JBL 2123 in a Pi Mid Range Horn

[David Ketley]

I wonder if anyone had tried the JBL 2123 in one of the Pi mid range horns?

I'm looking to use it from 160hz to 750Hz and want to try and get a more linear response from the JBL 2123.

Dave

[more10]

Qes: 0.37
BI Factor: 13
Fs: 85 Hz

EBP = 85/0.37 = 230

You will have mass roll off at about 450 Hz (EBP * 2). A horn designed for this driver will be useful for about 2 octaves.

If you want to reach above 1 kHz you will have to use compression drivers.

I would not use it for horn loading.

[gibber]

Hi David,

didn't know you had this in mind when we were in contact a few months ago.
Try Beyma 102Nd or 102Nd/n if you'd like to climb higher up than 450Hz.
The former has 250mm, the latter a 260mm frame, so perhaps mechanically the smaller one is closer to your JBL. Quite an achievement to have efficiency at the same or higher level than 2123 (but these do the trick).

Both versions are the same with regard to the drive system (see attachment for TSP). Have 7 pcs, four of them in use, so if you'd like to try a pair, shoot me a PM.
67845
Mine have an fs of about 55Hz and Qes of 0.07 to 0.08 on average, so EBP ca 750Hz and mass rolloff at 1500Hz, but their rise in response will probably allow you 3 kHz on axis.
I softened two of my units to have fs@47Hz, Qts 0.06 and use them in my Phonogen folded bass horns to 400Hz. A K110 went to 250Hz in that cab...

br,
Ralph

[gibber]

Sorry, title should have read EBP ...

[David Ketley]

Taken from Wayne's web site

Horn Basics

The horn covers the 200Hz to 2kHz band and has 105dB/W/M sensitivity. Maximum power is 300 WRMS, so maximum SPL is over 125dB. Actual response depends on placement, but it is intended primarily as a midrange horn subsystem for three-way (and four-way)π cornerhorns, so corner placement is normal. In this application, the horn is smooth down to below 200Hz, almost to 150Hz.


http://www.pispeakers.com/seven_Pi_with_midhorn.jpg
Seven π cornerhorn with midrange horn and Martinelli tweeter horn


Response is good to 2kHz, and then drops about 5dB and remains at this reduced shelf for almost an octave, to 3.5kHz. This is due largely to breakup modes in the driver. Both the Eminence Delta 10 (http://www.pispeakers.com/Delta10.pdf) and the JBL 2012 (http://www.pispeakers.com/JBL_2012.pdf) have rising response that peaks in the region above 2kHz. What occurs here is that the cone begins to flex making ripples in the surface of the cone. These cone surface movements are decoupled from the heavier moving assemblies so it's like having another much lighter cone driving the horn. This makes a second area of response that increases output from the horn above 1kHz.

In some applications, this output can be used making the horn capable of output to 3500Hz. Other applications will want to rolloff the region above 2kHz, and I've found that this can be done with a simple 1mH series coil. This is the same "Pseudo Butterworth" arrangement I've used in the past, and the addition of a 1mH coil does very little to affect horn response below 2kHz. It just shaves the peak between 2kHz and 4kHz, attenuating that region and preventing it from increasing horn output in this range.

Seems OK?

David

[Hoerninger]

... so it's like having another much lighter cone driving the horn. This makes a second area of response that increases output from the horn above 1kHz.

This helps for a pleasing on axis frequency response. But for this the horn is needless.

It is not easy to find suitable drivers for a real horn support.
Gibber proposed an exceptional speaker for this task.
More10 is right with pointing out for usage of a compression driver for the higher frequencies.
A dividing frequency about 700 Hz (500 - 1000) is managable with some modern speakers.
___________
Peter

[more10]

Since the horn cannot be used below 200 Hz, the combination will be useful for only one octave.

Find a 200 Hz horn for compressor driver instead. The Auto-Tech 200T is an excellent choice, but you can go for tractrix horns as well.

Mårten

[David Ketley]

I think one of the greatest problems with 2" compression drivers is pushing them too low, I will be crossing my E-JMLC 2" horns at 700-800Hz


David

[more10]

You will need a phenoleum driver or a modified Radian diaphragm in a compression driver. Since you already have the ejmlc horn, go for the beyma drivers.

Mårten

[Hoerninger]

BMS 4592ND

2" Coaxial Neodymium Compression Driver



Features :




Extended Bandwidth (300 - 22000 Hz)
Neodymium Magnet Assembly
With two subsystems in one, each Driver covers a smaller Frequency Range for increased Power Handling, high Dynamic and extremely low Distortion
Excellent Phase Coherence
Perfect Time Alignment without Problems of Multi-Source Interference
Ultra light Weight
8 or 16 Ohm


http://www.bmsspeakers.com/index.php?id=bms_4592nd

http://www.adamhall.com/de/BMS_4592ND_-_2_Coaxial_Neodym_Treiber_150_W_und_80_W_8_Ohm.htm l
___________
Peter

[David Ketley]

The trouble with audio is that its all very much a compromise both in the transducers available and the time one spends on trying to actually listen to systems. Most of us particularly myself have a limited budget so that is my starting point. The reason I choose the system I've ended up with is that the units are available at a very reasonable cost. My latest purchase E-JLMC horns were funded by sales of HiFi on Ebay.

I have not considered the BMS 4592ND but always thought it was good practise to cross at 2 x the lowest given manufacturers frequency?

Thanks for the input.

David

[gibber]

I have not considered the BMS 4592ND but always thought it was good practise to cross at 2 x the lowest given manufacturers frequency?

Thanks for the input.

David


Hi David,

i have used both BMS 4590 and 4592 on JBL 2360 horns the six years i was based in China. But i suspect that one reason why that worked is that these horns are quite long. 68411

In China that length's no prob. Nobody cares if you hire one of those aircon installer guys and have holes cut through the concrete and have them BMS suspended 50cm from your outer 10th floor wall :p The tiny balconies on those appartment buidings for the aircon outdoor unit come in handy, too -- you can stand on them when swapping drivers.

X/o 300 Hz electrically, ca 350 Hz acoustically. Bass units are TL-1601B's (first series). Great setup !

Ralph