L300/Summit Recap thoughts

[T.Rex]

Hi all,

I have a lovely set of Summits and was wondering about recap longevity. I know that this is going to vary, but want to keep my options open for the future. My Summits have worked flawlessly since I purchased back in 2007 as the 2nd owner........no cracks, pops.....nothing. Even the L-Pads, after treating with a little deoxit work like new. I also know that capacitors don't last forever. These are pushing 40-years old now and probably only a matter of time. I play every day, never really pushing them in a controlled environment.

How hard to disassemble crossover and remove board?...........Should I have the caps replaced on the original board or will a new board built for the job be the better route?.....Does anyone have any experience with the Pass-Nelson Board that is listed on Ebay/Amazon?.....will it directly fit into speaker or are their mods needed? (Pic Below)......Does anyone have any experience with the sound quality with this change?

I don't want to have to haul these heavy behemoths to a repair center.........how much is involved with the upgrade and could an electrician possibly be hired to replace for me?

I know I'm asking a lot of questions and seems funny since these speakers work fantastic as I write this.

Thanks,

Tom

Product description

Crossover for JBL L300 summit century 3 way speaker system! ( pair)
 
Welcome back to the sound of the century! We have decided to put together a " top quality crossover that will match the specifications of the JBL L300 ( modified version) , since it has a better frequency response and sound.. this crossover will work and sound just like back on the 70"s, but just built with new top quality components this days. sweet sound on the highs, clean and projected vocals on the midrange and the great boom, tight punchy bass on the lows. heavy duty 250 volt capacitors, high temp inductors and heavy duty resistors that will last for a long period of time. this crossover will have the feature for you to ad the L-Pads on the tweeter and the Mid, just like the original! specs: • 3 way crossover network system
 • crossover frequencies 1.2khz & 8khz 
 • 500 watts RMS / 1000 watts peak 12db/oct
 • to use with 8 ohms drivers
 • built and based on the " modified version of the "JBL L 300 "
 • heavy duty Bugle "J" 250 volt Metallized Polyester Film capacitors
 • orifices built on board for tweeter&mid for L Pad easy installation 
 • dimensions 4 3/4" X 6 3/4
.

[macaroonie]

Is your crossover is the same as N333 , essentially a steel box with all the components inside and a wiring loom going to the drivers ? If so you will find that the bass section caps and chokes are potted in wax in the bottom of the box. It's quite the process to extricate the relevant parts as you need to melt the potting and clear it out .

I did it with 4315 networks and it was a pita. You will need to be very meticulous
as to what wire goes where. Take loads of pics as you go and refer to the schematic.

It can be done , but take care.

BTW , if you have a woodburner with it on at a lazy heat you can heat the whole caboodle till the wax melts.

[T.Rex]

[QUOTE=macaroonie;415616]Is your crossover is the same as N333 , essentially a steel box with all the components inside and a wiring loom going to the drivers ?


Yep....Steel Box with wiring loom............Can I remove the whole box and remove from the cabinet and work on the crossover or is it riveted or non-removable?

thanks for your help,

Tom

[macaroonie]

[QUOTE=T.Rex;415620]

Is your crossover is the same as N333 , essentially a steel box with all the components inside and a wiring loom going to the drivers ?


Yep....Steel Box with wiring loom............Can I remove the whole box and remove from the cabinet and work on the crossover or is it riveted or non-removable?

thanks for your help,

Tom

Yeah it will disconnect and de mount. Screws probably. You will see a perf top plate on the box , thats when you need to start taking notes. Depending on the age the components may not have values printed on them but they will have part No's. You then need to refer to find that part in the schematic.

[T.Rex]

MCM......you should get a medal or something for that work!.........Unbelievable workmanship.

Macaroonie, Ian and MCM ....thanks for the help.

regards,

Tom

[MCM_Fan]

Tom,

Unlike amps/receivers, etc. with active electronics, capacitors in speaker crossover networks rarely fail catastrophically. They typically drift over time. How much and how fast the drift depends on the quality of the original parts, operating and environmental conditions.

So, don't expect any "a ha" moment when your speakers suddenly stop working or start sounding noticeably worse than they did the day before. The caps typically drift so slowly, you don't even notice it, until you do a recap and things suddenly sound better.

The caps in your L300 Summits are now over 40 years old. The caps JBL used were high quality for the time, but are nothing special by today's standards. I've recapped many smaller JBLs, and to my ears, they always sounded better after the recap. In the case of the smaller speakers, the crossovers are simpler, replacement parts are cheaper and the labor involved is minimal (compared to building a pair of L300 crossovers from scratch). So, I generally do them as a matter of course when I have the woofers pulled for replacing the deteriorated foam surrounds. Gives me something to do while the glue dries and I have easy access to the crossovers.

Unfortunately, with the L300 Crossovers potted in wax, a simple recap becomes more time consuming. You have multiple options:

• Just leave them as they are and be content that even if the caps have drifted the speakers still sound good to your ears.

• Replace the easily accessible caps - fortunately, the easily accessible caps are the ones in the tweeter and midrange circuits. These are more crucial to sound quality than the woofer shunt caps that are potted in the wax. This would be quick easy and relatively inexpensive. Low hanging fruit.

• Melt the wax and do a complete rebuild of the existing crossovers.

• Make some new crossover based on the original design.

• Make some new crossovers based on the Nelson Pass design. If you're contemplating going this route, I suggest you read the PDF in the link I provided in my first reply. Nelson Pass is a well respected audio engineer. He knows his stuff. Even if you don't end up going this route, as an L300 owner, it's worth reading his report just to fully understand your options.

As you move down this list, the cost of parts and time/effort involved increases.

[macaroonie]

Tom,

Unlike amps/receivers, etc. with active electronics, capacitors in speaker crossover networks rarely fail catastrophically. They typically drift over time. How much and how fast the drift depends on the quality of the original parts, operating and environmental conditions.

So, don't expect any "a ha" moment when your speakers suddenly stop working or start sounding noticeably worse than they did the day before. The caps typically drift so slowly, you don't even notice it, until you do a recap and things suddenly sound better.

The caps in your L300 Summits are now over 40 years old. The caps JBL used were high quality for the time, but are nothing special by today's standards. I've recapped many smaller JBLs, and to my ears, they always sounded better after the recap. In the case of the smaller speakers, the crossovers are simpler, replacement parts are cheaper and the labor involved is minimal (compared to building a pair of L300 crossovers from scratch). So, I generally do them as a matter of course when I have the woofers pulled for replacing the deteriorated foam surrounds. Gives me something to do while the glue dries and I have easy access to the crossovers.

Unfortunately, with the L300 Crossovers potted in wax, a simple recap becomes more time consuming. You have multiple options:

• Just leave them as they are and be content that even if the caps have drifted the speakers still sound good to your ears.

• Replace the easily accessible caps - fortunately, the easily accessible caps are the ones in the tweeter and midrange circuits. These are more crucial to sound quality than the woofer shunt caps that are potted in the wax. This would be quick easy and relatively inexpensive. Low hanging fruit.

• Melt the wax and do a complete rebuild of the existing crossovers.

• Make some new crossover based on the original design.

• Make some new crossovers based on the Nelson Pass design. If you're contemplating going this route, I suggest you read the PDF in the link I provided in my first reply. Nelson Pass is a well respected audio engineer. He knows his stuff. Even if you don't end up going this route, as an L300 owner, it's worth reading his report just to fully understand your options.

As you move down this list, the cost of parts and time/effort involved increases.

OR ......

Buy 3 x ML 11 in good nick and a DBX / JBL Urei 260 crossover and DSP the living crap out of them.

Well , perhaps a ML9 for the Bass

oops thats only 5K £££$$$eee

[T.Rex]

Read below...........I'm not going to fix what ain't broke.......just don't want to wait to the inevitable happens and than not have any idea what to do.

If, and when the caps go, I'll disconnect everything and have the original crossover box replaced with high end, reliable parts...that should last until I die I hope.

I think Ian is right.........am running through a Levinson 38S Preamp and Mcintosh MC 252 Power Amp........don't want to mess with the current synergy that might be lost with an aftermarket Crossover.

thanks,

Tom

[T.Rex]

Thanks.....When it comes time, or when I'm in a adventurous mood I will remove and have them rebuilt. I'm guessing that there are no spade connectors...just wires? So I'll have to cut, label and splice when I re-install?

thanks,

Tom

[macaroonie]

You can de mount the whole x/o complete with driver wiring. Once you start to take the
x/o to bits ,after you remove the perf cover you WILL have to start de soldering to get the tag board out of the way and then you are in to the potted components.

At each solder lug / tag you must ID the wires , some come from down below in the wax.

[T.Rex]

Hi MCM........

The Summits still sound good to my ears, but your right....I'm sure they have drifted a tad compared to new. I'll probably, in the next few years, remove and have the whole damn crossover re-done. I don't want to replace part of it now and part later. These speakers produce some of the most realistic vocals that I have ever heard and the drivers are built like a tank. I purchased them in 2007 after looking for years for a "like new Set" and found them with an additional set of unused Camel grill covers to boot. I wipe them down with Howards Feed-N-Wax a few times a year and the Black Walnut still looks almost new. Only modification was to install high-quality banana plug jacks. They are consecutively numbered as well........

thanks a million,

Tom

[MCM_Fan]

Hi MCM........

The Summits still sound good to my ears, but your right....I'm sure they have drifted a tad compared to new. I'll probably, in the next few years, remove and have the whole damn crossover re-done. I don't want to replace part of it now and part later. These speakers produce some of the most realistic vocals that I have ever heard and the drivers are built like a tank. I purchased them in 2007 after looking for years for a "like new Set" and found them with an additional set of unused Camel grill covers to boot. I wipe them down with Howards Feed-N-Wax a few times a year and the Black Walnut still looks almost new. Only modification was to install high-quality banana plug jacks. They are consecutively numbered as well........

thanks a million,

Tom

Tom,

Wow, those really are beautiful. JBL really made some great cabinets back in the day. Of course back then everything from the drivers to the boxes were top notch.

I've also installed new binding posts on every pair of vintage JBLs I've owned. If there was a weak spot, that was it. Fortunately, it's easily corrected.

[Robh3606]

Wow I forgot just how nice those speakers look!

Rob

[T.Rex]

If I have someone else recap these can I just remove the box with wires attached and have the tech do all the de-soldering? Also It looks as though the drivers are connected with spades...right? Are the Mid/Treble connections to the Brilliance and treble controls on the front simply soldered at their ends? From the pictures it looks like there is 1 wire coming from the crossover assembly leading to the 2. Does this wire branch out so that I can label the wires? I do not want to remove the front folical if at all possible.

thanks,

Tom

[SEAWOLF97]

I have a lovely set of Summits and was wondering about recap longevity. I know that this is going to vary, but want to keep my options open for the future. My Summits have worked flawlessly since I purchased back in 2007 as the 2nd owner........no cracks, pops.....nothing. Even the L-Pads, after treating with a little deoxit work like new. I also know that capacitors don't last forever. These are pushing 40-years old now and probably only a matter of time. I play every day, never really pushing them in a controlled environment.

reading the above, I'm wondering why you want to fix what ain't broke ?