What Power Amplifier Should I Buy?

Also, of course, having a room that is too reflective acts as a tone control, making the speakers sound brighter and short of enough bass.

In these cases some damping around the room can really help the bass bloom, in addition to improving imaging and clarity.

A good test for this is to get close to your speakers.  Do they suddenly sound much better, with a better bass to mid and treble balance?  Then it's your room.

@erik_squires 

Thanks for the suggestions.

I use REW to characterize and help me improve my sound system. I have extensive traps from a company called "Real Traps". I know where the resonances are. I understand that dips in FR are hard to compensate electronically.

I normally test every component. First, electronic performance and second, in-room performance (listening).

My speakers don't sound any different close up.

What kinds of measurements am I not doing that you think would help me to further understand the performance of my system?

Thanks.

Hey OP,

If your speakers still lack oomph close up it’s not your room for the most part, but it could be your overall levels. Can you post your full range response, including sub and mains?

I should mention, I have a Hsu 15" sub as well and well integrated with the main speaker's it's never lacked for guts.

Hi Kevemaher!

Hate to tell you this, but loudspeakers are very imperfect devices, and frankly there has only been limited progress over the last fifty years. The field is mostly limited by materials science and the cone and dome materials we have to work with. Software synthesis has advanced crossover design since the crude efforts of the Sixties, but cone materials and magnet design are only a little better.

It’s a fact of life that dynamic compression is a problem with low efficiency loudspeakers, which why they are unsuitable for PA, concert, or movie theater use. Watts are nearly free these days, but a multi-kilowatt amplifier at home will do nothing more than destroy the loudspeaker. It comes down to voice coil temperature. Copper has a temperature coefficient, which means it gets less conductive as it gets hotter. Not only that, the heating/cooling cycle is quite slow, on the order of several seconds, much slower than the dynamics of the music being played.

So in practice, just throwing watts at the loudspeaker does not solve the problem of dynamics. If you really want 110 dB peak dynamics, you need more efficient speakers, not a kilowatt amplifier. But scaling down is a reasonable goal, say, maybe 95 dB peaks. With speakers that are 85 to 88 dB/meter/watt efficient (very typical real-world numbers for audiophile speakers) 60 to 100 real watts should be plenty, with any extra just there for headroom.

If you crave headroom, bigger amps are not the solution. Go ahead, try a 500-watt Class D amp and see if it sounds more dynamic. Maybe a little, but much less than you would expect. On the other hand, try a 95 to 100 dB efficient loudspeaker and you will be physically stunned at the headroom, and your craving for more power will disappear.

What’s going on is the more efficient speaker is throwing away less power in the voice coil for a given SPL level. Hot voice coils are very undesirable, and not just for reasons of reliability. There’s no good mechanism for active cooling, nothing like a tiny fan or anything like that. The heat radiates into the thermal mass of the magnet, which in turn gets hot, and that heat convects into the enclosed air of the cabinet. Don’t worry, there’s no risk of fire unless you feed that 500-watt amp with full power sine waves.

But ... if the speaker is four times as efficient (6 dB higher), guess what, there’s four times less heat radiated by the voice coil for the same SPL at the listening position. And the amp can be four times smaller too. However ... there’s no free lunch. The bass enclosure volume grows in direct proportion to the efficiency (if the F3 low-frequency cutoff is held constant). So efficient speakers are necessarily bigger, or have higher cutoffs in the bass region, or a combination of the two.

These is a long-winded way of saying don’t expect big dynamics from small speakers, no matter what the reviewers say. And 500-watt amplifiers don’t necessarily cure the problem, although you can certainly try and find out for yourself.

In reality, speakers with efficiencies in the 87 to 90 dB/meter range typically experience power compression with amplifiers more powerful than 100 watts,

@lynn_olson To be clear, the amplifier power is only part of that, the other being the lower the efficiency of the speaker, the more thermal compression regardless of the power of the amp. The exceptions of course are ESL loudspeakers since they don't have a voice coil. 

@kevemaher Its a bit of a stretch to call your speakers '8 Ohms'! If you look at the impedance curve on the ASR site, you'll see that other than the box resonance, the impedance curve is closer to 4 Ohms (or less) in the bass region, where the power is most used.

There's a bit of math here; the woofer array of this speaker uses two 8 Ohm drivers wired in parallel for 4 Ohms. Since the sensitivity of the speaker is a Voltage measurement (2.83 Volts at one meter) the impedance of the speaker makes a difference.

So if 2.83Volts into 8 Ohms is 1 Watt, but that same Voltage into 4 Ohms is 2 Watts- a 3dB difference. If you were using the 8 Ohm taps on your Cary, it would have been struggling and no surprise you didn't get that 'tube sound'!

With tube amps the Efficiency spec (1 Watt/1 meter) is more useful since tube amps don't double power as the load impedance is halved. We already know the numbers, you simply subtract 3dB from the sensitivity value if a 4 Ohm load to arrive at the Efficiency, so only about 85dB.

If you want 'more dynamic' I really would consider getting a speaker that is both higher efficiency and also higher impedance (like actually 8 Ohms instead of '8 Ohm compatible' or '8 Ohms Nominal').

You don't lose any resolution by having a speaker that's easier to drive. In fact you may get more since hard to drive speakers cause power amplifiers to make more distortion, and distortion obscures detail. You want your amplifier to be loafing to do its job! That is when it will be the most musical.