PA Speaker Parts

paulphoenix

Can anyone suggest any good places for online speaker parts. 

I bought some secondhand speakers t'other day and one of the piezo drivers is broken. 

The plastic flare horn is 195x120mm and CPC/Terralec generic replacements are either too small or too big. The driver is screwed on to the flare not threaded.

The speakers are Studiomaster GX12 passive. I have emailed studiomaster but expect a less than inspiring reply. 

Anyone have any super suppliers for speaker parts they wish to divulge?  

maltingsaudio

Blue arran in Southampton my go to guys

paulphoenix

maltingsaudio said:

Blue arran in Southampton my go to guys

i'll send them my problems. thanks. 

ESBlonde

I think all the piezo drive units are similar (although I've not pulled many apart recently because they are so cheap to buy.
It's possible that a couple of quid gets you this and you unscrew the driver from the horn and screw it onto your horn. Without your horn to see I can't tell if the attachment screw holes are identical. A good seal around the horn throat is required.
http://uk.farnell.com/mcm-audio-select/53-800/3-1-8-square-piezo-horn-tweeter/dp/2827734?mckv=YO18ZYDl_dc|pcrid|78108376509|&gross_price=true&CATCI=pla-41477300408&CAAGID=14406255429&CMP=KNC-GUK-GEN-SHOPPING&CAGPSPN=pla&gclid=EAIaIQobChMIqsrdr5WR2gIVr7_tCh0OiQHnEAQYAiABEgIud_D_BwE&CAWELAID=120173390002173301

paulphoenix

ESBlonde said:

I think all the piezo drive units are similar (although I've not pulled many apart recently because they are so cheap to buy.
It's possible that a couple of quid gets you this and you unscrew the driver from the horn and screw it onto your horn. Without your horn to see I can't tell if the attachment screw holes are identical. A good seal around the horn throat is required.
http://uk.farnell.com/mcm-audio-select/53-800/3-1-8-square-piezo-horn-tweeter/dp/2827734?mckv=YO18ZYDl_dc|pcrid|78108376509|&gross_price=true&CATCI=pla-41477300408&CAAGID=14406255429&CMP=KNC-GUK-GEN-SHOPPING&CAGPSPN=pla&gclid=EAIaIQobChMIqsrdr5WR2gIVr7_tCh0OiQHnEAQYAiABEgIud_D_BwE&CAWELAID=120173390002173301

I had thought about bastardising a cheap unit like this, but it could result in some serious fudging to make it fit!

My other  option is this i guess: 

 http://cpc.farnell.com/pulse/pls00308/tweeter-piezo-horn-195x155mm/dp/LS03584?ost=pls00308&categoryIdBox=&selectedCategoryId= ;  

For which I'd need to make my cut out slightly larger - I've checked and I have room for this unit (just) 

Truth be know I'm a bit befuddled about getting the correct piezo specs on the replacement - Ratings/Watts/Ohms/Frequencies etc... does it matter a huge amount?

ESBlonde

Piezo drivers have no actual rating themselves, they are rated to use with bass drivers of the given wattage. Impedence is all but meaningless too, the crystals bunch up tighter as the freq rises and reduce the resistence allowing the membrane to vibrate progessively more in the higher frequencies (which are still present in the bass driver too). there is a pair of resistors externally on some units to control the load. this should be replicated on any new unit if applicable.

Given the relativly low unit cost, I'd be temped to replace the good and the bad units to retain symetry, but piezos are naff at best and I doubt most people will note any difference in response or dispersal patterns.

paulphoenix

Thanks for your help @ESBlonde ;


I tested the speakers last night at practise with an ipod at high volume (pumping out Hendrix and Royal Blood) and then at rehearsal volume with our band vocals. There was little noticeable difference between the good and bad tweeters, but  is it harmful to run a speaker with a damaged tweeter? should I cease using the speakers until I've got them fixed? 

ESBlonde

With a piezo horn there is no risk to amplifier or the big cone driver. The cone still gets full range all the time but it beams the higher freqs rather than dispersing them evenly. The advantage of the piezo is it adds more highs over a wider area out front.
You cannot add just piezos to an amplifier without proper speaker because they present no meaningful load to the amps output section.

ICBM

If you want to use the speakers for anything serious I would be inclined to look for some proper compression driver tweeters that will fit. You may also need a better crossover.

Piezo tweeters are universally horrible.

Danny1969

Those speakers are only around £75 each complete, so maybe not worth spending a lot on. Generally piezo speakers have a cap in series to present a high impendence to lower frequencies, if you have one check the cap before you replace the horn

I agree with ICBM about changing them for compression drivers and flare but you would need at least at basic high pass filter crossover to protect the compression driver

maltingsaudio

@Danny1969 and @ICBM  I agree cheap piezo’s are horrible but properly machined and engineered units are just as good and efficient as compression drivers. Trying to swap piezo’s for compression drivers in a unit designed for piezo’s isn’t going to work without a lot of heartache and at the price point of the Studiomasters simply not worth it

ICBM

Fitting a proper crossover is easy and cheap, so I really don’t see where the heartache is...

