[MGbert]

Hello and Greetings:

No, I'm not selling anything!  This is my first post here, but it is a
follow-up from earlier postings at that Asylum place over there, where I claimed the right to name the idea.  It is
a partial cross-post, but since I have some follow-up ideas about this
idea that I figured would be appropriate for this forum, I decided to
make it my initial foray here.  Besides, if I say so myself the basic
idea could be really helpful to other Planar owners...

I have my "Gunned" MMGs in a 11 foot by 11 foot "listening room" carved
out of an 11 foot wide by 20 foot long shed, with a barn-like ceiling (8
foot-4 inch average height, peak height 9 foot plus), insulated and
climate controlled. Because it also has to act as storage for several
pieces of furniture and other stuff, I could never make the full
footprint symmetric enough for Maggies to throw a reasonable soundstage.
The non-exterior "walls" consist of my 6 foot tall vinyl LP Album and CD
shelving to make a symmetric listening space within the shed, keeping
spaces on the back sides of the media shelving for storing the most
non-symmetric stuff. The bad news of course is that the listening space
becomes a 11 foot X 11 foot square! 

I settled on 3 facts right away: 1) by necessity, this will be nearfield
listening, which the Gunn mod makes really easy to live with due to his
crossover mod; 2) since getting the recommended 10 millisecond delay in
first reflections would be impossible any other way, the listening seat
(LS) would be right up against the shelving along the back wall. Others
have reported no serious problems sitting close to the rear wall, which
I attribute to evolution preparing our ears to deal with rear
reflections.  So it should have fewer audio consequences compared to
early reflections off the front or side walls. 3) I also decided that,
in spite of the tipped back nature of the Gunn frames, the MMGs still
sound their best tipped nearly vertical with the drivers centered at ear
level. So they are sitting on concrete cinderblocks with the rear spikes
shimmed to make the panels very nearly vertical with only a slight
backward tilt to get the center lined up to ear level.

Fast forward through many months and MANY attempts with the Rooze, Hong
Kong/Limage, Cardas, Jim Smith's "Get Better Sound", Beveridge (a.k.a.
sideways a.k.a. Stereo Unlimited (Walnut Creek)), Ambiophonics, and
random drunkard's walk placement experiments. I finally stumbled on
a placement about 50 inches from the front wall and 17 inches from the
side shelves to the outer speaker edge which had fairly even frequency
response properties*.  With a 45 degree toe-in so the direct sound
crossed about 2 feet in front of me, there was some real depth to an
amazingly wide soundstage. So far so good, but even with tweeters on the
inside the phantom center sounded like cardboard (how's that for an
audiophile descriptor?) compared to a monophonic signal from one speaker
only. I came to realize that some serious comb filtering due to the
first reflection being only about 7 milliseconds after the direct sound
was the likely culprit.

I suspect this phenomenon is the "gorilla in the room" for many folks
here, especially those with small listening rooms.  This business of a
monophonic "phantom center" signal from 2 speakers sounding different
(wooly? Like cardboard? The proper term escapes me) compared to the
sound of one speaker alone seems like an unfortunate consequence of
stereophony, to be put up with unless you "upgrade" to multi-channel
sound.  Well, I humbly submit that, at least in my room I beat it with a
$20 USD investment.  Perhaps you can too.   

The brainstorm: what if you could delay (not absorb or diffuse)
rear-wave reflections from reaching the LS by use of a baffle? I had
some wood paneling pieces around, and I took 2 designed for fake
wainscoting (48 inches wide by 31 inches high), turned them on their
side so they were now 48 inches high by 31 inches long and angled them
out from the front wall into the room in such a way that the first
reflection from the front wall is "trapped" behind the paneling, hence
the name "First Reflection Traps" (FRTs). Not absorbed; the point is to
have the first reflection bounce around the front and sides to lengthen
the time it takes to reach the listening position. I settled on the
position by placing a mirror at the first reflection point, and ensuring
the paneling blocked the speaker from view. Since I had a small (6 inch
deep X 20 inch wide X 6 foot high) bookcase centered on the wall, it
acted as a convenient brace and spacer for the panels. Like the MMGs,
the paneling is also sitting on cinder blocks to elevate them in line
with the MMGs. The result? Spacious sound, by my calculations the first
reflection went from about 7 milliseconds to at least 16 milliseconds
after the direct sound reaches the listening position**.  The phantom
center now sounds very nearly identical to the sound of one speaker
alone. And the depth of the soundstage was not harmed; in fact, it may
have improved! Here is the floor plan:










and a photo taken from the LS:









I think the 45 degree angle of the MMGs to the side wall is a key
element to this strategy, because it allows placement near the side wall
(good for bass reinforcement and for getting as wide a stereo soundstage
possible in a narrow room) while keeping the first reflections from
those side walls behind the speaker to bounce to the front wall, where
the FRTs as well as the bulk of the speaker can manage them by
lengthening their arrival time to the LS.

