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View Full Version : Extending HF of 2461 drivers w/2425 diaphrams?



Kevin
03-01-2013, 04:55 AM
Hello - I have a question about extending the upper range of some 2461 drivers. I have a pair that are mounted to 2345 horns in custom HF cabs. I replaced the diaphrams with factory 2425's almost 25 years ago when I purchased them (2nd hand). They have been in service as the high frequency drivers (crossed at 2.5K) for a PA system that I used for over 2 decades as a small to mid sized club system.

I never checked the specs on the 2461 until about a week ago and was surprised to find that they were only rated to about 12K with the original phenolics. Since then I've read a bit of anecdotal info about extending the range with newer diaphrams like the 2425 (which is what I did - without realizing what I was doing), but nothing concrete on what HF can be achieved with the alnico magnets in the 2461 compared to using a 2425 or 2426 driver. I would expect that the diaphram would make most of the difference in HF response, but dont know for sure. Does anyone know?

Also I havent been able to find any info on what is the natural roll off for the 2345 horns. Does anyone have experience with this? I've never had a problem with the HF output and my RTA says they are fine up to 20K - but that is with pink noise, which doesnt tell me if the output is colored or distorted. According to JBL, the 2345 horns were mostly used as high mids for vocal reproduction. The highs sound OK to me - but for all these years I've been blaming all the sound coloration that I hear on my mid packs and its certainly possible that the high packs are contributing as well.

These days I still take the PA on the road now and then, and occasionally run it hard - but mostly it stays in my basement as a practice PA, in-house PA for parties, and oversized stereo system. So I'm looking to improve the accuracy, without sacrificing too much SPL.

The weak link in the system sound fidelity has always been my mid packs - horn loaded PAS 10's - which are good for filling up a big room, but sound kinda honky up close - so I'm getting ready to build some new mid-high cabinets with two front loaded 10's on each side. I was planning to put the 2461's with the 2345's on top and get everything in a single mid-high cabinet, however I dont want to put a lot of effort into making my mids sound nice up front, only to find that the highs are not really cutting it. I'd like to keep the 2461/2345's if possible - partly out of of nostalgia and partly because I already have them in hand - however, if I can find something better for reasonable money, I'm open to that as well.

Bottom line - can anyone tell me if the 2461/2345 combination can be made to adequately cover the full HF range (or reasonably close to it) in a smallish system with the right choice of diaphram, or would I be better off trying to sell these and replace them with something like a used 2425 or 2426 driver which seem to have been made more for this application? Would there be an HF advantage to swapping the 2345 to a 2370 horn? Also, does the HF response of the 2425 diaphram degrade over time (ie after 25 years, would there be any benefit to getting new diaphrams to improve HF response - even if the existing ones seem to be working fine)?

thank in advance for any advice - Kevin

macaroonie
03-01-2013, 05:24 AM
Hey there Kevin and welcome to the LH forum.

Some quick observations , the 2345 is indeed old school and the old implementation as you will recall usually involved bullets (075 / 2402 ) for the highest frequencies. That horn is known to have a bit of the classic bell activity due to its metal construction. Some damping material in the cavity above and below the front lip is the cure. Usually car body sound deadening mastic is the preferred option here.

Others will tell you more re the polar charactristics of that horn , it will tend to beam somewhat at higher frequencies and some of the more modern horns will do a better job.

In all probability your mid box could use some taming if the system is a bit shouty so you are on the right tack. I'm not entirely sure that 2 x 10 is the way to go here. You might want to look at what JBL have been doing lately with pro boxes.

Specifically the 2206 is a very capable mid/ bass driver that will play up to 1000 / 1200 HZ and sound clean. There is a ton of info in the forum and on the web about this driver. Nice and easy to implement a single 12" whether you use it in a horn or normal it will do the job for you and is 600W rated so its pretty bombproof.

