University C8W

[spacemissing]

I joined AK about ten years ago,
and I have occasionally read some stuff here,
but I think this is my first post.

Sometime in the late 1970s, I bought a University C8W (8 inch, 8 ohm, 25 watts) at a swap meet.
If I paid more than $2 for it, I don't know how.

I still have it in the crude open-back particle-board box I made at that time,
finished in cheap woodgrain self-adhesive vinyl accented with orange burlap grill cloth.
(I was only in my late teens and had nearly no money.
Now I still have nearly no money, but I'm in my late 50s.)

More recently (2011), I acquired and fully recapped a Grommes 10PG mono tube amplifier.
It lit up nicely and didn't emit any smoke on the first try.
That was a happy moment.

Somehow I think these two items should get acquainted,
but not until the C8W is in a better enclosure along with a tweeter
(suggestions for a suitable HF driver would be welcome, too).

Adding to the impetus to do a simple speaker project is the empty JBL L19 cabinet I just bought ---
could it maybe suit the C8W well enough if I tightly stuff the port with dense foam?

If anyone has cabinet plans and/or other useful info, hints, etc. for this old woofer,
I would much appreciate you passing them along.


spacemissing
(David)

 

[klipschorn]

Hello David.

Just happened upon your query. The L19 cabinet should work well with the C8W. As for stuffing the vent, just try it and give it an audition. In an old book I have titled HI-FI SPEAKERS AND ENCLOSURES by Abraham Cohen, chief engineer for University loudspeakers (1946-1953), he shows a cabinet design for 8 inch units. (photo attached) Of the two rectangular ports on the right, I venture to say the smaller (upper) one is for a horn tweeter. The internal volume of that enclosure is about 0.8 cubic feet and that of the JBView attachment 1327341 L-19 is about 1.1 cubic feet.

As for a tweeter, Parts Express (PE) has many from which to choose. I'd recommend something with a sensitivity of about 90 to 94 dB as anything higher might overwhelm the woofer. https://www.parts-express.com/cat/tweeters/17

In those 4 pages of tweeters, you might consider the GRS-PRT8 on page 2, item # 270-252. It has a sensitivity of about 90 dB and isn't expensive. Another listed is the buyout special on that same page, a T25, item # 279-452 for a mere $3.50. A 4uf non polarised capacitor (high pass filter) will filter the lows below 5khz from the tweeter. An inductor (low pass filter) for the woofer probably isn't necessary.

Ahhh, the Grommes. Several years ago, I bought a Grommes Little Jewel, the LJ6 for nostalgic reasons. Upon seeing it on ebay, I couldn't resist as I had one when I was seventeen. That was waaaaay back in 1959. I still wonder where all that time went.

I do this sort of thing as a hobby, messing around with vintage audio. I have a website that's been in the works for about 20 years. The page on loudspeakers can be found here. https://www.ln271828.net/p3.htm

With such old speakers, data like the Thiele/Small parameters are unavailable. I can derive them and when done, it's amazing how good some of those old speakers can sound in the right cabinet with a well designed crossover.

Anyway, if you need any more help with your project, just post here of PM me.

Robert

 

[spacemissing]

The reason for thinking the cabinet should be sealed is that so far as I have ever known,
few, if any, speakers of the era of the C8W had ports.
Then again, I haven't really studied the subject and I'm sure I've missed out on a lot of info.


I should say that whatever I do with the L19 cabinet must leave it unmolested
so that it could be restored to being a real L19, which was the original idea I had.

You see, I have had a pair of L19s since 1981 and they are absolutely wonderful.
I was thinking of a center-channel scheme.

A friend is a JBL-trained speaker servicer and has a lot of "stuff" I can get for fairly low prices,
although right now the outlay for the drivers and crossover would still be prohibitive.

Anyway, any tweeter I use must be the same size or smaller than the JBL LE25 or LE26
and can't require drilling extra mounting holes.
For this I would make an insert for a smaller driver, using the original holes to attach the insert.


I have known of Parts Express for many years,
and that company would be a likely source for whatever I can't get locally.

Ah, yes, the old "phenolic ring" tweeter! They were once nearly ubiquitous,
and a long time ago I installed two of them in a pair of Audio Design cabinets.
They made a noticeable improvement, though not a revolutionary one.
Funny, isn't it, how some ideas are cheap, simple, and effective across a wide arena
while more costly ones barely serve the niche for which they were developed?


One of the specs I would most like to have for the C8W is its sensitivity,
in the interest of finding a tweeter to match
(preferably a little higher, which can of course be easily reduced).

I clicked on the link to the Cohen attachment.
All I got was redirected to a plea for money to support AK.
Oh, well.


My knowledge and experience with audio and electronics is large but limited.
I've never taken a class in it, but I'm currently doing fairly well at repairs in a local shop.
Fairly --- Not expertly.
(Unlike some people, I like soldering and I'm pretty good at it.)


Thank you for the quick response.