Celestion Vintage 30 Guitar Speaker

Tech Tip: Wattage, Speaker Efficiency, and Amplifier "Loudness"

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When it comes to volume, wattage is only part of the equation

There seems to be some confusion when it comes to how "loud" an amplifier can get. When it comes to "volume," many musicians only consider the amplifier's power or wattage rating, and in general, more watts does mean "louder." But while wattage is an important consideration, the efficiency of the speaker(s) that are connected to the amplifier are also an important factor in the loudness equation.

Decibels and levels

Decibels (abbreviated "dB") are a logarithmic unit of measurement that pertain to a ratio between two numbers. Okay, I can see eyes rolling and glazing over, so I'll simplify things, and attempt to keep the "math" to an absolute minimum. With a logarithmic scale, you can't just add numbers in the usual way—a doubled number isn't "twice as much," but rather, many times more. For example, 100dB is many times greater than 50dB, not just "twice as much." When it comes to "loudness," which is measured in Sound Pressure Level, (or SPL), a 10dB increase in level is roughly equivalent to a "doubling" of perceived loudness. In other words, if one amp is generating 90dB SPL and another amp is hitting 100dB SPL, the second amp will generally be perceived to sound about twice as "loud" to the typical listener.

Wattage, power, and SPL

So how many watts does it take to get twice as loud? Let's imagine two amps—one 10 watts, and a second 20 watts. The 20-watt amp is double the power of the 10-watt amp, but doubling the power only translates to an increase of 3dB SPL. Remember, in order to sound "twice as loud," you need an increase of 10dB, so while a 20W amplifier will sound noticeably louder than a 10W amp, it will not sound twice as loud. The same thing holds true at higher wattages—a 100W amp is not going to sound twice as loud as a 50W amp; assuming identical speakers, it will only be 3dB louder, which is noticeable, but definitely not a doubling of perceived loudness.

Speaker sensitivity ratings

Speakers have specifications in terms of their sensitivity and efficiency— their ability to convert the incoming electrical energy into acoustical energy. Dynamic, moving coil speakers (the type found in most guitar and bass amps) are notoriously inefficient, and most of the incoming power is actual-ly converted into heat, not sound. Normally, speaker sensitivity is measured in an anechoic chamber (non-reflective, soundproof room) and expressed something like this: 90dB @ 1W/1m.

Translated into English, that means "90 decibels (SPL) with one watt of power, and measured at a distance of one meter from the speaker." A more efficient speaker will have a higher number, and a less efficient speaker will have a lower number.

Putting it all together

So let's assume we have a speaker with a sensitivity of 90dB @ 1W/1m and a power handling capacity of up to 100W. If we power that speaker with 1W of power, it will generate 90dB when measured at a distance of 1 meter. If we double that power to 2W, the SPL measurement will increase to 93dB. If we increase the power to 10W, then the SPL measurement will increase to 100dB, which is "twice the perceived loudness" when compared to 1W. So it actually takes 10 times more power to give us a perceived doubling of volume level. Since this imaginary speaker is rated to safely handle up to 100W, we could double that volume level yet again, and in theory, hit up to 110dB SPL by increasing the power all the way up to 100W. One watt=90dB. One hundred watts, or 100X more power=110dB. That's a huge increase in power but only a "doubled double" (4X) increase in terms of perceived volume levels!

As you can see, it takes considerable increases in power—in the wattage of the amplifier—to "double" the perceived "volume." This is where speaker sensitivity/efficiency comes into the equation. If we replace that 90dB @ 1W/1m speaker with a model that has a sensitivity of 100dB @ 1W/1m, the numbers change dramatically. For starters, 1W of input power will give us 100dB SPL. Remember, the first speaker required 10W to achieve that same volume level! So by installing a more efficient speaker, we can get the same perceived volume level from a 1W amp as we could from a 10W amp that is coupled to a less efficient speaker. Again, this applies all the way up to the maximum power handling capacity of the speaker. Assuming our 100dB @ 1W/1m speaker can also handle up to 100W, it can give us up to 120dB SPL; again, that's double the perceived "volume level" of the 90dB @ 1W/1m 100W speaker's maximum level of 110dB SPL.

Tags: Amplifiers Speakers


# Kyle 2015-11-23 06:51
I've been considering pairing some Bowers and Wilkins 685 s2's that are rated up to 100W with a sensitivity of 87db with a Peachtree Nova 125se integrated amplifier rated at 65wpc rms per channel at 8ohms. Will this amp be sufficient for a smaller room measuring about 12'x12'?
# annu 2015-11-21 23:22
can i use 300 watts 2 speakers in my 2500 dp amplifer
why sound is not clear
# Fahad 2015-10-27 07:53
Hi..my car entertainment system gives an output of 25 watts x 4...i am not very keen on adding an amplifier...wan t to pimp it up just by using good speakers...i plan to install Polk Audio DB651 coaxial speakers with a power rating of 60w RMS and 180w peak and sensitivity of 93db...i would be installing these speakers on all 4 outputs...i am not a bass buff and not crazy about thumping cars...but i do enjoy a decent amount of bass like the drums in Soft Rock music....

