What does moving from a 150 watt amp to a 400 watt amp get you?


Hi all, I’m coming back to tap the knowledge of the forum again.  I have a pair of revel ultima studio 2s that I very much enjoy. I’m currently running them with an Ayre V-5xe.  I’ve seen others say that these speakers need to be driven by 400 Watts to get them to sound their best.  I sort of understand the relationship between wattage and sound volume, but if I am not looking for “louder” what do I get with a more powerful amp?  I don’t hear clipping. More current?  But what does that do?  Sorry for my ignorance!
miles_trane
I use high power amps, but do not confuse power with quality. Two 300 watt per channel amps, at completely different price points, are not comparable. There are diminishing returns, but do not expect a $3,000 stereo amp to sound like a pair of $15,000 mono blocks.  
, but if I am not looking for “louder” what do I get with a more powerful amp? I don’t hear clipping. More current? But what does that do? Sorry for my ignorance!miles_trane

Don’t fall into the BS that more watts is more powerfull.
These 25w ML 2 amps
http://www.hifido.co.jp/photo/05/504/50446/c.jpg
can sound more powerful than some 500w amps on certain speakers, because it can deliver good current down to 1ohm, where the 500w may start to sag below 8ohms.
Good current delivery of an amp is a sign of a "tested" amp to be able to come "close" to doubling it’s rated wattage for each halving of load impedance.

In this case the ML2’s (slightly exaggerated)
25w-8ohm
50w-4ohm
100w-2ohm
200w-1ohm

Cheers George

@wolf_garcia  You haven't lived until you've heard a pair of original Futterman H3AA's with KLH Nines or Quad 57's! Sublime musicality rarely equaled!
Indeed. Your amplifier is more than powerful enough for the P3ESR. In fact, you will need to exercise some caution. You are fine. You did not say how large the room is, but if the room is medium size or larger, the only thing you could do to get a 'bigger'sound is add two small subs like the SVS SB1000 and an Antimode 8033 (but don't add subs if the room is small).
Thanks for the peace of mind. Yes, they are P3ESR's. I'm glad to know the amp is enough.. watts really are a funny measurement.
I use thousands of watts to provide clear sound for concerts I produce/mix, but have become part of the "Lower powered single ended tube amp cult," LPSEAC or as commonly called "lipseek" (you've seen the t-shirts, right?). By joining the cult you agree to a couple of things: You use efficient speakers (99db in my case, plus hundreds of watts in powered subs), and you collect tubes. For many decades (I'm 106) I've owned tubeless and tubed hifi amps with from 60 to 250 watts per side, biased class A-ish for at least the first few watts or something, and have enjoyed music spilling out of these things for years…but after joining the lipseeks I'm stuck. Nothing to my taste sounds better, clearer, or more emotionally engaging than a properly utilized group of single ended glass bottles shoving electrons around. Headroom SCHMEADROOM I say (as long as you use efficient speakers or sit with drivers a foot from your head). I haven't tried an OTL amp…yet...
Thanks all for the incredibly helpful information (even the humorous responses!).  It is doubly dangerous to be armed with science AND personal experiences.  

Nutty / Aalenik - I'm using an ARC Ref5SE preamp currently.  It took me about a week, maybe more of long listening sessions to fall in love with it.  Initially I was a bit disappointed in the changes in moving from the K-5Xe - but by the end of two weeks couldn't move back.  

Overall I'm pretty pleased with the way things are sounding now.  Occasionally there is a bit of harshness in some of the highs - but it is minor.  The best systems I have heard make me want to keep nudging the volume up as I listen.  Mine seems to have a point at which louder is not better.  I don't think I'm listening at ear-splitting levels mind you - generally when listening "loud" it rarely exceeds 82 to 83 db.
Thr increase in power might offer more driver protection from amplifier clipping.
Robertjason75, to add to Willemj’s questions and comments, as I alluded to in the last paragraph of my lengthy post yesterday I don’t think that for most listeners the capability of cleanly producing 105 db peaks at the listening position is necessary on most or all of their recordings. And I believe that a majority of audiophiles do not have systems providing that capability.

