Richard Allan CG10's

Just got these yesterday and man do they have some potential. They sound very good once the back panel is removed. Not sure where to go from here but at this stage I'm thinking of keeping it simple and just fitting better HF units and maybe researching a better/alternative crossover.
Driving them with a 10wrms "T" amp.
Craig.

Allright man, awesome find! Richard Allan made some very good drivers.

I have the fullrange version of these, the CG10T. I found mine at the thrift store in ratty homemade cabs with 3 cheap cone tweeters each. This RA cone tweeter is probably decent enough, but could likely be bested with a modern unit.

Here is some data I found over the web on RA drivers:











Here are my drivers, used in the 12" Karlson:







The T/S parameters I measured are:

Re: 7.35 ohm
Fs: 38 Hz
Qms: 10.2
Qes: 0.48
Qts: 0.46
Vas: ~115 liters (a bit fudgy to measure, should be close enough IMHO)
BL: 8.25 N/A (WinISD extrapolation)
SPL: 93.2dB/W/m (WinISD extrapolation) that figure is about right

The suspension is one of my favorites, doped cambric, which is said to actually improve with time!

The enclosures your drivers are in look like they are on the small side, especially since they don't seem to have much damping/stuffing inside, so it's not surprising you like the sound with the back off better. They have a rather large Vas so will want large enclosures in general.

Enjoy your pair!

az

Awesome info! Thanks Az!
Your RA's look stunning. I'm looking forward to getting these sorted. I'll take my time mainly due to the fact that as yet I have no idea
Another member here has also suggested a higher quality crossover and wiring. These were assembled locally in the early 70's using fairly average x/over components and very basic wiring.
Ill keep everyone posted on the progress.
Craig.

T110 said:

Awesome info! Thanks Az!
Your RA's look stunning. I'm looking forward to getting these sorted. I'll take my time mainly due to the fact that as yet I have no idea
Another member here has also suggested a higher quality crossover and wiring. These were assembled locally in the early 70's using fairly average x/over components and very basic wiring.
Ill keep everyone posted on the progress.
Craig.

Click to expand...

Thanks!

We can spot a few electrolytic capacitors in the crossover, so yeah, things could indeed get better if you changed these out.

There seems to be a lot of RA drivers in Australia and NZ, good on you guys!

az

Right! A little progress. I've got a couple of 3.3uF poly caps and a couple of 0.22MH inductors to build two 1st order X/overs. Why 1st order? No idea other than I like the idea of keeping things simple. The X/over point will be the same 6kHz as the original. I'm also going to try the original HF unit too, however if I need to I will introduce a more suitable unit.
I'll be attempting a very simple open baffle design that I've got floating around somewhere between my left ear and right ear, or was that my forehead and afthead:scratch2:
Before I hatchet into things, does anyone have any advice regarding soldering these caps and inductors? I hope to just glue them to some type of board and solder directly to the wires/cables.
I'm thinking of using some course multi strand Monster Cable from some old but quite good Monster Bi Wire speaker cable.
Cheers
Craig.

The CG10's won't do much bass on OB, but it can still work for low-level, nearfield use I suppose; just watch out for over-excursion. You could also try to make the original cabinets aperiodic, either with a Scan-Speak Variovent, or a DIY solution, which can be easy enough to implement although it's good to know how to measure the resulting tuning in either case. Here's how I did it for some Philips fullrange drivers:

http://www.audiokarma.org/forums/showthread.php?t=327319

az

Thanks AZ. Food for thought:thmbsp:

Got one X/over mounted/soldered and re wired. Sounds quite promising. I'm going to follow Az's suggestion and go "Aperiodic". They do sound better with the backs on so I'll research a DIY Aperiodic vent for the existing enclosures. I'll also research some better damping materials for the inner surfaces leaving a clear path from the driver to the vent.
The enclosures may still be a wee bit small (about 28.5L) but I want to have a go with these cabinets first just to keep it simple and gain some experience.
I may also try bracing them a bit better as they are only thick chipboard which was typical of the early 70's.
Great fun this!

CG10 and CG10T might have had close enough parameters and, since an aperiodic/sealed design is pretty forgiving, maybe simulations with my driver's specs won't be too far off for yours...

28.5 liters is not bad to start IMO, at Qtc~0.99. Closed box for a Qtc~0.707 would be around 85 liters. If you add a fair ammount of stuffing inside the enclosure, you may expect an apparent increase in Vb of roughly 20-25%, so let's say ~35 liters, Qtc reduced to ~0.92. Maybe this will already sound good enough and you won't need further work. If not, you need to implement an aperiodic vent that de-Q's this to a value of your liking. Personally, I'd aim for ~0.8, but anywhere from 0.7 to 0.85 might be fair, but that's quite subjective.

It's a good thing to be able to measure system resonance and Q, but going by ear is possible too. You could progressively drill ~½-inch holes in the back panel and insert small pieces of dense open-cell foam in them. Add holes until it sounds good.

The trade-off here is higher f3 though. If one uses an enclosure of ¼ the volume required for Qtc=0.707 and de-Q's it back to 0.707, one can expect f3 to go up roughly one octave. In the above example based on my driver, F3 would be ~85Hz instead of 60Hz, because the design was not pushed as far as 0.25*Vb and a higher final Qtc was allowed.

az