Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Planar Speaker Asylum

RE: Except for corners?

64.252.128.97

In Reply to: RE: Except for corners? posted by genungo on October 09, 2010 at 15:36:35

What you get in the corner of a room is pressure maxima. Corners are effective locations for traps for that reason, but, according to Toole anyway, not for absorptive as opposed to resonant or active traps. Even if velocity weren't an issue, absorptive materials are fairly useless as bass traps, since they have to be about 1/4 wavelength deep to be effective, which is 2-1/2 feet at 100 Hz! Thus the usual approach for bass absorption is to use tuned resonators, which complement absorptive treatments nicely since they reflect higher frequencies.

Follow Ups:

RE: Except for corners? - genungo 03:32:42 10/10/10 (17)
I guess I had missed the point that it is possible to have pressure without velocity. And I better understand that homemade absorption treatments like John Risch's "quick & dirty" corner bass traps might work because of diameter, not just density. Thanks for the clarifications.
- RE: Except for corners? - josh358 07:11:18 10/10/10 (16)
  Apparently the real ASC's have to be fat as well because the internal air cavity behaves like a capacitor:
  
  http://www.tubetrap.com/technical.htm
  
  I've seen some online DIY tube trap projects that seem more sophisticated than the quick and dirty one, but I'm not sure how effective they are and most of the links seem to have gone dead.
  - DIY - genungo 08:58:04 10/10/10 (15)
    The original John Risch DIY basstrap did employ an internal air cavity and were effective down to around 60 hz. or so. The "quick & dirty" version (nothing more than solid, stacked rolls of fiberglass insulation covered with polyester batting) look pretty huge and ugly as they can take up almost three feet of floor space. I have tried these and they do help tame room resonances but I wanted something better looking. So, I invented my own version of a "quick & dirty" basstrap by wrapping 12" deep stacks of 4' tall rigid Rockboard panels tightly in burlap. After standing them up in the corners of my room with a triangular airspace left behind them, they proved to be even more effective than the Risch Q & D traps while looking much better with their clean lines and uniform surfaces. ATS Acoustics sells these bundles of Roxul Rockboard 60 panels for $49 each, and they also sell burlap fabric in many different colors.
    - ATS Acoustics (Open in New Window)
    Edits: 10/10/10 10/10/10
    - RE: DIY - josh358 09:46:30 10/10/10 (14)
      How deep do they go? I'm wondering about the efficacy of all these traps that only go to 75 or 60 Hz . . . seems like they're leaving half the problem untreated . . .
      
      Not that I can use traps in my front corners anyway, I have a closet that would be blocked.
      - RE: DIY - thetintdoctor 10:04:31 10/12/10 (10)
        
        In Reply to: RE: DIY posted by josh358 on October 10, 2010 at 09:46:30
        
        Hey Josh:
        You may have thought of this, but how about pressing the closet into service as bass trap? I believe you could do this while still using it as a closet.I wish I had the exact link, but I think I read about it on either the real traps site or the what's best? forum. The Ethan Winer section, I believe. Just a thought...
        
        RE: DIY - josh358 10:26:44 10/12/10 (9)
        
        In Reply to: RE: DIY posted by thetintdoctor on October 12, 2010 at 10:04:31
        
        That's a great idea, actually. But I'm not sure it's the right place for a bass trap, there's a 6' wide entrance arch on the right hand wall right up against the closet, so it isn't a pressure zone + the predominant resonance on that side of the room is going to be lower in frequency than on the left.
        
        I really have to take some measurements when I get things set up again, to find out where my modes actually are. The room is really too irregular for the mode calculators to produce accurate results.
        
        RE: DIY - thetintdoctor 10:44:12 10/12/10 (8)
        
        In Reply to: RE: DIY posted by josh358 on October 12, 2010 at 10:26:44
        
        Cool, I'm glad you can at least consider it as a possibility. :-) Ditto on the irregular room; I've got doorways, cathedral ceilings, fireplace, etc. The one plus I do have is a completely symmetrical area appx 14 X 8 x 8. This is the end of the room where the speakers sit. After that, though, it's pandemonium! At least it's a big room opening into 2 other big rooms. My lowest octave really isn't too bad, but from about 50 ~ 100hz, holy crap! I was able to mitigate that room rise by moving my speakers appx 59" from the wall behind them. Not exactly high WAF placement, but she loves the 60" plasma directly between and slightly behind the plane of the speakers. As someone else mentioned, it pretty much destroys image depth, though. See, that's why I need a motorized screen and a nice projector, honey. Oh well, one conquest at a time... ;-)
        
