Compression Drivers

macrojack · « **on:** 2 Aug 2008, 11:46 pm »

A wild hair has erupted in my psyche and an urge to explore vintage compression horns and drivers is the result. Does anybody have info, advice or product to dispense? Reward!!!

JoshK · « **Reply #1 on:** 2 Aug 2008, 11:51 pm »

you'd be well off reading the giant 'beyond the ariel' thread over at diyaudio.com. lynn goes through a great deal of history and info on comp drivers. then there is oswaldmillsaudio.com which has the rca museum section that goes through some history on rca theater drivers. you had western electric with the 555, rca with a couple of drivers mi8594 or something like that, then altec, then jbl. these aren't all of the vintage cd's but they make up a majority of those that were produced since they each dominated the theater market for different periods, and that is where cd drivers were born from.

what's my reward.

Figo · « **Reply #2 on:** 3 Aug 2008, 12:26 am »

You need seriously deep pockets to explore beyond recent Altec/JBL models (and even then...)

I'd start with a pair of Altec Valencias, or Model 19s.

macrojack · « **Reply #3 on:** 3 Aug 2008, 04:43 am »

Reward is for earth shattering, stop the presses, new data. I've initiated conversations with Jonathan Weiss, Bill Woods and Rick Brown. It is mainly because I don't have pockets so deep that I am posing this line of questioning.
I do, however, have a vintage pair of JBL L-200. The cabinets are quite nice and the contents seem to be as new. But, compared to my Zu Presence, they are lacking. Perhaps I can use my LE-85 drivers with an AH horn mounted on top of the cabinet. I was thinking of bypassing the passive crossovers, buying an appropriate active crossover, and hard wiring the drivers to the amps. For this purpose, I have a Perroux PMF 1850 to drive the woofers and a pair of modified Audio Mirror 20 watt monos for the horns.

I'm feeling a bit like Kevin Costner in Field of Dreams. What the hell am I thinking about this for. My Zus are positively awesome with those tube amps. Do I really want to give that up? Is this a classic manifestation of audiophilia nervosa or something deeper and more pernicious?

Anybody have any feelings about how or why I might proceed?

It appears to me that the cutting edge crowd is marching off in this direction and leading the cost no object people along with them.
But I think that JoshK is right about the movie house thing. During the Great Depression, movie palaces were springing up in every small town in America. It was a growth industry like computers in the 80s but it was not garage tinkerers who were creating the advances. It was RCA, Western Electric, Bell Labs. JBL and Altec were part of it and science was too. The amps of the day were tiny and required very efficient speakers. Compression driven horns were discovered and large theaters were brought to life with a couple of watts. You know the places. You probably attend concerts in them now that the movies are out at the MALL MULTIPLEX.

Anyhow, all of the industry saints cut their teeth in this and many modern audiophiles are suddenly figuring out that we shouldn't have let all that stuff go to Asia. But we were busy buying ever larger amps and laughing at those stupid Japs for wasting their money on that junk. I can hear them having the last laugh now as they stroll off into the sunS.E.T. with our priceless treasures that we mined for them.
I've read that horns fell into disfavor when we started using transistors that sounded bloody awful through the old horns. So we all stocked up on inefficient speakers and kilowatt doorstops. Now the tide is turning and field coils are beginning to top dream lists here and there. And it looks like I'm catching the fever. Is anyone else feeling their temperature rise and their compression lacking?

JoshK · « **Reply #4 on:** 3 Aug 2008, 05:08 am »

I am building a hi-eff OB pair of speakers and have plans for a horn variation to compare, but the horn speakers will take time as I need to spin some big tractrix midrange horns (238hz). The comparison will be to compare the JBL 2123H OB versus tractrix loaded (3.5" throat). The highs are going to be using B&C DE250's in 12" OS waveguides, so they are already there.

John Haskin did the tractrix modeling for me and then I installed hornresp and played around with looking at his design. I think it'll be interesting. The OSwg controlls the CD down to 1khz according to Dr. Geddes and the tractrix is around 90º directivity at 1khz, which was the goal, so that directivity will match between the two.

JoshK · « **Reply #5 on:** 3 Aug 2008, 05:09 am »

FYI, Great plains audio is still making modern altec remakes, so you don't have to pay antique prices, although they aren't cheap.

doug s. · « **Reply #6 on:** 3 Aug 2008, 05:29 am »

i know these aren't compression drivers, but they are horns.

since i have gotten my oris 150's (w/relatively cheap fostex fe206e drivers) & modded klipsch lascala bass bins sporting 15" fostex drivers, i have, for some reason, not been wery interested in swapping out my other speakers. which include, among others, a fine pair of coax-ribbon piega's, & a pair of gemme audio tanto's, that i was dying to hear - and, they have remained in their cartons ever since i got them, several months ago - i haven't even pulled them out to see what they look like "in the flesh"...

one reason i can see why horns went out of favor is due to their size/shape/looks - really quite ungainly. they actually make my vmps subs look small, sort of...

but, i think the sound is awesome! detail, dynamics, soundstaging - it's all there. did i mention dynamics?

(note - the tad ribbon supertweets are not hooked up...)

doug s.

