ARms1 refurb. And a mystery

[JKent]

I've read some good things about these minis so when I found a pair I bought them. But Googling them turned up a mystery: There's a pair on ebay now, SN 4851, that don't look like any I can find anywhere else

 

Edited June 15, 2023 by JKent
removed pic of wrong speaker

[JKent]

As for the ones I'm working on now, here's the plan:

1. Replace the terminal clips with 5-way binding posts
2. Replace the NPEs with film caps (some I had on hand)
3. Re-foam the woofers
4. Add damping

Regarding #4, I noticed while handling the empty aluminum cabinets that they have a definite ring. That can't be good. Was planning to get some AcoustiMat or similar product but then I found some foil-backed foam pipe insulation in my basement and it looked like it might do the job. Sure enough, much less ringing when I tap the cabinet.

[Giorgio AR]

Hi Kent, there's something wrong in the ad, the ones in the picture are automotive speakers, derived from the AR MS1...same woofers and midrange...even your ARs can be used in car put with the brackets (optional ) on the rear window!
The ones you have are the first series with US components, my next pair have Tonegen components.
They sound wonderful and have unexpected bass.

I am attaching the photos of my AR 1MSt, he assembly kit and the AR car speakers brochure

 

 

[genek]

I have two pairs of 1ms, and removing the front plate basically turns the open housings into bells.  When they're fully assembled and screwed tight, they don't ring.

[JKent]

2 hours ago, Giorgio AR said:

there's something wrong in the ad, the ones in the picture are automotive speakers, derived from the AR MS1..

Ah! Mystery solved. Thanks Giorgio. I should have looked at the instruction sheet, also shown in the ad. It says "AR 1cs car speakers".

1 hour ago, genek said:

When they're fully assembled and screwed tight, they don't ring.

Thanks Gene. That's reassuring! I'm thinking that since I've already put the foam tape in there, I may just leave it. Your thoughts? It's very simple to remove.

[genek]

The 1ms is a pretty tight squeeze, but if the foam doesn't make things bind up when trying to fit the internals back in you should be ok. Probably won't make much difference in the sound.

BTW, I'm pretty sure the 1cs didn't have an actual cabinet, just a front face with the drivers and crossover attached to it.

[JKent]

14 hours ago, genek said:

BTW, I'm pretty sure the 1cs didn't have an actual cabinet, just a front face with the drivers and crossover attached to it.

You’re right. Btw I contacted the seller and he corrected the listing 

[ReliaBill Engineer]

I learned 30 years ago not to put aluminum *anything* inside cabinets, big or small. It colors the sound. The foam without the aluminum tape would be good. On my small Realistic speakers, i used torn up polyurethane foam from a MyPillow that I don’t use. It works well for cabinet damping. 

[genek]

The 1ms cabinets are made of aluminum. 

[RoyC]

18 hours ago, genek said:

The 1ms cabinets are made of aluminum. 

...along with many other similar, popular, speakers. I'm trying to figure out what "aluminum *anything*" could possibly do to "color" the sound.

Roy

[ReliaBill Engineer]

“I learned 30 years ago not to put aluminum *anything* inside cabinets, big or small. It colors the sound. The foam without the aluminum tape would be good. On my small Realistic speakers, i used torn up polyurethane foam from a MyPillow that I don’t use. It works well for cabinet damping.”

Inside. Pretty clear, really. Why the skepticism?

Im not talking about the cabinet, whether ABS, Aluminum, MDF, particle board, solid oak, or other. 
 

In a small speaker (our subject here) I was doing some experimenting over 30 years ago, on a pair of Realistic speakers. I bought them for the walnut veneer cabinets, just $40 for the pair. Cheap 5-1/4 woofer and paper tweeter, sealed box. I installed a Peerless mid-woofer and a German polycarbonate dome tweeter. There was no batting or damping inside these little cabinets. They sounded good with the new drivers, but had a boxy/wooly/chesty coloration.

So I tried different batting inside, and some diffusers. I tried the aluminized pipe/duct insulation. It colored the sound drastically. Hard to describe, but very audible. Then I tried aluminum honeycomb used inside the wing sections of the F-14, as a diffuser. It really colored the sound! (I isolated the honeycomb pieces in polyurethane foam.) Then I tried aluminum angle pieces; that was even worse! I tried thin pieces of aluminum sheet metal, but I could still hear coloration. Aluminum rings from the back wave. 
 

Of course, I concluded that none of those ideas were good. I wound up using 2 small squares of rubber carpet backing (excellent sound deadeners!) and torn up pieces of polyurethane foam. Later, I drilled 1/4” holes in the rear to effect an aperiodic damped enclosure. I used a single order Equal-Compromise network. The end result was a neutral sounding small speaker with fast and articulate bass down to 45 Hz, and a nice level of detail and great dispersion. Rubber surrounds stand the test of time!
 

