Planer/Dipole speakers: FAQ

fishnchips

Banned
May 8, 2011
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To be precise, interference between the frontwave and the backwave reflection will create a comb-filter effect starting at a frequency, the wavelength of which is four times the speaker-to-wall distance, and then progressing upwards octave-wise. For reasonable such distances, this will soon degenerate to randomness as the frequency goes up. Even for low frequencies, this problem is not as grave as it seems, because the later a reflection arrives, the more easily is it rejected psychoacoustically as being unrelated to the main sound perception event - in other words it is classified as "ambience". This is the so called "Haas phenomenon", which has not been studied satisfactorily in the literature.
 

JonFo

Well-Known Member
Jun 11, 2010
322
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Big Canoe, GA
www.jonathanfoulkes.com
I’ve spent the better part of a decade tuning a custom room designed for MartinLogan speakers. And after much research and many measurements, I’ve come to the conclusion that absorption of the rear wave of a large, line-source dipole is the way to go. Many other MartinLogan owners have empirically validated this in their setups as well, as seen in this discussion over in the MartinLogan Owners forum.

One aspect not discussed yet is the fact that dipoles suffer from mid-bass (120 – 350Hz) cancellation due to their typically narrow profile. The right kind of absorption on the wall behind the speakers can improve that a good bit. Still won’t make them into a disco-diva’s favorite speaker, but definitely improves things.

The biggest benefit of absorption is the reduction in comb-filtering and the vast improvement in imaging and intelligibility.

I love electrostats due to their low-distortion and line-source properties; however, the fact that they are dipoles is actually a downside to be mitigated.
The ideal ‘enclosure’ for an electrostat is an infinite baffle. Basically, mount them in a wall between rooms, with the back-wave room containing absorption. That eliminates the rear wave problem, while maintaining the air-mass loading appropriate for the tech. My next custom room will be done that way.
 

fishnchips

Banned
May 8, 2011
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Basically, mount them in a wall between rooms, with the back-wave room containing absorption. That eliminates the rear wave problem
You must then be very, very careful about opening and closing doors and windows, air drafts etc. Such occurrences are liable to make ESLs arc when playing, and destroy membrane tensioning even when not playing.
 

JonFo

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Jun 11, 2010
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Big Canoe, GA
www.jonathanfoulkes.com
You must then be very, very careful about opening and closing doors and windows, air drafts etc. Such occurrences are liable to make ESLs arc when playing, and destroy membrane tensioning even when not playing.

I think you misunderstand, I plan to build a totally custom room-within-a-room setup, where the electrostats have their own (non-accessible) dedicated infinite baffle cavity, which will be treated and prepped just for this purpose. No doors anywhere.
 

fishnchips

Banned
May 8, 2011
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Still, large changes in pressure within the listening room (I presume this will at least have a door of sorts) will prove hazardous to the ESL membranes. Since you are going to such trouble and expense, it's probably best to make sure that the listening room door is a sliding one, with sizeable air leaks around it.
 

TitaniumTroy

Well-Known Member
Jan 11, 2011
136
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925
South Bend IN
Baffles/Wings

Has anyone here tried using side baffles/wings on their planer speakers? I have done some on my own, it helped the lower the bass response, and improved the center image to point I don't use my center channel anymore. Currently running baffles on the inner edge with tweets in. They are also folded back at angle kind of like _/ \_ for each speaker. Next I want to try a baffle on both sides of each MG3.6 like so \_/ \_/ .

I like the infinite baffle concept but, do not have the funds to tackle that scale of a project right now.
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
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I have heard Maggies and some 'stats, plus of course the old Infinity IRS, with wings and with mixed results. Helped some, did virtually nothing to others, and hurt a few. I have had much better success with room treatment, though building a set of wings is cheaper... I have known folk who swear by them, but I think it is very room and placement sensitive (naturally).
 
