The Vintage JBL West Coast Sound becomes the…

[Swerd]

Swerd - you had said that you used standoffs to hold the crossover away from the damping material. Is there any reason that you couldn't pull the original damping material from the back of the cabinet, attach the crossover directly to the cabinet back, and lay the damping material back (directly over the crossover)?

I only did what I described because I don't like handling fiberglass. I don't know how important stand offs are.

The resistors do heat up some, so I guess there is the possibility that fiberglass covering the crossover might prevent heat dissipation. I don't know if that would be a problem.

 

[bwilkinson]

I guess we'll find out. Thanks for the info.

 

[bwilkinson]

Still waiting for my last components to come in... Well, my first lesson learned - never take the "free" shipping from PE, you could walk to Cincinnati and get parts faster. This is my first (and last) experience with Fedex Smartpost.

One dumb question - which probably nobody has bothered concerning themselves with - any idea where the acoustic axis would be on the L100 after these modifications? I actually plan on using these as a second opinion pair of monitors in my home studio, and am trying to determine what height to set them.

I have a feeling I'll just be playing with them for a while until I find a point.

 

[Swerd]

One dumb question - which probably nobody has bothered concerning themselves with - any idea where the acoustic axis would be on the L100 after these modifications? I actually plan on using these as a second opinion pair of monitors in my home studio, and am trying to determine what height to set them.

I have a feeling I'll just be playing with them for a while until I find a point.

If it helps any, the new crossover was designed with the speaker cabinets sitting vertically on a stand that was about 12" or 15" tall. After trying a lot of different microphone positions, Dennis Murphy settled on placing the mike about tweeter high and about 10 feet distant from the front baffle. I really don't know what will happen if you listen to them near-field. I hope the somewhat steep 4th order crossovers help prevent lobing issues. With the original crossovers these speakers suffered greatly from that problem, so it ought to be an improvement.

 

[bwilkinson]

That's exactly what I needed to know. Typically the axis is somewhat close to the tweeter height, but I knew that a lot of the midrange was still coming through the woofer, so I didn't know if I should raise it up more to compensate or not.

If Dennis' readings were near tweeter height, then that's what I'll go with.

I'm less concerned about the nearfield reaction because I plan on soffit mounting the speakers, putting them about 5' from my ears. I know that the 70 Hz bump will become huge at that level, but it may actually help for me - I have a tendency to make boomy mixes in general, and that boost in those speakers should back me off some. In addition, I believe that Ziltch(tm) plugs that have been suggested will reduce some of that peak.

 

[bwilkinson]

Okay, yet another stupid question...

I have placed all the components on the board, and everything looks nice. Now, some of the inductor leads are entirely too long to connect from one location to anther. I know that there is an insulating coating put on the inductor wire (obviously), so simply cutting to the length I desire and soldering isn't the answer - or is it?

I have read through other forums that the coating can be remove mechanically by scraping, or (if I only had one) by immersing in a solder pot, or chemically using acetone. Some have even said that modern inductor coatings will simply come off when the solder hits the enamel.

So what have you all done? What works efficiently?

 

[Swerd]

Okay, yet another stupid question...

I have placed all the components on the board, and everything looks nice. Now, some of the inductor leads are entirely too long to connect from one location to anther. I know that there is an insulating coating put on the inductor wire (obviously), so simply cutting to the length I desire and soldering isn't the answer - or is it?

I have read through other forums that the coating can be remove mechanically by scraping, or (if I only had one) by immersing in a solder pot, or chemically using acetone. Some have even said that modern inductor coatings will simply come off when the solder hits the enamel.

So what have you all done? What works efficiently?

Sand paper scratches the thin enamel coating off. Tin the newly exposed copper surface, and you should be good to go. A sharp knife blade or a file should also work, but I used sand paper.

 

[bwilkinson]

Okay, now color me confused.

I just took apart my first speaker. Checking the drivers, I have a 123A1 woofer. I hooked a 1.5V AAA battery up, and tested. Positive to Red connection on speaker, driver out. So far, so good. This is the same as the green wire in the schematic, connected to the red "positive" input.

I then went to the LE5-2 midrange. Positive on the battery connected to the red connection on the speaker - driver in. This is what the white wire was connected to in the schematic. So, midrange was out of phase - no problem.

