Ron's Speaker, Turntable, Power and Room Treatment Upgrades

[kach22i]

...........

Ron and I both like panels and I routinely see most people over damp a room with panel speakers and that kills their purpose entirely. Makes me wonder why they didn't buy box speakers in the first place.

I agree with you guys.

Had this discussion many times in the Martin Logan Owner's forum, but the guys killing their front wall with acoustic treatment had the charts, and the charts just had to be right.

Guess they didn't trust their ears.

Hola, as Roberto used to say.

 

[PeterA]

Had this discussion many times in the Martin Logan Owner's forum, but the guys killing their front wall with acoustic treatment had the charts, and the charts just had to be right.

I don't have much experience with panels. Do they need walls behind them or will lots of open space work? I would think overdamping front walls would have a similar effect to open space.

 

[Ron Resnick]

I don't have much experience with panels. Do they need walls behind them or will lots of open space work? I would think overdamping front walls would have a similar effect to open space.

Placing the panels five feet to nine feet away from the front wall allows the right amount of time delay for the reflection off the front wall to merge with the direct wave and provide the spaciousness and open-ness panel people like.

Different people have different views, but I have never subscribed to absorbing the back wave.

 

[Zero000]

I resisted front wall absorption for years of ML and Apogee use.

Then I tried it and was pretty surprised. Better with front wall absorption.

New room as of Thursday with a lot more space. Be interesting if I think the same in there.

 

[kach22i]

Placing the panels five feet to nine feet away from the front wall allows the right amount of time delay for the reflection off the front wall to merge with the direct wave and provide the spaciousness and open-ness panel people like.

Different people have different views, but I have never subscribed to absorbing the back wave.

You must be talking big panels and big rooms, but you are promoting the right idea, no disagreement there.

I resisted front wall absorption for years of ML and Apogee use.

Then I tried it and was pretty surprised. Better with front wall absorption.

New room as of Thursday with a lot more space. Be interesting if I think the same in there.

I'm in a new space now too, so many things are different, but mostly in a good way.

I'm loving the concrete floor (with carpet), taking the sprung wood floor out of the equation that would muck up the bass and resonate the floor diaphragm is a thing of the past.

 

[PeterA]

I’m still wondering about open space behind panel speakers. Is this a good idea or do they need wall space for reinforcement?

 

[pjwd]

I don't have much experience with panels. Do they need walls behind them or will lots of open space work? I would think overdamping front walls would have a similar effect to open space.

Peter - if you look at linkwitz site he recommends( for dipoles) a minimum of 1m from speaker to wall behind to get the 6ms time delay between direct and reflections and of course more would be better
The problem with absorption is that it will be very frequency dependant and the reflected wave will not correlate with the direct - so the reverberant field does not exactly support the direct sound - similarly diffusion will almost certainly change the phase of reflected sound so treatment of wall behind is complicated and looking at all the angles of reflection is important and is addressed on the site
http://www.linkwitzlab.com/listening_room.htm

the James Heddle paper linked is well worth the read ( an acoustic engineer I have worked with quite a bit ) glide over the maths

cheers

Phil

 

[ack]

Placing the panels five feet to nine feet away from the front wall allows the right amount of time delay for the reflection off the front wall to merge with the direct wave and provide the spaciousness and open-ness panel people like.

Different people have different views, but I have never subscribed to absorbing the back wave.

I wholeheartedly agree here. I let my speakers radiate deep in the back.

 

[PeterA]

Thank you Phil. What about having no wall behind the panel speakers, just open space?

 

[Duke LeJeune]

I’m still wondering about open space behind panel speakers. Is this a good idea or do they need wall space for reinforcement?

My understanding is that the backwave is beneficial IF it arrives after a fairly long time delay and IF it is spectrally correct (has approximately the same spectral balance as the front wave). I can explain why if you would like.

Imo a good "target" for time delay on the backwave is about 10 milliseconds, which corresponds with having the panels about five feet our from the wall (sound travels about little over one foot per millisecond). A longer time delay (greater distance) is generally better. Ime less than 3 feet and imo it starts to make sense to diffuse or re-direct (via reflection) or absorb the backwave. That 3 feet figure is consistent with Linkwitz's recommendation of 6 milliseconds of delay; I got the 5 feet figure from years of having SoundLabs in my living room/slash/showroom, and it is consistent with Earl Geddes' recommendation of avoiding reflections within the first 10 milliseconds.

If you're going to absorb the backwave, then imo the ideal would be to absorb all frequencies equally, which is easier said than done. Something like foam will absorb short wavelengths much more effectively than longer ones, so while the reflections will be weaker their spectral balance will be wrong.

