Hi guys. Our Ross stage monitors need some TLC I think. one of them is making a resonating sound, as if you were trying to talk with a piece of paper over your lips. I think at least one tweeter is fried because a bit the VC and leads were black instead of shiny copper color.
They are 4 ohm drivers I believe now, which may or may no matter of they are being replaced. there is no crossover, but there is a cap: 2.2 microF 100V in series with one of the tweeter leads.
We don't play large gigs, so having "good enough" stage sound is all we are after.
If I were to replace the drivers and tweeters, what things should be considered?
Say for example, I were to use Eminence Delta 10A, 10" drivers with 350W rms power handling, what should the tweeter specs be, and what is this I am reading about in-series resistors? Can I just use a cap or is a XO mandatory ?
They are 4 ohm drivers I believe now, which may or may no matter of they are being replaced. there is no crossover, but there is a cap: 2.2 microF 100V in series with one of the tweeter leads.
We don't play large gigs, so having "good enough" stage sound is all we are after.
If I were to replace the drivers and tweeters, what things should be considered?
Say for example, I were to use Eminence Delta 10A, 10" drivers with 350W rms power handling, what should the tweeter specs be, and what is this I am reading about in-series resistors? Can I just use a cap or is a XO mandatory ?
I can't find any information on Ross 10" foldback wedges, so not quite sure what you have.
As a general rule just dropping drivers at random into cabinets can cause more trouble than it is worth (or, it might work fine).
A "resonating sound" may be due to the surround or spider coming adrift so I woudl start by a visual examination of the driver etc. to make sure the surround and spider are all intact and glued down.
The lack of crossover is curious (although technically the capacitor is a first order crossover) and may support some mentions I have seen of Ross stage wedges using Piezo tweeters.
in theory you would want something that delivered about 98dB at 1Watt 1 meter, and had similar coverage to the Delta (not specified) and since most compression drivers run at 104+dB 1W/1M most will probably work but would need to be padded down.
Fried tweeters are common in foldback speakers due to feedback, as it does not take much feedback to fry them.
As a general rule just dropping drivers at random into cabinets can cause more trouble than it is worth (or, it might work fine).
A "resonating sound" may be due to the surround or spider coming adrift so I woudl start by a visual examination of the driver etc. to make sure the surround and spider are all intact and glued down.
The lack of crossover is curious (although technically the capacitor is a first order crossover) and may support some mentions I have seen of Ross stage wedges using Piezo tweeters.
in theory you would want something that delivered about 98dB at 1Watt 1 meter, and had similar coverage to the Delta (not specified) and since most compression drivers run at 104+dB 1W/1M most will probably work but would need to be padded down.
Fried tweeters are common in foldback speakers due to feedback, as it does not take much feedback to fry them.
At first glance, I didn't see any problems. I did notice that the driver cones didn't seem rigid anymore, almost like how felt feels when you can pull it apart or shear it.
The tweeters definitely looked like piezo tweeters after looking online similar to [ THESE ] but without the bullet protruding.
The tweeters definitely looked like piezo tweeters after looking online similar to [ THESE ] but without the bullet protruding.
The tweeters are probably the KSN-1165 (oddly the KSN-1005 looks like the tweeter you linked to). CTS took over manufacturing Piezo tweeters from Motorola way back, and as far as I can see now, CTS have discontinued manufacture as well and some mob called Piezo source claim to have taken over
www.piezosource.com
the beauty of Piezos is that they are (relatively) higher impedance drivers, so they do not require a crossover (although a resistor in series is usually recommended, and being capacitive, impedance decreases as frequency increases) .
But if you are going to upgrade to non-piezos, then you will want a crossover.
while reputed to be damn near indestructible (especially as the KSN1165 has built in protection) I have seen them fried, although on at least one occasion they were destroyed by a Mosfet amplifier going into self oscillation.....
so back to your original quandary, your choices are:
try and identify the existing drivers and replace them - are there any part numbers on the woofer? the tweeter sounds like it is most likely the KSN1165
or go with a new design just using the existing cabinet and try and find new speakers and crossover etc.. that would work.
I would need to know more about the cabinet volume and any porting to know what to suggest here.
I am a fan of Co-axial drivers for foldback and close monitoring, as I get annoyed by having the high frequency source separate from the low frequency source - which is often very obvious where the drivers are side by side.
My current foldback wedges use B&C 8CX21 drivers which gives me a nice very compact wedge.
www.piezosource.com
the beauty of Piezos is that they are (relatively) higher impedance drivers, so they do not require a crossover (although a resistor in series is usually recommended, and being capacitive, impedance decreases as frequency increases) .
But if you are going to upgrade to non-piezos, then you will want a crossover.
while reputed to be damn near indestructible (especially as the KSN1165 has built in protection) I have seen them fried, although on at least one occasion they were destroyed by a Mosfet amplifier going into self oscillation.....
so back to your original quandary, your choices are:
try and identify the existing drivers and replace them - are there any part numbers on the woofer? the tweeter sounds like it is most likely the KSN1165
or go with a new design just using the existing cabinet and try and find new speakers and crossover etc.. that would work.
I would need to know more about the cabinet volume and any porting to know what to suggest here.
I am a fan of Co-axial drivers for foldback and close monitoring, as I get annoyed by having the high frequency source separate from the low frequency source - which is often very obvious where the drivers are side by side.
My current foldback wedges use B&C 8CX21 drivers which gives me a nice very compact wedge.
That's why you use a Selenium DH200 or D220 and pad the hell out of it. 7 dB of pad raises the real 40 watt long term power capacity to 200. Let' see feedback take out THAT.
Crossover is mandatory for a real compression driver - 4th order at 2.5k with one of the mid-grade Seleniums and 6 to 10dB of pad and you pobably can't kill it. A crossover (and dummy load) with a piezo is helpful in both ruggedness and sound quality, but an adequately sized CD is better. The Delta 10A is a nice midbass driver for wedges - but they really don't sound good with a stock or textbook crossover. It takes a custom filter. The response rises steadily through much of the midrange and the finally breaks up. It needs a damped 2nd order filter, with one pole at 800 Hz (yes 800) and the other at 2.5k to cross over at 2.5k. With the Selenium I suggested, the resulting wedge is flatter than a pancake from 100 to 10k. A stock 2.5k network will "shout" at you and be prone to feedback.
The trouble is, by the time you get that far, you've put a lot of money into them.
Genuine Motorola piezos can still be got on ebay.
Such as these: Real Motorola Piezo Tweeters 836 KSN1165 | eBay
Such as these: Real Motorola Piezo Tweeters 836 KSN1165 | eBay
A Genuine Motorola Piezo would still die the same death as the original if all it has is a 2.2 uf cap on it. It takes 2nd order and a dummy load to make a piezo really bulletproof.
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