Need Advice - Big Motor 15" Coaxial

[Magnetar]

What cabinet design would you recommend for the PAS CXL-2580C - It's a beast of a driver. The biggest motor single driver I have ever seen.

[IMGDEAD]http://www.pas-toc.com/images/products/components/cxl2580c.jpg[/IMGDEAD]

Surely I could put it in a bass reflex, but I'm looking for a design that will take better care of the back wave to reinforce the bass. Size is an issue, I really don't want to go over 24" wide but it can be tall and deep. I don't want to use baffle step correction, I'd rather build the right cabinet to use the back wave energy. I have had BIG back loaded horns and find the delay off the back side mating with the radiation off the front presents problems mucking up the upper bass. This is unacceptable to me. I want the bass to be tight, strong and linear.

What do you think about a tuned quarter wave pipe for a driver like this? Compared to a back horn? What is the least compromise? Why? What other cabinet will be the best compromise?

The cabinet will be 6' from the front wall so it will be pretty much on it's own. What do you do about floor bounce reflections with single drivers? Don't you get a horrific dip?

They only need to go down to 50 cycles strong, I have an appropriate sub. If the bottom end gets too strong, I have a front horn for the 15 to even it out.

It seems you guys are good at getting the best ot of the little 8" 'full range' drivers, so please advise what you'd do with this.

Thanks

 

[flshzug]

0this is the 2" HF driver version of the coaxial used in UREI 811B - 813B -815B. I did simulations on their low end response , and guess what bought some JBL 15 inchers since.

 

[Magnetar]

0this is the 2" HF driver version of the coaxial used in UREI 811B - 813B -815B.

Yes, I don't want to add 15's like UREI - this also has a bigger, stronger magnet and 4" voice coil

 

[flshzug]

these cxl-s were sold on ebay some time ago and i gave it a tought , but even If I skip JBL's for the coaxials, they most likely would be the neodymium Beyma 15" or 12"s . I bought the JBL's 'cause I can forget about seperate subwoofers ( think of 4435 hehe ) now.

 

[Magnetar]

these cxl-s were sold on ebay some time ago and i gave it a tought , but even If I skip JBL's for the coaxials, they most likely would be the neodymium Beyma 15" or 12"s . I bought the JBL's 'cause I can forget about seperate subwoofers ( think of 4435 hehe ) now.

I have the top of the line Beyma DX15 - with 4.5" coil and large format compression driver. They are very good, these seem to be better in the midbass and mid in my test box though. Also like the bigger horn and choice of compression driver.

I got these off ebay for 129 a pair! LOL - they are MINTY

 

[CLS]

I notice it has a relatively small Vas for such a big driver, so BIB comes to mind

(Or I should say, BBBIB ? )

Just plug the numbers in, I got:

Vb = 460.3 L
H = 207.3 cm
W = 39.6 cm
D = 56.0 cm
Height of Driver = 114.4 cm


Looking good

 

[Magnetar]

I notice it has a relatively small Vas for such a big driver, so BIB comes to mind

(Or I should say, BBBIB ? )

Just plug the numbers in, I got:

Vb = 460.3 L
H = 207.3 cm
W = 39.6 cm
D = 56.0 cm
Height of Driver = 114.4 cm


Looking good

Sorry - I'm not up on that lingo yet! What is this BIB and how did you already derive the numbers?!?

the size seems fine but why the high driver ???

 

[CLS]

BIB is a long story.

To make it short, here is the basic configuration:
http://www.zillaspeak.com/bib-howtobuild.asp


And here is all the calculations come from:
http://www.diyaudio.com/forums/showthread.php?postid=1190733#post1190733


And here is the built BBBIB:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=106083


That is 12incher version, now you can make a 15incher one

Almost all BIB related thread are very long. It's hard to keep following.

Actually I never build any of them, just keep planning. Too many projects, too little time ....

 

[Saturnus]

By height of driver, he means center of driver above floor level.

 

[Magnetar]

I see, still too tall, three feet would be ideal for me at center. - I found the BIB website from Godzilla - These look like they may have some bass ripple? I'm reading about this...... hmmm - it's almost a horn - why not add a back chamber?

[IMGDEAD]http://www.zillaspeak.com/lovechild-bib7om.jpg[/IMGDEAD]

 

[GM]

It can be scaled to 3 ft.

BIB are just simple pipe horns with the emphasis on 'simple'.

Considering your audio systems history though, I doubt you'll be satisfied with a BIB even if corner loaded as they're meant to be to reduce the ripple somewhat.

Anyway here's the ~36" driver height version:

L = 124"
W x D = 17.75" x 25.125"
zdriver = 26.875"
a-b-c = 12.5625"

GM

 

[Magnetar]

It can be scaled to 3 ft.

BIB are just simple pipe horns with the emphasis on 'simple'.

Considering your audio systems history though, I doubt you'll be satisfied with a BIB even if corner loaded as they're meant to be to reduce the ripple somewhat.

Anyway here's the ~36" driver height version:

L = 124"
W x D = 17.75" x 25.125"
zdriver = 26.875"
a-b-c = 12.5625"

GM

Thanks!

Well i kinda like the tall profile and narrow front baffle- What type of loading would you propose then? Is it possible to get great bass without resorting to adding bass drivers in a system out in the room like this? I never thought so but single driver folks obviously are getting great satisfaction from single eights!!!

I was hoping to find a low comprise design I could upscale to a 15 - I have some 32" diameter spheres here I could load these into and add some woofers below the sphere but just using the coax without helpers intrigues me.

 

[GM]

Yes, they are, but they accept the limited dynamics and higher distortion such systems impose, things you historically have strived to increase the former while decreasing the latter.

Anyway, probably the lowest compromise design without resorting to a helper woofer is a ML-horn driven with a high output impedance amp to EQ it ~flat. Otherwise a ML-TQWT with a big SS amp and BSC ckt. to flatten it at the expense of 3-6 dB eff. loss depending on your room gain.

GM

 

[Magnetar]

Yes, they are, but they accept the limited dynamics and higher distortion such systems impose, things you historically have strived to increase the former while decreasing the latter.

Anyway, probably the lowest compromise design without resorting to a helper woofer is a ML-horn driven with a high output impedance amp to EQ it ~flat. Otherwise a ML-TQWT with a big SS amp and BSC ckt. to flatten it at the expense of 3-6 dB eff. loss depending on your room gain.

GM

- you just saved me lot's off time.. Thank you

 

[pdan]

You might enjoy these TL's, designed by Jack Bouska, using Altec 18" drivers :www.audioheritage.org/vbulletin/showthread.php?t=12126

Cilla