Will this combination in any way effect the speakers or the car entertainment system in any way as the wattage of the entertainment system and the speakers is different...?
# Bob Dole 2015-10-27 13:39
Good speakers will only get you so far. Car audio is NOT regulated like home audio is, meaning the only way you can hope for accurate wattage is if they voluntarily join. With that said, 25w x 4 isn't real unless it's a CEA 2006. Even then, it'll be a class D which is like flat pop compared to carbonated pop being class A/B. Adding an amp won't turn door speakers into a bass machine, so stop that mentality right now. Most aftermarket head units have filters. For 6" and under door speakers, go with a 100 hz and above. Adding an external amp that's high quality will reveal better sound than the HU could ever wish for. I use West End Girls (Pet Shop Boys) as a test track to gauge how good an amp is doing. They have a simple "tick"...."tock " (that loops) that seems to be similar to different clap sound effects from a synth. You'd be amazed at how many amps are so muddy that sounds almost the same and difficult to distinguish between them. Figure speakers can handle 50w RMS, so 200w amp.
# Bob Dole 2015-10-27 13:54
That's a 200w amp to power the 4 door speakers. I suggest running in true stereo vs. 4-way fader. If speakers are 4 ohm each, either run them 2 ohm per side or get a healthy 4 ohm amp. 2 ohm introduces poorer quality and heat. Can't really series them due to having a crossover built-in to each speaker. Can also run 2 smaller amps. I'd suggest one amp per side L/R as you won't have cross-talk issues between the channels being added from the amp. If you have the $$$, go with Zapco amplifiers. They are some of the best sounding full-range/twee ter amps. And while 200w sounds like a lot, each speaker will only see a 1/4 of that, but at normal listening you'll have a better sound with more accuracy, similar to a decent home stereo. With external amps, you'll find you can turn treble (10khz) to -5 values and not be overbearing. You'll also learn about amps "coloring" the signal if you try cheaper brands. All sound different so experiment.
# Trey 2015-10-16 13:28
So I was wondering how this works. I bought a pair of 15" sub-woofers for my car. Currently I have them hooked up to my little Sony Mini Hi-fi system. The speakers themselves work, however when i turn the master volume up past 15 (30max), the cooling fan turns on and goes nuts. But I hook up my stock speakers to it and the fan doesn't come on until it is at 24 volume. Why would it do this? Also one of the 15" speakers seems to be "Popping" for some reason, does that mean it is junk or can i fix that. It isn't as loud as it once was. Help Please!?!
# Bob Dole 2015-10-16 14:43
What subs are you running? How did you wire them? Where you turning the bass all the way up with bass boosters max? Fans kick on when amp heats up. The lower the ohm load, the hotter the amp will run = more fan time. I'm betting the subs are low wattage (50 to 100w) at 8ohm and the Sony system (4 to 6 ohm) was set to max bass with bass boosters on and/or you actually were "clipping the amp". Google "amp clipping" and look at the sites that explain it with a messed up sine wave that has it's peaks cut off. Clipping can ruin speakers regardless of wattage, though really beefy subs can sometimes tolerate it better. Upgrade to better amp (go old school to save $$$ and have better bass + sound quality) and run Alpine R's or older JL Audio for home gear.
# Trey 2015-10-16 16:36
Thank you for answering my question, here is some info. The subs are Kicker CVRs, they are supposed to be safe at 1000w and have a peak at 2000w. The wire is connected to the speakers through a connection already on the box, the one where you push the it down and then the wire goes in the hole. the sony stereo is not a new one, so it doesn't have a bass boost. Also, does the amount of power coming in from the outlet (120V) have anything to do with the speaker acting funny, is it to much power? The wire i honestly don't know what gauge it is, i don't have a tool to measure it. I also believe the ohms for the subs are supposed to be 4 maybe, otherwise it is 2.
# Sander 2015-10-06 13:02
Thanks for the extensive explanation! Now I can finally figure out what it takes to blow my speakers :)

Or not. I'm actually trying to prove someone wrong by saying things I learned here. They said 200W for a sub is enough if your amp is 200W and that you'd get 200W power/ Sensitivity indeed plays a good role. My speakers are waay too sensitive. I get really loud sound and crystal clear indeed, with just two and a half watts driving the speakers. Keeping in mind it's 3way.
# Madit 2015-09-29 19:05
Can I use my 705 watts amplifier in my 300 watts speaker? Thank you,
# Bob Dole 2015-09-29 19:56
Talking car or home amp? With car amp stuff, you do NOT want to have a bigger amp powering speakers with less RMS rating than the amp. Some subs can tolerate 100w more than rated but it's risky and shortens life. A way around this is wire speakers into an 8 ohm load, and/or add more speakers to split the amp's wattage. Home stereo CAN power less powerful speakers, but you MUST be VERY careful with the tone settings and master volume as it's extremely easy to pop the tweeters and overheat voice coils seizing the rest. Again, increasing the ohms to a higher load from 8 to 16 ohm is typically safe and most amps can happily tolerate it and will sound better doing so. Amps that state "high-current" should NOT be run higher than they are rated for as they are often purpose-built to run 2 ohm or less bridged and 1 ohm to 0.5 ohm stereo. I run my AB 9620b 4 ohm x 2 = 1500wrms x 2 to about 400w worth of speakers. The trick? Keeping master volume low enough and avoiding loud volume spikes.
# Bob Dole 2015-09-29 20:05
Also, if you are running a 7.1 home stereo, that 705w is split to each channel. What I referenced above is an actual 1 or 2 channel amp or a 2 channel amp bridged mono to produce a full rms wattage to the speaker. With a 7 channel (or even 5.1, 5 channel) each channel would only be putting out 100 watts, and even then almost all of them neuter the power in the lower freq. range to keep costs low and components small as they expect you to wire a powered sub into that .1 sub channel, which allows the plate amp to give the effect of a more powerful system. Older (like mid/late 1970's) solid state amps for example would do rated RMS wattage regardless of frequency and often did more than rated with robust dynamic ranges i.e. 50 wrms could hit 65w on peaks. Depends how awesome the amp actually was. If you listen to a 35 wpc 1970's Marantz or even Pioneer, it'll often walk all over these modern 5.1 or 7.1 units despite double the rated numbers. Why they are so popular now is SQ trumps.
# Rupesh 2015-09-09 13:39
I got an amp 50 watt x4 signal to noise ratio at 105db that 0.04 and channel separation 60db frequency response +1db 15hz -30khz lpf frequency 50-250hz how much watt speakers I have to used
# Rupesh 2015-09-24 13:21
I got a rockwood amp 4x50watt can I used a 200 watt speakers from a channel
# Rupesh 2015-11-14 23:36
I want to know how much watt speaker I haven't to used
# Bob Dole 2015-09-11 19:04
If you are using all 4 channels, you can run pretty much any speaker in a 2-way, 3-way, 4-way configuration, etc. 2-way being a woofer and a tweeter per speaker box. If running a woofer + tweeter PER channel, they'd need to be a minimum 25 watts each or 50 watts RMS or greater. If you go below that, like say really cheap 15 watt tweeters they'll pop even with capacitors cutting their frequency. I always recommend having tweeters that can handle 2-3 times the RMS rating to play it safe. I've seen 50 watt bookshelves loose a tweeter from a sudden volume slip on 65 watt amplifiers. Remember, each speaker you add splits the wattage from the amp. So 3 speakers (woofer, midrange, tweeter) per channel on a 50 wpc amp will see 16.66 watts PER speaker. While that may not sound like a lot, I have a 33 wpc late 70's 2-channel stereo amp that can push a 4-way setup to 120 db JUST playing a bass sine wave at 32 hz. That's a 15" paper woofer with ribbon surround, a horn mid, and 2 piezo tweeters.
# Bob Dole 2015-09-11 19:13
And just be clear here, that's 33 watts RMS divided by 4 speakers. That 120 db rating was 2' away from one woofer. SPL of the speaker is VERY important with lower wattages as the speakers will get LOUDER with less wattage. Also, I was running with the loudness switch ON and bass at +6. Loudness on this particular amplifier seems to be active (vs. passive) and makes a huge difference. If your amp is older (I'm guessing it's a late 70's Quad amp?) it should do rated RMS at all frequencies and have a wider dynamic range i.e. it's rated at 50 WPC but can probably do 60 watts in peaks, making it sound louder and more vibrant. Newer amps shoot for rated RMS at 1000 hz (and above) but might do significantly LESS at lower frequencies AND they stay closer to the RMS rating, and limiting the bass area altogether. This allows the units to be made cheaper with weaker power supplies. This is rampant with 5.1, 7.1, etc. units as they figure you'll run a powered sub to cover what the amp can't.
# Justin 2015-09-07 21:55
Hi there I have Polk audio RTI A9 rated at up to 500w sensitivity rating of 90DB Frequency Response18 Hz - 27 kHz RUNNING on Marantz SR 7007 is this the right power for the rating of my speakers the receiver is 7.2 I'm only running 5.1 I believe it is 110wpc
# Bob Dole 2015-09-08 12:50
Those Polk have a 50 to 500w recommendation. It might get "loud" enough for you, then again it might not. That 500w rating comes from the fact there are 6 speakers in that cab, meaning each speaker *can* handle 83.33 watts RMS (500 divided by 6) each. With your 110 wpc source. 18.33 watts is going to each speaker. If it's not loud enough, maybe try 250 wpc. That'd put each speaker at roughly 41 watts each, which is plenty safe for them. You can always bi-amp your system. Run the Marantz for the rear, center, and sub signal, then go old school Marantz 2385 ($$$$) or any decent monster receiver from the late 70's and run that stereo. It'll most likely sound 100x better plus give better stereo separation. If you have the cash, look up AB amps dot net. They aren't cheap, but Bob builds custom to order and they are very powerful. I'm running a late 90's AB 9620b. I refurbed with newer electrolytic caps, metalized film caps, etc. and it's an excellent amplifier.
# Ramnik 2015-08-07 11:44
I have cadence anina stereo speakers 8 ohms 150 watts rms . I been told to buy nad amplifier of 80 watts. Is it the right choice ?
Am a novice in this field.