Finally, I went to the LE25-1 tweeter. There is no black or red connection on the tweeter. However, I connected the positive side of the battery to the terminal that the red wire of the schematic was wired to, driver in. Now, I understand that the red wire is actually connected to the "negative" terminal at the speaker cabinet. Why that is, I'll never know.

So, I just want to clarify - on your schematic, everything that connects to the negative terminal of the cabinet needs to be the actual negative terminal of the driver - if I were to hook up a battery with the positive part of the battery touching that terminal, it would move inward.

The three wires coming from the circuitry connect to the "positive" side of the drivers - ie if I connected the battery with the positive side touching this terminal, the driver will move out.

Am I correct?

I was expecting the LE25-1 and LE5-2 to be wired "normally", and MAYBE the 123A1 wired "backward". Now it seems that the 123A1 is wired what I would have considered "normally", and the LE25-1 and LE5-2 are wired "backward". What gives?

 

[Swerd]

So, I just want to clarify - on your schematic, everything that connects to the negative terminal of the cabinet needs to be the actual negative terminal of the driver - if I were to hook up a battery with the positive part of the battery touching that terminal, it would move inward.

Yes

The three wires coming from the circuitry connect to the "positive" side of the drivers - ie if I connected the battery with the positive side touching this terminal, the driver will move out.

Am I correct?

Yes. When you say "the circuitry" I assume you mean the new crossover board.

I was expecting the LE25-1 and LE5-2 to be wired "normally", and MAYBE the 123A1 wired "backward". Now it seems that the 123A1 is wired what I would have considered "normally", and the LE25-1 and LE5-2 are wired "backward". What gives?

I'm not sure how to quickly explain what gives with the old crossover. It has to do with the differences between the old 1st order and new 4th order crossover, and it doesn't matter so long as you wire the new crossover board to all 3 drivers as shown in the schematic diagram. All 3 should have their true positive terminals (as determined by the battery test) wired to the positive side of the board, and their true negative terminals should be wired to the minus or ground side of the board.

This is important, and I hope you are clear about what I mean.

 

[bwilkinson]

I am clear - I was just surprised to see what I found.

As soon as I get more wire (just ran out, making all of my patches between components) tomorrow, I will be actually assembling these. I cannot tell you how much I am looking forward to hearing the difference!

 

[bwilkinson]

Done!

Just finished the wiring the last speaker, and listened.

Let me qualify this, the amplifier I am running it through currently is an old RS MPA-200 - nothing special at all, just sterile amplification. I connected a CD player, and off I went.

Words cannot describe the difference in sound between before and after. When I was waiting to get these JBLs, I had high expectations. I first listened to them, and to say I was not impressed was an understatement. With this crossover, they are everything I want them to be - including the 70Hz bump. It is exactly where I boost sound typically (personal taste). The top end is smoothed right out, the vocal separation is more than impressive. I can hear each individual voice placed in the mix. The location of the instruments is incredible.

I am going to have a whole lot of fun with these speakers. Thank you for all your help, and although Dennis Murphy has no clue who I am, please thank him for the crossover design.

 

[Swerd]

Just finished the wiring the last speaker, and listened.

Let me qualify this, the amplifier I am running it through currently is an old RS MPA-200 - nothing special at all, just sterile amplification. I connected a CD player, and off I went.

Words cannot describe the difference in sound between before and after. When I was waiting to get these JBLs, I had high expectations. I first listened to them, and to say I was not impressed was an understatement. With this crossover, they are everything I want them to be - including the 70Hz bump. It is exactly where I boost sound typically (personal taste). The top end is smoothed right out, the vocal separation is more than impressive. I can hear each individual voice placed in the mix. The location of the instruments is incredible.

I am going to have a whole lot of fun with these speakers. Thank you for all your help, and although Dennis Murphy has no clue who I am, please thank him for the crossover design.

I'm real glad it all worked so well for you . Thanks for all the kind works. I'll be sure to mention it to Dennis the next time I see him. He does enjoy the feedback.

As far as amplification goes, as you have learned, nearly any amp will drive these speakers. With the new crossovers, they are a bit less sensitive (roughly 1-3 dB less) than before, but that should not be a problem. That's what volume knobs are for. Those old drivers are quite robust and can easily handle and sound great with big powerful amps, such as 200 watts/channel. I wouldn't spend big bucks on such an amp, but if you ever find something used, say for $1 per watt, it might be a good buy.

