Rear Wave

I've seen and heard a lot on these forums about "handling the rear wave," and I've been thinking about getting some acoustic panels myself to put behind my speakers. I just realized today, however, that Martin Logan says on their website about all (almost anyway) of their speakers:

"True dipole speakers, such as electrostatic panels, have long been noted for their near-ideal radiation patterns. They send very little sound to the sides, thereby minimizing side-wall reflections with short arrival times that tend to interfere with perception of the direct sound. Their strong rear radiation, however, produces a generous amount of ambience-enriching later-arriving reflections off the wall behind them."

which makes it sound like they view the rear wave as a "feature" that improves the speaker. Are there any people here who really think the rear wave is better just bouncing off of an untreated wall, or is Martin Logan just trying to make their product description sound as good as it can?

I imagine most people don't have the space for an ideal placement of ML speakers. Plus there are too many variables, such as room dimensions, wall and ceiling materials, source materials, etc. to not have to fiddle with indirect waves produced by the speaker.
Some nice systems I have seen photos of (haven't heard them, so I may be Waaay off base here) have a certain commonality: Speakers way forward of the front wall, even halfway in the room; 2 channel systems have front wall treatments on the front wall center, or thoses with HD displays dampen them; and plenty of other treatments and objects that deal with reflections in an oxymoronic random-controlled kind of way.
Also listener style plays a major factor. Some prefer to mostly sit in the sweet spot and concentrate on the music or equipment , others may be unconcerned with absolute perfection and prefer to use their systems as an accent to their various home life activities.
Again, it's all variables, but at least the Logans give plenty to work with.

I really think that room acoustics are a roll of the dice. I know mathmatics can tell it all but there is not much most people can do anyway. I use auralex Q fuser behind my speakers wich i have seen some reports on this website of causing less than desireable result for right now i like them better than say bare walls and much better than say gik 242's behind them. i have tride that . I have also pulled them way out form the wall with different effects. i seem too like mine right where they are. the panels are 3' from the rear wall.

FISH_MAN said:

I really think that room acoustics are a roll of the dice. I know mathmatics can tell it all but there is not much most people can do anyway. I use auralex Q fuser behind my speakers wich i have seen some reports on this website of causing less than desireable result for right now i like them better than say bare walls and much better than say gik 242's behind them. i have tride that . I have also pulled them way out form the wall with different effects. i seem too like mine right where they are. the panels are 3' from the rear wall.

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Aargggh, don't tell me that! I'm using the 242s behind my speakers right now.

Okay... I'll weigh in on this subject. Let me start by saying that I listen to music (smooth jazz, soft rock) at fairly loud levels. When I measure my SPLs with a Radio Shack digital (C-weighted, fast response), I routinely run about 90db +/-10db. So one could say that I have little issue with 100db+ transients.

I use a set of GIK 242's 4 feet behind each speaker. Overall, I prefer the result over bare walls. The absorbers shrink the depth of the soundstage depth somewhat... But they also take away the nasty comb-filtering harshness that so many rooms suffer from. My listening room is moderately damped and measures 16'x20'x9' high. The result from having the 242's behind the panels is that I can turn up the volume -- basically run the speakers at full acoustic output with virtually no midrange or treble "clangy-ness".

I have experimented with the GIK panels on and off the wall, and can honestly say that they are an big improvement. I like realistic sound levels better than the last degree of z-axis effect. Of course, this is strictly a personal thing. Sometime early next year I plan on having a Michigan/Northwest Ohio gathering at my place and letting other members of this board tell me what they think, for better or worse....

~VDR

Im with the rest of the crew using something behind the speaker.
Every panel I've ever owned has benefitted from something behind
the speaker.

Another big improvement if you can make it work in your room is
to get that big rack of gear out from between the speakers.

That made a tremendous improvement in overall imaging and
depth of the stereo image. All I have between my speakers is
an amp stand on the floor, that's it.

I know that's not convenient for everyone, but it's worth it
if you can do it.

The curved panel definitely helps with the rear wall thing as
opposed to something like a Quad or Magnepan, but the treated
room is always better. Really helps if you can get those speakers
away from the side walls too!

tonepub said:

Really helps if you can get those speakers
away from the side walls too!

