Acoustic Research AR18EJ Loudspeakers

[SteveCG]

Well folks,

I am now the proud possessor of a pair of Teledyne AR AR18EJ loudspeakers - serial nos 79852 and 3. They are missing their speaker grill covers and also the foam surrounds of the bass units. Apart from that, if run with the 'speakers up side down (to avoid the cone rubbing, noticeable when they are the right way around), they both work.

I can see on ebay that some replacement base unit foam surrounds are sold - but my question is this: is this a feasible fix?

More generally, in the pantheon of Loudspeakers where did these sit?

I think they must date from the mid 1970s.

[Andrew2]

I would imagine accurate alignment would be extremely difficult unless you used the old 'feeler gauge' method. You need to remove the central dust cover to do it.

[RojDW48]

Very well thought of - especially by American enthusiasts. Re-foaming is quite straightforward - I did on all the drivers for an ancient Wharfedale SFB3. Have a look on the interweb for really helpful vids - there are various methods - I favoured the one with all the clothespegs!

[GrimJosef]

Yes, replacing the surrounds on bass speakers is perfectly feasible. How well it works depends on a) whether the new surrounds are really similar to the original ones (does the physical size actually match, are the compliance/stiffness and range of travel the same ?) and b) how well the replacement process goes (is the magnet gap nice and clean, does the voicecoil end up centred, is any damage done to the cone in the process e.g. at the edge when removing the last remnants of the old surround and/or in the centre when removing the dust cap to allow the coil to be centred ?). Among the hifi community I've come across quite a few reports of first-timers successfully replacing surrounds on a range of speakers. It seems you don't need to be particularly skilful to do it, just careful and prepared to follow the instructions.

Cheers,

GJ

[DonaldStott]

I'd agree with the comments above that re-foaming is quite straightforward and perfectly feasible. Plenty of advice and guidance to be found on the internet but the main skill you require is patience.

I re-foamed a pair of AR28s and they now sound fantastic - in addition I also replaced the large capacitor on the crossovers. Another quick job if you have basic soldering skills.

Recreating the grill covers shouldn't be that challenging either - plenty of sources for grill cloth and fixing studs, try here: -

https://www.wilmslowaudio.co.uk/grille-covers-146-c.asp

Post us some pictures and let us know about progress.

[SteveCG]

Thanks folks.

I can see it is a 'round-tuit' job that I'll pick up again later. I'm encouraged by what has been said -and also appreciate Grim_Josefs' points.

[DonaldStott]

I also have another pair of AR28s on my 'round-tuit' list of pending projects - once I get round to doing them I'll post something here.

[MurphyNut]

They were highly regarded, I remember reading very favorable reviews in Hi-Fi News and record review back in the 1970's.
I nearly bought a pair but for some reason opted for Kef Corelli's instead.

[dseymo1]

I have a pair of AR18s here on my secondary system - 'impressive' rather than natural-sounding, perhaps, but nice nevertheless.
Bear in mind that these are an 'acoustic suspension', i.e. infinite baffle, design, so the characteristics of the surrounds may not be the same as those of typical reflex designs.

[Beobloke]

Originally Posted by GrimJosef

Yes, replacing the surrounds on bass speakers is perfectly feasible. How well it works depends on a) whether the new surrounds are really similar to the original ones (does the physical size actually match, are the compliance/stiffness and range of travel the same ?)

Whilst I completely concur with these points, I'll offer the theory that a drive unit refoamed with a surround that isn't quite the same specification as the original still sounds better than the same driver with an original, but completely knackered surround!

[SteveCG]

Beobloke, I agree with you - I think my thoughts were along the lines of: For all the cost and effort involved would the end result be worth it? Grim_Josef summarises the issues nicely.

[dseymo1]

Well, generic surrounds are pretty cheap these days, and despite suggestions to the contrary I've never found refoaming to be a particularly difficult task.
Why not give it a go?

[SteveCG]

dseymo1,- yes, I just might, but not at the moment - other things have a higher priority.