Bemopti123 · « **Reply #7 on:** 3 Aug 2008, 11:59 am »

To make things easier and less cumbersome, I would also look into those Altec 604 variation drivers. Although some might question the size of the horn. It is an awesome sounding driver set. Some pairs are not too expensive, but they are going up in price.

PS: Don't forget the crossovers.

chadh · « **Reply #8 on:** 3 Aug 2008, 01:48 pm »

I have little or no idea about compression drivers, or horns. But I thought I'd leave a little comment about a system I heard at the recent Audio Karma show in Detroit. Classic Audio Reproductions had a room playing vinyl, using AtmaSphere electronics into a massive pair of their T1 speakers. You can get some idea of what these speakers are like from this page:

http://www.classicaudiorepro.com/page5.html

The guy who runs Classic Audio Reproductions has recently started installing compression drivers in these speakers. They aren't vintage, but are new - he has them made specially. They are apparently "field-coil powered beryllium-dome compression drivers". Whatever that means. From an overheard conversation, I gather the drivers are not overwhelmingly expensive (of course, this is all relative).

Anyway, the point is that the system I heard sounded just fantastic. And if I had a big pile of spare cash, and the space and inclination to house speakers the size of refrigerators, I would own those speakers.

Chad

macrojack · « **Reply #9 on:** 3 Aug 2008, 06:17 pm »

Chadh- Thanks for the link and the testimonial.

I spoke with John Wolfe of Classic Audio Reproductions a couple of weeks ago. He told me that the model which represents the biggest bang for the buck in his lineup is the T-3.3 at $12,500 per pair. Big money for big hardware.
A field coil is a driver that employs an electromagnet rather than a permanent magnet. They are said to be better but I don't understand why.

Bill Woods of Acoustic Horns has recommended that I use his AH 700 horn with my JBL LE-85 compression drivers and mount it on top of my existing L-200 cabinets. He says it will be an enormous improvement over the H-91 horn that came in the speaker. I could then either use the existing JBL passive crossover or get an active XO and bi-amp. It would look something like the pictures dougs published above.
This option costs me about $2000 to $2500 in passive mode, plus the price of an active crossover added if I go that way. I already have the amplification.

This email came in this morning:

Hi Tom,

The AH700 is the best choice, but it is more money.
You will have a system secound to none if you go this route.
The AH700 goes deep into the voice range, a better match for the heavy
coned JBL LE15c.
There is no "horn" sound.
I used this system as my flagship model at the Rocky mountain Musicfest.

I use this system myself with a JBL D130 woofer-- less bass, but I like the
voice.

I have sent you a curve, and some pictures.

Bill

PS Here is some info on JBL...

_______________________________________ ____________

So, Bill is making strong promises there and he seems to have the cred to get away with it. Any comments?

JoshK · « **Reply #10 on:** 3 Aug 2008, 06:27 pm »

i'd first have a good look at redo'ing the crossover in the l200. i think it could probably be improved upon.

macrojack · « **Reply #11 on:** 3 Aug 2008, 08:38 pm »

Joshk -

I'm sure you are right about there being room for improvement in my existing crossovers. They are about 35 years old and all original. From what I'm told the caps are probably pretty dried up by now.

Problem is I don't have any idea how to do that and I suspect it might cost me more than an active XO that I can easily resell if this experiment bombs. Everything I've read indicates that an active crossover is always superior because of resistance and inductance issues in passives that are nonexistent in an active. Do I have that right?

It seems that hard wiring the amps to the drivers is the most elegant and foolproof approach.

Scott F. · « **Reply #12 on:** 3 Aug 2008, 09:56 pm »

Jack,

I'm far from an expert on the subject but I've started my travels down the same road. For a number of years now I've been doing fleapowered amps with high efficiency speakers (Lowther PM2A's in an open baffle with vintage 15's in BR cabinets, actively crossed and bi-amped).

Not too long ago I finally got my Altec A7's re-housed. What I did was take the 511 horn and mount it in a separate enclosure. I took the enclosure and filled it with sand to dampen the ringing that is associated with vintage metal horns. The difference is sound was more than noticeable.

I was lucky, a couple of years back I found a pair of Karlson cabinets that were still in good shape. They had a pair of vintage PAX 30 Pioneer coax drivers in them. I found out quick why so few out there don't listen to Karlsons, they (or at least these) sound like hammered sh*t.

So I gutted the box and cut a new front baffle to fit my Altec 416Z's, installed some extra bracing then played with the stuffing until I got even sounding bass. After listening to them for a while, I decided to not install the port and listen to them aperiodic loaded.

Right now I've got a completely new crossover for the Altecs that I'm building on a cutting board. I'm using premium caps, some PIO's in critical places, Goertz foil inductors, power film resistors, that kind of stuff. Unfortunately, I keep having other projects getting put in front of them. I'll get them finished one of these days.

One thing I can say for certain, pull apart your existing crossover and install some good quality caps in their place. You can save your old caps just in case you ever decide to get rid of them. That way you can restore them to the way they were originally. I did this with my Altec XO and it made a dramatic improvement.