eg these, for under a tenner - https://www.cricklewoodelectronics.com/High-Quality-250-Watt-2-Way-Crossover-12dB-8-Ohm-200W.html?gclid=EAIaIQobChMI6df519iZ2gIVzr_tCh3eEg0uEAQYASABEgIc_PD_BwE

The biggest problem is finding something that physically fits the hole in the cabinet or can be made to do so with the minimum of work.

maltingsaudio

ICBM said:

Fitting a proper crossover is easy and cheap, so I really don’t see where the heartache is...

eg these, for under a tenner - https://www.cricklewoodelectronics.com/High-Quality-250-Watt-2-Way-Crossover-12dB-8-Ohm-200W.html?gclid=EAIaIQobChMI6df519iZ2gIVzr_tCh3eEg0uEAQYASABEgIc_PD_BwE

The biggest problem is finding something that physically fits the hole in the cabinet or can be made to do so with the minimum of work.

The cabinet is £80 new on amazon, the option would be to buy a new flair with compression driver but to get one that’s going to do the job is about £ 25 plus flair, then add the cost of the crossover making sure it matches the speaker and driver, then add the woodwork mounting,and I rest my case. On the flip side as a project you’ll learn a bit from it.

paulphoenix

I’m always willing to learn so I’ll have a look at replacing the piezo for a compression driver. Inside the cab is already what looks like a crossover (for the piezo)? 

paulphoenix

... plus the speakers didn’t cost me a fortune so I’m not against investing a little extra money if it meant the tweeters (speakers) would be upgraded 

ICBM

maltingsaudio said:

The cabinet is £80 new on amazon, the option would be to buy a new flair with compression driver but to get one that’s going to do the job is about £ 25 plus flair, then add the cost of the crossover making sure it matches the speaker and driver, then add the woodwork mounting,and I rest my case. On the flip side as a project you’ll learn a bit from it.

... and end up with probably much better-sounding speakers than you could get for £80, regardless of whether the tweeter and crossover accurately match the bass driver or not.

You may be right about high-end piezos, but cheap ones *always* sound horrible. That distinctive spitty top-end fizz is the absolute bane of cheap PAs.

paulphoenix

A little further help and guidance please oh wise men, just so I can finalise which way I'm headed with all this speaker malarkey.

I opened up the patient just now and took a photo of the PCB/guts inside.

So it looks like a (very) basic 2 way crossover right?

Coil inductor/20w resistor 16ohm/3 caps (could only read the one top left in the picture @ 2.2uf)

Is this crossover man enough/good enough/correct enough to be able to straight swap the broken piezo for a compression driver? If so what sort of spec should I be looking at (wattage and ohm wise) on a new compression driver? Or would the crossover require upgrading to feed a different driver?

I'd be willing to chuck around £50 at this and would like to change both speakers at the same time. I plan to modify the existing plastic flare (1" throat) to accept a new bolt on driver. 

Or do I just cut my losses, replace with cheap and cheerful piezos and make do until I can afford to upgrade? 

Here are the original speaker specs for your consideration: 

Format: 2 Way 12″
Power Handling: 200W (continuous), 800W (peak)
Nominal Impedance: 8ohm
Frequency Response: 60Hz – 18kHz
Maximum SPL: 97dB
Crossover Frequency: 4kHz

ICBM

Could you do a pic of the other side? And say where the four coloured wires go to. (Usually blue/yellow are the bass driver and red/black the tweeter.) That should make it possible to check exactly what the circuit is.

It does look like it should be adequate to protect a compression driver, anyway. I would go for an 8-ohm 100W driver - it doesn't need to be as highly rated as the bass driver since there's less energy in the high frequencies. You might get away with less, but more risky.

ESBlonde

The stats for the cabinet suggest a compression driver of 25w RMS or more would be adequate above 4Khz. 100w RMS won't hurt but is overkill in this application. the compression driver is not taking a lot of power up that high. Beware of going too big and expecting to increase the cabinet handling, the crossover looks barely adequate to handle a 200w amp continuous and I would expect that to be the weak link. Still if you can get comp drivers in there it's got to be worth the effort for an improved sound. the comp driver should match the impedence of the bass driver for best effect to work with the crossover.

paulphoenix

Thanks IC, I know the blue and yellow go to the piezo, I will try and remove the pcb to get a photo of the reverse side. 

ICBM

ESBlonde said:

The stats for the cabinet suggest a compression driver of 25w RMS or more would be adequate above 4Khz. 100w RMS won't hurt but is overkill in this application. the compression driver is not taking a lot of power up that high. Beware of going too big and expecting to increase the cabinet handling, the crossover looks barely adequate to handle a 200w amp continuous and I would expect that to be the weak link. Still if you can get comp drivers in there it's got to be worth the effort for an improved sound. the comp driver should match the impedence of the bass driver for best effect to work with the crossover.

That's true, although I would err on the side of caution, even with a fairly high crossover frequency - the last thing you want is to have to replace the compression drivers given that the economics is a bit tight anyway. Around a third of the cab rating is about right to give some safety margin, from practical experience - which is about 70W. 100W is maybe a bit too high, but I definitely wouldn't go below 50W personally. You certainly won't increase the overall cab rating by going higher, but it makes blowing the tweeter much less likely.