Back Loaded Horn with Passive Radiator?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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 ;)
 

GM

Member
Joined 2003
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
 
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 :D I am currently planning to run them in pairs on each speaker.

thanks again :)
 

GM

Member
Joined 2003
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/showthread.php?s=&postid=1697803#post1697803

GM
 
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
 
Antripodean said:
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.
 
Alex from Oz said:

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
 
Antripodean said:

The tuning down to the 30s is being acheived with the MLTL long only?

The Z driver dimension with 2 drivers..........

Greets!

You're welcome!

Correct.

When drivers are vertically oriented on the baffle, 'zdriver' is the midpoint between the two so that the different loadings average out.

GM
 
rjbond3rd said:

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.

Correct, but I assumed he was referring to the Alpair MLTL in the referenced thread that sims into the 30s.

If a bipolar layout is used, then 'zdriver' is the center-line for both.

GM
 
Wound up doing more to get more detail out of them, though of course you can't make a 'silk purse out of a sow's ear', but they were very close to the 125 when it was BW limited to match, so if I'd bothered to add a decent super tweeter, who knows?

GM
 
fellow DIYers in Melbourne

Hi GM

Thanks for everything so far. I have drawn everything up and I am now having the boards cut for the cabinets.
I am making the MLTLs and also the BRs. As it is my first build, I am intrigued about the differences/similarities between the two configurations. I am going to do the listening test in situ in the home theater set up and also wanting to do some testing to actually know the frequency response.
So, this is also a shout out to fellow DIYers in Melbourne who have the gear and opportunity to do the testing. Please email, thanks :D
 
Example of BLH with Jordan

You can use the jordan very sucessfuly in a BLH, probably the same for the AN10. I've tried it with MLTL, but I like the BLH much better, much better base and dynamics. I used Martin king's spreadsheets to design these several years ago.

PJN
 

Attachments

  • jordan blh.jpg
    jordan blh.jpg
    32 KB · Views: 863
Hi PJN
They look great!! And I am sure they sound great too :)
I don't have access to MJK's Mathcad but I did read his back loaded horn articles and what really struck home was "If done correctly, a hybrid transmission line / back loaded horn enclosure will not require
any baffle step correction circuit which is the real big advantage. Imagine 94 to 98 dB SPL, at a 1 m distance for 1 watt of input, over the frequency range 50 Hz to 15-20 kHz produced by a single driver enclosure that is slightly bigger then a commercial tower speaker system."
Like many people I want to have a BLH but I dont have the space (height or size of room) to handle a massive cabinet. I am sure there is a BLH (TL hybrid) that I will be building soon :D Just need a design to make it happen ;)
 
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
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.