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Linear Suspension Laboratories

RMBRadley

RMBRadley

New Member
I have recently acquired a pair of vintage speakers from a company called Linear Suspension Laboratories that apparently was in the Chicago area. They are model HD401's. (See attached photo.) They sound great, in the same league as Large Advents, maybe a touch better. Full, balanced delivery. I have not pulled them apart to see what the drivers look like, but they are heavy and the cabinets are pretty quiet in a knock test.

I haven't been able to find anything on line about the speakers or the company. Anyone ever heard of the company?
 

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I'm sad you didn't post pictures of the the front of the speaker, with and without grill (if it is removeable). I have no knowledge to share, but am curious.
 
I will post more photos later today, I am traveling and had the "back of the speaker photo" with me. I will be back at the speaker's location today and will do some more digging. I like to find as much history as I can on old finds, part of the fun of vintage gear!
 
Interesting. From the name, I would have thought they are white van...but you said they sound good. Interesting there isn't more about them online.
 
They could be that era's white van, which was inexpensive, but reasonably impressive looking, speakers made to be included in systems. Retailers had only limited wiggle room with complicated components like receivers and turntables, but any cabinet maker can make a good looking speaker cabinet, and inexpensive drivers and simple crossovers don't add much to the cost, so there are a host of little known and unheralded marques.
And many of these products sound fine - not compared to Quad Electrostatics or whatever, but for the price, they delighted many, including a lot of AKers, back when we had hair.
At the same time, there were also plenty of serious audiophiles who thought they could design and produce speakers that would raise the bar, and maybe they did. But it is an unforgiving market, and most makers stumble and eventually fail. So the question is, were these speakers unknown greats, or just regular product?
 
Additional photos of speaker and the midrange driver. They are 4 way designs with a 10" woofer (acoustic suspension, sealed box with 1 internal brace), 4" mid, 2" tweeter (behind screen at top left), and horn HF tweeter. Probably weigh around 40 lbs. Looking at the serial number I was thinking that it may be the production date, which would make them from 1972. Drivers don't have any markings on them.
 

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They measured at 6.8 ohms. And again they sound really smooth, with strong tight bass for their size, with voicing similar to the Large Advents. I did re-foam them. The speaker terminals are spring clip, but they have an RCA jack in between the terminals so you could use that to connect as well. All this points to nothing really special in the design. I got them for free so they are a great value! They came from the estate of a friends father who was a musician and music instructor/directo director and old-school audiophile.
 
Odd looking midrange, that is rather distinctive. If I had to guess under the protective scree/cloth is a phenolic ring type tweeter.
 
Both the midrange and the woofer appear to have been modified by the maker, which suggests a more deliberate and musically purposeful approach than the simple 'toss some drivers and a basic crossover in a box' plan that is typical of white van and loss leader speakers.
 
That flower design bead of some sort applied on the midrange driver cone is a new one to me but would strengthen the cone and reduce break-up nodes and mass load it a bit. That took some time and effort to apply, so this is definitely not a white van speaker but seems like more of a local stereo store or chain house brand type speaker. The woofer looks decent, the midrange driver looks inexpensive but has that cool pattern applied, the tweet is a phenolic ring, and the super tweeter looks like a standard Motorola piezo unit from the 1970's, so I'd say mid 70's house brand model. If it sounds as good as a Large Advent, then that is quite a compliment to it's designer.
 
My guess is the woofer was refoamed using shims, and whoever did it replaced the original dust cap with a larger one.
 
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