Thanks in advance for a reply
# Bob Dole 2015-08-07 13:20
NAD are typically "liked" and collected. Will "you" like it? Only you can answer that. Typically speaking, amps in general can sound great, sound like garbage, be too colorful, too bright, too dull, lousy stereo imaging, unable to accurately reproduce highs and bass, are muddy, etc. etc. Wattage has ZERO effect on sound quality. It's just a limiting factor to help avoid damaging speakers and to also give a rough guideline on how loud it can theoretically get. Buy the NAD and set it up. I suggest playing everything you typically listen to, and pay close attention to detail (headphones can help expose more) If you all of a sudden "hear" new sounds like more detailed guitar plucking, a sax that's knocking you over, etc. That's the best way to judge. If it sounds like an utter mess, you all of a sudden can't "hear" things clearly anymore like subtle change ups, etc. then sell it or perhaps try different speakers first.
# Matt 2015-07-18 20:26
Say I have a 15 watt amplifier. How much "louder" will a 100 watt be?
# Bob Dole 2015-08-07 13:35
Really depends on the speaker's SPL rating. If the speaker has an 83 db SPL, 100w won't sound "that" much louder as the speaker needs a higher wattage than that to get significantly loud. Is the speaker is 91db SPL, going from 15w to 100w will make a more noticeable difference. EX: One of my home amps from the late 70's is rated at 33wpc. I have 2 4-way cabs with 15" drivers (rated to 150 wrms). I can hit around 120 db w/o clipping the amp at 100hz. My larger amp can do 855 wrms PER channel 8ohm & can push the same speaker to nearly 130db (100hz) before speaker is at limit (guessing it's overdriving the woofer by at least 100w at that point). If the speaker was 83db, it wouldn't even come close to that db on handheld meter. A +3db increase is about what you get from adding an extra, identical speaker. Just something to think about.
# William 2015-07-21 02:53
A little less than twice as loud. The 100 watt would be about 84% louder.
# Vijay 2015-06-30 05:22
I want to choose Sony SRS D9 2.1 speakers. 60W (30W sub woofer and 16X2 speaker). S'N Ration is 85db. Another compared model is Samsung HW-H20. 60 watts but s/N ratio is 65db. Sony is magnetically shielded. Which one should I choose?. Sony is double the cost of Samsung
# Bob Dole 2015-06-30 07:37
Choose the one you want that sounds best. Unless someone has BOTH sound bars and your exact listening tastes, set up, room characteristics , and can use descriptive lingo exactly to your understanding, no one can answer this for you. It'd be like me asking you to choose between indigo blue or midnight blue for the color of carpeting in my living room which you've never seen and don't know if like short of long loop under my toes. Shielding doesn't really matter anymore unless you have ultra sensitive magnetic devices. CRT monitors/TVs would be a concern as a 12" woofer too close will interfere with the color. LCD isn't an issue. Standard PC hard drives seem to be shielded as I have 15" woofer within 6" of 2 HD and it doesn't effect them. Though I imagine a strong magnet right on the HD case could be problematic. S/N ratio is a fairly significant difference. Google S/N Ratio to get a clearer picture on what will suit your needs better. Sound bars aren't that great, so don't expect much.
# Ajay Govind 2015-06-25 15:19
I am confused in buying between 2 2.1 Sound bars
Phillips HTL 3140B specs speaker with 60W (30W x 2) at 8 ohms + 2 Tweeter at 6 ohms + Sub 140W all 3 ohms with input sensitivity of Aux as 900mV and Audio In as 500mV and S?N ratio 65dB


Samsung HW-F450 specs Speakers 160W (80W x 2) + Sub 140W all at 4 ohms with input sensitivity 570mV S/N ratio 70dB

My Question is
Is Phillips better than Samsung since it has 8 ohms impedance and lesser output wattage than compared to Samsung with higher wattage but at 4 ohms impedance?

