Hi, Does anybody know these speakers?
I'm looking at a peak 8CX- 50 but i suspect it is a Coral. (same model# and specs).
Does anyone know anything about them? Thanks
Colin
I'm looking at a peak 8CX- 50 but i suspect it is a Coral. (same model# and specs).
Does anyone know anything about them? Thanks
Colin
Coral OEM'd for a lot of other speaker brands, so it most probably is Coral if it looks exactly the same...
94db/1m/1W (100dB at shorter distance ~1/2m)
2uF cap for tweeter. Replace it with new polyprop if you can.
Highish Q.
http://www.h3.dion.ne.jp/~roktal/unit/8cx50.html
94db/1m/1W (100dB at shorter distance ~1/2m)
2uF cap for tweeter. Replace it with new polyprop if you can.
Highish Q.
http://www.h3.dion.ne.jp/~roktal/unit/8cx50.html
sunnycue said:
Hi Colin,
I too have a pair of the Peak 8CX50's and I'm building them a pair of Coral 8CX501 BR cabinets. Do you mind if I ask what you've done with yours?
Doug
PS I quickly knocked together a pair of OB's for them. Fantastic!
I had 4 of the 501s, two per back loaded horn enclosure - about 17 -18 inches footprint and 31 inches tall, Mouth was 10 X 17 inches.
Since these added to about 16 ohms imp. and I had two goodmans horn 15 ohm trebax horns I used the goodmans crossovers. I had some old dome tweeters which I put in series , one vertical and one facing forward. They sounded so immediate and impressive - effortless. The tweeters on top sounded better than the horn tweeters on the 501s, possibly due to lobing issues with speakers being side by side. The opening tracks of Dark side of the moon at any volume was scary. As were the alarm clocks!!! Not very scientific a setup but I want them back!!!!!!
These were the speakers I mentioned in an old thread to do with listening experiences. They were run off a Lynsley Hood 75 watt SS amp.
jamikl
Since these added to about 16 ohms imp. and I had two goodmans horn 15 ohm trebax horns I used the goodmans crossovers. I had some old dome tweeters which I put in series , one vertical and one facing forward. They sounded so immediate and impressive - effortless. The tweeters on top sounded better than the horn tweeters on the 501s, possibly due to lobing issues with speakers being side by side. The opening tracks of Dark side of the moon at any volume was scary. As were the alarm clocks!!! Not very scientific a setup but I want them back!!!!!!
These were the speakers I mentioned in an old thread to do with listening experiences. They were run off a Lynsley Hood 75 watt SS amp.
jamikl
Does anyone have the T-S parameters for these?.
GM posted a set (with a qualification) but I have not been able to reconcile my measurements with his.
Thanks
GM posted a set (with a qualification) but I have not been able to reconcile my measurements with his.
Thanks
rjb said:
Yes, it's a problem. Good T/S data for old Corals is rarer than rockinghorse poo. I think the only stuff I've seen is from GM, but it may be worth your while to e-mail Howard at eastmarinedrive.com
cheers,
Doug
Hi GM.
I'm not saying you are wrong, in facct just the reverse.
I'm measuring an 8CX unit using the system outlined in Rod Elliotts web page, which I have used successfully before, but am getting answers I don't trust.
Specifically
Qms 3.17
Qes 1.67
Qts 1.09
Vas 55.2 L
I have two possible problem areas.
The original cloth surround had gone hard, stiff and brittle so has been replaced with rubber. This has lowered the res.freq to 38 Hz. from your 40. The spider seems OK.
The sig gen is an old philips which I have just resurrected and may be off.
You commented your results were from reverse engineering, which I took to mean not from measuring an actual unit, so I was just looking to see if anyone had . Regards
Ross
I'm not saying you are wrong, in facct just the reverse.
I'm measuring an 8CX unit using the system outlined in Rod Elliotts web page, which I have used successfully before, but am getting answers I don't trust.
Specifically
Qms 3.17
Qes 1.67
Qts 1.09
Vas 55.2 L
I have two possible problem areas.
The original cloth surround had gone hard, stiff and brittle so has been replaced with rubber. This has lowered the res.freq to 38 Hz. from your 40. The spider seems OK.
The sig gen is an old philips which I have just resurrected and may be off.
You commented your results were from reverse engineering, which I took to mean not from measuring an actual unit, so I was just looking to see if anyone had . Regards
Ross
Greets!
