JKent
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Posts posted by JKent
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Beautiful! Do you have the matching tuner?
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Hey Lou
Glad you figured it out. I didn't mean to mislead. Here's a closeup, a little fuzzy, of what looks to me like a threaded hole in the heatsink. Did your rod go through a hole like that or was it between the fins?
Kent
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Hi Lou
Good to see you back. Nice find.
I had 2 of those back in 2008 or so. Kind of sorry I sold the "keeper" but you know--too much gear, too little room.
I looked at some old pics of the innerds and I'm quite sure the cabinet was attached with screws threaded into the heat sinks. My guess is the steel screws and aluminum sinks reacted over time (forget the technical term. Galvanic corrosion?) and the screws are virtually welded in there now. Maybe apply some heat and tap them? A little PB Blaster? Sorta reminds me of the Big Bang episode with the frozen lug nuts 😀
Good luck and be sure to post pictures of your restoration.
Kent
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Very sad news but thank you for letting his friends here know. He will be missed.
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Finished the grilles. Instead of making new frames I just ran strips of 1/8" Masonite around the perimeter. This not only allowed the board to clear the woofer gasket, it also strengthened it and gave enough thickness to staple the linen.
Linen is some Zweigart 28 count Cashel Raw Linen from Michael's that I had on hand. After attaching the cloth to the board I spritzed it with water and dried with a hair drier. Nice 'n' taut. Finished the grilles off with some Dynaco "d" badges from ebay seller audiotagsiowa. I didn't want to use the full dynaco name, since these aren't real dynacos.
Still lovin' the sound.
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"Dynaclones"
A friend gave me a pair of crappy no-name speakers with woofer rot but they have really nice walnut veneer cabinets (photo 1). So after considering building an E-wave I consulted RoyC, who suggested using the GRS Dynaco A25 replacement woofers and tweeters sold by PE. I've never owned or even heard Dynaco speakers so I thought why not?
The cabinet size is close: 12-7/8"w x 22-1/8h x 9-1/2d. The real 25s are 11-1/2"w x 19-3/4h x 9-7/8d.
The first challenge: My speakers were 3-way acoustic suspension type. So I had to close up one hole and make a port. Looking around the interweb I saw that the tweeter is close to the woofer and although most A25s have the aperiodic slot on the bottom, some have it on top (photo 2, from web). So I decided to put the new tweeter where the mid had been, close up the tweeter hole and cut a slot. I made a port out of pine and covered the back with crinoline to hold the stuffing in the port. Roy says the amount of compression of that stuffing affects the sound and will have to be "tuned". Added a front-to-back brace made from a scrap piece of closet pole. I found some metal grilles in my basement. Don't know what they were from but they fit the port nearly perfectly (Photo 3). Once the new configuration of the baffle was finished I filled and sanded, then coated it with some DuraTex I had on hand, also from PE (Photo 4). The round grilles over the tweeters are some $1.50 PE buyouts I had on hand. The mounting holes weren't perfect but a Forstner bit and some washers fixed that.
My timing was off for the crossovers. Some sold on ebay for a fair price a couple months ago. Oh well. So I built my own, using a schematic and photo on updatemydynaco.com as a reference (Photo 5). My local electronics store had a 2 pole 5-position switch. Only needed 1 pole. The other components are one 5uF cap, five 2.2 Ohm resistors and one 10 Ohm. I ordered the 2.2 Rs from Mouser, everything else I had on hand. The cap is 4.7uF so I played with "cascading"--something North Creek used to advocate. The 5th photo shows the xo. I don't know where I got the 4.7uF 400v cap. The green one is a 0.1uF Paper-in-Oil and the small one is a 0.47 poly. The bundle measures 4.95uF. Photo 6 shows the new label and crossover panel from the back. 5-way binding posts and aluminum knob were parts I had on hand.
The next step will be making new grilles. The cutout for the woofer in the old ones is a little too small and touches the gasket on the new woofer. I'll make new frames and cover them with light linen (another suggestion from Roy).
The resistors arrived about 6PM today but I had to rush to finish putting the speakers together 😄 First impression: I'm very happy with them. I haven't fiddled with the internal stuffing (poly from some AR-11s that were beyond repair) nor the stuffing in the port. I think I like the tweeter switch in the middle or "normal" position. Placement in my shop is far from ideal. BUT, these sound great to my ears. Clear and detailed are the first words that come to mind. They have some stiff competition in my workshop: AR-4x's, AR-91s and AR-3a's along with a couple of others that aren't hooked up. I'll post further impressions and photos of the new grilles when finished.