        RE: DIY - pictureguy 22:35:38 10/12/10 (0)
        
        In Reply to: RE: DIY posted by thetintdoctor on October 12, 2010 at 10:44:12
        
        I have a completely asymmetrical room of 8 sides, and an off center vaulted ceiling. At least as far as bass goes, I think of it as an advantage. A couple sides are at 45degrees, so I may be dodging some standing wave issues. Moving around the room listening for bass bumps has no result. My den, which is entered from the living room is sort of boomy which is OK.....
        Too much is never enough
        
        RE: DIY - josh358 16:34:37 10/12/10 (6)
        
        In Reply to: RE: DIY posted by thetintdoctor on October 12, 2010 at 10:44:12
        
        That closet is going to do something or other, my current plan is to put the HTPC and amp in it and exhaust it with a duct and a fan into the hall on the other side of it to eliminate the fan noise. Already put in cable conduits and a removable crown molding so I can run cables in and out, as well as running Ethernet and power. Of course, there are at least two other things I'd like to do as well as the closet as well! It's a great place for my vacuum, and for winter coats. But priorities are priorities, and eliminating fan noise is high on the list. Plus it's probably acting as a bass trap to some extent already, given that the wood door is 315 years old and must be nicely diaphragmatic by now.
        
        Now, I have to live not only with the asymmetrical opening behind the speakers but with the fact that the left and right walls aren't precisely on center with respect to the fireplace. I've toyed with the idea of building a false wall a bit beyond the arch, that would make the room symmetrical behind the speakers but it would be an architectural nightmare.
        
        I don't know what my room is going to sound like when I put everything back together, since I decided to change the orientation after I'd taken it apart. I did try the speakers that way (oriented with the fireplace behind them) when I first got them and they sounded better than they did along the other axis, but at the time I didn't see how I could make my home brew fixed screen coexist with the fireplace. I have a friend who just bought a window shade and uses that for his projector, and sure enough, you can get a pretty big vinyl window shade for practically nothing. Who needs a fancy tab-tensioned motorized screen? If the shade develops wrinkles, you can get a new one and throw the old one away. And DLP projectors are dirt cheap now.
        
        RE: DIY - pictureguy 17:19:38 10/13/10 (5)
        
        In Reply to: RE: DIY posted by josh358 on October 12, 2010 at 16:34:37
        
        Is 'diaphramatic' a word?
        
        If it's a hollow core door, turn it into fireplace material. If solid core, sheet one side with something ......inert. I've seen a studio where the door had a sheet of lead on one side.....you could never get away with that today. A sound control store near here has 'blankets' to put on a door for sound insulation, usually in factories.
        
        Too bad we live in 'real' spaces and not an idealized sound room.
        
        AHHHHH if only I was born rich, instead of just good looking.
        Too much is never enough
        
        RE: DIY - josh358 17:40:16 10/13/10 (4)
        
        In Reply to: RE: DIY posted by pictureguy on October 13, 2010 at 17:19:38
        
        So is "diaphragmatically." Now how the hell would you use that? "I breathe diaphragmatically."
        
        Yeah, hollow core doors are the pits, I was knocking on (and painting) one just yesterday and it had a god awful resonance. But the 315-year-old closet door is made of a couple of big planks, held together with cross braces. I'm not sure you can get boards that wide anymore. You can still buy real sound control doors, but they're expensive (and no fun to mount). I'm not really sure what if anything I'll have to do at that end of the room. I'm concerned that the closet and the wall on the other side of the fireplace aren't at quite the same depth, I'm hoping it's the wall because I'll be able to build it out.
        
        RE: DIY - pictureguy 10:25:24 10/14/10 (3)
        
        In Reply to: RE: DIY posted by josh358 on October 13, 2010 at 17:40:16
        
        I just think it's funny......You may have invented a word.
        Perhaps.....Diaphragmistically?
        'Diaphragmistically, politician X is full of gas'
        
        OR
        
        'The lead singer for band X is diaphragmistically inhibited.'
        