 

[leesonic]

Just got a set of JBL L100s CHEAP

Hi there,

I didn't see an introduction forum for newbies, so let me introduce myself. My name is Lee, I live in South Jersey USA, moved here 10 years ago from London, England. I'm a bit of an old car nut, so my 1970 Mk1 Capri moved here with me, as did my HiFi gear.

Currently, I have a vintage setup in my spare bedroom consisting of a Sansui A-80 amp, T-80 tuner, D-90 and D-100 cassette decks, SR-5090 turntable, and what I call my "bass monster" speakers. I built these 20 years ago with SEAs drivers and matching crossover, with a dome tweeter, 8" and 10" woofers (the 10" runs through a subwoofer crossover).

The other day, I picked up a pair of JBL L100s for $4! The cabinets are a little bit scratched up, one of the tweeters has been pushed in, and they smelt a little musty, but everything is there.

Last night, I connected them up to the setup listed above, in the corners of the room (bad, I know), and had a listen. I was amazed at the sound quality of these speakers. Sure, they have the brash midrange and treble people have mentioned, but they really sounded "ALIVE". I haven't found anything to rival the bass output of my "bass monsters" until now.

I was thinking of building the Dennis Murphy crossover mentioned, but I was wondering, how to they compare to the Jantzen crossovers? I notice they don't list the component values anywhere. I was thinking of putting three toggle switches on the terminal plate, so you can switch between the "west coast sound" (JBL) and "coast to coast sound" (Murphy). Think this is a good idea? Maybe even a switch to reverse the polarity of the midrange to get the authentic JBL sound?

Is it possible to take the tweeter apart in order to push the dome back out? I thought about re-veneering the cabinets, anyone else done this, or has advice on repairing them?

Lee.

 

[Swerd]

Is it possible to take the tweeter apart in order to push the dome back out? I thought about re-veneering the cabinets, anyone else done this, or has advice on repairing them?

Welcome the AH forum Lee . I'll be glad to answer any questions you have.

Those tweeters are 1.5" cone drivers and the dome is really a voice coil dust cover, the same as on a larger driver. You can try to pop it out with some gentle suction, but I wouldn't bother with anything more drastic or potentially desctructive. Other people have poked a small hole with a sharp pin, inserted a bent pin in the hole, an pulled out the dent. They then sealed the hole with a bit of crazy glue. I've never tried that. Tweeters are fragile, and a dented dust cover looks bad but probably sounds alright.

As for the scratched veneer, the original walnut veneer was not varnished. It had a rubbed oil finish. Try rubbing the scratches with fine 0000 steel wool and clear Watco Danish oil, or boiled linseed oil. That may rub out the scratches if they aren't too deep.

I was thinking of building the Dennis Murphy crossover mentioned, but I was wondering, how to they compare to the Jantzen crossovers? I notice they don't list the component values anywhere. I was thinking of putting three toggle switches on the terminal plate, so you can switch between the "west coast sound" (JBL) and "coast to coast sound" (Murphy). Think this is a good idea?

A lot of people have asked about the Jantzen crossover kit. I've never heard it, so I can only point out that the Jantzen kit costs nearly double what the parts would cost for the Murphy design.

When I first built the new crossovers, I did one speaker and spent about a week listening to it and comparing it to the other speaker with the old original crossover. It was a very easy decision to leave the West Coast Sound behind for good. The new crossover sounded much much better. Your opinions, of course, might be different. It would certainly be possible to switch between the two crossovers, but I wouldn't know how to wire all that.

Maybe even a switch to reverse the polarity of the midrange to get the authentic JBL sound?

I am quite certain that is not a good idea. The new crossover requires wiring the drivers with different polarity than in the original. If you switch polarity on the midrange you will get a giant suckout - a large dip in the frequency response - between the woofer and the midrange, and also between the midrange and the tweeter. It would not sound good, and it would not at all resemble the sound with the original crossover.

 

[leesonic]

Welcome the AH forum Lee . I'll be glad to answer any questions you have.

It was a very easy decision to leave the West Coast Sound behind for good. The new crossover sounded much much better. Your opinions, of course, might be different. It would certainly be possible to switch between the two crossovers, but I wouldn't know how to wire all that.

