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In Reply to: RE: Agree to disagree. posted by RGA on April 27, 2012 at 21:28:59
What Tony said.
Check out this web page -- it compares monopole, dipole, and cardioid woofers. Note in particular the graph of the impulse response, all modes considered, near the bottom of the page. The benefits of the dipole diminish as you toe it in until at 45 degrees, it isn't much better than the omni, but I've found that in practice, with the moderate toe-in usually used, dipole bass is significantly smoother than monopole bass.
The downside of dipole bass is that you get backwave cancellation, so need more excursion and amplification for a given SPL. You also need large baffles, although they can be folded for a compact unit.
Another interesting possibility mentioned at the end of the page is to put the omni subs right behind the listener. He says that the variations that then occur are minimum phase, which means response irregularities can be equalized out. This would be effective only for a single listener, though.
Follow Ups:
I was able to cancel my worst room mode with my reflex loaded Focals in my system setup. This involved messing around with the cross-over settings and positioning of the speakers. I suspected this would be possible after several weeks of listening and tweaking, but I wasn't able to figure out how to make it work until I got a calibrated microphone and RTA and could see how the controls and speaker positioning interacted. Also, it was necessary to read some of the literature on the web on room modes, dipoles, sub setup, etc. which helped me make sense of what was happening. I can't say I really understood what I was doing, but I did get an intuitive understanding of how the response curve was related to my tweaking which helped get differing response curves. With a little listening of reference recordings it was then possible to fine tune the process and choose the most satisfactory compromise.
I suspect it would be possible to cancel an additional room mode if I got another sub, but apart from the cost I'm not sure I would be able to put it where I wouldn't trip over it without rearranging lots of stuff, and I'm happy with what I'm presently getting, both in sound and in measurements. It's hard to complain about a resolving system that reveals what's on each recording still making the mediocre recordings enjoyable if the musical performance is good.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Yeah, you can cancel more modes if you have two or even four subs, but only if you feed them a mono bass signal. With four, you might be able to use a stereo signal and cancel some of the depth axial modes.
I'm surprised at how few people use test equipment to help out with the bass. I'm as guilty as the next guy, I have a measurement mic and REW but never get around to using them. It's more fun to listen. Fortunately, my dismal almost-square room is broken up with about half of one wall opening on a hall, and between that and dipoles the bass is fairly good. (I've been wrestling with imaging instead -- a fireplace mantle that makes it impossible to use the speakers in the location that makes the most sense for the room.)
I agree that it's more fun to listen, but in December after doing that for several weeks and not progressing I ordered a mesurement microphone and real time analyzer and waited impatiently for them to arrive. My satellites have good response down to 40 Hz, so there was a lot of potential overlap between them and the sub.
The end result is +- 6 dB from 30 to 500 Hz measured 1/12 octave at the listening position so I don't think these is much to be gained with a second sub. Adding a second sub would undoubtedly involve moving all of my computer equipment out of the office and into a closet, which I may do anyhow for noise reasons but I would have to get a KVM extender system as my computers are presently tethered by their VGA cables.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
I hooked up my amp and projector to the computer in my home office, using a 50' HDMI cable from Monoprice for the video and USB repeater cables strung together for a second keyboard and mouse. While the setup was temporary, it was so nice to be without fan noise that I decided to put my new HTPC in the listening room closet. So I put in some conduit and a false molding so I don't trip over the cables, and also conduit and a hollowed-out baseboard in the hall so I could put a second keyboard and monitor in my office and eliminate the fan noise there as well.
I also found that I enjoyed surfing while I listened, I could read about the piece I was listening to, or check out a newspaper or magazine. And it occurred to me that since most of my work no longer involves paper, I could do most of my office work in my listening room, where I could enjoy the big speakers. The only downside I've found so far is that it robs me of an excuse to get a pair of Mini Maggies for my office . . .
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
So explain why with bass heavy music in an average room positioned per manufacturer rating do they sound so utterly unconvincing in the bottom end? They being the 20.1.
This is not aided with websites with calculus lessons.
It is real in room response and in the several rooms I've heard them in they've all sounded abysmal dynamically. Loud yes - some deepish bass yes.
Don't give me amplifier power. I have heard them always with appropriate amplifier power. Which is why it's funny that the completely inappropriate amplifier power was the only one that made them sound good.
Flagship - Class, Bryston, Meridian, Sim Audio, McIntosh, Anthem, Arcam, Rotel, Got some big beastly 1Kw amps here.
I will give it another try - next week or the following i will try the 3.7 or 1.7 again. They have a nice normal sized room and have them well away from all room boundaries. I liked the sound of the 1.7 with the AN gear but AN gear is too costly in the sense that the combined price for the system and the results don't make the endeavor worth the money and of course you can't play it loud.
I went to hear it today but they were closed for Buddha's Birthday and when they finally opened they were doing inventory. I would love to like them more because they're thinness makes them a rather dream space saver in Hong Kong where you can just shove them up against the walls when not in use. And of course the price is affordable. But they always sound "affected" and have some major off-putting attributes that I have never been able to get past. I keep trying them because there is something to them I like as well.
But if it can't be run with a SET - it is being fed inferior sound quality so it has a strike against. Fortunately the store did carry some tubes - we shall hear. 1-2 weeks.
I don't find them unconvincing in the low end. I love planar bass because it doesn't sound mushy and bloated like dynamic bass so often does. There's real detail in the notes. It sounds like real instruments.Of course, bass is very room sensitive and whether there's enough of it -- or too much -- depends on the room. Manufacturers can only design to an average room. It also depends on the specific model. The smaller ones are bass shy and pretty much want a sub. But I heard some wonderful bass from the 3.7's a couple of weeks ago. Not subterranean, they're good to maybe 40 Hz. But clean as a whistle and beautifully controlled. And the Tympanis still have the best midbass I've ever heard. Full-height line source planars are even better than you'd expect from that web page (you don't need the math for that, BTW, just look at the pictures at the bottom) because if you arrange them and your seating correctly, they act as a single bass array and *completely eliminate* room modes below a certain frequency. You can do the same thing with dynamic drivers, but it requires multiple drivers and electronic trickery. I hit on this trick years ago when I used Tympani 1-D's but had only a partial understanding of the theory behind it. Now I understand that below the spatial Nyquist frequency of the speakers and their reflected images, you get a plane wave, and with proper seating the reflected rear wave cancels even the depth axial mode for bass that's smooth as a baby's bottom.
Here's an interesting thread on the double bass array. Most people don't realize that line source planars can do the same thing without any electronics or rear speakers, if you get the setup right.
Edits: 04/28/12 04/28/12
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