Extrapolating Daveís baffle step compensation approach? - 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 17th July 2008, 02:43 PM   #1
diyAudio Member
 
otto88's Avatar
 
Join Date: Dec 2007
Default Extrapolating Daveís baffle step compensation approach?

Dave outlines six methods of dealing with baffle step loss: http://www.t-linespeakers.org/tech/b...intro-bds.html

Baffle step compensation in a typical crossover varies from 3 to 5.5 dB, gaining flat response at the loss of sensitivity. Especially with lower powered amps (tubes, class D) itís desirable to maximise sensitivity . .

Dave's favorite approach (above) adds a further mid-woofer on the back (bipole).

If BSC was left out of a 2 way's crossover, and instead of adding a mid-woofer, a sub were added with an active crossover (eg a Behringer DCX 2496) having shelf filter abilities, with tweaking of the shelf filter and phase, would you agree that the subs could provide the compensation for the baffle step loss; so the sensitivity could be raised.

Eg with Jayís MTM Usher 8945P / Peerless HDS http://www.geocities.com/woove99/Spk.../Usher_MTM.htm , sensitivity could be

Usher averages 87 + 6 (two drivers) = 93 dB
Peerless averages 93 dB

A trade off is that 200 Hz is into the range of eg voices. But with
low powered amps to gain 6 dB, thatís not necessarily a major deficit . .
A benefit is that as the bass load of the mid-woofer is greatly reduced, they should preform better . .
A sub would also go deeper.

What do you think?
  Reply With Quote
Old 17th July 2008, 03:02 PM   #2
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Default Re: Extrapolating Daveís baffle step compensation approach?

Quote:
Originally posted by otto88

would you agree that the subs could provide the compensation for the baffle step loss...........

A trade off is that 200 Hz is into the range of eg voices.
Works for me as long as the 'sub' driver has a wide enough BW to be nominally flat through the XO BW with no strong break up modes above it. I do the same thing except with a 500 Hz/2nd order XO.

Not much of a trade-off if you look at how poor our hearing acuity is down low........... I mean look at a phone's BW, its low cut-off is 250 Hz.........

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 17th July 2008, 03:32 PM   #3
diyAudio Member
 
otto88's Avatar
 
Join Date: Dec 2007
Default max Hz from a sub

Most want to XO subs at 40 - 80 Hz, that seems a waste.

Most good subs are very clean way beyond that, eg an engineer at the former Peerless (now Tympani) said that the XLS 12 driver with a 4th order XO could be crossed at up to 300 Hz

So i'm right that sensitivity is gained for the mid-woofers . . and there are no other drawbacks?
  Reply With Quote
Old 17th July 2008, 05:27 PM   #4
sreten is online now sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

The Watt / Puppy did this yonks ago albeit with stereo subs.
(and proper high pass filtering of the mid unit to boot)

see http://www.deadwaxcafe.com/vzone/david/david.htm

FWIW it is also one of the many ways of implementing a 3-way
speaker. a 3 way can be designed with BSC in the bass, in the
mid, or shared between the two in any ratio. No wonder then
that people get 3 ways so badly wrong, except for sub + sats.

/sreten.
  Reply With Quote
Old 17th July 2008, 09:15 PM   #5
pjpoes is offline pjpoes  United States
diyAudio Member
 
Join Date: Jan 2005
Location: New York
Send a message via AIM to pjpoes
I think I must be a little confused. I mean bass is too directional by 300-500hz, thats lower midrange territory. You wouldn't want a single subwoofer centrally placed acting as baffle step. If it was included into the main speakers, then yeah, but at that point, we are talking about a fairly common 3-way approach. I'm thinking I must be misunderstanding what you are asking, so please correct me here.
  Reply With Quote
Old 17th July 2008, 09:34 PM   #6
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
There's a lot to be said AGAINST using subs for 300Hz. In addition to localization issues, there's lobing, poor transient response and breakup suppression concerns, and other stuff.

If you want the bass driver to run that high, a good solution is to pick a passive driver with the extra 3dB of sensitivity, and use it as a woofer proper, with an XO at the bafflestep frequency (assuming passive XO).

