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Odd AR-4x speakers - advice sought


mangoman

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I posted this yesterday but it seems not to have worked so, once more...........

I own a pair of very old AR-4x speakers which seem to differ from the norm in that they have a passive device in the top corner, diagonally above the tweeter; none of the images I can find on the webbie show this thing in place, they all have just the woofer and a tweeter.

They have been here about 15 years awaiting re-rubbering of the surrounds and a crossover check/overhaul and still have the original AR-4x paper labels on the back with serial numbers G20674 & G2068, but in each case bearing a large cross over the printed details and one has an additional serial number on a blue label, but that could be an inventory or auction number.

Their size is 485h x 257w x 230d (mm) and I will try and post images with this.

I would really like to know what the function of this device is; it seems to have no diaphragm inside and has no magnet, just a bumped rear with a hole about 17mm in diameter that is covered with a strip of masking tape and a black fabric disc fixed to the front plate. It must be original because the baffle has the correct inserts for the screws that hold it and it has the usual black sealant goo behind it and the rebate is black painted in the same way as the woofer and tweeter holes. I would appreciate any advice from those who know these early AR speakers as to what it is!

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I posted this yesterday but it seems not to have worked so, once more...........

I own a pair of very old AR-4x speakers which seem to differ from the norm in that they have a passive device in the top corner, diagonally above the tweeter; none of the images I can find on the webbie show this thing in place, they all have just the woofer and a tweeter.

They have been here about 15 years awaiting re-rubbering of the surrounds and a crossover check/overhaul and still have the original AR-4x paper labels on the back with serial numbers G20674 & G2068, but in each case bearing a large cross over the printed details and one has an additional serial number on a blue label, but that could be an inventory or auction number.

Their size is 485h x 257w x 230d (mm) and I will try and post images with this.

I would really like to know what the function of this device is; it seems to have no diaphragm inside and has no magnet, just a bumped rear with a hole about 17mm in diameter that is covered with a strip of masking tape and a black fabric disc fixed to the front plate. It must be original because the baffle has the correct inserts for the screws that hold it and it has the usual black sealant goo behind it and the rebate is black painted in the same way as the woofer and tweeter holes. I would appreciate any advice from those who know these early AR speakers as to what it is!

Hi there

It appears to me that someone outside the AR factory cut or hole sawed another hole in the upper right hand corner.

My reasoning is the normal AR-4X had no driver variation that I've ever read about or seen myself.

Unlike Dynaco there was no left and right mirror imaged speakers and no additional driver holes.

They did use different woofer, yes, but the location of the drivers was always the same, tweeter left of woofer centerline.

Was there 1/4" blackened Philips machine screws and t-nuts inside the cabinet?

What material is the disk?

I assume metal of course.

The extra upper right hole may have been an attempt by someone to add another supertweeter driver.

It appears that the front baffleboard driver mounting flange was not recessed as are all AR driver openings.

The painted finish on the rear tells me it is a late issue, I have never seen one this late in production.

Are both speakers identical?

More advice will come as other members read this question.

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Once more, all I can say is it's not been messed with!

The baffle is rebated for this element exactly as per the tweeter and woofer, which you should be able to clearly see in the images, and it has the same original fasteners and baffle inserts as them and the same black goo.

Also, from the images you can hopefully see that this is an engineered part, not a blanking plate.

The speakers are identical and I have just noticed that there is a signature on both paper AR-4x labels.

Thanks for the help

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The poly woofer is also not correct for a 4x.The part # comes up as being for a 20c veneer.Any pictures of the cross over.May be that will help to figure out what you have.May be an early prototype for something else.The x through the 4x label would indicate that it was not sold as a 4x.

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I am no expert on AR speakers, hence my question.

I am in the UK.

The driver sitting out of the box is the original and both speakers have the same flared polycone driver, it has an AR logo on the backplate and bears "L63TNB" and a part number 1210072-8 - looks like a 1" voice coil.

I have dug out the glass-fibre wadding (yuk!) to expose the crossover; it is as basic as it could be, a flat capacitor and an air cored inductor, with the level pot fed from the cap and thence to the tweeter and the inductor feeding the woofer.

I have added images of the crossover and the "device" front & rear for clarity.

Cheers for the advice so far

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I am no expert on AR speakers, hence my question.

I am in the UK.

.............

I thought that might be the case regarding your location. It may explain a lot of things about the seemingly unusual nature of your speaker. However, I am a bit confused about the stuffing. Many of the Euro-AR speakers I've seen here typically have multi-coloured polyster stuffing.

In any case, there are some 'experts' who visit here on occasion who are knowledgeable about speakers built in Europe for European sales. Hopefully one of them will chime in - as they say.

Cheers!

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I thought the GF wadding was a bit odd; the rear of the woofer had a linen bag to protect it but it has fallen apart!

The tweeter has no AR logo or part number but does bear a date stamp of "OCT 28 1970"

The big capacitor is American made at least, by the Industrial Condensor Corporation of Chicago USA!

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The woofer is definitely not as old as the rest of the speaker, and thereby not the original. It is a later replacement and made in the 1980's, probably put in when the original woofers first needed to have new surrounds.

The Glas Fibre damping material fits with the 1970's timeframe, the multi-coloured cotton stuffing came later (second half of the seventies).

The airvent, I have also never seen before, could it be an AR experiment proto-type?

BRgds Klaus

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  • 3 weeks later...

My thoughts also are that these may have been a demo or prototype pair as I seem to recall seeing these AR speakers first back at a hotel Hi-fi fair in the late 1960's in London at the same time as the LST was shown for the first time, but the records seem to indicate that the LST was not made until 1972, so it's a puzzle still.

