JBL 2420 Horn Options - Suggestions Please

[wlk]

Zilch

You are right. The stock 2344 horn does not have ports. The 2344 is a two part horn assembly, the 2344A is a single part assembly. The 2344A has a tendancy of breaking at the throat if not handled gently. I have a pair of each in my two sets of 4430 clones. I cannot tell any differrence in sound quality between the two versions of 2344s but I prefer the first version for their durability.

The 4320 / L200s are some home brews that somebody made I would guess close to 35 years ago. They have all the drivers of a 4320 - 16 ohm system with a 3115 - 500 Hz crossover in L200 style cabinets. Yah, they should sound like crap and they did before I re-ported them, but they are now surprisingly good. The mid range bloom may not be accurate but it sure makes horns and vocals sound great. They are not as accurate, well controlled or have as good bass extension as my 4430 clones but as I keep saying "what a midrange". I spent my mis-spent youth sneaking in the back door of bars, honky tonks and rural dance halls (because I was under age) playing with blues rock bands and those horns and vocals on the old home brews sure sound like live horns and vocals to me. It makes the hair on the back of my neck stand up - just like the old days. Hey go figure - sometimes thing that are not logical work very well for a specific purpose.

I would not trade my 4430s for the old home brews but for my next speaker build project I would like to recreate some of the mid range magic of the old home brews.

Toddalin

Thanks for the information on the P Audio PH230 horns. Do you have a suggestion for an adapter to use for attaching these horns to a standard 3 bolt 1 inch JBL driver like a 2420 or 2426?
By the way I was rescued from my own stupidity by blind luck on the PH316 horn. I ordered them on line from a supplier who had them listed on their website. They phoned me this morning and the PH316 is no longer available.

I have had some private mail suggestions from form members that indicate that the characteristic mid range bloom on the old home brews is partly due to the crossover point being 500 Hz. They have suggested that I use a 1.5 or 2.0 inch MF driver and a HF driver if I want to recreate the mid range characteristics of the old home brews but with far more accuracy and control.

[toddalin]

Toddalin

Thanks for the information on the P Audio PH230 horns. Do you have a suggestion for an adapter to use for attaching these horns to a standard 3 bolt 1 inch JBL driver like a 2420 or 2426?

It doesn't need any adapter. It comes with holes for both the 3-hole, 1" drivers, and can be used with the two outter holes that mate with the two outter holes on the 2425 drivers (as I did).

[wlk]

Toddalin:

Thanks for the additional information on the PH230s. I am going to order a pair and try them.

Any advice on the crossover point? The specs say 600 HZ but that seems a bit low considering the horn size.

Regards
Wlk

[Earl K]

Any advice on the crossover point? The specs say 600 HZ but that seems a bit low considering the horn size.

Hi,

For some insights about this horn, I'd suggest reading the thread that contains some CLIO measurements of the PH-230 using various JBL drivers

- Assuming you are "tight-packing" the components ( less than a few inches between the woofer edge and horn edge ), I'd first try out a 2-pole highpass point around 800 hz for this horn . This can work well when crossing to a 4-pole lowpass ( same frequency ) on the woofer . It's a lot easier to test out this concept if you apply a sweepable electronic crossover ( only on ) the lowpass ( woofer ) section. Having a tunable delay function on the electronic crossover also helps . The delay function can really help the blend between hipass & lowpass .

- This approach ( going more or less 4 pole ) should allow you to maintain absolute polarity for both the woofer & horn ( rather than flipping polarity on one of them, merely to satisfy phase requirements in the crossover area ) .


- Here are more pics from the mentioned thread . ( You can thank Zilch for these plots )

[toddalin]

Toddalin:

Thanks for the additional information on the PH230s. I am going to order a pair and try them.

Any advice on the crossover point? The specs say 600 HZ but that seems a bit low considering the horn size.

Regards
Wlk

I use a modified version of the L200B crossover (keeper crossovers) that crosses over at about 800 Hz. I use these with W10GTIs.

