jbl 030 speaker system problem

[man cave audio]

:bouncy:e Hi to all forum members!

:confused: I am brand new to this forum and am posting this thread in the hope that someone can give me some advise with regard to my JBL 030 speaker system.

I bought the speakers in the early 70's (assembled in particle board enclosures: D130W and 075HF) The internal dimensions of the cabinets are 19 1/8" W x 29 1/8" H x 14 1/2" D or 4.67 cu ft. The port size is 7 3/8 x 3 3/8 or 24.89 sq inches. The port size, from what I have read is perhaps a little too small (should be closer to 26 sq")

I love the sound of these speakers but find them overly bright and shrill with certain music sources even though the high frequency adjustment has been turned down. Some of this brightness may be attributed to poorly recorded material, and/or component problems (ie: I found the pickering 3000 cartridge much smoother that a Shure type iv). The amplifier I most often used was a hk citation 12 with a citation 11 preamp. I don't believe they contributed to the problem.

I haven't used the speakers for quite a while (on loan to my son ) but have now started to build a man cave room dedicated to audio where I can rediscover these speakers as well as rediscover "vinyl" which I have missed for some time now. Hence the name "Man Cave Audio" Cave man for short will do!


The room will be approx 8x16 and will be devoted to audio for "music nights" and a big screen tv for movie and sound nights. Of course a bar, kitchenette and washroon completes the setup as adjoining rooms. After all, How else could a proper man cave successfully operate?


I will be using an Anthem AV2 amplifier (125 rms/channel) together with the Anthem TLP1 preamp. I have a Sony psx 4 turntable with an orfofon red cartridge and a project v phono preamp. Also using a Rotel CD player
incorporating a burr brown processor.


:confused: Now that you have a general history, here is my problem:


:dont-know: Are there ways to mellow out these speakers either through cabinet design; change in crossover electronics; or by introducing a midrange driver and a completly redesigned crossover system? Are the cabinet/port dimensions ok?

my main goal is to mellow out the sound of these speakers without sacrificing detail and imaging. If adding a midrange driver is feasible, what suggestions for speakers do you have? Should I have the N2400 crossover rebuilt or should I purchase a new crossover (what kind)? If leaving the two way system "as is" and tweeking the speakers/cabinets in other ways is a better solution, then I need to know this!

I am reasonably knowledgable when if come to audio equipment in general but am "techqnically challenged" when it comes to solutions which involve complex design changes.


Any help anone can give me would be greatly appreciated! I want to do right thing "once" without jeopordizing the integridy of the intended speaker design.


Thanks for listening! Look forward to some replys,

Rock on .......The Cave Man

[BMWCCA]

Welcome!
There are many here who find the 075 ring radiator to be quite shrill and obnoxious. In the range you're having a problem with it won't be from your cabinet dimensions. There is a hole in the mid-range on an 030 since the 075 is being asked to cover to 2,400Hz when in a three-way configuration it would be crossed at 7,000Hz. The "correct" vintage mid-range would be the LE175DLH "potato masher" horn/lens crossed at 1,200Hz and the 075 then at 7,000Hz but that would still leave the "shrill" 075. You could start by rebuilding the N2400. If you search this site using Google search, you'll find the simple schematic. You could find that would help.

As an owner of an 030 system for over fifty years, I have to confess I never was as bothered by the 075 as many here. In the years before I replaced that speaker in my main system I was chasing a harshness in some female vocals that I attributed to the system but never tracked down. My intent was to replace the N2400 with a Crown VFX2A and bi-amp the system but I never got around to it to see if it helped. I also have one LE175DLH I bought with a second VFX2A for a three-way tri-amp experiment but never got the second LE75DLH and took the project no further. I wish you best of luck. I love that old system. Let's see what more knowledgeable members have to say.

[man cave audio]

Thanks for the information!

I did run accross the le175dlh speakers when looking through the library and thought they might work. From what I gather in searching the internet, they are hard to find and very expensive. If one were to substitute a modern day midrange driver what characteristics should it have in order to compliment the D130. Will adding a midrange affect the speaker enclosure design?

I talked to an older audio tech in Winnipeg who is looking into rebuilding the crossover. The schematic you mention would help a lot. How exactly can I find it?


Thanks again


Cave Man

[Mannermusic]

Thanks for the information!

I did run accross the le175dlh speakers when looking through the library and thought they might work. From what I gather in searching the internet, they are hard to find and very expensive. If one were to substitute a modern day midrange driver what characteristics should it have in order to compliment the D130. Will adding a midrange affect the speaker enclosure design?