You might want to give us some more info re your crossover situation, amps etc , there are folks here with way more knowledge than me that will chime in with the real down and dirty. It is the case that some of that old gear can be made to sound very very good indeed.

Good luck ... Mac

OOPS I just re read your post , you say you are crossing mi - high at 2.5KHz , that is nice and easy for the horn but is probably optimistic for the mid driver , it is probably getting a bit nasty at that kind of frequency. Maybe come down lower with that changeover.

Kevin
03-01-2013, 09:49 AM
Thanks Mac,

Yep, as I've been learning more about the 2461/2345 combination, I've realized that it usually had some sort of UHF tweeter on top. I'm fairly sure that replacing the diaphrams with 2425's increased the HF response, because the system has never lacked for high end. OTOH, until the past few years, I've been more concerned about projecting to the back of medium size (150-400 person) rooms with reasonable clarity, rather than accuracy or sounding good up front (which is usually dominated by stage volume anyway)

The crossover is a Rane 23B, which is a 24db/octave active crossover. The mains are all QSC amps, with an MX700 driving the highs. I havent tweaked the crossover points in a long time, but my recollection is that 2.5K gave the best overall sound for the mid/high point.

One of the reasons that I want to stick with 10s for the mids, is that the ones I've seen that are made to be midrange drivers tend to be reasonably flat until 4-5K or so. I've got two pairs of EVM-15B's in ported front loaded cabinets on the bottom, crossed at 400hz, so I dont really need the low frequency response of a driver like the 2206. The 1080C's that I'm using now actually sound pretty good in the back of a decent sized room - its up front where they are lacking. Since I dont really need the long throw so much anymore, I'm hoping that putting them in sealed front loaded boxes will get rid of the honk up front.

About 20 years ago I moved the bass drivers out of scoops and into front loaded, ported cabinets, which made a huge improvement in the low end response, with only a minor loss of volume. So I'm hoping that I can do something similar with the mids and highs and get better accuracy from the same components by building new cabinets that are better designed for the application. However, its only in the past week or so that I realized that for all these years I've been running the 2461's a lot higher then they were originally intended, and I'd hate to build a new set of cabs, only to move the weak spot from the mids to the highs - so I'm hoping that there is someone on this forum who has used 2461s with newer diaphrams and can confirm that this will work (or not)

One advantage to going with a horn like the 2370 is that its physically not as wide as the 2345's - so I could make the mid-high boxes a little narrower. The main advantage to the 2345's is that I've already got 'em. Plus, they are old school and look kinda cool. But unlike the 2370's, I havent been able to find any info on what the frequency response for the 2345 is supposed to be. Does anyone know? Better or worse than the 2370? Or is there another horn that would be better suited as the main HF horn in a smallish (1300 watt per side) system that will sound good close to the front and still be able to project into a medium size room on occasion?

spkrman57
03-01-2013, 10:09 AM
I have a pair of the 2206J's which are 16 ohm other than giving up the bottom octaves it is very smooth in the midrange without any glare like most mid drivers run harder than home HiFi levels.

Just my 2 cents worth of opinion.....:blink:

Regards, Ron

macaroonie
03-01-2013, 11:48 AM
Hi Kevin , cheers for the details. My gut feeling with what you have said is that your x/o points overall are too high. In each case you are running a deal higher than the optimal band for each driver ( in a hi fi sense ) I would be looking at 300 or less for your 15's and bring your HF down to 1500 or even 1200. Thats still high enough to not stress the HF driver in PA use but takes better advantage of the horns' abilities.
In this scenario the 2206 mentioned will play great throughout the range and will not sound honky at all even in a conventional box. In fact it will tolerate a fairly small sealed box in this application and given that you can ladle power into that driver , efficiency is not really an issue.

As far as your HF driver is concerned , since you have installed a 2425 dia in there you effectively have a 2425 and it should play cleanly as high as you will need to go.

