Piezo Tweeters on XF212

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Mark Bottomley
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Joined: Mon Jul 15, 2019 9:09 pm

Piezo Tweeters on XF212

#1 Post by Mark Bottomley » Wed Nov 06, 2019 10:56 am

Hi,

I have built an XF212 with a closed back. I use it (and my Jack Lite 10) for both guitar, bass, and vocals. Compared to the Jack Lite 10 which has a 12-tweeter cross-firing array, I miss the high end. The speakers are 12" 8-ohm Peavey Scorpions so they are ported through the centre cone and they are rated for lots of power handling. I have configured the inputs to allow the cabinet to be 4-ohn, or 16-ohm mono, or 8-ohm stereo. The cabinet could use a cross-firing piezo array in the middle (I would use 8 tweeters) or I could mount two tweeters under each of the Scorpions. After reading some other articles about filters, I would need filters on both drivers. Is there a preferred tweeter configuration? If a cross-firing array, should it be wired with stereo right to the left side speakers firing right and vice versa? Should I be adding any porting to handle bass inputs (I have several 5-string basses with low B strings)? The stereo configuration would only be for guitar as bass lacks the directionality to make stereo useful.

Thanks in advance

Mark...
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Bruce Weldy
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Re: Piezo Tweeters on XF212

#2 Post by Bruce Weldy » Wed Nov 06, 2019 11:11 am

I doubt that your guitar amp is voiced such that you would get a lot out of piezos, unless you are using a pedal and a standard power amp.

As far as stereo.....forget it - with speakers that close together, everything hits the audience in mono.

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Bill Fitzmaurice
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Re: Piezo Tweeters on XF212

#3 Post by Bill Fitzmaurice » Wed Nov 06, 2019 11:59 am

You'd use the same cross-firing tweeter array as with the Jack 10. Filter wise with the way you've wired it each woofer would have to be separately filtered. Bruce is correct about the stereo option, it's not worth the bother. Anyone more than a few feet away will hear it as mono.
Your woofers aren't ported through the center domes. If they have porous domes that's for voice coil cooling, not porting.

Mark Bottomley
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Re: Piezo Tweeters on XF212

#4 Post by Mark Bottomley » Wed Nov 06, 2019 12:56 pm

Thanks for the responses. The amp(s) I use are Gallien Krueger MB200s - 250W into 4-ohms. They are rated up to 20KHz, unlike a normal guitar amp and despite being sold as a bass amp. I do notice a significant difference between the Jack Lite 10 and the XF212 in the treble area. The Jack Lite 10 uses a 4-ohm Eminence Delta-Lite II.

The Scorpion speakers have a doughnut-shaped replaceable magnet and through the porous centre dome it is open into the cabinet. The material may be sufficiently blocking to not act like a port. I don't know. Should I add a front port and if so, any suggestions on the dimensions?

I do use a BBE Sonic Maximizer and that definitely improves (IMHO) the clarity of the signal.

For reference, the constructed weights of the XF212 and the Jack Lite II are 37 and 24 pounds respectively.

Thanks for the designs - I like how they work and the weight.

Mark...

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Bill Fitzmaurice
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Re: Piezo Tweeters on XF212

#5 Post by Bill Fitzmaurice » Wed Nov 06, 2019 1:03 pm

The only options that make sense for the guitar frequency range are sealed and open back per the plans. If you use it for bass the cabinet volume is too small to tune it low enough for ports to be useful.

Mark Bottomley
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Re: Piezo Tweeters on XF212

#6 Post by Mark Bottomley » Wed Nov 06, 2019 1:56 pm

Thanks all!
Mark...

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