General Speaker Advice and Recommendations

You might as well go for it, they look a little rough but for $100 you expect that.

 

Wow you're right, I didn't even think of it that way. I think I am going to pull the trigger on them.

They do look a little rough, but you're right, for $100 I can't complain! For that price I'll happily take the time to spruce them up, especially if they sound good!

 

Preface:

I have always been a headphone geek, I've owned so many pairs of "audiophile" headphones that I can't even remember which pairs I've had and which I haven't. But I have since settled down with finding my "end-game" headphones and now I am taking a step in a new (more fun, less clinical) direction, vintage two-channel. So, I went ahead and picked up the TWS RD-12 speakers I spoke about above for $100 from a local seller. As a re-cap, they were built in 1973 by a local speaker builder (Tom W. Snider) who has long since passed away and below is everything I know about them:

Speaker Information:

Size: 26"L X 17-3/4"W X 16-1/4"H (4.34 Cubic Feet Per Cabinet)

Cabinets: Solid cherry wood (Each cabinet weighs ~40 pounds)

Crossovers: Previous owner recently replaced crossovers with new ones, he is a jukebox repairman so I assume he knows what he is doing but I could be wrong! (See imgur album for photos)

Woofers Repaired: Never, they are original. The paper cones have rips, the dust caps are coming loose, and the paper surrounds are ripped and need replaced.

Note: According to the previous owner, the speakers "sounded amazing after replacing the crossovers, so much so that I almost didn't want to sell them anymore!" I'm not really sure how this is possible given the condition of the woofers, but perhaps I am splitting hairs at their condition.

Driver Information: (Taken from 1974 Utah Electronics catalog)

Woofer: Utah Electronics MH-12PXC 12" Round 8 Ohm*

Mid-Range Horn: Utah Electronics H-068 10-1/2" X 4" X 11" 8 Ohm*

Tweeter Horn: Utah Electronics H-208 7-1/4" X 3" X 6-3/8" 8 Ohm*

*I believe this is what the drivers are based on how they look and the "Utah Electronics" stickers that are on the back of the woofer and the diffusers of the horns.

Issues / Concerns:

-- 1 --
Problem: Both woofers have rips in the paper cones that have been repaired with glue and their dust caps are starting to come off. Plus the paper surrounds are beginning to crumble and have tears in them.

Solution: Recone / resurround both woofers with a complete kit from one of the Utah MH-12PXC's closest relatives, the JBL K120-8 or the Altec 421-8H. All are 12", 8 Ohm, 1970s-era, alnico, guitar amplifier speakers with paper cones, and paper surrounds. I have no idea if either of these kits would actually work for the MH-12PXC's or not, but I figure one of them may be worth a shot. Both the K120 and the 421 even have the same silver dust cap as the MH-12PXC's do!

-- 2 --
Problem: I am unsure of the quality or "correctness" of the crossovers that the previous owner "upgraded" the speakers with. They look like some cheap pre-built kit from AliExpress or something and I have no idea what was originally in there to start with.

Solution: I am all ears for suggestions on this one!

-- 3 --
Problem: The internal wiring from the rear jacks, to the crossovers, to the drivers is all soldered, but it looks like the cheapest, smallest gauge wire you could buy off the shelf at your local electronics shop.

Solution: Replace all internal wiring with something like Canare 4S11 14AWG and replace soldered joints with alligator clips or spades for easier future repairs?

Comparing With Other Speaker Specs Of The Time:

Utah Electronics (who made all the drivers for these RD-12's) was a direct competitor of Jensen Loudspeakers and Atlas who made the woofer driver and midrange / tweeter horns for the Klipsch Cornwall I (and Klipsch Heresy I) respectively. So, if my research is correct, these TWS RD-12 speakers should be pretty similar to a pair of original Klipsch Cornwall I's from the early 70's, except with a smaller 12" woofer instead of a 15".

DIY Cost In 1973:

As an aside, the drivers alone for these speakers cost $87.70 per cabinet in 1974, which would be $500.14 per cabinet in 2022's money. Does this translate into me getting something worthwhile in terms of sound quality? Or should I have passed on buying these due to the (seemingly) small issues they have?

Conclusion:

I fell in love with the history of the speakers since they were built by a local family-owned audio shop in the 70's, so I felt like dropping $100 on them was a worthy gamble. However, I don't want my rose-colored glasses and on-paper statistics to get in the way of me owning a legitimately good set of vintage design / inspired speakers if these aren't worth the time, effort, and money to restore. If you were me, would you invest the additional money to get both woofers repaired and the internal wiring re-done with something nicer, or would you just cut your losses and run?

P.S. - Please view the imgur album for close-up views of every aspect of these speakers, including the internals. Feel free to ask me for any other photos as well. Even if these speakers end up being junk I am having a great time diving into them.

LINK TO IMGUR ALBUM: https://imgur.com/gallery/ngi8ijQ

 

weird essay, the photos would've been enough.

the woofers have three rolls in the surrounds so the tears are not really the end of the world. I apologize, however those drivers and horns are more or less 'junk', bottom of the barrel stuff as far as vintage drivers are concerned. I also highly doubt any of those magnets are alnico, they have early ceramic written all over them.

as far as craigslist finds for a Benjamin go, there's better to be had.

not even close

 

I'll let others speak to the electronics, but are you sure that is solid wood? The photo of the bottom appears to show plywood laminations and the seam on the top photo screams veneer plywood (to me) as well. Also a real strange color selection for cherry - the last thing most people would do with Cherry is put a walnut colored stain on it.

I also would find it strange that someone would go to the expense of using solid cherry and then put a particle board baffle on the front.

 

Its a veneer ply, it does look like a stained Cherry veneer.

