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dmtp
07-11-2006, 07:38 PM
I'm looking for recomendations for a horn to mate with my LE85's. I have H91's at present, but take it from what I have read around here that CD or PT horns are preferred (FWIW, I do NOT have the 91 lens). I plan on mating them with LE-14A in a ~3 cf cab.

Zilch
07-11-2006, 08:20 PM
First choice: 2344(A) for an L200T3 clone two-way, as John W made:

http://audioheritage.org/vbulletin/showthread.php?t=9695

Use NL200T3-16 crossover for 16-ohm LE85s from over in Q&D:

http://audioheritage.org/vbulletin/showthread.php?p=71276&#post71276

What results to expect -- 2420 is JBL Pro version of LE85:

http://audioheritage.org/vbulletin/showthread.php?p=73059#post73059

For PT waveguides, which will require dual adapters, I'll have to do some testing to recommend a crossover.

You'll be very pleased with how sweetly original aluminum-diaphragm LE85s can play, if my experience with them is any indication.... :thmbsup:

Gotta test 'em tho; condition varies:

http://audioheritage.org/vbulletin/showthread.php?p=71329#post71329

dmtp
07-13-2006, 07:09 AM
I love the simple elegance of the HF section (I read the thread discribption of its funtion), but wht about the LF? No Zobel, no big resistor across the woofer like JBL usually does, Is this more 'magic'? or just not necessary?
TIA

Zilch
07-13-2006, 11:48 AM
I took a half-assed stab at figuring out the LF at one point there; fact is I still don't know enough to come up with anything definitive.

http://audioheritage.org/vbulletin/showthread.php?p=73676&postcount=192

See also post #195 by DavidF there.

What I DO know is that more sophisticated JBL networks are often tuned to specific systems for a particular voice - driver, box, baffle layout, damping, HF, etc. So I just strive to use what seems to work best, which means test, measure, and tweak when departing significantly from the original designs.

dmtp
07-13-2006, 12:50 PM
When I try to access site:
http://audioheritage.org/vbulletin/showthread.php?t=7551
I am told I don't have permission to view that page?????:(

Zilch
07-13-2006, 12:59 PM
It's the David Smith article, then a draft, subsequently relocated here:

http://www.audioheritage.org/html/profiles/jbl/4430-35.htm

dmtp
08-22-2006, 10:52 AM
I'm lookng at the original L200B XO and it says the XO in at 800.
The NL200t3 looks to me like it XO ~1000.
Question: At what freq should I XO the LE85 (bass will be LE14A)?
L220B vs. NL200t3 - pros and cons?
What freq (cut off) horn for the LE85? (I will be using a 'salad bowl' wooden Tractrix)

Mr. Widget
08-22-2006, 11:10 AM
Are you going to stay in the two-way realm, or will a tweeter be a possible part of the equation? I ask because as the tractrix horn gets larger to accommodate a lower crossover frequency, you will find greater high frequency roll off.

That said, as per our private conversation, I'd advocate going with a larger horn and lower crossover frequency point. The LE85 is rated to 500Hz at a reduced power level. I used them years ago in the S7 system... they will play to 500Hz quite well without damage, though they need a horn that can support a lower crossover. Realize that when I am talking about it's ability to run down to 500Hz, I am not suggesting a 500Hz crossover point... just that with a 700-800Hz crossover you will not be stressing the driver unduly at it's lower limit.

As for crossover, I'd be inclined to build a custom network.


Widget

Earl K
08-22-2006, 01:40 PM
I'm lookng at the original L200B XO and it says the XO in at 800. The NL200t3 looks to me like it XO ~1000.
-- Question: At what freq should I XO the LE85 (bass will be LE14A)?
L220B vs. NL200t3 - pros and cons?

- It's quite likely , neither network will give you optimal performance ( for the "salad bowl" in your project ) .

What freq (cut off) horn for the LE85? ( I will be using a 'salad bowl' wooden Tractrix)

- Build a custom/hybrid crossover that offers an effective 800 hz crossover point . Ron ( skrmn57 ) may have some suggestions , since he uses ( or has used ) salad bowls on 1" drivers .

