Correct woofer foam kit for AR18

[RobHolt]

Hi folks,

Looking for links to the correct higher compliance foam kit for the AR18.

Seen plenty of adds and of course google throws it all up but I'd prefer to obtain a link form the experts who've done the job.

Cheers,

Rob

[RoyC]

Hi folks,

Looking for links to the correct higher compliance foam kit for the AR18.

Seen plenty of adds and of course google throws it all up but I'd prefer to obtain a link form the experts who've done the job.

Cheers,

Rob

Rob,

The most compliant foam replacements for the AR 8 inch woofer are the Bose 301/JBL 116H replacement surround and the Boston Filled Fillet replacement. The Boston surround is a bit more compliant, but the Bose/JBL surround is a perfect fit.

Contact John at the email address below:

msound@shentel.net

Roy

[RobHolt]

Thanks Roy, much appreciated.

I'm embarking on a slightly unusual project.

I've a pair of 'Teledyne' period UK built AR18 and AR8, plus a pair of non functioning AR4xa.

The 4xa were won in a charity auction for £20 but the bass drivers are shot. The cloth surrounds are torn and dust caps and shot, but the cabinets are sound.

The AR8/18 woofer drops in perfectly to the 4xa cabinet as does the tweeter once two slots are cut for the terminal. All screw holes match etc.

So my plan is use the 18 drivers in the 4xa cabinet, with the extra cabinet volume extending the bottom end - I guess this is essentially close to the old AR6/7/17?

I'll go with the single 6uf cap from 18 so the only change is the cabinet - so a sort of 'Super 18' is the aim.

Just a point of info on the AR8 and AR18.

On the surface these use the same drivers and certainly the driver numbers are the same.

However, the 18 bass driver clearly has a slightly softer cone paper - more felted if you like - and the 18 tweeter is also doped where the 8s are not.

...and listening to the raw drivers they clearly sound different so it seems that similar looking AR drivers with the same model number aren't all equal. Looks like they evolved a little over the years.

Regards,

Rob

[RoyC]

Rob,

Interesting...Over here the AR-8 had a 10 inch cone and the AR-18 had an 8 inch cone. Your project will result in a speaker very much like the AR-17 (US).

If you are replacing cloth surrounds, the Bose 301 foam is much easier to install.

Roy

[Robert_S]

Interesting...Over here the AR-8 had a 10 inch cone and the AR-18 had an 8 inch cone.

It's more likely to be the (Teledyne era) AR-8s that Rob is referring to. There's some information regarding said model in the following thread:

AR8S (or AR8SE?) refurb

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4458&p=73984

The woofers in my AR-18s and AR-8s speakers are virtually identical, save for the cone colour. I've seen the 200037-0 woofer cone in a range of tones, varying from batch to batch, from neutral to brown-grey, to green-gray. The granular surface texture and softness/rigidity has been consistent in my experience (of handling perhaps 30-40 of these, manufactured around 1981-83 ). Environmental factors, such as if the cones have been exposed to sunshine for extended periods, or dampness, can obviously play a part.

I'm sure I've seen a more felt-like quality in the cones of some early 8" Universal Woofers (#200001-x), and certainly in some 10708-1 woofers, as used in early AR-7.

Robert_S

[ra.ra]

Robert_S appears to be correct regarding RobHolt's AR-8s speakers as seen in this first post from 2008. Also, Robert-S provided the factory drawing for the tweeter cut-out with terminal tabs in this second thread, which also shows pics of two speaker projects to fit a similar tweeter.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4581

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7431&page=4

I was about to question the capacitor value (6 mf), but if you are simply taking the guts (drivers, wiring and cap) from the 18 cabinet and dropping it all into the 4xa cabinets, you're probably right about this - - no need to think it thru any more than that. This presumes that you will be using neither a switch or a pot control for the tweeter (which would have been typical for the 4xa), and that you will be simply plugging up this original opening on the rear of the 4xa cabinets.

Just a thought here, but if you modify the x-o a bit, you may be able to construct your 'Super 18' to have a tweeter control, which I think is always useful. The crossover freq. might get tweaked a bit, but the 4xa cabinets should already have one of the two control types available, and it might be fun to keep it functional.

[ra.ra]

Roy is referring to this model, which was apparently a last ditch marketing effort and was never very successful.

[RobHolt]

Robert_S appears to be correct regarding RobHolt's AR-8s speakers as seen in this first post from 2008. Also, Robert-S provided the factory drawing for the tweeter cut-out with terminal tabs in this second thread, which also shows pics of two speaker projects to fit a similar tweeter.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4581

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7431&page=4

I was about to question the capacitor value (6 mf), but if you are simply taking the guts (drivers, wiring and cap) from the 18 cabinet and dropping it all into the 4xa cabinets, you're probably right about this - - no need to think it thru any more than that. This presumes that you will be using neither a switch or a pot control for the tweeter (which would have been typical for the 4xa), and that you will be simply plugging up this original opening on the rear of the 4xa cabinets.

Just a thought here, but if you modify the x-o a bit, you may be able to construct your 'Super 18' to have a tweeter control, which I think is always useful. The crossover freq. might get tweaked a bit, but the 4xa cabinets should already have one of the two control types available, and it might be fun to keep it functional.

4xa rear pot.jpg 4xa rear switch.jpg

Yup, I intend simply dropping the 18 drivers into the 4xa cabinet so best to stick with the 6uf cap. The response is nicely integrated with just a little tweeter lift which I quite like - gives a nice fresh, projected quality without going OTT.

The 8s are indeed the Teledyne version with 8" driver.

I refoamed those woofers with a kit apparently specifically for AR drivers but they lost all bottom end weight, hence my question to those experts here.

Thanks all for the information. I'll photo the project as it progresses and pop it all into a mini article when complete.

[RobHolt]

Just a quick update.

I'm half way through sanding back the cabinets which I plan to re-oil. Since everyone online says great things about Howard feed n wax with orange oil I thought I'd try that.

Can't get it here in the uk so I have a bottle on order form the US - should arrive late next week.

But.....my fears re the original woofer foam might be unfounded.

I did some measurements today of the 18 woofer in the 4 cabinet and it looks to my eyes exactly what I'd expect, ie the LF roll-off knee has dropped about 10-15hz in frequency and the bottom end is more extended. So the foam I used seams ok. Based on these measurements I'd say the overall bass system resonance is about 65hz, and the bass response looks correct for near wall placement, is it gently tails town.

This plot shows on axis (between woofer/tweeter) at 1m with the speaker pulled out into the room. Ignore the dip at 140Hz which is a room effect.

Pretty nice overall and the tweeter integrates very nicely at the correct level IMO. The plot shows the pair - nice pair matching too

AR18 drivers in 4xa cab by trebor1966, on Flickr

The veneer seems surprisingly thick and better than commonly used today.

One of my cabinets had a long and deep scratch right across the top and I managed to sand it out completely.

I'll post a pic of the sanded and repaired cabinets before oiling/waxing.