AR9LS restoration

[mjs]

I have just purchased a pair of AR9LS speakers. The drivers require re-foaming. I compared the 8 inch upper mid driver with those in my AR98LS. Although they have the same part number (200045-0), when a bright light source is shone through the dust caps I observed the following. The drivers on the 98LS have a seal under the dust cap that appear to make the voice coil airtight when mounted in the cabinet; those on the 9LS do not have a seal leaving an open voice coil. I have also checked the schematic drawings of the 98LS, 9LS and the improved versions. All the driver part numbers change from 2000xx to the improved version 2100xx.

I also have a pair of AR90’s which I purchased some modern non original replacement 8 inch drivers. I subsequently obtained some original drivers. The originals have a sealed voice coil and the new replacements do not.

I intend to retain all the original driver parts, but I am interested to know why there are these differences and what the affect is on the air tight enclosure. I will also upgrade the crossovers with the LSI modification and replace the capacitors.

Regarding driver wiring connections, these are normally a push on connector. Does it make sense to solder the cables to the driver to ensure a high quality connection?

Any advice and feedback would be appreciated.

Regards

Mark

[AR55]

It appears that AR may have changed the midrange design during the production of the AR98Ls. I have 2 pairs of AR98Ls speakers and a pair of AR9Lsi speakers (my vintage surround system). My original pair of AR98LS speakers (serial numbers 47xx), purchased new in 1983, have a seal under the dust cap of the 8" midrange. The other pair of 98Ls speakers (serial numbers 8840 & 9573), that I purchase recently & restored, do not have a seal under the dust cap. The 8" midranges of the 9Lsi speakers also do not have the seal under the dust cap.

I have listened to the 2 pairs of AR98Ls speakers with the same amp, mixed them up and can't say that I can hear any significant difference between my originals and the restored pair.

The differences between the 2000xx drivers in the 98LS speakers and the 2100xx drivers in the 9Lsi speakers appear to be mainly cosmetic. The 9Lsi's basket frames are painted black and have an exterior foam gasket, but I believe that the voice coils, magnets, etc are the same spec.

[michiganpat]

It appears that AR may have changed the midrange design during the production of the AR98Ls. I have 2 pairs of AR98Ls speakers and a pair of AR9Lsi speakers (my vintage surround system). My original pair of AR98LS speakers (serial numbers 47xx), purchased new in 1983, have a seal under the dust cap of the 8" midrange. The other pair of 98Ls speakers (serial numbers 8840 & 9573), that I purchase recently & restored, do not have a seal under the dust cap. The 8" midranges of the 9Lsi speakers also do not have the seal under the dust cap.

I have listened to the 2 pairs of AR98Ls speakers with the same amp, mixed them up and can't say that I can hear any significant difference between my originals and the restored pair.

The differences between the 2000xx drivers in the 98LS speakers and the 2100xx drivers in the 9Lsi speakers appear to be mainly cosmetic. The 9Lsi's basket frames are painted black and have an exterior foam gasket, but I believe that the voice coils, magnets, etc are the same spec.

functionally, if that was the only woofer, the air leak through the voice coil/dust cap may cause reduced bass response in an acoustic suspension system. but since this is crossed over in the 150-200hz range, and the 10" internal woofer and 12" woofer handling the low bass, it shouldn't have any affect on performance.

[harry398]

this topic is not discussed enough

the dust cap.

I am under the impression that ar woofers are to have sealed dust caps.  As a matter of fact, many of the older woofers have a sealant applied to the dust caps as well.

without this seal, I am not sure how the woofer will seal.

However many of the speaker surround sellers dont understand this or are playing dumb?  In fact some are selling and recommending mesh dust caps.

 

many of these vintage speakers have already been refoamed, so many times we dont know what was original

 

what are YOU (everyone) using?   solid paper dust caps?   sealant?  or?

[DavidR]

A 'screen' type of cap is OK but ONLY when used with the secondary dust cap found on some AR drivers that is sealed.

I've used the paper, felt and plastic dust caps. I usually use a black solvent based sealant but have also used Aleen's Tacky glue. What I don't like about Aleen's is that when it dries it is hard and feel it would be difficult to remove w/o damaging a cone.

