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72.48.94.34
I have two Spectralinear model 1280 speakers to repair for someone. Here is the description on the lable attached:
Spectralinear 1280
System Components: (4 component driver tower system) 12” (30.5cm) large excursion bass radiator
8” (20.3cm) Foam-edge suspension low/mid frequency driver.
4 ½” (11.4cm) sealed back edge treated midrange.
4 ½” Vertical aperture high frequency radiator.
Crossover Frequencies: 2000 Hz and 4500 Hz
Nominal Impedance: 8 ohms
Frequency Response: 34 Hz to 18,000 Hz
Recommended Amplifier Power Range: 5 – 50 watts (RMS) continuous per channel.
Cabinet: Simulated walnut grained finish with protective Melamine coating.
Dimensions: 34 ¾” H x 14 ½” W x 11 ¾” D (88cm H x 37cm W x 30cm D)
Shipping Weight: 41 lbs. (18.61Kg) each, packed 1 per carton.
LIMITED WARRANTY
Two Year Unconditional Parts and Labor Guarantee on all internal loudspeaker components providing unit is not abused, used beyond its intended limits or for professional use, or repaired or altered without our acknowledgment. Transportation charges to our factory or authorized agent not included. Repaired units under warranty will be returned freight pre-paid. See your dealer for in-warranty repairs.
SOLAR AUDIO PRODUCTS, INC.
3228 E. 50th Street, Los Angeles, Ca 90058
The foam surrounds on the 8" low/mid range drivers have completely disintegrated. I have new foam surrounds on order from Parts Express. The voice coils check OK and the voice coils move freely in their air gaps, so I expect the repair to go well.
The woofers are in good shape, so no repairs are needed there or with the midranges or tweeters. There are no adjustable level controls and no circuit breakers inside. The interior of the cabinets are lined with fiberglass. There is no tuning port so apparently they depend on the 8" low/mid driver to provide some loading and phase boost to the woofer at the low end. It will be interesting to see how these sound when repaired.
The owner uses them with a Kenwood-Trio KR2600 receiver which appears to be rated at about 15-20 watts per channel. The speakers likely are high efficiency speakers to be driven by amplifiers of relatively low power. I haven't seen anyone else post anything about these speakers so this is posted primarily for information.
Solar Audio Products, Inc. appears to be out of business after a run from late 1970s into the early 1980s or so. An internet search does not produce any indication of current products on the market.
Follow Ups:
I used a Parts Express P/N 260-920 8" speaker surround repair kit. It went together nicely and results were good. Listening tests shows that the speakers are high efficiency SPL units with bass appropriate for rock and disco music. They are somewhat shrill and need to be played with treble controls turned down some to produce a more balanced sound. The receiver used with these units since new is a Kenwood KR2600, which seems well matched with these speakers. I would say these speakers are not for a critical listener.
Joe
I ran some swept frequency response tests and found that one of the 12" passive radiators was making a buzzing noise at about 37Hz. It seemed related to the edge surround on one side. I applied some Aileen's clear Tacky Glue to that area of the cardboard edge rim and left it overnight to cure. Result - same vibration. Further investigation showed that the convoluted edge surround (rubberized cloth) was actually slapping against part of the cut-out in the cabinet! I discovered that I could get the same effect on the opposite side of the passive radiator. My suspicion now is that this has been an issue with this radiator since it was manufactured. The cut-out should have been about .08" larger radius. The radiator is glued in place from original manufacture. Removal and change of cut-out size is not an option. To do so would destroy the passive radiator.
My next attempt will be to use some GE clear silicone caulk on the backside of the edge surround where it meets the cabinet cut-out. This should stabilize that part of the edge surround and stop the cabinet slapping noise.
I received the new foam surrounds for the 8" speakers in these units and began the repair on the first unit. I decided to look closer at the interior of the cabinets. It turned out that what I first thought was a 12" woofer and 8" mid-bass or mid-range was actually a 12" passive radiator and the 8" is the active woofer. The 4 ½" midrange is fed by an 8 mFd @50V NP electrolytic. The 4 ½" slot tweeter is fed by a 4.7 mFd @50V NP electrolytic. That is the extent of the "cross-over" network. There are no inductors and no level controls. This is a very simple design.
The new foam surround has been attached to the first 8" woofer edge. It must dry for a minimum of 1 hour. Then I can glue the outer edge of the foam surround to the basket (allowing about 5 minutes of dry time between application of glue film to basket surface and back side of foam surround outer edge before pressing into place. There are shims keeping the voice coil centered while the first glueing operation cures. It will be interesting to see how these speakers sound after repair.
As it turned out, I finally had to replace the 8" woofers and used some MCM 55-1190 units. The old woofers had damaged voice coils from being operated with disintegrated foam surrounds. The repair kit did not keep them from continuing to make scraping and clicking noises.
The new woofers worked well, but revealed a problem with one 12" passive radiator, whose edge was slapping against the baffle cut-out on one side of the cabinet at about 40Hz. Since it was glued in place and not removable, I wound up putting some clear GE silicone caulk along this outer edge and managed to stop the noise.
I did replace the 4mFd and 8mFd non-polarized electolytics with 4mFd and 8.2mFd polypropylene caps from Parts Express. The cabinets have a pretty good fiberglass lining already, and I was satisfied with the repair after running several frequency sweeps of 20Hz to 100Hz which smoothed out nicely. Best response from the bass region is from about 30Hz and up. Some useable output is obtained down to about 20Hz but several dB down.
The Kenwood KR-2600 receiver that drives these speakers has very effective tone controls and does a good job of quieting the treble response to a satisfactory level. The owner has been used to this for years, so I saw no need to do more to the speakers.
Thanks for the input though. I never know when I may encounter a similar situation that may need the level controls added.
Joe
I would replace the caps on the mid and tweeter with equivalent value polypropylenes. Since you find the highs somewhat shrill, you could install L-pads on the tweeters to tame them. Parts Express #260-248 (8 Ohm, 15W) should be fine, and will let you dial in the treble balance precisely.
You could probably put some constrained layer damping material and a couple of cross-braces inside each cabinet, and tighten up the bass performance a bit.
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