 

Well, at least the cabinets may be worth something! So in your opinion repairing the woofers really isn't worth it at all? I wonder if I could reuse them and just get a better set of drivers all around that would work in a ~4cuFT cabinet? The size of the cabinets themselves is really nice for the space I have to work with.

No I am not sure, that is just what the previous owner told me. I don't have much experience with woodworking but wouldn't the speakers be much lighter if they were all plywood? To your last point about the particle board baffle (and rear panel) you are right, that does cast a lot of doubt on these being real hardwood.

I think you are most likely correct. Is there any way I can get a photo that would illustrate this better?

 

4.34 cubic ft cabinets are fairly small for 15" woofers. They probably won't play all that low in that size cabinet. How do they sound?

 

The woofers are 12" not 15". Unfortunately I haven't been able to audition them yet due to me not owning any power amps, only headphone amps. I have an Adcom GFA-535 II coming in the mail in the next couple of days though!

 

@InsanityOne , for $100 sometimes you roll the dice and don’t hit the big payout. This is one of those times, but if you have the need to experiment with speaker stuff to gain understanding as I do, then you gotta try sometimes.
I think at this point if they were mine I’d try a complete redesign where you pick components, design a new Xover from the ground up and then build a new front board to reuse the cabinets. I’d probably keep it simple with a two way design using a horn and either a 10 or 12. A three way will be exponentially more complex and might be too much of a first project. Maybe you can dump the old horns and get some money out of them.

 

As a first-time speaker owner I definitely agree that I need to experiment to gain more understanding of how speakers work and what makes them sound "good". I am actually leaning towards doing a rebuild like you said, and I did quite a bit of research last night. But instead of a "custom redesign" I would be taking more of a "transplant" approach.

I have always really liked the design of the Klipsch Heresy HIP-2. That is partially why I was so drawn to these TWS RD-12's. The HIP-2's are front ported and use all the same size components (woofer, midrange horn, tweeter horn) as these TWS RD-12's that I have. So my thought is that I will cobble together all the parts from the Heresy II (tweeter horn pair, midrange horn pair, woofer pair, crossover pair) and then transplant all of that into these cabinets. I have seen a couple of custom builds online where users have taken Heresey parts and put them into larger cabinets resulting in a better bass response, so I am hoping to achieve the same thing with my project!

 

Are there 2 sizes or kinds of banana plugs/terminals? I have a banana -> headphone adapter and the banana plugs fit very tight in a couple First Watt clones I had here. But I have an Akitika GT-102 and they are super loose to the point of wiggling around in the ports. They seem to make a connection as music is passing though, but they're so loose I can't imagine its' doing the sound any favors.

It would be annoying if there were two kinds, I don't really want to have to have two adapters made. But it seems that way.

 

As far as I know they're supposed to be universal but the tolerances of the plugs and posts aren't always exact and that's where you run into problems. I've experienced the same. At one time you could buy adjustable banana plugs with a screw down insert to loosen or tighten to fit any post. They're probably still made but I haven't come across them in a few years. Maybe Parts-Express has them.

 

Locking banana plugs ( far left in image) generally take care of the tolerance issue when using the same cable with multiple speakers\amps. By turning the knurled outer ring the banana spreads (locks) or contracts and gives a snug fit anywhere. I highly recommend them.

The BFA style (second from left) supposedly gives a better connection than 'standard' bananas and theoretically could be manually spread or contracted to fit whatever. Id be concerned about breakage after a while though.

 

you guys think it's possible to make a mid/side speaker array? i really want to hear how ridiculous it would sound. point source stereo is an absurd concept i can't wrap my mind around

 

There's no rule stopping you from using line arrays as side/surround speakers...

 

no, i mean point source stereo as in both effective channels are coming from a single point source. as in, one front facing cone speaker and one side to side bidirectional ribbon that are as close to coincident as possible outputting a non-converted mid/side recording. has anyone ever done something like that? a single-point stereo setup where there's no time OR amplitude difference (in space) to create stereo imaging where the formation of the left and right channels happens in the air. I'm wondering what would happen if someone implemented a mid/side microphone array "backwards"

 

I took your advice, the speakers sound "fine" to my ears as I listen to them more and more, but I feel like the potential of these cabinets goes far beyond the 1973 drivers that are in them. So, I gave myself a new project and will be upgrading all of the drivers, crossovers, internal wiring, and input terminals of these speakers. Here are the components I chose:

Tweeter Horn - Pyle PDS221
Midrange Horn - Atlas Sound PD30
12" Woofer - Jensen Mod12-50
Crossover - Custom
Internal Wiring - Canare Star Quad 4S6
Input Terminals - Dayton Audio BPA-38G

The most difficult part will be designing the crossover because there really isn't any TSP data available for the Pyle PDS221 and the Atlas Sound PD30, so using a program like Xsim to simulate the "best" design may not be possible. I reached out to someone I know who has experience designing custom crossovers though and they are willing to help. I have already got their placement in my room mapped out and I've got 28" stands on order to get the tweeters at my ear level. I can't wait to get these all put together and listen to them for the first time!

 

Might be worth it to save yourself the extra trouble and choose drivers based on availability of data.

 

You are absolutely right, but unfortunately I got a little too gung-ho and ordered all the drivers before I realized that I needed quite a bit more data than was provided for the midrange and tweeter drivers to actually build a proper crossover. Thankfully I was able to find measurements for both drivers along with measurements for horn flares similar to the ones I will actually be using. I was also able to find all of the "standard" data for the midrange / tweeter compression drivers like RMS power, peak power, sensitivity, useable frequency range, etc. so at least all of that gives me somewhat of a good base to start from.

Woofer:


Midrange Compression Driver: (Less Horn Flare)


Tweeter Compression Driver: (With Horn Flare Attached - Highlighted)