Kent
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I believe Andre is talking about stuffing so yes, Vilchur used fiberglass and Kloss used foam blocks.
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Isn’t that what they put in Rolls Royces?
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Thanks. Very helpful. I actually made my ports already and was very surprised to see how shallow they are in the drawung. Looks like just 3/4" or the thickness of the front baffle. I had originally planned to use a 4" round port but then made a rectangular one of wood but it's 2" deep. Thought that would be useful for experimenting with the amount of stuffing in the slot but the picture at the top of the linked page shows a rather thin piece of fg. Back to the drawing board?
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I recently acquired some speakers with very nice walnut cabinets but crappy drivers. My plan is to build some Dynaco A25 clones using the GRS replacement drivers from Parts Express.
Here's my question: What are the dimensions of the slotted aperiodic port? My clones will resemble the A25s pictured in this thread with the slot on top but I assume the dimensions were the same, top or bottom.
I’m primarily interested in the DEPTH of the port
TIA
Kent
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Here's a shot of the back with the new 5-way binding posts. I put them to the side because space is limited in the middle. The old hole is blanked off. The pic also shows my "custom interconnects." The originals had a flat color coded 4-conductor cable but that was missing. Fortunately I had just pulled a bunch of ~20" wires from a speaker (my next project--Dynaco clones). Trying to figure out how to tie them together I Googled "4-strand braid" and found lots of instructions. I had the crimp connectors and heat-shrink tubing on hand so these cables were virtually free. I like the look. Still need to paint the 4th screw head yellow.
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Got these recently--just the contour (crossover) boxes--not the speakers. One box cover looked just awful inside--all moldy. The guts of that box were a little dirty but not bad. Everything else was good but 2 knobs were missing. Wood veneer had some small chips and one gouge or dent.
First step was to scrape the mold off with a putty knife, then brush on pure bleach. Rinsed it off and dried with a hair dryer.
The gouge was steamed out. Wood was stripped using lacquer thinner, steel wool and paper towels. The chips were filled with a mixture of epoxy and walnut sanding dust. The cabinets aren't finished yet. Still have to decide whether to use lacquer or oil. Also have to get some yellow paint for 2 of the terminal screws.
This was odd: The instructions say "The terminals marked 'GND' and '8 Ohms' on the Contour Control's rear panel should be connected to the corresponding speaker terminals on your amplifier". Surprise! KLH used some spare FM Antenna terminals for this pair! So I decided to remove those, blank the hole with sheet aluminum and install 5-way binding posts. That's a first for me but I think it's an improvement.
All of the caps were replaced with ones I had on hand: Two 50uF NPEs, one 16uF Erse mylar, three 4uF Dayton polys and one no-name 3uF mylar. I used to replace all of the resistors but Roy advised me that the only truly undersized one is the 5 Ohm 5 watt in the woofer circuit so I replaced that with 2 10 Ohm 10 watt Rs for an effective 5 Ohm 20 watt.
Because of the two missing knobs I used some stove style knobs to replace them. I think they look right, with a vintage vibe but I just bought a single "parts donor" crossover with 4 knobs, so I can use originals and have 2 to spare.
I tested these two with some raw drivers just to make sure everything works.
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Here's the latest revision; Rev 7b as of March 2024. Please disregard the old revision (Rev 2) in the Library.
Thanks again to Gene for resizing this.
Kent
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Glenn is the expert on this, but I'll take a crack at it
- Before clamping, dig out as much crumbly/swollen stuff as you can.
- Sorry I don't remember what the finish is. I'd try wiping it with Lacquer thinner first. If that softens it, it's lacquer. If there are dents, where the fibers aren't torn up, you can steam them out with a damp cloth and an iron (even a soldering iron).
Good luck. Worthy speakers.
Kent
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9 hours ago, RoyC said:
I would be more inclined to investigate the driver PeteB (many credentials, btw) mentioned earlier in this thread
I was wondering why no one picked up on that. Pete has mentioned good subs for other drivers in the past and it looks to me like an adapter plate could be made, even without a 3D printer. Maybe I should add a couple to my next Mouser order. Anyone plan to investigate?
