The Vintage JBL West Coast Sound becomes the…

[sterling shoote]

This has been a very, very informative thread on a very romantic subject. I bought a pair of JBL L100t3's, L20t3's, and a B-380 sub back in 1987. I use these today in a 5.1 system. Although these speakers are now over 30 years old, they still satisfy. I had to replace the foam surrounds for L100t3's and the B-380 about 2 years ago; and, now these speakers will out last me. Frankly, in the years that I've owned these speakers the only other consideration for audio improvement has come from an opportunity to listen to the JBL L300's. I like their seemingly effortless ability to deliver rock genera's at outdoor concert levels for closest thing I've heard so far to life-like. Thing is, I still can't afford any in excellent condition that have come available.

 

[thedrub]

I'll echo @sterling shoote, and others. This is an amazing thread.

My L88 Plus 12 ("Acoutically identical to the L100") was purchased from Warehouse Sound Company, in Feb 1975, and has served me well all these 42+ years. About $300, according to the warranty card I taped to the back. They have always been with me over the many, many miles.

Recently, my wife broke off one of the spring terminals so, it is time to violate these beauties and invade her internals. So, I looked around the web and found this thread, which has very much interested me in a new crossover. Arrrrrrrg. Don't I have enough projects around here without you guys causing more problems with my domestic tranquility?

The easy part has been handled. Ordered the banana posts. Took one apart and dismantled the aluminum box encasing the spring terminals. Will get them back on line while I research ordering all the other parts. Then, we'll go for a round 2 by building the replacement crossovers.

Looking around the web was quite surprising. I see L100s going for around $1,200 to $1,500. Zowie. And the 2018 version of the L100s are $4k. Holy crap! Replacement foam is around $230 to $300. Did I mention that I paid $300 for the 1975 originals?

Another project will be to do a little light sanding of the exterior and refinish with oil. The foam grill failed many years ago, and I built a fabric grill to replace it. May have to change the fabric color to suit my wife. I'll try to take some photos and post, if anyone is interested.

One thing surprised me. The wire gauge that was used seemed really small. Maybe 16 ga? These were supposed to be able to take a lot of abuse, so I expected something more like 12 ga. Must be OK since I haven't seen the topic discussed in this thread.

Question: What gauge wire should be used in assembling the crossover components?

Thank you, thank you for all the work to design and make public the design. Very generous, and appreciated. I pulled the schematic, parts list, and the layout guide.

 

[lovinthehd]

I'll echo @sterling shoote, and others. This is an amazing thread.

My L88 Plus 12 ("Acoutically identical to the L100") was purchased from Warehouse Sound Company, in Feb 1975, and has served me well all these 42+ years. About $300, according to the warranty card I taped to the back. They have always been with me over the many, many miles.

Recently, my wife broke off one of the spring terminals so, it is time to violate these beauties and invade her internals. So, I looked around the web and found this thread, which has very much interested me in a new crossover. Arrrrrrrg. Don't I have enough projects around here without you guys causing more problems with my domestic tranquility?

The easy part has been handled. Ordered the banana posts. Took one apart and dismantled the aluminum box encasing the spring terminals. Will get them back on line while I research ordering all the other parts. Then, we'll go for a round 2 by building the replacement crossovers.

Looking around the web was quite surprising. I see L100s going for around $1,200 to $1,500. Zowie. And the 2018 version of the L100s are $4k. Holy crap! Replacement foam is around $230 to $300. Did I mention that I paid $300 for the 1975 originals?

Another project will be to do a little light sanding of the exterior and refinish with oil. The foam grill failed many years ago, and I built a fabric grill to replace it. May have to change the fabric color to suit my wife. I'll try to take some photos and post, if anyone is interested.

One thing surprised me. The wire gauge that was used seemed really small. Maybe 16 ga? These were supposed to be able to take a lot of abuse, so I expected something more like 12 ga. Must be OK since I haven't seen the topic discussed in this thread.

Question: What gauge wire should be used in assembling the crossover components?

Thank you, thank you for all the work to design and make public the design. Very generous, and appreciated. I pulled the schematic, parts list, and the layout guide.

