Bruce Edgar Midrange Horn for 2445

[Dr.db]

Hi,


I´d like to build some wooden midrange horns for my 2445 2"-drivers.
I love the look of the Bruce Edgar horns, but I can`t find exact plans to rebuild some of them. Can anyone help me out ?

Besides that, I have a generell question on horns:

If the physical cutoff-frequency of a horn is 500hz, I would have to cross it over at 1000hz, right!?
For example this horn;
http://www.soniphase.com/speakersc.html
It has a 400hz cutoff, so crossover should be around 800hz.....!?

Another example, the JBL 2380;
http://www.jblpro.com/pages/pub/components/2380a.pdf
It claims to be useable from 500hz.... But the frequency-drawing shows, its very weak between 600-1000hz and actually starts rising efficiency sufficient at about 1100hz and up.
So without eq-compensation, even this horn shouldn`t be used below 1000hz!?


Thanks a lot and have a great week,
Olaf

[more10]

The reason you want to cut a horn one octave above cutoff is group delay and driver loading. This is a simulation of a 1100 Hz le Cleac'h horn:


Black is resistive load, red is reactive. The reactive load causes phase shift. You want to cut at the first notch on the resistive curve. From this curve I would say 2,5 kHz.

This is group delay:


Group delay is a measure on how much phase shift you have. 2,5 kHz looks ok here too.

With a real horn and driver, you can measure the impedance curve or use our ears.

Horn shapes have influence on the sound. Any angles in the horn causes reflections. Le Cleac'h horns don't have reflections. Tractrix horns on a baffle don't reflect either. On traditional horns you get less reflection problems the higher you cut.

[ivica]

Hi,


I´d like to build some wooden midrange horns for my 2445 2"-drivers.
I love the look of the Bruce Edgar horns, but I can`t find exact plans to rebuild some of them. Can anyone help me out ?

Besides that, I have a generell question on horns:

If the physical cutoff-frequency of a horn is 500hz, I would have to cross it over at 1000hz, right!?
For example this horn;
http://www.soniphase.com/speakersc.html
It has a 400hz cutoff, so crossover should be around 800hz.....!?

Another example, the JBL 2380;
http://www.jblpro.com/pages/pub/components/2380a.pdf
It claims to be useable from 500hz.... But the frequency-drawing shows, its very weak between 600-1000hz and actually starts rising efficiency sufficient at about 1100hz and up.
So without eq-compensation, even this horn shouldn`t be used below 1000hz!?


Thanks a lot and have a great week,
Olaf

Hi Dr.db,

I have understood that You want to make "tractrix" horn, so IF you have decide to use it from 500Hz, Rm-horn mouth radius has to be about 25cm, and the length would be about 50cm, ( fc=220Hz) but the "problem" of such horn type would be very narrow at higher frequency, so here about 23 deg (-6dB) on 10kHz. from my point of view, this too 'beamy' result for home-listening purpose. Almost the same results (but shorter horn) can be get from the JMLC horn type.

About the 'construction'

"......
HornCalc is based on this formula:

x = a * ln((a + sqrt(a^2 - r^2)) / r) - sqrt(a^2 - r^2)
where;
x is the distance from the mouth of the horn,
a is the radius at the mouth, and
r is the radius at distance x from the mouth.
....
Thus, P.G.A. Voight can be claimed to calculate: Fc=c/(4*r)...
c is the speed of sound, 340m/s, and "r" is the radius of the horn mouth for the fully expanded tractrix"

http://stereo-lab.de/Information-Sph...-Tractrix-Horn
http://www.sonicdesign.se/horncalc.html

http://darklanternforowen.wordpress....midrange-horn/
http://www.positive-feedback.com/Iss...rinterview.htm

regards
ivica

[more10]

Aha, Bruce Edgar midrange horn is Tractrix! Then you can use Hornresp to simulate it and also generate horn profiles. You can quite easily make a petal Tractrix horn.

With a Radian diaphragm you can make the driver go lower. Just decide on how low you want cutoff, 200 Hz is reasonable if you can house such a big horn.

[Dr.db]

@ Mårten:

Thanks for the graphs, I think I got it
Phase-shift seems to be the biggest issue when crossing over to low...
A round tractrix horn like this below should have no reflections, but I think it is much more beamy than a bruce edgar tractrix-horn!? What do you think ?
http://gpoint-audio.com/wp-content/u.../03/T400-2.jpg


@ ivica: Thans for your calculations and links!
I don`t need to crossover as low as 500hz, I´m actually aiming 800-900hz as a crossover-point
I need a horn with flat-front and I´ve heard the JBL 2380 or 2370 are not very suitable for hifi-use, because they do not sound very musical
So I thought a tractrix-horn like the bruce edgar would be better sounding.
I have a 2405 to cope with the highs, so the midrange horn should behave gently to about 8khz. Is it allready too beamy at these frequencies ??

http://www.soniphase.com/speakersc.html
Any ideas, how such a horn would sound...!?
Any better than the JBL 2380 ?

I would try to decrease the measurements a little, to fit it into my enclosures.... My maximum width would be about 16". So cutoff should be little higher than 400hz, maybe 450hz I guess...

[ivica]

@ Mårten:

Thanks for the graphs, I think I got it
Phase-shift seems to be the biggest issue when crossing over to low...
A round tractrix horn like this below should have no reflections, but I think it is much more beamy than a bruce edgar tractrix-horn!? What do you think ?
http://gpoint-audio.com/wp-content/u.../03/T400-2.jpg


@ ivica: Thans for your calculations and links!
I don`t need to crossover as low as 500hz, I´m actually aiming 800-900hz as a crossover-point
I need a horn with flat-front and I´ve heard the JBL 2380 or 2370 are not very suitable for hifi-use, because they do not sound very musical
So I thought a tractrix-horn like the bruce edgar would be better sounding.
I have a 2405 to cope with the highs, so the midrange horn should behave gently to about 8khz. Is it allready too beamy at these frequencies ??

http://www.soniphase.com/speakersc.html
Any ideas, how such a horn would sound...!?
Any better than the JBL 2380 ?

