Acoustics
tmartin2 -- Sat, 07/30/2005 - 22:38
Where on the forum do I find information on room acoustics, measurement and products that fix acoustic problems?
Where on the forum do I find information on room acoustics, measurement and products that fix acoustic problems?
This section is fine to post questions on room acoustics. If we get a big enough thread, we can always add a dedicated section.
Short of buying a bunch of test gear or a Velodyne subwoofer, are there good programs on the PC that can be used in conjunction with a standard microphone that can help one tune a non-rectangular room?
Thanks
Jim
All the modeling software I've seen assumes a rectangular room. But Velodyne should soon have a low frequency EQ out, under $1k, that has their measurement mic and software. I'm using an Ivie IE-33 real time analyzer, which is very nice (built around an HP PDA, so handheld). www.ivie.com. But that's around a $2k solution.
Another interesting possibility is at
http://www.nvo.com/winmls/winmls2004/
I want to let all AVGuide forum participants know that the editors and writers of The Absolute Sound and The Perfect Vision will be engaging in the forum on a regular basis. Bring on your questions, comments, thoughts about the magazines. We'd love to hear from you.
We will also publicize this forum in the magazines so that we get more participants and generate some interesting and stimulating threads. I look forward to seeing you on the forum.
Robert Harley
Editor-in-Chief
The Absolute Sound
The Perfect Vision
Jim,
To field your question, an intriguing new solution is Velodyne's SMS-1 system, which is essentially the Velodyne measurement/EQ/control system, but for use with any subwoofer (not just with Velodyne subs).
Another potential option is (or was) the RDES (Rocket Digital Equaliser System) from Onix/Rocket. I looked into a prototype version of RDES some time ago, but am not sure where the product now stands. Check out Rocket/Onix at: www.av123.com
Best,
Chris Martens
Audio Editor, The Perfect Vision
Senior Writer, The Absolute Sound
Chris Martens
Editor, Avguide.com/Playback/The Perfect Vision
I can highly recommend two pieces of software that will tell you just about anything you want to know about your speakers, your room, your electronics, and the interface of all three.
The first is the Praxis Suite from Liberty Instruments (http://www.libinst.com/), which is pretty much the gold-standard measuring suite for speaker developers and designers in the U.S. (Alon Wolf of MAGICO uses it, for one of a great many.) It will also do room acoustics exceedingly well.
The second is Room Tools from the same folks who make the Ascendo loudspeakers (http://www.room-tools.com/). It is the European counterpart of the Praxis Suite and, like Praxis, is widely used by designers and studios (such as BMG and DG). Though not as fully featured (or, frankly, as computer-geeky) as the Praxis suite), it wil tell you what you want to know about speakers and room.
BTW, both of these programs are excellent choices for subwoofer setup (via RTA and phase-repsonse analysis). Both require a laptop or desktop computer and a high-quality soundcard that allows stereo I/O and has provision for a microphone input (and phantom power for the mike). I use the M-Audio Transit USB box with Praxis and the Edirol UA-25 box with Room Tools.
I should note that neither of these software programs is cheap. They will run you $1200-$2000 each. And that does not include the price of the outboard soundcard, a good mike, and assorted cabling.
Jonathan, do these software tools "assume" a rectangular room?
I asked because my listening room is irregular and some of the less expensive software solutions don't work for me.
Thanks.
Jim,
I use the ETF and R+D software:
www.etfacoustic.com
Both together cost only $150. There's also the Room EQ Wizard which is free, but requires you to install a 100+ MB Java runtime engine:
www.hometheatershack.com/roomeq/
There are also test tone CDs you can download for free (there's one on my company's site), but test tones show only raw frequency response, not low frequency ringing which is just as important.
I'll also mention that room prediction software is never reliable, especially with an irregular room. Even with a basic rectangle room, the only way to know for sure what you have is to measure the bass response.
Buying software is useful because it not only lets you verify what you have, but is much faster than using a test tone CD. So you can more easily experiment with speaker and listener placement. Instead of taking 5+ minutes to plot a room, it takes only a few seconds. The ETF software I use also has a continuous update mode so you can start it sweeping, and as you move things around the display updates continuously. This lets you hone in on the ideal speaker placement very quickly.
--Ethan
www.realtraps.com
The acoustic treatment experts
No, Jim, neither software program makes any "assumptions" about room size or shape.
I should note that both the Praxis Suite and Room Tools are primarily speaker design and room analysis tools, intended primarily for folks who need quasi-anechoic frequency-response measurements, waterfall plots, phase curves, etc. They are probably overkill if you plan to use them solely as RTA analyzers for subwoofer setup. Nonetheless, they will do that job with high accuracy--and will also tell you precisely how your room is shaping the sound.
