Replacement drive for AR55BX

[mike the bike]

Hello Guys,

Happy new year to all of you.

I am newly registered on the site and considering the high level of knowledge shown here, sure I have joint the right place.
I am far from being an expert in the speaker stuffs, but eager to learn with you.

Well, here is my problem:

I own a pair of Acoustic Research AR55BX since 1986 and have not used them for 10 years. I recently decided to bring them up to life and obviously foams of the woofers and mediums were rotten. I have successfully repaired 3 drives with new foams from speakerworks, but can't do anymore on one woofer: cone twisted and rusty magnet (dust cap was widely open), I don’t think it is worth going any further with it.

The reference of the speaker is: AR – 1-2100740B – 561TNG. Size is 10” dia. No more spec available.

I did not succeed so far to find one genuine speaker. I have tried with Oaktreevintage: they don’t have it.

One dealer told me that the most suitable replacement would be a Peerless 850146, but I can’t say if it is correct and a good combination with the existing medium and tweeter.

I am actually looking into two options:
1 – Replacement by one AR genuine drive, no matter is the foam condition (I can replace it) as long as the rest is ok – So, if you can help me for possible sourcing, I would appreciate,

2 – Replacement by an equivalent drive and so, is the Peerless 850146 as suggested able to do the job? (This model is not in the Peeless catalogue anymore but stock is still on sale), Do you have any other model to suggest? Is it necessary to change both woofers? Any modification required on the filters?

Any advice is welcomed.

Thank you for your help,

Michel

[AudioFreak]

Originally posted by mike the bike

2 – Replacement by an equivalent drive and so, is the Peerless 850146 as suggested able to do the job? (This model is not in the Peeless catalogue anymore but stock is still on sale), Do you have any other model to suggest? Is it necessary to change both woofers? Any modification required on the filters?

Yes, if you went down this path you would need to replace all of the woofers from both speakers.

[sreten]

http://www.classicspeakerpages.net/a.../Unclassic.htm

you sure the model number is AR55BX ? sounds like the AR48BX.

Its important as AR used some dubious crossover methodologies,
which could make a drop-in replacement a very difficult task.
(e.g. mechanically rolling off bass units)

/sreten.

[mike the bike]

Thank you Sreten for your reply.

I know this list from classicspeakerpages and its true that the AR55BX is not in it. It seems to be a confidential edition....

However, this is 100% sure. Please look at the picture of the original packing box and of the loudspeaker itself (the one repaired). The speaker on the front of the box is the second medium after repairing.

[mike the bike]

Don't know where the pdf attachment has gone.....
I give it an other try.

[sreten]

Hmmm......

they look like europe only specials - with a finish similar to the EB101 turntable.

The drivers could still be AR though.

If your defunct bass driver does not have any weight or inserts
added around the voicecoil or behind the dust cap then it is safe
to assume mechanical filtering has not been used.
This can also be confirmed by sketching out the crossover details.

First thing to do is measure the drivers DC resistance.

Is the peeerless driver within your budget - for two ?

/sreten.

p.s. its midrange - not medium

[mike the bike]

I think they were confidential and even so I have two of the very first units (and maybe the very last who knows) as serial numbers are respectively 00005 and 00008 !

Well as far as i can see, there is no weight of any kind around the voice coil or behind the dust cap.

The speakers are all stamped AR.
The woofer DC resistance is 3.5 Ohm approx.
The midrange (sorry for the "French" medium) reference is:
AR - 1-2100730B - 263TNG. It is 6.5" dia and its DC resistance is 5 Ohm approx.

Sketching out the crossover details is not that easy because of its hard fitting in the box. Anyway i will try to take it out because i suspect some breakdown on the capacitors and after 20 years, it could be worth to replace them. What is your opinion?

Peerless are around 70 $ each. It is not that cheap but if suitable for my units then i will go for them.

[mike the bike]

I managed to take out the crossover, but the assembly is glued to the wooden plate so reading of the hidden capacitor and resistor values is not possible without a complete dismantling. Anyway, I was able to get at least the wiring diagram and measured the hidden resistances.

Going back to Classicspeakerpages , I have found that the crossover schematic for the 44BX is similar if not identical to the one i have in my 55BX (I cannot check the coils but i guess they are of same values...). This schematic is attached with this post.

The 44BX is not in the manufacturer list as well, so I tried to get more information about it, and found something on e-bay, and surprise: all the characteristics of this model match perfectly with my 55BX !
Link to 44BX on e-bay
I am now in the opinion that the 44BX and the 55BX are identical units. They were both manufactured in the UK with different numbers according to the market place. I guess that 44BX was for American market, while 55BX was for asia and middle east (I bought mine in the UAE)

So I think we can reasonably assume that what is ok for the 44BX will work out for the 55BX.

Therefore, If some of you have knowledge and experience with the AR 44BX this could be handy.

Thanks,

Michel

[sreten]

Hi,

that does clear a few things up.

The peerless 850146 is not directly suitable - you would have
to scale the crossover component values up from 3.5R to 5.5R.

Neither is a very cheap alternative I was going to suggest as
DCR is 7R according to its possibly dubious specification sheet.

However we are getting nearer. We need a 10" 4ohm driver,
(did someone mention cars ?), 90dB/2.83V (allow for c/o losses),
and that will work with a box volume of 40 litres sealed.

Your simplest option is probably going to be a 10" car subwoofer.

/sreten.

[mike the bike]

Hello Sreten,

Thank you so much for your very interesting post.
I'm still around, searching here and there for more stuff regarding my speakers and I've got some additional information.
In fact, I was wrong in my assumption of a marketing difference between the 44BX and 55BX. I understand now the main difference is the tweeter, at 1" on the 44BX and 1.5" on the 55BX. Also, I came to know that the woofer was also identical (10") on the 33BX. If confirmed, then it widen the possibilities for finding a genuine driver.

Regarding the replacement option, it seems as per your post that the Peerless is not adequate and would require some modification on the crossover. Well, unless I am forced to do so, I do not envision to go into that solution at first.
It means that what was given to me as a straight forward equivalent falls short from expectation. Thank you for saving me from an expensive mistake!

You say that a car subwoofer could be ok. Do you have any cheap and good model(s) to suggest for my system?

I have also some questions regarding your post:
Is the driver's dynamic behaviour directly linked to its electrical characteristics? How did you determined the 90dB/2.83V? Is there one (or more) software I could use myself?

P.S.: The enclosure is effectively 40 L approx internally, but is notably reduced by the separate enclosure for the midrange which "eats" up some 9 L approx. So, the effective volume for the woofer is 31 L+ only. If my assumption is right, is it still OK for the subwoofer?

Regards,

Michel