The Vintage JBL West Coast Sound becomes the…

[Swerd]

I'm going to PM you asap if that is OK?

MixingMusic

No problem. But if all you want is the parts list, I attached them in an earlier post.

 

[AllenW]

Just happen to hit this site looking for crossovers for my L100 clones.

I'm currently running a tri amped system out in my woodshop/garage and need to get one of the Crowns looked at, also I'm also trying to build a better cabinet for them while finishing the wife kitchen cabinets.

So I need to dismantle the system and figure it'll take a couple months to finally get everything back together again, so I thought I could build a set of crossover for my DIY speakers.
Then I could run one amp/receiver for the time being.
Maybe keep it that way too.

I built these with the L-100 sound in mind except I used 15" woofers instead of 12".

I'm wondering if you think your crossovers would work in my speakers?
While I realize crossover design is such that it'd be just a educated guess I'll take that guess.
The L100's I had years ago also had their crossovers changed by the previous owner and I'm hoping there's enough similarity that your's may work in my speakers.

If you can help it'd be most apreceated, if not, it was a great post anyway..

Brought back some memories, as I had 4 of them back in the 70's.

fwiw I used,

Peerless 850488 HDS 5.25" Mid/Woofer

Morel 1.125" MDT-30 Tweeters.

DAYTON ST385-8 15" Series II Woofer


Once again, thanks.

Al

 

[Swerd]

I'm wondering if you think your crossovers would work in my speakers? While I realize crossover design is such that it'd be just a educated guess I'll take that guess.

The L100's I had years ago also had their crossovers changed by the previous owner and I'm hoping there's enough similarity that your's may work in my speakers.

fwiw I used,

Peerless 850488 HDS 5.25" Mid/Woofer

Morel 1.125" MDT-30 Tweeter

DAYTON ST385-8 15" Series II Woofer

I doubt if the new L100 crossovers I posted in this thread would work well with what you have. Although those 3 drivers of yours may make a very decent 3-way speaker, the crossover I posted was designed specifically for those JBL drivers mounted in the L100A cabinet. The crossover points are 950 and 5000 Hz. What are the crossover points in your tri-amped system? I doubt if my JBL drivers share impedance characteristics, sensitivity or frequency response with your drivers. So using this crossover would lead to numerous problems with your 3-way.

The Peerless mid and Morel tweeter you have are actually much better than those in the L100. I’ve always liked that MDT-30 tweeter. It is a very good modern dome design and easily outperforms the larger cone tweeter in the L100. The Morel can go a lot lower than 5000 Hz, maybe even lower than 2000 Hz.

I couldn't find any info on the Peerless 850488 mid woofer, but I expect it is very different from the JBL LE5-2 midrange, which was always a strange one. It was a true midrange in the sense that it couldn't go as low as a typical 5" woofer but it could go much higher. Its main problem was that it wasn't very smooth and required a lot of equalization in the crossover. I'm pretty sure that the midrange part of my crossover would be unsuitable for your Peerless mid. As a guess, the Peerless probably can go low enough to blend with that Dayton 15" woofer and high enough to blend well with the Morel tweeter. But the bandpass filter designed for the JBL LE5-2 midrange would stomp all over that.

Your 15" woofer is also much different than the JBL 123A 12". It can’t go much above 300 Hz without breaking up. My crossover point from the woofer to the midrange is at about 950 Hz. That would be real trouble with your woofer.

 

[highfigh]

Here's the Tymphany data sheet for the 850488:
http://www.tymphany.com/850488

There's no way that 15" should run all the way up to 950 and personally, I think the L100 should have been crossed over well below that, too. The Peerless will do fine crossed over at about 200Hz although the data sheets don't indicate power handling. The response curve for the Dayton shows that 200Hz would be a decent crossover point and even then, it will need some smoothing.

With a well designed crossover, these should sound pretty good.

 

[Swerd]

Here's the Tymphany data sheet for the 850488:
http://www.tymphany.com/850488

There's no way that 15" should run all the way up to 950 and personally, I think the L100 should have been crossed over well below that, too. The Peerless will do fine crossed over at about 200Hz although the data sheets don't indicate power handling. The response curve for the Dayton shows that 200Hz would be a decent crossover point and even then, it will need some smoothing.

