Power

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Power

As some of you may remember, it is my considered view that good amplifiers do not have a sonic signature. Howevr, as you may also remember, that is only true if certain conditions are met. One of them is that the amplifier must have enough power to avoid clipping on dynamic peaks. The next question then obviously becomes whether this is an issue in real life conditions or not.

Ever since moving to a bigger house with a considerably larger listening room, and replacing my old Quad esl 57's with the modern but far less sensitive Quad 2805's I have had the nagging feeling that my old 2x45 watt Quad 303 power amplifier was stressed in louder passages. That suspicion was reinforced when I read about Alan Shaw's demo of the 2x500 watt that was occasionally drawn on peaks by the not even particularly insensitive Harbeth 40.1's as measured  during a demo in Hilversum in the Netherlands. It made me think.

So last summer I could buy a completely refurbished 2x140 watt Quad 606-2 (i.e. essentially the same amplifier as the later 707, 909 and QSP) for only 350 euro. And indeed: playing not very dynamic music at moderate levels there was abolutely no difference with the old Q303. But turning up the wick playing large scale dynamic music changed all this. The sound remained clean and the dynamics were far more life like.

So the lesson for me is that watts are indeed watts, but that if you are playing dynamic music in a large roon on insensitive speakers, you had better have many of them. This is all the more so since sound levels are measured on a more or less logarithmic scale: a bit more sound demands a lot more power. I may have to start saving for a set of Quad monoblocs. The reassuring lesson for others is that if you are listening to relatively sensitive speakers in a typical UK living room you do not need too many watts, and they will be cheaply available.

Willem

cheap quality watts

As a follow up, I want to point to what you can buy if you go the pro audio route (most affordable consumer audio amplifiers max out around 2x100 watt). Pro audio amplifiers are much cheaper and more powerful than typical consumer hifi amplifiers, and the following test by a French electronics engineer (using an expensive Audio Precision test instrument) shows they can be just as good:

http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fid...

The test is of a 2x350 watt Yamaha P3500s that sells for 500 euro. See here: http://www.yamahaproaudio.com/global/en/products/poweramps/ps_series/ As you can imagine from Yamaha, it is a very well made and rugged unit, with balanced and unbalanced inputs, a high pass filter if you want to, and it measures absolutely beautifully. Like nearly all pro audio amplifiers it has a cooling fan, but unlike with many others this is not permanently on but will only come on when necessary, when the amplifier is playing so loudly that you cannot possibly hear the fan. In short, it is a perfect home audio amplifier to drive insensitive speakers in a large room. There is also the 2x250 watt P2500s for 400 euro, and yes there are also more powerful models (up to 2x650 watt rms into 8 ohm for 625 euro, before you start bridging them for even more power) for those with ballroom sized listening rooms.

Willem

Mind the Speakers

Willem,

 

As the owner of a Quad QSP amp, a pair of 2905 electrostatics and a room corrector and sub, I must agree that adequate power headroom in one's system is needed for realistic listening.

 

The flipside of high power output from the amp is of course the ability of your speakers to handle it. Many an expensive mistake has been made by dynamic range enthusiasts unintentionally driving speakers beyond their physical limits. Good speakers may give little or no advance warning of imminent disaster, though thankfully the Quads come with built-in overload protection.

Roderick

the dangers of power

That is of course, all too true. Power has its own dangers, even if clipping by underpowered amplifiers is often even more dangerous for your speakers. However, these pro audio amplifers also have their own additional volume controls to reduce output, and on the Yamaha you can block those controls from prying fingers. In my own case, my Quad 606-2 has thus far failed to trip the overload protection on my Quad 2805's.  But the overload margin of electrostats is an altogether different story in any case.

Roderick, did you get some kind of room correction for your sub?

Willem

Room Correction and Quads

Willem,

 

Yes, after research I decided on the DSPeaker 8033s-II room corrector which I bought together with a new sub (BK Monolith Plus) after my previous REL sub bit the dust and was not readily repairable.

 

I have to say that I am quite pleased with, though still getting used to, the room corrector. I have a sofa where I and my family do the majority of our listening and viewing. The middle part of the sofa is deliberately placed in the Quads' sweet spot. To my surprise, using the room corrector to optimise the sub to the same listening position has produced a quite localised sweet spot there too. If you sit elsewhere in the room the sub's bass can sound window-rattlingly loud or too quiet, but in the middle of the sofa it sounds just fine, and integrates well with the Quads on material with audio content below about 40Hz. The rather extreme form of localisation is not what I had been expecting, though I know it is possible to optimise in more than one room position to reduce this effect.

 

Roderick

localised sweet spot

This is indeed a possible outcome, but I am surprised it is so extreme. In my case there is only a bit of it, but in the end the result is better everywhere. On advice from the DSpeaker engineer (I just called him over the phone) I placed my sub in the far corner behind one of my Quads. This gives maximum corner reinforcement and the least problems with nulls. The peak is then equalized by the Antimode.

The system also allows multiple measurements for more than one location, and can then average the correction for a wider area. Did you try that? Finally, there is, of course, always the option to use a second sub. I have not yet gone that route, but may do in the future. The advantage apparently is that you can optimize over a much wider area. Floyd Toole did some interesting research, both on multiple subs and on equalizing them: http://www.harman.com/sites/default/files/white-paper/12/11/2015%20-%200...

Willem

Where to place the Sub

I agree that sub positioning is indeed a key ingredient. In my present room I have placed the sub on the left-hand wall roughly in line with the end of the sofa. In my previous listening room I had placed the sub in the corner of the room behind the left-hand Quad.

 

With the previous set-up I had always perceived a small reduction in the accuracy of the Quad speakers' (normally pin-point) imaging across the sound stage. This applied whether or not the sub was switched on, so I concluded that it must be caused by reflected sound from cabinet of the the sub interfering with reflected sound from the back wall. Or perhaps it was all in my imagination. Anyway, whatever the reason, I was aware of it.

 

When I have got more used to my present set-up I will try moving speakers and tweaking optimisations again.

Roderick

amplifer power video

See here for a video of amplifier power needed on one particular occasion:

https://www.youtube.com/watch?v=bRMR9JZ1m0s

Willem

even cheaper watts

The Yamaha pro audio power amplifiers that I referred to earlier (and do read the test that I linked to) have just come down in price: the 2x250 watt (rms at 8 ohm) p2500s is now 298 euro and the 2x350 watt p3500s is now 359 euro. So I just bought a p2500s for my son. It should serve him well for many years to come.

Willem

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