Sorry in advance for the long post.
I recently picked up a vintage pair of Jennings Research towers. They are 2-1/2 ways with 8" woofers and Peerless tweeters. When I grabbed them one of the woofers had been replaced with an inappropriate driver. Thought it would be no big deal to find a suitable replacement in a pair.
Well, it proved impossible to find spec's or even manufacturer of driver. So, I took the remaining 3 "good" drivers to my local speaker repair place (the one everyone says knows what they're doing) to be tested so I could get some baseline parameters. They declined to run them, as they said the VC's are rubbing and it would be pointless. They did seem to play fine though when I tested the speakers with the weird RadioShack 8" full range driver in. The original drivers are paper coned, rubber surround, and 1" VC's. They feel very compliant to me.
So, now I can either shoot from the hip on replacing just the 2 lower drivers, or replace all 4 woofers. Not sure if I really want to get into re-doing the crossover. My goal was to refinish the cabinets and get them working for a nice little vintage living room system. Not looking for audiophile quality, just to work well. I don't have any measuring equipment. And, have only basic knowledge of speaker theory. I also don't want to spend very much money since I am a full time college student.
Here is the pertinent information…..
The boxes are 1.5 cubic feet inside (42 cu. ltr.) inside dimension. They are 11.5 inches square and 30 inches tall.
I've also attached a copy of the crossover schematic. It's pretty simple. All drivers are 8 ohm. Using online calculators I came up with the tweeter being crossed over on a 2nd order at 2500hz. The upper woofer also crossed at 2500hz on 1st order. And the lower woofer crossed over at 500 hz. as baffle step compensation. The speakers were originally rated at 75 watts max.
The tweeters are rumored to be Peerless KO10DT - 810665
Specs:
Freq Range: 1000-20,000 Hz
Fs: 980 Hz
Power Rating: 50 Watts
Impedance: 8 ohms
Re: 6.8 ohms
Sensitivity: 89 dB
Xmax: .5mm
Voice Coil Diameter: 1" (25mm)
Magnet Weight: 228g
I'm thinking about using these drivers.
GRS 8PR-8 8" Poly Cone Rubber Surround Woofer 292-428
Without any T/S parameters for the originals, I'm just going on the recommended sealed enclosure volume, the rated wattage, and frequency response. The price is right, especially if I just wanted to replace all 4. I did download UniBox and plugged the parameters in for my box size and from what little I know it looked like it could work? Hopefully without too much adjustment to the crossover. If I ordered 4, I could get the discount.
Any help is appreciated.
-Chris
I recently picked up a vintage pair of Jennings Research towers. They are 2-1/2 ways with 8" woofers and Peerless tweeters. When I grabbed them one of the woofers had been replaced with an inappropriate driver. Thought it would be no big deal to find a suitable replacement in a pair.
Well, it proved impossible to find spec's or even manufacturer of driver. So, I took the remaining 3 "good" drivers to my local speaker repair place (the one everyone says knows what they're doing) to be tested so I could get some baseline parameters. They declined to run them, as they said the VC's are rubbing and it would be pointless. They did seem to play fine though when I tested the speakers with the weird RadioShack 8" full range driver in. The original drivers are paper coned, rubber surround, and 1" VC's. They feel very compliant to me.
So, now I can either shoot from the hip on replacing just the 2 lower drivers, or replace all 4 woofers. Not sure if I really want to get into re-doing the crossover. My goal was to refinish the cabinets and get them working for a nice little vintage living room system. Not looking for audiophile quality, just to work well. I don't have any measuring equipment. And, have only basic knowledge of speaker theory. I also don't want to spend very much money since I am a full time college student.
Here is the pertinent information…..
The boxes are 1.5 cubic feet inside (42 cu. ltr.) inside dimension. They are 11.5 inches square and 30 inches tall.
I've also attached a copy of the crossover schematic. It's pretty simple. All drivers are 8 ohm. Using online calculators I came up with the tweeter being crossed over on a 2nd order at 2500hz. The upper woofer also crossed at 2500hz on 1st order. And the lower woofer crossed over at 500 hz. as baffle step compensation. The speakers were originally rated at 75 watts max.
The tweeters are rumored to be Peerless KO10DT - 810665
Specs:
Freq Range: 1000-20,000 Hz
Fs: 980 Hz
Power Rating: 50 Watts
Impedance: 8 ohms
Re: 6.8 ohms
Sensitivity: 89 dB
Xmax: .5mm
Voice Coil Diameter: 1" (25mm)
Magnet Weight: 228g
I'm thinking about using these drivers.
GRS 8PR-8 8" Poly Cone Rubber Surround Woofer 292-428
Without any T/S parameters for the originals, I'm just going on the recommended sealed enclosure volume, the rated wattage, and frequency response. The price is right, especially if I just wanted to replace all 4. I did download UniBox and plugged the parameters in for my box size and from what little I know it looked like it could work? Hopefully without too much adjustment to the crossover. If I ordered 4, I could get the discount.
Any help is appreciated.
-Chris
Attachments
I'd look for a driver with a lower Qts (.4-.6???, perhaps the Dayton), to avoid that hump.
Sim a few more to see if you can get a flatter response.