With a well designed crossover, these should sound pretty good.

Thanks for that link. The Peerless should make a good midrange between 200 and 2000 Hz, but do not cross it over at 950 and 5000 Hz!

Compare it to the unfiltered freq response of the JBL LE5-2 midrange. Smooth is not a word I would use for that. Because the JBL 12" woofer was capable of smooth response (at least on axis) in that frequency range, a crossover at ~950 was a way to eliminate part of the midrange's roller-coaster frequency response. It also distorted a lot more when you got well below 1 kHz.

 

[highfigh]

Here are two slightly different parts lists. Only two items, capacitors C1021 (40 µF) and C2081 (30 µF), are different on these lists. They are highlighted in yellow. As of August 2006, their total prices differed by about $32 US. Parts List 1 uses less expensive bi-polar electrolytic capacitors, and Parts List 2 uses somewhat more expensive metallized polypropylene (MPP) capacitors. List 1 uses Bennic (Madisound) bipolar electrolytic caps for C1021 and C2081. List 2 uses Dayton (Parts Express) metallized polypropylene (MPP) caps for C1021 and C2081.

When I built mine, I splurged and used all MPP capacitors from List 2. Crossovers built with parts from either list should sound the same, so take your pick. Note that the large value MPP capacitors are larger in size than the electrolytic ones, and that is reflected in my crossover layout diagram.

Neither of these types of capacitors is as expensive as exotic or boutique capacitors. The house brands from Parts Express (Dayton) and Madisound (Bennic) are both very reasonably priced and very good performers.

It has now been nearly a year since building these new crossovers, and I am still quite happy with them. Now that most of the frequency range is smooth, the exaggerated bass response of the L-100 became a more prominent problem. The L-100 cabinet is about 1.6 ft³ and has a port vent. With the 123A 12" woofer, this causes a large peak, roughly 5 dB, in the 50-80 Hz range, that overemphasizes the bass. The best cabinet for these 12" woofers would be a 3.0-3.3 ft³ sealed box, which would require a completely new cabinet.

I found a much easier way to at least partially fix this problem. I sealed the port opening with a 3" Plumber’s Test Plug. I can find them at my local Home Depot or Loews’ in the plumbing pipe department for less that $4. I think the photo shows a smaller plug smaller than 3", but they are all similar. They consist of a rubber ring held between two metal plates, with a nut and bolt. Tightening the wingnut presses the two plates closer and expands the rubber ring. Plumbers use these to temporarily seal drain pipes so they can test for leaks.

To seal my L-100s, I filed down the smaller of the two plates until it would fit into the roughly 2⅞" diameter port. Then I turned the wingnut until it the rubber ring fit tight. I think it made a noticeable improvement, but I haven’t measured this to be sure.

If you have any gullible audiophile friends, try slightly turning the wingnut while playing some music and ask if they hear the difference. I find that about half agree with me and say it makes a big improvement!

Marantz had speakers in the late '70s or early '80s with a tapped centerpiece that was part of the cone assembly and they came with a selection of weights that were to be used, or not and by using one or another, the resonance frequency and Q could be varied, depending on the taste or room. Being Marantz, they were OK but it was pretty unique.

 

[highfigh]

Thanks for that link. The Peerless should make a good midrange between 200 and 2000 Hz, but do not cross it over at 950 and 5000 Hz!

Compare it to the unfiltered freq response of the JBL LE5-2 midrange. Smooth is not a word I would use for that. Because the JBL 12" woofer was capable of smooth response (at least on axis) in that frequency range, a crossover at ~950 was a way to eliminate part of the midrange's roller-coaster frequency response. It also distorted a lot more when you got well below 1 kHz.

200Hz and 2500-3000Hz are good numbers for the band-pass on that Peerless- the response isn't as smooth above that and it may be subject to beaming in the 5KHz range. I was using Peerless 833599 for mid-bass and just replaced them with 830874 form the HDS PPB line.

