25 replies to this topic

[JKent]

Anybody know anything about these? I found a review here:
http://www.soundstage.com/entry01.htm
and a review of the “black gold” version here:
http://www.stereophi...speakers/494ra/

I need a tweeter. Now I’m making a couple of assumptions. According to Stereophile, the “black gold mini reference” has a

1" copolymer (ie, plastic) tweeter (footnote 3) is "sourced offshore" and may come from various sources, depending on the production run. I questioned whether or not this might result in a change of sound, but I was assured that Roy Allison personally selects and approves the tweeters, and they all closely match. The tweeters in my pair were made in Italy.
Footnote 3: Bob Barr told me that the tweeter is more or less a copy of an old Audax tweeter found in such neat, cheap speakers as the original Boston Acoustics A40. If this is the case, the tweeter sounds much more civilized, less strident, than the original Audax—at least to my recollection

I’m pretty sure the “black gold” is just the plain ol’ mini reference, based on the price quoted in the article. On the pair I just bought, one tweeter was replaced with a JBL tweeter. I don’t actually HAVE these yet, but once I get them, I’d like to have matching tweeters.
Any suggestions? Should I:

• Look for some Boston A40s? (now I wish I hadn’t sold mine).
• Find out what the Audax model was and see if I can get that?
• I happen to have a spare pair of Audax TW025A2 4 ohm tweeter, 1" textile dome--these are the tweets used in the Spica T50. I bought them to use in an Allison: Four but later obtained original Allison tweets. Use those?
• Just keep the JBL tweet?

Or……?

Thanks for any suggestions
Kent

[Pete B]

Hi Kent,

I do remember the glowing reviews of these when they first came out,
and I did hear a pair in a showroom back in the day. But I seem to remember
the 10mm Audax tweeter not a 1" do you know if there was a production
change or was it always a 1".

Do you have at least one good original tweeter? Can you read the model
number off of it, and measure the DC resistance? Year of manufacture?

I have early and later Audax data books and I can try to look it up.

I could measure Fs, Qts and Rvc if you want to bring one on Saturday, in
order to try to do a better job matching it up.

[Pete B]

Those TC-50 tweeters are valuable becasue they're hard to find and so many TC-50 owners need them.
It seems better for them to find a good home in a TC-50 or Snell.
I don't think those are an exact match for the Mini References since they're textile domes.

I'm considering these as a low cost replacement for the TC-50. They're not a perfect fit being 102 mm
in diameter as compared to 100 for the originals:
http://www.madisound...roducts_id=8312

Good that you have one working system since it provides an original as a reference.

[JKent]

Hi Pete
I'll check those numbers on the working tweeter, maybe bring BOTH tweets on Sat. Unfortunately, I discovered another problem: Looks like the previous owner decided to paint the entire woofer with shiny black goo to hide deteriorating foam surrounds. The black stuff never dried completely and is a bit tacky (maybe that's how it's supposed to be to remain pliable?) but I'm afraid this probably screws up the cone, even if I should decide to refoam them (any thoughts?)

You may want to check these out for your Spicas:
http://www.madisound...products_id=374

They're the ones I bought for the Allisons.and on the page it says:
"Used in the Spica TC50 speaker"

In fact, if you want to make me an offer on them. They've never been used. I could bring those on Sat also.

Kent

[l24e]

Hi Kent,
I was wondering if you won those speakers on the Canadian e-bay? As I , after reading your post decided to Google
RA Labs .
One of the links showed a pair of speakers matching your description ( JBL tweeter ) .
This might not be of any use to you, but on the English e-bay someone is selling a pair of Audax HD 100 D25 tweeters .
Item number: 260237828422
Good luck with the restoration!!! If they are the same speakers, it looked like they needed some serious TLC.

Ken

[JKent]

Hi Kent,
I was wondering if you won those speakers on the Canadian e-bay? As I , after reading your post decided to Google
RA Labs .
One of the links showed a pair of speakers matching your description ( JBL tweeter ) .
This might not be of any use to you, but on the English e-bay someone is selling a pair of Audax HD 100 D25 tweeters .
Item number: 260237828422
Good luck with the restoration!!! If they are the same speakers, it looked like they needed some serious TLC.

Ken

They're probably the ones you saw, but they were from Pennsylvania (Item number: 350054769786). Thought I had a bargain for $10 + s/h. Oh well.....
I looked at those tweets, but I don't think they're the right ones. Besides, he quoted 50GBP to ship to Toronto. Assuming it would be about the same to the US, that's $100 USD!!!!!!!!!!!!!!!!!!!!!
Thanks!
Kent

[Pete B]

Hi Pete
I'll check those numbers on the working tweeter, maybe bring BOTH tweets on Sat. Unfortunately, I discovered another problem: Looks like the previous owner decided to paint the entire woofer with shiny black goo to hide deteriorating foam surrounds. The black stuff never dried completely and is a bit tacky (maybe that's how it's supposed to be to remain pliable?) but I'm afraid this probably screws up the cone, even if I should decide to refoam them (any thoughts?)

