I am in possession of a pair of these salvaged from an old Newbie repair project ( replacing the low tweeter in a cheap pair of rubbish 3-ways ) and they are still in good condition.
http://support.radioshack.com/support_audio/doc40/40982.htm
Any body have any direct XO experience with these and if so how low is the best compromise?
The supplied capacitor being 10uF and factory Fs being 600Hz i was thinking of starting to play with a second order around 1500, not my favourite XO frequency but this will be another pair of garage speakers so performance isn't critical
http://support.radioshack.com/support_audio/doc40/40982.htm
Any body have any direct XO experience with these and if so how low is the best compromise?
The supplied capacitor being 10uF and factory Fs being 600Hz i was thinking of starting to play with a second order around 1500, not my favourite XO frequency but this will be another pair of garage speakers so performance isn't critical
I remember those!!! Had a pair "mounted" in the dash of my ol' 70 Mustang upright...the material coating the dome was very "sticky" & would gather anything that would touch it!
Read the power rating is 70 Watts "peak program".....that is the old style power rating, the actual RMS rating being about half.
Remember the "twice Fs" rule of thumb, your 1500 Hz with second order is right about spot on. If I recall the Efficiency was 89 Db@1W@1M.
______________________________________________________Rick..........
Read the power rating is 70 Watts "peak program".....that is the old style power rating, the actual RMS rating being about half.
Remember the "twice Fs" rule of thumb, your 1500 Hz with second order is right about spot on. If I recall the Efficiency was 89 Db@1W@1M.
______________________________________________________Rick..........
Looks like i'll have enough "Scrounge' parts then to get these up and running. local people know I build speakers and I often wake up to find stuff dumped on my front yard.
So I have a box here with blown tweeters but a working woofer, XO in this old Akai box is a single 2.2uF cap on a cone tweeter, I'm sure it didn't come from Japan like that as the woofer is an 8inch Dai-1Chi
So I have a box here with blown tweeters but a working woofer, XO in this old Akai box is a single 2.2uF cap on a cone tweeter, I'm sure it didn't come from Japan like that as the woofer is an 8inch Dai-1Chi
If you are going to interest me here, Moondog55, you're going to have to post some photographs and at least a DC resistance measurement. Also some estimate of what speaker these Radio Shack 40-1281A (2"?) midrange domes came out of. 
What I can tell you is these sort of domes were used by Acoustic Research in the AR-3A. It's really quite remarkable how well the filter and drivers worked together with an almost classic bell shaped profile on the midrange. I have slightly modified the AR filter for a crossover around 1.5kHz here. Despite the simplicity of the filter, response and phase is very good, and surprisingly my very rough sim with modern drivers (10" bass, 2" mid and 1" tweeter) gives no lobing above and below axis.
The strength of the lowish 1500Hz crossover is you avoid a lot of the bass cone breakup region. The 16 ohm wirewound level attenuators were an essential part of the sound, but I don't see why you couldn't use a cone tweeter.
What I can tell you is these sort of domes were used by Acoustic Research in the AR-3A. It's really quite remarkable how well the filter and drivers worked together with an almost classic bell shaped profile on the midrange. I have slightly modified the AR filter for a crossover around 1.5kHz here. Despite the simplicity of the filter, response and phase is very good, and surprisingly my very rough sim with modern drivers (10" bass, 2" mid and 1" tweeter) gives no lobing above and below axis.
The strength of the lowish 1500Hz crossover is you avoid a lot of the bass cone breakup region. The 16 ohm wirewound level attenuators were an essential part of the sound, but I don't see why you couldn't use a cone tweeter.
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They came out of the discards bin at Tandy when they had their great big "Going into business with Woolworths" sale about 20 years ago
Part of their DIY line. Actually a reasonable looking bit of old kit, they even came with a wired on 10uF cap in line, but nothing like the high quality AR dome.
Rated 15 watts nominal program with the supplied cap, but by using a decent ( even a book ) second order XO I can probably safely cross these at 1500 and still carry as much power as the cheap 8inch woofers in the box
I'd use cone if I had a working one, but I have a spare cheapie dome.
DCR is 7.9~ faceplate is 112*112mm
Part of their DIY line. Actually a reasonable looking bit of old kit, they even came with a wired on 10uF cap in line, but nothing like the high quality AR dome.
Rated 15 watts nominal program with the supplied cap, but by using a decent ( even a book ) second order XO I can probably safely cross these at 1500 and still carry as much power as the cheap 8inch woofers in the box
I'd use cone if I had a working one, but I have a spare cheapie dome.
