Questions regarding piezo tweeters, crossovers

[Splork]

Hi.
I'm building a set of speakers, in each box there will be one tweeter and one woofer.
The tweeters will be either:
CTS/Motorola KSN1025B
2"x6" Piezo Horn Tweeter
Impedance: High at low frequency
Power: 75W
Freq. Resp.: 1.8 KHz - 30 KHz
SPL: 92db

OR

CTS/Motorola KSN1167A
2-1/2" Exponential Piezo Bullet Tweeter
Impedance: High at low frequency
Power: 75W
Freq. Resp.: 3.8 KHz - 30 KHz
SPL: 92db

I'm leaning towards the first one due to the greater range of frequency response. Since these are going to be Woofer + Tweeter sets, properly covering the dynamic range IS a concern. Now, is there any reason why I'd want to avoid Piezo tweeters? Is there anything special I need to be concerned about?

The woofer will be:
Sammi CWR200B50
Impedance: 8 ohm
Power: 50W
Freq. Resp.: 24Hz - 4KHz
SPL: 85db

What I plan to do:
I plan to run negative from the amp to negative on the woofer, then positive on the woofer to positive on the tweeter. I ASSume I can connect a 2000 Hz crossover in between the two.

Would that make sense to anyone, at all? Am I completely wrong and about to destroy a bunch of gear?
Or is there an infinitely better way to do all of this?

As you may have guessed, this is not a super high end system, it's just gotta sound real nice playing Meatloaf at a reasonable (not-too-loud) level. It's for my girlfriend, part of a bigger thing really, and she's far from being an audiophile.

Also, will it be possible to connect a fuse or circuit breaker of some sort between the sub and the negative connection on the box to protect the speakers? Or is that WAY too much trouble for what it's worth?

Thx in advance.

[GM]

See if this answers your Qs:

http://www.ctscorp.com/components/Da...ation_Note.pdf

GM

[Splork]

Originally posted by GM
See if this answers your Qs:

http://www.ctscorp.com/components/Da...ation_Note.pdf

GM

Alright, so tell me if I understand correctly: I probably shouldn't even need to use a crossover, unless I hear a lot of harshness in the midrange, at which point an R-C Filter would do fine?

Sounds good to me. And I assume then, that I could just wire it in series with the woofer, positive on the tweeter to positive on the woofer, negative on the woofer to negative terminal on the box and expect no problems?

If so, that solves a lot. I'm just left with the question of whether or not it's possible to protect the speakers from being plugged into too powerful an amplifier. Could I use a simple fuse, or is there a more exotic solution I should be aware of, or is it going to cost twice as much as I'm spending on speakers anyhow?

btw, thanks a tonne for that link.

[GM]

>Alright, so tell me if I understand correctly: I probably shouldn't even need to use a crossover, unless I hear a lot of harshness in the midrange, at which point an R-C Filter would do fine?

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Correct.

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>Sounds good to me. And I assume then, that I could just wire it in series with the woofer, positive on the tweeter to positive on the woofer, negative on the woofer to negative terminal on the box and expect no problems?

====

Wire it in parallel and follow the guidelines for protecting it and the amp, just in case the amp doesn't have its own protection ckt..

====

>If so, that solves a lot. I'm just left with the question of whether or not it's possible to protect the speakers from being plugged into too powerful an amplifier. Could I use a simple fuse, or is there a more exotic solution I should be aware of, or is it going to cost twice as much as I'm spending on speakers anyhow?

====

Well, there's no such thing as too 'large' an amp, only to 'small' a one since it's the clipping that kills the speakers, though of course you can crank it up till you blow the speakers.

Anyway, yes, you can use a fuse, polyswitch, or simple lightbulb to protect it against a mishap. If the lightbulb is mounted on the speaker where you can see it, then you'll have a visual clipping indicator.

If fused, use a fast blow sized at whatever percentage of overcurrent the driver's rated for, or if no rating, then 130% of its calculated RMS short term rating is. Obviously, if you use a lightbulb it needs to be able to handle the current at the nominal resistance since it's in series, so size it accordingly. Automotive tailight, parking, etc., are the most commonly used.

====

>btw, thanks a tonne for that link.

====

You're welcome!

GM

[Bull]

Can't stand piezo tweeters and they are crap because no pro audio touring speakers use them and no hifi speakers over £80 use them either.
Piezos are harsh,spitty sounding and lack detail,only producing super high frequnices of 10khz and above accurately.
Even with a crossover they can't match the sensitivity of the over drivers and leave big gaps in the audio range.
So if u must use them, use them for super tweeters with a crossover at 6khz or above used with dome or compression tweeters.
Only good for adding the sparkle and hisssssss and maybe the top end of cymbols clashing,where this could be done with a better with a super tweeter such as a titanium bullet Ring Radiator super tweeter or Slot tweeter.
And for a hifi sitation i've never a piezo tweeter being used.
So Splork u and ya gf will be severally dissapointed in the poor sound quality.So the piezo might be down to 1.8khz,but it will be 'ear bleeding' horrible at those frequecies.
In your case the tweeter is more efficent than the woofer.
So if u have to use the piezo then buy a non-polarised capactor and put it in series with the piezo [a 1uf cap 100v NP capacitor],to cut the piezo off at 4khz instead of 1.8khz which will improve things a bit,and add a 22 ohm 2w resistor to the piezo to decrease the sensitivity for a better intergration with the woofer.
Or if u haven't bought em yet buy a cheap mini sized soft dome tweeter and use a [1uf 100v non- polarised capacitor] in series with the tweeter on the plus terminal side,to protect the tweeter from bass frequencies which would blow it.A miniture soft dome tweeter will sound a whole heap better than a piezo.

[Circlotron]

Originally posted by Splork
it's just gotta sound real nice playing Meatloaf at a reasonable (not-too-loud) level.

Funny you mention Meatloaf. Have a listen to the cymbals on the title track of the Bat out of Hell album. You could be forgiven for thinking that your tweeters are full of sand and also somehow being modulated by the bass. Avoid this piece of music if you are evaluating whatever tweeters you end up using.

My suggestion. 1/ Avoid piezo's. They are only useful for guitarists who want to slice cheese at 30 feet with their strings. Get an inexpensive ferro fluid dome tweeter and if possible use a 12 dB / octave crossover. Feed it a clean signal and you and the GF won't be disappointed.

2/ Just because she doesn't yet appreciate hi-fi as much as you do doesn't mean she shouldn't have the best anyway. Besides, if she ever got wind of the fact that you cut corners...

[navin]

dont underestimate your GF.

i know atleast 2 women who wer surprised at what they could listen to.

my sister today can tell the difference between cables. my wife could tell the difference in a 0.5 ohm resistor difference in teh BSC ckt of my speaker's XO.

simulations on LSPCAD showed teh the 0.5ohm difference would only make a .5db difference in the 300-1k range and she heard it. ok i heard it too but i was the onle doing the soldering and had seen the simulations so i was not an objetive listener she had not seen the simulations (could care less) all she said that one version sounded brighter than the other and more natural than the other and things like that.

BTW Richard Vandsersteen also built his earlier designs based on his wife's opinions.

moral: expose her to good sound and she will appreciate it. she might even challenge you to make a still better speaker next time :-)

[navin]

on a another thought what do you guys think of use a piezo to top out a fullranger like the fostex 207.