Cabinet volume = 2.4 cu.ft. = which JBL driver?

[Wornears]

Hello all:

About a year ago I bought a pair of incredible condition home-made speaker cabinets from a thrift -- the cabs immediately grabbed me. Whoever built them really had wood skills. They are out of 1/2--3/4-inch cherry (I think), have cane grills and a great '60s, box on four (stout) legs look.

They have a single 12-inch driver hole and a 3-inch diameter port tube that is 10-inch long/deep, and directly aligned below the 12-inch driver. No tweeter provision. The inside dimensions are 22H x 12W x 16D, which is 2.4 cu.ft. if I haven't jacked the math. I think the builder must have been reading audio mags of the time too.

Amazingly, they were loaded with full range LE-8T/16-ohm drivers (that needed then and still require re-edging -- I've been busy <G>) mounted on an external board screwed to the main driver baffle. The board downsized the 12-inch mounting hole to accept the smaller LE-8T. I pulled the LE-8Ts and boards and installed some Utah 12-inch coaxial full range drivers I had laying around, and have been playing them. OK sound, with decent bass, but I wasn't going to risk hurting the LE-8Ts.

I've since acquired a pair of LE-10A drivers ready to run, and a decent pair of L-88 Novas. The drivers and crossover are bone stock and work great. They are early L-88 with black/dark woofer and LE-20 tweeter and no way to install the mid-range kit without major surgery.

I drive them with a tube receiver (15--20 wpc), and really like their sound. I have plenty of SS amps to drive them with, too, if needed. I eventually need to refinish/re-veneer the L-88 cabs, and was thinking I'd pull the complete drivers/crossover of the L-88 and transplant them to these home-made cabs while I do the L-88 work. I can do wood work, but would rather work on cars when I have a chance, so would probably be better off sending them to a real woodworker to get them done right.

Putting the L-88 driver combo in the home-brew cabs would mean cutting a place for the LE-20 and crossover. I'd put the drivers back in the L-88 when done and then have to re-load the home-made cabs.

So, a few questions for the speaker-building gurus here. Given all the (long-winded) background above, which driver combo would be appropriate/best for these home-made cabs with port?

1) Get the full-range LE-8Ts professionally refoamed (they have hard and cracked Lansalloy surrounds -- but I tested them at low volume--once-- and they work fine) and reinstall them? No tweeter, no crossover, no fuss. Is the cab too big a box with its port for this driver?

2) Make a downsizing board for the working LE-10As and use them? No tweeter, not crossover, no fuss.

3) Transplant the L-88 drivers and leave them there. Cut holes for LE-20 and crossover. Sell the 5/10 L-88 cabs for someone else to load. (I really do like the L-88 cab look though!)

4) Your suggestions, please.

Pics of the cab later. Thanks for all your help!

Wornears

[Zilch]

#3, closed port, but I wouldn't bother with the LE20s. They hardly even qualify as tweeters by today's standards:

http://audioheritage.org/vbulletin/showthread.php?p=123070#post123070

Read on in that thread:

http://audioheritage.org/vbulletin/showthread.php?p=132587#post132587

LE10A will work as woofers in your box, too, ported, once you get good HF in them. Then, I'd put the same HF in L88s and move the 123As back into them, closed box, heavily damped per my study there:

http://audioheritage.org/vbulletin/showthread.php?p=124348#post124348

[Wornears]

Thanks Zilch, I have more reading to do. What is a good downloadable approximation program to plug all the parameters into (speaker and cab) and get an idea of their compatibility? Free would be good.

I had seen in one of your other posts about damping/closing the port of the L-88, so have put some loosely rolled socks in them and noticed the bass boom was muted to a more pleasing level (for me). I was familiar with this low-buck "tuning" tool having had a friend with some Marantz's with the optional foam plugs in the ports. We used loosely rolled up socks when the foam eventually went to dust and the cloth worked fine. That was in the '80s.

Should have patented the idea: Acoustic Fiber Tuners!

[Zilch]

Download free WinISD to play with box designs. Google will find it for you.

Socks won't get it. You need to close the box tightly as described there.

Your biggest problem is the HF, and that $10 JBL waveguide horn is a surprisingly well-performing approach.

Post a pic of your custom cabinet front baffle layout.

Here's LE10A. You're excursion limited to ~50 watts at 50 Hz. Port is 3" dia. x 5.5" long for BB6P suggested 31.11 Hz. This may not be the optimum tuning; I just click buttons here: :p

[Wornears]

Roger Zilch on the socks! Off to the hardware store for the Zilch Sound Damper.

Appreciate the refer to WinISD -- will get it and start the numbers -- and the LE10A curve.

Pic later this evening. Have to quit coming here during work!

[spkrman57]

I went to Lowe's to get some and they looked at me like I was wacked!