And even though as I mentioned I listen to a lot of classical symphonic recordings that have been engineered with minimal or no compression, and consequently have extremely wide dynamic range, that I listen to at average volume levels of perhaps 75 db or so, there are relatively few recordings in my collection which will reach brief dynamic peaks in the area of 105 db. (In addition to basing that conclusion on SPL measurements I have performed using a Radio Shack digital SPL meter set for fast response and C-weighting, I have used a professional audio editing program on a computer to examine the waveforms of some of the widest dynamic range recordings in my collection. Doing so readily allows me to determine the full amplitude of even the briefest high volume transients, and compare it to the average level of the recording).

So without knowing what kinds of recordings you listen to, or the answers to Willem’s questions, my guess is that you don’t have a problem.

Regards,
-- Al

Which Harbeth speakers are these - the P3ESRs? If so, your amplifier is at the beefy end of what they can handle.
If not, the bigger Harbeths are more sensitive than this. How big is your room?
I'm hoping you can help me understand this 105db idea better. My speakers, harbeth, are 83.5db sensetivity. If I subtract 10db, add back 3db were at 76.5db. To get to 105db I'd need 30db's provided by the amp (A 1000 watt amp!). I'm a budget audiophile. I run them currently on a parasound 2125 which is 150W @ 8 ohms, 225W @ 4 ohms..  the harbeths are 6 ohms... so based on the chart above I'm likely getting a 22db boost from the amp.. now we're at 98.5db--short of the 105db goal.

My question, sorry I'm a bit of a newbie, is my amp likely clipping? I don't crank music, but listen at a good volume 75-85db spls according to my rack shack meter.  


A correction to a miswording in item 2 of my previous post.  When I said ...
...for a 4 ohm impedance the SPL produced in response to an input of 2.83 volts will be 3 db less than if the spec had been based on 1 watt, since 2.83 volts into 4 ohms corresponds to 2 watts.
I should have said:
...for a 4 ohm impedance the SPL produced in response to an input of 1 watt by a speaker whose sensitivity spec is based on 2.83 volts will be 3 db less than if the spec had been based on 1 watt, since 2.83 volts into 4 ohms corresponds to 2 watts.
Regards,
-- Al
 

I'm sorry to say that most of the responses you've received are not useful, and some are nonsense.  (There are some good ones too, so don't everybody feel insulted.)

I'll try to help...  In general, more watts are not needed for more volume.  They are needed for more 'headroom'.  In a musical recording, the transients (leading edges of any sound) are MUCH higher amplitude than the rest of the signal.  Having plenty of headroom allows your amp to produce those (fraction-of-a-second) transients at full volume without attenuation or 'clipping'.  That results in a much richer, more robust and more REALISTIC presentation.

It's also true that less efficient speakers will perform better with plenty of wattage & current, because they simply need more power to 'sing'.  I tend to like the sound of low-efficiency speakers mated to powerful amps, but there are many exceptions (& that's my personal taste).

That being said, your Revels are rated at about 88 dB sensitivity w/ nominal 6 Ohm impedance.  That is a moderate, rather than difficult, load, and should not require 400 W/ch.

What's more important is the QUALITY of the amp!  The Ayre V-5xe is a nice-sounding amp. You could easily find a mega-watt amp that is not so well-designed... and take a step BACK in sound.  I would try to audition the Revels with a more powerful amp before spending any $$. You may find that there's no real advantage.

BTW... what pre-amp are you using?  Have you tried a tubed pre-amp?  I've had great success matching solid-state power amps with tubed pre-amps (incl. my current system). That gives you the tight, well-controlled bass associated with solid-state as well as the beautiful mids & highs that only tubes seem to provide.

Anyhow... I hope that helps. 

