Best vented transient response - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 23rd December 2006, 01:07 PM   #1
diyAudio Member
 
Join Date: Dec 2002
Location: dry ol Melbourne Australia
Default Best vented transient response

I've searched this forum (and dickason): for a given driver - how to best model boxes to predict and optimise vented box transient response . . some learnings:
"more gradual rolloffs have better transient response than steeper rolloffs"

(If I were doing sealed, I'd aim for Qt of about 0.7, but I have some big drivers suited for vented)
"wisely chosen vented alignments can produce bass as refined as a moderate Qtc sealed alignment".

~ Unibox simulates step response/ tone burst
~ Win ISD simulates group delay very interactively.

I believe that settling time (rise time + the time of any "ringing") step response is generally the better compromise of fairly fast rise time with a slight overshoot, that best predicts transient response.

. . ie rather than Win ISD simulated group delay - use Unibox's step response

if I am right, the next step along this line of optimisation is looking at step response graphs - at what point is settling time achieved, and how much time difference is signifcant . .

The multiple wiggles of a vented box's step response make comparisons hard - who could comment on my suggestion of a good yardstick -

the mimimum time by which (Unibox's) step response is no more than ~ 0.1(?)

Thanks
  Reply With Quote
Old 23rd December 2006, 04:35 PM   #2
diyAudio Member
 
Join Date: Dec 2002
Location: dry ol Melbourne Australia
playing with Win ISD, I see for better transient response, build the biggest box, tuned low . .

. . the ultimate "alignment" of which is probably the Onken . .
  Reply With Quote
Old 23rd December 2006, 09:52 PM   #3
diyAudio Member
 
Join Date: Nov 2005
The alignment called SBB4 in Dickason is the best vented enclosure for transients, and all I use. Current project uses Scanspeak 25W (the lower Q version) in 6 cu ft, with the box tuned to ~18 Hz. Bass is very clean, no hangover or "one-note-ness".

Several advantages;
Earlier mild rolloff helps compensate for room gain.
Driver is loaded to <20Hz.
Driver excursion is reduced as you approach resonance.
And in my experience, tuning is not particularly critical.

The principal disadvantage is the box size. I also used this once in a commercial design, the 18W tuned to 28?? Hz or so, also with good results.

As a general bias, I believe that keeping the driver loaded for all program content is a good idea, so for smaller drivers I prefer sealed.
  Reply With Quote
Old 24th December 2006, 03:19 AM   #4
diyAudio Member
 
Join Date: Dec 2002
Location: dry ol Melbourne Australia
Default Beyond SBB4 . . but not Onken

Of the normal vented alignments, yes the SBB4 with those attributes is very appealing. (And the Scanspeak *W's with the SD1 motors are great drivers).

If a driver is suited to the Onken alignment - very high Vas I think is most important - and you can live with a giant box, reports suggest the Onken is best vented enclosure for transients. the Onken seems to be the final step along the spectrum of larger box, tuned low, yielding slow roll off and better transients.

I'm looking at the best way to use a 15" JBL pro driver (the 2035, with a big but not massive Vas of 192 litres). Onken_calc.xls suggests (depending on Rg) a 285 litre box, but I don't want it that big
The priority is transient resonse rather than depth.

planet10 said in a similar thread a while back
"The classic vented box alignments are an artifact of a time when we didn't have personal computer programs - and not even any calculators. back then it was a long tedious process to calculate out even one alignment. So they picked a few spots on the curve and generated tables & graphs so that anyone could easily generate those boxes.
A vented alignment is a continuum of possibilities. Now with a computer program you can explore all the possibilities."


Has anyone simulated step response in Unibox, and found they could employ the results to fine tune their design, ie go beyond SBB4, knowing in building a bigger box that they gained something tangible ?

