BillFitzmaurice.info

Good day!

Last gig we blew up the tweeters in a pair of Carvin 1584. I'm sorry Bill, I bought those 30 years ago when I didn't know better. In my defense, If you look at their spec sheet it shows 100dB SPL 1W @ 1m, and flat from 50-20kHz +-3dB. At the time I thought they were pretty good based on the specs. However, I cannot reproduce their measurements, not even close. That is one of the reasons I came to BFM, the stated expectations are realistic. Anyway I'm off topic, don't mean to bash Carvin, most every speaker manufacturer seem to use some ideal test conditions that I can't reproduce. And the Carvin 1584 has been through a lot of abuse with very little issue, so a 30 year run without problems is very good.

I have a gig this weekend, and I stole a BFM trick of a flat piezo array to replace the tweeter horn: I can't get parts quick enough in the middle of Montana. Six piezos just happened to fit in the existing cut out. However, while one sounds as good as ever, the other is still a bit muddy. Is it possible that the array is out of phase? These speakers have a three way crossover, and I rewired the array in the same polarity as the tweeters I removed.

Also the tweeter I removed was 16 ohm so I wired three series pairs of tweeters to boost the impedance a bit. I assume that lowers the crossover point so there's some risk of blowing these up because lower frequency content may be getting to the tweeter. I just need to make it through a couple (few?) more gigs, then I can replace these with BFM mains.

Thanks Bill, et. all. I was a bit desperate last night when I realized the tweeters were blow and they needed to work Saturday. Happening to have a bunch of piezos that are going into Wedgehorn 10's laying around was a simple and quick fix, all props to BFM and his designs.

Thoughts? Suggestions? Today I'll be measuring response, so I'll have more scientific data about the performance soon.

Best!

The high pass for the original compression driver won't work with piezos. They'll function, but the high pass filter isn't doing anything.

Should I solder one together or not worry about it?

Sorry, more directly, will I damage them up if I don't solder together a crossover? I don't understand piezos.

You probably won't damage them but they won't work as well as they would with the correct high pass filter.

Thank you.

Made it through the gig. Small gig, didn't have to push hard.

EDIT: The fix to the one that didn't sound right was one piezo that had the same SPL, but not the same high end reproduction. Test carefully!

I'm going to replace the 8" driver, it's a little suspect, in both speakers, and put a proper crossover in for the piezos.

It's anecdotal, but one person who's heard those speakers a lot, mentioned that they sounded "a lot more crisp" then he remembered them. I'm not recommending this as a modification, but rather as support of the flat array piezo concept.

Thanks again Bill.