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piezos, tweeters and horns (oh my!)


Fred TBP

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I've noticed a lot of builders using inexpensive piezo tweeters (I think that's what they are, they're made of plastic and you can find them in a lot of inexpensive PA equipment as well) in their cabs and combos and often wished there was a way to replace them. Most of them hiss, and I don't think it has to do with the maker's circuit. I've already replaced the stock speaker on my SWR Workingman's 15 combo (to a JBL K140 if you're interested) and I've wanted to do the same with the tweeter.

 

Before I go to my long-time contacts in the repair field, I thought I'd ask y'all for suggestions. I'd prefer a direct-mount replacement, but I'm not afraid of drills and routers either. My concern is the tight fit in these cabinets, not the frequency response, although it might involve getting a separate crossover to add to the circuit.

My thanks to all! :wave:

 

PS: at present the search results for "piezo" is 187, "tweeter" is 216 and "horn" is over 300; that's just on the LDLD forum. I might be off Google-ing for awhile.

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You will need to add a crossover circuit, it's doubtful you will find one in a cab with a piezo driver. Piezo horns don't need them, they naturally attenuate frequencies below a certain point.

 

Consider that they are most often used in cheapie systems, and the horn and crossover, and you may also need a separate level control since you don't know if the horn sensitivity will be greater -or even less than the low frequency driver. The investment may render it an unwise move... the phrase "polishing a turd" comes to mind, if the cone driver is mediocre.

1000 Upright Bass Links, Luthier Directory, Teacher Directory - http://www.gollihurmusic.com/links.cfm

 

[highlight] - Life is too short for bad tone - [/highlight]

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Good points, gentlemen, keep them coming. I'm mulling it over and I'm especially conscious of what Bob mentioned on the cheap components. Probably not worth risking the expense when I'm really looking at a new cabinet (I still recall how great adding the David Eden 2x10 made my combo sound), but I've gotten good results with the SWR/JBL hybrid and it's making me consider going a little further to tweak the high end.

 

I've acquired, polished and subsequently dumped quite a few turds in my time, so I appreciate the caveat. :D

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An upgrade would be cheapest from Carvin: their current tweeter (or their past Foster with the attached horn), and their crossover/cup. Actually even piezos can benefit from the crossover, but piezos are relatively inefficient and often can barely keep up with the woofers in such cabs.

 

More efficient piezos can be had, but they usually have higher natural cutoffs. As it is, tweeters in two-way bass cabs are crossed over lower than sounds as good as when the same one is used in a three-way system with a 5K or higher crossover.

 

That's part of the secret of such cabs as Accugrooves BTW: the poor polar pattern and jagged response of cone-cry freq's of the woofer is not used as a stop-gap to come up to the lower frequencies of the tweeter, and thus smoother extended response is to be had over a wider area of dispersion.

 

Anyway, the cheapest way mentioned at the top of the post is the only practical upgrade for your cab, provided the diameter isn't a problem. You will gain good attenuation and speakons and 1/4" in parallel as well...

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