I went to Home Depot and they looked confused until one of the staff said "all we have are these test-plugs", at which point I said: That's what I need!

I bought 6 of them (4") for approx $26.00 for the group.

They are tough to get started, once they can grip the port they work just fine!

Be prepared to torque them down a bit!

Ron

[Zilch]

I went to Lowe's to get some and they looked at me like I was wacked!

I went to Home Depot and they looked confused until one of the staff said "all we have are these test-plugs", at which point I said: That's what I need!Yeah, well, until they get up to LHF speed, home improvement centers aren't gonna know what Zilch's Bass Dampers are.

[Maybe I'll schedule some training seminars.... :p ]


They are tough to get started, once they can grip the port they work just fine!I put silicone oil O-ring lube on the tapered ID of the rubber part. They operate smooth as snot, now.

[Teflon spray'd probably work, too... :thmbsup: ]

[spkrman57]

Quoted from Zilch:

[Maybe I'll schedule some training seminars.... :p ]

You get'em Zilch!

Ron

[Thom]

No advice on the cabinets but whatever you do, if you have never heard an LE8t don't discard them. It's not the ultimate speaker or anything but for an 8 in full range it is amazing.

[Wornears]

Thom: Thanks for the advice on the LE-8T. I had gathered from researching here that they were one of the better JBL vintage drivers and will not part with them. I want to find a use for them in another project. Have to solve this one first.

[Wornears]

Per requests, pics attached. The Utah driver is a 12-inch.

Thanks for any help with my project.

[Zilch]

Your cabinet is quite beautiful.

It appears the front baffle is removeable, is that correct?

If so, that opens up the prospect of inverting it to put the woofer at the bottom, and using the area where the port is for HF options.

And also the possibility of making new baffles for other driver/port combinations....

[Wornears]

Zilch: Thanks for the complement on the cab -- the other is in just as good a condition. They were $15/each -- with the cracked and hardened Lansalloy edged LE-8Ts (16ohm) loaded in each. As is sometimes the case, the local thrift didn't know what they had, and I got lucky.

Full disclosure: I was originally attracted by the looks and build of the cabs, and didn't recognize the LE-8T from its woofer face -- strange surround material and white cloth cone. So, I used a pocket tool I always carry to unscrew one and found out how heavy it was and read the label on back. I had to mightily restrain myself from letting out a loud Yippie! and prancing around the thrift like a lunatic. I casually replaced the driver, put on my best Oscar-winning-minimal-interest-manner and talked them down from $20/cab.

I'll try to see if I can extract the baffle tonight. The way these are put together they may be glued in. I was going to try this anyway to get the port up off the floor.

IF I can extract the baffle, then I could make one with a provision for a tweeter or other drivers. Otherwise, I'd rather not take a saw to these, and would prefer an external tweeter if possible and if that yields improved sonics. I am not aware of modern tweeters sound that much, but know that titanium ones I've heard are too bright and brittle for my ears. Guess that is what L-pads are for though.

[I have seen from your posts you do not have such quivering about taking a power saw to enclosures<G>.]

[Wornears]

Zilch asked: "It appears the front baffle is removable, is that correct?"

I followed up on that thought.

The guy who built these cabs found some clever plans, or was creative -- the 3/4-inch thick front baffle lifts out for replacement/changing drivers. You have to unscrew the cabinet top and lift it off, undo the front screws that hold the baffle to its two rear support rails along its long sides, and just lift it out from between the front of the cab and the support rails.

So, for now I just flipped it over to put the 3x10-inch (long!) tube port on top with the 12-inch Utah full-range drivers on bottom. Nice of the original builder to put the baffle securing screws on each side in symmetrically -- lift out, rotate, insert, screw down. The original port tube is glued in very stoutly, so only tuning on it will be a permanent cut.

Now I can cut out replacement baffles (sealed or ported) to fit any of the JBL driver combos I have.

Note the original 1-inch thick fiberglass internal batting; top piece removed for photos. The top and front baffle had never been extracted since original assembly AFAIK. All those wood screws were tight!

[Zilch]

Very clever. It's not apparent how the top screws on. Where is that?

I'm not understanding why you want the port on top. That coaxial driver wants to be up where the axis is closer to ear height for the high frequencies.

Having the port at the bottom will produce more low bass due to the floor boundary, I think.... :dont-know

I'd make baffles for the LE10As first, I think. Let me run that again to get dimensions for dual ports:

Two 2.5" diameter at 8.75" long.

Dual 3" looks best, at 13.35" long. I think I'd do that using elbows on the inside ends.

LE10A is not an extended range driver. You're gonna need tweeters with them; your #2 isn't gonna sound very good up top.

Cut another set for your L88 woofers, no ports. See which bass you like best.... :thmbsup:

[Wornears]

Zilch: It wasn't obvious at first to take the top off. I first tried to extract the baffle from the front and unscrewed all the visible screws. The bottom of the baffle would move, but the top was still held in place. So I started looking at the top.

