[timbley]

After poking around here for a few hours I came across some discussion of research by David Griesinger about sonic envelopment through low frequency spacial reproduction in small rooms.
 http://www.davidgriesinger.com/asa05.pdf
He recommends woofers at each side of the listening position, with one playing 90 degrees out of phase from the other to get some swirling about of the apparent location of the bass source, as happens in real concert halls.
I realized that I have a really good set up right now for playing around with this. My bedroom experimental system bass cabinets can easily be moved to the sides of my listening position. Since I have a digital active crossover it's also easy to time align the now side to side bass with the fronts, and apply the 90 degree phase shift to one bass channel.
The bass cabinets, Athena AS-B1 bookshelf speakers, are crossed over at 488hz with a 48db/octave slope and go down to about 40hz. The front speakers are little Polk TL-1 satellite speakers with 2 1/2" mids and 1/2" dome tweets. Pretty wide dispersion. I have acoustic panels to the sides and in the rear corners and on the back walls behind them.

So I did the setup and am listening right now to this Spacial effect. At first it sounded rather odd. The side speakers needed to be lifted off the floor and level adjusted, and the fronts needed to be lifted a bit higher too. Now that everything is fairly well balanced I'd have to say it is quite impressive. I'm currently listening to  Oregon's Northwest Passage album, and it's trippy. Definitely a big sound! I'll have to try some classical symphonic music next. I don't really hear anything weird or bothersome from the 90 phase shift between left and right bass cabinets. The 488hz crossover doesn't seem to be causing any horrible problems either, although I think I hear a little off-ness there from time to time. The side speakers are about 4 ft off to either side but looking at them I could swear they are turned off and somehow the bass is coming from the wall in front of me, behind those little tiny Polks. The bass sounds very good. I think that's due to the fact that the bass is closer to me and turned down about 5db, so I'm hearing it more directly and less from room bounce interferences. Overall the sound is bold, rich, and spacious. I guess enveloping is a good word for it.

Anybody else is using this kind of setup? So far I'm not in a hurry to put things back so that's a good sign.

[poseidonsvoice]

Timbley,

Excellent paper.

Big fan of Griesinger’s work as well as is Earl Geddes.

To better illustrate what you have changed, do you mind uploading a picture of your setup? Before/After setups?

Thanks,
Anand.

[timbley]

I will upload some pictures after I get things cleaned up a little. It's kind of embarrassing after seeing so many beautiful, elegant systems on this forum. This is more of a laboratory room. Everything is ad-hoc, including using CD storage cases as speaker stands. I have to walk gingerly so nothing falls down.
From David's papers and videos it seems that this low frequency spacial effect needs to be on the recording. His survey of recordings suggests 20 percent or so will have the stereo bass with random phase shifts. I'll have to do some more listening, but a few hours last night sounded very good to me on pretty much everything. The hard part is it sounded great before, so is it better?
I also recently broke into the little Polks and the Athenas and bypassed their passive crossovers so it's now a fully active 3 way system. It sounds great, but once again it sounded great before. I think in both cases it's better and I'm in no hurry to undo anything, but it's hard to quantify exactly what I think sounds better.

[timbley]

A couple of pictures of the bedroom lab set up with the Spacial Bass arrangement. Speaker stands are a major priority, I promise!
I also desperately need to replace that old Lazy Boy recliner. My initial plan was just to sit on the floor. It's supposed to be better for you. Floor sitting listening position opens up a whole new avenue of speaker setup experiments.




Here's how it was before, with the Polks sitting on top of the Athenas:



And here's an earlier experiment to control early reflections. Didn't sound good for music, but listening to spoken word was exceptionally clear. This experiment is where all the goofy looking sound panels came from. I was hoping those boxes would work well on the bass, but they don't. The bass gets out of the box, somewhat attenuated, and then bounces around the room, which has untreated corners so it's about as bad as it can get, as verified with a MATT test. Also sounds dark because the bass gets out but a lot of the highs and mids get absorbed. That can be equalized, but it still has muddy bass. Much better to treat the whole room. I realize now that I could try this again with the bass cabinets by my sides, outside the absorption boxes. I haven't torn down those boxes yet so if I have the will power I could try it again. Still, I think this is generally a bad idea. Takes up too much room for questionable benefit in controlling dispersion. A bigger speaker with a waveguide is much more efficient.