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You could have seen AR-4x's in the 1960's, but not LST's.

As stated above, the woofer in your photo is not original to the 4x, nor any AR speaker into the early 80's. It is a woofer made for AR in Japan by Tonegen from the mid 1980's onward, long after the 4x ceased to be manufactured. It is well constructed, but does not have the same response characteristics as the original AR-4x woofer. Regardless of the origin of those unusual cabinets, the woofers are replacements, and the speakers will not sound as they originally did.

The crossover in your photo is the last generation AR-4x crossover, as it has the #5 inductor, and along with the capacitor type, indicates a manufacture date of around 1970. The tweeter looks like a 4x tweeter of the day. The 3rd hole in the baffle, and the device installed in it, appears to be the addition of a controlled air vent (aperiodic port) to an otherwise typical AR-4x.

Roy

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I am no expert on AR speakers, hence my question.

I am in the UK.

The driver sitting out of the box is the original and both speakers have the same flared polycone driver, it has an AR logo on the backplate and bears "L63TNB" and a part number 1210072-8 - looks like a 1" voice coil.

I have dug out the glass-fibre wadding (yuk!) to expose the crossover; it is as basic as it could be, a flat capacitor and an air cored inductor, with the level pot fed from the cap and thence to the tweeter and the inductor feeding the woofer.

I have added images of the crossover and the "device" front & rear for clarity.

Cheers for the advice so far

Hi again

I just had another looksee at your great photos.

The tweeter voice coil seems to appear to be open, as in exposed, or do I need stronger glasses?

The round plate appears to have a screen cover cover similar to an old Electrovoice tweeter and masking tape on the oposite side.

The smaller dimple appears to be a backplate bump such as with some woofer backplates, Re KLH.

There does not appear to be any air opening through the plate.

That cabinet hole does not appear to be recessed and has black paint in the recess if it is.

The front baffleboard finish does not look typical of AR-4x's.

Have you taken a look with a mirror of the T-nuts to see if they are all identical?

This is getting more interesting as the world turns.

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The LST's that I saw back at that trade fair were supposedly very new & revolutionary and so it must have been a new product launch I suppose, as AR Americanos were there demonstrating to a room full of seated peeps; they also had a driver from the cab on display beside it and I remember being highly unimpressed because it had a simple old-fashioned pressed steel U-magnet and so the coil was visible at the back of the driver. The chap claimed that this speaker could handle over 400w and I recall him being very upset when I called his bluff during "questions" by offering to go and get my 400w valve head from the car and prove it! But an open coil can shift a lot of heat I suppose.........

The bass drivers in these cabs look nothing like that one I saw back then obviously, but I have not seen any really old AR drivers of the true acoustic suspension era on the webbie and so I agree it is easily possible that they are later replacements. The drivers still work but needs a new surrounds obviously, even the tweeter still functions, (it does not have a visible coil but the coil former stands out from the cone part by a few mm with the dust cap simply glued onto the end!)

I have other old AR's here by the way and the baffles on these have exactly the same appearance as this one; as I have said already, there IS a proper, original rebate in the two baffles which incidentally are not mirror image, for this seemingly useless device and I have done as suggested and can confirm that it has exactly the same type of T-nuts fitted at the back as the tweeter and bass driver so for wahtever reason, this device is original and why I put this post in the first place.

At least we now know that the crossover and the tweeters are from 1970 and the glass fibre stuffing seemingly also ties in with that date - thanks to those who contributed for that info.

I also think the thing is some sort of air leak or, in my view, a resistance flow device and the tape looks pretty original, it's not modern masking tape certainly; without it, air could flow through it but with considerable flow resistance from the material on the front I think but I have no idea why it's there unless it is to actually stop the thing working; in other words is it a failed prototype?

From what I have read, (remember I am no AR expert!), it seems that only the early speakers truly used the air suspension concept to drop the effective Fr to get better bass from a small box, but the air flow resistance principle has the same effect and also flattens out the Q, which could explain why they maybe were attempting to get a similar effect from different, (cheaper?) bass drivers.

Once again, thanks to all who have so far rsponded

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  • 3 months later...

Just an update: despite spending many hours researching this AR4x variant I have got nowhere and because of downsizing I am now clearing out all non-essentials such as bulky speakers so, as this topic seems to have dried up, I will list these on eBay tomorrow so that someone else can pick up the ball and run with it!

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  • 5 months later...

Of interest perhaps, another pair of similar AR-4x, with a 3rd opening in the baffle, have surfaced up for auction in the UK (item# 290810852563). The woofers in these look to be original, and the labels have not been crossed out.

Robert_S

Interesting. The OP is also in the UK and put his on ebay (Item number: 330813999408). Maybe these are some weird UK-only variation.

Kent

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Robert's photo shows original AR-4x woofers, unlike mangoman's, which were equipped with later Tonegen replacement woofers.

I am convinced these are not "prototypes", but just another version of the AR-4x, possibly unique to Europe. It has become increasingly apparent that the 4x was not a completely sealed speaker system. It was an aperiodic design, which allows for controlled cabinet leakage. Most 4x's allowed the leakage past the magnet and through the dustcap. Others did not have completely sealed surrounds (take note those of you slathering stuff on your 4x woofer surrounds). These European specimens obviously allowed leakage through a fiberglass filled gap in the cabinet (as did the popular Dynaco A25 of the same era). Fiberglass filled vents of this type were later marketed by Dynaudio as "Variovents", as the amount of fiberglass could be varied to increase or decrease the amount of leakage.

Roy

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