[SteveCG]

desymo1, - You might like to know that I followed up your suggestion and looked at generic surrounds on both ebay and Amazon, and have ordered a pair. Have you a suggestion for an appropriate glue, PVA? or UHU perhaps?

[dseymo1]

I've used PVA successfully a number of times. The trick, of course, is to ensure good contact while it's curing. It's useful to have some sort of jig, a bowl for instance, to support the driver cone-down during the process to ensure this.
Don't try and do the whole job at once - fix the surround to the cone first, as concentrically as possible, allow it to cure overnight, then fix the surround to the chassis. Experiment first to find the best surround mounting: some are better fixed to the back of the cone, some to the front.
As long as the spider (or equivalent) is still intact, the cone should be more-or-less self-centering, but it's worthwhile working it in and out and imposing a slight tilt, and 'feeling the limits' as you glue the surround to the chassis.
If it all goes pear-shaped, moderate heat will soften the PVA and allow you to have another go!

[Diabolical Artificer]

They usually send you a little pot with the surround's Steve and a diddy brush. Wouldn't use UHU, it's the worse glue in history for dribbling everywhere and not the best for this job. PVA is ok but there are far better glue's out there for t' job, you want something that goes off slowly so you can re-position the surround's, also straight PVA doesn't bond well to metal. The Dutch co that sells surrounds also sells said diddy tubs of glue.

Loads of youtube video's out there on this subject, I'd recommend watching a few for tips, like using a microwave/cake twirly round base thingy.

Andy.

[SteveCG]

Thanks folks - I just have to wait now for delivery (about 3 weeks the vendors say).

[BulgingCap]

I have done several replacement suspensions, including a pair of unknown Teledyne AR speakers recently that I found for $10 at a garage sale.
They feature a 'wrap around' draw-string speaker cloth that I could not remove to verify the state of the drivers at the point of sale.
Years ago, when I worked in Singapore, I found a shop that sold suspension surrounds, so bought a big selection as I could not remember the size needed for some old defunct Allison 4 speakers that I have.
The technique that has worked for me is to remove all of the old surround and glue. Then estimate the inner diameter of the new ring and draw a pencil line around the face of the cone, using the technique of the third finger to keep a constant distance from the edge. This ensures that the ring can be centred visually when glued. I was advised to use a glue such as 'Copydex' which is a latex based adhesive. I could not find this product in Oz but have a tub of something that I used to lay vinyl floor tiles years ago. This is tacky, and can be used as a 'contact' adhesive on the cone face.
I 'lift' the cone to enable the ring to be glued without the outer part touching the speaker frame. I do this by pushing chop sticks through the holes in the frame.
Then the glue can be applied to the frame and the ring pressed down evenly. The ring has always seemed to centre itself, although I carefully deflect the cone to check that the voice coil is not binding. It seems that the ring has to be moved a long way out of true visually before this binding occurs. One one occasion I attached a signal gen to the speaker and applied a low-Hz large excursion to the cone to check as it was glued but I don't think it is necessary to do this.
One tip at the end of the job- it seems that the ring often obscures the mounting holes. Don't attempt to drill the holes !!! Use one of those El Cheapo 'star wheel' useless leather punches to cut the holes.
The pics show: the ring glued to the cone; the ring with glue applied; and the speaker with original ring removed (I know the tweeter is damaged- it has been replaced. The Allison 4s were found on the back seat of a car connected to the car radio..!)
Regards, BT

[SteveCG]

Since I'm new to this game and am still awaiting the surrounds (I'm not expecting any glue to be sent with them), I looked up information on Copydex glue and other latex rubber based glues on the Web. I gather that Copydex has water and ammonia added whilst other glues use alcohol as a solvent. I wonder which sort would be better. A Dutch firm was mentioned as supplying glue with the surrounds they sell - does anybody know what type of glue it is?

[GrimJosef]

Most of time the glue for surrounds seems to be PVA (as in Evo Stik wood glue). You need something which will make a pretty strong bond, given the repeated flexing it's going to get.

Cheers,

GJ