I assembled the primary components then went in with the Behringer RTA and worked on the HF compensation (very important for a semi-flat response). I still get some of the classic 1-2KHz "hump" (~3 dB) with some HF roll-off, but it is vastly improved over using no HF compensation.

My HF compensation scheme may or may not work for you depending on the efficiency of the woofers. The W10GTIs are very inefficient, so I use large value resistor in series with the horn and a fairly small resistor to ground after the 24 mfd cap. But, I also put a 1 mfd cap and a fairly small resistor after the 16.5 mfd/choke combination to let the highs through. I even tried a 0.1 mfd with no resistors in parallel with the 1 mfd cap and this really brought out (i.e., helped flatten) the highs (as shown on the Behringer) above 10kHz. But I really couldn't hear these extra highs so figured that there was no sense in pushing the horn that high and introducing a possible distortion.

I was looking for my schematic, but did not locate it off-hand. If you really want to persue this, I'll scour the house when time allows and try to scan a copy for posting.

(BTW, as I noted earlier, the HF compensation is totally different between the PH-230 and JBL 2370 even using the same driver.)

[wlk]

Earl K & Zilch

Thanks for the pointer to the CLIO measurements of the PH 230 and the excellent plots. It appears that the usability of the PH 230 at 800 Hz is questionable. It appears that a 1K Hz crossover point would be much more suitable.

I am planning on tightly packing the LF driver and the HF driver / horn like I did on my 4430 clones so I do not have to compensate for any time delay / phase shift.

Toddlin

Thanks for the additional information. I will be using a 2235H LF driver and I am planning on building a L200A crossover with a 800 Hz crossover point and HF compensation. I would be very interested in seeing a schematic of you final crossover design when you have time to locate it. There is no panic since I am currently collecting components and choosing a preliminary design. I will not start building until I have some time next winter.

Your comments on the difference between the PH 230 and the 2370A have tweeked my curiosity. Can you provide more information on the subject since I had initally considered trying the 2370A for this project.

I am also having a problem finding a pair of PH 230s. On Wednesday evening I ordered a pair from US Speaker as recommended by a form member via the Web. Al from US Speaker called me this morning and indicated that he only had one in stock and that he could not get more because they are discontinued.

Does anyone have any suggestions for another supplier where I might find a pair of PH 230s.

Regard
WLK
(In the still rainy and cold Pacific Northwest - What happend to spring? - Where is this global warming we keep hearing about?)

[wlk]

Toddlin

Sorry! I ment to say that I am planning on building a L200B (not L200A) crossover.

Regards
Wlk

[jcrobso]

I think a little clarification on the lens is in order.

(1) The only reason they angle "down" is to save on depth. If you look at the 2390 they alternate up+down for the same reason. If you look at the lens from the side, the front of each plate is in a vertical line so there is no "push" up or down.

(2) The cutout in the middle of each plate means that there is less "interference" and the waveform is unchanged. AS the plate gets longer there is a diffraction effect and the waveform is "bent" towards the outside - giving the combo a wider horizontal pattern. The large 2395 ( 36" ) goes to 140 degrees because of it's additional plate depth *and* width.

(3) The lens has nothing to do with time delay unless a cat knocks one off the cabinet and it breaks. Then it's time to delay it's dinner and warm housing.

meow.

The sound wave slows down as it passes through the lens then speeds up again once it leaves. The cut out in the center allows the that part of the wave to speed up first and this causes the wide dispersion. Similar to wide angle projection lens on a slide projector. John

[Hoerninger]

The speed of sound changes throught the lens.

The sound wave slows down as it passes through the lens then speeds up again once it leaves.

When this holds for acoustic waves than you can build a virtual box enlarger. Just place a stack of sheets behind a woofer, the depth is increased.

But I better argue with the longer way in a lense performing a time delay, look at posting 8.
___________
Peter