[Tyson]

Put up some 2 inch thick compressed fiberglass on the corners/walls behind my speakers (they are angled in 45 degrees).  Between that absorption and the dispersion from the hexacomb window treatments, the room is starting to sound pretty good. 

[nickd]

Ebag, that is a sweet room my layout is similar at 14' 6 wide by 21' long by 9' high. I have a heavy (padded and backed) velvet curtain behind both speakers and across the top of my screen. The screen is acoustically transparent and could probably use some diffusion between the 3 in walls behind it.

I have been thinking of making some diffusers out of bannister posts (3-5 ea) placed between a top and bottom plate, for installation behind my Super V's (2 weeks form completion) they combine round and square edges and I think they may be OK looking if painted black.

Sorry to hear about the tube amp. They sound magical but man can they be a P.I.T.A. to live with from time to time.

I do plan to join you on the SET journey when I find the right amp at a good price.

[ebag4]

Ebag, that is a sweet room my layout is similar at 14' 6 wide by 21' long by 9' high. I have a heavy (padded and backed) velvet curtain behind both speakers and across the top of my screen. The screen is acoustically transparent and could probably use some diffusion between the 3 in walls behind it.

I have been thinking of making some diffusers out of bannister posts (3-5 ea) placed between a top and bottom plate, for installation behind my Super V's (2 weeks form completion) they combine round and square edges and I think they may be OK looking if painted black.

Sorry to hear about the tube amp. They sound magical but man can they be a P.I.T.A. to live with from time to time.

I do plan to join you on the SET journey when I find the right amp at a good price.

Hey Nickd,
Just to clarify, that sweet room belongs to Perry, he has built it recently, unfortunately my room is much smaller.  I am however the person running V1s with a 2a3 SET amp, I believe Perry's tube amp is in need of repair.

Best,
Ed

[nickd]

must have been late last night

got my V owners confused

what type of 2A3 amp did you settle on Ed?

[rollo]

  If one cannot have at least 10 feet to the rear wall difussion is warranted. Recently added [5] 2' x4' wood RPG clones at the rear wall. Two in the ceter side by side with one atop. Then one directly behing each speaker also at the rear wall.
   Neve have iIhad such a dissappearing act of the Pipedreams. The soundstage just emerges from the room. Depth is uncanny. The rear wall is damped. worked for us. anyways.


charles

[ebag4]

must have been late last night

got my V owners confused

what type of 2A3 amp did you settle on Ed?

I built the Bottlehead Stereomour, here is my build thread if you are interested:

http://www.audiocircle.com/index.php?topic=94743.0

Best,
Ed

[BPT]

You can also DIY something like the Soundlab Sallie http://www.soundlab-speakers.com/accessories.htm
Chris H.

[JohnR]

Hey now that's an interesting idea.

[JohnR]

----begin excerpt----
Dipoles radiate equally forwards and backwards. This makes placement of the dipole relative to the front wall (behind the speakers) particularly critical. ~15ft path length difference is required to reduce the level of reflection from the front wall to -15dB (our standard for the level of reflections relative to the direct sound). This calculation is correct for a point source. For a true line source (floor-to-ceiling) the distance is much larger since SPL falls off 3dB per doubling of distance as opposed to 6dB for a point source. 15ft path length difference requires the dipoles to be placed around 7-8ft from the front wall, which in most living situations is not practicable. Placing a dipole closer to the wall requires that wall to be acoustically treated. The difficulty is that this selfsame acoustical treatment can distort the dipole radiation pattern resulting in unwanted changes elsewhere.

I think it would be helpful to distinguish the different frequency ranges. I'd agree it's far from axiomatic that dipoles have reduced room interaction and that overall it's a different mindset/approach.

[poseidonsvoice]

You can also DIY something like the Soundlab Sallie http://www.soundlab-speakers.com/accessories.htm
Chris H.

Chris that's pretty cool, and especially relevant behind OB speakers.  But I would first try something a little more accessible and cheaper (especially if you are a non-diyer). Get 4 GIK Acoustics Grid Fusors, line them up on a flat panel, like the Sound Lab Sallie! About 1/2 the price (and maybe better performance but measurements would have to be made). If you are purely into DIY however, you may be able to go even cheaper.

Anand.

[Pez]

You can also DIY something like the Soundlab Sallie http://www.soundlab-speakers.com/accessories.htm
Chris H.

I don't know... Would my foam wedges on a stand sound as good as these $1000 a pair foam wedges on a stand?
 

[driguy]

I think you can sense a pattern with a lot of responses that leads one in the direction of getting your speakers away from the wall. You have done this already but as an experiment you may want to go out a bit further if you can. That corner between the console and the wall is not good and is to be minimized. Also, as you can see in PDR's photo having the speakers a little more parallel may help as well. It helps my soundstage and frequency response both. A more parallel setup will also allow having the speakers closer together. Normally this would cause a more coalesced sound that sucks but in my setup it helps. Getting the speakers closer together moves them away from the walls giving you a better sound IMO. Basically, moving the speakers away from all of the walls helps.
Treating the first reflection points BEHIND the speakers with diffusers will help as well and it will give you the sense of having a much larger room.
As an experiment you can try putting some absorbent material on the sides of the console (facing the wall) to see just how much that corner is (or is not) affecting the sound. Absorption may not be the last or best solution but I suggest it only because it will allow you to hear if there is a potential problem or not. Cheap to test as a blanket or towel will do the trick.
OK, one last thing. Try elevating your speakers to get them at least two inches off of the floor. Especially with a carpeted floor, four inches is not too much. I think you will hear a less muddled bass therefore clearing up the upper regions as well. Another cheap experiment as even a cinderblock will work. Cover it with a towel to avoid scratches of course.
Have some fun with it!