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bwraudio

New Member
Jan 24, 2011
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Planar/Dipole speaker placement and acoustics

IMG_1181..jpg I have 50 years of experience with acoustics and audio and have
had 4 different listening rooms. I owned many types of speakers,
from Acoustic Research, Bose, Klipschorns, Electrovoice, JBL Lansing,
but Planar/Dipole speakers are just plain realistic. It takes a large
room for Planar/Dipole speakers as well as proper acoustics. I have had most of the Magneplanar speakers, some Martin Logan
electrostatics and this drawing shows what it takes to get state of the
art sound. Placing dipoles requires a very large distance from all
surfaces and in addition many bass traps, mid bass traps. The
following drawing shows what I have learned about the requirements
for these speakers. Placing these dipoles on the long wall, when done
right provides a enormous sound-stage, and one feels like there in the
hall (venue).
 

hifiaudio2

New Member
Sep 3, 2011
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After reading numerous threads and articles, many by Ethan, I have discovered that I dont have my listening seat at the proper distance from the Martin Logan CLX speakers. I want to try forming the equilateral triangle that Ethan suggests with the point converging just behind my head. I think I have been sitting a foot and a half to two feet too far back. I have 106" between the inside sides of each speaker. My question is: What distance between the speakers do I use for the distance to my head? The far inside side of each panel? Or the middle of each panel?
 

A.wayne

New Member
Jan 14, 2011
1,289
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Front Row Center
Hello,

I'm also in full support of not damping the front wall ( behind speakers) when it comes to dipoles, you will end up with a dead sounding speaker, diffusing works best here IMO , with any absorbtion being done to control reflections along the side walls at seat location( if listening near field.) or at the listening position...( far field)


regards,
 

wineslob

New Member
Aug 5, 2010
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Hello,

I'm also in full support of not damping the front wall ( behind speakers) when it comes to dipoles, you will end up with a dead sounding speaker, diffusing works best here IMO , with any absorbtion being done to control reflections along the side walls at seat location( if listening near field.) or at the listening position...( far field)


regards,


I agree with this. Having owned Apogees for 6 years I can assure you that the front wall is VERY important. Small changes in speaker position, 1/4", can make or break the soundstage, as can listening position.
When I got the position "right" (per the Golden Ratio) albums would go from very nice, to, WTH, is there something/someone in the garage???(one sidewall is the back of my garage). Yes, the soundstage had no boundries. I could hear off stage noises that would not show up when the setup was not perfect. It was the "in the recording" not "looking at the recording from the outside" effect. At times, however, it could be very distracting, thinking someone is rummaging around in another room. :D
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
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Monument, CO
The advantage of damping the front wall is that placement is much less critical and imaging more precise. The disadvantage, as stated above, is the speakers lose some of their "life". My front wall is heavily damped, for various reasons.
 

RussellD

New Member
Oct 12, 2010
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1
Victoria BC
The advantage of damping the front wall is that placement is much less critical and imaging more precise. The disadvantage, as stated above, is the speakers lose some of their "life". My front wall is heavily damped, for various reasons.

I believe this is the point being missed by so many in this sort of discussion is that the speaker should have no "life". The life should be in the recording.

The ideal listening room, allowing for the inevitable compromises forced by the practicalities of life itself, has absorption to deal with early reflections, flutter echo, and the inevitable bass standing waves. The typical error is inadequate bass damping relative to mid and highs, adding to the typical box speaker errors of over-resonant bass and bass-heavy room response due to directional mids and highs and omni bass and leading to a plodding, inarticulate bass range as heard in the room.
There are few commercial speakers that deal with the directionality in the bass range - Gradient and Geithain being two; the latter being an obscure German studio monitor maker.

In my old mastering room the front wall consisted almost entirely of a wide range trap, the side walls were convex, curving inward with a 14 foot radius curve, the front 2/3rds was symmetrical and the rear 1/3 was irregular and diffusive. It worked so well that the bass sounded essentially the same anywhere in the room - even if tested with a tone generator at any fixed frequency in the bass range.
 

Grainger49

New Member
May 11, 2010
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Knoxville, TN
Bruce, in re: Martin Logan planar dipoles, at least, Ethan has consistently advised owners to fully absorb the backwave, and many owners have followed that advice with excellent results. His assertion is that all of the information from the recording is contained within the front wave and that the back wave serves only to "confuse" the intended soundfield. Essentially, the unabsorbed backwave adds a form of artificial ambience while, as a result of comb filtering, reducing image clarity. . . .

I can see that the ML might really confuse the directional cues because of the curved surface. I think they are an ingenious design. My experience of 15 years with Servo-Static speakers was to toe them in for more direct sound to the listener. That also allowed me to use the back wave reflected off the wall behind them, then the side wall to open up the soundstage. I had to adjust the distance from the R/L panels to the back wall to get what I was seeking.

As always this changes drastically from speaker to speaker, even within the small category of electrostatic speakers.
 

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