Well... for what it's worth...

ambrandt420

New Member
Mine has become kind of a mix of stuff (someday soon, replace the tuner... or just a super thorough deoxing might help it along with a good antenna, otherwise one of those Sony XDR's look interesting), but here it is:
(I apologize for the pics... taken at 2AM with no decent lighting, so the autofocus wouldn't lock exactly where I wanted it, and not enough patience right now to try again using manual focus)
First pic: Technics ST-S78 tuner, Technics SU-V78 reciever
Second pic: Technics SH-8017 equalizer, Kenwood KX-W8010 tape deck (tape deck=eBay item)
Third pic: Technics SL-1500 turntable with Stanton 681EEE cartridge & needle (eBay item)... and the 45's snuck into the picture, too
Fourth pic: Technics SB-2845 speaker (have the pair, naturally... though the other one lacks the dent in the tweeters dustcap... I should find some creative way to pop that out someday)

To date, I've had to mod the receiver twice... once to replace the power switch (which had long since failed... was held in the 'On' position with a thick Fender guitar pick, but the contacts much have corroded away to nothing) with a piece of my single-strand speaker wire to bridge it, then the second to supply external power to the fan to get it to run after the fan controller died (fan stopped working totally and the amp started getting very hot and the area around the amp developed that hot circuit board smell). The whole rig is powered from a power strip, so the switch part isn't an issue.
Speakers are wired to the amp with 22-gauge single strand wire from Radio Shack.
For being so old and decrepit, this beast can sing pretty darn loud (with bass-heavy material, and the Super Bass switch on and the bass knob in the middle, I can redline the display at about 3 on the volume knob, and with more regular material, anything past about 4 1/2 is simply crazy (getting ear-level with the midrange speaker is almost suicidally loud).
 

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Speakers are wired to the amp with 22-gauge single strand wire from Radio Shack.

That 22 gauge wire you're using is too small. The series impedance of such thin wire is probably "strangling" the music. 22 gauge is typically used for telephone inside wiring, alarm systems, etc. Get at least 18, 16 or 14 gauge speaker wire. Also, get those 45s cleaned up and placed in some jackets, instead of sitting out in the open collecting dust. Your stylus will thank you.
 
Oops... should've mentioned that *I think* it's 22 gauge wire... no markings on the insulation, so I just grabbed a wire stripper, held it closed and tried sticking the wire through the holes... didn't fit through 24, just fit through 22. Also, the left speaker wire is about 4ft with slack, and the right wire is about 2.5-3ft with plenty of slack... could that also make a difference (send slightly more power to one speaker)?
Any decently priced sources for solid strand wire (a quick search didn't turn up very much at all) that you guys recommend?
One other question that is probably self answering... when listening to music (even CDs), is it normal to not be able to hear anything out of the tweeter itself (maybe it is pumping some sound and it's just being overpowered by the midrange and woofer)... the sticker says that the crossover points are 3000Hz and 6000Hz, with 200W of output power (redline on the amp is 110W)... should the tweeter be screaming into my cranium with my ear in front of it? I've never checked the internal wiring, so maybe it's just a loose wire... might be worth a weekend investigation.
Was bought NIB for about $750... I looked at the old receipt from 1988 (still have it).
 
Oops... should've mentioned that *I think* it's 22 gauge wire... no markings on the insulation, so I just grabbed a wire stripper, held it closed and tried sticking the wire through the holes... didn't fit through 24, just fit through 22.
Then its 22 gauge.
Also, the left speaker wire is about 4ft with slack, and the right wire is about 2.5-3ft with plenty of slack... could that also make a difference (send slightly more power to one speaker)?
No, the differences in length are way too small to make any audible difference whatsoever.
Any decently priced sources for solid strand wire (a quick search didn't turn up very much at all) that you guys recommend?
Local sources are Radio Shack, Lowe’s, Home Depot. Mail order, try Parts Express. http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=374
One other question that is probably self answering... when listening to music (even CDs), is it normal to not be able to hear anything out of the tweeter itself (maybe it is pumping some sound and it's just being overpowered by the midrange and woofer)... the sticker says that the crossover points are 3000Hz and 6000Hz, with 200W of output power (redline on the amp is 110W)... should the tweeter be screaming into my cranium with my ear in front of it?
You probably have blown tweeters. If you crank up the volume so much that it drives the amplifier to clipping, that can burn out your tweeter voice coils. You did talk above about how you "redline" the output display and that "getting ear-level with the midrange speaker is almost suicidally loud". You probably don’t want to have your music “screaming into your cranium with your ear in front of it” either, or you risk permanent hearing impairment.
 
