Multiple Small Subs - Geddes Approach - Page 152 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th January 2013, 05:24 PM   #1511
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by Omholt View Post
Thanks gedlee.
What about the size of drivers for bass reproduction?
Does bigger come at a cost?
Of course - bigger is always better, but its not free. Larger sizes are always more expensive to make and take up more room. Its simple really.

I have given up on subs of any variety except closed boxes - as big as you can afford. Everything else (ported, bandpass, LF horns, etc.) is just fluff with little real impact on what matters. (I assume that one is using multiple subs and a controller of course, but in this thread that's a pretty reasonable assumption.)
  Reply With Quote
Old 8th January 2013, 05:36 PM   #1512
diyAudio Member
 
Join Date: Jan 2008
Location: Toronto and Delray Beach, FL
Quote:
Originally Posted by gedlee View Post
As expected people are confusing thermal compression with thermal modulation. they are related but distinctly different effects.....

That this effect is real, I would stake my reputation on, the level of its significance is still only a guess...
Sorry to continue thread hijack. Then likely no perceptible effects on a cycle time-frame but possible gross compression influence over longer periods in non-Gedlee speakers?

Got that, jcx?

Ben
__________________
Dennesen ESL tweets, Dayton-Wright ESL (110-3200Hz), mixed-bass Klipschorn (35-110), and giant OB using 1960's Stephens woofer (20-35); Behringer DSP. HiFi aspirations since 1956

Last edited by bentoronto; 8th January 2013 at 05:38 PM.
  Reply With Quote
Old 8th January 2013, 05:41 PM   #1513
Moonfly is offline Moonfly  Spain
diyAudio Member
 
Join Date: Oct 2012
Quote:
Originally Posted by gedlee View Post
Of course - bigger is always better, but its not free. Larger sizes are always more expensive to make and take up more room. Its simple really.
Personally, I wouldnt say bigger is more expensive, not when you consider what you get. OK, so a 15 inch driver is going to cost more than a 12, and the larger cabinet will cost a bit more in material. If you want to match its low end output (the bit that matters), you would need a pair of 12's, so in those therms the larger sub is actually cheaper, and give more output for your cash outlay. Building smaller is really false economy if looking at it that way.
  Reply With Quote
Old 8th January 2013, 05:49 PM   #1514
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by gedlee View Post

I have given up on subs of any variety except closed boxes - as big as you can afford. Everything else (ported, bandpass, LF horns, etc.) is just fluff with little real impact on what matters.
Why then is this "fluffy" passive radiator bandpass sub (with only vague specifications) the only one listed on your website ?
Attached Images
File Type: png Fluffy.png (155.5 KB, 180 views)
  Reply With Quote
Old 8th January 2013, 06:18 PM   #1515
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by weltersys View Post
Why then is this "fluffy" passive radiator bandpass sub (with only vague specifications) the only one listed on your website ?
I still sell the PR bandpass - at least while the PRs hold out as they are no longer available. It is a "good" sub. There are other models listed in the price table.

What specifications are relavent for a sub?
Resonance? - doesn't matter, it will be EQ'd.
Power handling? - look that up on the B&C website - 12TBX100
Efficiency? - also on the B&C website.
  Reply With Quote
Old 8th January 2013, 06:22 PM   #1516
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by bentoronto View Post
Then likely no perceptible effects on a cycle time-frame but possible gross compression influence over longer periods?

Ben
The time constants tend to be too long to be a factor for low frequencies, but not for tweeters. A burst of HF material and the tweeter heats and a burst about 1 ms later will be lower in level with a change in frequency response.

This is dominately a HF effect, which is why its kind of out of place here.
  Reply With Quote
Old 8th January 2013, 07:15 PM   #1517
diyAudio Member
 
Join Date: Jan 2008
Location: Toronto and Delray Beach, FL
Quote:
Originally Posted by gedlee View Post
The time constants tend to be too long to be a factor for low frequencies, but not for tweeters. A burst of HF material and the tweeter heats and a burst about 1 ms later will be lower in level with a change in frequency response.

This is dominately a HF effect, which is why its kind of out of place here.


1 millisecond, taking that figure as a rough guestimate, is still seems too slow to matter for a tweeter since it represents half a cycle at 500 Hz. I suppose it might compress the tail end of a full cymbal crash to an unknown (but likely, imperceptible) amount.

Ben
__________________
Dennesen ESL tweets, Dayton-Wright ESL (110-3200Hz), mixed-bass Klipschorn (35-110), and giant OB using 1960's Stephens woofer (20-35); Behringer DSP. HiFi aspirations since 1956
  Reply With Quote
Old 8th January 2013, 07:28 PM   #1518
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
Quote:
Originally Posted by bentoronto View Post
Sorry to continue thread hijack. Then likely no perceptible effects on a cycle time-frame but possible gross compression influence over longer periods in non-Gedlee speakers?

Got that, jcx?

Ben
still relying on the kindness of others to do your reading for you when you apparently didn't believe in any aspect of the problem - you didn't qualify by time scale

I can't read Geddes mind - but thermal compression in dynamic drivers has been described in the literature for a long time now

and in fact the envelope modulation "compression" does occur on human perceptible time scales - if you have 10s of seconds attention span

Quote:
Originally Posted by bentoronto View Post
Inhibiting my first impulse to consider those comments on efficiency crazy out of well-earned respect for the author (not to mention the possibly casual use of the word "instantly" in an otherwise rigorous presentation).... For sure, I have never heard this idea or that distortion, compression, or whatever results in copper wired devices connected to low-impedance driving sources.

Without necessarily agreeing with a word of the theory, I like to hear more about the tests. Can you please tell us more about your tests?

Ben

Last edited by jcx; 8th January 2013 at 07:33 PM.
  Reply With Quote
Old 8th January 2013, 07:41 PM   #1519
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by gedlee View Post
I still sell the PR bandpass - at least while the PRs hold out as they are no longer available. It is a "good" sub. There are other models listed in the price table.

What specifications are relavent for a sub?
Resonance? - doesn't matter, it will be EQ'd.
Power handling? - look that up on the B&C website - 12TBX100
Efficiency? - also on the B&C website.
Last time I checked, the only specification that applies to your PR bandpass sub on the B&C website was the power handling and DC resistance of the 12TBX100's voice coil .

One can certainly EQ anything flat at a low enough level, but if one actually wants high SPL low frequency, there are many useful specifications which will separate the wheat from the chaff.

Relevant specifications for a sub are frequency, phase, and impedance response, sensitivity, harmonic distortion at rated power, and power handling.

Since manufacturers know that showing THD at the rated voice coil power handling would look terrible, we seldom see more than phase, frequency, impedance and sensitivity response.

Those would be three relevant specifications that are lacking for your "good" sub.
  Reply With Quote
Old 8th January 2013, 09:48 PM   #1520
gedlee is offline gedlee  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by jcx View Post
I can't read Geddes mind - but thermal compression in dynamic drivers has been described in the literature for a long time now
I know of no literature that talks about thermal changes on a short time scale, only steady state SPL compression. If you know of such literature them please inform us.
  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 07:16 AM.


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