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Q. Will an Amplifier Provide More Boost to My 7.1 Surround Sound Setup?
March 16, 2009 | by Bryant Moore
Bryant Moore explains how to add an amplifier to this 7.1 surround sound set-up.
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Posted by Tom  on  03/16  at  04:47 PM

Sorry but i disagree. Unless you are running all 7 speakers at full bandwith then a seperate amp would make sense.

But 99% people have a dedicated sub and run all speakers as “small” and any mid-upper level receiver will have plenty of spare power to run sattelites.

People dont realize how loud 30 watts really is, and very rarely does an amp really require its full power.

If you got money to burn then get a nice seperate amplifier. I recommend EMOTIVA or OUTLAW.


Posted by Paul  on  03/16  at  11:59 PM

@Tom, sorry Tom, I think you’re really oversimplifying wattage and volume.  There is a lot more to the problem than perhaps you’ve thought of.

You need to factor in a lot more variables.  If we say a ‘typical’ speaker is 87dB efficient @ 1 watt 1 meter, here’s a really simplistic version of how the math goes (and even this long winded summary ignores a TON of important factors and variables):

Part I:  Efficiency:
First off, the acoustic measurement does not cover the entire frequency response of the speaker.  87dB is how loud the sound was when fed a 1 watt signal.  It may only be at it’s loudest at 1 kHz, and +- 6db or so at the rest of the useful frequency response.  Every 3dB of volume requires double the wattage to achieve, as volume is logarithmic.  So let’s say 80Hz-20kHz, since we have a sub, and assume that the speaker does not go below -6dB in that range, we have 4 watts to achieve 87dB at 8 ohms. 

Part II – Impedance
While the speaker may have a overall impedance rating of 8 ohms, all speakers will have impedance drops that will put additional strain on an amplifier.  Rather than get too much into it, let’s just increase the power requirement to 6 watts to deal with a minimum load of 6 ohms per speaker.

Part III – Distance & SPL
So now we are at a 6 watt signal to feed 1 speaker 87dB of sound… at 3 feet away from it.  THX reference level calls for 105dB peaks in maximum volume, so we need to make sure our 87 dB can get there. 6 steps of 3 dB are required to get the 18dB we need.  So we take our 6 watts and double it 6 times = a 384 watt signal!

Part IV Distortion:

Amplifiers amplify all sound, good and bad.  Many receivers inflate their power specs by using large distortion percentages (anything above 0.1% in my opinion) for the specs.  We’ll need to bring the power level back down to acceptable distortion levels, which will reduce overall available power.  I mean sure it can do 100 watts, but if it sounds like crap am I going to turn it up that high?  Probably not.

So that 100watt per channel amp can easily be more like a 35 watt per channel amp when actually driving 7 speakers without appreciable distortion.  In other words there isn’t a lot of clean overhead for volume spikes or increasing the overall volume. 
A stand alone amp will provide much larger reserves of power, with less overall distortion. In almost all cases it will be superior to the amplifier built into the receiver, and can result in a dramatically improved soundstage.

Posted by Chirpie  on  03/17  at  08:58 AM

Dramatically improved soundstage? I don’t buy it. So long as your amp is running within it’s ability, there is no way in heck it should be affecting the sound that much.

About the only area a better amp will help is in the dynamics. An important consideration to be sure, but I don’t think people should be expecting a dramatic increase in actual sound quality.

If the sound is being affected that much by the amp, and it’s not being pushed into mild or severe clipping, something is amiss.

Posted by Chirpie  on  03/17  at  09:17 AM

“6 steps of 3 dB are required to get the 18dB we need.  So we take our 6 watts and double it 6 times = a 384 watt signal!”

I’m confused… I came up with…

87 db at 1 watt at 1 meter
90 db at 2 watt at 1 meter
93 db at 4 watt at 1 meter
96 db at 8 watt at 1 meter
99 db at 16 watt at 1 meter
102 db at 32 watt at 1 meter
105 db at 64 watt at 1 meter
108 db at 128 watt at 1 meter
112 db at 256 watt at 1 meter
115 db at 512 watt at 1 meter
118 db at 1024 watt at 1 meter

Posted by Paul  on  03/17  at  09:34 AM

We were doubling 6 watts 6 times, not 1watt.
6x2x2x2x2x2x2=384 watts

Posted by Chirpie  on  03/17  at  09:35 AM

Nevermind Paul, I missed the extra watts you tacked on for the ohm load. Peace!

Posted by Pische Herkoon  on  03/17  at  11:18 AM

Well if you pull or spread sound by advising 6x3x3 or piggy- back the gander you won’t gall the perverse.  I think you could configure the modular psyche to agile the outcome.  Use your ears for once and hear what the sound is cementing.

Posted by Paul  on  03/17  at  11:28 AM

Like I said in my long post below, it’s not so simple.  There are still a lot of other things that can be looked at, but quite a few are not directly impacted by the amplifier, so I passed over them.

Perhaps we can agree to disagree about the importance a great amp can play, I guess I think that the differences can be dramatic, and you say they are subtle at best. 

My experience in moving from a receiver to the same receiver with seperate amplification was a massive difference.  I went from an Onkyo 875 receiver to using the Onkyo as a processor, with seven outlaw audio monoblock amplifiers.  I didn’t swap speakers, I didn’t move anything, the sound just got better.  Even my wife thought it was a huge difference, and I’ll admit, that surprised me.

If you think it wasn’t the new amps that made the difference I’d like to hear your theory.