DCR is 7.9~ faceplate is 112*112mm
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Wasn't that the truth. Not a bad driver otherwise but having to cross so high eliminated it from many designs. Well suited for a 4 way.
Dried out over 20 years, covered in cat hair and fluff too, does cat hair improve the response?
They are much better than the usual 3inch cone tweeter of the 60s and 70s which is what it replaced.
Has any-one ever tried improving one of these by drilling the pole piece out and adding damping? Looks like it would be possible
They are much better than the usual 3inch cone tweeter of the 60s and 70s which is what it replaced.
Has any-one ever tried improving one of these by drilling the pole piece out and adding damping? Looks like it would be possible
Rear chamber is 30mm across and 6mm deep, sides look to be 45 degrees, and I have no idea what the fibre pad is made from but it could be fibreglass.
Should I play or not, it is very tempting but I would have to drive 140 klicks to have these demagnetized before drilling and then the same again to have them charged up again. Same goes for adding ferrofluid but I can't find any suppliers in OZ and Amazon want $36 plus $9- for shipping and I imagine I need about a half gram or less in each VC gap. I am tempted to use a small felt pad in there tho, I have some (Somewhere) I used for tweeter mods a while ago
Should I play or not, it is very tempting but I would have to drive 140 klicks to have these demagnetized before drilling and then the same again to have them charged up again. Same goes for adding ferrofluid but I can't find any suppliers in OZ and Amazon want $36 plus $9- for shipping and I imagine I need about a half gram or less in each VC gap. I am tempted to use a small felt pad in there tho, I have some (Somewhere) I used for tweeter mods a while ago
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I just found and read an old thread with some posts by MarkMcK and 5th Element on tweeter mod's that seem relevant to my query.
http://www.diyaudio.com/forums/multi-way/52689-tweeter-modification-3.html
Mark said that the only real issue is the diameter of the vent hole and that it should be as large as possible.
Thoughts ??
Also unlike some more expensive tweeters and/or domes there is no gasket between the various parts of these, is there any argument in favour of a paper gasket Vs a thin layer of aviation gasket goo?? I have some so would it be a useful trick?
http://www.diyaudio.com/forums/multi-way/52689-tweeter-modification-3.html
Mark said that the only real issue is the diameter of the vent hole and that it should be as large as possible.
Thoughts ??
Also unlike some more expensive tweeters and/or domes there is no gasket between the various parts of these, is there any argument in favour of a paper gasket Vs a thin layer of aviation gasket goo?? I have some so would it be a useful trick?
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Decision made to use them "as-is" but can I have some suggestions as to value of the coil I should use to cross these at 1500Hz and a first order at 4k.
I choose 4k as the undamped response goes to 8k
So use approximate/ probable values or use a Zobel to correct the rise?
Perfection isn't the aim here, merely something acceptable.
I am going to use an old Japanese plywood box too, no point in buying material for this project and I am still debating which 8 inch to use, if I use the Coral woofer I may also put a cap in front to limit LF and add a sub at a later date. The Dai-1chi woofer needs lots of work as the top end is ragged and the others are not efficient enough to keep up with the mid and tweeter.
I choose 4k as the undamped response goes to 8k
So use approximate/ probable values or use a Zobel to correct the rise?
Perfection isn't the aim here, merely something acceptable.
I am going to use an old Japanese plywood box too, no point in buying material for this project and I am still debating which 8 inch to use, if I use the Coral woofer I may also put a cap in front to limit LF and add a sub at a later date. The Dai-1chi woofer needs lots of work as the top end is ragged and the others are not efficient enough to keep up with the mid and tweeter.
Regarding your drilling polepiece idea- im unsure why u need to demag beforehand. Perhaps im a caveman, but i managed to drill a hole in the polepiece of some cheapo domes i bought from maplin. I used masking tape over the gap to keep swarf out, and tack to remove any from the vent hole. Using the centre punch to mark the hole wouldve been easier if i had demagged them, but it seemed like alot of trouble for cheapo domes. Im still perusing the more generic 'dome, vc and plastic plate' type, replacement assemblies, since the originals are pretty rough.
I love these old revamp threads tho, im not sure we got these mid domes in Radio shack (Tandy in UK i think). The stores seem to be extinct now Pity. There was some small Jamo speakers with a louvred horn tweeter that i always wanted to rip apart, just to salvage said tweeters!
Good luck with the project!
Going to trawl epay in search of the cheapo jamos
Pity. There was some small Jamo speakers with a louvred horn tweeter that i always wanted to rip apart, just to salvage said tweeters!Good luck with the project!
Going to trawl epay in search of the cheapo jamos
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