[Nyal Mellor]

I think it would be helpful to distinguish the different frequency ranges. I'd agree it's far from axiomatic that dipoles have reduced room interaction and that overall it's a different mindset/approach.

Hey John - Great idea. We do have a little other text in there regarding dipoles performance in the modal region.

[John Casler]

I think it would be helpful to distinguish the different frequency ranges. I'd agree it's far from axiomatic that dipoles have reduced room interaction and that overall it's a different mindset/approach.

Exactly.

And not only frequencies, but the different directivity of the different driver types.

From 20Hz to 20kHz the room inter action will depend on frequency, driver type, and directivty/radiation pattern of the individual drivers.

All this is relevant even before you factor in distances to room boundaries and the angular incindence to the individual boundary. (caused by convergence angles)

So the original thread title of room relevance with OB (dipole) employment is correct.  All it might do is "change" the mindset making you rethink things when using that technology.

[JohnR]

Hey John - Great idea. We do have a little other text in there regarding dipoles performance in the modal region.

I've been doing some experiments with dipole subwoofers. In the area below about 120 Hz, in my room, I observed that:

1. Dipoles do interact with room modes (quite strongly).
2. Mode interaction is sensitive to orientation. Orientation along room width tends to excite modes in that axis; orientation along length tends to excite modes in that axis; orientation at 45 degrees excites modes in both axes. This is most noticable with the (2 0 0) and (0 2 0) modes. However the effect is not huge (a few dB). And can be hard to relate to modes.
3. Placing a pair of dipole subwoofers in "mirror image" gives almost the same response as having just one of them, but with increased amplitude.
4. "Nearfield" placement improves response at low frequencies (< 70 Hz). Up to a point - too close and the listener starts moving into the null.
5. A second dipole subwoofer can be used to tune in-room response. I placed a sub next to one main panel, and another right behind the listening chair. By varying delay to one sub I was able to obtain significant improvement in response smoothness, especially in the 70-120 Hz range.
6. In general, dipole interaction with the room is harder to predict than with monopoles. At times I had a null or peak that I couldn't readily explain, or get rid of.

These are initial observations based on a morning's measurements.

[AJinFLA]

OK, I admit that OB bass is a godsend in difficult rooms like mine.  And that OB's have an airy, open presentation that box speakers have difficulty matching.  But, does that make the room (and by extension, room treatments) irrelevant? 

NO!  In fact, in some ways I think that room treatments are more important with OB than with box speakers - after all, box speakers are mostly front radiators, and have a longer time cycle before interacting with rear walls (side walls are another story).

I had a head-slapping moment today that brought this home.  I've been trying to get better soundstage depth in my setup, something OB's are supposed to excel at.  But I think the hard, flat, reflective surfaces on the rear wall kinda killed that, even with my speakers pulled 4 feet into the room.  I have twin windows roughly behind each speaker.  I leave them bare, usually, because we live in downtown Denver and the view out of these windows is spectacular.

Today I dropped down my hexcomb window blinds on a lark.  Holy crap, the sound improved more from this than several weeks of tweaking crossover and eq settings in my active crossover!!! 

But, here's the really awesome news - my wife has agreed to let me put up acoustic treatments in corners of the front wall!  Tomorrow I sally forth to find some Owens Corning 703 compressed fiberglass to build some "real" treatments for the room.  I'm stoked!

Tyson,

Out of curiosity, what size is your room? I can't find any specs on your speakers, what is the mid/tweeter XO frequency? Is it modified, or the standard V2 design, no dipole tweeter? Thanks.

cheers,

AJ

[nickd]

No one seems to have mentioned this but OB designs seem to be easier on the ears. They excite the air in the room rather than adding and subtracting pressure.

if you have ever had LS9's of Montana WAS size loudspeakers you will understand (and maybe agree) that "sound pressure" takes on a different meaning when the loudspeker adds and subtracts pressure to your room and on your ears.

OB is one elegant solution to "listener fatigue" if implemented correctly.

[Pez]

They excite the air in the room rather than adding and subtracting pressure.

You've lost me, what does this mean?

[Tyson]

Tyson,

Out of curiosity, what size is your room? I can't find any specs on your speakers, what is the mid/tweeter XO frequency? Is it modified, or the standard V2 design, no dipole tweeter? Thanks.

cheers,

AJ

Room is about 12x20, closed on one side, open to the rest of the condo on the other. 

I use the GR Research V2's, but I swapped in the tweeter from the V1's, which has the rear chamber removed so it's a dipole as well.  Crossover varies as I like to experiment, but usually doesn't stray too far from 1khz.  The bass crossover is usually around 100hz.

[nickd]

Pez,
put 4ea  15" woofers in couple of big boxs or 24 ea 6" woofers in a couple of big boxes run a low sweep using a couple of hundred watts and you will understand. Your ears feel like you are changing altitude. It is "sound pressure", I understand that much, but in bigger systems I therorize the pressure affects your ears differently in a sealed or ported design than OB. I have heard all three. To my ears the OB sound seems just as loud but I don't feel quite the same "pressure" that a sealed or ported system makes exciting the same air

just my expierence. Thats why I like the Circle always somthing new to debate among like minded friends.