- Read this Post ! (http://audioheritage.csdco.com/vbulletin/showpost.php?p=51748&postcount=13) to get an idea of what Dr. Bruce Edgar has to say on the subject ( Thanks to Ron ! ) . I'd be a bit more inclined to use a slightly larger Edgar Horn than the 650hz version ( the 8" mouth in front of a 1.75" diaphragm is fairly weenie, IMHO / though I'd like to see some "raw" FR measurements before forming a final opinion ).

- IMHO, aesthetically, a 10" to 11" circle ( outside dimension ), "looks" a bit more correct, when sitting above a 14" woofer .

:)

spkrman57
08-22-2006, 01:59 PM
My experience with Great Plains drivers 1" and 1.4"(basic Altec 902 and 288) has led me to use the 650hz round wooden tractix horns with 1" drivers crossed over at 1.6khz and the 1.4" drivers on 500hz round wooden horns crossed over at 800hz.

1" on 650hz salad bowl sounded bad at 800hz, usable but not desirable to me due to strain on lower frequenies and loss of upper HF response.

1.4" on 500hz salad bowl sounded good at 800hz and decent enough HF response(to approx rated 18khz top end) to allow me to not have to bother with tweeter.

1.4" on 500hz salad bowl crossed over at 1.6khz had much better voicing than the 1" driver on smaller horn, but I found too much zing on the top HF response.

After listening to both horns at their best crossover setting left me thinking the 1." driver sounded nice, but when using the 1.4" driver on the larger horn I left the 1" and 650hz horns sitting in the closet for now.

Bill H. at Great Plains sells the 902 and 399 drivers manufactured new for decent prices.

In comparison of the 1" drivers (Altec 902 and JBL 2426), I found the JBL better in the upper midrange but needing a tweeter for upper HF.

The Altec goes higher, but with less magical midrange of the JBL.

Many choices here, I prefer the Altecs due to availability and cost.

I run small SET triode amps most of the time.

Hope this helps some!

Regards, Ron

dmtp
08-22-2006, 02:08 PM
As I am sure you all know, The Circumference of The mouth needs to be equal to The wavelength of The lowest freq 600 Hz is about 7" Going lager will mean a lower "design" freq. and more loss on The topend..

Earl K
08-22-2006, 02:43 PM
As I am sure you all know, The Circumference of The mouth needs to be equal to The wavelength of The lowest freq 600 Hz is about 7" Going lager will mean a lower "design" freq. and more loss on The topend..

- Don't be so sure. ;)

- Depending on the speed of sound ( that you want to use today ), a 400 hz wavelength is @ 34" .
- 34" translates into (the circumferennce of ) a 10.8" diameter circle .
- Since I don't want to talk about horn design theory / I'll simply stand behind my earlier remarks ( - that a 10" to 11" wide horn "looks" about right ) .
- RTAs of any horns' repsonse will tell the FR story quite quickly .

- All horns appear to have HF loss / when the HF response is compared to the midrange performance. That disparity in level will grow as the horn size is increased. Get the lower limits of the horn loading correct first and then design a network that attenuates only the midrange by "x-dB" / while leaving in place the HF frequencies . In your case, you'll need to design a network that attenuates the midband frequencies ( in the neighbourhood of 12 db / give or take a couple of db ) .


:)

Mr. Widget
08-22-2006, 03:08 PM
It seems we are pretty much all saying the same thing... so it's a matter of which compromises you want to make.

I agree with Earl that you should consider a larger horn and custom network. I would use an additional tweeter.

I also agree with Ron that a larger driver will likely give you a better midrange sound, though you are obviously wanting to use the LE85s that you have along with your LE14As.


