Polars Plots for Altec Multicells? - 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 14th February 2013, 07:20 PM   #1
steve71 is offline steve71  Australia
diyAudio Member
 
Join Date: Nov 2007
Default Polars Plots for Altec Multicells?

I'm using hornsrep to model a front loaded bass horn to cover 60-300/500hz.

I want the horizontal dispersion pattern to match the 1003 multi-cell at the crossover at around 400hz.

The 1003 is a 90x40 horn, but at what point does the horn loose pattern control?

There are three options.

(1) Find some published measurements - I'm sure I've seen them somewhere, but can't locate them now...
(2) Built some sort of turntable and do my own off axis measurements out doors
(3) Model the 1003 in hornsrep. Not sure if this is possible and I can't find thiele and small data on the 288 compression driver. Is there a speaker testing tool that I can buy that will measure the t/s parameters of a compression driver?

I've noticed, playing around with hornsrep, that it is mouth size that determines the point at which the horn looses pattern control. So can I just measure the size of the 1003 horn mouth and model a single exponential horn of that size to determine the horizontal beam width at the crossover point.

I know that the 1003 is billed as a 90 deg dispersion horn and a conical bass horn around 150cm length with a mouth area ~ 4,000cm^2 will give me a 90 deg horizontal beam at around 400hz and play down to 60hz.

Help!
  Reply With Quote
Old 14th February 2013, 08:24 PM   #2
diyAudio Member
 
Join Date: Jan 2008
I have seen polars of the 1003 before, and also could not find them.
As I recall, they are diffracting outward more than 90 degrees at 400 Hz.
Your own off axis measurements out doors would be best.
Your bass horn will likely be quite a bit deeper than the 1003, if you built 90 degree waveguides for the sides of the 1003 matching the LF horn you could control the dispersion and reduce diffraction.
  Reply With Quote
Old 14th February 2013, 08:39 PM   #3
diyAudio Member
 
Join Date: May 2010
Location: MN
What's wrong with #2? You don't need a turntable, just a dot, a protractor, and some string. You can probably get workable measurements indoors too, if you've got a room with a high ceiling.
  Reply With Quote
Old 14th February 2013, 09:02 PM   #4
steve71 is offline steve71  Australia
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by weltersys View Post
I have seen polars of the 1003 before, and also could not find them.
As I recall, they are diffracting outward more than 90 degrees at 400 Hz.
Your own off axis measurements out doors would be best.
Your bass horn will likely be quite a bit deeper than the 1003, if you built 90 degree waveguides for the sides of the 1003 matching the LF horn you could control the dispersion and reduce diffraction.
From playing around with hornsrep the bass horn needs to be about 150cm long, not including the driver chamber. I like the idea of extending the 1003 - I just need some way to make it look acceptable. On axis it sound good playing down to 300hz so it would be nice to cross that low. That would also mean I could make the bass horn mouth a little larger, smoothing out the response a bit.


Quote:
Originally Posted by dumptruck View Post
What's wrong with #2? You don't need a turntable, just a dot, a protractor, and some string. You can probably get workable measurements indoors too, if you've got a room with a high ceiling.
I've never taken these type's of measurements before, so it will be a good learning process, since I need to do measurement of the final speaker anyway.

The biggest problem I have is that the 1003's that I have are tar filled 150lb monsters. They're in the house at the moment and I need to relocate all my gear to the outbuilding (I'm turning it into a home theater) which is separated from the house by about 150 yards. And that 150 yards is buried in snow right now.

It would save me a ton of trouble if I could just model it in hornsrep or go off Altec's measurements. Beats waiting for the snow to melt.
  Reply With Quote
Old 14th February 2013, 11:01 PM   #5
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by steve71 View Post
From playing around with hornsrep the bass horn needs to be about 150cm long, not including the driver chamber. I like the idea of extending the 1003 - I just need some way to make it look acceptable. On axis it sound good playing down to 300hz so it would be nice to cross that low. That would also mean I could make the bass horn mouth a little larger, smoothing out the response a bit.
I envision something like the sketch below, whether it looks acceptable would be a subjective opinion. The wings would definitely be a big help if you want to cross as low as 300 Hz.
Personally, I find looking at horns and raw speakers makes me constantly think of what could have been done better, so I have always have covered them with speaker cloth since 1981 .

Art
Attached Images
File Type: png Horny.png (138.5 KB, 257 views)
  Reply With Quote
Old 14th February 2013, 11:27 PM   #6
steve71 is offline steve71  Australia
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by weltersys View Post
I envision something like the sketch below, whether it looks acceptable would be a subjective opinion. The wings would definitely be a big help if you want to cross as low as 300 Hz.
Personally, I find looking at horns and raw speakers makes me constantly think of what could have been done better, so I have always have covered them with speaker cloth since 1981 .

Art
That looks good, I like that concept. But if I were to make the mouth of the bass horn that large, the beam width would be less than 90 deg at 300hz - or am I missing something?
  Reply With Quote
Old 14th February 2013, 11:34 PM   #7
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
steve71,
I think that Cal Weldon has the information that you are looking for. I see him on many of the multicell threads and I think he is a real Altec lover. Personally I can't handle the 1.4" drivers at that low a cutoff frequency but everyone has their own preferences. Talk to Cal and see what he says. Search for his name, he is on all the time.
  Reply With Quote
Old 15th February 2013, 12:04 AM   #8
steve71 is offline steve71  Australia
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by Kindhornman View Post
steve71,
I think that Cal Weldon has the information that you are looking for. I see him on many of the multicell threads and I think he is a real Altec lover. Personally I can't handle the 1.4" drivers at that low a cutoff frequency but everyone has their own preferences. Talk to Cal and see what he says. Search for his name, he is on all the time.
Thanks, I will send Cal a PM if he doesn't chime in here. What horn were you using down to 300hz and what didn't you like about it? What crossover slope were you using? I'm using an active crossover with 24db/octave roll off, that might be the difference?
  Reply With Quote
Old 15th February 2013, 03:32 AM   #9
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
I haven't seen polar plots, but Altec did publish directivity plots for all the multis. I swear I had a copy but can't find it now. Should be online somewhere.

I could do it, but it would be a week or two before I'd get a chance.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 15th February 2013, 06:32 AM   #10
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
Originally Posted by steve71 View Post
The 1003 is a 90x40 horn, but at what point does the horn loose pattern control?
Around 180 Hz.

GM
Attached Images
File Type: gif 1003 polar response.gif (86.3 KB, 246 views)
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  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
waterfall plots bonsai171 Multi-Way 28 8th January 2014 05:24 PM
HOLMImpulse measurements into polars? boris81 Multi-Way 3 26th July 2011 09:27 PM
Multicells horn with BMS hugobors Multi-Way 10 18th September 2010 08:05 AM
Altec 811B horns and Altec 414z 12" Speakers xecluded Swap Meet 0 21st September 2008 05:21 AM
Boutique Bi-polars? setmenu Parts 2 26th December 2005 04:19 AM


New To Site? Need Help?

All times are GMT. The time now is 03:24 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