 

[AllenW]

Thanks guys, I had major doubts about the crossovers working, but I had to start someplace.

I'll have to check on how the crossover is set up to what numbers I'm using now.

I seem to remember back in the 60's or early 70's somebody had a basic formula for building crossovers.
Considering I doubt I have the time or patience for trying to learn the art of designing these things, I was hoping for a simpler method to at least get close.

Or a bit of help.

Thanks all.

Al

 

[highfigh]

Thanks guys, I had major doubts about the crossovers working, but I had to start someplace.

I'll have to check on how the crossover is set up to what numbers I'm using now.

I seem to remember back in the 60's or early 70's somebody had a basic formula for building crossovers.
Considering I doubt I have the time or patience for trying to learn the art of designing these things, I was hoping for a simpler method to at least get close.

Or a bit of help.

Thanks all.

Al

The simple crossover formula is C=1/((2 x Pi)( FR)), where C is capacitance, F is -3dB frequency and R is the resistance, but since you need a more elaborate crossover, that's not what you need.

Look here for the section on passive crossovers:
http://www.the12volt.com/info/diagrams.asp#menu

OTOH, you could go to this site and have a conniption:
http://www.sengpielaudio.com/Calculations03.htm

 

[AllenW]

The simple crossover formula is C=1/((2 x Pi)( FR)), where C is capacitance, F is -3dB frequency and R is the resistance, but since you need a more elaborate crossover, that's not what you need.

Look here for the section on passive crossovers:

OTOH, you could go to this site and have a conniption:


..
Thanks, your correct, the second web site is a bit much for the old guy here...

I'll play with the first one, thanks.
Not sure if I want first, second or third order, guessing first ??

Al

 

[AllenW]

"""""
I doubt if the new L100 crossovers I posted in this thread would work well with what you have. Although those 3 drivers of yours may make a very decent 3-way speaker, the crossover I posted was designed specifically for those JBL drivers mounted in the L100A cabinet. The crossover points are 950 and 5000 Hz. What are the crossover points in your tri-amped system? I doubt if my JBL drivers share impedance characteristics, sensitivity or frequency response with your drivers. So using this crossover would lead to numerous problems with your 3-way.
""""


Sorry for the delay, I work in HVAC and live in Minn, been a bit hetic here lately.

I'm crossing the system at 400 and 3000Hz, been playing with the settings a bit to get the best sound for my lacking ears, but at them setting I get a fairly flat curve considering they are in a garage with poor acoustics.

I'll take your advise and not use the crossover you have, might just be better off leaving it tri amped.
But it might be interesting to see how they sounded.

Once again, thanks all.

Al

 

[bwilkinson]

Another Resurrection

Sorry to resurrect this old thread yet again - especially as my first post. However, it fits exactly in the realm of what I am working on.

I just got my hands on a pair of immaculate L100A's, for a steal. Cabinet has a few scratches, but nothing major. Drivers are perfect. L-pads, are - well - rough, at best. I played them, and either the caps are shot, or the description of the "peaky" sound at 6k and the boost at 80Hz has been terribly under-exaggerated. Then again, with the L-pads in the condition they are, it's probable that they are just allowing full signal to the speakers, and cutting nothing.

At any rate, I plan on using these as a second opinion speaker for my yet planned control room in a home studio, and am seriously considering the crossover design that Swerd has described. I do have a few questions with regards to it.

(1) The crossover schematic shows all positive outputs of the crossover connecting to the positive side of each speaker. Because the 123 woofer is actually wired backward from what most manufacturers do, then is this saying that in a traditional woofer wiring the signal is actually out of phase?

(2) I have never built a crossover before. I've done other simple DIY electronic work, just never anything involving an inductor. Given the inductance of these, how close together can these inductors get, given the orientation that was shown? I would like to assemble them on a PCB, with the resistors and capacitors on one side of the board, and the inductors on the other side. Thus far, I have been able to package the crossover on a 6"x8" board - I rotated the 0.15mH crossover clockwise 45 degrees from the shown orientation, and the 0.68mH inductor counterclockwise by 45 degrees. Is this getting too close to cause inductive coupling?