Bruce, thanks for providing the Musical Fidelity writeup, which is excellent IMO, and is similar to some analyses I have provided here in the past. A couple of minor nits:

1)The reference to SPL (sound pressure level) falling off at 6 db per doubling of distance applies to most non-planar (box type) speakers. The rate of fall-off for planar speakers such as electrostatics is significantly less.


2)More often than not sensitivity is specified as the SPL produced at 1 meter in response to an input of 2.83 volts, rather than in response to 1 watt. For an 8 ohm impedance those results will be identical, since 2.83 volts into 8 ohms corresponds to 1 watt, but for a 4 ohm impedance the SPL produced in response to an input of 2.83 volts will be 3 db less than if the spec had been based on 1 watt, since 2.83 volts into 4 ohms corresponds to 2 watts.


In any event, Stereophile measured the OP’s speakers as providing an SPL at 1 meter of 89 db in response to an input of 2.83 volts, which corresponds to 1.6 watts into what I would consider to be its 5 ohm impedance (see my earlier post regarding the 5 ohm figure). 1.6 watts is about 2 db more than 1 watt, so the speaker will produce 87 db in response to an input of 1 watt. The 240 watt capability of the amp into 5 ohms (again, see my earlier post) corresponds to about 24 db more than 1 watt. Two such speakers listened to at a distance of about 10 feet when driven with 240 watts will produce an SPL of approximately 87 + 24 + 3 -10 = 104 db, very close to the 105 db minimum recommendation provided in the paper.


And as I mentioned earlier, an amplifier capable of providing 400 watts into 5 ohms would add very little to that figure, 2.2 db to be precise. Unfortunately, IMO, it appears that very few of the responses by the others have focused on the OP’s situation in a comparably specific manner.


All of this assumes, btw, that the speakers are capable of handling these high power levels without significant thermal compression or other non-linear effects becoming significant. I have no knowledge of the maximum power handling capability of the Revel Ultima Studio 2, or of how well it would perform as its power handling limit is approached.


I would add that while I personally listen to a lot of classical symphonic recordings that have been engineered with minimal or no dynamic compression, and consequently I have stated in some past threads here that 105 db at the listening position is the minimum peak volume capability of any amp/speaker combination I would consider (which happens to coincide exactly with the paper’s minimum recommendation), my perception has been that the majority of audiophiles do not listen to recordings that when played at their preferred volume levels would come anywhere close to such high peak levels. With peak levels not exceeding even 90 db in many cases that have been mentioned in past threads here. I believe the main reason for that is the high degree of dynamic compression that most recordings in various genres, especially pop and rock, tend to be engineered with.


Thanks again. Regards,

--Al


Miles,  There are many well respected in the industry the agree with the following.  Happy reading.  Bruce

From Musical Fidelity Website around 2009

 

Technical background to our dynamic range/power claims.

 

This section is slightly technical and may take you a few minutes to read. We would like to take you through to the basic technical elements that make up a hi-fi system and explain how they go together.

 

Loudspeaker sensitivity

 

Loudspeaker sensitivity is a measure of how much sound a loudspeaker will give for 1 watt at 1 metre. It is critical to note that the basic measure of sensitivity is at 1 metre and not at a typical listening distance of about 10 feet or 3½ metres.

Sound attenuates (reduces) over distance at the rate of 6dB with each doubling of the distance. At 2 metres distance from the loudspeaker its perceived sensitivity is reduced by 6dB. At a normal listening distance of about 10 or 11 feet from the loudspeaker its perceived sensitivity will be reduced by approximately 10dB.

 

This is the factual basis for our claims about how much power a system would need for a decent hi-fi dynamic range. We reiterate that this is not made up or marketing hype, it is scientific fact.

 

Loudspeaker sensitivity – is it real?

 

Regrettably, most loudspeaker sensitivity ratings are not particularly accurate and are regularly overstated by 2 or 3dB. We have seen several examples of respected manufacturers’ products specifications overstating their sensitivity by 5dB or more.