You may want to check these out for your Spicas:
http://www.madisound...products_id=374

They're the ones I bought for the Allisons.and on the page it says:
"Used in the Spica TC50 speaker"

In fact, if you want to make me an offer on them. They've never been used. I could bring those on Sat also.

Kent

Hi Kent, sorry I spoke too quickly. Rethinking and as best as I can determine,
the Audax TW025A2 was never actually used in the TC-50s, the later TC-50s used a very
similar tweeter, the previous version in the evolution without the catenary dome. Those are
suggested as the closest replacement, but are not as valuable as I mis-stated previously.
My own TC-50s are the later type, the tweeter domes are a bit off center because the thick
felt pad sags in time and hits the dome. I see many on ebay like this, eventually permanently
displacing it. These now have a voice coil scrape that causes a large notch in the frequency
response and probably some serious distortion.
I'm hoping to recenter them since they are unavailable at this time, and I've
already purchased the replacement domes for the TW025A2 which are supposed to fit this
earlier tweeter. So, thanks for the offer but I believe I have those tweeters once I replace
the domes. I liked the Vifa because it is a non-catenary shape and looks very similar to the
earlier version, good price also. They might work well in your RAs.

I remember that the woofer was a treated paper cone, low cost Vifa driver. Don't recall if
RA treated the cone or Vifa. Vifa was good with cone treatments and I do think that it was a
black sticky coating, could it be original?

Sure bring the tweeters and I'll do a quick measurement, then send them back to you.

[Pete B]

Hi Kent,

These are the 10mm tweeter that I was thinking of, don't know why RA calls it a 1" tweeter.
This should be it, but with a round face plate, and in 8 ohms, not sure if the RA was 8 or 4:
http://www.madisound...;products_id=96

Here it is with a Neo magnet and in 4 ohms, with no face plate:
http://www.madisound...;products_id=92

I'll measure this one when I can get to it.

[teknofossil]

They're probably the ones you saw, but they were from Pennsylvania (Item number: 350054769786). Thought I had a bargain for $10 + s/h. Oh well.....
I looked at those tweets, but I don't think they're the right ones. Besides, he quoted 50GBP to ship to Toronto. Assuming it would be about the same to the US, that's $100 USD!!!!!!!!!!!!!!!!!!!!!
Thanks!
Kent

JKent,
I am not sure but I think the tweeters that were used in the RA Mini's were those inexpensive tiny Audax ones that used to be available everywhere. *IF* this is the case, Parts Express is selling a Chinese made version of the unit. There may be/probably is differences, but they are dirt cheap to give a try. I vaguely recall reading in Stereophile a review of the RA Labs Mini's....I think it was titled something like "Allisons Black Gold". If you haven't found it you might want to consider poking about the Stereophile archives.

http://www.partsexpr...tnumber=264-840

-T

[Pete B]

Hi Kent,

These are the 10mm tweeter that I was thinking of, don't know why RA calls it a 1" tweeter.
This should be it, but with a round face plate, and in 8 ohms, not sure if the RA was 8 or 4:
http://www.madisound...;products_id=96

Here it is with a Neo magnet and in 4 ohms, with no face plate:
http://www.madisound...;products_id=92

I'll measure this one when I can get to it.

Quick Rvc measurement:
Original RA Labs Tweeter (looks like an Audax 19 mm dome - 10mmVC) is 6.24 ohms
Similar looking JBL tweeter is 4.94 ohms so I would not recommend using it.

DC resistance for the old Audax TW54A and TW74A is listed as 5.7 ohms and this
is the one I'd use as a replacement after comparing to the original RA Labs tweeter:
http://www.madisound...;products_id=96

[JKent]

Quick Rvc measurement:
Original RA Labs Tweeter (looks like an Audax 19 mm dome - 10mmVC) is 6.24 ohms
Similar looking JBL tweeter is 4.94 ohms so I would not recommend using it.

DC resistance for the old Audax TW54A and TW74A is listed as 5.7 ohms and this
is the one I'd use as a replacement after comparing to the original RA Labs tweeter:
http://www.madisound...;products_id=96

Thanks Pete & Techno. Pete, I'll probably use the tweets you recommend. Do you think they will fit the original mounting plate or will I need to fabricate something?
Tech: Tang Band speakers have a good rep for bang-for-the-buck, so that is probably a good recommendation tooo.
Kent

[Pete B]

Thanks Pete & Techno. Pete, I'll probably use the tweets you recommend. Do you think they will fit the original mounting plate or will I need to fabricate something?
Tech: Tang Band speakers have a good rep for bang-for-the-buck, so that is probably a good recommendation tooo.
Kent

Hi Kent,
I'd say that the Audax is the closest, since it has the same polymer dome
and probably the same 10mm voice coil. I'd suggest you buy these and
first A/B one against the original to see if you hear any difference.

The TB's have a larger voice coil, ferro fluid, and a fabric dome; all are nice
improvements on paper, however it is different and there's no way to
know if they'll sound as good or better without a comparision. You could
buy these first since they're somewhat better on paper, compare to the
original then get the Audax's if they're not a good match. I'd probably
want to have a pair of Audaxs as backups.
I'm planning to order a pair of those TBs with my next PE order, for another
project that I'm working on, I could add them to my list of things to measure
and let you know, if you don't mind waiting a bit.