Since a lot of folks place a big TV between Maggies, some of the
positives they provide the sound could be some degree of first
reflection trapping similar to my FRTs. Especially the old-school big
TVs which taper towards a point in back behind the screen. It seems to
follow that, if one uses these FRTs that one could put ANYTHING centered
between them without affecting the sound, as long as it didn't stick out
further from the front wall than the forward edge of the FRT. Also, the
FRT probably shouldn't extend beyond the plane of the Maggies. I could
imagine a variant which even has some WAF, if they are made to look like
attractive, self-standing oriental screens behind the TV perhaps.  As
long as the backs of the screens are acoustically reflective, the front
could be anything attractive, like rice paper behind a wood latticework.
Since mine are in a shed which my significant other refuses to enter,
WAF is academic in my case.

OK, what does it sound like?  Unfortunately I can't write in Audiophilia
as well as I can read it.  All I can say is that music sounds like I'm
sitting in the second row of an intimate theater, with a stereo spread
approaching that of headphones, except for being totally outside the
head vice in-the-head like headphone listening typically is. Drums in
particular sound present in the room, although a lot of that came from
the Gunn mod. The excitement factor is through the roof, and I can
listen for hours without ear fatigue. I also suspect some here would
consider me a heretic for using a Behringer EQ as my DAC. All I can say
is that, judiciously used, it just seems to work without screwing up the
sound, like the Gunn mod does on my MMGs. OK, maybe the EQ function
introduces a little congestion to the sound, but that is more than made
up for by the evenness of the frequency response, meaning ALL the notes
get equal emphasis.  Besides, when listening to rock the congestion
actually adds to the "slam" and sounds totally normal!  Point is, I've
gotten the sound of my relatively inexpensive system good enough for me
to put it up against many multi-buck systems.  I'm still grinning. 


MG-bert

*I use a Behringer DEQ2496 digital equalizer for both room EQ and my
DAC, and by using pink noise and a reference mic was able to get the
frequency response flat (+/- 2.5 dB) from 45 Hz to 16000 Hz with none of
the relevant frequency bands adjusted more than +/- 5 dB. Compared to
other
positionings in my shed, which required perhaps 8 dB settings on some
frequency bands and still were worse than +/- 2.5 dB of flat, that is
phenomenal!

**"Calculations" meaning drawing sound trajectories on graph paper and
measuring them. True, the second reflection may be hitting me now
before the old first reflection does due to the FRTs, but the bottom
line is that the phantom center sound is now powerful and clean.

[SteveFord]

My only suggestion would be to invest in some sheetrock to attract the babes to your uptown Sin Den (so to speak).  Insulation will only attract Thunderbrick's foul birdie.
Has anyone else given this a shot? 

[josh358]

I haven't tried it, but as I said back on the asylum, I think it's one of the most interesting experiments I've seen and hope eventually to play with it myself. The theory is sound, in fact, studio control rooms are typically designed with a "reflection free zone" consisting of facets that keep early (<10 ms) reflections from reaching the listening area. The facet approach works with soffit-mounted monitors, but dipoles require a different approach. The ideal? To delay most early reflections so they arrive no sooner than these:



A formidable task with a much smaller room.

In general, with dipoles, you have:

Floor and ceiling reflections -- not a problem in a full height line source.

Front wall reflection -- speakers need to be at least 15' out, that is, as far as the players are from the rear wall of the shell. Diffusion can help.

Side walls -- you can null the proximate side wall with the dipole null which helps but in a small room even that isn't enough. Rooze comes closer than anything I know for the side walls, it effectively increases the acoustical size of the room. But it doesn't work in every room. Diffusion can help.

Rear wall -- hopeless, unless you live in the Taj Mahal. Control rooms typically use diffusion on this, it's probably the best approach unless you're sitting against it, in which case you need absorption.

