Rebuilding Vintage Speakers

[Shannon Parks]

I have a pair of Knight 2330K speakers. There's a lot of history between them and me, but they kind of sound soft and mushy with no treble. I almost considered putting them on the curb. Here's some nice pix from the same model on eBay:
Knight 2330K Speakers

The crossover looks like two capacitors and a rheostat. Is there anywhere on the 'net that shows some similar vintage schematics, so I can get an idea of how this worked? I'm thinking I would start with just replacing the capacitors, but thinking a true crossover and real tweeters might be the ticket. Any links to people that have done this? Hard to find what I'm searching for on Google.

Shannon

[DeathRex]

I was trying to rebuild my ESS AMT-1Bs. I emailed a guy at ESS, trying to find a schematic to get the correct capacitors. He said there are several versions and send a picture of mine, which I did. We emailed back and forth for months and then he stopped sending emails. I couldn't find the schematic online, I guess the guy at ESS wants to keep it that way.

[Hotsauce]

http://www.erseaudio.com/Second-Order-3-Way

John C.

[leadtower]

I received a lot of good advice and helpfull info with rebuilding my old Wharfedales on Parts Express Techtalk.

[Shannon Parks]

I received a lot of good advice and helpfull info with rebuilding my old Wharfedales on Parts Express Techtalk.

I'll have to check it out. Certainly, they are the crossover clearing house. Just curious if these old dogs are even worth the trouble. I'm sure they never sounded great. Maybe with new tweeters and a real crossover they will come to life?

Shannon

[leadtower]

http://techtalk.parts-express.com/showt ... p?t=191345
Hope this is helpfull.

[EWBrown]

As I remember, with this general type of 3-way speakers, the two capacitors were simply high-pass elements, one each for teh tweeter and the mid, and the rheostat /WW pot was the level control for both the midranges and the tweeters. The rest of the "crossover" function was a matter of the speakers' physical characteristics.

The speakers were about as cheap as could they could be, and still sound good enough to be sellable. The paper cone tweeters were "fair" at best... The main culprit in cases of dead or flakey HF response was that the level rheostat became corroded and no longer served as a proper resistive divider. THis was a particularly serious problem with AR speakers.

The wooden cabs are the best part of these speakers, what I would do (and have done previously for other similar speakers) is to go through the Parts Express catalog or website and find some physically compatible and suitable replacement speakers and then re-load the cabs with them. These can range from cheap to fairly costly "pro grade" drivers. The cabs generally represent about 80-90% of the speakers' sales price, and are worth holding on to, if they are in reasonable condition.

The cheap replacement speaker stuff tends to be of lower efficiency, the "pro" grade stuff can go as high as 100 dB/W/M SPL, which would be great for tube amp use.

You might want to consider changing these to 2 way and cover over the 8 inch midrange hole from the inside, or use a coaxial 8 inch driver / tweeter and then cap over the tweeter hole, which would allow for 3 way operation, with better sound than three separately located drivers.. Or the tweeter hole could be used for a tuned port. Waste now, want not...

I never mastered the art of proper crossover design, I just used the relatively inexpensive 2 or 3 way crossovers, also available from Parts Express. If you want to roll your own, they have all teh crossover parts, all the way from cheap to boutique quality.

HTH

/ed B

[Shannon Parks]

Excellent advice, Ed - thank you. May have a lull here before the Budgie (and the baby!) arrives, so I'll maybe start with adding a dome tweeter and a 2-way crossover.

Shannon

[Shannon Parks]

Swept the speakers on my Boonton last night using a technique I found online (no linkage - the doc is out in the garage). Basically I am using 10V out of the Boonton and have a 1K resistor in series with the test speaker. The woofer tested fairly textbook. Resonant at 30Hz with a pretty flat impedance out to 1kHz. Decent SPL out to 2.5kHz to 3kHz. The mid range ended up being a goofball. Its nominal impedance was 15 ohms and there was no linear region. For the 2-3kHz crossover region it was particularly crappy. (tosses Utah speaker into trash) The tweeter tested very well (linear and efficient), but dropped sharply into the void at 14kHz.