[Speedskater]

I'm also a fan of David Griesinger.  Siegfried Linkwitz (RIP) also wrote on the same types of subjects and his page has links to many other authors.
http://www.linkwitzlab.com/

* * * * * * *
also a fan of Doc Earl Geddes.

[timbley]

Speedskater,

All those guys have put out some great information. It's interesting all the different takes on things. Linkwitz doesn't like the sound of waveguides. His writing got me interested in trying a wide dispersion speaker again after I just went to great lengths to build big horns. I went cheap and got those little Polks as a starting point. I think they really sound great in my small bedroom, early reflections and all. It surprises me how much I like them, although I do have absorption on the walls directly behind and to the sides of them.

 Geddes got me interested in the problems with exponential horns. Despite their problems, they sound good to me, provided they aren't too long and skinny and diffractive at the mouth.  I hear what Linkwitz said about the unnaturalness of the highly directional sound. I hear it at first because it has a different presentation than my own voice or other ambient sounds in the room. After a few minutes I don't notice it at all and find the music increasingly enjoyable as time goes on. They also project well into adjacent rooms, something my non audio nut friends have commented on multiple times.
I built some big, 3 foot mouth 9 sided conicals and some smaller conicals  after reading Bill Wood's praise of them. They sounded good, but to my ears an exponential of similar proportions sounded as good, and required less equalization. I measured some pretty hard mouth diffraction effects from the  suddenly terminated conicals. I have a hard time understanding his dismissal of a round over at the mouth because it merely "ameliorates" the problem. I'm all for ameliorating problems.

Ha, I just realized that remains of my old concrete 5 way direct radiators can be seen outside. Those mid bass boxes were a complete failure, resonating like a bell at around 200 hz. Crazy heavy too. They served for a long time as compost bins. The concrete subwoofers however were awesome! Insanely heavy and big. I used them to supplement the Klipschorns for a while, till I decided they were too big to live with. Now I have no idea where they went.

[timbley]

Oh, and let us not forget Don Keele! The curved, banked attenuated line array he is pushing lately looks very interesting.

I also think there's tremendous merit to Ralph Glasgal's ambiophonics, although my experience with it so far has only been successful using a physical barrier. A working ambiophonic arrangement knocks my socks off for stereo imaging and realism unlike anything else I've ever heard. Unfortunately these setups are pretty hard to live with and I always end up taking them down.
Keele also played around with a physical barrier and noted that the effect was excellent. Too bad it's so impractical!
I had some Polk Stereo Dimensional Array speakers that tried to minimize crosstalk. Like the digital solution, it really didn't work that well and I  disabled that feature. I had a Carver Sonic Holography pre-amp too. It really didn't work either, not like a physical barrier.
I also tried near field speakers behind my head to eliminate crosstalk. This is a neat idea because if you're not in that sweet spot the rest of the room just sounds like normal stereo. This created a huge sound field effect for me, but I couldn't get it to sound reasonably natural. Quite entertaining though. Maybe they could use that for special effects in theater seats.

[timbley]

I got in touch with David. He sent me some test files to compare the same recordings he made in concert halls with mono bass and stereo bass. I can definitely hear the difference, especially where he's exaggerated the effect, but I think I can be pretty happy without the spacial bass speaker arrangement and it's related encumbrances and anomalies.  I'm going to listen some more on headphones. I do think I like the spacial bass better than mono, but it's not a deal killer for me.

So for now I'm done with this experiment. The woofers are back to their normal position under the mids and tweets. Less enveloping perhaps, but more coherent.

Now to get some speaker stands.