The face plate is different, I wouldn't hesitate to cut the Audax if necessary.
Depends on how big the cutout is if you'll need a plate.

I liked this simple design, would appreciate it if you'd tell us how the
crossover is wired, the cap value(s), and if there are any numbers
on the woofers.

[JKent]

Thanks Pete
I'll order the Audax's.
The RAL woofer has a sticker on the magnet, marked "4 OHMS D-92265".
The xo consists of a 6.9uF NPE, 1.8 ohm 6 watt resistor, and an inductor (value?). I'll post a photo.
Thanks for all the help
Kent

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[Pete B]

Thanks Pete
I'll order the Audax's.
The RAL woofer has a sticker on the magnet, marked "4 OHMS D-92265".
The xo consists of a 6.9uF NPE, 1.8 ohm 6 watt resistor, and an inductor (value?). I'll post a photo.
Thanks for all the help
Kent

Thanks for the info Kent,

I don't recognize that number on the woofer, this was going to be my guess, but in 4 ohms:
http://www.madisound...roducts_id=1072

[JKent]

Hey Pete,
On your recommendation I bought a pair of the Audax TW010F1. Perfect drop-in installation--I'll just have to drill 3 new screw holes and fill the 4 originals. I also ordered 2 mylar film caps. Will post photos as soon as these are back together.
Kent

[Pete B]

Hey Pete,
On your recommendation I bought a pair of the Audax TW010F1. Perfect drop-in installation--I'll just have to drill 3 new screw holes and fill the 4 originals. I also ordered 2 mylar film caps. Will post photos as soon as these are back together.
Kent

Hi Kent,

I got your off list email where you say that the RA's are brighter than
your AR-2ax's, this might be completely normal. I tend to think of the RA's
as low cost mini-monitors, in that they should have a smooth midrange.
You could hook up an L-pad on the tweeter and see if a few dB attenuation
provides a correction that you prefer. You could then measure the L-pad
values and put in permanent resistors. Might be better to wait until I send
the original back to you.

Another experiment that you might want to try is to sit the RA's on top of
your AR-2ax's and use them as subwoofers (disconnect the jumper on back).
I'd expect this to be an impressive setup and I can offer more if you're interested.

[JKent]

Hi Pete (and others who may be interested)
Yes--I'll wait to compare the new tweet with the original, but I also need to spend some more time listening.
Compared to the AR2ax, these do seem to have that "pinpoint accuracy" typical of mini monitors, and on some recordings they really sound very impressive (Passion, Grace & Fire by DiMeola, DeLucia & McLaughlin sounded pretty awesome). I may try some female vocals next to see how that is.
And you're right--I did try the RAs and the ARs together and they they sounded pretty great! I did not disconnect any jumpers--just ran the ARs off "speaker A" and the RAs off "speaker B".
Kent

[JKent]

Here they are. New caps, repaired grille frame, new grille cloth, and--oh yeah, new Audax tweeters. They sound good, but after Pete tests the original tweeter I'll reinstall it and compare side-by-side. In the meantime, these excel on recordings like acoustic guitar, giving crytaline sound and pinpoint imaging. They're completely different from my AR2ax's of course, but I was horrified when I asked my wife to listen to Carly Simon (one of her favorites) thru the RALs, then thru the ARs. She thought the RAs sounded good, but when I swtched in the ARs (which I would have called "fuller" or "richer"), she called the ARs "muffled" compared to the RAs
Kent
Before & after:

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[Pete B]

Hi Kent,

Looks good with the new tweeters!

The JBL tweeter is difficult to measure since it seems to have thick ferrofluid
so there is hardly any peak in the impedance curve. Fs seems to be 3200 Hz,
which does pass a sanity check.

The original Allison also seems to have ferrofluid but with a small peak that
allows for a better measurement. Fs is 2800 Hz, very close to the 2900 of
the Audax replacement, also:
Rvc = 6.24 ohms
Qt of .86
Qm = .92
Qe = 13.1

The Qt seems reasonable, not sure about the others. Voice coil inductance
measures 47 uH at 10 KHz.
Here's the impedance data:
1K 7.0
2K 7.3
2.8K 7.5
3K 7.4
6.3K 7.37 Min
8K 7.6
10K 7.9

These figures are all very close the the Audax.

[JKent]

Thanks Pete (for the compliment, but especially for the info!).
I see on the specs page at Madisound they do not give all the specs you measured on the RAL, so I guess it's hard to compare (unless you also measured an Audax yourself). Here is the info they provide:
Znom 8 ohm
Re 5.5 ohm
Le@1kHz .03 mH
fs 3000 Hz
Qms -
Qes -
Qts -
Mms .11 g
Cms - mm/N
Sd .03 cm2
BL 1.3 N/A
Vas - ltrs
Xmax 0.25 mm peak
VC Ø 10 mm
Sensitivity
1W / 1m 90 dB

Kent