Anything that helps circumvent these limitations is welcome.

[medium jim]

I find well placed clutter works.  Not trying to be funny, as it breaks up the 1st order reflections.

Jim

[Rclark]

As a side note, those are really beautiful MMG's. I wanted a knotty type of wood at first, knotty pine, but PG talked me out of it, and I certainly like my build.

Anyway, great convo, carry on.

[J-Pak]

Great read, thanks for sharing mg-bert

[Rclark]

 This is one thing I have not tried, the extreme angle, direct facing. I have excellent sound in the position I have taped out now, excellent soundstage, etc (used Cardas planar calculator for a start point, but didn't end up too far from it. Very moderate toe in).

 I'm about to give this a listen here.

[Rclark]

oh wow! That is niiice! I just tried a crude approximation of that, I'll place them with the measuring tape later.. Not sure why I didn't try it like that before.

 That's quite something!

[Rclark]

I want to thank you for posting this, I was actually able to lock in an even stronger center image, and some of my benchmark recordings proved this out. I learned that I'm not even close to finished to dialing in the perfect sound in this room. Very much looking forward to the measurement/treatment stage, but I'm about go over over some very expensive speedbumps (amps, pre.. reclocker), but your arrangement works very well in my room.

 Better than what I had before.  Thank you.

[Rclark]

(can't edit so have to post anew)

 Getting Magnepans right seems very much like focusing a pair of lenses. It will be fun to one day soon have software that just reads our entire room and everything in it (camera based), and is able to give us the exact location we need to be for perfect imaging. With Magnepans it's a game of inches and sometimes all you want is to just have it right the first time, not a voyage of mistakes.

[MGbert]

I want to thank you for posting this, I was actually able to lock in an even stronger center image, and some of my benchmark recordings proved this out. I learned that I'm not even close to finished to dialing in the perfect sound in this room. Very much looking forward to the measurement/treatment stage, but I'm about go over over some very expensive speedbumps (amps, pre.. reclocker), but your arrangement works very well in my room.

 Better than what I had before.  Thank you.

De nada!  And you are so right that placement is critical - my equipment is actually fairly non-SOTA (except for the Gunned MMGs, of course), but the room placement makes such a huge difference over hardware that it isn't funny.  Best thing is that doing this is almost free!

And btw, your Gunned MMGs are the real beauty queens; I purposefully had PG make mine fairly plain, since I wanted to minimize the cost and was doing it for the acoustics.  I got what I asked for and am not unhappy; but you got true works of art!

[MGbert]

I haven't tried it, but as I said back on the asylum, I think it's one of the most interesting experiments I've seen and hope eventually to play with it myself. The theory is sound, in fact, studio control rooms are typically designed with a "reflection free zone" consisting of facets that keep early (<10 ms) reflections from reaching the listening area. The facet approach works with soffit-mounted monitors, but dipoles require a different approach. The ideal? To delay most early reflections so they arrive no sooner than these:



A formidable task with a much smaller room.

In general, with dipoles, you have:

Floor and ceiling reflections -- not a problem in a full height line source.

Front wall reflection -- speakers need to be at least 15' out, that is, as far as the players are from the rear wall of the shell. Diffusion can help.

Side walls -- you can null the proximate side wall with the dipole null which helps but in a small room even that isn't enough. Rooze comes closer than anything I know for the side walls, it effectively increases the acoustical size of the room. But it doesn't work in every room. Diffusion can help.

Rear wall -- hopeless, unless you live in the Taj Mahal. Control rooms typically use diffusion on this, it's probably the best approach unless you're sitting against it, in which case you need absorption.

Anything that helps circumvent these limitations is welcome.

So what are you waiting for?     The rear wall is NOT hopeless, btw.  I came up with an improvement which actually adresses both the rear wall and side wall issues, and is a marked improvement over the initial FRT arrangement, which itself was an improvement.  It's also impossible to ascribe any WAF to it.  Basically, you lean a 6 foot high, 4 foot long piece of luann paneling on the outer edge of the speakers, angled so you just see the back of the panel from the listening seat.  I know, I need to provide another sketch to make this clear, and I will in a few days.  Looks ugly, sounds great.  Never was there a better excuse for listening with eyes closed!

[MGbert]

I find well placed clutter works.  Not trying to be funny, as it breaks up the 1st order reflections.

Jim

Now if only I could convince my wife of the acoustic benefits...