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One thing Alvin Gold said in his review of the Spire "The sound is almost as spacious and clear when used hard against a side wall as in clear, open air". Hm - having heard Summits in clear open air I'd be amazed if that was true. Maybe be I'm over analysing here, but I think "almost" means "quite a bit" of difference, really...

Sorry, Alvin!

I'd post the whole review, but there are probably copyright issues I ought to respect.

Just for clarity's sake, are proponents of H/F absorbtion behind the speakers doing so in combination with corner bass traps? I couldn't be certain from reading jonfo's thread, but this would seem to make the most sense.

RUR said:

are proponents of H/F absorbtion behind the speakers doing so in combination with corner bass traps?

Click to expand...

Yes. All domestic size rooms have severe bass problems. No way around that other than bass traps. You'll never get a smallish room perfectly flat with no ringing, so the more bass traps you add, the closer you'll get. At some point - between 2 and 20 traps - it will be "good enough" for most people.

I'm also a fan of absorption on the front wall with dipole speakers. I see the rear radiation as a byproduct of the design versus a design goal. Sometimes people find the improvement jarring, and report not liking the sound of a room after adding absorption panels. I think of a well-treated room as sort of an acquired taste, and once you get used to the increased clarity you'll realize it really is better even if it lost ambience. Which is not a bad thing! Small room ambience is usually not good sounding ambience. In my experience, adding absorption in the right places actually makes a room sound larger, because the space cues embedded in the music are no longer drowned out by the room's own "small sounding" ambience.

--Ethan

VanDaRo said:

Okay... I'll weigh in on this subject. Let me start by saying that I listen to music (smooth jazz, soft rock) at fairly loud levels. When I measure my SPLs with a Radio Shack digital (C-weighted, fast response), I routinely run about 90db +/-10db. So one could say that I have little issue with 100db+ transients.

I use a set of GIK 242's 4 feet behind each speaker. Overall, I prefer the result over bare walls. The absorbers shrink the depth of the soundstage depth somewhat... But they also take away the nasty comb-filtering harshness that so many rooms suffer from. My listening room is moderately damped and measures 16'x20'x9' high. The result from having the 242's behind the panels is that I can turn up the volume -- basically run the speakers at full acoustic output with virtually no midrange or treble "clangy-ness".

I have experimented with the GIK panels on and off the wall, and can honestly say that they are an big improvement. I like realistic sound levels better than the last degree of z-axis effect. Of course, this is strictly a personal thing. Sometime early next year I plan on having a Michigan/Northwest Ohio gathering at my place and letting other members of this board tell me what they think, for better or worse....

~VDR

Click to expand...

Exactly! I just spent the last hour listening with the 242 panels on and off the wall directly behind the speakers and concur with your statements! The differences are especially noticeable at louder levels.

I couldn't agree with Ethan more, especially on the bass traps.

I've NEVER had a bigger improvement for the money than adding
the bass traps to my room.

What the treated room also helps with tremendously is that it
raises the level that you can play your system comfortably. In an
untreated room, things really bounce around leading to a loss in
clarity and ultimately dynamics.

I think once you start experimenting with some well placed room
treatments, you will never want to go back. Ethan makes great
stuff that is moderately priced....

Thanks Jeff.

tonepub said:

What the treated room also helps with tremendously is that it raises the level that you can play your system comfortably.

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Yes, that too. And when music is really blasting it doesn't hurt, and you can talk comfortably to someone next to you and both of you hear each other clearly.

--Ethan

Ethan Winer said:

Thanks Jeff.



Yes, that too. And when music is really blasting it doesn't hurt, and you can talk comfortably to someone next to you and both of you hear each other clearly.

--Ethan

Click to expand...

Even with the volume set to eleven? Wow - I'd need some new, more powerful amps

Sorry - couldn't resist it.

slowGEEZR said:

Aargggh, don't tell me that! I'm using the 242s behind my speakers right now.

