RCA LC9A's & Crossovers

[thetubeguy1954]

I just acquired of VERY rare and VERY desirable set of RCA LC9A enclosures. For those who don't know these were developed to compete directly with Altec Lansings VOTT. The RCA's are IMHO so much better looking, even my wife hasn't complained about them and they're fairly big at 44'H x 36'W x 28" D

What I received were 2 empty enclosures. My plans are to use TAD 2001's on the top mid/high horns and a pair of "designed to Jon Lane's specs" 15" TC Sounds woofers.

These speakers were originally crossed over at 500Hz. As the enclosures and their horns were designed with that fact in mind, I'd like to do the same. Before I ask the question keep in mind I'm not real DIY orientated, so this will be my first real attempt at a major project ok?

So after many words here's my question. My thoughts are that I should look for either a vinatge JBL or Altec crossover that uses 500Hz as the cutoff frequency and then after listening try to tweak it by ear? OR Do you guys think I should build the whole crossover from scratch? I'm open for any constructive comments or suggestions.

In case this helps my setup consists of BlueNote Stibbert CDP into a Mastersound Reference 845 Integrated amp out to the RCA LC9A's.

Thanks for any help you might provide, Thetubeguy1954

[sdclc126]

You should only consider building a crossover from scratch or "tweaking" an existing one if you have measuring equipment - you need to know what everything is doing, beyond what your ears can perceive.

You are also using non-original drivers, correct? So even the crossovers that originally came with these speakers may not be appropriate, including the crossover frequency. Hopefully someone here knows enough about the drivers you've chosen and these cabinets that they will be able to make some recommendations.

Those are gorgeous cabinets - couldn't have been cheap - I'd hate to see you do anything other than the best possible build for them.

[thetubeguy1954]

CLC thanks for your comments. This weekend my friend Paul B, visisted and we opened the LC9A's to have a look inside!

As you know I originally thought I'd need to build custom crossovers. However to my delight when I opened the backs of the enclosures the original XO's were inside! I was pretty excited about that. My friend Paul says the caps are some of the very best every made.

Unfortunately with my bad back, restoring them will be a long slow process. First I'll be stripping all the white paint. Then I'll use wood filler to fill all the uneven edges & sand as needed. Next I'll tighten up everything that can be manuelly tightened. Then I'll fill any remaining open seams & sand again! Then I'll prime all wood & fiberglass. Paint the upper & bass horn. Paint all remaining surfaces that aren't black, burgundy, to match the Mastersound amp and the stand it sits on! Paul has even offered me some beautiful burgundy grill cloth to cover the area under the bass horn.

I plan on taking pictures all through the process to keep for posterity! Not only will I have one of only 100 pairs ever made, I bet I'll have one of the best looking pairs! I've added a picture of the RCA LC9A's in my room...

[bushroot]

Holy giant cabinets Batman!

[infinia]

Hi
It's my understanding that the TC woofers are of the long excursion low sensisitivity variety. It seems you'd never get them to mate well with a HF horn unless you bi-amp. The most reasonable approach would be to investigate the enclosure volumes and its original tunings and start thinking of PA drivers as possible candidates for matching with a high sensitivity low distortion HF compression driver. So IMO firstly start measuring volumes, path lengths, reflex openings etc. Also draw up the original crossover schematic if you are able.

[sdclc126]

Though my knowledge is limited, I'd have to agree with Infinia - it's great that you have the original crossovers, but you need to mate them with drivers (very) similar to the originals for it all to work right. These are high efficiency speakers all around so the woofs have to be also. Bi-amping might be a great idea either way.

Regarding the finish - sounds like a great plan, but I'm just curious as to how the originals were done, unless what's on them now is the original?

[thetubeguy1954]

Infinia & CLC, These TC Sounds woofers are not your typical woofer from TC Sounds. The were custom designed to Jon Lane of Jon Lane Design, specific specifications. I believe Jon had to agree to minimum purchase of 100 pairs for TC Sounds to tool-up to custom build these woofers to Jon's specs.

The TC Sound woofers I own have cast four-legged frames, 3.5" flat wire coils, heavy copper Faraday motors with underhung geometry and precision machined gaps, vented poles, hard paper cones, cloth surrounds, flat lead-in wires woven into the rear suspension. Xmax is 10+ mm. They're pretty much no-holds
barred, medium-to-high sensitivity 15" drivers. Jon's specs were:

NomR: 12 ohms
Revc: 9.2 ohms
BL: 25.75 TM (!)
SPL: 94.25 dB
Qms: 6
Qes: .27
Qts: .25 ik
Vas: 355 litr.
Cms: 350 uM/N
Mms: 130 Gm.
Fs on these is under 25Hz.

===============================
My friend Paul Butterfield took these ACTUAL Laud TS measurements:

‘A’ ‘B’
Fs: 24 Hz Fs: 24 Hz
Qt: 0.268 Qt: 0.284
Re: 9.5 Ohms Re: 9.5 Ohms
Qe: 0.268 Qe: 0.294
Qm: 9.460 Qm: 8.888

I'm completely new to DIYing. So I'll be relying on Paul's advice a lot. He assured me I can cross these woofers over in the 500Hz to 800Hz range easily and that they are of sufficinetly high enough effciency.

CLC I'm adding a photo of the LC9A's in their stock color scheme of black and blue. If you replace the blue with burgundy you'll have good idea of the goal I'm shooting for.

Thetubeguy1954

[sdclc126]

The woofs do look good based on the specs!

I like your finish scheme much better than the original. I have a preference for veneers, which would look great on the horn and front areas of the speaker, but that's a lot of work given the amount of real estate and curved/compound surfaces you have to work with.

Keep us informed, and let us know your listening impressions when you're finished.

[thetubeguy1954]

Thanks CLC! I will definitely keep you all informed of how the project is going. I'll also post pixs along the way!

If anyone has ideas or suggestions PLEASE tell them to me. I cannot promise I'll use all of them, but who knows what I might use?

Thetubeguy1954

[HiSPL]

I hate to drag up an old thread like this, but I happened to have 3 woofers and 3 comp drivers from the LC9A in case any one is looking for some originals. All 3 woofs work fine. Of the three comp drivers only 2 have diaphragms in them, those two work fine as well.

I'm really not trying to spam the boards here. I just need to build some new PA cabinets and I don't want to abuse these classic and rare drivers in the process. I am hoping to pass them on at a fair price to someone that can appreciate them. I would love to build some big horns, but unfortunately that is not in the cards for me.

If anybody is even halfway interested you should shoot me an email at Tim(at)weaverimaging(dot)com.

Thanks Ya'll,
-=Tim=-