Underneath I found about 8 countersunk screws pointing up -- undid all them and the top lifted off.

I put the woofer on the bottom just because I could do it <G>. Looks a bit more conventional for a speaker if I did have a tweeter in it.

From your previous suggestions -- the LE-8T has no place in this cabinet? Looks like I'll have to find another homemade set of cabs at a thrift of smaller dimensions <G>? Any pre-built cabs you'd recommend?

What would you suggest as a decent tweeter to use with the LE-10A, and with the L-88 woofer (to replace its LE-20) -- given that modern ones with titanium are very brittle sounding to me? I'm going to build a specific unported baffle (per your comments above) for the L-88 woofer and a tweeter TBD.

Man, I'm asking a bunch of questions! Did I comment anywhere that I deeply appreciate your individual guidance and sharing your hard-earned expertise and time with someone who has spent most of their life evaluating store-bought audio gear, and not building/modding extensively on his own? Well, I do. Thanks!

[Guy in WNY]

Wornears, those are really cool. Great for switching up drivers and trying other components. Nice thread you got started here.
Please keep us all posted - looks like you are going to have a lot of fun.
:applaud:

[Zilch]

From your previous suggestions -- the LE-8T has no place in this cabinet? Looks like I'll have to find another homemade set of cabs at a thrift of smaller dimensions <G>? Any pre-built cabs you'd recommend?http://audioheritage.org/vbulletin/showthread.php?t=6153

[Wornears]

Zilch: I read the post you referenced directly above about the LE8T enclosures and you found:

"Older alnico LE8T's like a smaller 2.5 cuft., apparently."

Was that ported or sealed?

Guess the original resizing board to mount the early alnico LE8Ts I have wasn't just a WAG install. I shouldn't have expected such from the person who built these cabs. (Can you imagine how much they would cost to do in a production line? That switchable baffle would break you.) See attached plans by JBL. -- hope they are readable.


Yet, I'll still need a JBL (prefer that if possible, but open to others) HF driver for use with the LE8T it seems. You were more keen on the LE-20 in those earlier posts. What changed your mind?

[clmrt]

You could always add hunks of wood to the cabinet (think scrap 2x4's stacked and taped). This would reduce the volume if you needed to tune it under 2.4 cf.

Seal the port, add 0.5 cf of solid fill to get Q = .707.

Nice cab for tweaking - I see a veritable library of loaded baffles in your future. Maybe even L77's if you can make them fit.

You might need a crossover solution, though.

[Zilch]

You were more keen on the LE-20 in those earlier posts. What changed your mind?At that time, I was looking for a vintage tweeter that would play low on the AR4x crossover, being lazy, basically, and wanting to make them 100% JBL.

Since then, I've measured LE20-1s in L88, and LE25s in L100, and neither hardly even qualifies as a tweeter by contemporary standards.

I'd encourage you to find a nice pair of 035tiA (on eBay, perhaps,) and try those with the LE8Ts, despite their being titanium. The filter can be rudimentary, just a cap and L-Pad, at a fairly high frequency, for starters. You just want to sweeten the VHF with those.

I have some L44s I may mock up with 035tiAs in place of the passive radiators. I certainly considered the AR4x experiment successful, though, as you know, I went on to do something more radical with them. :p

I'll post a pic of the tweeters that were in the AR4xs, which have better VHF extention than the LE20/25 for sure; maybe somebody will recognize them. Upon removal, it was apparent they were replacements, and perhaps not AR.

If you find you don't like the 035tiAs, Audax might be an alternate choice. They're also an industry "standard," apparently....

*****

I'll check whether the 2.5 cuft was ported or closed. I've got it in a file here somewhere....

[Wornears]

Thanks to all for their comments and knowledge on this project -- I have a friend who publishes an on-line woodworking mag (www.newwoodworker.com (http://www.newwoodworker.com) -- shameless plug, but good Joe Average skill material). He has every wood shaping/cutting tool known to man, so I have to get some MDF to buy for baffles...

I was thinking of a very simple crossover -- maybe even a single cap, no L-pad, like in the old days.

I'll likely try the L-88 drivers in a sealed baffle version of this cab first because the parts are all on hand. I probably don't hear over 12K anyway...being 50-plus can do that to you. <G>

[Zilch]

Zilch: I read the post you referenced directly above about the LE8T enclosures and you found:

"Older alnico LE8T's like a smaller 2.5 cuft., apparently."

Was that ported or sealed?
Ported.

For "extended bass" alignment in your 2.4 cuft box, tune to 33 Hz with a single 3" port 4.5" long:

[Wornears]

Thanks Zilch! Great data to have when I get the LE8Ts installed. Wow. The more I look at this site, I see you have done a LOT of driver/combo measurements . Thanks for sharing all that effort.