2 Way using AMT Heil.

[speakerdave]

Ok, i`ve picked up a pair of D123s and am thinking a ported box about 4.0cu ft tuned to 38-40hz? I know that these don`t have the bass of the 123a-1s, but are more efficient. Anybody got any experience working with these drivers?

I'd like to be a little more encouraging about the D123. It is a more linear driver than the other D's (D131, D130 and D208), and less efficient, which will make it a better match for the Heil tweeter, which is not as efficient as one might think.

I have put the D123 in a box about the size of the one you suggest, and I think it will work. Mine was crossed over to a tweeter at about 1500, if I recall correctly. You could even use a somewhat higher crossover point than your original idea of 800, which would be better for the Heil and I'm guessing the dispersion patterns would be more in line. I've never finished a system using the Heil, but I've experimented with it.

You will get bass with the D123 in that box, do not fear. What will not be there will be VLF. I doubt that you are shooting for that right now. The D123 has a free air resonance of 35 Hz. I would experiment with different degrees of damping in the box, starting with fairly light (one layer on one of each set of opposing surfaces).

The 6BQ5 makes a very nice little amp, and those fifteen watters have more guts than many people would think. You already know that you are not looking for gut thumping volume.

You have to understand, most JBL people slowly become bass freaks once we discover what true VLF is like. As Widget said, that may be in your future. But for now, I think the project you are contemplating will be quite satisfying.

David

[speakerdave]

I've done comparisons of the efficiency ratings of some drivers that appear in charts with both old and new methods. It appears that adding 49 dB to the old rating will give the number arrived at by the new method with closer miking. The LE14 is listed at 44 dB in the old charts, so by the new method I would expect 93 dB. It is more efficient than one might think.

David

[Mr. Widget]

I've seen JBL rate the LE14A/H at 91db and at 93dB... like so many of their specifications, I have no idea why their numbers would vary.


Widget

[speakerdave]

I doubt the specs vary as much as the accuracy of the copywriting and proofreading. The online information about the LSR32, for example, stated that the midrange was 2" when in fact it was a 5" midrange with a 2" voice coil. As happens on the internet, this bad information was copied everywhere and probably hurt the sales of the speaker. After all the effort that goes into engineering speaker systems, to have this kind of thing happen is really ridiculous.

David

[Robh3606]

I've seen JBL rate the LE14A/H at 91db and at 93dB

Take a look in the T/S tables

http://www.lansingheritage.org/html/...s/tech1-3a.htm

Then use this with the %

http://www.trueaudio.com/downloads/spl_eff.xls

Looks like rounding???? Not sure on the 93

Rob

[castlesteve 1]

Thanks for the encouraging replies. I was beginning to think i had made a mistake in buying these woofers. I will experiment with raising the crossover but i have read that the aluminium dustcap on these has a breakup node around 6-7khz which i would like to avoid. I am also looking to pickup apair of Altec 414s which i will A/B with the 123s.
All i have to do now is build the boxes. These will be the biggest yet! I am going to use plywood and laminate the baffle with 1/2" mdf.
Thanks again, Steve.

http://img.villagephotos.com/p/2006-...-system005.jpg

[speakerdave]

. . . . I will experiment with raising the crossover but i have read that the aluminium dustcap on these has a breakup node around 6-7khz which i would like to avoid. . . .

I don't think it's a breakup node, but rather a bump in response based on the dimension of the aluminum dome. I wouldn't use a twelve-inch much over 1000 Hz, anyway, so the 7k mode should not be a problem. The Altec 414 is a very good idea, but I'm a little concerned about efficiency matching. You want your woofer to be the least efficient element you will be linking with a passive crossover. You don't want to be in the situation of having to pad down your woofer to match the tweeter. See if you can find an efficiency rating of the Heil before you buy any more woofers. Have fun.

David

[moldyoldy]

(snip) See if you can find an efficiency rating of the Heil before you buy any more woofers. Have fun.

David

I've had a pair of AMT-1s in their boxes in the closet for.....awhile......and gathered what info I could when I got them. Can't find the file, but 97dB 1W/1M is what I recall, down to around 700Hz, with a fairly quick rolloff. The power rating surprised me, IIRC, around 125W. Someday, I'll find out for myself.

[moldyoldy]

Here's a (semi-useful?) response plot;

http://www.audioasylum.com/forums/MU...ges/78320.html

And for the dedicated patent-reader;

http://patft1.uspto.gov/netacgi/nph-...&RS=PN/4160883

[kartsmart]

Here is a link for the ess http://www.lautsprechershop.de/hifi/...endchen_en.htm

[arawak1969]

I just got a pair of the AMT1's from Gordon W and here's my idea.
AMT1 HF 7500+
511 802-8b Mid <500-7500>
jbl 2225 woofer 500hz and below

I would build a 9846 box and run it sealed.

Now I think that would rock.

I could run a pair of Crown VFX-2A's with Altec 9441 HF, Hafler DH-200 on the Mid and 9442 LF.
That would give killer mids and HF with TIGHT LF

[yggdrasil]

I'm not trying to be a party killer, but you should do a frequency response check on your Ess tweeters.

This winter I was visiting a friend with some test equipment in the trunk, and both tweeters was stone dead above 10KHz. Both checked with and without the Ess crossover in the loop.

Attached is the left speaker without the crossover connected.

[speakerdave]

I'm not trying to be a party killer, but you should do a frequency response check on your Ess tweeters.

This winter I was visiting a friend with some test equipment in the trunk, and both tweeters was stone dead above 10KHz. Both checked with and without the Ess crossover in the loop.

You mean the curve was the same? Can you post the two curves, with and without the crossover?

David

[yggdrasil]

I'm sorry. Looked around on the computer, but it seems only one set of curves have been saved.

I can remember though, that the only reason for measuring without the crossovers was that I could not believe the curves with crossovers in the loop.

[Zilch]

How big is 9846?

Seems inappropriate to run 2225H sealed.

Have we been through this already in another thread?