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Neal K

AR 8bx original tweeter?

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Hi, I just registered on this site. I got my hands on a pair of AR 8bx speakers a short while ago. The previous owner had blown the tweeters, and I replaced them with drivers that I took oput of Yamaha NS 526. These are the ubiquitous 10 mm mylar dome that Audax made and that have been copied and used on many many speakers. It acually sounds prettyu good and I didn't modify the x-over at all. It is a simple 2 pole on the tweeter with a 3 uf series and a .20 Mh parallel. The woofer just has a one pole with a series 0.46. iron core inductor. didn't keep the originals and I do not remember the model number. Does any have any information on this model speaker, and possibly know which tweeter was used  in it? This is a 2 way 6 1/2 inch AR 8BX. the other question I have is i looked at the crossover and it uses what appears to be a decent quality electrolytic and 2 iron core inductors. Will it make any appreciable improvement if I rebuild it with a poly series cap and air cores? The speaker sounds fine and look fine. I enjoy building speakers and on the other hand I am practical. There are four components in the circuit when you count the single 3 ohm resistor on the tweeter.

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Hi Neal, welcome to the forum. I don't know this line of speakers at all, but from looking at AR literature, it appears that your tweeter is probably the same as the ones used in the AR-6bx and AR-18bx. If so, this schematic for the 6bx identifies it as part number 210068. There is one available in current online auction, but it's located in the UK (attached pic).The literature is from 1988 which makes your speakers about 30 years old, so replacing the capacitor might be a prudent move. I wouldn't bother messing with the inductors, however. Best 'o' luck. 

AR 6BX.jpg

AR 6BX schematic.jpg

AR 6bx tweeter.jpg

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Hi, thanks for the welcome ra.ra. SO I had been to Classic speaker pages looking for info and crossover schematics. I did find the schematic for the 8bx. The tw in the pic, the one with the model #, is it a paper cone, a mylar "balanced drive" I.E. the AudaX 10 mm, or a fabric dome? I think what I would like to do with this is to find a pair of the 1 1/4 paper cone HF used in a lot of the "Real" AR's" I think that is a good driver. It has good dispersion, transient response, and since I cannot hear much above 15 k anyway it will work for me. It';s just I am not crazy about looking for 30 -40 year old drivers. That's a lot of miles for a voice coil and I feel like paying for some on ebay is kind of a crap shoot. Is there anything today being made anywhere that is anything like that 1 1/4 paper cone? I know the 8bx isn't a "real" AR, it's just what I have at the moment. I am going to replace the mylar driver I threw in there.  OK, this is what was on there. The screen resolution isn't great. I can't really tell if this is a cone or a dome or what and i don't remember. I should have kept it but i didn't because they were blown. I want to know just so I know my starting point. I am going to google the part # and see if I can find freq/imp chart for it.      

image.png

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The attached text is the full description of these speakers in the AR literature - - - with "one-inch low mass liquid cooled tweeter" - - so I can't help you with the Mylar / Audax / fabric dome questions. The Library does not seem to have a more detailed drawing of this tweeter. Also, I would not be the best person to recommend a more modern driver because I am mostly unfamiliar with what is available.

AR's various 1-1/4" cone tweeters are favorites of mine, too, and with some careful shopping you can be reasonably assured that they should be good for years to come. I use these all the time in many AR speaker models, but I wouldn't know how one of these might work in your project - - how to adjust the crossover.... or will it even fit your cabinet? If you look at the AR-8b (with no "x"), you'll find an excellent little simple speaker with a 6" woofer and 1-1/4" cone tweeter that might serve as a guide for your 'mod' project. 

AR 6BX spec.jpg

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Hi ra.ra, thanks for the useful info. Right the pictured driver is the one that was in my 8bx pair originally. They belonged to a friend of mine. The guy had a party and he let someone turn up a Yamaha receiver that was powering them all the way. Probably threw out an A.C> voltage. They just fried and probably melted the VC. I had a pair of extra tweets and just put them in. It sounds very good. The x-over does have a 3 uf capacitor, and also a .20 mH iron core inductor in parallel. The LF has a single iron core 0.46 in series. There is a 3 ohm resistor and these components are mounted on a small PC board behind the connector. All right i am going to see if the pictured tweet is still available. i'll grab it, and put it in one of them then i will A - B the two. I think that if you can cross over somewhere below 2000 hz it's might have better phase/tracking. A lot of AR and KLH variously have crossover points at 1200, 1400, 1800. and many of them use a simple one pole filter! It's a testament to how well some of the drivers are built that they can handle it and sound great. A lot of the drivers were designed to work together and have complimentary roll off curves. And herein lies one of the secrets as to why these AR and KLH sound so good and hold up. We'll see what happens. To be continued.....