If you're happy with the midrange sound spend a bit more on the woofers.
Personally, with a box that small, I'd be inclined to make a new front baffle and replace the 8" drivers with 6" drivers, and vent the box... but that's a bit more work...
Sim a few more to see if you can get a flatter response.
If you're happy with the midrange sound spend a bit more on the woofers.
Personally, with a box that small, I'd be inclined to make a new front baffle and replace the 8" drivers with 6" drivers, and vent the box... but that's a bit more work...
No way that box is getting modified without destroying it. And I'm a cabinetmaker. Besides, I prefer the bass of acoustic suspension.
The Dayton DC200 models a lot smoother. But the recommended enclosure size is 2/3 of mine.
One thing that occurs to me, there may be a hump in the GRS drivers, But it doesn't look that bad. And I'm wondering if this UNIBOX doesn't account for Baffle Step loss? If not that hump may actually be occurring right below where the bass starts to drop off due to the narrow baffle?
The Dayton DC200 models a lot smoother. But the recommended enclosure size is 2/3 of mine.
One thing that occurs to me, there may be a hump in the GRS drivers, But it doesn't look that bad. And I'm wondering if this UNIBOX doesn't account for Baffle Step loss? If not that hump may actually be occurring right below where the bass starts to drop off due to the narrow baffle?
The hump doesn't look too bad, as you say, it won't cost you much to find out...
No, Unibox doesn't compensate for baffle step, which would probably be a quite a bit higher (Freq = 115/width in metres)
I don't mind a slight hump down low, but prefer it a bit lower, if too high it can muddy the sound
probably a bit expensive, but try modelling this one:
The Madisound Speaker Store
No, Unibox doesn't compensate for baffle step, which would probably be a quite a bit higher (Freq = 115/width in metres)
I don't mind a slight hump down low, but prefer it a bit lower, if too high it can muddy the sound
probably a bit expensive, but try modelling this one:
The Madisound Speaker Store
I think you are on the right track. I wouldn't spend a lot on the woofers without also replacing the KO10DT's and the crossover. The only thing I would look for is to make sure that whatever woofer you buy, it should be an 8 ohm nominal speaker because the crossover runs them in parallel at low frequencies. Those GRS's are just fine.
Study hard and always remember to feed those speakers good music !
Study hard and always remember to feed those speakers good music !
Wow, that is really cheap. Model looks a little better.
Sreten, do you have any experience with the MCM drivers? I'm always suspicious of super cheap generic stuff. At least with the Parts Express they have a reputation to uphold and I trust them to pick their budget import products well.
Sreten, do you have any experience with the MCM drivers? I'm always suspicious of super cheap generic stuff. At least with the Parts Express they have a reputation to uphold and I trust them to pick their budget import products well.
Attachments
Hi,
The magnet doesn't look that pathetic at all for 7(18) bucks.
http://www.mcmelectronics.com/content/ProductData/Spec Sheets/55-2971.pdf
The numbers and graph look excellent for a very budget driver.
I'd buy and use in the bottom of the 0.5 way, but also try at the top.
I'm in the UK, never tried them.
http://www.ebay.co.uk/itm/Peerless-...ound_Vision_Speaker_Parts&hash=item35acd48013
rgds, sreten.
ZaphAudio has tested MCM drivers and found some budget gems and some not so good.
An externally hosted image should be here but it was not working when we last tested it.
The magnet doesn't look that pathetic at all for 7(18) bucks.
http://www.mcmelectronics.com/content/ProductData/Spec Sheets/55-2971.pdf
The numbers and graph look excellent for a very budget driver.
I'd buy and use in the bottom of the 0.5 way, but also try at the top.
I'm in the UK, never tried them.
http://www.ebay.co.uk/itm/Peerless-...ound_Vision_Speaker_Parts&hash=item35acd48013
rgds, sreten.
ZaphAudio has tested MCM drivers and found some budget gems and some not so good.
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For comparison the GRS 8PR-8:
An externally hosted image should be here but it was not working when we last tested it.
Visually comparing it to some old Pioneer 8" woofers I have, the only difference is the MCM has a rear vent, hence its 20 W higher power rating. Spec wise, the Pioneer's measured specs [way different than was published by PE, RS] are very close to the MCM's, though it has a rubber Vs foam surround, so I'm inclined to accept its published specs as close enough if data is current.
The Pioneer woofer and its 'FR' variant, the late, lamented 'BOFU', were true budget gems and nice to know it appears that at least the woofer has survived ~intact, though wish it had the original's foam surround.
GM
The Pioneer woofer and its 'FR' variant, the late, lamented 'BOFU', were true budget gems and nice to know it appears that at least the woofer has survived ~intact, though wish it had the original's foam surround.
GM
OK, then, where is MCM's profit margin? They can build and ship a high quality driver all the way from China for 7 bucks ? You don't get something for nothing.
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Hi,
You tell me ... I never said it is high quality or you can trust the
specs, or QC, but IMO its a very high value driver, and is the best
value best budget spare / repair 8" by far I've come across on paper.
In my tentative opinion its likely the best cheap option you can
get, and over the years I've looked at lots of cheap 8" drivers.
rgds, sreten.
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