I'd like to see some pics! As to the gauge inside, the distances are very short so it doesn't matter as it would with a 30' run....

ps Always a good site for things speaker wire http://roger-russell.com/wire/wire.htm

 

[Swerd]

My L88 Plus 12 ("Acoutically identical to the L100") was purchased from Warehouse Sound Company, in Feb 1975, and has served me well all these 42+ years. About $300, according to the warranty card I taped to the back. They have always been with me over the many, many miles.

I know the L88 was a 2-way with the same woofer and tweeter as in the L100 3-way. Does the L88 Plus have the mid driver added?

Recently, my wife broke off one of the spring terminals so, it is time to violate these beauties and invade her internals. So, I looked around the web and found this thread, which has very much interested me in a new crossover. Arrrrrrrg. Don't I have enough projects around here without you guys causing more problems with my domestic tranquility?

The easy part has been handled. Ordered the banana posts. Took one apart and dismantled the aluminum box encasing the spring terminals. Will get them back on line while I research ordering all the other parts. Then, we'll go for a round 2 by building the replacement crossovers.

On my L100s, once the woofer was removed, it was easy to remove the spring terminals from the inside of the cabinet. Replacing them with larger 5-way banana terminals was also easy as I used the holes that already existed. I probably do not have any photos of that.

Another project will be to do a little light sanding of the exterior and refinish with oil. The foam grill failed many years ago, and I built a fabric grill to replace it. May have to change the fabric color to suit my wife. I'll try to take some photos and post, if anyone is interested.

A number of years ago, I did a gentle refinish on mine. I didn't sand, instead I rubbed the veneer with #0000 steel wool dipped into Watco Clear Danish Oil. It came out very nice.

One thing surprised me. The wire gauge that was used seemed really small. Maybe 16 ga? These were supposed to be able to take a lot of abuse, so I expected something more like 12 ga. Must be OK since I haven't seen the topic discussed in this thread.

Question: What gauge wire should be used in assembling the crossover components?

As lovinthehd said, short lengths of thinner gauge wire make no difference at all. When I did mine, I used 16 g wire because soldering with thicker gauge wire is difficult.

Good luck with building and installing the new crossovers. If you have any questions, just ask on this thread.

 

[STRONGBADF1]

I don't remember seeing this... nice job swerd! Makes me want to open up my old Ohm Model C's and see what's in there. I have various older speakers... I wonder what could be done with some old Cerwin Vegas... nobody likes them and I have not one but two pair... could it be the crossovers fault all this time???

Sent from my SM-G920V using Tapatalk

 

[PK Vintage]

I have thought long and hard about changing by L100's. I actually ordered the Murphy parts then cancelled the order. Why? the L100's are different. I have other sets of speakers that are very smooth detailed that I could listen to all day but they don't attack you like the L100's do. Put on some Led Zeppelin or the intro part of "Crazy on you" by heart, The sound impact actually raises the hairs on my arms, kind of an anxiousness. I also own a full Linn Aktive Isobarik system, Infinity Kappa 8, Ditton 66 powered by Bryston plus others so I have comparables. The initial WOW factor from the L100's just keeps me coming back for more. I can only take them for so long but that day or two or three is why it is well worth keeping them.

The only upgrade I will try is a recap with

some Ansar Supersound PP's, ​

I just did a set of L26 decade and was very impressed.

If you want a different sound I would suggest getting another set of speakers. There are a lot of quality vintage speakers for very good prices out there that are plenty smooth.

My 2 cents worth.

 

[Swerd]

I have thought long and hard about changing by L100's. I actually ordered the Murphy parts then cancelled the order. Why? the L100's are different. I have other sets of speakers that are very smooth detailed that I could listen to all day but they don't attack you like the L100's do. Put on some Led Zeppelin or the intro part of "Crazy on you" by heart, The sound impact actually raises the hairs on my arms, kind of an anxiousness. I also own a full Linn Aktive Isobarik system, Infinity Kappa 8, Ditton 66 powered by Bryston plus others so I have comparables. The initial WOW factor from the L100's just keeps me coming back for more. I can only take them for so long but that day or two or three is why it is well worth keeping them.

I cannot argue with your opinions. Yours are as good as mine, or most others.

But I can repeat what I said much earlier, how the new crossover does not loose that 'initial WOW factor' from the L100s. That is largely due to the 12" woofer. Even if its limited to 950 Hz and below, instead of playing to nearly 5 kHz, it still sounds great. The old frequency response curve goes from this:

To this:

Note how these 2 curves are essentially the same below 1 kHz. That's where nearly all the WOW factor is.