I talked to an older audio tech in Winnipeg who is looking into rebuilding the crossover. The schematic you mention would help a lot. How exactly can I find it?


Thanks again


Cave Man

There is a PDF of a revised schematic here in the JBL pro data base. Look on the forum introductory page under: Links, JBL Professional links, Network schematics, N2400. You could make one of these and see what you think. But, the primary reason the 075 sounds so shrill is that it does not reach a flat output until 5,000 Hz; there is approx a 10 db rise in output from 2500 to 5000 Hz (as I recall). So, it is impossible to get a smooth blend between the bass and treble. Back in the 60s we didn't worry about that stuff so much - loved all that hi frequency splashiness! But, it drove most of us crazy, eventually - same as you. Inserting the 175DLH will flatten the response as BMWCCA indicated. However, it sounds significantly different and not everyone thinks for the better. The 030 system is a classic in a 6 cu ft enclosure. Good luck!

[Baron030]

As a 030 system owner for over 36 years, I am trying to think of what could be cause the system to sound overly bright. If the shunt section of the L-Pad would have failed, then turning it down would have little or no effect. You don’t state the age of your 030 system. Very early N2400 crossovers do not have 2 – 5 ohm 10 watt resistors, which act as a -8.5 db fixed L-PAD and is used in addition to the variable L-Pad. Testing the L-Pad with an ohm meter would reveal any problems with that component. Another possibility is that the 075 diaphragms are cracked. You should be able to look down into mouth of the horn and see a portion of the diaphragm. This test would not require any disassembly of the 075 driver. So, if you don’t see any crack then the diaphragms may not be the issue.

If you want to overhaul the N2400 networks then refer to the following link: http://www.audioheritage.org/vbulletin/showthread.php?12938

On the other hand, if you plan on adding LE175DLH "potato mashers", then you will need N1200 and N7000 crossover networks to be period correct. The N7000 network would be easy to make. But, the N1200 network has a tapped-coil in it and so it would harder to make scratch.

Baron 030:)

[man cave audio]

I found the schematic for the n2400 rebuild and I read your thread (Baron) on rebuilding the crossover. These are both a great deal of help. I am still unsure of what to do, but now at least am aware of what the problem may potentially be. I am really glad I joined this forum because without your input, I would not know what to do to improve my 030's. Thankyou both for your advise!

I bought the speakers in 1975, the serial number on the crossover is 47393. These speakers have never been abused but are obviously very old.

I am very handy but am not an electronics expert. I am more of a carpenter and plan to refinish the cabinets once I figure out how to fine tune the sound of the speakers. I'll post pictures of the before and after, and of the "man cave".

Please be patient with me because as much as I realize that both of you have a perfect understandinding of electronics, I on the otherhand, don't even know how to check the measurements on the components that you have recommended. I have also read other articles on building crossovers. On the surface it seems easy, but again, if you have never done this, it is a little overwhelming.

I'm in no hurry since this is my winter project. I am currently doing renovations on the sound room and am getting my audio component in order. These speakers are my last project.


Although I am hesitant about rebuilding or building a new crossover system, as the saying goes, " the Lord hates a Coward", so I think I'll give it a try. I still think a modern midrange speaker might be the way to go. I know this strays from the classic build but if it doesn't work, I can always go back to the original design.


What do you guys think? Again, I am looking for suggestions on an a choice for a midrange speaker as well as a guide to where to cross over the frequencies. Is there a "good" prebuilt crossover that will work or is a custom built crossover the only alternative? I really don't know, so I hope your advise will help.

My hope in the end is to get the best possible sound from the 030's using modern day solutions.


Thanks again for your patience and your help!

Cave Nab

[BMWCCA]

My hope in the end is to get the best possible sound from the 030's using modern day solutions.

In that case, you may as well simply get modern speakers.
An 030 is what it is. No point in making it what it isn't. Next you'll be complaining about the lack of bass and ditch the D130. :banghead:

[man cave audio]

That's not my intention. I have a pair of Bose 901 series iv. I could easily use these. Very detailed and with the right placement, very good bass.


I will probably use both speakers. The point is that I still like the 030's and if changing them is a mistake then I can relate to your point of view. On the other hand, if I can improve the sound i9n the mid to upper range, would be happier with mu old favorites. If you have any suggestions in that regard, good, oif not thats ok too!