Bummer, I was hoping you had more accurate ones that indicated a lower Qts since I fudged them on the high side to calc a too large a cab since it's easier to shrink one than stretch it.
Anyway, you're right, mine are a complete SWAG based on similar Corals and the two BRs designed for the 501, so could be pretty far off, though they would have to be in complementary ways to perform well in it. Note too that a Qts this high wouldn't have been put in a BR and the calc'd eff. is way low compared to the published specs, so something's amiss.
GM
Bummer, I was hoping you had more accurate ones that indicated a lower Qts since I fudged them on the high side to calc a too large a cab since it's easier to shrink one than stretch it.
Anyway, you're right, mine are a complete SWAG based on similar Corals and the two BRs designed for the 501, so could be pretty far off, though they would have to be in complementary ways to perform well in it. Note too that a Qts this high wouldn't have been put in a BR and the calc'd eff. is way low compared to the published specs, so something's amiss.
GM
I'm posting this for anyone that may be interested in the future.
I have four Coral 8CX, only one of which still has the tweeter. The surrounds have all gone hard and brittle, sufficently so to cause two of the cones to fatigue at the outer edge, with tangental cracks. Tested Fs in this state was of the order of 180Hz.
The spiders seem ok still.
On the principle I could not make matters worse, I replaced the surrounds of the two with cracked cones with new rubber, (not foam) surrounds and repaired the cracks as best I could. Then coated the whole cone with a light coat of PVA.
Using arta software and the added weight method, the following are the results of testing the best of the two units.
Fs 42.82
Re 6.9
Qes 0.53
Qms 2.63
Qts 0.44
mms 17.9 gm
Rms 1.746 kg/s
Cms 0.0000808 m/N
Vas 45.89 L
Sd 201.06 Cm2
Bl 7.76Tm
The second gave similar results, but because of the more extensive repair work the cone was slightly heavier and consequently Fs slightly lower, and other slight changes.
I have reasonable confidence in the above results being not dis-similar to a good condition unmodified unit. The manufacturer's specs claim a "moving mass" of 12gm, and an Fs of 40 Hz with a Qo (whatever that is) of 0.45, and recommend a BR cabinet of 68 litres.
I have four Coral 8CX, only one of which still has the tweeter. The surrounds have all gone hard and brittle, sufficently so to cause two of the cones to fatigue at the outer edge, with tangental cracks. Tested Fs in this state was of the order of 180Hz.
The spiders seem ok still.
On the principle I could not make matters worse, I replaced the surrounds of the two with cracked cones with new rubber, (not foam) surrounds and repaired the cracks as best I could. Then coated the whole cone with a light coat of PVA.
Using arta software and the added weight method, the following are the results of testing the best of the two units.
Fs 42.82
Re 6.9
Qes 0.53
Qms 2.63
Qts 0.44
mms 17.9 gm
Rms 1.746 kg/s
Cms 0.0000808 m/N
Vas 45.89 L
Sd 201.06 Cm2
Bl 7.76Tm
The second gave similar results, but because of the more extensive repair work the cone was slightly heavier and consequently Fs slightly lower, and other slight changes.
I have reasonable confidence in the above results being not dis-similar to a good condition unmodified unit. The manufacturer's specs claim a "moving mass" of 12gm, and an Fs of 40 Hz with a Qo (whatever that is) of 0.45, and recommend a BR cabinet of 68 litres.
Win ISD pro gives the following slightly different figures, (original test results in brackets)
fs 42.83 (42.82)
Qes 0.527 (0.53)
Qms 2.634 (0.63)
Qts 0.439 (0.44)
Vas 46.33 (45.89)
and calculate a BR cabinet size of 63.9 litres which is in line with manufacturers reccommendation of 68 litres less damping.
fs 42.83 (42.82)
Qes 0.527 (0.53)
Qms 2.634 (0.63)
Qts 0.439 (0.44)
Vas 46.33 (45.89)
and calculate a BR cabinet size of 63.9 litres which is in line with manufacturers reccommendation of 68 litres less damping.
Brisso57 said:
And due to aging, will have wandered from the original, Each pair is more likely to be different than the same.
dave
Yes Dave, as you say all units even of the same type age differently, particularly paper cones. I have four 8CX, three without tweeters, bought cheap so have been experimenting with them.