(3) I plan on driving this with a studio reference amplifier (Behringer A, ART SLA, Samson Servo, or Alesis RA series). Will the "lack" of color added by the amp cause me issues?

Please let me know your thoughts.

Thanks!

 

[Swerd]

I just got my hands on a pair of immaculate L100A's, for a steal. Cabinet has a few scratches, but nothing major. Drivers are perfect. L-pads, are - well - rough, at best. I played them, and either the caps are shot, or the description of the "peaky" sound at 6k and the boost at 80Hz has been terribly under-exaggerated. Then again, with the L-pads in the condition they are, it's probable that they are just allowing full signal to the speakers, and cutting nothing.

Thanks for you interest. I'm always glad to answer questions like yours. I doubt the caps are bad, but I'm willing to bet the L-pads are hopelessly oxidized.

(1) The crossover schematic shows all positive outputs of the crossover connecting to the positive side of each speaker. Because the 123 woofer is actually wired backward from what most manufacturers do, then is this saying that in a traditional woofer wiring the signal is actually out of phase?

Some of those JBL woofers were wired opposite from what is considered the industry standard, and others were done the standard way. You have to find out what polarity yours are. Get an AA 1.5 volt battery, and tape on two pieces of wire, one on each end of the battery. Touch the plus wire to one terminal of the woofer, and the minus wire to the other. The woofer cone will pop forward if you have touched the plus end of the battery to the plus terminal of the woofer. The woofer pops back if you have it reversed. You can do the same with the mid and tweeter without harming them. The important thing is to wire all 3 drivers in the same polarity.

(2) I have never built a crossover before. I've done other simple DIY electronic work, just never anything involving an inductor. Given the inductance of these, how close together can these inductors get, given the orientation that was shown? I would like to assemble them on a PCB, with the resistors and capacitors on one side of the board, and the inductors on the other side. Thus far, I have been able to package the crossover on a 6"x8" board - I rotated the 0.15mH crossover clockwise 45 degrees from the shown orientation, and the 0.68mH inductor counterclockwise by 45 degrees. Is this getting too close to cause inductive coupling?

I showed a diagram of my crossover. I used a 7"×10" piece of pegboard, and my diagram was made by tracing each piece. So it is roughly to scale.
I followed a simple guide to placing inductor coils here. Scroll down to the lower part of this page and see the diagram for placing coils. Remember that 10 cm is about 4 inches.

(3) I plan on driving this with a studio reference amplifier (Behringer A, ART SLA, Samson Servo, or Alesis RA series). Will the "lack" of color added by the amp cause me issues?

I doubt you will have any problems with those amps.

Good luck with your project .

 

[bwilkinson]

I'm beginning to understand. The inductor layout you used was not just to fit all the components on one side, but primarily to minimize the interactions of the magnetic fields. Thanks for that information!

I'm looking forward to starting on this - hopefully I can get moving in the next couple of weeks. In the mean time, coats of linseed oil on the cabinet over and over to bring the walnut back to beauty!

I can't bring myself to purchase the replacement quadrex - I guess being born in the 70's is too late to truly appreciate the style of the era. I'll build a cloth insert and velcro it into place where the quadrex was designed to sit - so it can be changed back in case I ever decide to feel nostalgic. I hate the thought of doing anything irreversible to the speakers.

Thanks again for the information.

 

[Swerd]

I'm beginning to understand. The inductor layout you used was not just to fit all the components on one side, but primarily to minimize the interactions of the magnetic fields. Thanks for that information!

I'm looking forward to starting on this - hopefully I can get moving in the next couple of weeks. In the mean time, coats of linseed oil on the cabinet over and over to bring the walnut back to beauty!

I can't bring myself to purchase the replacement quadrex - I guess being born in the 70's is too late to truly appreciate the style of the era. I'll build a cloth insert and velcro it into place where the quadrex was designed to sit - so it can be changed back in case I ever decide to feel nostalgic. I hate the thought of doing anything irreversible to the speakers.

Thanks again for the information.