The 2345 is a Radial horn and has different traits compared to a 2370 which is a CD horn. The Rane carries compensation for a CD horn I assume ?? If not you will need to think around that issue as these (CD ) horns need a rising respose from the amp to play a flat response to the room.
I say stick with the 2345 but do a bit of damping on it , they do tend to ring somewhat. Years since I had my mitts on any mind you. Most of them are probably beer cans now 8</

Here is the poop sheet on the 2345 http://www.jblpro.com/pub/obsolete/radial_horns1.pdf

Mac

As an afterthought , with your HF running from 2.5KHz up you could be using a horn throat with a mouth the size of an envelope. This is tweeter territory.

Kevin
03-02-2013, 10:30 AM
Thanks again Mac. That spec sheet is partly what got me concerned in the first place, because the HF response on the 2345 seems to roll off a lot faster than the 2370. However the 2345 response curves were done with a 2410 driver, which could be responsible for much of the rolloff because it quits at 15K. I havent been able to find any plots of the 2345 horns with a full range driver. I'd like to think I'm getting better performance from the 2345 horns with the 2425 diaphrams, but maybe not.

If no one at this forum is currently using the 2345s and can vouch for them in this application (which I suppose should tell me something) then I might try to find a reasonable priced spectrum analyzer for my laptop and check the response myself. I may be able to get a ballpark idea with a sign wave generator and my outboard RTA.

According to JBL, the 2370 horn is a bi-radial, not CD. Looking into this some more, it appears that JBL made the switch from radials to bi-radials sometime in the 80s, presumably to reduce HF beaming. My Rane does have EQ setting for CD horns, but I'd have to pull it and open the case to change it, which would be a PIA, so hopefully its not really necessary for the 2370s. If the 2370s werent so overpriced, I could just get a pair and A/B them with the 2345s before building new cabs. I may see if I can find a pair of 2nd hand clones or maybe borrow a pair of loaded 2370s. Presumably, JBL wouldnt have replaced the 2345 with the 2370 unless there was a clear sonic advantage to doing so, but maybe the 2370s were just cheaper and easier to cast.

One advantage to the 2370s is that they are a lot lighter than the 2345s, so would be better in a high/mid cabinet. If I keep the 2345s, I might just fly them since I have 8 foot ceilings in the basement. That would make the system harder to move, but I try to avoid that as much as possible these days anyway.

Hadnt thought about making the 2345s into beer cans, but now that you mention it, if I dont end up using the 2345s and no one wants to buy em, these things will be worth a tidy sum at the scrap yard.

I'll see if tweaking my crossover points helps the sound of the existing cabinet setup, but I'm skeptical that this will help until I have better mid boxes. I spent some time tweaking it when I front loaded my bass cabs 20 years ago - although at the time, my main priority was SPL. Thats why the low-mid is set a little high. I have more headroom in my bass cabinets, so this lets me push the midrange drivers harder in their band.

The advantage I see to having two 10s for the mid packs is that when the room is full, the bottom driver will be at about shoulder level which should cover the dance floor area fairly well and the top driver will be just slightly overhead, for reaching to the back of the room. I might even angle the bottom drivers into the room a little bit to improve the sound near the stage. I'f I'm by myself or just a few friends over, ambient room noise is much less, volume is down and having the drivers front loaded should sound a lot better

now off to play with my crossover.....

Kevin

Kevin
03-04-2013, 06:13 PM
I spent some time over the weekend tweaking my mid/high crossover point. For now, I'm going to keep the crossover at 2.5K. If I go lower, its hard to tell the difference in the room, but closer to the speaker stacks the high mids (1.3K to 2.5K) dont sound as good coming out of the horn at high volume. Too harsh up close. Part of the problem is that the 2345's are right about at head level now. When I rebuild my mid cabs, the 2345's will be further up overhead so wont tear your head off up close. If I can fly them, that should help even more. After 25 years, new diaphragms probably wouldnt hurt either.