Price-wise both are same rate. Which one should I buy which will give me better sound?
# Bob Dole 2015-06-26 07:40
I'm not familiar with sound bars as I run actual amplifiers to standing speakers. But looking at the specs of each unit, I'd lean towards the Samsung as it has a 6" sub vs. Phillips 5.25" sub which is too small. 5.25" is about the size of a typical car door speaker. 6" is a little bigger, though don't expect to rattle windows, but in a small room it should suffice. These are singular subs by the way. Their ohms don't matter as they apparently have their own amp. Samsung also has a higher S/N Ratio, and 4 HDMI inputs. Phillips is typically below Samsung in the pecking order. Also noticed the Samsung has an average of 4 stars in most ratings. I suggest looking online at these ratings to see what made people gripe. If you are buying at a store, see if you can demo them and play with whatever settings they have. Granted, a large open store with tile or concrete floors isn't the best testing grounds to simulate a small room with carpeting and furniture, it should give you an idea.
# Phil R 2015-06-23 18:29
I have a Twin Reverb with 85 watts of tube power. Currently I house 2 Celestion Vintage 30's at 60watts each, 8ohm. I am looking to swap one of those speakers out for something else. What wattage window should I stay in so that they both blend well? And I must get one at 8 ohm to match the current speaker, yes?
# Bob Dole 2015-06-24 10:49
Wattage doesn't matter with regard to sound. Wattage given to speakers is so they aren't stuck on an overly powerful amp and seized after 10 minutes of bass notes or tweeters popping from being over driven. If you mix speakers in a mono setting, it won't matter much. I find differing speakers can compliment the overall sound. EX: I run an Alpine R 10" (round) and Kicker L5 12" (square) both in similarly ported boxes, both getting roughly 225w each from same amp mono, so they get the same freq. cut. It's a good bass sound that covers better "bass" a 10" provides along with the more air a 12" pushes. Listening to rock or whatever you'd never know 2 different sizes were being run. In a stereo configuration at lower volumes, it's hard to tell, but put some distance between them and sit in the sweet spot with more volume and you'll hear a difference. With that said, they both have very similar SPL. Testing with a DB meter, they put out the same. So try and choose a similar SPL with 100w+
# Phil R 2015-06-24 12:58
Thank you! Do you have a good recommendation of a speaker to pair with the V30 to really beef up my sound?
# Rory K 2015-06-28 03:35
I think in a parallel configuration, the power will be distributed evenly i.e 40 watts to each speaker, so make sure your new one can handle 40 watts. Speaker sensitivity is also a big factor. V30's are rated at 100db and are quite loud. Vintage style Jensens that you might find in many Twins might be as low as 96db. It doesn't sound a lot, but consider that a doubling of wattage is equivalent to 3db! If if were me, I'd be looking for a speaker that had different tonal qualities to get the beef you're looking for. Being a Twin, i'd go for something that was going to provide a Fendery mid range scoop, rated at at-least 40 watts with high sensitivity - I'd recommend Eminence as a starting point. Note, Twins normally sound thin at low volumes (i used to own one), you might be better off with a less powerful amp :-)
# Rory K 2015-06-28 03:59
And yes, you'd be advised to use an 8 ohm speaker
# Bob Dole 2015-06-25 08:41
I don't unfortunately. Really boils down to personal preference and intended usage. Running from same amp, just try and match SPL and ohms to existing speaker and make sure it can physically cover your intended freq. range. Can upgrade film/electrolyt ic caps in audio path to improve sound too. If you end up with say 50w polypropylene 12" (85/2 = 42.5w min.) with foam surround and have it only playing lower to low/mid freq with a voice choke, shoot for a couple db higher SPL as it'll sound a tad quieter & smoother vs. a paper woofer due to the way it's constructed. If you don't mind a physical difference, and 2 speakers of differing composition can fill in some holes with the audio signal. But again, it's purely your ears that matter. Ex: I run paper composition 15" woofers in main home stereo fronts. When time comes to add a dedicated sub channel, it'll get synthetic composition woofer(s). 15" paper will focus on higher range and polys will cover lower. Just experiment for best sound!
# arvin 2015-06-23 20:30
sorry sir, the speaker has a sentimental value its my dads gift.... but thank you....
# arvin 2015-06-23 04:29
sir can i ask a question?. i have amps that that has a 11 channel and 130 watts per channel, can i use 2 pcs of 300 watts speaker?
# Bob Dole 2015-06-23 05:57
Can you clarify what you are talking about? Are you saying you have 2 speakers per channel? Or you have 2 speakers and want to only use 2 channels?
For the record, speaker wattage is what they are supposed to safely handle. Better speakers underrate this figure by as much 25%. Higher-end subs fall into this category where it might be rated at 400w but can safely handle 500w. That's the max it can handle. If it has a decent SPL rating, like say 91db, then running off a 100w amp should still get it loud enough. If it has a 83db SPL, then 100w won't be enough to get it very loud. Will probably find you need to crank the volume pot nearly all the way to get loud. This is because they designed the speaker with a lot of wattage in mind and opted for a low SPL design. You can put a 1000w rated speaker on a 130w amp channel, it doesn't matter. But if it has a really low SPL, you'll need more wattage to get it louder.
# arvin 2015-06-23 20:20
thanks, it is 2 separate speaker, i just test it in my amps and my amps starts to gain heat after a few hours it is very hot i just can't touch it. and i need to to maximize my amps vol. to get the speaker sounds better.. i think i need to replace my one of them....
# Bob Dole 2015-06-24 11:11
Heat is normal. People think their air cooled amp is supposed to run ice cold. It won't. Fan-forced amps run cool providing they move enough air, thermal paste hasn't dried out, unit isn't covered in heavy dust, etc. Driving lower ohm WILL create more heat. I suggest buying an inexpensive volt/ohm meter. Set it to ohms. Connect (+) to speaker (+), and neg (-) speaker (-) of each speaker and see where they actually are. Some speakers might state "8 ohm" on the magnet plate but are actually 6 to 7 ohm. Heavily worn speakers can drift over time from usage too. If your amp is very sensitive to ohms, has just barely adequate cooling, etc. it could be enough to drive temps hot like that. You can try running the speakers in series (connect (+) of speaker "A" to (-) of speaker "B"; this leaves you with (-) on "A" and (+) on "B"; run ONE channel's (+) to "B" and (-) to "A". This will put 65w to each speaker in a mono load. Play for 30 minutes. Does it get hot now?
# arvin 2015-06-24 17:30
thank you sir Bob Dole. your right sir, i try it and its 4 ohms each .. i'll just now connect them in series..
# Kip 2015-06-11 11:37
I hope you can help me out.