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Forget about stacked Advents. Your stack rocks!
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4 hours ago, tourmax said:
anything that even looks like it's only half worth going for a viewing is obscenely over priced. Like 1-2 grand for a set of advents that don't even have original drivers in them. Even stuff that's been poorly modified or needs serious work before it can be used is foolishly overpriced these days.
Are you serious? For phony Advents? Where do you live? It seems to me a lot of people are getting rid of speakers that are "too big." I recently got some very nice Snells for free. And a CSP member has some AR-9s listed in the FS section for $800 which sounds to me like a steal if you have room for them and happen to live in New England so you can pick them up.
But to your point: I doubt that I know any more about xo's than you do but it seems to me that, since your Polks are ported, you could simply splice into the tweeter wires, run long wires out through the port and attach L-Pads, then adjust them from your listening position until you find the setting that sounds right. Then solder in your fixed resistors.
Kent
PS: Looks like you posted while I was typing but I still think my suggestion would work if you want a reversible fix
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Nice work. Enjoy the music.
I remember commenting to my audio technician friend that it was my impression that all Canadian hi-fi was excellent. He said "well, not ALL...." He named a company but I've forgotten the name. Electro-something? He said it was an attempt by the gov't to re-train lumberjacks to build audio equipment. Apparently not high quality. Sounds like a Monty Python bit to me 😄
I've always lusted after Bryston gear but never took the plunge.
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Yeah, those 47s are definitely new. And 47 is close enough to 50. You'll notice in my re-do, some caps and some resistors are close but not exact values.
Speaking of which, it may be too late now but I always recommended replacing all of the 5w resistors with 10w. RoyC looked into this and identified just 1 or 2 that had to be replaced. I have to search my notes. One is the 5 ohm in the upper left corner in my pic. I'll try to get more info.
Kent
PS: OK. I think Roy said that 5 Ohm resistor in the woofer circuit should be 15 0r even 20 watts. There's a 15 Ohm in the mid circuit. I think it's the one in the middle of the board. That one's OK but could be bumped up to 10w. The other 5w resistors are fine.
PPS: OOOPS. We were typing at the same time.
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On 3/7/2024 at 4:00 PM, tourmax said:
IPA seems to soften things up nicely.
Yeah. Beer softens me up too 😄
On 3/7/2024 at 4:00 PM, tourmax said:The mesh dust cap is interesting. That's new one on me too.
Your 4x's have a mesh cap, essentially.
On 3/7/2024 at 4:00 PM, tourmax said:The veneer also looks very "thirsty, so I give "Howard's Restor-a-Finish" (neutral) a try:
That should clean it up nicely but if the wood is thirsty, Howard recommends following up with their Feed n Wax.
On 3/8/2024 at 11:52 AM, tourmax said:Used Aleene’s for the first time.
I use Aleene's on paper cones. Don't know how it will be on poly. I use that nasty nitrile based glue for plastic cones.
Looking forward to more posts. Not familiar with that brand but those seem very nice. I think in general Canadian speakers are quite good. I'm told the Canadian government helps speaker manufacturers with R&D. I'd say they were a great find and a good project.
Kent
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That's right. Is that your only double cap? Sometimes KLH used a double cap but both red leads went to the same point, so a single cap can be used instead.
Kent
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Welcome back "cousin" 😉
What a great find! (and great spouse!).
Not sure about the dust cap. How does the woofer do with a push test? If it springs back maybe try a little white glue around the cap. If it still springs back use some of Roy's goo on the surrounds.
Regarding the caps, I hope someone with more expertise chimes in but I don't see a problem. What are the implications for ESR? I dunno. I do know, from working on Snells, that Peter Snell was an advocate of "bundling" caps, so you're in good company.
Kent
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Simply Speakers sells that glue. Maybe contact them and ask.
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Take a look at this old thread
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AR4x replacement tweeter recomendations?
in Acoustic Research
Posted
This is a bit OT but it’s sort of relevant: I don’t know what happened to Gene’s post suggesting those tweets might be appropriate for MicroStatic supertweeter clones, but they’re exactly what I used. Had a pair of MicroStatics with fried tweets so I needed EIGHT replacements. These fit the holes perfectly but had to be glued in place. I think they’re fine.