What makes the new crossover so successful is that it prevents the mid-range driver from producing the fatigue-inducing high frequency noise, peaking from 6 to 7 kHz. It also eliminates the comb filter unevenness and tones down the extreme brightness to the overall sound. All this occurs without loosing that WOW factor.

The only upgrade I will try is a recap with some Ansar Supersound PP's, I just did a set of L26 decade and was very impressed.

I can say with some confidence that simply replacing the existing caps on the L100 will not improve things. If I recall correctly, the capacitors in the old crossover did not look like non-polar electrolytic caps that are known to gradually fail with age. It's that old and inadequate crossover design of the L100 allows the mid-range driver to misbehave so much.

 

[PK Vintage]

Thanks for the reply. I will take this into consideration for sure. Noted that you say it will not take away that impact WOW! factor. Now you have me thinking again.

 

[thedrub]

First ... @Swerd ... When writing your original post, did you have any idea the conversation would continue for all these years? Must be relevant!

@lovinthehd , thanks for the link to the wires pages. I think I read those several years ago. As a result, I've always used lamp cord. Have tended towards 12 ga, just so I didn't need to even think about the length.

Yes, I ordered both the L88+ and the upgrade kit at the same time. The upgrade kit included the LE5-2 mid driver, and I'm guessing a new crossover and name plate. I truly don't remember replacing those pieces, so it may have just been installing the mid driver. The results were an L100, and saving a few bucks in my early 20s. $300 was much more significant at the time! See the photos of the ID plates.


Yes, with the woofer removed, access to the internals is easy.


The spring posts were contained in an aluminum box which was riveted to the hardboard on which the spring posts were mounted. Easy enough to drill out the aluminum pop rivets. Wondering why the heck they bothered with the aluminum box. Just for safety with the contained capacitor? Reduces the enclosure volume. And there is a socket on the box and a plug that mates to the socket. Just another opportunity for corrosion. I'm thinking I'll get rid of the alum box. Can you think of any down side to doing so?


The banana posts arrived, and are now installed. That small thing is a big improvement. Never liked those little spring loaded posts.

Also, I looked closely at the veneer. It really is in great shape. Only the "top" has some minor dings. I like your idea of steel wool. A much gentler treatment. Will only go beyond that if really needed.

Over the years, I've taken so much heat from other folks who thought the JBLs were way out of date and antiques. "Too big". Many times have had "wisdom" shared with me that I should replace them with a nice, small set of Bose something.

Thank you for the kind offer. I'll get moving on the crossovers in the next month or so, and will keep you posted on progress.

 

[Swerd]

Yes, with the woofer removed, access to the internals is easy.

The spring posts were contained in an aluminum box which was riveted to the hardboard on which the spring posts were mounted. Easy enough to drill out the aluminum pop rivets. Wondering why the heck they bothered with the aluminum box. Just for safety with the contained capacitor? Reduces the enclosure volume. And there is a socket on the box and a plug that mates to the socket. Just another opportunity for corrosion. I'm thinking I'll get rid of the alum box. Can you think of any down side to doing so?

In my old L100s (bought them in 1973) there was no aluminum box behind the spring terminal posts. Wires ran directly from the crossover board to the backs of the terminals. The terminals were mounted on a piece of Masonite board (similar looking to those in your photos) and the boards were fastened across an opening in the cabinet back.

Maybe the aluminum boxes were put in the L88s to make wiring the added mid range driver and it's capacitor easy for owners. Once you build the new crossovers, I don't see any reason why you should keep it. If its hard to remove, leave it in place and bypass it with the wires from the new crossover board.

 

[thedrub]

Good questions. Memory does not serve me well on what exactly I installed in 1975. Let's just say that certain activities during that era may have had an impact on my memories of that era. There was also a lot of loud music involved. ;-)

I believe it was just remove the grill, connect the mid wires, and attach with 4 screws. I certainly didn't route the wires inside the enclosure, and use orange glue where the wires penetrate the fiber tube that encloses the mid.

Thanks for the info on the lack of aluminum box. Seems prudent to eliminate the enclosing aluminum box, socket, and plug, in the next steps. I'd guess JBL folks added them when they thought consumers may have their hands in the cabinet with charged capacitors. <shrugs shoulders>. Very easy to remove the spring post box. It was attached with aluminum pop rivets.