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Hmm... that's a possibility with the tweeters... might investigate that sometime... pull the midrange and woofer (or at least enough to disconnect the wires) out and leave the tweeter hooked up... theoretically, the crossover should still send signal to the tweeter... if so, then that would confirm whether they are blown or not.
If so, then I might have some work to do to replace them... should turn into a fun search (can't mod the cabinets too much, what with lack of tools or a garage with power and a workbench, and don't want to end up with some super-nice ribbon tweeters and the plain old midrange and woofer), though I know experimentation is where really nice gear starts from.
 
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Only one thing... I don't think the amp was clipping when I redline it like I said... the woofer wasn't hitting the basket and both weren't anywhere close to distorted.

Okay... as I understand the label, the tweeter's crossover frequency is 6000Hz (midrange is 3000Hz)... and with the midrange and woofer unhooked, absolutely nothing out of the tweeter (playing an older Abba tape... would expect something to be in the 6000Hz-20,000Hz range, even just tape hiss. Same with a CD (Nelly Furtado's Whoa, Nelly).
Turns out the crossover is mounted to the back of the speaker wire connector.
And, turns out the magnets are smaller than I ever thought they were... except for the tweeter (magnet is almost as big as the cone).
Attached are images of the tweeter from the right speaker... it's 3" and square (cone is 2 5/32") and the tweeter speaker is held in place by the waveguide.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120689422170 <-- looks almost identical
How much of a match would it have to be, or could I just chuck any old tweeter I find laying around in there and have it work, or would I have to know how much power is going to the tweeter itself so I don't get a lower-power tweeter and blow it the first time I play something through it because the crossover is sending twice it's rated power to it? I don't have a voltmeter, so I don't have a clue what wattage is going where (would think more to the woofer than the midrange and more to the midrange than the tweeter... but numbers are anyone's guess).
 

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When I have some concern as to a tweeter's performance I never thought of disconnecting the other drivers, I just do some critical listening at moderate volume, with my ear close to the tweeter in question. Maybe turn the bass down & treble up on the amp, or you can hold a blanket over the other drivers to muffle the sound. If they sound okay and you do enjoy cranking them loud, the that's the next test, with you in your normal listening spot. If it sounds good, it is good, if it starts sounding bad- turn it down!

I don't know that I'd spend money on those speakers. If they have problems or you just want to upgrade I'd think your money would be better spent looking at different speakers. Although I've never owned any, Technics speakers aren't thought of that highly- which is not to say they didn't make some great speakers. Maybe if I had an extra pair of dome tweeters laying around I'd start wondering how they'd sound in there.

Do be careful with "Super Bass" switches- they do tend to pump out distortion, including high frequency harmonics of the bass that can fry tweeters.

As for the speaker wire I find single strand is a pain because it's so stiff. Speaker wire is one of the things I tend to be on the alert for when I go through a thrift store. When I see it I grab it and throw it in a box in the garage.

I've always liked Technics stuff ever since an affordable Technics receiver was my first "real" stereo. Always wanted a turntable like yours! I have one of the SL-5 linear trackers they came out with in 1979, and it still works!
 
...I just do some critical listening at moderate volume, with my ear close to the tweeter in question. Maybe turn the bass down & treble up on the amp, ...

I have the equalizer in the smile arrangement, with the middle at zero and the upper and lower ends at the high position, treble all the way up at +5 and bass at 0 (treble and bass knobs on the amp, I mean).

If they sound okay and you do enjoy cranking them loud, the that's the next test, with you in your normal listening spot. If it sounds good, it is good, if it starts sounding bad- turn it down!

Honestly, you wouldn't know they weren't working unless you held your ear up to each tweeter... the midrange does a surprisingly good job of being a midrange... I know it's hard to pick out specific frequencies from an audio source and identify them, but 6000-20000 Hz is enough of a spread that it should be more noticeable than it is.

I don't know that I'd spend money on those speakers. If they have problems or you just want to upgrade I'd think your money would be better spent looking at different speakers. Although I've never owned any, Technics speakers aren't thought of that highly- which is not to say they didn't make some great speakers.

At only 3 on the volume knob (I would assume 30% of full power), with the right music, I can rattle the stairs in the hallway with zero distortion. If I push it to 3 1/2, the balcony railing (which is bolted to brick) rattles. Above 4 (with a little reduction on the bass knob), you can hear it about a block away. Any louder and you can barely get close enough to the receiver to turn it down.


Do be careful with "Super Bass" switches- they do tend to pump out distortion, including high frequency harmonics of the bass that can fry tweeters.

I always kinda wondered if the switch did anything more than just increase the bass.

As for the speaker wire I find single strand is a pain because it's so stiff.