I would try to decrease the measurements a little, to fit it into my enclosures.... My maximum width would be about 16". So cutoff should be little higher than 400hz, maybe 450hz I guess...

Hi,

If You decide to use 2-inc throat tractrix type horn over 500Hz you have to deal with the beaming problem

regards
ivica

[more10]

The Edgar midrange horn is a biradial horn with conical vertical expansion and tractrix horizontal expansion. It cannot be simulated in Hornresp, this doesn't mean it is bad only it cannot be calculated.

The whole point of the tractrix expansion is to avoid sharp edges on the horn in order to avoid reflections. The conical upper and lower parts of the Edgar horn will cause reflections.

Any cylindrical horn will be beamy. This means that you will have a small sweetspot and a rising response directly in front of the horn. In practice you will have to EQ the horn or point the horns away.

[ivica]

The Edgar midrange horn is a biradial horn with conical vertical expansion and tractrix horizontal expansion. It cannot be simulated in Hornresp, this doesn't mean it is bad only it cannot be calculated.

The whole point of the tractrix expansion is to avoid sharp edges on the horn in order to avoid reflections. The conical upper and lower parts of the Edgar horn will cause reflections.

Any cylindrical horn will be beamy. This means that you will have a small sweetspot and a rising response directly in front of the horn. In practice you will have to EQ the horn or point the horns away.

Hi more10,

You are right that Edgar horn has different flares: in vertical plane as conical horn, and in horizontal plane as tractrix. In the mentioned horn , as seems to me, either plane horn mouth would produce a kind of reflections in the lower frequency range ( say under 2kHz), but I would expect that the horizontal dispersion of the frequency over (say ) 4kHz would mainly affected by the horizontal plane horn flare, so the beaming would be present. I have such experience with such type of the horn with the Dynaudio D54 mid-range driver applied -look at the attached figure.
http://www.forker.de/downloads/300hz_d54_horn.pdf

Such driver is fare from being the same as JBL 2445 driver, but the beaming has been evident without the need for any kind of measurements, so from such experience I would expect that using 2445 driver with such as Edgar Tractrix (horizontal) horn would be beaming horn too.
May be looking at the JBL solution such as 2380, or PT-H95HF, or 18-sound XR2064 where a kind of narrowing sound passage in the horn throat would produce a kind of expanding dispersion , here , in the horizontal plane.

Regards
Ivica

[more10]

May be looking at the JBL solution such as 2380, or PT-H95HF, or 18-sound XR2064 where a kind of narrowing sound passage in the horn throat would produce a kind of expanding dispersion

These horns have diffraction slot for better horizontal dispersion. I believe the diffraction slot is bad for the sound.

I like the biradial horns like the Yuichi, they don't beam much.

[more10]

You can find a lot of interesting horns at Auto-tech. They can be bought in USA from DIY Sound Group. They have a few Bi-radial horns, but no flat-front.

[Dr.db]

Thanks a lot four your help!!


Bruce Edgar horn will be beamy, because it is still tractrix....

JBL 2380 won´t be beamy, but will have even more reflections caused by the diffraction-slot


Yuichi-horns won´t be that beamy, but they´re not flat front



Are there any flat-front horns which are sweet sounding ?

[more10]

Olaf

Since you are building the horns yourself, I suggest that you build exponential or hypex horns from a hornresp simulation. Hornresp will help a lot generating the cut profiles. You can tell Hornresp to use conical vertical expansion.

The A 200Hz Exponential Midrange Horn for Altec 288B has pictures of a larger horn. Interesting project.

If the horn beams you can eq it. If it sounds bad you have learnt something :-)

Mårten

[ivica]

Thanks a lot four your help!!


Bruce Edgar horn will be beamy, because it is still tractrix....

JBL 2380 won´t be beamy, but will have even more reflections caused by the diffraction-slot


Yuichi-horns won´t be that beamy, but they´re not flat front



Are there any flat-front horns which are sweet sounding ?

HI Dr.db,

That is why I would suggest You to pay your attention to: JBL PT-H95HF, or 18-sound XR2064 horns, as both are "flat" mouth, an either have a kind of "soft diffraction throat", and as seen from their horizontal plane dispersion I believe that they would be 'sonically' acceptable up to about 10kHz.
but not lower then 800Hz (I think).

http://www.jblpro.com/ProductAttachments/tn_v1n31.pdf

http://www.eighteensound.com/Portals/0/PDFs/XR2064.PDF


Regards
Ivica

[Dr.db]

@more10: Thanks for the idea But I wanna stuck to a completed design which is allready well tested.


@ivica: Thanks, those are some nice looking alternative flat-front-horns! But I am afraid, that a JBL 2397 or Yuichi Horn will still sound a lot better, right

I have the feeling that all these flat-front horns are just some kind of compromise. They might sound allright, but they´re never really good sounding!?
So perhaps I have to rethink my design to be able to integrate a 2397 or Yuichi...

[Hoerninger]

You should remember the KLANGFILM Kugelwellenhorn, which is well documented in this forum.
Avantgarde Acoustics uses this type of horn:
http://www.avantgarde-acoustic.de/de...orntechnik.pdf

A Kugelwellenhorn integrates well with the baffle as a tractrix does.
But it is shorter, so the dispersion is wider.
____________
Peter (HH)