"Coloration" of horns

[pangea]

Hi!

This is my first post here and I'm hoping to find some help regarding a suitable X-over for my JBL 2445J mounted on a short (13 cm) exponential horn.

Right now I'm experiencing some "coloration" from the horns as my x-over is 551 Hz. I have tried another x-over at 7000 Hz without any coloration what so ever. But I would like to be able to go as low as possible, but without the coloration of course.

I have noticed that the x-over on some large JBL monitors is set at 1.1 KHz, so I wonder if that x-over frequency is high enough to avoid coloration, or do I have to go even higher?

Otherwise my filter is a 12 dB/oct L/R, HP: 10uF (polypropylene) and 8 mH, L-Pad (-10 dB attenuation) 7,5 Ohm/11 Ohm with a 4,7 uF parallell over the 11 Ohm.

BR
Roland

[boputnam]

Hey, "pangea"

Great moniker, by the way (said the geologist... )

Widget knows best on the 2445's, but note that the 4355 using the 2441 x's at 1,200 Hz, and the 4345 with the 2421B (smaller diaphragm...) x's at 1,300 Hz. Me thinks if you're able to do something in that range, you'd be best to do so.

What MF are you using, and is this a three- or four-way assemblage?

[pangea]

Hi!

Thanks for your advise!!!

I would say my set-up is a total hybrid, but I'm quite happy with it. I have a pair of speakers made by the former Swedish representative Tommy Jenving called "JBL KIT 65 BIG" they are somewhat upgraded with new 2402H, new 2105 although with Alnico magnets, but never the less brand new and at the bottom end a pair of brand new 2231H. On top of all that I have next to them a pair of newly re-coned 2220A in a 127 L custom build and extremely rigid enclosure made out of 25 mm MDF board with an extra panel on the baffle, with heavy bracings and all kinds of special damping materials inside!!! Rediciously well built, when come to think of it!
The MF sub chamber is still empty, but I hope to find a pair of reasonably priced 2123H to fill that void, in the near future!

On top of this speaker I have a custom build adjustable "top" for the 2445J with a pair of, dare I say this here, Selenium exponential horns from Brasil (HL 14-50). I bought them because I had the opportunity to listen to them some time ago and they sounded completly neutral then, so I thought they would be ideal for my 2445J, replacing my old 2425J with 2370 horns, which by the way also had some, not so nice "coloration" when x'ed 550 HZ.

All the low-end is then adequatly taken care of by a pair of (Swedish) Sentec mono blocks ACM 1
The rest is driven by a H/K AVR 5000 (AVR 500, for you over there) The H/K sounds very nice, but has that annoying habit of suddenly turning up the volume, now and then, without even asking me.
Shame on you Harman!!!

But all in all, I'm quite happy with the lot, for the time being.

Oh yeah, I almost forgot to ask. Does anyone know if there is a "magic" line where the horns, I mean any horn becomes "colored", theoretically???

Thanks again for your help and thanks also for this great forum.

BR
Roland

[Robh3606]

Hello Pangea

I am wondering if you are crossing to low for the horns used. If you are below the cut off frequency it unloads and that could be what you are hearing. You should really run some what above the cutoff of the horn figure 1/2 octave. Depends on your crossover slopes and the type of horn flare used. The 2445 should OK at 500Hz. What are your slopes??

"2425J with 2370 horns, which by the way also had some, not so nice "coloration" when x'ed 550 HZ. "

Running 2425 at 500 hz is too low for the driver and the 2370 won't load the compression driver properly that low. Try up around 800Hz.

Oh yeah, I almost forgot to ask. Does anyone know if there is a "magic" line where the horns, I mean any horn becomes "colored", theoretically???

Yeah don't run them lower than they are designed to run. Horns are bandwidth sensitive. That is one potential but, avoidable pitfall of using them. Asside from that I have not played with too many horn types but the three I have tried were all different. You need to try a few out and decide what works for you. My favorite is still the 2344A for a 1 " driver. 2123 is one nice driver! Hey where are the pictures???!!!


Rob

[scott fitlin]

500hz is too low. 800hz would be much better.

[Alex Lancaster]

And if You use 2123H's, 1 to 1.2 KHz., even better.

Alex.

[pangea]

Thanks for all your help!!!

I think I'll play it safe and go for the 1.1 or thereabout, depending on which standard components come closest.