All four had widely different results.
The tweetered one had been over-driven at some stage, the "crossover"resistor badly burnt up. It also showed oddities in the impedance curve, so I dismantled it. Conventional design, except for what seems to be a slug magnet and associated W steel pole , rather than the normal tube type magnet with central steel pole. Normal paper former, and as far as I can tell, a two layer copper coil about 2 mm longer than the depth of pole-peice. So Xmax is quite short. The end of the coil former had hit something solid, and slightly squashed, lightly rubbing on the pole-piece, so this was sanded off and a very light coat of epoxy added. This now matches the others.
Overall, not particularly a well made unit under its impressive casting.
All the surrounds had gone hard, ( cloth plus some form of coating)so Fs were all above 150 Hz.
Due to this, two showed tangental cracks at the cone edge, one badly. These I repaired, and replaced all surrounds with off-the shelf rubber roll-edges. This dropped all back to near the T-S values I listed above, However the spead between the four was still wider than I expected, one in particular had a 10 Hz higher Fs.
I had treated two of the cones with PVA, and one of these was the problem. Some PVA had in my haste got on the surround, and once this was cleaned off, the Fs dropped to the common value.
I was surprised by the shift, as the PVA is quite flexible. Obviously the surround still has a significant effect, something I haven't seen on larger drivers.
These cones are very light, and quite soft and flexible. The possibly have absorbed moisture over the years. The impedance curve drops above about 4500 Hz on all four so obviously the cone fails mechanically there. When I get round to a frequency test I will post more.
I'm now going to clean all four surrounds, and sand lightly to see what happens to the T-S. I suspect Fs will drop slightly on all.
Coating the most damaged unit with several PVA coats on the front, has added mass, and the Fs is lower. So too is the impedance peak, but the other values have not shifted proportionally. Win ISD suggests cabinets close in size to three, the heavy cone one being the odd one out.
For the four units,at present Fs ranges from 36 to 42, (the two best units both close to 39.5), Qt 0.47 to .52, and Vas 47 to 51 L. ( with the heavy cone one being 57)
I will now do an open baffle frequence run on each.
With that done, I will treat two cones with an artists varnish and compare.
All four had widely different results.
The tweetered one had been over-driven at some stage, the "crossover"resistor badly burnt up. It also showed oddities in the impedance curve, so I dismantled it. Conventional design, except for what seems to be a slug magnet and associated W steel pole , rather than the normal tube type magnet with central steel pole. Normal paper former, and as far as I can tell, a two layer copper coil about 2 mm longer than the depth of pole-peice. So Xmax is quite short. The end of the coil former had hit something solid, and slightly squashed, lightly rubbing on the pole-piece, so this was sanded off and a very light coat of epoxy added. This now matches the others.
Overall, not particularly a well made unit under its impressive casting.
All the surrounds had gone hard, ( cloth plus some form of coating)so Fs were all above 150 Hz.
Due to this, two showed tangental cracks at the cone edge, one badly. These I repaired, and replaced all surrounds with off-the shelf rubber roll-edges. This dropped all back to near the T-S values I listed above, However the spead between the four was still wider than I expected, one in particular had a 10 Hz higher Fs.
I had treated two of the cones with PVA, and one of these was the problem. Some PVA had in my haste got on the surround, and once this was cleaned off, the Fs dropped to the common value.
I was surprised by the shift, as the PVA is quite flexible. Obviously the surround still has a significant effect, something I haven't seen on larger drivers.
These cones are very light, and quite soft and flexible. The possibly have absorbed moisture over the years. The impedance curve drops above about 4500 Hz on all four so obviously the cone fails mechanically there. When I get round to a frequency test I will post more.
I'm now going to clean all four surrounds, and sand lightly to see what happens to the T-S. I suspect Fs will drop slightly on all.
Coating the most damaged unit with several PVA coats on the front, has added mass, and the Fs is lower. So too is the impedance peak, but the other values have not shifted proportionally. Win ISD suggests cabinets close in size to three, the heavy cone one being the odd one out.
For the four units,at present Fs ranges from 36 to 42, (the two best units both close to 39.5), Qt 0.47 to .52, and Vas 47 to 51 L. ( with the heavy cone one being 57)
I will now do an open baffle frequence run on each.
With that done, I will treat two cones with an artists varnish and compare.
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