Asymmetrical crossover question - 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 12th August 2009, 05:52 AM   #1
diyAudio Member
 
gainphile's Avatar
 
Join Date: Dec 2007
Location: Melbourne the sunny city!
Default Asymmetrical crossover question

I'm new to asymmetrical XO. Usually I just use textbook XO.

Below is a picture of P13WH woofer measured nearfield (ignore the SPL). It follows either bessel or LR 2nd order highpass filter, almost perfectly.

The question is: Is it reasonable to simply let the driver rolloff by itself (no xo) and for the woofer I apply 2nd order lowpass LR (red curve on left).

What about the phase issue?
Attached Images
File Type: jpg assy.jpg (82.4 KB, 258 views)
__________________
http://gainphile.blogspot.com
  Reply With Quote
Old 12th August 2009, 06:13 AM   #2
CLS is offline CLS  Taiwan
diyAudio Member
 
Join Date: Jun 2005
Location: Taiwan
Somewhat confused here.

My understanding would be: you'll use this P13WH "woofer" as a mid, and add "another woofer" by <2nd order lowpass LR (red curve on left) >.

If so, I'd like to have at least the simplest HP filter to help reducing the cone excursion of the mid driver and forget about the symmetry of xo slopes.
  Reply With Quote
Old 12th August 2009, 06:44 AM   #3
diyAudio Member
 
gainphile's Avatar
 
Join Date: Dec 2007
Location: Melbourne the sunny city!
Hi CLS,

Correct. I'm actually happy with the excursion issue as I don't play music that loud.

I guess I just have to build and measure the response and see if it's summed properly.
__________________
http://gainphile.blogspot.com
  Reply With Quote
Old 12th August 2009, 06:54 AM   #4
ttan98 is online now ttan98  Australia
diyAudio Member
 
Join Date: Apr 2006
Location: Melb
Try this Thread,

http://techtalk.parts-express.com/sh...20&postcount=1

you may find it useful.

Cheers.
  Reply With Quote
Old 12th August 2009, 07:02 AM   #5
ttan98 is online now ttan98  Australia
diyAudio Member
 
Join Date: Apr 2006
Location: Melb
Try this Thread,

http://techtalk.parts-express.com/sh...20&postcount=1

you may find it useful.

Cheers.
  Reply With Quote
Old 12th August 2009, 09:29 AM   #6
rabbitz is offline rabbitz  Australia
diyAudio Member
 
rabbitz's Avatar
 
Join Date: Jul 2003
Location: Newcastle, Australia
For that to work the best IMO is to use a 1st order on the woofer with an oversize zobel to help with the roll off (shape) a couple of octaves past the crossover point. It's sort of how 0.5 woofers work but in this case with different sized drivers.

I've used this method several times with great effect and helps with overall BSC. Room gain on the woofer tends to fill in the gap below the P13 roll off say below 80Hz. The downside is the impedance will drop due to the 2 drivers in parallel. I've had no excursion problems doing it this way and can be assisted by the enclosure design restricting driver excursion.

Using a 2nd order on the woofer would give worse results IMO and would not have as smooth a transition and would have worse phase and summing.

Using 2nd order on both may require reversed polarity on the P13 to ensure correct phase and summing but technically would be the best for a true 3-way design.

Depends on the behaviour of the woofer (mid capability) and how quick you want to get it to dive. It's nice not to have a large (say 120-250uF) cap in front of the P13 by allowing a natural acoustic roll off.
__________________
No longer DIY active
  Reply With Quote
Old 12th August 2009, 11:48 AM   #7
diyAudio Member
 
gainphile's Avatar
 
Join Date: Dec 2007
Location: Melbourne the sunny city!
Thank you all for the advise. That link is very interesting read indeed.

The P13 is on open baffle and textbook crossover did not materialise nicely due to driver rolloff. It resulted in somewhat thin sound.

I implemented the xo tonight and it actually worked!. P13 is able to cope with quite loud SPL, and even with shelving filter down to 60Hz for dipole compensation. It does work hard

The phase did create issue, quiet tiring to listen. After few read I calculated that the induced -90 degrees phase shift on the woofer is worth about 60cm. I did not have the space and moving back my h-frame woofers 45cm seems to be good enough. I know it's not coherent due to no XO on the mid, but we'll see whether this stands longer listening test.
__________________
http://gainphile.blogspot.com
  Reply With Quote
Old 12th August 2009, 12:52 PM   #8
rabbitz is offline rabbitz  Australia
diyAudio Member
 
rabbitz's Avatar
 
Join Date: Jul 2003
Location: Newcastle, Australia
OB

Yes that changes the game. Have to allow for additional 1st order roll off under Fe and a rise of around 6dB to Fp.

I remember having to play around with polarity of the mid and woofer in an OB I did. IIRC the woofer ended up reversed with the mid normal.
__________________
No longer DIY active
  Reply With Quote
Old 13th August 2009, 04:39 AM   #9
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Surpricing that your small midwoofer doesnt seem to have the dipole related rolloff
__________________
sometimes we know very little, and sometimes we know too much
  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
cascode vs asymmetrical cathode coupled oldeurope Tubes / Valves 47 18th April 2008 05:37 PM
Asymmetrical P-P OPT Primary rdf Tubes / Valves 14 11th March 2007 11:46 PM
Asymmetrical amplifier Thoru Solid State 0 26th January 2004 07:00 PM
Aleph asymmetrical clipping? (help) panos29 Pass Labs 9 8th October 2003 11:54 AM
crossover question Rodtay Multi-Way 3 7th August 2003 12:35 PM


New To Site? Need Help?

All times are GMT. The time now is 08:29 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