Two drivers one selaed box - 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 4th September 2007, 02:45 PM   #1
diyAudio Member
 
Join Date: Nov 2005
Location: Mauritius
Default Two drivers one selaed box

Hi could anyone please help on this:-

I am planning to build a sealed subwoofer with two drivers in it. The drivers share the same volume. The drivers will be equalized with a linkwitz transform circuit.

My question is how do i measure the Q parameters for the woofers in the sealed box for the linkwitz transform:

do i

1) Measure the parameter for one woofer and multiply the Vas by 2?

2) Or connect each woofer in parallel and measure the total Q values? ( Note that each driver will have its own amp and the amps are driven by a linkwitz 24 dB/Octave active low pass filter)

Thanks for the help
  Reply With Quote
Old 4th September 2007, 02:51 PM   #2
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Hi,
Measure both driver and average the results. Use Unibox, set for two driver in either series or paralell, with the average parameters. Unibox will do the rest.
  Reply With Quote
Old 4th September 2007, 04:15 PM   #3
diyAudio Member
 
Join Date: Nov 2005
Location: Mauritius
Default DRiver configuration

Hi thanks for the reply i will try to look for unibox. But actually each driver is run by its own amp they are not connected together neither in parallel nor in series. So is it still valid to consider theT/S parameter of one driver only (measured in the box with both drivers present) and used these values for the linkwitz transform?

Thanks
  Reply With Quote
Old 4th September 2007, 04:32 PM   #4
Account disabled at member's request
 
MJL21193's Avatar
 
Join Date: Mar 2007
Ok, first things first: You need the T/S specs to design the enclosure. I measure these with Speaker Workshop to get Fs (free air resonance), Qms, Qes, Qts and Vas. The driver needs to be measured in free air, not in the box. I mass load the cone to determine the Vas.

To design the enclosure with Unibox, two drivers in paralell or series electrically makes no difference to box volume or tuning. You need the Fb and the Qtc of the box to determine the values for the Linkwitz transform. Fb should be near the top of the desired frequency range of the sub, to drive the speakers below this resonant peak.
For example:
2 subs with Fs = 35 installed in a 40 litre box gives an Fb of 80Hz(this is just a for instance example, not real data).
Below 80Hz, impedance is flat, easy load for the amp to drive.
Having the box small enough to drive Fb up is one of the biggest advantages of the Linkwitz transform.
  Reply With Quote
Old 5th September 2007, 03:03 AM   #5
y8s is offline y8s  United States
diyAudio Member
 
y8s's Avatar
 
Join Date: May 2006
Send a message via AIM to y8s Send a message via MSN to y8s Send a message via Yahoo to y8s
Quote:
Originally posted by MJL21193
[B]Ok, first things first: You need the T/S specs to design the enclosure.
nah he doesn't need them prior to building if he's doing a linkwitz transform. Sure you need to be in the ballpark so your max gain isn't too high, but the point of the L-T is to make a random box behave like a better-than-perfect box. just measure the drivers in their box after it's all built and use that Q and Fs.

matt
  Reply With Quote
Old 5th September 2007, 04:02 AM   #6
diyAudio Member
 
Join Date: Nov 2005
Location: Mauritius
Default still same question

Hi thanks for your replies the steps you have mentionned have already been done. So to make it simpler with the two drivers in the same box do i connect only one driver and measure the Fs and Qts or both of them?
  Reply With Quote
Old 5th September 2007, 02:44 PM   #7
y8s is offline y8s  United States
diyAudio Member
 
y8s's Avatar
 
Join Date: May 2006
Send a message via AIM to y8s Send a message via MSN to y8s Send a message via Yahoo to y8s
connect them as you would during normal use. you'll want the "system" response and that's how the system will be used.

the L-T will be fed into the amplifier driving the two drivers, correct?
  Reply With Quote
Old 6th September 2007, 06:55 AM   #8
diyAudio Member
 
Join Date: Nov 2005
Location: Mauritius
YEs Y8S the same linkwitztransform will be fed into both amps

So to sum up i put both woofers in the box. Connect only 1 woofer. Measure the T/S parameters and use the measure parameters in the linkwitz transform and it should work.
  Reply With Quote
Old 6th September 2007, 06:02 PM   #9
y8s is offline y8s  United States
diyAudio Member
 
y8s's Avatar
 
Join Date: May 2006
Send a message via AIM to y8s Send a message via MSN to y8s Send a message via Yahoo to y8s
ohh two amps.

I would still do them together. both running, both measured. you're only making one linkwitz transform, correct?

source -> LT => amplifiers => woofers

the LT doesn't know how many woofers or amps there are, it just knows the system Q and Fs. Measure the system response with the same source into both amps and woofers and use that.

If you hook up only one woofer in a box with two woofers, the second "dead" woofer will interact and give you improper response curves.
  Reply With Quote
Old 6th September 2007, 06:15 PM   #10
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
If you are using an amp per woofer I would put a partition between the drivers to make two equal boxes. Then as you are using only one LT I would either measure each woofer individually and average the results to design the LT, or connect them in parallel or series and measure that way.

If you do not have a partition sealing each half you cannot only measure one woofer leaving the other unpowered. The results will be completely screwed as the undriven woofer tries to be a passive radiator.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  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
JBL comp drivers, Dayton Reference Sub drivers for auction NO RESERVE pkpickard Swap Meet 1 21st January 2009 03:19 AM
FS: x25 Vifa 5" Drivers + x2 Diamond Audio 5.6 Hex Eton Drivers omarmipi Swap Meet 0 19th November 2007 04:21 AM
Two 10" drivers selaed sub zeus_threat Subwoofers 15 8th November 2007 07:03 PM
21" Bass Drivers and Beyma Compression Drivers Magnetar Swap Meet 0 19th November 2006 02:42 AM
Open-Baffle dipoles...a heresy to pair PA drivers w/ home drivers? thadman Multi-Way 7 11th November 2006 09:11 PM


New To Site? Need Help?

All times are GMT. The time now is 03:02 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