Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Are you (open) baffled yet?
Are you (open) baffled yet?
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 8th September 2003, 02:05 PM   #21
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by phase_accurate
Is that a Beauhorn in the background ? How does it compare to your open-baffles ?
The smaller Beauhorn on it's own sounds very coherent, well balanced with perhaps a somewhat overly "fat" bottom. The Bastanis Prometheus manages a much wider bandwidth, better detail and much greater dynamic range (plus sensitivity), but slightly the cohesiveness of the Beauhorns (maybe more tweaking will bridge the gap...).

Sayonara
  Reply With Quote
Old 8th September 2003, 02:34 PM   #22
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa Cat San,

Quote:
Originally posted by Romy

So are any Web sources that you might suggest with the calculation of the open baffles?
Not really. I have pretty reasonable Spreadsheet that gives a good idea how things work, in room. The first thing to note, you require a driver with a Qts of 0.5 or higher to stand any chance of balanced sound.

If the driver has a Qt of 0.5 the output on an INFINITE baffle will be 6db down at the drivers resonance. Using a Driver with a Qt of 0.7 the output will be down 3db at resonance. Using a Qt of > 0.7 will result in a certain peaking of the driver output around Resonance, which can be used to offset the reduced output from open baffle mounting.

So, the baffle size needed relies on a complex relationship. Drivers with a Qt < 0.7 could be said to benefit more or less from as large a baffle as possible (within limits).

The second thing is that Olsons formulas for baffle width are inaccurate. For a simple "ballpark" idea, a plan Baffle with an assymetrically placed driver and a total circumference (all edges of the baffle measured) of 140cm (eg 27cm wide and 44cm high) will provide a +3db peak centered around 400Hz and will have
a -3db point of around 100Hz for the BAFFLE ONLY. The frequency scales with size.

SO if we had a driver with an Fs of 100Hz and a Qt around 1.0 (say a classic German Saba "Greencone" 8" Radio Full range Speaker) on the above baffle the result would be a speaker with a response flat to around 100Hz and then rapidly rolling with a slope a little steeper than 3rd order.

Now if we had a driver on the same baffle with a Qt of 0.2 and an Fs of 56Hz (say a Lowther DX2) we would have a system that is around 12db down @ 100Hz compared to the Midband sensitivity and rolls off below with a slope closer to 2nd order than to third order.

For reference, the Bastanis woofer on the baffle has around 50Hz Fs & a Qt of 0.6, meaning on an infinite baffle the driver will be 4 - 5db down @ 50Hz. The Bastanis Baffle is 36cm X 110cm giving a -3db point of around 50Hz, so as system the Baffle & Driver is around -7...-8db down @ 50Hz and around -2db @ 100Hz, all based on Backmanns analysis & classic TS parameter analysis, but seemingly in line with what I heard ( I have yet to make comprehensive measurements.

I hope this gives some basic datapoints for your work.

Sayonara
  Reply With Quote
Old 8th September 2003, 05:42 PM   #23
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by fdegrove
Le vin est un Chateau Bricolo d'un excellent millesime..j'ose esperer.
Well, it was some french 2000 Vintage Bordeux. Nothing to write home about....

Quote:
Originally posted by fdegrove
On a more serious note, alot of credit should go to Steen Doessing of SD acoustics for bringing both OB design and bi/tri wiring back to our attention.

I've owned a pair of OBS2 by SD Acoustics and would like to point to the importance of proper baffle design.

The baffle should be made asymmetrical IMO to reduce IMD.
Hmmm. I agree in principle on the Asymmetry, but the Bastins Speaker has basically a minimal baffle. It makes for a fairly elegant visual design, but less ideal acoustically. Had the baffle been about twice as wide the Subwoofer may very well have become optional....

Quote:
Originally posted by fdegrove
Steen designed an OBS threeway which I can recommend to anyone.
It comprises a bass-reflex rear firing port woofer, the OBS midrange and a ribbon tweeter by Visaton.
I considered buying one of these from a 2nd Shop once, but they wanted silly money. Midrange was a modified Audax PR170M0 IIRC and the woofer also Audax.

Quote:
Originally posted by fdegrove

Some really nice stuff you have there, TL.
Thanks. BTW, the Bastanis Speakers have surprised me (and a friend) by just HOW GOOD they are....

Of course, haveing 50W EL34 Push-Pull Penthode Watts available makes for an absolutely SILLY dynamic range on these around 96 - 97db/W/m sensitive speakers.... When playing one of the big warhorses (Mahler Thousand, Saint Saen Organ Symphony or my personal Killer favourite Mussorskys "Pictures" on Reference) I am grinning madly, just as on the 15" Tannoys.

Sayonara
  Reply With Quote
Old 8th September 2003, 05:47 PM   #24
Romy is offline Romy  United States
Banned
 
Join Date: Sep 2003
Location: Boston, MA
Sayonara,

Unfortunately I have no knowledge about the Qt and Fs of my drivers but I got the picture, thanks.

Rgs,
The caT

PS: Try to tune yourself off from the Mussorsky’s orchestral version of the "Pictures…" This work is as vulgar in its orchestral rendering as musicality could theoretically be.
  Reply With Quote
Old 8th September 2003, 07:26 PM   #25
Rudolf is offline Rudolf  Germany
diyAudio Member
 
Rudolf's Avatar
 
Join Date: Mar 2003
Location: Germany
Default I´m still wondering what ...

Kuei

thank you for your calculation guidelines. Your spreadsheet seems to be much in line with the practical experience of people as I gathered it from the internet.

