Fostex FF85K as tweeter with JBL LE111A woofer?

[Norris Wilson]

Hi everyone,

I found a pair of JBL LE111A woofers that need to be put back into service. But, I am not quite sure what design to use.
I considered replicating the original JBL L110's, but decided against it due to the cost of drivers and obscurity of the 033 tweeter.

I was thinking of using the Fostex FF85K as a tweeter from 1kHz and up with the JBL LE111A.
My thought is to possibly load the LE111A in an MLTL or BIB cabinet. And mount the FF85k in an OB arrangement.

Has anyone used the FF85k specifically as a tweeter?

Also, any ideas of how to pair these two drivers together, or other suggestions would be appreciated.

Scroll down for LE111A specs: http://www.drewdaniels.com/JBL_PARM.XLS

FF85k: http://www.madisound.com/catalog/PDF...vers/FF85K.pdf

Thanks

Norris Wilson

[badman]

The LE111 is very low Qts, due to a very strong motor, it would seem. A box alignment may be tough to decide upon, as it's not really inherently suitable for anything but horn-loading, though it MIGHT be able to work with a relatively high tuned reflex alignment.

I use the 123A as a midwoof with the FF85k, first order series at 500Hz, works a charm. There's never going to be good top-octave power response with the ff85k, so you do have to take some care positioning so that you get all that tweetery goodness.

[Norris Wilson]

Thanks badman,

Horn loading the LE111A is out, unless it would be down firing at the floor. I have never warmed up to the sound of a rear firing horn. And a LE111A front firing horn would be huge and unrealistic mated to the FF85k. Unless, I could firgure out a proper waveguide for the FF85k.

After looking further at the box options with a BIB, MLTL, or RFH.
I may just go with the original L110 reflex box for the JBL 10" to keep the box size down. I figure I could get away with using the LE111A as a midbass from 75Hz up to around 800Hz to 1kHz, where the FF85k will take over.
So, a subwoofer would be required to fill in the bottom octave.

I will play around with the crossover point to see what yields the best results for the highest output and uniform response of the FF85k.

Thanks again for your input.

Norris Wilson

[planet10]

I'd encourage the use of the FF85k as a midtweeter... this is a very nice driver (blew up my 1st one today -- DC from an amp).

I'd recommend an XO somewhere around the bafflestep frequency. The JBL specs sufficiently higher SPL to make this work a treat.

dave

[Norris Wilson]

Ouch!!!!!!

"(blew up my 1st one today -- DC from an amp)."

I plan on bi-amping these drivers with no more than 6 watts on the FF85k.

Dave, could you tell me what the step frequency would be for the FF85k?

Also, looking at a picture of your modifications to the FF85k. I see that you have modified the aluminum dust cap some how. It looks as if you crimped it into more of a phase plug shape than a dome.
Could you tell me what the results are from doing this reshaping?

Thanks

Norris Wilson

[chrisb]

Originally posted by Norris Wilson
Ouch!!!!!!

"(blew up my 1st one today -- DC from an amp)."

I plan on bi-amping these drivers with no more than 6 watts on the FF85k.

Dave, could you tell me what the step frequency would be for the FF85k?

Also, looking at a picture of your modifications to the FF85k. I see that you have modified the aluminum dust cap some how. It looks as if you crimped it into more of a phase plug shape than a dome.
Could you tell me what the results are from doing this reshaping?

Thanks

Norris Wilson

The only mods are EnABL polka dots to the cone and metal dust cap. The latter is small enough on this driver that photos can be a bit misleading.


Dave will pipe in later on the subject, but my first guess on XO step frequency would be anywhere from 250-300Hz on up

[planet10]

Originally posted by Norris Wilson
Ouch!!!!!!

I have to look at is an opportunity to dissassemble one, check the voice coil size and verify that there is a copper cap... then the frame goes into Chris' template kit for fitting boxes around the drivers....

boy do they stink...

Dave, could you tell me what the step frequency would be for the FF85k?

That is dependent (mostly) on the width of your box.

dave

[Norris Wilson]

Thanks Guys for your input.

chrisb, I should have specified the dimensions of the L110 box before asking for the step frequency.

Dims: 23.5" H x 14.25" W x 11.25" D

About the way I thought the dust cap on the modified FF85k looked, I just have to go back and look again. This time I will clean my glasses first.

Dave, I like your optimism in turning your damaged FF85k into an opportunity to look inside. I hope it will help you in your future upgrades of this driver.

Norris Wilson

[planet10]

Originally posted by Norris Wilson
14.25" W

4560/14.25 gives a 1st irder approximation of the bafflestep -3dB of 320 Hz.

dave