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Old 6th December 2010, 04:46 AM   #1
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Default Waveguide with piezo above fullranger

Thinking about using this piezo:
http://piezosource.com/general/datas..._datasheet.pdf
into this waveguide:
Dayton H10RW 10" Round Waveguide 1" Threaded | Parts-Express.com
to add above a Tang Band 1808 full range speaker in OB.

I need to figure out how to cross over to the piezo high (above about 8 KHz) preferably without altering the 8 ohm impedence of the full ranger. Also I'd welcome comments on how well you think this might work out. They'll be going into a pair of vintage Wharfedale SFB open baffle speakers whose drivers are shot (and will be reconed hopefully at some later date). The TB will go into an "adapter" custom made of plywood and then into the lower, 12" speaker cutout, and the piezo/waveguide would go into the upper 10" speaker cutout. Bass below about 100 Hz would be from some pro audio 18" speakers in sealed cabs sitting either next to or under the OBs, and the crossover between bass and the OB will be active.
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Old 7th December 2010, 12:09 PM   #2
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I don't think it's a real good idea. If you cross that high, you are going to have a serious directivity mismatch between the waveguide and the 8" Tang Band. The center to center distance will also be huge, causing you some serious lobing problems. That Tang Band is a nice driver. Many people don't think it needs a tweeter at all, but if you decide to add one, it deserves something better than a cheap piezo.
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Old 7th December 2010, 04:14 PM   #3
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Thanks for the response. I had also briefly considered the Eminence ASD1001S compression driver:
Eminence ASD1001S 1" HF Titanium Horn Driver 1-3/8"-18 TPI | Parts-Express.com
but that would involve a "true crossover" and seems to have a significant roll off in the highest frequencies where I want it to add in. I could use a piezo without a waveguide at the top (in place of the 3" cone tweeter) pointed up to avoid most lobing issues and just fill in the 10" cutout. I'll most likely just try the Tang Band alone to start, but thinking of other options in pursuit of DIY speaker greatness.
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Old 8th December 2010, 01:39 AM   #4
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Quote:
Originally Posted by Rev. Billy Bob View Post
If you cross that high, you are going to have a serious directivity mismatch between the waveguide and the 8" Tang Band. The center to center distance will also be huge, causing you some serious lobing problems. That Tang Band is a nice driver.
i agree with just THESE bits from billy bob. personally i would try and find a small piezo cone tweeter-i think motorola still do them- and load THAT with the dayton waveguide. I would use with NO crossover at all, just resistor padding, to (hopefully) reduce any lobing issues or driver spacing issues. anything but that AWFUL piezo compression type driver.

Or, take a look at tangband w2-800sl. im using one as a wideband tweeter in a 2way project crossed at 500hz. You COULD mod the waveguide to accomodate the 2" driver, but im not certain that it would work too well. but it WOULD be an experiment! OR you could cross it 1st order with the 1808, low enough that polar lobing is minimal, but high enough that the 1808 still provides most output, even at HF.

im not sure THAT would work either, but its just an idea.

Or, just forget the tweeter altogether, and maybe boost HF a bit if its really that necessary.

rgds
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Last edited by mondogenerator; 8th December 2010 at 01:45 AM.
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Old 8th December 2010, 03:37 AM   #5
freddi is offline freddi  United States
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1772 have adequate/good highs I've used KSN1142 (rough response and two dips due to phase plug) - not sure about 1188

Last edited by freddi; 8th December 2010 at 03:40 AM.
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Old 8th December 2010, 05:42 AM   #6
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Originally Posted by freddi View Post
1772 have adequate/good highs I've used KSN1142 (rough response and two dips due to phase plug) - not sure about 1188
i second that. most ive been interested enough to look at (for a FR virgin lol) have easily enough HF and i feel im quite picky in regard FR drivers, since im STILL holding out for the ultimate performance:value driver.

these two defo have enough HF, if maybe a tiny bit ragged

http://www.tb-speaker.com/detail/1208_03/w5-1611sa.htm slightly ragged over about 5k, a attenuated above 10k, no big issues here

http://www.tb-speaker.com/detail/1230_04/w5-1880.htm same as above

and your choice:

http://www.tb-speaker.com/detail/1230_04/w8-1808.htm slightly rising response above 5k, which if anything for ME personally, i would choke off a bit of the HF if anything. the only other thing i dont like is the whizzer cone, if you can stand that, then you dont even need to bother with a tweeter at all
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Last edited by mondogenerator; 8th December 2010 at 05:51 AM.
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Old 8th December 2010, 03:12 PM   #7
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In listening to my 1808s on a much smaller open baffle, they to have to my ear a lot of treble, but they seem to lack a little top end "sparkle". It may be just that I'm used to hearing the distorted noise that some tweeters produce up high. Especially off axis, I don't think the 1808s put out much above about 12 to 13 KHz. I'm definitely not doing a "whizzerectomy" on these, but if I add a supertweeter I might also add a Zobel. Overall, just trying to think it through thoroughly before I commit to cutting out the plywood inserts. I've also thought a little about putting the TB in the upper, 10" cutout and using a 12" woofer in the lower cutout with some EQ to provide the bass and forget using my "helper subs".
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