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PA horn driver repair question


djRocky

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Hi Friends :pissedoff:

advice appreciated re: repairing a piezo horn driver vs replacement (cost and recycling):

 

the tweeter wasn't working on the Nady PS115 cabs I bought used. Couldn't find detailed specs/schematics on Nady site. Can I reattach the wires holding the piezo disk, and glue it to the horn? I assume it would take special glue that flexes, yet holds.

 

Any advice from an experienced soundy is good :pissedoff:

 

thanks!

Mik

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Mik,

 

It's likely to have failed due to over temperature, rather than a wire coming off - unless you have inspected this and the wires are indeed adrift?

 

Most piezos are relatively inexpensive, and it would probably be better to have a fully working unit than one which has failed and may not be easily brought back to life again?

 

Simon

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Hi Simon & thanks for the timely reply!

 

I had only inspected just one of the horn drivers, when I took the other one apart, I noticed that the piezo disk was attached, but the capacitor was not - it apparently came apart! quite literally the wires were attached but the capacitor was sitting by itself in the driver cover.

 

I think you are right, and that both units suffered some previous misfortune in their previous life...The woofers work well, but the tweeters didn't. Good tip - probably better to get a new driver that starts clean. I will see what a capacitor costs for the driver that is only missing one, otherwise it looks pretty solid. I did see some 500 watt high compression drivers, on the web (, as the OEM description indicated), for less than $20, so if I need to replace, then it's not too pricey.

/m

 

 

Mik,

 

It's likely to have failed due to over temperature, rather than a wire coming off - unless you have inspected this and the wires are indeed adrift?

 

Most piezos are relatively inexpensive, and it would probably be better to have a fully working unit than one which has failed and may not be easily brought back to life again?

 

Simon

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Piezo drivers need a simpler crosover than compression drivers. A well chosen, correctly driven compression horn will sound better than a piezo, but with the wrong crossover the compression driver could die very quickly.
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On occasion I've seen compression drivers advertised that quote the total power handling of the cab that they anticipate being installed in. ^_^

Maplins (sorry) used to have a "600W" compression driver. Once you looked a bit closer, they said it was actually only 80...

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B&C makes a 2" comp which will handle 280w down under 1kHz :blink: Silly money too. I would say I'd be worried about blowing them due to the cost, but you'd have to try pretty hard! ^_^
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What is the total RMS wattage of the Nady cabs?

I assume a 15"... replace the whole driver or seek a crossover and 1" throat horn.

I 've just gone down this route with a couple of 100-150w boxes with a 10" (originally by Eminence - no brand on box, probably Carlsboro or similar) + motorola for a bit of shine. Being a bit "fino" (epicurean!) about sound, I sourced a couple of Beyma SM2012/N +Xovers for less than €100 trade. Motorolas would have probably been about €30. But like most of my gear; If a jobs worth doing... and even if appearance is a bit rough I VERY rarely get complaints about sound qualiy. Will report when loaded in a couple of days.

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It's worth noting that those cabs are VERY quiet speakers - 91.5 dB/1w/1m. Adding in a good compression driver which will have a sensitivity over 105dB/1w/1m is going to make them incredibly toppy to the point of being unbearable. Could you imagine a 15dB peak from 1 - 2.0kHz and upwards?
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I note your comment Killyp about the Nadys: evidently not very efficient on Watts to dBA...

While you can usually use a capacitor and a variable wire wound resistor to adjust a piezo (cheap option) , a horn tweeter will always be mucho (!) more efficient than direct radiating transducers and will require a series/parallel (look up constant impedance) network to adjust the relative loudness... Crossover adjustment takes a lot of time and patience to get it right never mind about getting the right Zimpedance load on the amp (horrendous task)! ! ! However, once done even in severely abused systems tweeters have survived better than on commercially available units I have sold during the last year - the general reliability (despite bulb and similar protections) seems to be getting worse even with reputable U.S./world established brands - a pity...

Back to the case in hand look up other Beyma horns though from the images I've seen of the speakers you will have to check if the magnet etc will fit.. I mention the make because of availability and data supplied, not because I'm a Beyma fan - by preference I still use units from what remains of British speaker manufacturers, though the Germans and Italians also offer some incredible units.

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Precision Devices and B&C are also very good, but their cost reflects their quality, and even if you could get them wired up correctly in the cabs, they may be a little wasted. Possibly worth looking for some cheaper (dare I say it) Eminence drivers? They'll be a step up from what's in the cabs at the moment, and won't break the bank.
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I contacted Nady and they told me that 250 RMS is correct wattage. Also, they recommended replacing drivers ($20 USD, each, plus shipping).

 

I will replace a cap on the one driver that is otherwise complete, except for cap and we'll see :P

 

On occasion I've seen compression drivers advertised that quote the total power handling of the cab that they anticipate being installed in. :bleh:

Maplins (sorry) used to have a "600W" compression driver. Once you looked a bit closer, they said it was actually only 80...

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