I searched through all the comments I could find on this site about the 2345 and it seems like the majority of folks think the 2345 was a bit of a dog, although there are some nice wood horns that have copied the shape. I bought a used factory 2370A off ebay, so I can A/B it against one of the 2345's in some different configurations. If I come up with anything notable, I'll report back. IMHO the 2345's look better out of their cabs than in them, so I'm going to see if I can figure out a way to fly them naked without making them even more prone to ringing.

I decided to ditch going to a single mid/high pack on each side and stay with separate cabinets for mids and high. That way, I can front load my mids now (which should make the whole system sound better) before before making final decision on the horns.

I may also get a new diaphragm and see if it makes a difference in the sound and/or how far down I can cross either horn before they get harsh. Searching this forum, I saw there was a fairly big debate on the forum about 5 years ago on factory vs aftermarket diaphragms. At the time, the consensus seemed to be that factory sounded better, whether or not it was worth the 3x premium was subjective. Without re-hashing an old topic, have any of the aftermarket mfgs notably stepped up their game in the past 5 years?

short_circutz
03-09-2013, 09:58 PM
I have 4 of the 2461 drivers. They were originally installed on 2397 horns with throat adapters over 4 4560 cabinets loaded with 2220's. These were originally installed as a center cluster in a roller arena here around 1977 or so. In about 1990, we were approached by a club about installing a system in the bar, so we had them purchase these cabinets from the now closed roller rink. Before installing them in the club, we retrofitted the horn drivers with 2425 diaphragms, which definitely extended the high frequency extension.

Around 4 or 5 years ago, the club went through an extensive renovation and the JBL cabs were decommissioned, replaced with a pair of SR4731X cabs over 6x Martin 115 low frequency bins.

I now own 2 of the 4560 bins, which I reloaded with E140 and 2345 horns, with the 2461 drivers. I've also used these horns originally with 2425 drivers. I find the 2345 horn sound better with the modded 2461's on the horns. With 2425 drivers on them I always found myself giving them eq very similar to a CD horn in order for them to sound nice.

I do have a pair of 2370 horns that I had purchased with 2426 drivers to use over a pair of 2202's in reflex boxes. The 2370 horns may be advertised as a bi-radial horn, they have the response characteristics closer to a CD horn, and take similar eq. The frequency response you could get from them is a lot nicer than the 2345 horns.

Hope this helps you.

badman
03-11-2013, 12:08 PM
The 2425 phragms are not a good choice for extended HF. Look to a separate driver, or find BE phragms (or even Al) if you want to squeeze more than 10k out.

4343
03-12-2013, 01:07 AM
My 2345's sound sweet with Aluminium diaphragms. Originally they had 2461's on them, which got replaced with 2420's. Now they have 2425's with Radian diaphragms, which handle a bit more power than the 2420's with their original diaphragm's but sound very similar.

I have never run any of the 1" drivers below 2.5KHz for SR use, part of the reason my 2420's still have the (almost*) original diaphragms.

Still like the 2461 too, it can take a pounding all night long, even surviving a dropped mic that slammed it into the phase plug once or twice, something that would have cracked a 2420 diaphragm. Just need a slot above 10K to fill in the top.

*One of my 2420's died soon after I bought them from a singer that got tired of replacing the diaphragms, seems he was driving them with a 3122 passive XO @ 1.2KHz. I tried that once, and only once...

jbl
03-15-2013, 04:47 PM
I've been using the 2425J/2370 combo in my main system since 1985. Very life like sound. The 3110A cross over (800 Hz) has worked well with either the 2225H or 2235H woofer in the 5 ft3 4507 cabinet. The 2370 is a very good horn for home use.
IIRC, the spec sheet for the 2425 (back page) has the frequency plot for the 2425 mounted with the 2345. I do believe that the compression driver spec sheets from the 1970s and '80s were all derived from the 2345 horn. Posting from memory. I may be wrong.