I'm not familiar with the horn the JBL uses but the Altec 511 had a screen covering the compression driver. Removing it, the 2" compression driver gained tons more "air" and clarity. The other thing you might try is taking apart the compression driver. Remove the diaphragm and install some damping material behind it. That also definitely improves the sound and focus.

I haven't researched your compression driver but if it is similar to the 511 horn with the 802d driver, it's likely to roll off at about 8-10k. In my case I've rolled a pair of super tweeters in above them to fill in those gaps in the upper registers (Pioneer PT3's with a simple 1st order XO).

Now, the "sound" of my Altecs aren't anywhere near the sound of my Lowther OB's but they are definitely loads of fun to listen to. Right now I've got my Audio Research EC3 (tubed active XO) up at Bill's (Response Audio) being modified (I can't seem to find the time to do it myself). When it comes back, I plan on using it with the Altecs. I'll drive the horns with my 2A3 and bass bins with 300b's (until I get my PP 6L6's built).

I've got a number of different vintage hi-e coax speakers I'll play with one of these days when I get some more time.

Oh, the Classic Audio Reproduction speakers are one of the few sounds that have been stuck in my head for a long, long time. John's repro Hartsfields when I heard them were simply stunning. Granted, he was doing a bit of EQ'ing with the Cello but man, that was some of the best sound I've ever heard. I'd also rank Bruce's Edgarhorns right up there next to them too. The Oris horns using Lowther PM2As as the driver with the Onkin bass bins sounded pretty darned good too. Vintage Klipsch horns and LaScalla's are pretty cool too.

macrojack · « **Reply #13 on:** 9 Aug 2008, 07:47 pm »

Thanks to all of you for your help and suggestions. I've been on sick leave but I'm back in dream mode and looking at horns harder than ever. Bill Woods has advised me to stay with my passive XO and how can I argue?

So that part is decided. Next I have to look inside the crossovers and see what I can see.

Lastly, I need to figure out which is the most cost effective pairing of drivers and horns.

Are any of you in a position to comment on the Acoustic Horn products? I'm very impressed and most likely will buy from them.

nullspace · « **Reply #14 on:** 10 Aug 2008, 06:59 pm »

I have a pair of the AH!1000 horns, and they're certainly well made. And, as you know by now, Bill is very easy to work with. I heard his set-up at VTV in NJ a couple of years ago and was very impressed. My set-up is still a work in progress, so I don't yet have any impressions of how the horns work in my system in my room.

Regards,
John

zako · « **Reply #15 on:** 11 Aug 2008, 12:51 am »

I have always used compression drivers housed in many forms,,Tannoy,,Vitavox,, JBL Metragon,, Then in my JBL Paragon,, Moving up to a modified Khorn useing the wooden Smith horns on the high frequency section and JBL 2441 drivers,, Top drivers now are the TAD 4001 with Smith DSH horns with TAD 703 compression tweeters... All are triamped with 6 Esotec monoblock amps.. Ive been useing compression drivers now going on 45 yrs,.

zako · « **Reply #16 on:** 11 Aug 2008, 01:05 am »

Glad to hear John Wolf is still making the Classic Hartsfield,,, It has now been superceded by a simmiler horn systen now being made by the Klipsch Co. The Klipsch Jubilee,, Its a large horn system Two way,, They also make a pro version 3 way. A compression speaker system to replace the old Klipschorn.. Awsome,,...

macrojack · « **Reply #17 on:** 11 Aug 2008, 02:32 am »

Seems like more and more in audio we are discovering that the past is the future.

merdy · « **Reply #18 on:** 11 Aug 2008, 07:03 pm »

Hi i have played with horns for over 20 years but only in the last 10 that i took them seriously for home audio when some guy in japan played me his set amp with the ad1 tube on a 3 way horn since then i have made many and experimented and listned ,listned ,listned and read read read
you live once and if your ear craves for it ,you have to go for it let alone the trip you will be on you will appericate music like never before and might even enjoy the process of experimenting with hardware
i would say that there are now a lot of very talented folks on the web who know their stuff who will help, i have had more help on this than any marrige consular
the ah horn is stellar on jbl drivers better than most jbl horns for home use once dialled in all your perceptions of horns will change
i use a 4 way horn system with mostly altec components as my main set up
in my work shop a jbl /altec with martin sub
i also use a few tqwt speakers in my bedroom and office

a big magnet a beautiful engineered waveguide a strong lite diaphram a beautiful sexy horn curve whats not to like

macrojack · « **Reply #19 on:** 12 Aug 2008, 02:03 am »

Well I'm shopping for a cabinet maker and trying to align my financial ducks for the mighty assault on Everest. The plan is to build Bill Woods V-Vent bass cabinets to reinforce the efforts of a specific 15 inch woofer. Then buy the AH 300 horn from Bill and attach a B&S driver. Then I have to build (or have built) a 3-way crossover network and acquire the prescribed tweeter. I think this is going to be an incredible speaker system and I am just wetting my pants with excitement over having them hooked up in the living room.
Everyone I know thinks I'm out of my mind to let the Presence go but I can't let go of this idea. I gotta do it. Conical horns rule.