 

This does not sound like a big deal, but it has tremendous implications for the power required by the loudspeaker to deliver proper dynamic range.

 

Amplifier power – confusion reigns.

 

This is the source of much misunderstanding. Amplifier power is specified in watts, which are a measure of heating power. They have no apparent relationship to what we hear, as they are a linear measure. Loudspeakers (and our ears) perceive things in dB (decibel) steps. These are based on a logarithmic relationship.

 

1

This is the fundamental mismatch between what your ears perceive and how amplifiers are specified. The solution to the problem is to recalibrate watts into dB steps. The results are below, in a chart of watts converted to dB steps. For convenience we have started our chart at 50 watts. These figures are not made up they are fact.

 

dBW Watts         dBW Watts

17      50             24      251

18     63             25     316

19     79             26     400

20     100           27     500

21      126           28     630

22      156           29     795

23      200           30     1000

 

As you can see, as soon as you calibrate amplifier power in dB watts, you get a dramatically different view of what amplifier power really means.

 

First off, you can see that what looks like a large increase in amplifier power, for example from 50 watts to 100 watts, only gives an increase of 3dB.

 

Things get really interesting as when you get to higher powers. You start needing vast amounts of power for each dB step. For example, only 1dB (remember 1dB is the smallest change in sound pressure level that the human ear can perceive UNDER IDEAL LISTENING CONDITIONS) is the difference between 400 watts and 500 watts. If you really wanted to hear a difference above 400 watts you’d probably need to go to 800 watts (3dB) which should be audible.

 

You can see why amplifier manufacturers want to sweep these figures under the nearest carpet; they make most of their claims look ridiculous as they predict that most loudspeaker/amplifier combinations will have only limited dynamic range.

 

2

How much dynamic range do I need?

 

Some years ago John Atkinson (current editor of the Stereophile) made some measurements of live music using accurate equipment. He recorded 109dB peaks (brass and percussion) and the quietest was 63dB (solo violin) a variation of 46dB from the quietest to the loudest moments – a huge dynamic range.

 

The question is what sort of dynamic range a really good hi-fi system should have.

In our opinion, an ability to produce unclipped peaks of 105dB is the minimum starting point for a really good hi-fi system. You are welcome to debate different figures, but that is our basic position.

 

If you listen to small scale chamber music or usually listen at quiet levels, you will not need the peak capacity we deem necessary. But if you are trying to recreate the listening experience at reasonable levels, 105dB peak is not overly generous.

 

How do you put all this together.

 

Assuming that you have accepted the scientific facts this is how you determine what your system can produce.

 

1. Take your loudspeaker sensitivity (better yet check back to a technical review to find out what its sensitivity really is). Deduct around 10dB for the SPL (sound pressure level) attenuation over distance. And then add back 3dB because there are two loudspeakers in the room.

 

Now you have arrived at the practical, real world, in-room sensitivity of your loudspeaker system.

 

2. Decide what peak level you want to achieve. We think 105dB is about right. Some people think 110dB is more appropriate. It’s up to you.

 

3. Deduct the result of 1 above from your decision about 2. This is how much amplifier power you require in dB watts.

 

 

4. Use the chart above to translate your dB watts result in to ordinary watts.

 

General overview.

 

None of this is intended as criticism of amplifier or loudspeaker manufacturers.

 

You could regard it as a criticism of magazines and shops for not bringing it to your attention. We have been banging on about this for about ten years and many people have reacted adversely because they believed it was just marketing hype.

 

This is not marketing hype, this is scientific fact. Many people do not like the result of a scientific analysis of their equipment but that does not alter the scientific facts.

 

People have objected to our position claiming that their system sounds great. It might. However, you can’t escape the fact that, if they have a low powered amplifier and relatively insensitive loudspeakers, the system must be clipping, distorting and limiting regularly, which must dominate the listening experience.

 

Maybe the listeners like distortion clipping. Well, each to his own and good luck to them. If you want your hi-fi system to produce as close an approximation to the real live performance as you can get, then you must ensure, for a start, that your amplifier is not clipping.


