B20 on Open Baffle - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Vendor's Bazaar

Vendor's Bazaar Commercial Vendors large & small hawking their wares

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 19th January 2010, 05:56 PM   #1
diyAudio Member
 
Godzilla's Avatar
 
Join Date: Nov 2005
Location: New York
Default B20 on Open Baffle

This sounds really good! It's a Pioneer B20 on an open baffle. The woofers are Alpha 15 and the tweeter is an Eminence using the small Dayton waveguide. The woofers are crossed at approx 75Hz and the tweeter is at about 11kHz.

I will be selling this as a kit at a reduced price than buying everything separately but have not figured the price yet. Once the plans are drawn out i will offer them free so you can purchase the components from anywhere you want, build and modify.

Without sounding like all i want to do is sell the kit i must say this is a very nice sounding speaker. I have been enjoying these for weeks and feel they are a great way to implement the Pioneer B20. If you like this driver you will love it with the added tweeter and woofers. From top to bottom it's very enjoyable. Open baffle removes any boxy coloration, the soundstage is wide with instruments and vocals floating in space rather than emanating from a box. Pink Floyd the Wall will creep you out (and your kids) and large scale orchestral music really sounds like a large orchestra. I will provide more details later.

Godzilla
Attached Images
File Type: jpg B20-Boomer.jpg (42.8 KB, 436 views)
  Reply With Quote
Old 19th January 2010, 06:39 PM   #2
diyAudio Member
 
InclinedPlane's Avatar
 
Join Date: Jan 2007
Location: Maine
75hz 6db?
__________________
I must confess my favorite music is that made by the Rolls Royce Merlin.
  Reply With Quote
Old 19th January 2010, 09:00 PM   #3
diyAudio Member
 
Godzilla's Avatar
 
Join Date: Nov 2005
Location: New York
>>> 75hz 6db?

The woofers roll off at 18db.

Godzilla
  Reply With Quote
Old 19th January 2010, 09:28 PM   #4
diyAudio Member
 
InclinedPlane's Avatar
 
Join Date: Jan 2007
Location: Maine
Huh. I figured you'd have a hole in your midbass with that alignment. But apparently not.
__________________
I must confess my favorite music is that made by the Rolls Royce Merlin.
  Reply With Quote
Old 20th January 2010, 01:11 AM   #5
2litre is offline 2litre  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Bremerton, WA.
Good to see someone has finally tried this

Given that the B20's list at 90db and the Alpha at 97db (an MJK OB friendly set of numbers there), what made you cross so low?

R/
Jim

Last edited by 2litre; 20th January 2010 at 01:13 AM.
  Reply With Quote
Old 20th January 2010, 01:33 AM   #6
diyAudio Member
 
InclinedPlane's Avatar
 
Join Date: Jan 2007
Location: Maine
Well keep in mind the Alpha is, according to Eminence's infinite-baffle loaded plot, 90 db at 75hz. The OB that Zilla is using would reduce that even more, but probably not much more. My concern would be that since the B20 is comparatively inefficient, the 100-200hz area might suffer a little considering that cancellation still does occur that high. BUT, this could probably be filled with room reinforcement, preventing the kind of midbass vocals-destroying bloat that I loathe.
__________________
I must confess my favorite music is that made by the Rolls Royce Merlin.
  Reply With Quote
Old 20th January 2010, 01:54 AM   #7
2litre is offline 2litre  United States
diyAudio Member
 
Join Date: Jul 2005
Location: Bremerton, WA.
InclinedPlane,

Looking at the response graph here:
http://www.eminence-speaker.com/pdf/alpha-15a.pdf
I see what you mean about SPL @75Hz.

But what do you mean about "cancellation still does occur that high"?

R/
Jim
  Reply With Quote
Old 20th January 2010, 02:45 AM   #8
diyAudio Member
 
InclinedPlane's Avatar
 
Join Date: Jan 2007
Location: Maine
Baffle losses, where the front wave is meeting the backwave and partially 'canceling each other out'.
__________________
I must confess my favorite music is that made by the Rolls Royce Merlin.
  Reply With Quote
Old 20th January 2010, 02:47 AM   #9
MJK is offline MJK  United States
Account disabled at member's request
 
Join Date: Feb 2002
Location: Clifton Park, NY
Quote:
Originally Posted by 2litre View Post
Looking at the response graph here:
http://www.eminence-speaker.com/pdf/alpha-15a.pdf
I measured the T/S parameters for the Alpha 15A and found it to be 92.4 dB/W/m. Due to the Qts of over 1.0, the driver should be flat down to fs on an infinite baffle. The geometry of an OB will start to eat away at this SPL value as a function of size.

The 97dB/W/m quoted on the spec sheet is probably a peak value. The SPL curve shown must be for the driver in a box of some kind, it is totally inconsistent with a driver that has an fs of ~40 Hz and a Qts of ~1.2.

Be careful with manufacturer's spec sheets.
  Reply With Quote
Old 20th January 2010, 05:28 AM   #10
diyAudio Member
 
Godzilla's Avatar
 
Join Date: Nov 2005
Location: New York
It sounds funny to say the crossover is at 75hz and incorrect actually. Remember, i have an amp connected to the woofers. The woofers have a rising response so when adjusting the variable crossover the setting is at approx 75hz on the dial but the actual crossover is probably closer to 200hz. Tomorrow i will post a pic of the woofers simmed response and it may make more sense why the settings are what they are. Everything sounds great without any holes... probably more overlap between drivers than gaps. Also, the amp raises and lowers the overall volume of the woofers. So once the crossover is set to blend the woofers into the B20 then you can raise and lower the volume to adjust further. It's really just like setting up a powered subwoofer but in this case you have two 15" woofers.
Godzilla
  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
Does open baffle suffer from baffle step? 454Casull Multi-Way 15 19th May 2012 04:12 PM
Pioneer B20 open baffle -- popular tweeter jmar Full Range 22 24th June 2011 02:27 PM
Murphy baffle radios [ open baffle ] keithpeter Full Range 10 11th September 2007 08:59 PM
what effect does baffle have on open-baffle system? kappa546 Multi-Way 6 24th January 2006 11:21 PM
Australians- what solid timbers for baffle? (open baffle loudspeaker) tktran Multi-Way 13 30th November 2004 12:09 AM


New To Site? Need Help?

All times are GMT. The time now is 09:07 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