But using subs.... just asking for trouble. If you like muddy mids, it's a fine solution. Subs are best crossed LOW LOW LOW, to keep them out of the more sensitive ranges of our hearing, and from interfering with any but the deepest of instrumental fundamentals.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 18th July 2008, 12:26 AM   #7
diyAudio Member
 
otto88's Avatar
 
Join Date: Dec 2007
pjpoes
I didnít say stereo subs, because I thought any (sensible) use of subs over about 80 Hz would be stereo, my oversight.

I only mentioned 300 Hz because a Peerless engineer said that their XLSís would go that high. Iím assuming for the time being that baffle step would occur around 200 Hz +/- 50 Hz.


Sreten
A tad off topic, but in the Watt / Puppy, what did you mean by *proper high pass filtering of the mid?

badman
> localization issues, there's lobing, poor transient response and breakup suppression concerns, and other stuff
Are you assuming a mono sub: if not, can you elaborate?

The drivers I want to use - because I have them, and they achieve a higher efficiency tube friendly result are:

Tweeter: Peerless HDS 810921 (used in eg the Elsinore and Jayís systems with Ushers) 93 dB
Mid: a B&C (cant recall model, Fs I know is 117 Hz) ~ 95 dB
ďbass/ subĒ: Eminence Kappa Pro ~ 95 dB

If used up to say 250 Hz, how would the Eminence muddy the sound?


One thing thatís since occurred to me is that reasonable inductors at say 250 Hz would cost a bit, thoí I have no idea how much.
  Reply With Quote
Old 18th July 2008, 12:34 AM   #8
diyAudio Member
 
Join Date: Aug 2006
Sounds like the beginings of a typical 3 way, and I would design it as such.

Considering excursion and response capabilities of both woofer and mid, driver placement vs listening position, crossover slopes, baffle size, etc.

__________________
~Brandon
DriverVault Soma Sonus Old Driver Tests
  Reply With Quote
Old 18th July 2008, 01:23 AM   #9
pjpoes is offline pjpoes  United States
diyAudio Member
 
Join Date: Jan 2005
Location: New York
Send a message via AIM to pjpoes
I actually would consider a 3.5 way or a 3 way. The setup may be too efficient in the bass if designed as a typical three way. If you want higher impedance in the bass, you could wire the woofers in Series, then design as a typical 3 way. But really, I think a 3.5 way would be a potential option.

I don't agree that there will be any problems such as lobing. This design will actually work quite well I think, and you could run those drivers higher if you wanted. I would have no problem running those woofers to 500hz. To be honest, I think they don't begin having lobing problems until around 1khz or maybe just below that.

If you need any help with some overall topologies let me know. I can post some schematics. Without the drivers themselves I couldn't give you exact values for the parts, but it would get you started. If you do have measurements, and just need help with the crossover, then you can send me the files and I can see what I come up with.
  Reply With Quote
Old 18th July 2008, 04:05 AM   #10
diyAudio Member
 
otto88's Avatar
 
Join Date: Dec 2007
Yes my thinking evolved from a 2way with mid-woofer, but itís a 3 way with the ďbottomĒ active.
So a few 3 ways use the bass driver with a shelf filter for BSC?

pjpoes
Possibly I might end up running those 12Ē Eminences to 500 Hz, they should handle that easily enough; itíll be by trial. .

Can anyone throw a rough cost on reasonable inductors at say 250/ 300/ 400 Hz??

Thanks
  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
When to use baffle step compensation? tmblack Multi-Way 28 6th December 2008 01:39 PM
Short TL as Baffle Step Compensation m@ Multi-Way 0 10th March 2008 10:07 AM
Baffle step compensation formula? bart_dood Full Range 4 8th July 2006 11:50 AM
Baffle Step Compensation Khron Multi-Way 4 16th April 2006 09:23 PM
Baffle step compensation in an active X/O sunil Multi-Way 0 26th October 2003 09:47 AM


New To Site? Need Help?

All times are GMT. The time now is 02:47 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