Small speakers can be a real challenge, being very revealing of flaws and cabinet damping.

 

 

 

 

 

[genek]

Aren't the inner walls of the cabinet "inside" the cabinet...?

[JKent]

On 5/30/2023 at 4:24 PM, genek said:

The 1ms is a pretty tight squeeze, but if the foam doesn't make things bind up when trying to fit the internals back in you should be ok. Probably won't make much difference in the sound.

Yup.

On 5/30/2023 at 12:13 PM, genek said:

  When they're fully assembled and screwed tight, they don't ring.

Right on both counts Gene. I couldn't re-assemble the cabinets with the foam on the sidewalls so it had to go. I only have one put back together (waiting for another terminal cup) but from what I've heard so far I'm impressed.

[JKent]

Well, they're finished. For the record;

• woofers are 200046-0 and tweeters are 200047-0
• leads from xo to terminals are white + and green -

Restoration was

• new foam surrounds
• new terminal cups with 5-way binding posts
• new caps. One 4.7uF (original was 5.0) and one 8uF per xo

The original surrounds were mounted behind the woofer cone. I started to attach them to the front, thinking it was easier and wouldn't affect the sound but it was actually easier to attach them to the backs. I used Aleene's Tacky Glue, which is quite forgiving.

I shimmed the VCs. This is useful both for centering the VC and avoiding rubbing but also because it allows the cone to be raised and held in place as needed. I probably should have hinged the dust caps but I went with new so they're just a tad larger than original.

The cabinets were in very good condition so I didn't repaint them.

The result? IMHO these are exceptionally good-sounding speakers for their small size. I prefer them to my Zilch-modded Minimus 7s. They're a little bright compared to my reference AR-91s so sometimes I play these with the 91s. Nice little speakers.

 

[scottie munoz]

On 5/30/2023 at 7:24 PM, genek said:

The 1ms is a pretty tight squeeze, but if the foam doesn't make things bind up when trying to fit the internals back in you should be ok. Probably won't make much difference in the sound.

BTW, I'm pretty sure the 1cs didn't have an actual cabinet, just a front face with the drivers and crossover attached to it.

I own a set of 1cs, yep, drivers and a simple 2nd order mounted on a steel oval plate.  There aren't too many 5.25-in models from that era and that one's a beast. I don't know why, it's one of the funnest, quirkiest pieces of my collection.

Same as the ar1ms, the tweet, a still different sized magnet structure than the vertical series, and different than the 1ms...it produces the same output as the vertical series.  The 1ms slightly lower output, based on my low end testing mic.

The diaphragm however, exactly the same all three, with a Dcr within +- .3.  for whatever it's worth.

The five and a quarter inch woofer, gets down to 80 hz fairly easy.  Currently they're mounted in a cabinet with a 12-in vertical series woofer.  I'll tell you what though crossed over at 100 Hz... It kind of solves the problem with passing over a 12" to a  a one and a half inch dome and you can do it at 100hz (always thought the ar-9/90 would have benefitted from a 100z lpf.  For whatever reason they didnt have much faith in that 8-in which is their bread and butter. It'll get down below 100hz without trying,  for that reason alone I think the Nht 3.3 goes into the boat with the ar9 with an advantage.  100 Hz to 200 Hz is a lot of real estate.

Interested to see a nine with an adjusted Low pass down to 100hz, letting the 8" high pass there as well. 

The plate is steel btw.

Scottie

[Aadams]

39 minutes ago, scottie munoz said:

Interested to see a nine with an adjusted Low pass down to 100hz, letting the 8" high pass there as well. 

This question was addressed by @Pete B sometime last year in another thread.  He surmised that one obstacle to choosing a 100hz passive crossover point for the AR9 was the already very large components used for the network @ 200hz would need to be even larger @ 100hz.

Aadams

[JKent]

On 6/15/2023 at 12:40 PM, JKent said:

IMHO these are exceptionally good-sounding speakers for their small size. I prefer them to my Zilch-modded Minimus 7s. They're a little bright compared to my reference AR-91s so sometimes I play these with the 91s. Nice little speakers.

Well, I’ll be reevaluating the Zilch/PeteB modded Minis. I just finished a second pair and discovered a problem so I tore both pair apart and will report on the results soon. Will probably compare the ARs, Zilch mini 7, modded Zilch mini 7 and some Zaph HiVi single driver minis

 

 

Edited July 6, 2023 by JKent