Imo that spectrally-correct backwave energy is a major contributor to what fullrange dipole speakers do well, assuming it arrives after a decent amount of time delay. So personally I would not be in favor of a totally open space behind the dipoles into which you lose the backwave energy completely.

 

[ack]

My understanding is that the backwave is beneficial IF it arrives after a fairly long time delay and IF it is spectrally correct (has approximately the same spectral balance as the front wave). I can explain why if you would like.

Imo a good "target" for time delay on the backwave is about 10 milliseconds, which corresponds with having the panels about five feet our from the wall (sound travels about little over one foot per millisecond). A longer time delay (greater distance) is generally better. Ime less than 3 feet and imo it starts to make sense to diffuse or re-direct (via reflection) or absorb the backwave. That 3 feet figure is consistent with Linkwitz's recommendation of 6 milliseconds of delay; I got the 5 feet figure from years of having SoundLabs in my living room/slash/showroom, and it is consistent with Earl Geddes' recommendation of avoiding reflections within the first 10 milliseconds.

If you're going to absorb the backwave, then imo the ideal would be to absorb all frequencies equally, which is easier said than done. Something like foam will absorb short wavelengths much more effectively than longer ones, so while the reflections will be weaker their spectral balance will be wrong.

Imo that spectrally-correct backwave energy is a major contributor to what fullrange dipole speakers do well, assuming it arrives after a decent amount of time delay.

That's where I come from as well

 

[pjwd]

Thank you Phil. What about having no wall behind the panel speakers, just open space?

well technically I don't think it is needed for the output but a nice well delayed well behaved reverberant field is needed for any room ( if you have listened to a recording mane in an anechoic chamber it is pretty clear) and I believe you should locate your speakers so first reflections from rear or sidewalls are delayed as much as possible ( Duke lejeune has been pointing this out in his many excellent posts) so theoretically you would use your room geometry to optimise and equalise these distances as much as possible
My view is that longer first reflection delays from side walls than rear are subjectively better so favour locating speakers on the long wall ....but I don't have any science for that

Phil

 

[pjwd]

Imo that spectrally-correct backwave energy is a major contributor to what fullrange dipole speakers do well

Duke - I just mentioned your name and there you were - thanks for all your posts - I really enjoy them
However I am not certain how much support you need directly from the rear wall - you design crossovers for dipoles by measuring in free space ( as much as possible ) so the output is technically not reliant on a rear reflection - the big issue is a correlated , delayed reverberant field which is provided by all surfaces and the reflections from rear wall are just a part of this

Phil

 

[Ron Resnick]

I’m still wondering about open space behind panel speakers. Is this a good idea or do they need wall space for reinforcement?

The front wall space is not for low frequency reinforcement; it is to capture and hear the full-range back wave reflecting off the front wall.

 

[Folsom]

I'm going to simplify what Duke said - in a manner of speaking.

It all depends on distances. It's not universal.

 

[Ron Resnick]

. . . What about having no wall behind the panel speakers, just open space?

If that is what someone wants, but I wouldn't know why . . . because then one forfeits the sonic spaciousness afforded by the backwave -- which many planar dipole owners consider to be the unique selling point of planar dipoles. The sonic result would be essentially the same as completely absorbing the backwave.

 

[Lagonda]

The front wall space is not for low frequency reinforcement; it is to capture and hear the full-range back wave reflecting off the front wall.

Your experience is maybe with hybrid electrostatic speakers. A full-range will
often need the back front wall for bass reinforcement.

 

[Ron Resnick]

Your experience is maybe with hybrid electrostatic speakers. A full-range will
often need the back front wall for bass reinforcement.

My first loudspeaker was Magnepan MG-IIIAs.

Yes -- solving the equation for bass reinforcement and for the backwave cannot be accomplished at the same time.

 

[Lagonda]

My first loudspeaker was Magnepan MG-IIIAs.

Yes -- solving the equation for bass reinforcement and for the backwave cannot be accomplished at the same time.

My ML CLS can play very articulate bass when placed at the right distance from
the front wall, not the deepest notes, but always better without subs.

 

[Folsom]

Thank you Phil. What about having no wall behind the panel speakers, just open space?

Well, I can tell you the one time I took some OB 15" coaxial speakers outside for a memorial, and played a sinatra song on them... Everyone on this forum would be envious of that sound. I've thought about doing it again some day, an outside gathering for music. It seems almost silly but you can't get that indoors, not in any way whatsoever.

But if you're inside and just have a LOT of space behind them, like another big room, well the sound is just very delayed, very toned down, and won't add to the 3D effect in an appreciable manner.