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pangea
03-26-2004, 08:45 AM
Hi everyone!

Does anyone have any Tractrix/exponential/hyperbolic plans for the 2105?
I could use a bit of help there.

I would like to use them as mid-bass drivers, because I like the clean and crisp sound they produce and also because I already have them on the shelf.

However the sensitivity is much to low for my purpose, (2105/2445J/075) so I went looking for some formula to calculate some horns and to see if they were suited for horn loading, which I found them to be by a wide margin, but then I got stuck on the calculations because the formula didn't say if the parameters were in feet, inches or in the metric system.

So I wonder if anyone could help me with the measurements preferably on a frontloaded horn. But if it's considered that a rear-loaded horn would be better, then of course I would choose just that.
I also think I wan't the horn to work between 290 Hz to 1000 Hz if possible. I also think a square horn would look better and also be a bit more practical as well as easier to build.

Also what kind of sensitivity could I expect from the horn-loaded 2105H?

Grateful as always for any help I can get.

BR
Roland

DavidF
03-26-2004, 12:23 PM
Dr. Bruce Edgar wrote an article for US publication Speaker Builder circa early 1980’s following his efforts to match off-the-shelf mid range drivers to tractrix horns. With his interest in horns progressing, Dr. Edgar moved on to bass horns and full-range systems. You will see references to him or to “Edgarhorns” at many sites and forums on the net.

Back to the midrange, one of the better drivers he found to mate to the horn was the LE5-2, and later the 2105. The horn had a square throat of about 10 cm a side, with a rectangular mouth of about 36 by 51. The upper and lower trace of the horn was flat, the sides were shaped on a tractrix curve.

You may be interested to know before exploring this design that the lower-end cutoff was 400Hz, or higher if you need to roll-on under more gradual slopes. The rising response of the LE5 allowed for a fairly flat response out to about 4000Hz but this driver is not suitable for good response much below 500Hz, horn-loaded or not.

DavidF

pangea
03-26-2004, 01:43 PM
Hi DavidF!

Thanks for your input!!!
It seems I have to find me another driver. :(

I was thinking I could use the 2105 above my bi-amped 2231H's in vented boxes, under 100 Hz and my equally bi-amped 2220A's in 4530's, crossed over between 200 - 300 Hz with a 18 - 24 dB/oct. slope. I was thinking I could play with the butt-kicking bass levels, without affecting the mids too much, but if I have to take the 2220's up to 500 Hz it will affect the mid section too much, don't you think?
Above the 2105, the 2445J would have taken over from around 800 - 1000 Hz, or so I thought.

But it seems I was a bit too optimistic there.

Is there another not too expensive, but still good sounding mid-bass driver, that you or anyone else could recommend, producing a sensitivity at about 105 dB/W/m, i.e. leveling with the 2445J, without too much attenuation on the HF/UHF?

Perhaps a 8" or 10" driver.

BR
Roland

DavidF
03-26-2004, 02:28 PM
I am not one who can give you direction with the use of the JBL heavy artillery. It is true though that you have to have a larger voice coil and drive assembly in the power range if you want high dB response with low distortion. When you mix horns with cone drivers you will always have the further complications of blending the power response of the two drivers. Taking a 15” driver up to around 1000Hz may not make the best sense in terms of micro detail in the upper mid-range, but this is often the best frequency range to match it to a horn in terms of consistent power response (dispersion narrows as the frequency is increased, matching with the horns narrower dispersion at the crossover).

DavidF

Mike Bates
03-27-2004, 06:53 AM
I use the 2123 from 180 to 1K in a large round tractrix horn with the 2440 crossed in at 1K loaded in smaller round tractrix horns and then 2405 at 10k -- with this all passive first order networks. Below that 2220A 50 -180 in front laoded expo horns with 2nd order passive line level biamped - and below 50 another amp with a 3rd order active network driving three 18's in sub horns.

The 2123 is VERY good in these horns but the back chamber is tricky to build at one liter volume.

I have the little 2105 and they sound like toys compared to the 2123 even when horn loaded.

What I'd like to try is the new 10" 2012 driver in place of the 2123 -- with it's rising response and bigger motor it may actually better the 2123..




Originally posted by pangea
Hi DavidF!

Thanks for your input!!!
It seems I have to find me another driver. :(

I was thinking I could use the 2105 above my bi-amped 2231H's in vented boxes, under 100 Hz and my equally bi-amped 2220A's in 4530's, crossed over between 200 - 300 Hz with a 18 - 24 dB/oct. slope. I was thinking I could play with the butt-kicking bass levels, without affecting the mids too much, but if I have to take the 2220's up to 500 Hz it will affect the mid section too much, don't you think?
Above the 2105, the 2445J would have taken over from around 800 - 1000 Hz, or so I thought.