Wanting a classic radio look, I installed a RetroSound Model Two radio in my 1970 Chevelle SS. Output power is shown to be 25X4w RMS 45X4 Max Power. 4ohm.

2 Kenwood KFC-X173 speakers. 4 ohm.87db.Power range of 2-80 W RMS (240 watts peak power) Rated input power: 80 W. 2 Kenwood KFC-X 693 speakers. 4 ohm. 89 db. 2-130 W. Peak power 300W.

It is not very loud, and I would like more volume.

What is max amplifier wattage I can install, and what increase in db (and volume) would result? Is it worth it? Or, being long in the tooth, should I just invest in a pair of hearing aids?

Thanks for any help you can give me.
# Bob Dole 2015-06-12 02:09
If it were me, I'd either buy a 4 channel amp with separate gain control i.e. a front/rear gain control, Or buy 2 smaller amplifiers, which might be easier to hide, though be sure to use a heavy gauge wire for 12v+ and ground (follow the amplifier's specs for wires, and double it to power 2 separate amps off same ground and power). I had a ground wire burn up once while driving and it melted carpet and almost a fire. So use proper wires. 80w x 2 = 160, so 150-200w would be OK there. Keep gain low to prevent clipping and avoid unwanted noise. 130w x 2 =260w, so 200 to 250 would be OK. Since they are 89db, they'll get LOUDER easier, so a 300w to 320w 4 channel would work too. Turn gain to 0, turn head unit to a normal level, then increase gain for fronts until they are near a decent level. Then adjust "rear" gain so they match the fronts or just a tad louder so you can hear all 4 equally. If amps come with freq. cuts, set fronts to the range they play and higher, same with rear.
# Sean 2015-06-10 08:24
very interesting read

I am looking at making a 2x12 guitar cabinet for my 50 watt combo amp. Would it be to safe to use 2 30 watt speakers? I understand about matching the ohms but not the wattage. With so many options out there I want to make sure I buy the right thing

# Bob Dole 2015-06-10 10:15
Yes, it's safe. If you are running 1 speaker, then the wattage should be around what the amp puts out, OR you have to be really careful NOT to overdrive the speaker i.e. have to keep volume well under clipping, OR lower the input sensitivity so the amp never gets near rated wattage (I'm running an 850w x 2 AB9620b amp with 150w cabs on both channels, but input sensitivity is low enough I can turn volume 60% and they aren't even clipping; my pre-out voltage is low enough that the amp isn't getting near rated). IF you are running 2 speakers, then they share the wattage evenly (basically amp "sees" one load). In your case, your 50w amp will get divided into 2, so each speaker will see 25 watts. If they are 8 ohm speakers and amp is 8 ohm, you can wire them series for 16 ohm, but amp will be around 25-30w total, so you'd be lucky to see 14 watt at each speaker. If speakers are 8 ohm and amp can tolerate 4 ohm, wire them parallel so amp sees 4 ohm. If it does 50w 8 ohm, might do 65-70w @ 4.
# Sean 2015-06-11 05:08
Thanks for your reply

Had a look last night and my amp has 8ohms & 16ohms options.

The speakers are both 8ohms so was thinking of wiring them up in series to make them 16ohms.

Would that also work if i was to use 2 types of speakers that are not the same wattage? i.e. have 1 speaker at 30 watt and the other at 25 watts?

# Bob Dole 2015-06-12 01:57
Speaker "wattage" is just a rough guideline so you can match it to an appropriate amplifier. You'll be fine. Most 3-way speaker boxes for example, might have a 50 watt woofer, 30w tweeter, and 40w mid. Since they share the wattage, 90w is about the most you'd want to feed it 90/3 = 30, though it's not exact as bigger amps with a lot of dynamic range could peak higher.
# Brandon 2015-05-26 20:54
I got two ALTEC 15" speakers and a 1700 watt amp, would the speakers able to handle 1700 watts without blowing?
# Bob Dole 2015-05-27 02:36
You need to list more information like which Altec speakers those actually are with specs, along with the amp you are using, along with what you are trying to do, and if we are talking 1700w @ 8, 4, or 2 ohm mono or 2 channel setup i.e 1700w/2 = 850w x 2. Also need to know the ohm rating of the speakers. Rule of thumb is try and not exceed the woofer's RATED wattage. Ignore the "peak", "max", or "total" wattage of the speaker as that's usually reserved for it can either handle in short bursts or what'll cook it immediately depending how well it's built. High-end car subs can sometimes tolerate 100-200 watts more than rated, and even sound slightly better, but the heat will kill them eventually, especially in sealed enclosures with no fresh air vs. a ported box that's constantly moving air. With high power home amps; say 1700w @ 8 you can run the series for 16 ohm for 850w, which would get divided into 2 speakers for 425w each and actually sound better with less heat.
# Sauhard 2015-07-13 05:04
I cannot figure out a confusion ... I want to find a appropriate combination of amplifier and a woofer for my project , which should make an use of 12v battery. Plz Tell me the easiest and lightest stuff