BTW, the existing crossover also appears to be enclosed in an aluminum box, higher in the cabinet, above the bass driver. I didn't get a good look or a photo, but felt a cool aluminum box of similar characteristics. Larger than the one containing the spring clips. Maybe 2 to 3 times the volume. More photos when I yank it outta there to install the new crossover. Will contribute a little more volume to the cabinet.

Thanks again for the info and the ideas, design, thoughts, inspiration, silly musings ......

 

[3db]

Swerd, What do you think contributed to the East Coast verses West Coast sound back then? Was it because the computer modeling tools weren't readily available or was it purposely built in? I ask this because today's manufacturers are trying to achieve as neutral response as possible ( ie flat FR curve over the widest possible bandwidth). Has the East verses the West sound died off or is this still prevalent?

 

[Swerd]

Swerd, What do you think contributed to the East Coast verses West Coast sound back then? Was it because the computer modeling tools weren't readily available or was it purposely built in? I ask this because today's manufacturers are trying to achieve as neutral response as possible ( ie flat FR curve over the widest possible bandwidth). Has the East verses the West sound died off or is this still prevalent?

Back in the 1960s and 70s, the East Coast (AR and KLH speakers) vs. West Coast (JBL) sound was real and I believe intentional.

The AR & KLH acoustic suspension woofers were a new concept in the late 1950s and early 60s. For the most part, they succeeded in achieving a highly damped bass sound in a rather small cabinet. They were power hungry (a 40 or 50 watt amp was very expensive back then) but they worked. Their bass was potent and had a dry restrained sound. Their mid range and tweeters were hit or miss. Crossover design was more engineer's intuition, a seat-of-the-pants approach, than anything else. Some designs worked better than others. The AR-2a was a smaller less expensive and better sounding 3-way speaker than the AR-3.

The JBL approach, at least in the L-100, was to achieve a big bass response in what was then considered a small cabinet. They used a 12" woofer in a small (too small) ported cabinet. It's bass was resonant and exaggerated, a high Qts design. JBL clearly knew better. They had used that same woofer in a much larger sealed cabinet, which worked better. The mid-range driver was loud but peaky, full of ups and downs. The cone tweeter wasn't bad at all. They deliberately arranged the drivers in an odd fashion so the speaker could be used sideways or upright without sounding much different. All that was intentional. There were, no doubt, clever speaker designer who could achieve these goals, but it took a lot of trial & error. Computer aided design tools, as we know them, didn't exist. People didn't run through the Fourrier transform math by hand if they could avoid it and only if someone paid for the effort. And finally, JBL made a big marketing effort to sell these speakers to younger buyers. They were advertised as sounding different, more exciting, than the dry restrained East Coast speakers. I believe it was JBLs advertising language that coined the phrase West Coast sound vs. East Coast sound. Using the term "East Coast Sound" avoided naming their AR or KLH competitors.

Remember that the math models based on T/S parameters that could predict bass response as cabinet dimensions were varied had not yet been published. Speaker designers of the day probably understood some of that, but it hadn't yet become a widely used tool.

And computer modeling tools for crossover design were not available at all. Hence the "minimal" crossover networks. Keep it simple and cheap. JBL, AR and KLH crossovers all shared that minimalist feature.

Your questions are very good. I didn't address them all, but I hope this was a good start.

 

[Kapitan_Nemo]

Hello. I am new here. If anyone is interested, I will write about my impressions, because I do not know if the topic has died.

 

[everettT]

Hello. I am new here. If anyone is interested, I will write about my impressions, because I do not know if the topic has died.

In regards to the mod or the speakers? Either way thanks for posting.

 

[Kapitan_Nemo]

Some time ago I bought a jbl l100 century. I decided to improve the crossover according to Murphy's scheme. As I live in Europe, I used capacitors available at us such as mundorf Evo Oil, MKP, etc. I have slightly modified the design by adding battery power to each of the speakers. For high 1x 9V, medium and low 6x9V. From the very beginning of listening on the new crossover I was disturbed by too big bass. So I choked the bass refkex which gave very good results. Thank you, Swerd for inspiration. It was really worth it.