At this point, I figured my first route to go would just pop in my Infinity Polycell tweeters and use a 2-way crossover. Alas, I tested the two Polycells and both were shot (open). They must be the reason I parted out those speakers. I need to leave myself better notes next time. Anyhow, after tearing them apart, it looks like the bonding goop they smeared on the super tiny voice coil wires basically completely oxidized them away. Strange. (tosses Polycell tweeters into the trash)

So I have the boxes and the woofers. Seems that if I replaced the tweeters, the midranges and bought some 3-way crossovers that I may as well buy the woofers, too. At that point, I'd have to recalculate my bass port. Full speaker project at that point.

Maybe I can still do a cheap DIY fix with the 2-way crossover and the original tweeter and woofer.

Shannon

[EWBrown]

That old Utah woofer is probably less than it was when it was new - My Karlsons originally had 12 inch Utah FR speakers and they had aged / deteriorated to the point where they sounded akin to cheap 4 inch table radio speakers. THey were probably pretty good back in the 50s or 60s but they degraded to utter poopoo by the early 2000s

PE has a selection of Pioneer speakers / drivers with decent SPL efficiency and they have all sizes and shapes. They are also fairly inexpensive.
The "Goldwood" stuff is OK but it can quite "variable" in quality...

Just a crazy thought on my part, cover up the woofer and tweeter holes, and the port, and use an 8 inch FR speaker in the midrange hole, though this may take some work to enlarge the mid's mounting hole to properly fit a Fostex FE206E or similar.

I know, these speakers were originally intended for back loaded horns, etc, but I've used them in sealed cabs with decent sounding results. The bass response may be attenuated somethat for the lower octave, but for most purposes I find them to be very good. I've also done this with the FE166Es and the PE 0.38 cu ft sealed cabs. They start lose bass around 80-100 Hz, but for most low powered SE usage they are excellent. For most acoustic type music, they are a perfect match.

/ed B

[Shannon Parks]

Heh - after realizing everything was crap, Ed, I decided I didn't want to invest money into the enclosures either!

My buddy Thermion just bought a pair of old B&W 802s last week and has fallen in love with them, so I knew he was ripe for a trade. I brought home a couple La Scala sized boxes (20" x 20" x 36") home last night that are driverless. They're beautifully handmade, veneered and have 1.5" thick walls. Wife was just a tiny bit shocked. So now I'm perusing Madisound and Parts Express. Lot of fun!

The Knights will be turned into guitar amps - Thermion is making one for a friend and so am I. I think I've use half of an old ST35 Rev B board along with one of those PP outputs you sent me awhile back. Should work great. And I can just paint the cab black.

Shannon

[EWBrown]

Now, that sounds like a plan. And they will probably still sound better than when they were new!

Just picked up a pair of Acutex MTS-3 bookshelf speakers at a local thrift shop, for five bucks. Sounds pretty good, though not overly efficient, they definitely need at least an ST35 for them to sound good. These are two way, woofer and dome tweeter, and a small passive radiator.

They're good for the basement system or as test speakers, at least

/ed B

[Geek]

FWIW, my crossover calculator is back online

http://geek.scorpiorising.ca/lcms/index ... =crossover

Cheers!

[Shannon Parks]

FWIW, my crossover calculator is back online

http://geek.scorpiorising.ca/lcms/index ... =crossover

Cheers!

Thanks, Gregg! Do you have any suggestions for an online retailer for inductor wire? Say, varnished 15-17 AWG? Seems like picking up a 50lb spool at a hamfest would be my best bet.

Shannon

[Geek]

Hi Shannon,

Checkout these people:
http://www.superioressex.com/

Last I talked to them, they sold spools as small as 6# in the popular gagues.
(use a company letterhead if you can)

Cheers!


** edit **

I also have these people bookmarked... can't remember if I talked to a rep:
http://www.reawire.com/