I have been in this game for over 40 years and spent many thousands on equipment. I even build my own speakers now. I have less than 1000.00 in my current speakers and would challenge any 5000.00 soeaker in the world for sound quality!

A lot of these responses are flat-out wrong and / or confusing! Yes, your speakers WILL sound better with a 400 watt amp (asumming equal quality), If someone thinks higher amp power is just about maximizing volume, they are clueless about music reproduction. It is more about the dynamics of the sound throughout the volume rang. Your speakers will sound more dynamic from lowest to highest volume.

This means bass will sound tighter, treble will be more distinct, mid range will be slightly clearer but not necessarily more detailed or musical. That depends on the quality.

I would would not sell your amp and get a lower quality amp with more power. In that case you would be trading musicality for dynamics. That is the challenge in musical reproduction, combining musicality with dynamics. The only way to do that is spend more money!
@douglas_schroeder Your analogy fails because you changed 2 parameters with the assumption the new amp had a different (better?) quality. Reverse the terms such that the older man is heavier and see if it still holds true. 

POWER !   I had not heard my DQ 10s, not really - until I went from a 60w/ch tube amp to a 250w/ch ss amp.  It then rocked out! drums were heard AND felt, bass lines became distinct, dynamics went through the roof.  It became capable of inducing FEAR also when in a film we were watching had some low, threatening sounds played.  

Let none tell you it doesn't matter, my friend. 
“What does moving from a 150 watt amp to a 400 watt amp get you?”

250 watts yuck yuck!

sorry, just couldn’t resist!!
It's all about sensitivity and headroom. If your speakers make 90db with one watt. Then they will use one watt no mater if you have a 50 watt or 500 watts amp connected to them . The only difference is you paid a lot for those extra 499 watts that your not using. You need headroom for the loud spikes especially in classical music but 15db should be more than enough. So to get that headroom you need your amp will need  to deliver 16watts. Quality watts are expensive.  Doubling an amps power often means a doubling any of its problems plus a quadrupling of the price. If you don't need them then it's better to go with a lower powered amp with higher quality watts.
Invite a 170 pound 60 year old to hit you like a football tackle. Then invite a 260 pound college football player to hit you like a football tackle. Take the data generated and apply tangentially to amps.  

Glad I could clarity that for you.  ;)  
I don't see why an average sensitivity speaker (say 88 to 91 dB/Watt) with an impedance that reaches a low of 3-4 ohms would need a 500-watt amplifier. Every doubling of the output level requires a tenfold increase in the power delivered to the speaker. So, let's assume we have a speaker with a 90dB/watt sensitivity. 10 watts will result in a 100 dB SPL (sound pressure level, the actual measure used to describe the loudness we hear). A 100 watts will result in 110 dB SPL. Considering that most amplifiers can supply, for a very brief period, double their RMS, or continuous, power output, a 200-watt brief signal will result in nearly a 115 dB SPL sound level. Other than using your rig to make people deaf, or induce tinnitus in their ears, or develop some really bad relationships with your neighbors, there are very few musical events that go this loud. Maybe the very highest peaks of a symphony will reach these levels. So I will always vote for quality over quantity, provided that the amplifier I choose will meet my basic requirements for reproducing what are to my ears, loud enough peak SPL's.
+1 what initforthemusic and timlub said. MOST of the rest of the responses do not match my 45 years of experience in this hobby. But quality will matter over quantity, and I love great big power supplies.
Good listening,