Thanks
  Reply With Quote
Old 24th December 2006, 05:28 AM   #5
diyAudio Member
 
Join Date: Nov 2005
I certainly agree with the continuum comment. I don't use classic alignments as such, I mentioned SBB4 as a way to connect to the Cookbook. I use LEAP for modeling and do final tuning with the Sheffield drum record for minimizing overhang. Frequency response falloff is chosen to more or less match room gain.
  Reply With Quote
Old 24th December 2006, 07:24 AM   #6
diyAudio Member
 
Join Date: Dec 2002
Location: dry ol Melbourne Australia
Curmudgeon

Does LEAP allow simulating of step response, or do you think that could be worthwhile?

Cheers
  Reply With Quote
Old 25th December 2006, 06:52 PM   #7
diyAudio Member
 
Join Date: Nov 2005
Yes it does, but I don't use it; I used the delay curves instead. Nowadays, I tend to use the freq response more, and the delay curves a bit less, as I choose the driver and box size to put me in the SBB4 (or Extended Bass Shelf) territory to begin with. I did spend a lot of time the first time through the loop (10 years ago?) to decide that that was the "alignment" I wanted to use.

Oh, and to emphasize the Sheffield drum record; the notes say the kick drum should be totally dead. With a significant alignment error, I've heard it Baarooommm. When it is truly dead, the transient response (which is actually more lack of hangover I think) is very good. I don't think the disk is still available, and I don't know a substitute unfortunately.
  Reply With Quote
Old 25th December 2006, 07:55 PM   #8
diyAudio Member
 
Join Date: Feb 2004
Location: Queensland Australia
Hi rick57. greetings from the Sunshine State, I don't want to confuse things but you might reconsider going for a Qt of 0.7. I am aware that this number is frequnetly seen as the optimun and gives "Butterworth" or maximally flat response. On the other hand as the bass end there is a good case for a lower figure. My source is Martin Collom's book "High Performance Loudspeakers" (various editions since 1978. I think the 5th is the latest). He maintains that a figure of 0.6 gives a better subjective response. The maximally flat response tended to sound too bassy and loose. Its a v.good text and might repay checking out at a local library if you can get it. Enjoying the weather down there this week? I lived there during the 70's and can recall leaving a building in sunshine having a coffee in Lygon St Carlton and returning 75 minutes later. During that time it rained and snowed but the sun was shinning by the time I headed back. You've got to love it!
__________________
"It was the Springtime of the year when aunt is calling to aunt like mastodons bellowing across primeval swamps." P.G. Wodehouse.
  Reply With Quote
Old 25th December 2006, 07:58 PM   #9
TerryO is online now TerryO  United States
diyAudio Member
 
TerryO's Avatar
 
Join Date: Nov 2002
Location: Seattle,Wash.
Default Sheffield Drum Record

Quote:
Originally posted by Curmudgeon
~~~~~~~~~~Snip~~~~~~~~~

Oh, and to emphasize the Sheffield drum record; the notes say the kick drum should be totally dead. With a significant alignment error, I've heard it Baarooommm. When it is truly dead, the transient response (which is actually more lack of hangover I think) is very good. I don't think the disk is still available, and I don't know a substitute unfortunately.

Curm and any others,

If you want the Sheffield Drum record, it's available on CD and for sale by Winston Ma of FIM.

Go here: http://www.fimpression.com/detail.aspx?ID=85

HTHs,
TerryO
__________________
"If you have to ask why, then you're probably on the right track."
quote from Terry Olson's DIYaudio Forum application
  Reply With Quote
Old 25th December 2006, 08:52 PM   #10
diyAudio Member
 
Join Date: Nov 2005
Well, that's an interesting site! Thank you.
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Controlling transient response AdamZuf Tubes / Valves 29 6th July 2007 01:38 AM
Vented alignment to maximise transient response rick57 Multi-Way 31 3rd December 2004 06:12 AM
Transient response on underdamped sub with EQ mikee12345 Multi-Way 13 24th June 2004 11:41 PM
Transient Response Testing cm961 Multi-Way 37 22nd March 2004 09:57 AM
EBS transient response Solid Snake Multi-Way 1 1st February 2004 05:26 AM


New To Site? Need Help?

All times are GMT. The time now is 06:32 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