P. S : I am making the whole car audio system kinda portable
# nestor 2015-05-16 20:42
sir i have a 10watt bass amps and i want to turn this to more or less 200watt bass amps so that i can use it in bigger venue. i want to make use of what can still be used in this small amps to save maney. what shall i do?
# Bob Dole 2015-05-16 21:27
You can't just take a 10w amp and turn it into 200w. A die hard DIY'r *could* study it's circuitry, and build a custom amp based around yours with more outputs, etc. then through laborious testing, get it's "sound" dialed in. This is out of my realm and if you are asking, way out of your realm. I suggest you find a 200w bass amp used and have a recap done if old, including updating the film caps. Avoid film caps like metalized polypropylene as they'll removed distorted audio i.e. they clean up the sound to be more precise, which might be undesirable in this type of amp so stick with same type it has already. You could get speakers with around 97-100 db SPL, and get away with less wattage. I have 15" 95 SPL paper woofers on a solid state 33 wpc home stereo amp. Using a db meter, I'm hitting 117db around 35 hz. At 15 hz, due to amp roll-off, it's doing around 97 db. If you are in a large room, I'd shoot for 125db or more (per speaker) which is easier to hit with higher SPL speakers.
# Bob Dole 2015-05-16 21:35
That 117db rating is per speaker. Each identical speaker you add (assuming it's NOT halving the wattage i.e. a mono amp going from a single 8 ohm load bridged to 16 ohm bridged; 8 ohm to 4 ohm doesn't always double the wattage, have to look at specs) running from identical amp should add +3 db, so in my case 117 from one speaker should be 120 db from two of them seeing the 33 wpc each. My car subs are 10" Alpine R and Kicker 12" L5. Both are run from same amp @ 225w each. Measuring both separately, I'm seeing around 125 db (or more) on average and combined they are at least 128 db which is where my meter stops registering. But again, that's 225 watt per speaker, and they don't have the higher SPL my home woofers have. Food for thought.
# emmo 2015-05-06 22:36
I need to power a pair of yamaha ns10s for studio monitoring, thus, I need quiet power amps. I heard the ns10s cones are hungry suckers (the specs say 60w, 120w max.). I was looking to a crown els 1000 (220x per channel) or a mar ants ma500 (125w per channel). should I worry with too much power from the crowns melting the ns10s, or too few power from the marantz? I don't intend to play them too loud and I have a refrigerated studio (I read the els 1000 fan doesn't even start if you are not driving them hard). thanks in advance for you precious help !
# Bob Dole 2015-05-07 00:35
How are you going to wire the NS10's? They are 8 ohm each, so you need a 4 ohm amp mono, stereo or dual 8ohm, or an amp that'll do 16 ohm if mono, but running series with speakers that have their own crossovers might cut freq. wrong. If doing mono 16ohm, you might need to wire them off one crossover. That Crown is a Class D amp. I personally abhor Class D amps as they just aren't musical enough but are getting "popular" and advertised as "green" as they drive higher loads easily. ONLY thing they are good for is high wattage car audio when you want 1kw or more from a single amp and aren't willing to run multiple Class A/B amps and mult. alternators. The Marantz is 125 w @ 8 ohm and I believe an A/B amp. It should sound better than a modern D amp and it's SNR is 116 which is high (good). As long as your pre-amp provides sufficient pre-volts, it should be a good match musically if 16 ohms mono. Amp will run cooler and easier at 16 ohm than 4 ohm.
# Bob Dole 2015-05-07 00:41
Try running in series @16 ohm with the Marantz. You'll loose a little wattage, but with a 116 SNR and 90 db off the speakers, it should still sound loud and hit high SPL numbers. If it sounds like it's lacking bass, then use one crossover to and treat each speaker as a pair. i.e. one crossover would filter both woofers as 1 and highs as 1, check final ohm with ohmmeter to see where it's at. Otherwise, go with a different amp that can handle dual 8 ohm loads i.e. stereo amp or purchase 2 smaller mono amplifiers @ 8 ohm. Stick with Class AB if you want to hear musicality.
# #low 2015-04-29 13:43
I bought a Lazarus car amplifier, bass box,and speaker package. HTG447 2000watt 4 channel MOSFET amplifier, VCHB310 vector 3000 watts triple 10" slim designed bass box enclosure VX6C VX 6.5 two-way custom component system VX630 VX 6.5 three way speaker, LQ19CAP Contaq 1.9 farad 12 volt power capacitor , AMPKIT4 contaq 1800 watt 4 gauge power amp kit. Was this a good buy? Will that aamplifier be enough for all of that? I have a 320 amplifier will that help any? This is my first system
# Bob Dole 2015-04-29 15:35
A "good buy" is entirely subjective and boils down to whether you like it's sound or not. I will however say all those high watt numbers are NOT RMS watts. Car audio isn't governed under the same federal laws home audio is (which I still find amazing as it's straight-up misrepresenting but I'm sure their lawyer would question how long it needs to make that watt to be considered a watt, or maybe they switch to an unregulated power supply and jack the voltage up to 36v for 2 seconds and say "see, it made 4kw)- it's deceptive advertising. Although not full-proof, you can usually ballpark an amp's wattage by it's fuse ratings. I think 75w for each 10 amp's worth of fuse is a safe guess, though higher-end amps like a Crossfire VR602 I used to own did 605w bridged @ 4ohm and had 60 amp fusing. Those speakers can't take that wattage either. Hook them up to a 3kw home amp and they'll smoke under 10 minutes of pushing.Probabl y closer to 200-300w each.
# Bob Dole 2015-04-29 15:44
I will say many more honorable brands have volunteered and adopted the CEA-2006 standards which is basically in-line with home stereo gear to a degree. They MUST report the actual true wattage (which an amp is supposed to be able to do for a full hour IIRC then they take the average number. This helps weed out amps that make more power briefly while cold then loose it as it gets hot) of the amplifier, but they still seem to want to print the "peak" wattage like it even matters. Old SS gear in the late 70's was "dynamic" and could quite easily double it's rated RMS wattage in peaks, which made it more dynamic sounding and even larger. This garbage about a 1kw amp with 50 amp of fuses peaking at 3kw is 100% rubbish. Look for the CEA 2006 logo on the next amp you buy. Stick with Alpine R's or even JL Audio W3 or better. Buy Class A/B amp as they have better sound quality than Class D (wattage doesn't matter, SPL does)
# bill pate 2015-04-23 13:31
can you hook 4 25 watt channels to 2 50 watt car speakers?
# Bob Dole 2015-04-23 14:43
Normally, NO. If you want 4 speakers for four channels, I suggest finding 2 more speakers. Online you can probably find matches. If speakers are DVC (dual voice coil) then yes, it's possible. A dual voice coil speaker is basically like having 2 speakers in one. They'll typically have dual terminals on opposite ends. I Best way to do it is either mono or run both left channels to one, both right to other, but again, this is for DVC ONLY. Do NOT bridge your channels unless it's capable. In your case, if you must run only 2 speakers, I suggest using front right and front left channels for a stereo experience. Some older head units were actually designed like that leaving the rear channels optional. Might loose some rear stereo effects though. 4ohm is typically car speaker, so be weary what you connect to as 8 ohm home stereo normally won't tolerate it and might trip protection and shut off. Should say ohm impedance on unit.
# clueless 2015-04-14 16:07
I've a QSC RMX2450 and wonder if it will a good mate for JBL PRX425 speakers. Can someone please give advice?
# clueless 2015-04-14 16:17
additional details -
RMX 2450 specs:
Continuous Power Output Wattage:
- 8 Ohms: 500 W
- 4 Ohms: 750 W
- 2 Ohms: 1200 W
- 8 Ohms Bridged Mono: 1500 W
- 4 Ohms Bridged Mono: 2400 W
- Current Consumption: 10 Amps