Posted by Mark  on  03/17  at  01:44 PM

I was hoping to read something about the benefits of Bi-amping.  Of course this depends on the capability of the speaker.  Any thoughts?

Posted by Paul  on  03/17  at  03:39 PM

Hi Mark,

For the most part bi-amplification is only required for commercial applications where extremely loud volumes are required.  Biamplification will let you run lots of power to the woofers and less to the mids and highs which don’t normally require a ton of power. 

Back in the day when two speaker systems were the norm, and inexpensive amplifiers did not have the power they do today bi-amping was a little more common. 

Powered subs have basically eliminated the need to bi-amp speakers, as your processor should be crossing over the woofers on your front speakers above the frequencies that the sub produces, nicely eliminating the need to bi-amp.

Hope that’s helpful.

Posted by Todd Charse  on  03/17  at  10:21 PM

Good points thanks answered my questions without me asking it!

Todd Charske

Posted by Craig  on  03/18  at  12:06 AM

Its a mistake to think that bi-amplification is for commercial high SPL applications.  In fact using active crossovers and separate amplifiers for each driver will dramatically increase the clarity of the sound.  I think that eliminating passive crossovers and instead using high quality active crossovers is one of the best ways to improve sound quality.  As an example, a popular HT speaker, Paradigm, offers some of their models bi-amplification ready and states on their web site that this will improve sound quality.  My front speakers are 3-way tri-amplified and the sound quality is incredible.  Also, using powerful amplifiers, even for low-level listening is fantastic because there is so much available headroom.  The sound is unstrained and dynamics are fantastic.

Posted by Kris Berger  on  03/18  at  07:46 AM

Assuming you don’t run your receiver in the 1500 square Ft acoustically dead space (another word we are talking about typical living-room/HT environment), you should have adequate power as is.
If that’s the case, you will benefit the MOST by investing in SPEAKERS upgrade.
At the today’s level of technology, speakers (together with their placement and room acoustics) are BY FAR the most critical/influential factors in sound reproduction.


PS Craig - only double-blind (AB or preferably ABX) tests with level matching to less than 0.1 dB difference wold reliably reveal any possible change in sound quality. That has been proven scientifically countless times.
What you most likely heard (aside from unknown problems with your previous amp/receiver) was level mismatch + “placebo effect”.


Posted by CJ  on  03/18  at  10:51 AM

Chad, I truly believe that you would benefit the most by having a consultation.  (In case you are wondering, I’m on the west coast so there is nothing in it for me.)  A little background is in order:
Sometimes when I design a home theater system I have to weigh the dollar amount available to see if I go w/a receiver or separates, and this will determine what speakers I match with which amp/preamp or receiver.  In addition to this, I also have to visit the space so I can better understand the viewing/listening area in relation to the speakers and the display.  All this has to be factored in.  My first question to you would be, ‘what do you mean by more punch?  In other words are you trying to make the system play louder?  (With 130 watts/channel, you SHOULD be putting out some high SPL’s, enough to make some viewers/listeners uncomfortable.)  Or is it that you want it to play louder because you are missing clarity or some other find nuance that you are hoping to gain with more power?  Possible solutions could be… 1. Your current speakers have a low sensitivity rating.  Obtaining a speaker with a higher sensitivity, greater than 3Db when compared to what you have would DOUBLE the output.  2. Speaker placement isn’t ideal or the room could use acoustic treatments to provide better clarity and imaging.  3.  Maybe getting a bigger amp really is the solution.  Either way, it would behoove you to meet with your local A/V specialist for a consult.  The initial outlay in exchange for the information gathered would be well worth it.

Posted by Fat Larry Powertoss  on  03/20  at  11:28 AM

If you look at your ears as a set of speakers you wouldn’t really worry about 7.1 surround sound.  You have two ear holes which means you only need two speakers, maybe four at the most.  The brain can only handle 6 hz of power per day so what is the point of having 7-18 speakers floating above your head or running under your feet?

Posted by rlw  on  03/20  at  12:33 PM

Fat Larry, are you for real?  You need to go back to school and get some education, you clearly slept thru all your classes.  Your logic implies that since we only have 1 mouth we should only eat one kind of food.

Wake up, bro…


Posted by Paul  on  03/20  at  01:26 PM


I’m going to be nice and assume that you’re actually interested, and try to answer your question.

We have two ears which are more like microphones than speakers.  That’s where your statement was faulty. The ears take in sounds from all around around us, and when interpreted by the brain, we can locate what direction a sound is coming from.

The sound has to come from everywhere because in real life, we are ‘surrounded by sound’ and sound travels in waves which can bounce all over the place.  Since most speakers send sound out in front of the speaker and not in a spherical pattern our brain can tell that the sound is coming from 1 speaker pretty easily. 

To date, no amount of technical tricks or processing that I’m aware of has made a single speaker fool the brain into thinking sound is coming from all around.

When we add more speakers (or drivers) and introduce processing tricks to feed them, we can actually surround the listener with sound from all sides, hence the term ‘surround sound’.

Sound engineers have to mix the sound to best approximate what each speaker should radiate to convince the brain that it is in the middle of whatever movie scene you are watching.  Each speaker can radiate different sound, and put it out at different times and volumes in order to help you localize where the sound is ‘supposed’ to come from.

To a point, more speakers in more locations make it easier to have sound come from a specific location to add a sense of size, scope, power, height, depth, whatever is trying to be expressed, but only if the soundtrack is recorded with all of that information, and your equipment knows how to interpret it properly.

Where does it end?  If I knew, I’d be a rich man, but a lot of people think that we’re not done at 7.1 yet.

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