HD8 refoam

[adam2434]

Picked up a pair of HD8 and need to refoam them.  

Thinking of using these:

http://www.ebay.com/itm/Boston-Acoustics-8-HD-8-HD8-HD-9-HD9-Woofer-Speaker-Foam-Repair-Kit-FSK-828-/130808153361?hash=item1e74c60511:m:mEtObaBkmlITsLwMj2o3Rrg

or 

http://www.ebay.com/itm/Boston-Acoustics-A60-A70-HD8-HD9-A400-BEST-Filleted-Foam-Surround-Repair-Kit-/172368150863?hash=item2821f1414f:m:mCvcRpHM7zQBHFg-8SlIbPA

Which would you choose?

Or, is there a better option?

My first refoam was on a pair of AR18s, and the resulting bass is pretty weak, so I am hoping to get the ideal foams for the HD8 to restore the bass to original performance.

Thanks,

Adam

 

 

 

[adam2434]

Have not ordered woofer surrounds yet, but pulled the woofers to start the prep work.

Surprised at how small the magnet is for an 8" woofer.  It's about the size of magnets I've seen on 4.5-5.5" midrange drivers.  Heck, I've seen bigger magnets on a couple tweeters.

Curious about the bass performance with such a small magnet, once new surrounds are installed...

 

 

[tvdantv]

I have used Simply Speakers kits for A60 sets and a small Infinity set.  They are very good.

If you are in Eastern PA and considering professional woofer work, Bill is fantastic:  http://www.millersound.net/index.html

[adam2434]

Thanks, tvdantv.

Simply Speakers does not recommend shimming the voice coil.  I shimmed the voice coil on my only other refoam job, so not doing it makes me a little nervous about centering the cone on the voice coil.

If I do shim the voice coil, not sure if the original screen dust caps can be removed without damage so that they can be reused.

This kit includes shims and screen dust caps, but they indicate that the foams may need to be trimmed to fit inside the recess in the frame.

http://www.ebay.com/itm/Boston-Acoustic-HD8-8-Woofer-Refoam-Kit-Speaker-Foam-w-Dust-Caps-/160391234508?hash=item25581003cc:m:mB80ruoxbDq48cr0JDaZpog

[adam2434]

I’ll keep updating this thread as a potential reference for folks doing future HD8 rehabs.

I went with the Simply Speakers foams linked above.

I was able to remove one dust cap without damaging it, but the other one tore.  I ordered the replacement screen/fabric dust caps in the link below.  They will be a hair bigger than the originals, assuming the stated dimensions are correct.  http://www.ebay.com/itm/182236113612?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The foams and dust caps, should arrive in the next few days, so I may get started over the weekend if time allows.

The voice coil gap is tighter than the gap in the AR18s 8” woofers I refoamed a couple months ago.  The plastic shims I used on the AR18s woofers were too thick, so I made some shims from some thick, shiny paper (cover from a calendar). 

The difference in voice coil gap on the same size woofer has me curious.  I’m sure the gap is a design parameter, but I’m not sure what else it interacts with.  For example, does a tighter gap for a given voice coil diameter and magnet size provide a more linear or more efficient response to the magnetic field?

Regarding the crossover caps, the crossover has a 4.7uF and 8.2uF electrolytic.  After I get the new foams installed and give them a listen, I may replace the caps with new electrolytics of the same values.  I think film caps will be too large for the terminal cup.

[adam2434]

Completed the HD8 refoam on Sat and listened to them a few times yesterday.

They definitely have a bright tonal balance vs. the majority of other bookshelf speakers I own or have owned - including NHT SB2/SB3, Def Tech SM65, Elac B6, AR18s, JBL Studio 530, Polk S15, Sony Core, and a couple others I briefly tested.  The only other model that I recall being as bright (and maybe a little brighter) is the Klipsch RB81 II that I owned for a while.

This is the first Boston speaker I've owned.  Are they generally on the bright side, or does it vary by series/generation?

[AR surround]

Adam,

I own pairs of Boston Acoustics A70's, A60's and A40's.   I have never found any of them to be on the bright side and have used each of these pairs at one time or another in a surround system with AR90's and/or AR9's.   However, I have never listened to an HD8.

[adam2434]

Does anyone have an idea whether the the 4.7uF and 8.2uF electrolytic caps are are tweeter or woofer circuits.

I'm thinking of replacing the capacitors and I "think" I could fit a film cap in the 4.7uf spot, but would only do that if the 4.7uf is in the tweeter circuit.

If the 4.7uf is in the woofer circuit, I'll just go with electrolytics for both.

 

 

 

 

 

[adam2434]

Recapped the HD8’s last weekend.  Used 4.7uF and 8.0uF Parts Express electrolytics. 

http:// http://www.parts-express.com/80uf-100v-electrolytic-non-polarized-crossover-capacitor--027-338?utm_source=google&utm_medium=cpc&utm_campaign=pla

The original caps were 4.7uF and 8.2uF, but I figured the Parts Express 8.0uF with +/- 10% tolerance was close enough.

Recapping these speakers was very easy.  The drivers did not need to be disconnected and there was enough wire slack to allow the work to be done with the crossover resting on the back of the cabinet.

I listened to them a little while after replacing the caps, and I can’t say that I noticed any differences in sound quality vs. the original caps.  I honestly did not expect to hear a significant difference.  I did this recap for “refresh” purposes and to increase my recapping experience.

The new caps (black) are bit smaller than the old caps (red).

Here are a couple crappy pics.