Frequency Range: 55 Hz - 19 kHz
- Frequency Response: 75 Hz - 16 kHz
- Coverage Pattern: 90 degree x 50 degree nominal
- System Sensitivity: 100 dB SPL (1w@1m)
- Power Rating, Pink Noise: 600 W / 1200 W / 2400 W (Continuous/Program/Peak)
- Rated Maximum SPL: 134 dB SPL peak
- Nominal Impedance: 4 ohms
# Bob Dole 2015-04-14 16:36
Those JBL (nice SPL btw) are 600w @ 4 ohms. The QSC is 750w @ 4 ohm. The 1200w "program" and 2400w "peak" seem way exaggerated. I'd be VERY cautious with the master pre-amp volume and avoid trying to floor them given their price. While I don't doubt the RMS (continuous) rating of the speakers, I wouldn't expect them to tolerate a doubling of that on regular basis let alone 4 times. At 4 ohm, the amp puts out 150w more RMS which is what would concern me. Keep volume reasonable and it should be OK. But accidentally have full 750w from the QSC hit them at once and I suspect you'll loose a tweeter or crossover cap, etc. The QSC is an OK amp. I run old AB amps which are similar to the RMX line. I try and up the ohms to avoid over powering my speakers while lessening the burden on the amp. With such a high SPL anyways, you don't need a ton of wattage to get them going. Consider adding polypropylene metal caps to the amp board to clean up it's sound if it's running green polyester caps ;)
# Devin 2015-04-13 10:28
My 4x12 cabinet has 4 12" 16
Ulm 30-watt speakers. Would it be acceptable to replace those with higher wattage speakers? If so what would be the outcome
# Bob Dole 2015-04-13 11:00
@Devin Speaker wattage is just a rating of what they are supposed to be able to handle safely before self-destructin g. You can put 100 watt speakers on a 15 watt amplifier, and suffer no issues. You need to watch the SPL of the speaker though as some companies will tout a high wattage, but it'll only have say an 83 db rating, meaning it'll need the higher wattage to hit the same db as a higher SPL speaker at far less wattage. Speaker wattage is more or less a safety feature so you can hopefully couple it to something that won't smoke it on the 1st bass note :) If you had a 500 wpc amp and tried powering a 50 watt woofer, it'd cook the poor thing, but without a rating you'd never know. Car audio is an exception as they aren't bound by law and often exaggerate, but speakers are typically accurately rated. Again, just make sure the speaker has a high SPL and matches the tonal qualities you are looking for and it'll be OK.
# Bob Dole 2015-04-13 11:12
Also, avoid pushing the speaker to the point of clipping, as that can still damage it. A woofer or rather an actual subwoofer that's typically over-built, can probably survive it, but a mid or tweeter might not tolerate it.