That part was easy. It was just drawing it was the problem. I'm old school, still using PaintShop Pro version 5, I bought version 10 a couple of years ago but it seemed too complicated. Here is a link to the switchable crossover.

home.comcast.net/~leesonic/JBLxover.jpg

I am quite certain that is not a good idea. The new crossover requires wiring the drivers with different polarity than in the original. If you switch polarity on the midrange you will get a giant suckout - a large dip in the frequency response - between the woofer and the midrange, and also between the midrange and the tweeter. It would not sound good, and it would not at all resemble the sound with the original crossover.

Makes sense, I only thought of it because I thought I read earlier on in the thread that one of the drivers is wired backwards from the factory. My "switchable crossover" does away with the L-pads, on my speakers they didn't make much difference anyway. Earlier on in the thread, someone said they might be oxidised, but they feel like wire-wounds to me, less prone to oxidisation.

Until now, I haven't found any speakers with as much bass power as my old "bass monsters" that I made nearly 20 years ago (picture below). They have all SEAs drivers, a dome tweeter and 8" bass wired through a SEAs crossover, the 10" wired through a subwoofer crossover.

home.comcast.net/~leesonic/speakers3.jpg

These have a much more laid back, some would say British sound than the JBLs. It would be interesting to compare the two with the upgraded crossover. That said, I was listening to some Level 42 the other night. For those not familiar with this music, Mark King plays the bass with a slapping technique. The extra midrange of the "west coast sound" allows you to hear his playing style even more.

Lee.

P.S. Couldn't put the full links in as this is only my second post. You'll have to put your own h t t p : / / in front of it, unless an admin wants to edit my post so the pictures display?

 

[bwilkinson]

I Concur with Swerd

I had a similar thought as you did - with regards to being able to put the speaker back to "original" condition for nostalgic purposes. Then I built the first crossover and listened. After doing so, I threw away the old pieces I had removed.

When I rebuilt these, it was with the intent of using them as a "second opinion" for recording monitors. I have a set of KRK RP-8 speakers that I use currently, and thought that they were great sounding speakers. I now feel that the JBLs will be my primary monitors, and the KRKs will be my second opinion - it is that much of a difference.

My daughter - a 16 year old - texts me at least once a week... "Dad, do you mind if I use the JBL's?" It is that impressive.

The crossover does not eliminate the bass response of these speakers at all. In testing, the only thing that I have done is boost the sub bass levels (I hooked up a subwoofer crossed over at 45 Hz, brought in just enough to give a "bump" in the kick drum) and I just sit back and listen.

I cannot say anything about the Jantzen crossover, either. However, I am also a firm believer of, "if it ain't broke, don't fix it." These speakers with the Dennis Murphy crossovers - if I can understate it any more - definitely "ain't broke".

 

[leesonic]

I had a similar thought as you did - with regards to being able to put the speaker back to "original" condition for nostalgic purposes. Then I built the first crossover and listened. After doing so, I threw away the old pieces I had removed.

Yeah, I hear what you are saying. I just figured three DPDT switches, and two new caps per speaker, and I could be able to switch between the two crossovers, if only to hear how they sound.

Money is tight right now though (been out of work since Feb), and $100 for the crossover components isn't really something I can afford right now. I keep seeing the drivers being sold on eBay, woofers for $200, mids and tweets for $100-150. Tempting, but I'd rather keep them intact.

 

[Theresa]

A wonderful walk down memory lane

Its wonderful to read a thread such as this. I listened to them at one time and wasn't impressed, now I have a good idea why. They were far from "perfection." I once was in a wealthy families house and there was a more modern version of these. The adult male raved about them. He wanted to put them in the great room. I sort of withdrew into my shell and refrained from comment. Now I would love to rehabilitate the AR-9s. They were truly great speakers but I'm sure would be even better with modern crossovers and perhaps a different tweeter. There have been so many advances in the science of speaker design that the best today and far better than 40 years ago but as was said most poorly performing speakers can be improved greatly with a good crossover. But that still doesn't dull the nostalgia I feel concerning speakers from my youth. I was very poor for decades because of a disability but desperately wanted good sound.

 

[Swerd]

Its wonderful to read a thread such as this. I listened to them at one time and wasn't impressed, now I have a good idea why…

I'm just getting over a bad cold, the weather is very cold, and snow is threatening. Your comments put a big smile on my face . That made my day. Thanks.

 

[leesonic]

Guess I have enough posts now to post some pictures. Here is the picture of the switched crossover.