Thought I'd document some really rudimentary stuff here in case it helps other beginning modders, and maybe provide a little general entertainment value.
I've got lots of plans for the Polks I've long owned or recently acquired but first needed to start getting experience working with some of the materials used in basic modding. Let's just say there's a reason I don't try to make a living working with my hands. I hit on a good little project this weekend, entry-level and low-risk, and have had an overall positive outcome while learning a lot.
No Polks were at any risk of harm in this production.
A couple months ago my son picked up a small guitar amp that had been left out on the street for the taking or trash, very beat up - cone torn, tweed front gone, etc. Apparently I suck at taking "before" photos but honestly I can't say it was insane that it nearly ended up in a landfill. Here it is after some dissection:
Turns out the thing is a circa 1966 Teisco Checkmate 14, solid state with what is labeled as a 21-watt amp although the limited info available on the Internet indicates it should be 14 watts. I've learned that tube Teiscos are collectable and there'd likely be some barely non-zero dollar value in this SS piece if it were in good shape, but it's far from that. So it's a great platform for me to work on - certainly vintage (I now know what nearly 50-year-old particle board is like to work with ...) and while if there were a Club Teisco forum bad karma undoubtedly would be flying my way for me saying it, it wouldn't really be the end of the world if I were to accidentally visit fatal misfortune upon this amp.
Anyway, a week or two after my son got the amp I was rummaging in the attic and happened upon the 8" 2-way Panasonic car speakers from my car 30 years ago. A few days later I realized that was the same size as the amp driver, and when I checked it out with my son it dropped in perfectly, four screws and that's that. Not sure what the impedance of the old driver was and the replacement is 4 ohm but at least in initial testing, nothing spontaneously combusted - we have a functional amp, even if some things need work. And it's not designed to be an airtight cabinet nor are we talking hi-fi here so even if the replacement speaker specs are all wrong, for a practice amp I don't much care.
So this weekend I did the following:
- removed the Panasonic speaker and applied Dynamat Extreme to the frame (liberally, figuring there's reportedly no potential harm from overkill other than maybe a few pennies and minutes wasted).
- I also applied Armaflex even though the cabinet is not sealed and thus I'm thinking a gasket probably doesn't buy me anything - just wanted to work with Armaflex a little (which was good as frankly I didn't do a terribly neat job with it in this first try).
- Loctite and JB Weld or equivalent are still on my shopping list so no practice with those steps at this stage
- sanded the front of the front panel to try to remove as much of the grill cloth glue and other crap as possible, then cleaned the panel front and back (brush, then vacuum, then a swipe with a tack cloth). Decided to reverse the sides as what had been the back doesn't have glue remnants on it.
- sprayed polyurethane on (what now will be) the back of the front panel, with multiple coats around the speaker opening and screw holes. For future reference I am thinking brushed-on poly might be better - is that right?
- when the poly dried I turned the panel over and spray-painted the (new) front flat black. Here it is drying:
HEY WAIT! Those are CRS+ frames in that photo - but I said no Polks could be harmed! -- Don't worry, I didn't plug in the soldering gun ...
I'm just replacing the CRS+ grill cloths, the originals of which unfortunately were not fit for presentation in my family room. The speakers themselves stayed safely in my family room (where, btw, I recently hooked them up to my newly repaired common-ground receiver, thereby officially joining the SDA club - me likey ...)
Anyway, back to the amp front panel, I attached the Armaflexed speaker using hurricane nuts. Very valuable experience here. I tightened the socket cap screw to pull in the nut and despite my polyurethaning efforts they quickly spun anyway ... will redo this at some point with a dab of glue to get them to hold.
- screwed front panel to (solid wood) cabinet frame. Did not bother with hurricane nuts for that. Here's the basic look (yes as a matter of fact I did crop rough edges out of this photo ...):
- as that tweeter frame extrudes a bit, I didn't want to simply glue grill cloth to the front panel as was originally done; there would be a bulge. So I built a frame out of some old wood I had lying around, spray-painted that black, then cut acoustic architectural grill cloth (from the eBay seller westmassguy recommends) and attached it using spray adhesive (which is fairly not fun to work with). I do not yet have this installed on the amp though as I need to get velcro or something to mount it.
- cut and attached grill cloth to the CRS+ frames, installed polkaudio badges and attached the grills to the speakers. My craftsmanship was far from perfect on the backs but installed I have to say they look sharp. I think I even may have scored a few WAF points but I'm not sure. Here's one next to a Monitor 7 with original cloth:
- hooked up the amp speaker, plugged in a guitar, turned it on and ... it still worked! And it looked OK too - better than it started out, anyway (I know, not exactly a high bar ...).
- it looks a tad worse for the wear today after I had to remove the front panel to remove the electronics, mainly to DeOxit the pots (this worked like a charm) and have a look/take pics.
But it works pretty well, has a decent tone to it. Tremolo does not work but that's not a show-stopper here. At tone settings that emphasize higher end there is a fairly faint but noticeable hissing/crackling sort of sound, which according to my internet research may indicate a bum resistor. To be continued some other time ....