And sorry, to answer your question, higher wattage won't change anything. If you want to experiment with different sounds, look at paper, polypropylene, or other materials. I find paper makes for louder mids and somewhat louder full range, whereas polypropylene makes cleaner bass in the lower freq. range, especially when driving high wattage. Although I used to run some Radio Shack Realistic 50 watt polypropylene woofers in the early 90's and they made really good bass when matched to a capable amp. Most car audio subs are polypropylene or some other synthetic. Just experiment if you can afford it, or ask around about specific speakers on appropriate forums to narrow down your selection and go from there. Good luck.
# Bob Dole 2015-03-13 21:22
Also, keep in mind 30wpc to 100wpc is more than adequate (referring to vintage solid state gear from late 70's, 80's, high-end PA stuff, etc) for a house system or really small church, etc. Whereas 1000wpc to 2000wpc would be needed in large venues. If you want the best sound (to your ears), don't focus on wattage. Just use the wattage of the amp to ultimately dictate how loud the overall system can be, then match speakers that can handle it. I have an old late 70's MCS 3233 (a JCPenny house brand no less) in my collection that's rated at 33 wpc and peaks around 65 wpc. It'll walk all over a modern 100 wpc stereo in sound quality and even loudness. In my teens I even ran 2 12" woofers in a 3-way and it sounded amazing at full volume. In a small bedroom, you couldn't even hear someone talking and the bass was knocking the clock off the wall in another room and rattled plates, despite the fact the wattage was split across 6 speakers, and woofers were rated around 50w. Just experiment!
# Bob Dole 2015-03-13 21:05
"Double speaker watts vs. amp wattage", isn't always needed anymore and depends on the actual amp and what you are doing. Typically, you want the speaker wattage to at LEAST be what the amp puts out if running 1 speaker per amp. Most vintage SS amps from late 70's, 80's, HAD higher dynamic wattages, so a 33 wpc amp could easily hit 60 wpc peaks at full volume. Average modern home stereo amps aren't built as rugged, and stay closer to their rated RMS as sound quality is NOT a concern like it once was, hence old gear when taken care of sounds better. Remember, if your AMP is putting out 200 wpc x2 channels, and each channel has a 3-way speaker cab with say a horn, piezo, and woofer, that 200w is evenly split to each speaker. 200w/3 =66w seen per speaker. If each speaker is rated at 100w, you'd want a 300 wpc amp to get the most out of it, though less wattage can power it fine. Subs can sound better if overpowered slightly, but caution is needed. Aim for highest SPL and match watts.
# Bob Dole 2015-03-13 20:36
For those asking wattage questions, speaker questions, etc. here's my take. Tweeters, horns, mids, are typically higher SPL like 97dB @ 1W/1m to 100dB @ 1w/1m, whereas subs are often in the low to mid 80's, but typical woofers are in the low 90's. Paper cone speakers are typically louder sounding than polymer speakers, hence why many PA and guitar speakers are still made of that, but they seem to often introduce unwanted effects at very large volumes whereas polymer can stay more controlled and doesn't have that "ringing" effect. Subwoofers, with car audio subs typically being heavily over-built with over-sized magnets with pole venting, dual voice coils, and extremely rigid baskets handling anything from 100w up to a genuine 1000w+, seem to sacrifice SPL in favor of actual wattage, though some subs are 89 dB with high wattage, and those will sound "louder" than a 85 dB running from same amp. Running mult-amps, you can often get away with less watts for highs but need more for bass.
# John Alfieri 2015-02-09 07:08
Should have added this to last question. The QSC 153
claim 1000watts continuous and the DXR15 claims 700watts continuous if that helps
# John Alfieri 2015-02-09 06:50
I appreciate your advice. Here is our situation. I have a pair of QSC 153 3way speakers 134db {spl } We played in a larger hall the other night and felt we needed more power to cut through to the back. I purchased two DXR15 133 db{SPL} to connect to the QSCs. Leaving out any discussion about subs, how much louder will this set up be ? Will it be noticeably louder and have a longer throw ? Thanks
# cayde 2015-01-22 08:18
I was just wondering why a lot of times when it comes to guitar heads and speaker cabinets, that the speaker cab will say 200 or 300 watts @8 ohms, but the head that is displayed to go with that cab says 40 watts @ 8 ohms output. So the question is is why are most heads between 30 to 100 watts output, but the cabs go up to like 200, 300, 400 or even 500 watts handliong? I was allways under the impression that you can do damage to your system if the watts are not enough for your speakers. Thanx for any answers.
# Emmanuel 2014-12-16 15:37
Hi, I am searching for an amplifier that can really make a difference in terms of output and durability!
Can anyone who knows, advice on the wattage I need and the type of speakers than can harmoniously work with it without much of a headache? What I need is far from a home theater....this is for commercial purposes! Grateful for any help!!!
# Joe 2014-05-26 16:16
Good article however I have 2 120w amp heads Names unmentioned.Amp head a sounds great vol has to be turned up to at least 5 to really let loose. Amp head b sounds very good also but will blow your face out at 3. Same 4-12 cabinet here guys.
# Scott 2014-05-23 06:25
The Ah-Ha light did indeed go on.
# Cesar Cardenas c. 2014-05-23 00:19
Very good article, it really helped me to understand more, speakers and relation with power and sound level.

# Daddy D 2014-05-22 23:38
Well as far as guitar amps go, the more weight you can carry into the gig, means your guitar amp can be louder.

My biggest concern is clarity and a smooth response at all freqs I can generate. I guess my amp is loud enough and I don't have to buy a heavier one.
# duke 2014-05-22 19:42
Always ask your amp manufacturer what they found best during bench tests. If you are using a mass produced amp don't worry about it, use what it came with, a speaker won't fix a poor quality amp.
# matt 2014-05-22 18:42
A good rule I heard is. Ideally the watts of your speakers be twice the wattage of your amp. So with a 25 watt amp. Have 50 watts for your speakers. this way you get the best tone. And you are not underpowered so you won't blow your speakers.
# Ben 2014-05-22 19:40
Matt, if i have a 100W 2x12, would getting two 100W speakers be optimal? or two 200W ones? you said speaker capacity should be double the amp, but does the wattage split evenly between the speakers or no?
# M. Underwood 2014-05-22 17:23
Good article. Let's remember though, any amplifier has a peak efficiency, typically 50 to 60 percent of its rated power. If you want reliable service from your amp, keep this in mind. This will give your amp plenty of headroom but not over draw current through the circuits. Just FYI.
# grubbs 2014-05-22 17:21
This clears a lot of things up, thanks.
# XwpisONOMA 2014-05-15 11:32
Sorry, I tried, I could not understand anything of what you're saying. I came here trying to answer a simple question: If I have -say- a 1Watt amp what is the power rating of a speaker I should most efficiently connect it to ? Efficiently means the least amount of wattage producing a good, non-distorted sound. In other words is there a rule of thumb: So many watts from the amp require so many watts (min-max) capacity from speaker.
# pbhales 2014-08-18 13:29
Once again, there seems to be confusion about wattage and sensitivity and loudness. The power-handling capacity of a speaker is demarcated in watts-- a "100watt" speaker will handle the full-on signal from a 100watt amp without blowing. You use that spec when you're trying to mate a speaker to an amp so you don't promptly ruin your investment. Why, then, do speaker companies make guitar speakers with different wattages rather than just one high-wattage speaker? Because many people want the sound of "soft breakup" that comes with pushing a speaker at something close to its max. If you're looking to get max perceived loudness out of a rig, you go for the highest-sensiti vity speakers around-- typically topping out at 102-103 db. That makes for a substantially louder rig than the same head run through a typical lower-efficienc y speaker, say with a 95 db. sensitivity.
# Batelec II 2014-05-08 03:18
Wow..interestin g!
# Bobb Woods 2014-03-29 11:06
This is where the "Ah-HA!!" light goes on... very informative.

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