Arranging the pieces

Vintage Acoustic Research AR98LS Restored

I had some AR98LS in the storage I picked up for $5.00 if I remember right that need some TLC, rusted screws all foam surrounds pretty much shot and the cabinets have severe cosmetic damage.

The project is done as of 12/27/15. One of the woofers had some damage but seems to not make any audible difference, well worth the $50 and 8 or 9 hours of work. The AR98LS is by far better than any Satellite Sub combo for my use in a home studio. The comparison to 8ea Sony SB1000 in 2 parallel channels (2 ohms 300 watts) plus a 12 inch Sub is phenomenal although the Sonys are nothing to sneeze at amazing sound if you hit em' hard enough, the AR98LS sound is about as flat as you can get or it can be as fat as you can get unlike the Sonys which was fat in middle base and VERY “loud” for lack of another description.
Irritation point I can actually hear the compression artifacts in some mp3 music and in definitely on Pandora now :?::-(:?:

  • I'm thinking I want a set of AR9's to fix up - Anybody?

Mini DSP 2.1 Settings

I use these with a 12“ sub tuned to 28hz crossed over at 40hz. The sub has a VERY strong EQ Boost in the frequencies below 50hz mostly found in 5.1/7.1 Surround Movies or bands such as Pink Floyd, Blue Man Group and Enigma. This curve is not unlike Subwoofer Equaliser although not as strong due to driver limits and box design is different than the intended, I have this circuit as well my current driver and box can not handle the stress of the Linkwitz curves. It will rock and does not exhibit the classic boom in car stereo systems.

Mini DSP Config File1

  1. AR98LS has a pronounced midrange from 1500-2000 hz which can be customized to fit.
  2. AR98LS base can be a bit boomy but my room is 12'x30' and exhibits a hump at about 50hz.
  3. My room has a 120hz null about 20bd down (at low volume levels) The room is roughly 13' x 29' x 7' ceiling the speakers are not oriented towards the long dimension of the room and cannot be moved far enough away from the wall to resolve the null, the 120hz null simply cannot be resolved without expensive and simply impractical wall and ceiling treatments. I will attempt a 4” deep bass trap behind the speakers but I doubt that will resolve anything.

REW Measurements Here

Without EQ

Without Sub

With Sub

With EQ

Without Sub

With Sub

Crossovers / Electronics

Crossover parts List if needed $410 in 2015 not something I would just do for the heck of it
I will test all the caps with a Capacitance Meter since I have one…

2x350uf capacitors in speakers (ordered 2 x 250uf + 2 x 100uf NPE's)
2x3uf capacitors in speakers (ordered 2 x 2.7uf + 2 x .22uf jantzen caps)
2x5uf capacitors in speakers (ordered 2 x 4.7uf + 2 x .22uf jantzen caps)
2x12uf NPE caps
4 x 8uf capacitors in speakers (ordered 4 x 1uf + 4 x 6.8uf jantzen caps)
6 x 40uf capacitors in speakers (6 x 33uf NPE+ 6 x 6.8uf NPE)
2 x 22 watt 2.5 ohm resistors in speakers, ordered 2 x 10 watt 2.5 ohm wire wound resistors (22 watts was unnecessary per an AV guru electrical engineer friend)
2 x 22 watt 1.5 ohm resistors in speakers, ordered 2 x 10 watt 1.5 ohm wire wound resistors (22 watts was unnecessary per an AV guru electrical engineer friend)

AR98LS Crossover Original AR98LSi Crossover Updates

Crossover Parts Hope not Needed - $410

Ordered
Resistors in 12 watt…
Mills 0.5 Ohm 12W Non-Inductive Resistor 005-.5 $4.25 2 $8.50
Mills 1.5 Ohm 12W Non-Inductive Resistor 005-1.5 $4.25 2 $8.50
Need 1.5 ohm and 2.5 ohm 2 of each WTF
Ordered them cost $15 Crap

Rebuilding the Drivers

DO YOURSELF A FAVOR - Just buy the foams from Simply Speakers I'm not convinced I had the absolute correct parts.
Specifically this kit will get everything you need PLUS you get an extra 12“ woofer set….. Acoustic Research AR9 COMPLETE System Speaker Repair Kit FSK-AR9C
eBay Speaker Refoam kit both mids and woofers
AR98LS Speaker Foam Surround Repair Kit / AR 98LS Woofer Refoam Kit
Item# 380439271300 $37.81 USD 1 $37.81 USD

  1. Removal from cabinets
    Remove screws, mark wire colors on the drivers and disconnect wires. Preserve gaskets when possible.
  2. Removing the old suspension from the speaker cone and frames
    Carefully remove as much of the old foam as possible with fingers. The more thorough/careful you are the easier it is to clean up in the next step
  3. Cleaning the speaker cones and frames
    Use a sharp scraper on the frames, do not remove the Masonite ring the total *linear* travel of the woofer cone is designed to be 12.5 mm or 1/2-inch removal of the masonite ring would be bad.
    Lacquer Thinner and a green Scotch-Brite pad works wonders on the frame if needed.
    CAREFULLY - A dry Scotch-Bright pad also works quite well to remove the deteriorated foam from the cones, do not tear or damage the cones.
  4. Replacing the suspensions
    Center the suspension correctly over/under the cones. The 8” mid-ranges have the suspension under the paper cone.
    • Align and Glue suspensions to cones
      1. Using a battery to lift cone for glue application (mids)
      You can prop the cone with blocks or I use an AA, C or D cell to lift the cone up. Reverse the polarity of the battery one direction pulls cone down, the other pushes it out.
  5. Center the voice coils and glue suspension to frame
    1. Using a battery to lift cone for glue application to the frame
    You can prop the cone with blocks or I use an AA, C or D cell to lift the cone up. Reverse the polarity of the battery one direction pulls cone down, the other pushes it out.
    2. Centering the voice coil. I use a Tone Generator through a Lepai LP-2020A T Amp to gently (very little power) play a 10hz tone which moves the cone up and down vibrating the suspension into center alignment naturally and offers the added benefit of audible feedback (scraping or rattling) if the voice coil is rubbing on the magnet assembly as you press the glue surfaces into place. Vary the frequency higher/lower to test for problems in alignment throughout the frequency spectrum. I then use clothes pins to clamp for a minimum of 4 hours or overnight.

Question or Have Unknown Driver Polarity?

Like me you did not mark the first drivers you removed? A battery can assist in identifying the positive and negative connections on a driver. Connecting a AA battery to the speaker terminals, connect a 2 color wire set to the speaker terminals note which wire is to what terminal on the speaker, once you have connected the wires to your speaker, proceed to briefly touch the ends of the wire to the battery terminals. NOTE: In some cases, extended contact with the battery can result in blown speakers! If the speaker moves OUT when the battery is connected, the + connected terminal is the + on the speaker… deduce the rest.

Cabinet and Covers

  1. Sand as much of the scratches out as possible not going to deep as to damage the veneer
  2. Clean all dust/particles
  3. Apply 4 coats of Tru-Oil on them buffing between coats with a green ScotchBrite pad

Damit. Cabs are looking really good but no before after pics. Bad me.

Speaker Gasketing Tape 1/8“ x 1/2” x 50 ft. Roll 260-542 $9.25 1 $9.25
Speaker Grill Cloth Brown Yard 70“ Wide 260-339 $7.55 2 $15.10
Heavy Duty Grill Guides 12 Pair 260-367 $3.59 1 $3.59
Small Grill Guides 12 Pair 260-368 $3.59 1 $3.59

Other Pictures

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