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Old 21st January 2009, 08:40 AM   #1
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Default Back Loaded Horn with Passive Radiator?

I have just bought some Alpair 10s and while I already feel I have an application for them (BR for HT), I was wondering about whether there was a better way to use them to achieve the full dynamic range inherent with HT and of course music in general. Most of my searches came up with MTMLs (along with BR).

One post that interested me was by GM where he spoke about designing a BLH with PR. This came from the numerous FR drivers that are now also providing high Xmax. eg.
Item Qts Fs Vas Xmax Dimensions
Jordan JX92S 0.4 45 15.28 9mm 4"/92mm
Alpair 10 0.33 40 19.5 8.5mm 4"/100mm
CSS FR125SR 0.59 70 5.98 6mm 4.5"/125mm
Sonido SFR-144-8 0.228 55 14.8 6.8mm 4.5"/120mm

Has anyone actually put together a build or design like this? Interested to know folks thoughts on this.

NB: I am a newbie to speaker building so I don't mind if someone says I am completely off track
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Old 21st January 2009, 02:48 PM   #2
GM is offline GM  United States
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I don't remember what I wrote, but it's something I'd like to try one of these days with my early version FR125S drivers as it will probably only be viable with those that have a low mass corner. Anyway, with no way to sim it accurately it would be a trial n' error build/measure/tweak affair and probably have to do it again based if my prototyping history is an indicator.

WRT an MLTL for it, I recently tweaked an existing pair designed for the late RS 40-1354 to good effect IMO, so a viable option for modest average SPL down into the 30s, i.e. loud enough for small rooms and/or apartments and/or a near-field app.

GM
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Old 21st January 2009, 10:49 PM   #3
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Hi GM
thanks for your reply. If you do some work on a BLH with PR that would be great. I dont have the testing equipment so wouldnt be able to provide the necessary measurements if I did it myself. Sounds like a winter project

I saw your post on an MLTL for the Alpair 10 bass. What dimensions would be best for the MLTL with Alpair 10 Fullrange? Down to the 30s is mighty low I am currently planning to run them in pairs on each speaker.

thanks again
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Old 22nd January 2009, 02:36 AM   #4
GM is offline GM  United States
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Greets!

You're welcome!

I have many projects planned ahead of it and running out of time to do them, so if I do it at all it won't be anytime soon. Sorry.

The dims I posted for the Alpair 10 bass driver yields a near identical sim with the FR driver, though you may want to experiment with shorter vent lengths to flatten it in-room.

For dual drivers, double the CSA and number of vents: http://www.diyaudio.com/forums/showt...03#post1697803

GM
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Old 22nd January 2009, 03:53 AM   #5
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BLH with PR is something I've pondered for years.

What if you replaced the PR with a bass driver complete with magnet BUT not wired to anything?

The drivers magnet would actively try to return the bass drivers cone to its neutral position but would not have any electrical impact on the system because it would not be connected.

Would that work?



GM,

I have a pair of RS 40-1354A's - are you able to email me your MLTL plans?

Cheers,

Alex
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Old 22nd January 2009, 11:48 PM   #6
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Hi GM
Just double checking on some of the details ;-) The tuning down to the 30s is being acheived with the MLTL long only? The Z driver dimension with 2 drivers is for the centre of the top driver and the other driver sits in line underneath that? I am still learning
thanks again for your help
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Old 23rd January 2009, 12:19 AM   #7
CSS/XBL is offline CSS/XBL  Canada
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Hi,

I'm happy and willing to donate one of my new APR10s to the person who can convince me that they have the best solution for the Alpair 10 and the APR. Send me an email with you ideas.

Bob
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Old 23rd January 2009, 12:59 AM   #8
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Quote:
Originally posted by Antripodean
The Z driver dimension with 2 drivers is for the centre of the top driver and the other driver sits in line underneath that?
I interpreted GM's reference to 30's response to mean he put the CSS FR126S into the RS 40-1354. Let's see what the man himself says but I think Zdriver in a two-driver MLTL is usually the same for both drivers, i.e., the drivers are mounted on different panels at the same height, usually front and back, but I'm interested to hear whether there's a better position for the second driver.
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Old 23rd January 2009, 01:46 AM   #9
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Oops, I meant CSS FR125S.
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Old 23rd January 2009, 01:51 AM   #10
GM is offline GM  United States
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Quote:
Originally posted by Alex from Oz

What if you replaced the PR with a bass driver complete with magnet BUT not wired to anything?

The drivers magnet would actively try to return the bass drivers cone to its neutral position.......

I have a pair of RS 40-1354A's - are you able to email me your MLTL plans?
Greets!

Yes, you can do it, though its Vas, Xsus and Xmech specs come into play, so Caveat Emptor. The magnet has no discernible effect on the VC if there's no current flowing through it otherwise the high compliance prosound woofers I have laying around face down wouldn't be bottomed out against their suspensions.

Here's a write-up I did many moons ago. Pic is them during voicing, so unfinished. On a whim, I brought them to a DIY Meet and was pleasantly surprised that they measured within +/- 3 dB from 40-12.5 kHz tuned just by ear: http://myhifisite.50megs.com/gm/tower.html

With driver adapters and a longer vent, they play into the 30s loaded with early CSS FR125S now.

GM
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