Click to expand...

you may like the sound in your room it may be better all rooms are different although I would probably try some diffusers. my room is already pretty dead and to put more dampening material behind the speaker really amputates a lot of what the logans have to offer. you can not see it in the pics I have but there are 242's to the left and right at the first point of side reflections.logans do not have a huge problem with this but they still make a big difference. another option is to place a couple of Qfusers over the 242's that sometimes gives you the best of both worlds! a nice contrasting color can look good
you will diffuse those annoying highs the qfusers do not really go down that low anyway and can still use your absorption

Ethan Winer said:

Yes. All domestic size rooms have severe bass problems. No way around that other than bass traps. .....

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Oh, I've already got your mondo's in the corners. Just ordered two micro's from Jim. :ROFL:

of course, you don't want to over damp your room, that can be bad news too...

User211 said:

Even with the volume set to eleven? Wow - I'd need some new, more powerful amps

Sorry - couldn't resist it.

Click to expand...

One time a friend was over and he brought some old Arnold Schwartzenegger action movie he wanted me to see. The volume was really cranked for maximum excitement, yet we could still talk fairly easily and comfortably. When all early reflections from the side walls (and ceiling) are absorbed, you can localize nearby sound and hear clearly. Not just what's coming from the speakers, but from the seat next to you too.

--Ethan

FISH_MAN said:

you may like the sound in your room it may be better all rooms are different although I would probably try some diffusers. my room is already pretty dead and to put more dampening material behind the speaker really amputates a lot of what the logans have to offer. you can not see it in the pics I have but there are 242's to the left and right at the first point of side reflections.logans do not have a huge problem with this but they still make a big difference. another option is to place a couple of Qfusers over the 242's that sometimes gives you the best of both worlds! a nice contrasting color can look good
you will diffuse those annoying highs the qfusers do not really go down that low anyway and can still use your absorption

Click to expand...

Ok, that makes good sense to me. My room is overly "live" sounding. I think that's why the absorbers work so well. As a matter of fact, now that I've got five absorbers working, I still need to add some more. What I'm finding is what has already been discussed, that the system becomes more enjoyable at elevated volume.

Ethan - I must try some traps at some stage.

However - consider this, all trap people - I am just thinking, not criticising.

I am sitting in my room, playing my guitar. Sound radiates from the back and the front of the guitar, and to some small extent from the sides. It behaves, therefore, a bit like a dipole, or an omni. If I replay a recording of it, surely all I want the transducer to do is behave in the same way as the guitar - the omni will probably get closer to how the guitar behaves than the dipole, in all honestly.

So, by the trap argument, don't I need some traps in my room to make my guitar sound better? Of course not - reflections off the walls are part of the deal. Conversely, adding traps can only make the transducer reproduced guitar sound less like the real one.

Point of note - all my acoustics sound different depending on which room in the house they are played in. The difference is really noticeable. They don't really sound worse or better - just different. Though I can imagine in extreme cases (an empty, uncarpeted house, for instance) echo being a nuisance. So room interaction with real instruments is just as significant as with hi-fi. Which is one reason why recording studios use damping materials I guess. Another reason studios use it is that mics pick up room acoustics much more than the ear seems to do - really noticed that with hi-fi show recordings I have made.

Not an entirely "sound" argument, just a bit of food for thought.

So what do I conclude from the rambling above? Not a lot, really, apart from the fact that damping materials will make a definate difference and are another legimate way of tuning a system, I guess.

Ethan Winer said:

...Sometimes people find the improvement jarring, and report not liking the sound of a room after adding absorption panels. I think of a well-treated room as sort of an acquired taste, and once you get used to the increased clarity you'll realize it really is better even if it lost ambience. Which is not a bad thing! Small room ambience is usually not good sounding ambience. In my experience, adding absorption in the right places actually makes a room sound larger, because the space cues embedded in the music are no longer drowned out by the room's own "small sounding" ambience.

Click to expand...

In my experience, bass traps and absorption panels clearly change the tonality, soundstage, and ambience of the room. In many (? most) cases, the affect is positive, but not necessarily all the time. A lot depends on the room, and especially the listeners preferences (which may deviate from being a "flat" response). While I am certain the addition of bass traps has markedly improved my room, I am still debating whether or not I like the loss of ambience derived from placing acoustic panels behind my Summits. See my description in this earlier post...
http://www.martinloganowners.com/forum/showpost.php?p=78574&postcount=27