My filter slope is 12 dB/Octave, as suggested by the manual. I did chose the x-over because the manual suggested a minimum of 500Hz with a minimum 12dB slope.
What horns work that low? Does the tractrix go that low?
What about 6 dB slope, where would you set the x-over with a first order x-over and how would you design the filter and at the same time trying to make the frequency response as flat as possible up to 20 kHz?

Pictures, well I dont have any, yet. I havent got around to buying one of those digital cameras, but who knows, maybe Santa will bring me one this year. I'll see though if maybe I can squeeze some useful pictures out of my web camera.

By the way, does anyone have an opinion regarding which 2" driver has the best tonal qualities as well as punch?
A friend of mine says that the 2440 with a 2445 diphragm beats everything else! Any comments on that statement?

BR
Roland

[pangea]

Hi again!

Yesterday I received a somewhat unorthodox suggestion on how to solve my x-over problems. I got it from someone who supposedly is an expert at these things in Sweden. It may well be OK to use his suggestions, but I'm not sure it will give me a flat response in the high/ultra high region or even if it will work properly, since he left out the tweeter R1 9,82 Ohm, serial resistance and therefore I would appreciate your thoughts and opinion, whether you think it could do it for me.

I have attached the x-over as a JBL speaker shop file, if anyone would like to have a look at it.
The cross over is now made with the assumption that I hopefully will soon find a pair of 2123H, which would definitely take away my "coloration" problem at the same time. Abrakadabra!

BR
Roland

[pangea]

Here is the 2445J x-over suggestion, integrated with the rest

[pangea]

Once again the attachment was lost

I'll try once more to attach the picture of the x-over.

[boputnam]

Originally posted by pangea
I have a pair of speakers made by the former Swedish representative Tommy Jenving called "JBL KIT 65 BIG" they are somewhat upgraded with new 2402H...

I don't see the UHF in the schematic...?

So, these are only three-way's, or am I missing something? I think you'd notice improvement with a 2405H on top.

[scott fitlin]

Originally posted by pangea
Thanks for all your help!!!

I think I'll play it safe and go for the 1.1 or thereabout, depending on which standard components come closest.

My filter slope is 12 dB/Octave, as suggested by the manual. I did chose the x-over because the manual suggested a minimum of 500Hz with a minimum 12dB slope.
What horns work that low? Does the tractrix go that low?
What about 6 dB slope, where would you set the x-over with a first order x-over and how would you design the filter and at the same time trying to make the frequency response as flat as possible up to 20 kHz?

Pictures, well I dont have any, yet. I havent got around to buying one of those digital cameras, but who knows, maybe Santa will bring me one this year. I'll see though if maybe I can squeeze some useful pictures out of my web camera.

By the way, does anyone have an opinion regarding which 2" driver has the best tonal qualities as well as punch?
A friend of mine says that the 2440 with a 2445 diphragm beats everything else! Any comments on that statement?

BR
Roland

The 2440 is a great driver. BUT, you put the 2441 diaphragm in it. Aluminum sounds better than titanium. This will give you the tonality and crisp punch your seeking.

[pangea]

OK, my mistake that I wasn't clear enough, but I wasn't referring to the "JBL KIT 65 BIG", when I was describing the x-over. It's the other ones with the 2220A, (the soon to be incorporated 2123H) and the 2445J that have given me a few new gray strains and that is why I'm trying to find the best solution for the cross-over, whether it's a 6- or 12 dB x-over.

I have also been playing with the thaught of putting a 2405 on top of the 2445J, but if a first order (6 dB/oct) x-over can even out the frequency response, then I would think the 2405 can't add all that much, or can it!? But that's never the less a secondary issue right now. My main focus is trying to build the best possible x-over for the JBL 2445J and I'm thinking that I would prefer a first order x-over if you or anyone else, think it will work as suggested by this expert.

BR
Roland

[pangea]

Originally posted by scott fitlin
The 2440 is a great driver. BUT, you put the 2441 diaphragm in it. Aluminum sounds better than titanium. This will give you the tonality and crisp punch your seeking.

OK, thanks for your input, I'll be sure to take it to the source!!!

By the way, what's the difference between the 2440 and the 2441 diaphragms? Why didn't JBL do this instead of putting a weaker magnet in the 2441?
I'm also thinking, why isn't the titanium diaphragm better? Shouldn't it be better?

BR
Roland

[scott fitlin]

The 2441 diaphragm has a diamond pattern surround instead of the rolled surround of the older 40 diaphragm. The 41 has cleaner, more extended top end response.

Aluminum has a sweeter sound than titanium, which tends to sometimes be hard sounding!

The 2441 diaphragm sounds really good in a 2440 driver, I know, because I have done it.