        I would HATE to remodel Very Old Work. 'They' built 'em good back then, but differently.
        I lived in a house in Fullerton which was near 70 years old. Knob and Tube wiring and a total of about 6 outlets in the entire house. A fire waiting to happen. My dad, who let me 'do my thing' came for a visit and turned pale. 'This electric service hasn't been code since the '50s! I'd move!' Which was about as stern as he got, once I became an alleged adult.
        
        If you strip the paint off that door, I'll bet it's a beauty....
        Too much is never enough
        
        RE: DIY - josh358 11:08:21 10/14/10 (2)
        
        In Reply to: RE: DIY posted by pictureguy on October 14, 2010 at 10:25:24
        
        The amazing thing about these old houses is the beams, immense rough-hewn chestnut beams from the forest primieval that support the house. You can see part of them in this picture -- they cut away part of the vertical one in the 19th century to enlarge the window, also boxed the one that runs laterally -- the same beam is exposed and rough hewn in the next room.
        
        RE: DIY - pictureguy 15:28:57 10/14/10 (1)
        
        In Reply to: RE: DIY posted by josh358 on October 14, 2010 at 11:08:21
        
        The place I lived in Southern California was not 1/8th as nice. It was sagging in spots and it took an ENTIRE hot water heater for a single BATH. NO insulation, either, and I slept part of the winter in my sleeping bag, which would, outdoors, keep me warm into the low 20s.
        Your flooring alone is worth more than that place was.
        But OH, the parties! Friend brought over a guy he met at school. He stood inbetween the speakers and jammed on harp for about 2 hours....to anything I put on.
        Weeks later, 'the band' showed up. Do you have any idea how far away you can hear a Marshall Stack?
        
        Too much is never enough
        
        RE: DIY - josh358 16:23:58 10/14/10 (0)
        
        In Reply to: RE: DIY posted by pictureguy on October 14, 2010 at 15:28:57
        
        That oak floor was (is?) in pretty sorry shape, actually. It was put in in the late 19th century over the original planks, and everything is sagging. It looks pretty good because I just had it refinished, but it has a lot of patina to it. If I had infinite time and money, I'd pull up the oak planks and restore the original floor, which has even more patina (like big holes in it).
        
        A few months ago, I was in one of these old saltboxes that had been restored, and it was more like a cabin than a room -- wood walls, exposed beams, and those old Tudor-style windows with the diagonal lead frames -- a reconstruction since the lead from the original windows in these houses was apparently melted down to make shot during the Revolutionary War.
        
        But your old house sounds like much more fun. Reminds me of the friends who lived in lofts in New York, and the wild parties they used to throw.
      - RE: DIY - genungo 10:26:30 10/10/10 (2)
        
        In Reply to: RE: DIY posted by josh358 on October 10, 2010 at 09:46:30
        
        I'm not exactly sure how deep these DIY traps go. It might depend on the sizes, the locations, and how many of them you use. I think that a Risch Q & D corner trap about 4 feet tall does not absorb too much below 80 hz. or so, but if you stacked the material all the way up to the ceiling you would get better performance. However, it is said that the typical listening room could really use treatment for bass resonances in the 60 to 80 hz. range, so our DIY traps are not a bad place to start.
        
        Edits: 10/10/10
        
        RE: DIY - josh358 11:01:57 10/10/10 (1)
        
        In Reply to: RE: DIY posted by genungo on October 10, 2010 at 10:26:30
        
        That's true. My own room has a first and two second modes between 80 and 89 Hz. Unfortunately it also has two first modes between 40 and 45 Hz . . . I suppose I could tune those out and let the treatment take care of the higher frequency modes, but I'd need four subs to do that, which is three more than I have. Another possiblity would be to put the chair right in the null of both modes, but I don't have a big enough room . . .
        
        It's all academic, anyway, my room is kind of irregular and the calculations never quite work anyway (because of doors, flexible walls, etc.). To do it right you really have to measure and tune.
        
        RE: DIY - pictureguy 17:21:06 10/13/10 (0)
        
        In Reply to: RE: DIY posted by josh358 on October 10, 2010 at 11:01:57
        
        Tell me about wacky shaped rooms!!!!!
        Too much is never enough

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors:

Parts Connexion