I've read the 'stereo review' magazine from 1970 to it's end. they say that to hear a difference in volume you have to triple the wattage to hear a 3 decibel increase. from 100 watts you need 300 watts. from 300 watts you need 900 watts. from 900 watts you need 2700 watts. to all out there , is this still true??
A big amplifier is useful for a clean sound on dynamic peaks as in symphonic music. Harbeth's Alan Shaw recently did a demonstration of his big M40.1 speakers and the digital power meters on the monoblocks that he was using indicated they were delivering more than 500 watts/ch on peaks.
Fortunately beefy pro audio amplifiers do not cost mega bucks, and can be very good for home audio. See here for a serious test (with an AP audio analyzer) that makes precisely this point: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...
Omg this topic again. More watts doesn’t mean better sound quality it just means you can play your music louder. You will never use 450 watts unless you listen at an ungodly volume and you have a very, very large listening room. The fact is most people use about 8-15 pure watts when listening to music. Focus on the sensitivity of your speakers before spending ridiculous amounts of $$$ on a amplifier based on how many wpc it has. 

Cheers
Well, I agree with most of what has been said.  Normally the advantage of adding power, isn't necessarily adding power itself, but having the power supply with larger current capability. Power supplies don't have to be regulated, but a good regulated power supply along with good current capability normally provide a amp that is dynamic and full... of course a poor design can kill that whole theory.  Overall, your Ayre is a nice piece of equipment.
Correction to my previous post:  In the first paragraph "music music" should have been "most music," of course.

Regards,
-- Al
 
I would make several points:

1)As a practical matter what you are using with this particular speaker is a 240 watt amp, not a 150 watt amp. The amp is rated at 150 watts into 8 ohms and 300 watts into 4 ohms. The impedance curve of the speaker, as shown in Stereophile’s review, indicates an impedance averaging about 5 ohms across almost all of the frequency range below 1 kHz, which is the part of the spectrum that encompasses most of the energy of music music. It can be calculated from the 150 watt/300 watt 8 ohm/4 ohm numbers that the amp is capable of 240 watts into 5 ohms.

2)The difference between 400 watts and 240 watts is about 2.2 db, which while not quite negligible is not much of a difference.

3)IMO design differences between amplifiers are likely to be vastly more significant from a sonic standpoint than a 2.2 db difference in maximum power capability.

4)Everything else being equal more amplifier watts = more amplifier $. IMO it is usually desirable to have as high a percentage as possible of the dollars one chooses to invest in an amplifier go toward quality rather than toward watts, assuming the number of watts is sufficient to avoid getting near the amp’s clipping point.

Good luck. Regards,
-- Al

Over the years I've upgraded amps from lower to higher power models, and in every case, the result has always been better sound quality.

That may not be attributable to just the extra power.  When I've made the jump to a higher-powered amp, it is usually a better quality model as well.

I currently use an amp that's rated at 450wpc, and when I'm really driving my speakers to (for me) loud levels, I'm using WAY less than the power this amp is capable of delivering, but in no way has this amp sounded like it's straining to drive those speakers.
miles-train, 
the difference in watts are just numbers. you will notice that the same number of watts in one unit is NOT the same as the same number or watts in another amp. A good example are Naim amps, whose 50 watts are more powerful than many manufacturers that tout 100watts. Its just a conservative estimate of wattage for Naim. and many times, manufacturers are describing power in terms of amps or dB of gain. 

the point I want to make is about gain, different than watts or power.

Maybe an analogy: if 150 watts compared to 400 watts was like 5 gallons of gas in your car compared to 15 gallons of gas in your car. But you have the choice of the amount of gas octane you put in your tank.

In CA, we have 87, 89, or 91 octane. So the octane will give you boost, speed, and run a lil hotter. Meaning that the gain of the 150w/5 gallons vs 400w/15 gallons can be different. you might have high gain (91 octane) with 150 watts or low gain (87 octane). Same for the 400w amp Each amp manufacturer is different, and they try to establish an even amount of gain that sound pretty good at low or high volume levels.

But generally speaking, a 400w unit will give you more gain at lower volume levels than 150w amp. The point is that the higher the gain, the better your stereo will sound at lower volumes, b/c the 91 octane will distribute the energy to more of the hi and low frequencies and tend to give more of a "live" sound. doing this will take some energy from the mids, since the energy is spread out (think of a bell curve here) to the right and left extremes (the "bell" in the middle lowers). 

