Harbeth M40 room setup - nearfield or not?

[kckwong723]

Dear Alan,

So what power range of amplifiers is sufficient to push M40 (not M40.1)?

I've got a pair of M40 around one month ago. My room dimension is 20 x 16 x 9"5' feet. I place the speakers along the long wall. The distance between the speakers and the front wall is about 4 feet. Distance between the tweeters of the speakers is 9 feet. Distance between the speakers and listening position is about 10-12 feet. Sofa is just placed close to the rear wall.

Previously I used SHL5 pushed by a Chinese integrated tube amp Cayin A100T (4 x EL34 - 70W per channel) and I was fully satisfied with the combo performance. However, after upgrading to M40, I found the tube amp could not handle the woofers properly although the mid was still perfect. So I gave up the tube amp and used TacT Semi-Digital Amp (4ohms - 375W). Now the bass is now much more acceptable but TacT amp lost many aspects against the tube amp.

I have a plan to upgrade the amp. Densen pre/power combo or Gryphon Diablo is on my list. But I still wonder which power range of amp suit M40. SHL5 is very easy to push but I think it is not the case of M40.

What amp BBC is using to push (non-active) M40 in studio?

Someone said in this forum that M40 suit for a near-field listening. In my case, I may need to move my sofa around 3 feet forward from the rear wall but I still have not tried. But what is your opinion?

Here are some photos of my listening area. You can see I have not made any room treatment.

Many Thanks

Ken Wong

[A.S.]

Hello Ken and our friends in Hong Kong,

Excellent photographs which clearly illustrate your text. Do you have a coastal view from your balcony? The light suggests so.

I think the comments that 'M40 is designed for nearfield use' is really apt. To explain better what I mean by nearfield, there is already a video on the Harbeth website of the M40 in a nearfield set-up. You may have seen it already, but anyway I mention it again here.

The BBC are not really troubled by the selection of amplification for M40. In fact, we loaned them a very cheap rack-mount 19" stereo PA amplifier (cost only about $250) and it worked fine - but - they were using the speakers in the relative nearfield. You are not; your set-up is really for farfield listening. So what? Well, I've drawn on your picture the direct sound (green line) and just a very few of the reflections (red lines) from only the right side speaker. The situation is much more complex when both speakers are playing. Every object in the room without exception will, at some frequency or other, reflect sound, even the so-called soft furnishings such as your chairs.

What we hear at any point in the room is inevitably a combination of the direct sound plus the reflections. The further you are from the speakers, the more the relative balance between direct and reflections begins to tip towards the reflections becoming dominant. This is simply because the further from the speakers the more hard surfaces there are for the sound to bounce off, multiple times then on to your ears. The most surprising thing is that the brain can make any sense at all of this mess of sound waves, but miraculously it does.

So, what would I do in your situation? First, I wouldn't throw any serious money at this for now. I wouldn't worry about changing the amp now. That can be explored later if necessary. I'd try bringing the speakers in towards each other by 2-3 feet in total (1m or so) to points L' and R' (see attached) and I'd try (as an experiment) moving your sweet spot to S'. That would bring you to a quasi-near field situation and then I'd do a lot of listening and even more ruminating before taking any further steps. You will certainly notice a change in sound quality when you draw your curtains as they will damp (but not eliminate) the reflections off the window glass. Drawn curtains will be most effective in damping the midrange and higher frequencies though, with little effect at low frequencies.

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[kckwong723]

Dear Alan,

Thanks for your prompt reply and your drawing demonstrating the direct sound and sound reflection in my listening area.

But can you tell me more about power range requirement of amplifiers for M40 in far-field situation like my case?

As an ex-user of SHL5, I found that power is not a must for SHL5 and many amplifiers can make SHL5 sing. However, it seems that it is not the case for M40.

Thanks

Ken Wong

[A.S.]

I'm sorry but I can't really add much more to my previous detailed observations. The amplifier (and speaker) have no idea about the size of your room, or how far away you sit as they have no way of sensing the environment. They don't have eyes.

The efficiency of a speaker is measured (by convention) at 1m away, for a calibrated input power. As the measuring (or listening) position recedes from the speaker more power will be required for the same measured loudness because the speaker is spraying so much energy across the room that only a small proportion of it reaches the measuring microphone - or your ears. The reflected sounds arrive after the initial direct sound because they have to travel further (to the reflective surface, then from it to your ears) and sound travels very slowly; these reflections screw-up the clean pure direct sound which arrives first at your ears.

Increasing the power into the speaker is just not the correct way to improve fidelity; all that does is blasts more unwanted energy into the room increasing reflections and overall smear. The logical solution is to minimise the power into any speaker and sit as close to it as is considered domestically acceptable as I suggested in my drawing. As I explained, that tips the balance back in favour of the direct sound and away from the 'room sound' and completely sidesteps any issues about amplifier power etc. etc..

Pumping more power into any room - especially a lively, reflective room like yours - is not the answer at all.

That's all I can usefully say.

[pranderos]

Increasing the power into the speaker is just not the correct way to improve fidelity; all that does is blasts more unwanted energy into the room increasing reflections and overall smear. The logical solution is to minimise the power into any speaker and sit as close to it as is considered domestically acceptable as I suggested in my drawing. As I explained, that tips the balance back in favour of the direct sound and away from the 'room sound' and completely sidesteps any issues about amplifier power etc. etc..

Pumping more power into any room - especially a lively, reflective room like yours - is not the answer at all....

Alan;
I've taken these words to heart, and moved my P3ES-2s significantly closer together; a little under 6 feet, or less than 2m apart, relative to a listening distance of about 7 feet, a little over 2m. This has cleaned up the sound and consolidated the soundstage at the same time.

thanks and regards,
-Paul-