Since you emphazise the plan nature of the baffle:
How would you account for any backfolded parts of the baffle like the small wings on the Prometheus?
If I take (as an extreme example) a V-shaped baffle like in the illustration below (view from top) - what distance would be entered in the calculations? The green, blue or red one? Since dipole theory is all about the time difference between the front and back waves of the speaker at the hearing position, the red distance seems to be the valid one. Any ideas about that?
Attached Images
File Type: gif shape.gif (995 Bytes, 5678 views)
__________________
www.dipolplus.de
  Reply With Quote
Old 8th September 2003, 07:33 PM   #26
Bricolo is offline Bricolo  France
diyAudio Member
 
Bricolo's Avatar
 
Join Date: Nov 2002
Location: Grenoble, FR
Quote:
Originally posted by Kuei Yang Wang
Konnichiwa,



Well, it was some french 2000 Vintage Bordeux. Nothing to write home about....


Sayonara

If you still have some bottles of it, keep them 5 years. 2000 was a good yead, but it's too young to be drunk now
  Reply With Quote
Old 8th September 2003, 11:56 PM   #27
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Re: I´m still wondering what ...

Konnichiwa,

Quote:
Originally posted by Rudolf

thank you for your calculation guidelines. Your spreadsheet seems to be much in line with the practical experience of people as I gathered it from the internet.
No profit or recognition to me. Planet 10 send me a copy of Backmans article, I eventually coded the formulas into a decent Excel approximation, no creativity involved.....

Quote:
Originally posted by Rudolf

Since you emphazise the plan nature of the baffle:
How would you account for any backfolded parts of the baffle like the small wings on the Prometheus?
The small wings have the ability to slightly increase the wave radius. Once you take a wave as (sort of) spherical you realise that (short) folded back wings are acoustically nearly invisible. I fitted them merely to make sure the bleedin things stand stable....

Quote:
Originally posted by Rudolf

If I take (as an extreme example) a V-shaped baffle like in the illustration below (view from top) - what distance would be entered in the calculations? The green, blue or red one?
Non of the above. Draw in a spherical wavefront co-inciding with the driver center.

Quote:
Originally posted by Rudolf

Since dipole theory is all about the time difference between the front and back waves of the speaker at the hearing position, the red distance seems to be the valid one.
Almost, except that waves are not square, but spherical....

Sayonara
  Reply With Quote
Old 9th September 2003, 01:05 AM   #28
Romy is offline Romy  United States
Banned
 
Join Date: Sep 2003
Location: Boston, MA
Dear, Mr. Wang

Perhaps you would suggest if the direction I looks is achievable.

I am kind of multi-ways-multi-amps kind of guy and what I am thinking is not something that would substituted my main system but I am kind of look at this project as a complementary system. Nop, not the second system (the notion that I reject religiously) but something that would be melted within my main installation….

I would like to build a mono active speaker that would be able to work from my line level and to cover from 100Hz and up. I am in pursue of the very SPECIFIC AND INTENTIONAL SONIC QUALITIES/ATTRIBUTES with this mono system and now I feel I eventually have found/collected/stolen all ingredients that I need.

The system is 2 ways. The mids will are cared full range by a pair of the 12” active coil 1938 Telefunkens (got two in mint condition) connected in series. The HF will unavoidable 120 degree T350, kicking in at 7kHz with a first order. It driven by two stages with a penthod outside (AM2+AL4) plumbing 8W. The sensitivity altogether will be around 109dB (with 10dB killed in the tweeter).

I certainly would like to make the open baffle as small as possible but here is a dilemma. The 12” Telefunkens 1938 in open air run down to 500hZ and die very sharp. In a sealed enclosure it run very smoothly down to–3 dB at 600 Hz and –6 dB at 100 Hz and then depart from life very quick. The geniuses from Telefunkens found the way to boost 15dB at 150 Hz by placing this driver in their open boxes of those radios from end of the 30s. You have to hear how those enclosures sound themselves just when you knock on them! Those enclosures from those radios sound like an Amati from 1651! I am not kidding! The tone that those Teles enclosure-resonators do is mind boggling!

Now, the question: is any KOSHER ways to get somehow 15dB gain in an open baffle at 150-300Hz or I bound to use those open-box-resonators that Telefunkens used? I intend to use it only as the open baffle and the only chooses would be the original Telefunkens-box- open-baffle or my own flat-large panel. The second it much more desirable but what can I do with 15dB gain at upper bass?

Rgs,
The Cat
  Reply With Quote
Old 9th September 2003, 01:35 PM   #29
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by Romy
Now, the question: is any KOSHER ways to get somehow 15dB gain in an open baffle at 150-300Hz
Nothing I could possibly think of....

Sayonara
  Reply With Quote
Old 9th September 2003, 01:50 PM   #30
Romy is offline Romy  United States
Banned
 
Join Date: Sep 2003
Location: Boston, MA
Quote:
Originally posted by Kuei Yang Wang
Konnichiwa,
Nothing I could possibly think of....
Sayonara
OK, the harakiri is the only one my way out…. :-(

Rgs,
The Pussy
  Reply With Quote

Reply


Are you (open) baffled yet?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Baffled by a UPS analog_sa Parts 2 21st June 2008 06:34 PM
Open Baffled 3.5 TMMW or MTMW? Emiel Multi-Way 5 16th March 2006 05:09 AM
open baffled all over again then_dude Multi-Way 58 5th April 2005 10:42 PM
5" enclosed or 6.5" open-baffled coolkhoa Multi-Way 6 17th May 2004 03:18 AM
Passively baffled jmiyake Multi-Way 0 3rd February 2003 11:26 PM


New To Site? Need Help?

All times are GMT. The time now is 05:53 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki