KLH classic Model 5 inside wiring — req. for advice

[Hafizullah]

I've got a pair of old Model 5s that I'll be restoring. Not impressed with the interior wiring and in addition to recapping (and maybe replacing the iron-core inductors with air-core), I think I'll replace the interior wiring with 16awg OFC or OCC, and prolly be silver-soldering the leads directly to the driver terminals.

Question: Should I get rid of the wire nuts and solder the speaker leads directly to the terminal strip on the crossover? I know the wire nuts don't make any difference electrically, but wonder whether they degrade the signal in any way that's audible.

Any other thoughts about my plan?

Also, once these are done and in my system, should I elevate them off the floor a bit? Floor is wall-to-wall carpet.

Thx, in advance. Deep bow to the massive knowledgebase in this group.

 

[infullview]

Once you pull the woofer and start working on the crossover inside the box you're going to want to get the job done and get the hell out (i.e. working in tight spaces is no fun). Leave it all stock and just replace the caps. Yes to raising them up a bit,

 

[Hafizullah]

One you pull the woofer and start working on the crossover inside the box you're going to want to get the job done and get the hell out (i.e. working in tight spaces is no fun). Leave it all stock and just replace the caps. Yes to raising them up a bit,

Well, I'm going to pull the crossovers anyway, to do the recap and replace the old spring clips with banana-plug sockets — and I'm 5'6" and the space in the cab isn't particularly-tight for me.

 

[RTally]

I suggest recapping and replacing the speaker terminals and calling it good. I restore a lot of vintage speakers. I prefer to buy unadulterated speakers.

I have a pair of KLH 17 that need to be restored. The previous owner converted the stock crossover to a series crossover. He also ripped out most of the original crossover components, so I need to source more than I care to. I have other speakers messed up by the previous owner, such as my pair of EPI M100 with the wrong surrounds installed that I am getting ready to refoam with the correct style surrounds.

Replacing the internal wiring is not likely to make any audible difference in sound. Replacing the inductors for air-core is also unlikely to make an audible difference unless you like to drive your speakers so loud that the core saturates. (That would be very loud).

As for the wire nuts, a good connection is a good connection. Nothing wrong with a wire nut, as long as it is correctly installed. By soldering the leads, it is often easier to make a good connection. There is no audible difference between the two connection methods.

If you must entirely rebuild the internals, I suggest recapping both speakers and then replacing the wiring on one speaker. After you finish the first rewiring, A/B the speakers with mono music. New caps will make a significant difference in sound. By recapping both and then testing only one speaker with new wiring you can find out for yourself if there is any audible difference by replacing the internal wiring. I would not expect there to be any audible difference, but it is your ears that count. You may decide it is not worth the effort to replace the original wiring and silver solder the connections.

 

[THalchuck]

You should not replace the iron core inductors with air core because the DCR of the air core inductor will be much higher for the value of the inductor. Iron core was used to minimize the series resistance of the woofer circuit and the crossover was designed based on this DCR. The saturation of the iron core inductor is sufficiently high enough to handle the rated power of the system.
Swapping the capacitors for polyester (PE) type will greatly improve the performance, with the sound stage really "opening up." PE capacitors with a 100v rating will work just fine.
If you decide to change out the internal wiring be VERY careful if you decide to solder directly to the speaker terminals. The danger is that the terminals probably have become oxidized and will need to be heated longer to get the solder to flow. This could result in damaging the tinsel wire connections which go to the voice coils should the solder in those locations also get heated.
Also, if you change out the internal wiring be certain to seal the wire holes going through the midrange boxes. Air leakage there will result in the midrange cones being "pumped" by the action of the woofer. As a check, when you push the woofer cone inward the midrange cones should not move. This could also occur if the glue holding the midrange boxes to the baffle has become compromised.
If you change out the input terminals, be certain the metal in your new terminals doesn't contact the speaker data label. Some data labels used in production were "metalized mylar," silk screeded black. If the black is scraped away it will result in a dead short between the terminals. Not a common problem but could happen.

The M-5 is a great speaker. Be certain to recoat the woofer surround and dustcap, otherwise the bass response will sound a bit "flabby." Check threads from others to find the proper stuff. Don't use Permatex or other stuff which can harden. BTW, for production it was pure butyl rubber thinned with toluene, same stuff as was used for the midrange surrounds and the suspension for the phenolic ring tweeters.