For my system, it seems to work great (though, lacking an oscilloscope, all I have to go on is how it sounds to me). The amp is situated closer to the right than the left speaker, and the whole thing is too heavy to really relocate, so stiffness isn't really an issue. Single strand (solid core) wire practically doubled the volume of the speaker (relative to the volume knob), and it sounds great, but I'm leaning towards Glen B's advice about thicker wire... it's possible that I could be actually overloading the wire with power. Maybe someday the wires will burst into flames or explode from the power (would be worth having a camcorder nearby to record that).

Aaron
 
So the tweeters definitely aren't doing anything? Sorry, I didn't understand if you had said that or were just wondering if they were okay.

Since you have the tweeter out if you're still wondering about them it shouldn't hurt to hook them right up to the speaker wire coming from the amp- but start with volume at zero, bass all the way down, everything on the equalizer below 6000 Hz all the way down. Then give it a little volume very slowly and carefully to see what they're doing without the midrange chiming in.

6000 Herz is quite a high note, the highest key on a piano is only 4186 Herz. Since an octave is a doubling of frequency, the tweeters are responsible for only the last octave and a half that you can possibly hear. (The last octave for me, since my ears don't really go above 12,000 Hz any more.)


"I always kinda wondered if the switch did anything more than just increase the bass."

Any time you turn up the bass on any amp, you are geometrically increasing what you are demanding of it. The distortion created tends to be higher frequency harmonics of the bass notes, which are really bad for tweeters. Lower power amps are a particular problem with this when people use the loudness button and bass knob to make it loud enough for them.

"Single strand (solid core) wire practically doubled the volume of the speaker (relative to the volume knob), and it sounds great, but I'm leaning towards Glen B's advice about thicker wire..."

Definitely I'd agree that I'd want some more substantial speaker wire.I was interested to read that you noticed that dramatic a difference between the stranded and solid wire- although the stranded wire thinner than 18 gauge is pretty wimpy stuff. 18 gauge is a minimum I'd use, the more power you're using, the thicker it should be. You may have to use special connectors to hook up wire that is thicker than 16 gauge.
 
So the tweeters definitely aren't doing anything? Sorry, I didn't understand if you had said that or were just wondering if they were okay.

Since you have the tweeter out if you're still wondering about them it shouldn't hurt to hook them right up to the speaker wire coming from the amp- but start with volume at zero, bass all the way down, everything on the equalizer below 6000 Hz all the way down. Then give it a little volume very slowly and carefully to see what they're doing without the midrange chiming in.

6000 Herz is quite a high note, the highest key on a piano is only 4186 Herz. Since an octave is a doubling of frequency, the tweeters are responsible for only the last octave and a half that you can possibly hear. (The last octave for me, since my ears don't really go above 12,000 Hz any more.)


"I always kinda wondered if the switch did anything more than just increase the bass."

Any time you turn up the bass on any amp, you are geometrically increasing what you are demanding of it. The distortion created tends to be higher frequency harmonics of the bass notes, which are really bad for tweeters. Lower power amps are a particular problem with this when people use the loudness button and bass knob to make it loud enough for them.

"Single strand (solid core) wire practically doubled the volume of the speaker (relative to the volume knob), and it sounds great, but I'm leaning towards Glen B's advice about thicker wire..."

Definitely I'd agree that I'd want some more substantial speaker wire.I was interested to read that you noticed that dramatic a difference between the stranded and solid wire- although the stranded wire thinner than 18 gauge is pretty wimpy stuff. 18 gauge is a minimum I'd use, the more power you're using, the thicker it should be. You may have to use special connectors to hook up wire that is thicker than 16 gauge.

Right about the tweeters... they don't do anything while hooked up through the crossover,
I can't double-check (don't have it anymore) the old stranded wire, but it must've been about 16-18 gauge wire... it sounded good, bass was a little on the weaker side, normal listening volume was about 2 1/2 or so... with the solid single strand 22-gauge wire on there, normal listening volume is about 1 1/2 or so (numbers are approx... depends on the material).
I'll try wiring the tweeters directly to the amp with the bass on both the amp and eq turned down and see if I get a squeak out of them... might wait until Friday (work all week except Friday).
My theory about the speaker wire is that the multi-strand wire... only a few wires directly touch the terminal and those few wires divide up the power they receive to the rest of the wires. Solid core wouldn't do that, resulting in a greater percentage of the power reaching the speaker without having to share X amount of power between 20 small strands (though the solid core wire might present a different resistance to the amp, it seems to handle it fine). Single strand works fine for my short runs (speakers about 3-4 feet apart, amp almost right next to the right speaker... left cable run is only like 3 feet or maybe a bit less).
 
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