I know nothing about the ETF and R+D software that Ethan recommends. I assume that it is designed to do many of the same jobs that these more expensive programs do for a lot less dough. BTW, I agree with Ethan about the convenience (and much higher accuracy) of using tone bursts and computer-and-microphone measurements compared to CD test tones and an SPL meter.
As far as I know, most automated room-correction systems and acoustic modelling software assume a sealed rectangular room. Irregular spaces don't adapt themselves easily to such technology, but they're often the spaces that sound best.
I'm therefore still a member in good standing of the old school of room-tuning by ear.
BW
Barry, I tune my system by ear, too. I do not use either the Praxis Suite or the Room Tools Suite to set up my stereo, although I have used both to measure loudspeakers and the acoustical properties of my room. Since I don't currently have a subwoofed stereo system, I haven't yet used them for setting up a sub, but, frankly, that would be the one place where I think measuring output and phase of both sub(s) and sats (at the listening seat) could make level and positioning adjustments (i.e. sub/sat blend) easier to get "right."
I repeat: Unlike automated room-eq systems, neither of these software suites makes any assumptions about room shape or size. They are measurement tools, not room-correction devices.
Setting up subwoofers can be tricky. Home theater guys, who see subs as "LFE" devices, like putting them one-third of the way into the room.
My approach is music first. Because the sub and primary speakers have some frequencies in common, I try to place the sub so its wavelaunch is on the same horizontal plane as the front left/right. Getting the phase correct is simply a matter of finding which way bass sounds loudest with both sub and front speakers playing. Then you turn the sub's crossover control to as low as it needs to go to provide bottom fill, and adjust the sub's level control to the point where the bottom end energizes the room without the sub bottoming out or drawing too much attention to itself. Simple once you understand the relationships. A well-integrated subwoofer can improve almost any system.
BW
You've obviously had better luck than I have with integrating subs into music-only stereo systems. Over the better part of two decades I've tried to mate just about every make and model of sub on earth (including the mighty Krell) to "fast" (electrostatic and/or planar and or superb two-way) loudspeakers without achieving fully satisfactory results. Sure, I got more bass (though not always "better" bass), more "floor," richer lower midrange timbre, and sometimes more apparent ambience retrieval. But...I've never heard a sub that didn't, to some extent, veil the midrange of the "satellite." No matter what the crossover frequency, no matter what the slope, no matter what the phase angle, no matter where the sub was placed in the room, I have always lost some subtle texture and detail—some of the very things I bought the "main" speaker for in the first place. It has always seemed to me that you have to have “forgiving” ears or a very short-term auditory memory to overlook the slight but unmistakeable loss of transparency that inevitably accompanies the addition of a sub.
However, if a slight loss of transparency is a trade-off you can live with—and most audiophiles can—then a sub is a good idea (although I would strongly recommend adding two subwoofers, if you don't want to compromise soundstaging and imaging).
As for sub setup...I also believe in trying (in so far as it is possible) to time-align the subs with the mains by placing them out into the room, roughly in the plane of the main speakers, although this does not guarantee that you won't run into room-node problems that can generate nasty resonances in the 60-80Hz range. Nor is setting phase by ear to get the "most bass" necessarily the formula to get "best bass," in my experience.
I should add that I am definitely in the minority when it comes to my views on subwoofers. Most audiophiles swear by them, including many of the reviewers/editors on TAS’s staff (HP foremost among them).
I agree with Jonathan on adding subs to electrostats.
I've tried many and wasted a bunch of money only to ultimately take the subs out of the system. They do impact on the purity & transparency of the mids of the 'stat---the primary reason to put up with 'stats in the first place. (Yeah, subs can be fun initially for power music).
Admittedly, I haven't tried dipole woofers with 'stats (but I probably will).
Some argue that a dipole woofer mimics the wave launch pattern of an electrostatic and can therefore blend in better if positioned correctly.
The only dipole woofers I'm aware of are DIY kits based on Linkwitz designs. Anyone know of others besides used Typanni 1Ds, etc.?
I have had much better success adding subs to dynamic driver systems, particularly mini-monitors, and concur that a pair of smaller subs is superior to a single, larger one (in terms of imaging/focus).
I'm largely with Jim and Jonathan on this topic. I too have tried adding subs to notoriously bass shy speakers--LS3/5as, Maggies, Quads--and in every case ended up preferring the speakers without the sub and realizing that it's generally best to accept these designs for what they are. If deep bass is a priority, then one should probably buy a speaker designed to deliver it and not mess with ones that aren't.
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