[medium jim]

Now if only I could convince my wife of the acoustic benefits...

 

Jim

[josh358]

So what are you waiting for?     The rear wall is NOT hopeless, btw.  I came up with an improvement which actually adresses both the rear wall and side wall issues, and is a marked improvement over the initial FRT arrangement, which itself was an improvement.  It's also impossible to ascribe any WAF to it.  Basically, you lean a 6 foot high, 4 foot long piece of luann paneling on the outer edge of the speakers, angled so you just see the back of the panel from the listening seat.  I know, I need to provide another sketch to make this clear, and I will in a few days.  Looks ugly, sounds great.  Never was there a better excuse for listening with eyes closed!

Actually, I don't think I could do this with my new setup, Tympani IVa's in the split configuration (woofer panels 1/2 wavelength behind the mid-tweeter panel, against the outside walls). It's unexplored territory for me, I used to have Tympani 1-D's but those you couldn't split. I imagine if you did, you'd want to do it for the mid-tweeter panels but I'm not even sure that would work, since low frequencies have a major effect on spatial sense.

My rear wall is going to have to have absorption on it, because my room is too small -- I have to sit almost against it. This would solve the early reflection problem, unfortunately, it would do so by eliminating all reflections, and you really do want reflections back there.

However, I have something else interesting to try. On my desktop, my computer speakers are behind my monitor and I realized at some point that I could position them so the monitor acts as an ambiophonics barrier to minimize interaural crosstalk. Now I have a large monitor for my listening room -- the idea is to do most of my computer work in there where the big speakers are -- and I'm going to see if I can position it to get crosstalk cancellation. Whether it works I think will depend on whether I can get it close enough to minimize diffraction, while still maintaining the right angle -- I didn't buy the new monitor with this in mind, thought of the idea later.

Actually, I'm not sure how the setup is going to work at all in my room. I was having trouble with it, with the speakers where I'd like them to be there's a fireplace mantle on the front wall that screws up the sound. The only thing I've been able to come up with is to put barriers on either side. Easy enough to do, but not very functional since my equipment closet would be behind one of them.

[Rclark]

Please keep this coming because I'm learning something new here and the way my speakers are sounding now, I think I'm inclined to try out all your methods.

And thanks for the compliment, that's very kind of you. I almost wish I had two sets, one like yours as well. Love the look of a knotty wood! It took me forever to pick, because just like you I was in it merely for the sonics.

Anyway, please carry on, great thread on the mysteries of planar placement.

[medium jim]

Please keep this coming because I'm learning something new here and the way my speakers are sounding now, I think I'm inclined to try out all your methods.

And thanks for the compliment, that's very kind of you. I almost wish I had two sets, one like yours as well. Love the look of a knotty wood! It took me forever to pick, because just like you I was in it merely for the sonics.

Anyway, please carry on, great thread on the mysteries of planar placement.

RClark are you telling us that you never fiddled endlessly with the placement and or room treatments to get them in their best position? 

The OP has some interesting things to bring to the table, kudo's.  But each room/environment is unique and there is no perfect formula, only a good starting point, then the fun begins with an inch here, less toe-in, or more...sit a little lower or higher, put something behind them, in front of them, or on the side of them. 

The joy is when you finally do get them right and the sweet spot becomes bigger than a postage stamp, maybe even big enough for 2 people on axis and if you are really lucky 3. 

Why in the world do we love them so much, the big ones need world class amplification, then we need to spend countless hours getting them in their sweet spots....Magnepan lover's are Masochists

Jim

[Davey]

The diagram shows just a single ray emanating from the rear of the speaker (at a fairly extreme angle.)  What about the infinite number of other sound rays at all other angles?  How are you blocking first-reflection on those?

Cheers,

Dave.

[josh358]

At higher frequencies, ray tracing is a good acoustical approximation. At low frequencies, not so much. But since the reflections arriving within the first 10 ms are the most problematic, the main imaging impairment will be caused by the indicated first reflection from the front wall, and the first reflection on the proximate side wall, which seems here to be in the dipole null. Floor and ceiling reflections aren't a problem with full height line sources. The main potential problem I can see here is not with first reflections, but second reflections, e.g., the corner bounce reflections, which also have a short path length.

[Rclark]

No Jim I.messed with them a lot. You should see all the spots taped out. I had just never tried this specific orientation, with something blocking.

Remember I've only had these seven months!