But it seems I was a bit too optimistic there.

Is there another not too expensive, but still good sounding mid-bass driver, that you or anyone else could recommend, producing a sensitivity at about 105 dB/W/m, i.e. leveling with the 2445J, without too much attenuation on the HF/UHF?

Perhaps a 8" or 10" driver.

BR
Roland :)

pangea
03-27-2004, 08:39 AM
Hi Mike!

It seems we're going down roughly the same path, except for me using the 2231H instead.

You're mixing Tractrix with expo's, is that OK? I read somewhere that one shouldn't mix different kinds of horns, because it was said to create differences in the imaging, i.e. it wouldn't be possible for the speakers, to sort of disappear.

I have no idea if that's the case, but perhaps you or any one else here knows anything about this.

BR
Roland

Mike Bates
03-27-2004, 09:56 AM
The expo horns are used below150-180 cycles, I know of NO (zero) full range tractrix horns. IOW one that is fully horn loaded from the deep bass through the treble. The 2405 is around 40 by 90 where I crossover at 10K - I can't imagine finding a tractix super tweeter let alone one that will blend better than these old alnico slots. They allow for a little larger listening window where the tractrix begins to beam (25 times the flare rate, in this case the 2440 horns flares are 360 cycle) they open up and give nice detail and presence to the very top end. Bass horns generally will perform better with an expo flair, and will go lower with more slam and authority than a tractrix.

Imaging is as good as I have heard from any system with this current rig.. no complaints. One of the goals of building this beast was to recreate a realistic soundstage.

pangea
03-27-2004, 10:45 AM
So, if I take my 075 as is (only a 1,2 uF Cap), my 2445J (1,6 kHz - 10 kHz 6dB/oct., -3dB Att.) mounted on a Selenium horn, a 2123H mounted on a Tractrix horn (180 Hz - 1 kHz 6dB/oct.), my Bi-Amped 2220A in the 4530 horn (50 - 180 Hz 12dB/oct.) and my Bi-Amped 2231H vented box (Electronic 24dB/oct. x-over between 20 - 50 Hz), then I would only run into trouble between the 2123/Tractrix and the 2445/Selenium/expo?

Is that a correct assumption, or are there more problems hidden there?

BR
Roland

Mike Bates
03-27-2004, 11:18 AM
I doubt there would be much as far as trouble. The problem I personally have is listening to large format compression drivers and direct radiators below them. IMO that's where the trouble is. There is a huge difference in realism between the horn loaded 2123 and using one or two of them as direct radiators. When placed in a horn they go from excellent (direct radiated) to a whole nother level. The radiation pattern ideally should be the same between the low mid and mid horn but I really can't say for sure how much of a problem it is since my horns are identical and I haven't expiremented much otherwise. At the 1k crossover point it makes sense to use the same general radiation -- My guess is the lower the crossover the less of a problem. For example a 500 cycle crossover point should be less sensitive to the 'trouble.'

pangea
03-27-2004, 11:44 AM
Perhaps an exponential horn on the 2123, would be a better match with the 2445/Selenium horn, though I can't go as low as 500 Hz, because I'm using first order crossover and secondly because the Selenium horn doesn't work well below 800Hz.

By the way, do you or anyone else, by any chance know anything about P.audio? Someone told me recently that the JBL 2123H and the P.audio P10/100MB are made in the same factory. They also look very similar and seem to have almost the same specs. What's going on there? Is it true that P.audio makes drivers for JBL?

BR
Roland

GordonW
03-28-2004, 07:09 AM
AFAIK, many PAudio driers are an eastern-asian (HK, I think?) "knock-off" of JBL drivers. Yes, they're VERY similar. I just saw a pair of the PAudio 2225 clones yesterday; it took me more than a minute to realize they weren't 2225s. If it wasn't for the different size of the pole vent screen and the shape of the back plate, it'd be very hard to tell the difference.

As for the 2123- having looked at the response curve of that driver, I've consistently thought that would make one of the best candidates for a tractix or exponential horn midbass, that exists. Naturally rising driver response is EXACTLY what the doctor ordered for a horn... a typical horn has the exact OPPOSITE response shape. Makes for very little response shaping or compensation necessary in the crossover...

Regards,
Gordon.

JoshK
07-28-2008, 12:40 PM
Sorry for drudging up a thread from the black hole, but this is precisely what I was looking to do. Mike or anyone else, can you provide some more details on the tractrix/horn loaded 2123H? I have a pair of 2123H's and am thinking of doing this very same thing.

Cheers,
Josh