 

[Hafizullah]

You should not replace the iron core inductors with air core because the DCR of the air core inductor will be much higher for the value of the inductor. Iron core was used to minimize the series resistance of the woofer circuit and the crossover was designed based on this DCR. The saturation of the iron core inductor is sufficiently high enough to handle the rated power of the system.
Swapping the capacitors for polyester (PE) type will greatly improve the performance, with the sound stage really "opening up." PE capacitors with a 100v rating will work just fine.
If you decide to change out the internal wiring be VERY careful if you decide to solder directly to the speaker terminals. The danger is that the terminals probably have become oxidized and will need to be heated longer to get the solder to flow. This could result in damaging the tinsel wire connections which go to the voice coils should the solder in those locations also get heated.
Also, if you change out the internal wiring be certain to seal the wire holes going through the midrange boxes. Air leakage there will result in the midrange cones being "pumped" by the action of the woofer. As a check, when you push the woofer cone inward the midrange cones should not move. This could also occur if the glue holding the midrange boxes to the baffle has become compromised.
If you change out the input terminals, be certain the metal in your new terminals doesn't contact the speaker data label. Some data labels used in production were "metalized mylar," silk screeded black. If the black is scraped away it will result in a dead short between the terminals. Not a common problem but could happen.

The M-5 is a great speaker. Be certain to recoat the woofer surround and dustcap, otherwise the bass response will sound a bit "flabby." Check threads from others to find the proper stuff. Don't use Permatex or other stuff which can harden. BTW, for production it was pure butyl rubber thinned with toluene, same stuff as was used for the midrange surrounds and the suspension for the phenolic ring tweeters.

Thank you for your detailed reply. (And I did notice when I opened the cabs that the sealer around the leads to the mids had already failed, so made mental note to replace.)

I have ordered sealer from the AR guy on eBay. It should arrive this week.

I can find 14AWG air-core inductors with the same DCR, but in the interest of saving $ and time, I'll take your advice about them. I'm contemplating replacing the sand-cast resistors Because I Can — but probably don't need to.

 

[THalchuck]

The cost for those #14 wire air core inductors is the reason iron cores (actually, "I-Sheet" because the core material is the same as transformer lamination material) were used in production. Same reason for using electrolytics instead of PE or PP. Any cost differences at the production level translate to at least a 4X change in the final selling price.
The sealing gaskets for the drivers was Ethafoam, so any "closed-cell" foam tape will work just as well, and easier than using Mortite. Be careful reinstalling the drivers and make new screw holes. That particleboard has most of its strength in the skin, so the counterbore shelf for the drivers is a bit weak and reusing old holes could result in stripping, particularly for the woofers. Make your new holes a bit away from the previous holes to avoid damaging the counterbore. Rotational position of the drivers has no effect on performance.
Those "sand cast" resistors are nothing special, just some nichrome wire wound around a ceramic form. If you break away the filler material from the bottom you can see the trick. (Just for fun, that internal winding is the same thing Lionel and American Flyer used for the heating element in their "smoker" locomotives!) If you replace the stock cement resistors be sure your replacements don't have any inductance.
The biggest problem with the M-5 (and M-12) was air sealing the midrange boxes from the woofer chamber. Not hard to correct is you're doing only one or two. Use a tube of caulking to make a bead in the all the seams. You'll need to fight that white insulation material to get it all in without bending the midrange flanges. Need to get it all in to keep the midrange resonance Fb up so it doesn't interfere with the top end response of the woofer.
Just a few tips to help you get the most bang for the bucks and time you're spending. You're going to love it when you're done! The M-5 is a fine speaker.

 

[Hafizullah]

The cost for those #14 wire air core inductors is the reason iron cores (actually, "I-Sheet" because the core material is the same as transformer lamination material) were used in production. Same reason for using electrolytics instead of PE or PP. Any cost differences at the production level translate to at least a 4X change in the final selling price.
The sealing gaskets for the drivers was Ethafoam, so any "closed-cell" foam tape will work just as well, and easier than using Mortite. Be careful reinstalling the drivers and make new screw holes. That particleboard has most of its strength in the skin, so the counterbore shelf for the drivers is a bit weak and reusing old holes could result in stripping, particularly for the woofers. Make your new holes a bit away from the previous holes to avoid damaging the counterbore. Rotational position of the drivers has no effect on performance.
Those "sand cast" resistors are nothing special, just some nichrome wire wound around a ceramic form. If you break away the filler material from the bottom you can see the trick. (Just for fun, that internal winding is the same thing Lionel and American Flyer used for the heating element in their "smoker" locomotives!) If you replace the stock cement resistors be sure your replacements don't have any inductance.
The biggest problem with the M-5 (and M-12) was air sealing the midrange boxes from the woofer chamber. Not hard to correct is you're doing only one or two. Use a tube of caulking to make a bead in the all the seams. You'll need to fight that white insulation material to get it all in without bending the midrange flanges. Need to get it all in to keep the midrange resonance Fb up so it doesn't interfere with the top end response of the woofer.
Just a few tips to help you get the most bang for the bucks and time you're spending. You're going to love it when you're done! The M-5 is a fine speaker.

