Geddes Bandpass Subs and the Multi-sub approach - Page 7 - diyAudio
Go Back   Home > Forums > Commercial Sector > Manufacturers > GedLee

GedLee Home of the renown Geddes Loudspeakers

Reply
 
Thread Tools Search this Thread
Old 18th October 2010, 03:30 AM   #61
diyAudio Member
 
Join Date: Mar 2007
Location: Cleveland, Ohio, USA
Quote:
Originally Posted by gedlee View Post
I never said that they were the same thing. It doesn't really matter does it? It's function that matters and I suspect that they do work the same or similar . . .
I try to take everything online with a grain of salt, but the word "identical" was used . . . See post 41-
Geddes Bandpass Subs and the Multi-sub approach

No big deal.
I completely agree--if it wasn't clear in my post--that I don't need identical inputs, just comparable results/function. My '99 Civic gets me to work in the same amount of time, at a much lower cost, than a Lexus does. Good enough for the daily grind.

Nearly any non-hardening CLD goo, when used in conjunction with decoupling from the stucture (resilient channel, hanger springs, isolation clips, whatever) should be at least as effective as Green Glue sandwich screwed directly to studs as prescribed on the GG site. Tests over the years show that of all possible interventions for non-transmission of sound by absorption (as opposed to non-transmission by brute reflection -poured concrete, etc), decoupling is hands-down the first step to take.

pjpoes- I "get" your testing - I often do similar 'unofficial', but insightful tests at work. Here it's not necessary, unless one is trying to "prove" or create a competing product. I'm just taking a practical approach to comparing alternatives before slapping walls up, and joining the leagues of folks posting anecdotes on the forums.

FWIW, a follow-up to my previous look at GG: The stuff never fully "cures" - seems to remain gooey and tacky indefinately -- it hasn't changed a bit in several days now. It definately would dampen very well, and is very elastic when subjected to shear forces. The cured melamine glue is quite flexible, and does not break when subjected to reasonable shear, but it does not allow the constrained layer sandwich to flex as easily as the GG does.

The melamine glue (as well as underlayment glue, etc) are real glues - wallboard screws can (& should) be removed after curing. The GG is so elastic that it would surely result in wallboard resting on the floor within a day or two.

Given the resources, I would love to test how GG (which requires screws) would fare against a lesser CLD assembly that allows removal of screws. Any peformance gap might narrow considerably.

While this comparison may be impractical from a commercial standpoint (typical contractor just isn't going to wait for no glue to cure & then remove screws before patching, and you are a meddling idiot cuz he's been doing this forever and ain't no homeowner gonna tell him how to put up a wall), it does makes complete sense to a DIY'er or acoustic specialist.

I suppose all of this should have been started as a new thread . . .

-- Mark
  Reply With Quote
Old 18th October 2010, 12:16 PM   #62
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by Tubamark View Post
I try to take everything online with a grain of salt, but the word "identical" was used . . .
-- Mark
Hi Mark

Yes, thats true. I think that I cleared that up in my next post - that I meant "performance" and not "composition". At any rate, we are all on the same page. For what its worth, I don;t use any of that stuf anymore, because I found a two part polyurethane that cures very fast and is reasonably compliant and well damped, so I use this for all my CLD work now. The air-dry glues all seem to take too long to cure and most tend to harden completely as they age. I've also had Liquid Nails explode on me due to the solvents used.
  Reply With Quote
Old 19th October 2010, 10:46 AM   #63
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
I am designing a system of subs, and I'm trying to make use of the space below my mains directly beneath my woofer. It's a little over a couple of feet from the wall.

I want two subs that reach up above 100Hz, and one that reaches down to 20Hz.

My problem is that the main woofers go down to 70Hz. I would therefore like to put a 20Hz-70Hz woofer in the cavity beneath the mains but, it isn't large enough for that (1.5'^2).

So, do I choose to run over 100Hz and overlap the mains even though it will be so physically close to the mains that it risks causing a needless peak? or do I leave that space alone?
  Reply With Quote
Old 19th October 2010, 01:31 PM   #64
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
I would not use the space under the mains. This is bad place to put subs, but do overlap the subs with the mains.
  Reply With Quote
Old 19th October 2010, 01:45 PM   #65
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Thank you. I'd have been well tempted to use that space

If I may ask another question, if I want to put a sub in a corner, is it reasonable to run its output behind a corner bass trap or does the front of the bass trap become the 'new' corner?
  Reply With Quote
Old 19th October 2010, 02:29 PM   #66
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
At sub wavelengths, the trap is invisible.
  Reply With Quote
Old 19th October 2010, 03:43 PM   #67
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Quote:
Originally Posted by gedlee View Post
At sub wavelengths, the trap is invisible.
yep, but great for soaking up distortion or vent noise components
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 19th October 2010, 04:30 PM   #68
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Perhaps, depending on how the vent is positioned relative to the trap. I always place my vents so that they do not radiate directly to the listener. If they faced the trap then yes, that would work.
  Reply With Quote
Old 19th October 2010, 10:26 PM   #69
AllenB is offline AllenB  Australia
diyAudio Member
 
Join Date: Oct 2008
Quote:
Originally Posted by gedlee View Post
At sub wavelengths, the trap is invisible.
So, could I build a 150Hz sub into the space beneath my mains that needs a long port, and run the port right into the corner of the room, first going beneath the 10" thick bass trap which is held against the corner behind the mains, then pack around it to re-seal the trap?
  Reply With Quote
Old 19th October 2010, 11:25 PM   #70
pjpoes is offline pjpoes  United States
diyAudio Member
 
Join Date: Jan 2005
Location: New York
Send a message via AIM to pjpoes
I use the open cell reticulated foam in the ports to have the same effect, absorbing port noise and distortion.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 01:00 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2