OB noob 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 13th March 2009, 03:44 PM   #1
Pault is offline Pault  Greece
diyAudio Member
 
Join Date: Sep 2008
Default OB noob question

First post here and it's a question(what else could it be?).It is my understanding that using a woofer in OB requires the driver to be of high Qts.Exactly how high is high enough?Am I missing something?Am I wrong?For example,an MTM OB configuration with 6,5" mids, what kind of drivers needs?What other specs of the driver are of big importance for OB designs?And what about 12" or 15" drivers?(Qts etc.).Thanks in advance!

Pavlos
  Reply With Quote
Old 13th March 2009, 03:53 PM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
big drivers with low to medium Xmax seem to perform well in OB.
sufficient small drivers giving adequate cone area should still be able to give good performance in OB.

Qts ~ 0.5 to 1 may work OK. But I've never built one for long term listening.

I have tried a 6inch coaxial designed for ceiling mounting in an 8foot by 4foot by 18mm board and was surprised at how well it played.
__________________
regards Andrew T.
  Reply With Quote
Old 13th March 2009, 08:30 PM   #3
diyAudio Member
 
Join Date: Jan 2002
Location: Puget Sound
Your mid requirements are tied to the width of your baffle and your desired woofer crossover point.
  Reply With Quote
Old 13th March 2009, 09:54 PM   #4
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally posted by ultrachrome
Your mid requirements are tied to the width of your baffle and your desired woofer crossover point.

Expect a small driver to be almost "dead" or at least attenuated below 300hz, which is also the BSC area
Just small losses at these frequencies leads to thin and boring sound
I believe in the old days it was often wrongly called analytical sound, but probably still is

So you need some exstra SPL in the midbass
Either with EQ
Or multiple woofers
2.5way may work, or may not due to phase issues from mid rolling off
Or use a bigger woofer with higher sensitivity

Im not sure how I would do it
It could be a big true dipole
Or it could be a smaller hybrid with boxed woofer

But even skilled people who thought it would be easy, have realised that it can be quite tricky and take quite a lot of work
Others seem to have been more "lucky" without much problems
__________________
sometimes we know very little, and sometimes we know too much
  Reply With Quote
Old 13th March 2009, 10:04 PM   #5
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Default Re: OB noob question

Quote:
Originally posted by Pault

For example,an MTM OB configuration with 6,5" mids, what kind of drivers needs?

And what about 12" or 15" drivers?(Qts etc.).Thanks in advance!

Pavlos

http://oaudio.de/media/products/0470...53.01%20PC.pdf

http://oaudio.de/Loudspeaker-chassis...W2-800::2.html

About 80EUR pr side may still want a sub though


And fore a real nice system you could use a preamp from HifiAkademie, with dsp eq and digital xo
Attached Images
File Type: jpg pre21.jpg (40.5 KB, 117 views)
__________________
sometimes we know very little, and sometimes we know too much
  Reply With Quote
Old 13th March 2009, 10:52 PM   #6
Pault is offline Pault  Greece
diyAudio Member
 
Join Date: Sep 2008
First of all, thank you for your answers.
I asked specifically for the mids because the project I have in mind is a WMTMW speaker,where only MTM is OB.For the woofers I'm thinking of these http://tymphany.com/830667 in a 60 ltr box tuned to 33Hz with a 12" Dayton PR and crossed at about 250Hz.As for the tweeter I guess the Peerless HDS should be fine.The mids are still a mystery.What do you think of this project?Is it doable or I'll end up banging my head against the wall?
  Reply With Quote
Old 13th March 2009, 10:52 PM   #7
Pault is offline Pault  Greece
diyAudio Member
 
Join Date: Sep 2008
BTW Tinitus these drivers seem quite interesting.As for EQing I'll probably use a Behringer DEQ.
  Reply With Quote
Old 13th March 2009, 10:59 PM   #8
Rudolf is offline Rudolf  Germany
diyAudio Member
 
Rudolf's Avatar
 
Join Date: Mar 2003
Location: Germany
Default Re: OB noob question

Quote:
Originally posted by Pault
[B]It is my understanding that using a woofer in OB requires the driver to be of high Qts.Exactly how high is high enough?
You can build a dipole with any Qts you want. But: Practically you need to equalize any driver until its frequency response behaves like a driver with at least Qts=1. For Qts from 0.7 up the variable bass boost of many subwoofer modules will be sufficient. Drivers with Qts >0.9 probably will do without special EQ. When going above Qts=1.2 things will start to get worse again.

Quote:
Am I missing something?
The primary and limiting factor is not Qts, but the drivers ability to move air. The product of Sd and Xmax should be at least 4 times bigger than for the woofer in a CB you find sufficient for your room.

Quote:
For example,an MTM OB configuration with 6,5" mids, what kind of drivers needs?
In that configurations the mids are no problem. You will have a harder time to find an equivalent tweeter.

Quote:
What other specs of the driver are of big importance for OB designs?
You need to look for "silent" woofers. No ringing baskets and chuffing pole vents. There is quite some background noise that can be subdued by a box but might get annoying in an OB.

Quote:
And what about 12" or 15" drivers?(Qts etc.).
Serious OBs start with double 12" or single 15" woofers. If you want lots of headroom think about 21". 8" or 10" drivers may be an option for dipole line arrays.
__________________
www.dipolplus.de
  Reply With Quote
Old 14th March 2009, 01:15 AM   #9
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally posted by Pault
BTW Tinitus these drivers seem quite interesting.As for EQing I'll probably use a Behringer DEQ.

Whether those Omnes/TB drivers are adequate or not, they may tell you something about whats needed

Trick of it is as Rudolf touches...in a MTM its important to cross low, and the 2" TB may be used down to about 1khz, where impedance begins to rise, maybe best crossed just a little higher

A TB 4" ti ought to be good as tweeter too, and could b crossed even lower, but cost more
I have read that it sounds nice fullrange, but have to try it first...and I will
If unable to cross that low, I would consider a single mid

AND it would be true dipole, which a dome tweeter is not

I would maybe consider a cheap supertweeter like the small Fountec CD1.0MB(cost only 38EUR)


If you really like the HDS tweeter, it might work nicely with just a single Eminence Beta-8A...or maybe two in a 2.5way, and consider a small "waveguide" fore the HDS
But dont know really...
Would also work in a box, with actiive subs
__________________
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
one noob question.. ryan750 Subwoofers 3 12th May 2009 10:04 AM
Noob Question -.- fr1s Chip Amps 6 25th February 2009 07:47 PM
Very noob question snails07 Chip Amps 10 7th October 2008 11:42 PM
Noob Question USlatin Everything Else 3 13th November 2007 05:01 PM
noob I2S question p_ete2003 Digital Source 6 19th May 2004 05:51 AM


New To Site? Need Help?

All times are GMT. The time now is 10:39 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