LE15A/375/075 Box Design

[Val]

I've re-surrounded the LE15A's, read the books, wasted WAY too much time browsing this site and have knocked out a box design for my beloved drivers. I've decided to post the design in hopes that smarter people will point out dumb things before I start cutting wood and wasting even more time!

My design factors are this: Make them small so my lovely wife will let me put them in the living room (they will be stereo speakers). Make them simple to build (no time for fancy joinery). Don't spend too much money. Vertically align the 075 and 375 for better imaging. I'll be using 1" MDF. I've used WinISD for the math.

Comments welcome! Thanks.

[Zilch]

BaseBox 6 Pro says you want your box tuned to 32 Hz, with 4" duct length 4.25".

Do you have enough room for the dispersion lens there? It's not shown....

[Val]

Yes, I think I have enough room. I believe the footprint of the acoustic lens is about 4" x 10". I've been looking for a pair but haven't found any (I probably couldn't afford them anyway

Thanks for running the BB math. It's probably better than WinISD.

[Mr. Widget]

You may want to try a 5.75" length duct as well and subjectively compare them. It will give you a slightly lower tuning ~30Hz... depending on your room and your own listening tatses, you may prefer the slightly lower tuning. You gain a tiny bit of deeper bass with the lower tuning.


Widget

[toddalin]

I would mount the drivers in a verticle array rather than off-set.

[GordonW]

I would mount the drivers in a verticle array rather than off-set.

I agree with this sentiment; though, I could see mounting the midrange and treble drivers say, one inch off center, to break up diffraction modes just a bit. You don't want the acoustic centers that far off of the vertical line through the center of the woofer, since it does go up to around 1KHz...

If you were to move your port upward, to where it was next to the 075, you should be able to accomodate this driver arrangement. Personally, that's what I'd do.

Also, if you offset the drivers, naturally be sure to "mirror image" the cabinets. This will definitely help imaging/soundstaging perception.

My only other suggestion would be to use the 077 or 2405 slot tweeter, rather than the 075... but with the drivers you've chosen, this is probably about the ideal arrangement.

Oh, one other thing comes to mind- you may want to use a "u-bolt" large enough, to clamp the 375 to the brace. Something like a very large muffler clamp U-bolt (probably available from anywhere that does truck or high-performance automotive exhaust systems) or the U-bolts made for large wiring or plumbing conduits should work. Just attach a couple of L-bracket to one side of the brace, and feed the U-bolts through the holes in the L-brackets, to clamp the unit down. This will prevent any side-stress whatsover, in ANY direction, on the front of the horn...

Regards,
Gordon.

[Zilch]

If you move the mid and high drivers in line, use dual, smaller ports either side of and belowish of the 375.

That'd be two 3" ducts 5.75" long (best choice), or two 2.5" ducts at 3.5" long for the 32 Hz tuning (Orchid).

For Widget's 30 Hz tuning, it's two 3" ducts at 7.0" (Blue).

Your original tuning (~36 Hz, actually,) in Black.

All of the proposed tunings are the same at 40 Hz. Me and Widget are gettin' you a leetle more bass extension, is what....

[rloggie]

Hi,
I believe the lens you would want are L91. You may want to check out this Ebay auction.

http://cgi.ebay.com/JBL-L91-HORN-SPE...QQcmdZViewItem

Good luck.

[Zilch]

Jeez, $144. Time to clean some up around here.

Why'm I sittin' here lookin' at these dusty things...?

[toddalin]

Yes, I think I have enough room. I believe the footprint of the acoustic lens is about 4" x 10". I've been looking for a pair but haven't found any (I probably couldn't afford them anyway

Thanks for running the BB math. It's probably better than WinISD.

I have a couple of the HL89 horns with the folded chamgagne-colored lenses (Hartsfield horns) I would part with. The lenses are normally 19.75" wide, but one was cut down to 15.825" and other has a cut on one of the plates at this same 15.825" width. (These were cut to fit the former owners cabinet but I guess he had second thoughts on the second.) This is still several inches wider than the horn opening of 9" with a 10.5" mounting flange. The horns are in fine shape except that the prior owner filled in a couple of the mouning holes with putty (easily removed). They have a depth of 12" if you rear mount them and about 11.75" if you surface mount them. The driver has a depth of 5.25" so they should just fit your listed cabinet depth.

If you cut the both to 15.825" you would have no problem fitting them on your baffle and would have something unique and different than anyone else.

[rloggie]

These may work better.

http://cgi.ebay.com/JBL-L91-Acoustic...QQcmdZViewItem

Jeez, $144. Time to clean some up around here.

Why'm I sittin' here lookin' at these dusty things...?

[Val]

Thanks for all the suggestions. I've updated the drawings to move the 075 and 375 1" off center, put in two 3" x 7" long ports and anchor the 375 with a gianormous u-bolt. I've also penciled in where an H91 might one day go (one can hope). I will mirror image them.

Thanks for the ebay links on the L91's. I'll keep an eye on the cheaper ones but they will probably go out of my pathetic range in a few days. I did ponder the H89 solution. Mounting those monsters would be pretty cool but would not pass the "In my living room?!?!" test.

I'll be using 1"MDF. Do you think the baffle will be too weak around the ports? The inner circle on the LE15A indicates the cut-out.

Thanks again for all the input.

[Zilch]

L200's are laid out like what you have. See my Avatar. They're made out of 3/4" MDF.

I believe that the woofer and horn frames strengthen the baffle once mounted.

It's difficult to brace between the ports; the concern is legitimate.

How do we feel about moving the ports into the upper corners?

[Robh3606]

Why are you keeping the ports on the baffle?? Unless they are going to be shoved up against the wall you could always drop them on the back panel.

Rob

[Val]

I've thought about putting the ports up top on the front. I'd like to avoid that if I can as I'm thinking I will only cover the LE15A with a grill. I like looking at the 075 and 375/L91 and will leave them exposed.

I like the idea of back mounting the ports. If I do so, how far should the cab be kept from the wall? Now that space is not an issue is it better to go with one 4" port rather than two 3"?

Hmmm. 3/4" mdf is easier to get and work with. Is it overkill to go w/1"?