[harry398]

Hi David

 

can you snap a pic of what your using?   the black solvent sealant

 

thanks

[cARver]

 I’m not sure if these videos will work, but I sealed the dust cap this afternoon using vulcanizing cement.

The first video demonstrates the leak past the cap with the paper lifting and the woofer fast movement.

449C07D5-5D75-454F-A53D-692C93221417.MOV

The second video has no paper movement and slower woofer movement.

F23D6302-F77B-4E3B-A118-662DF3DCD79C.MOV

[DavidR]

26 minutes ago, harry398 said:

Hi David

 

can you snap a pic of what your using?   the black solvent sealant

 

thanks

Springfield Speaker. They also have a good selection of dust caps.

https://www.springfieldspeakerrepair.com/SearchResults.asp?Cat=1833

[AR55]

I purchased a pair of AR-98Ls speakers new in February of 1983, shortly after they came out.  The 8" midrange (200045) drivers on those speakers have solid dust caps. 

I have since purchased and restored 2 pairs of 98Ls, 2 pairs of 98Lsi and a pair of 9Lsi speakers.  The dust caps on the 8" midranges (210045) for all of the 98Lsi and 9Lsi speakers are not solid, but are instead tightly woven, cloth that allows light to pass through .  Also, one pair of the 98Ls speakers (highest serial numbers) have woven dust caps on the 8" midranges (200045).  The other pair of 98Ls speakers have the same solid dust caps as my original pair.  I suspect that it was a conscious decision by AR to change to the woven dust cap.  I can't say that I notice any difference in the sound of the 98Ls' with the solid dust caps and those with the woven dust caps.  There is a difference in sound between the 98Ls and 98Lsi speakers, but that is primarily due to changes made by AR to the crossovers.

Note that the 8" midrange is sealed to the cabinet and the cone, spider and surround are glued all around, so I doubt that a slightly porous dust cap has a significant affect on its performance. 

I should also note that all of the AR speakers that I have owned have solid dust caps on the woofers.

 

[cARver]

6 hours ago, AR55 said:

I purchased a pair of AR-98Ls speakers new in February of 1983, shortly after they came out.  The 8" midrange (200045) drivers on those speakers have solid dust caps. 

I have since purchased and restored 2 pairs of 98Ls, 2 pairs of 98Lsi and a pair of 9Lsi speakers.  The dust caps on the 8" midranges (210045) for all of the 98Lsi and 9Lsi speakers are not solid, but are instead tightly woven, cloth that allows light to pass through .  Also, one pair of the 98Ls speakers (highest serial numbers) have woven dust caps on the 8" midranges (200045).  The other pair of 98Ls speakers have the same solid dust caps as my original pair.  I suspect that it was a conscious decision by AR to change to the woven dust cap.  I can't say that I notice any difference in the sound of the 98Ls' with the solid dust caps and those with the woven dust caps.  There is a difference in sound between the 98Ls and 98Lsi speakers, but that is primarily due to changes made by AR to the crossovers.

Note that the 8" midrange is sealed to the cabinet and the cone, spider and surround are glued all around, so I doubt that a slightly porous dust cap has a significant affect on its performance. 

I should also note that all of the AR speakers that I have owned have solid dust caps on the woofers.

 

Thanks for your information. From my experience every 8" woofer from a 90/9/9ls/18 all have a dual dust cap. A cosmetic outer cap with a solid inner type. The sealing is provided by the inner cap.

The 8" woofer is the 9ls is unique as it has a hole in the center rear of the magnet. When I blow air into this hole, the woofer moves outward away from the airflow, so the woofer is sealed from the magnet. Conversely this woofer is not sealed in my cabinet and is most like caused by the porous surrounds being sold in the marketplace.  

I have recently performed several tests illustrating this.

The foam does not develop vacuum in the first test. This woofer has no acoustic suspension.

The foam does develop vacuum in the second test. This woofer does have acoustic suspension. 

Still investigating and trying samples from other sellers. Stay tuned.....

 

[harry398]

Yes, I find Midwest surrounds to be the worst performing in terms of leakage.

 

Awful customer support as well.

 

I will post info on it soon,  great vids sir!

[cARver]

Update.

I picked up a set of surrounds (260-972 part number) from Parts Express today and confirmed it passes the vacuum test performed in my prior posted videos.

The dust cap however is not sealed.