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1 hour ago, Neal K said:

The guy had a party and he let someone turn up a ... receiver .... all the way. ...They just fried ...

Musta been a great party until the music died. :lol: 

1 hour ago, Neal K said:

It's a testament to how well some of the drivers are built....

I agree with this - -- it's great to discover certain speaker models with such simple circuitry that produce excellent performance.

(Edit: Hey Neal, I had not noticed you are located right here in Cambridge - - - I'm sure you've got neighbors nearby with AR speakers, and don't forget to keep your eyes open on trash day in your neighborhood!)

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20 hours ago, ra.ra said:

Musta been a great party until the music died. :lol: 

I agree with this - -- it's great to discover certain speaker models with such simple circuitry that produce excellent performance.

(Edit: Hey Neal, I had not noticed you are located right here in Cambridge - - - I'm sure you've got neighbors nearby with AR speakers, and don't forget to keep your eyes open on trash day in your neighborhood!)

Right next door in the Allston section of Brighton there is a rehearsal studio called the music complex. They rent out rehearsal space for drummers and bands. I know a lot of the guys there, in fact this is whee the 8bx pair came from. I've found all kinds of equipment that either got left behind or discarded. You would be surprised how often you find speakers. I have a pair of Yamaha 12" 2 ways that were just left there. I have them on ebay. Yamaha made a speaker that was intended for studio monitoring called the NS 1000. The NS stood for natural sound. It id a sealed cab with I believe a 10" woofer, and get this: berillium dome midrange and tweeter. I heard a pair once when I was at Berklee college of music and I remember being quite impressed. 

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Always keep your eyes peeled for those discarded goods! :rolleyes: Don't know nuttin' about Yamahas, but sounds like you're hanging out in the 'hood where Aerosmith first emerged (not exactly my cup of tea, FWIW). Being in Cambridge, I hope you know you are at epicenter of the early New England speaker industry (Acoustic Research, KLH, Advent, A/D/S.....).

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On 11/30/2018 at 9:15 PM, ra.ra said:

Always keep your eyes peeled for those discarded goods! :rolleyes: Don't know nuttin' about Yamahas, but sounds like you're hanging out in the 'hood where Aerosmith first emerged (not exactly my cup of tea, FWIW). Being in Cambridge, I hope you know you are at epicenter of the early New England speaker industry (Acoustic Research, KLH, Advent, A/D/S.....).

You are not kidding, I have a friend who is sort of an expert at finding discarded equipment. Right next door to Cambridge is what we used to call a student ghetto called Allston /Brighton.

I say used to because there are fewer and fewer "Affordable" apartments in the metro Boston area. But Allston is the name of the neighborhood where HBS is. My friend Blaine goes out on runs during what he calls "Allston Christmas". It's late august/early Sept. That's when the standard Boston lease is up on August 31st. you find furniture, luggage, electronic equipment, and speakers! Because sometimes it's more practical for them to discard stuff and just buy it again than paying huge shipping costs and the logistical nightmare of relocating. Blaine is the night person at the music complex. That means when someone leaves, or or has to leave due to unpaid rent, he is usually the first in line to inherit gear that has been left behind.  Between Allston Christmas and the complex we get our hands on a good deal of stuff...like my AR 8bx pair..... 

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On 11/30/2018 at 9:15 PM, ra.ra said:

Don't know nuttin' about Yamahas

I've never heard them but the Yammy NS1000,NS1000M is supposed to be very good https://www.tnt-audio.com/casse/yamaha_ns1000m_passive_e.html or for a Stereophool review: https://www.stereophile.com/standloudspeakers/yamaha_ns-1000_loudspeaker/index.html

They have a bit of a cult following. Produced from 1974-1995, they initially sold new for $500/pair but they seem to go for 4 or 5 times that amount (or more) on the used market!

Apparently very bright but supposedly very accurate. Probably not for fans of the New England sound. But I digress....

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