Widget

dmtp
08-23-2006, 01:23 PM
"Since I don't want to talk about horn design theory / I'll simply stand behind my earlier remarks ( - that a 10" to 11" wide horn "looks" about right )"

If you folks will indulge me, the theory is intriguing (and may even be useful if I finally get the time to work at the lathe and start making wood chips!). As I undertand it, an exponentional (or conical or hyperbolic) horn can extend indefinately - it just keeps getting larger. The merits of extending it beyond the point where the mouth = wavelength can be debated, but it is easy to do. A tractix horn, on the other hand, "ends" when the mouth = wavelength. The next step is infinity (the tangent to the curve is perpendicular to the axis of the horn at that point). The only way to make the mouth bigger is to design it for a lower freq. While a lower freq horn will certainly work when crossed over at some higher freq, why would you want to do that? It will also "peter out" and start exhibiting a high freq droop at a lower freq which would require more compensation. It would seem to me more ideal to choose your XO freq first and then design a horn about 25% below that - perhaps a bit more if you are using a low order XO (but that probably isn't advisable either).
I would love to hear alternative theory, or -even better- real live examples of this or divergent approaches. I have been a fan of horns for ages and read extensively, but I am very much still an amateur!

Mr. Widget
08-23-2006, 02:03 PM
While a lower freq horn will certainly work when crossed over at some higher freq, why would you want to do that?Because it sounds better. It's that simple.

Why does it sound better? I have no idea. I am sure many theories and analysis of this topic could be explored... but to what end. It sounds better.

Widget

spkrman57
08-23-2006, 02:18 PM
Tractix horns according to Dr Bruce Edgar(and others also) are shorter than other horn designs(hyperbolic/exponential/etc).


Tractix horns also are not designed to be used to their flare frequency since at the end of the flare(mouth) ends up being 90 degrees referenced to the throat.

Simple examples:

Edgar round tractix horns:

650hz flare - designed to be used no lower than 800hz minimum
500hz flare - designed to be used no lower than 800hz minimum
350hz flare - designed to be used no lower than 500hz minimum

While the 650hz flare works to 800hz(not well enough for my ears), I found a better overall sound performance when crossed over at 1khz or higher.

Not trying to confuse things here, just giving my points of view in the hope that it might help out.

Ron

Mr. Widget
08-23-2006, 02:30 PM
I wasn't going to bring up horn cut off frequency verses minimum usable frequency because it can get confusing. Since you have, my personal rule of thumb, which seems to roughly correspond with your findings is that you should use a horn no lower that 1 octave above it's cut off. Using that rule, the 650Hz horn should be crossed over no lower than 1300Hz.

Widget

Ian Mackenzie
08-23-2006, 05:56 PM
The LE14a might be interesting with a 2344 and perhaps Zilch has tried this already. Try making one out of wood like others have recently posted.

But it depends on your expecations and how hard you intend to run them and your level of skills with crossovers and system tuning etc.

If you are adventurous and intent on running horns down to 650hz, propably a good crossover point for a 1.4 inch driver; a 1.4 inch driver is a much better candidate or even a 2 inch driver like the 375. But the LE85 is still fun to play with and its a nice driver.

Some horn diy fans who love wood turning use mutiple horns over limited bandwidths ie 400- 1000hz using an LE5 , 1000 - 4000hz using a 375/2440. 4000-20K using a LE85 with some eq. These are not compact affairs nor are they Waf friendly but they can perform well with careful setting up...

dmtp
09-14-2006, 11:50 AM
No, I haven't heard it yet (still mocking up an XO - probably 1000Hz, maybe 800), but I had to post pics of my "salad bowl" horn. It is a 500 Hz Tractrix horn in solid cherry. In the first pic, you can see it mounted just above the LE14A in the beginnings of a cabinet. Walls of the cabinet are 1 3/8" thick (5/8 particle board & 3/4 MDF) and the speaker mounting board is at 30 degrees to the front wall. (It is lying on its back in the pic.) Cabinet was ~4 c.f. before bracing and the horn. I have yet to cut hoples for the tuning ports which will be two 3 1/2" (ID) mailing tube that just fit between the horn and woofer on either side.
The second pic shows the outside of the horn. The entire horn is 8 1/2" in diameter except for the ring 1 3/8" back which is 10" creating a nice mounting flange. The LE85 is mounted to a 1/2" piece of composit (bowling alley material that I got at the dump years ago!) which is then lag bolted to the cherry horn. (recessed hole in the horn for the three bolt heads). I intend to coat the horn with West Epoxy to create a nice smooth, shiny surface, but I'm waiting to finish the other horn before mixing epoxy.
Stay tuned!