Last, I would try to explain this by using the Easter Electric BBA, Booster Buffer amp. It is a small unit, has 3 tubes and a transformer. Only 2 knobs on the front: VOLUME AND GAIN. in 10 years of audiophile, it is the most valuable unit I have had in terms of learning how to control sound through my speakers, and how to mitigate bad recordings and get to sound good. e.g. if I am playing a CD with too much gain ("loudness wars"), I reduce the gain and match to a volume that sounds good. If I am playing a poorly recorded or old LP with low gain or flat dynamics, I will turn up the gain to give better hi/lo dynamics and breath new life into it. 

I know this doesn't give a concrete answer, but I'm hoping the theory will help you figure out what will work best for you.Last, I dont know if you are familier with SimAudio, but they are know for having strong, solid power from amps (and gain, but not too much). In that respect, they are similar to the Naim amps referred to above. 


I’ve seen others say that these speakers need to be driven by 400 Watts to get them to sound their best.
If you really need 400 watts to make a speaker work, in a nutshell the efficiency of the speaker is borderline criminal. The reason why is simple- if you want an amp that really sounds like really real music, you can count on one hand the number of amps that make that kind of power as well. With almost any technology, the larger amps tend to be less musical. The reason is that First Watt you hear so much about- while that is a bit of a generalization, the fact is that many amps at lower power levels actually make a fair amount of distortion. So if you have a 400 watt amp as opposed to a 150 watt amp, that distortion level might be a bit more audible.

How this manifests is that you loose low level detail- and there is a tendency to turn it up to try to get more impact.

If you're not clipping your amp right now, I'd hang on to it!
I think you have an excellent amp and I'd leave it at that. 

You need a lot of power to significantly increase volume. Doubling the volume requires 10x the power. Without doing the math, volume wise you may gaine around 4 dB going from 150 to 400. ( 150 to 300 is 3 dB). 

But  you may need a lot of current, which your amps should have. 

Best,


Erik 
It depends how power is specified.  For sinewave it will be 33% louder.  For music signal it will depend on the headroom of the amp, type of music, type of speaker, etc.  
I have Revel Ultima Studio 1's and have half a dozen Power Amps. They are not a difficult load, but the more high quality Watts/Current you put into them the better they sound.  I've ran them with Amps 150 W. up, they just seem to lap up more high quality Wattage. They sound best with the Vincent SP-998 Mono Blocks, conservatively rated @ 300W 8ohms, 600W 40hms, 50W Class A. Everything just opens up, grip on bass, dimensionality, soundstage, bigger more powerful, more control,more musical, everything.

Must stress, make sure they are high quality Watts/Current. not just run of the mill, Parasounds, Rotel, Emotiva etc. All Watts are not created equal.
If you add a great sub to any speaker, you automatically need only half as much power for the speaker. If you bi-amp, same thing for the m/t drivers.
about 3db, is the difference....but it generally seems like more.

I'm messing with a DC capable amp that can put out an approx 1.5 horsepower (1100watts) into the 4 ohm speaker load I'm running. Custom skaaning drivers, and so on. I'm kinda scared, a bit. One mistake and ..thar she blows...

The bulk of compression effects is now on the speakers. I was using 150 wpc before, and the amp  was working for it. the 1.5hp is not working for it at all, and can easily exceed the capacity of the speakers to hold themselves together.

One generally has to re-orient their thinking a bit, when putting extreme power into a 'standard' sort of speaker load. To go back to tube preamp and high power SS amp pairing, kinda thinking. Like driving rear wheel drive extreme horsepower cars, in the winter. Every move is clearly calculated in potential and in motion.
Look at Pass 350.8 it is a wonderful sounding amp with plenty of power to spare.
Everything sounds better at lower volume levels when you have lots of good clean power. The sound tends to get better when you drive them up to around 35watts then things really open up, improvements in tightness, control, speed, are usually noticed right away. You will end up loving the volume knob a little more I think :-)


Matt M