p38arover

Yes, too many speakers! I have some JBLs I'm using as rear speakers on the 7.1 sound system on the TV. I oiled the AR-6s up last night. They do look good. The KEFs were bought many years ago (in the 70s, I think) and do lack in HF response in comparison with later speakers. I rarely sit down to listen to music these days so I don't need what I have in speakers nor amps (Harmon Kardon 630 Stereo Receiver, Pioneer A717 amp, Sony STR-DE697, Sony STR-DE525), turntables (APAN BFU121, Pioneer PL51 direct drive, Thorens TD125 with SME arm and V15), then there are the Sony MD and CD players and Harmon Kardon HK1000 cassette decks. I really need to sell instead of hoarding although I have a 7.1 sound on the TV as well as my hifi setup in the lounge room (separate systems).

I'm not so sure. Had the 10 ohm resistor and 24uF cap been of a different brand to the original, I'd agree. However, the cap had glue on it from where it had been stuck to an original AR woofer. Who would look around to find secondhand original components to change a set of speakers? They'd use off the shelf components (I would). Re the 10uF cap values, I don't believe the variation from 10uF is all that significant with respect to the sound. Ditto with the new 22uF cap vs the 24uF (err, 40uf?) cap especially considering the woofers aren't original spec. I really appreciate your comments. I hadn't seen ReggaeBen's thread so that made interesting reading. Thanks to you, too Ben. I'm pretty satisfied with what I now have but I will get some teak oil and give the cabinets a once over. Quite frankly, my speakers are in far better condition than others I've seen on here and I'm only using them in my garage workshop (like I am with my KEF Celestes). I feel I'm committing heresy! I think I mentioned earlier that my daughter is taking my Wharfedale 2180 bookshelf speakers (I bought those new in 1991/2) but I'll still have the Wharfedale Valdus 400 towers (got them from my late son in 2008) in the lounge room. Cheers Ron

Sorry about the delay in replying - the thread has been inaccessible to me for the past couple of days. BTW, I am no expert, just a bumbling ex-electronics tech. Yes, the Sprague cap is the big blue 10uF item. The small 24uF is Royalytic (a brand I'd never heard of). I tried a side by side comparison of the speakers, one with the Royalitic/resistor combo and the other with none with both music and with a sine wave source (from my HP oscillator) and I can't detect any difference between them Having said that, my hearing is rolling off at 9kHz. However, as I swept upward in frequency, there were odd sounds coming from both speakers, possibly at the crossover frequency (design value unknown). I'm yet to do a comparison of the speakers, one with the Royalitic and the other with the new in-spec 22uF cap. The speakers do sound better than when I started. I'm sure if I drove them hard, the front speaker cloth panels would buzz as they are warped and are not held tightly into the Velcro. Cheers Ron

Thanks for the link. I hadn't seen it before. Very interesting reading. I didn't test the caps with varying frequencies. The phase variation was interesting. However, prompted by your comments, I looked again at my scribbled notes and realised I'd made a transcription error. I typed the first set of figures then copied and pasted it for the second speaker, updating the measured values but missing the 24uF cap. It should have read 38uF. I'll edit my post above. Today, I went to the local electronics parts store and bought a 22uF 100v non-polarised (NP) crossover capacitor and a 22uF BiPolar (BP) cap. The latter looks just like a small PCB electrolytic and was 1/4 the price of the NP cap. When I got home I measured them with the same test equipment used earlier and got these results: 22uF NP 24.83uF ESR 0.23 ohms 1.0 Vloss 22uF BP 24.07uF ESR 0.48 ohms 1.6% Vloss I also went through drawers of capacitors of all types and measured them. All, except some very old caps were in-spec, usually high in capacitance, up to 20% high. The old caps were up to 100% higher. I tossed them out. The tester I use is a Mega328 LCR-T4 12846 LCD Digital Component Tester or a similar item So are the Royalitic 24uF caps in the AR-6 speakers really high in value? Without Carl's test rig, it's hard to be sure but replacing them isn't expensive. The question is, what is the effect of 40uF//10 ohm compared with 24uF//10 ohms? What is the purpose of the parallel RC network? As an aside, when I was taking the photo of the tweeter with a mirror, I put a torchlight inside the speaker box for illumination. When I finished I stuffed the box with sound deadening material and buttoned it all up. The next day I couldn't find my torch. I looked high and low in my workshops to no avail. Yesterday, I opened the speaker up to check the soldering on the nichrome wire (it's a pig to solder) and found the torch, dead flat, in the speaker. :)

Thanks for the heads up on the badges. I hadn't really looked at them and just assumed they were discoloured plastic. There was, as you noted, a bit of plastic stuck onto them. With a polish up on some 1200 wet or dry paper they look really good with a brushed satin finish I might need to spray them with clear lacquer or enamel. While I was in the speakers, I measured the caps and inductors. S/N 6024 Inductor #4 0.79mH 0.63 ohms Inductor #12 0.23mH 0.53 ohms 10uF cap 11.74uF ESR 0.12 ohms Vloss 1% 24uF cap 40uF ESR 0.44 ohms Vloss 5% 10 ohm resistor 10.13 ohms Rheostat 16.13 ohms S/N 6032 Inductor #4 0.87mH 0.56 ohms Inductor #12 0.23mH 0.46 ohms 10uF cap 11.47uF ESR 0.19 ohms Vloss 1.1% 24uF cap 40.4uF ESR 0.42 ohms Vloss 4.6% 10 ohm resistor 10.23 ohms Rheostat 16.23 ohms Maybe I should have subtracted the measuring lead resistance of 0.07 ohms from those ESR figures. I did from the other resistance measurements. Testing with music (DAB radio) tonight didn't show any differences between the speakers, one with the RC network, the other without. I'll test it tomorrow with an audio oscillator and my imperfect ears. Now the question of the 24uF caps arises. Both measured 40uF. I wonder if that's really a problem and whether I should replace them. Anyway, the badges before and after:

Thanks for the reply. I'll get the epoxy out! Re Deoxit, we can get here in Australia but, by heck, it ain't cheap! I have silicone dielectric grease and silicone spray. Re the nichrome wire, the way AR assembled the speaker makes it worse. putting it through the rheostat tag then wrapping it around the green wire before soldering makes it difficult to untwist. If I bought these speakers from the radio station, it's likely the woofers were replaced by a tech who worked there before (and later with) me. He was a long-time friend - we were in the same class at the radio technician training college 1965-1968. I can't ask as he passed away a couple of years back. He would have bought the replacements from an Australian components retailer. (The station did have some good gear, I also bought a no longer used Thorens TD125 and SME 3009 arm with a Shure V15 cartridge). I didn't get the second AR-6 reassembled last night. We had visitors in the late afternoon and, after he and I finished off a couple of bottles of shiraz, and lots of cheese, dip, and crackers, I didn't feel like going out to the workshop. I might take my very old KEF Celeste K2 bookshelf speakers off the shelf in the mechanical workshop and give them some TLC, too. (My lounge room speakers are Wharfedales) I do appreciate your taking the time to reply. Cheers, Ron

Yes, I'll try one without the resistor/cap. I've added a pic of the tweeter rear (taken with a mirror and then the image was flipped). I've disassembled the other speaker's rheostat and cleaned it up. There wasn't as much corrosion as the first. I've added pics so that others can see how to disassemble it. One can see the clip that holds it together. The wiper arm drops out so it can have the silver contacts burnished with an eraser. The obvious corrosion on the rivetted terminals doesn't seem to have leeched into the junction of the rivet and the terminal tag thank goodness.

I saw you made comments about the speaker cloth in an earlier post. Here's mine:

Thanks for the reply, ra.ra I'm not sure how long ago it was that I bought these speakers - over 20 years - possibly bought from a Pacific island radio station I worked at from 1990-1993, so they may been bought 25+ years ago. I don't recall from where I got them. The crossovers have the no. 4 and no. 12 coils and the speakers have the front wired tweeters. The capacitor is a Royalitic NP I guess the question is, would they sound better without the 10 ohm/24uF RC circuit? I assume it's there to roll off the high frequencies that may get through the crossover. As I've got them apart, it would be easy for me to modify one and compare them (either with a function generator signal source or with music) but they aren't in a great listening environment, they are in my small electronics workshop/ham shack. I have too many projects............

Further to the above, I put an analogue ohmmeter across the 16 ohm pot/rheostat and rotated the shaft from end to end. The circuit went open circuit at both ends and was a bit erratic along the rotation. So I pulled it apart (it's held together with a clip). The brass rivets at each end were black with, I suspected, oxidation. Checked with the ohmmeter, they were high resistance. As the pot wiper hit the ends of the track, it would ride up onto the black sections and go open circuit. I scraped them clean and burnished them with a bit of wet & dry grit paper. I polished them with an eraser and also polished the centre wiper area with the eraser. I also cleaned the track. Reassembled, it was flawless in rotation. Re the woofers, I suspect they have been replaced. Why? Because the soldering on their terminals was not good (actually, terrible) and also the 24uF capacitors have glue residue where they had been glued to the speakers but not these speakers. There's no trace of glue on these. Tested, the speakers once again have treble.

Perhaps four versions. Mine has a combo of type A and B, i.e., it has the 24uF capacitor and 10 ohm resistor across the woofer AND it has the 16ohm rheostat, not the 3 position switch. The serial nos. on my two are 006024 and 006032. However, there a re handwritten letters before the printed S/N, viz. ER or EG. They were built in the UK. The 10 ohm resistor in one of the speakers must have been rather warm, it's burnt the sound deadening material. My woofers don't have a square magnet. and they don't appear to have been changed (I bought the speakers secondhand many years ago). My speakers also have the narrow front lip mentioned earlier. Why did I open them up? I replaced my workshop amp (Harman Kardon Model 630 Stereo Receiver that my daughter has now taken) with a Sony STR-DE525 from my son (he'd discarded it as it had stopped working - I had to replace one of 15 volt power regulators). When I switched it on, and with both the electronics workshop AR6 speakers and the mechanical workshop KEF speakers being driven, I noticed the AR6 were severely lacking in treble. The 16 ohm rheostats in both had gone electrically open circuit. I pulled them apart and found that they just needed cleaning (a spring clip holds the wire-wound resistance element onto the casing). I came to this forum because I was looking for the circuit diagram of the speakers. Tonight I'll reassemble them and hope they are working properly again. Cheers Ron VK2OTC