I think you got it now. Only the inductors generate a magnetic field. The caps and resistors can go anywhere without interacting with other parts.

Have you gotten the crossover parts yet? The resistors are all the same small size, the caps vary in size but are not heavy, but some of those inductors are large and heavy. My pegboard was about ¼" thick. I don't know how thick and strong your PC board is, but the weight of the larger inductors parts might be too much for it. You'll know when you get the parts.

 

[bwilkinson]

I haven't purchased the parts yet, and after my conversation with you (and some more looking around) I may change directions a bit.

I drew everything up on CAD to try to fit it initially. The mass of the inductors I was less concerned about, because I could have placed standoffs to reinforce the structure.

Now, I may just grab a piece of MDF or black walnut (rather than pegboard, I have these sitting around), and mount it to the inside back of the cabinet - in place of the current piece holding those silly push connectors. Then I can replace the push connectors with binding posts, and keep the old mounting block intact - again, in case someone wants to put it back to true "original" condition.

Speaking of that, rather than using zip ties to hold things in place, would a silicone sealant or something along that line work well to hold the heavy components in place? I know I can screw through the 2.5mH inductor's core to mount it, and I guess I could put something together to mount through the center of the air core inductors - but the thought of bringing a metallic screw anywhere near the magnetic field of an inductor just sounds like it is asking for trouble!

You may have said this in other threads, but I might have missed it. What did you use (or did you) to replace the original baffle insulation?

 

[Swerd]

Now, I may just grab a piece of MDF or black walnut (rather than pegboard, I have these sitting around), and mount it to the inside back of the cabinet - in place of the current piece holding those silly push connectors. Then I can replace the push connectors with binding posts, and keep the old mounting block intact - again, in case someone wants to put it back to true "original" condition.

Yes, definitely replace those flimsy push connectors on the back of the cabinet with some sturdier binding posts.

Speaking of that, rather than using zip ties to hold things in place, would a silicone sealant or something along that line work well to hold the heavy components in place? I know I can screw through the 2.5mH inductor's core to mount it, and I guess I could put something together to mount through the center of the air core inductors - but the thought of bringing a metallic screw anywhere near the magnetic field of an inductor just sounds like it is asking for trouble!

I don't think silicone sealant would be strong enough for the inductors. On some earlier DIY builds, I used to use hot-melt glue, but it was also not strong enough. I have heard of people who use epoxy compounds, but I prefer to use nylon zip ties. No mess, no waiting for the glue to set, and if you make a mistake, they are reversible. Zip ties do require pegboard or any thin board like masonite that lets you drill holes to pass the zip ties through.

The holes in the iron bar of the 2.5 mH inductor do allow screws, but use only brass, aluminum, or non-magnetic types of stainless steel. Two 8" long zip ties worked well on that piece for me.

You may have said this in other threads, but I might have missed it. What did you use (or did you) to replace the original baffle insulation?

My L100s had a roughly 1" thick layer of glassfiber on all inside walls of the cabinet. I left that in place. When I mounted the crossover board on the bottom of the cabinet, I used 1" long stand offs under the board to keep it from compressing the glassfiber.

 

[bwilkinson]

I don't think silicone sealant would be strong enough for the inductors. On some earlier DIY builds, I used to use hot-melt glue, but it was also not strong enough. I have heard of people who use epoxy compounds, but I prefer to use nylon zip ties. No mess, no waiting for the glue to set, and if you make a mistake, they are reversible. Zip ties do require pegboard or any thin board like masonite that lets you drill holes to pass the zip ties through.

You're killing me here! I'm just one of those perfectionistic types, and want my projects to look as tidy as possible. Looks like I'm going to have to go with either masonite or the like, drill holes to fit zip ties, and use silicone to keep from any vibrations. I know it's overkill, but it looks pretty.

At any rate, thank you for all the information. I really appreciate it.

 

[bwilkinson]

Just bought the components for the crossover! The cost of copper has changed the prices for the inductors just a shade, though. I feel like a kid waiting for Christmas...

 

[bwilkinson]

One more question

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)?

Or is this a major no-no in speaker building?