I'm going to reseal all the drivers to their baffles with new gook, including the leads into the mid compartment. That compartment is full of fiberglass damping, so I'll have to fuss a bit to get the drivers re-seated. I will go with vinyl or polypropylene sheathing for the leads, rather than teflon, so that I can get a good bond between sealer and the leads.

Good suggestion re the screw holes.

I have some candidates for the caps picked out, with the choices being between Jantzen, Solen, and Clarity. If you have suggestions for values of bypass caps for the big 25 µF and 16 µF caps, I'm listening.

 

[THalchuck]

Make certain the midrange boxes themselves are also sealed. The pressure from the woofer leaking into the midrange box, particularly at Fb, was an issue from time to time. If everything is apart, now's the time to take care of it.
For the woofer mounting, some have suggested installing T-nuts and using machine screws. Problem with T-nuts is they need to be hammered into the back side of the baffle, so this is impossible to do without destroying the counterbore shelf. I saw someone suggest making two 1/2" thick half-circle doubler plates and gluing them to the backside of the baffle. This way longer screws would bite into the doubler to hold the woofer in the case of a compromised counterbore shelf. Just saying.
IMHO, I would go for the 5% tolerance DMPC series. I don't think getting 1% tolerance crossover components is going to be cost effective. The big thing here is the DF of the new capacitors. The original NP capacitors had a DF of around 1%, so with the 0.001%DF Daytons you're going to hear a huge improvement in crispness. Think about what's happened to the driver performance after enduring almost 6 decades of exposure and exercise. The drivers themselves are paper cone, so over the years (again, think decades) the paper has been cycled between humidity and drying, so the cone edge/body/apex treatment has surely changed, and you have no control over these changes. Yes, we used 1% components for product development and nominal performance matched drivers, but the chances of replicating the Engineering Standard are remote. Only if you were able to check driver parameters from among a group and select dead-nuts matching drivers would using 1% components would make sense to me.
I'll probably be crucified for these recommendations, but I'm a New England Yankee and budget is always in the front row.

 

[Hafizullah]

<<
The drivers themselves are paper cone, so over the years (again, think decades) the paper has been cycled between humidity and drying, so the cone edge/body/apex treatment has surely changed,
>>
I got these 5s free 10 years ago — and in their original cartons — from someone who had stored them well, and they went into a climate-controlled storage compartment. So it could be worse.

I don't mind spending a little extra to get good components. Of course, there will be a limit to the responsiveness of these old drivers, but I figure that even with the age of the drivers, there's unrealized potential to be tapped with decent electronics. I noticed a huge before-and-after difference in replacing the old electrolytic caps with Clarity caps in my RtR HPR-12 Magnums.

The cabs are in excellent condition — not quite mint, but very few signs of their age. I don't know if I'll refinish them, but might go for new grillecloth.

 

[TroutBear]

This forum its a wonderful resource - and I respect the experience and dedication of many members. With this inn mind, they're your speakers to mod as you see fit after taking in advice. Upgrade wire as you want to - it will not be a negative. Of the caps listed, Jantzen [audio superior Z if you're so inclined] are the best of the 3. Mills are nice resistor replacements. I'm in process of refinishing a pair of Model 20s and the walnut veneer and trim has responded well to thickened Sutherland Welles tung oil w/ their oil stain added followed by a top coat of Tried & True linseed oil w/ beeswax

 

[THalchuck]

Agreed, whichever path you take for the refurbish you will be DELIGHTED with the final result. That M-5 is a great speaker. Please do report on the acoustics once you get everything settled to your satisfaction.

Regarding the cabinet finish, the later production walnut did get an overcoat spray. For me, I loved the oiled walnut. Rubbing the veneer with rotten stone (finer grit than pumice) and linseed oil a few times, then wiping it down really brought out the grain after it dried for a day or two. Don't know if this can be done after the finish has received an overspray because I never tried it. Not something I'd experiment on.

Again, please be sure to report on how this all turns out. You're the custodian of a classic piece of audio.

 

[TroutBear]

Exactly - I encountered that clear topcoat on my 20s - 150 / 220 / 320 sanding sequence prepped the walnut for the finish redo