 

[highfigh]

Some time ago I bought a jbl l100 century. I decided to improve the crossover according to Murphy's scheme. As I live in Europe, I used capacitors available at us such as mundorf Evo Oil, MKP, etc. I have slightly modified the design by adding battery power to each of the speakers. For high 1x 9V, medium and low 6x9V. From the very beginning of listening on the new crossover I was disturbed by too big bass. So I choked the bass refkex which gave very good results. Thank you, Swerd for inspiration. It was really worth it.
View attachment 28466
View attachment 28467

What the F? Batteries? Why?

 

[Kapitan_Nemo]

What the F? Batteries? Why?

It would take a long time to write about it. I read once on one of the forums about powering the speakers with batteries. JBL has successfully applied this patent in some high models.
The JBL "charge-coupled circuit" replaces a single cap with a pair of series-connected caps of twice the value of the original single cap, the center-point between the cap-pair is attached to a battery in series with a 100K to 1M resistor, and the other side of the battery is attached to circuit ground. This polarizes both caps to the DC voltage of the battery, so the caps never go through zero-crossing. 9V is a better choice than 1.5V batteries, since loudspeaker-level signals fairly frequency pass through the 1.5V threshold, but 9V is getting pretty loud.
Building a new crossover I decided to try this patent. The effect exceeded my expectations.

 

[Swerd]

Kapitan_Nemo, thanks for the photos of your work. Some of those capacitors are very large, larger than the inductor coils! And 13 batteries per speaker. That's one big crossover board.

It would take a long time to write about it. I read once on one of the forums about powering the speakers with batteries. JBL has successfully applied this patent in some high models.
The JBL "charge-coupled circuit" replaces a single cap with a pair of series-connected caps of twice the value of the original single cap, the center-point between the cap-pair is attached to a battery in series with a 100K to 1M resistor, and the other side of the battery is attached to circuit ground. This polarizes both caps to the DC voltage of the battery, so the caps never go through zero-crossing. 9V is a better choice than 1.5V batteries, since loudspeaker-level signals fairly frequency pass through the 1.5V threshold, but 9V is getting pretty loud.

I've seen this mentioned before, but I've never understood the reasons behind the design. Do you have a link that would explain this?

The new Murphy crossover requires 7 capacitors. The charge coupled modification can be very expensive because it requires twice as many capacitors all of which are double the origianl capacity.

How long do you expect those 9 volt batteries to last?

JBL did this years ago in some of its more expensive models, but I don't believe this charge coupled type of circuit is used in any new speakers. No other speaker maker, to my knowledge, has used this design.

Building a new crossover I decided to try this patent. The effect exceeded my expectations.

The new Murphy crossover design, alone, can account for a much improved sound quality. Were you able to compare two L100s both with the new Murphy crossover, but one with charge coupled circuit, and the other without it?

 

[Kapitan_Nemo]

Kapitan_Nemo, thanks for the photos of your work. Some of those capacitors are very large, larger than the inductor coils! And 13 batteries per speaker. That's one big crossover board.

To tell you the truth, I did not do it alone. I just follow news, interesting projects on the Internet and if I'm interested in something, I ask my friend to do the Task. This crossover was also done by my friend for me.

I've seen this mentioned before, but I've never understood the reasons behind the design. Do you have a link that would explain this?

I will try to find links for you in a few days as I will have more time.

The new Murphy crossover requires 7 capacitors. The charge coupled modification can be very expensive because it requires twice as many capacitors all of which are double the origianl capacity.

Capacitors are added only when there is one capacitor, because then if we would like to give a constant voltage it would go to the loudspeaker or amplifier, then we add condensers so as to maintain the required capacitance and the voltage between them will not go in any direction because the capacitor does not release voltage solid. There we have a 3rd order filter where there is a capacitor, coil and capacitor, so we have a capacitor on both sides that will block the DC voltage, and because the battery for the alternating current in the crossover is a short circuit, then supplying the battery to the coil between the capacitor gives us the DC bias effect condensers and the battery itself is a short circuit for alternating current, hence you can do it.
Therefore, additional, double-value capacitors were only added for the bass speaker and additionally a transformer coil.

The new Murphy crossover design, alone, can account for a much improved sound quality. Were you able to compare two L100s both with the new Murphy crossover, but one with charge coupled circuit, and the other without it?

No, I did not compare Murphy crossover without an extra battery. I was just fantasized and decided to check how it would work. So it is difficult for me to say what are the advantages of this solution.

I can only say that I have never heard such a resolving bass.