Help Needed: inexpensive speakers with bandwidth to 50 kHz?
May 15, 2006 at 9:45 PM Thread Starter Post #1 of 10

Ferbose

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My friend is conducting research on insects' perception of ultrasonic signals.
She needs a speaker that has a flat frequency response up to 50 kHz.
Is anyone familiar with fairly inexpensive speakers (<$500) with such bandwidth?
 
May 15, 2006 at 10:07 PM Post #2 of 10

Ferbose

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I found Sony SSMB-150H, which claims to use nano-fine tweeter (whatever that means) that extends to 50 kHz:
http://www.sonystyle.com/is-bin/INTE...nents_Speakers

Can anyone comment on whether or not it extends that high?
I guess Sony's specs should be believable, right?
 
May 15, 2006 at 10:26 PM Post #3 of 10

tennisets

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Quote:

Originally Posted by Ferbose
I guess Sony's specs should be believable, right?


Definitely not. Have you ever looked at Sony's headphone specs? They claim the SA5000 has a frequency respons of 5 - 110,000 Hz. Yeah, right.

You won't get frequency response to 50 KHz with a conventional dome tweeter (as far as I'm aware). You'll need something like a ribbon tweeter or supertweeter to get that kind of extension.
 
May 15, 2006 at 10:40 PM Post #4 of 10

Ferbose

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May 15, 2006 at 10:45 PM Post #5 of 10

tennisets

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I just don't think you could possibly get extension to 50 or 100 KHz with a tweeter like that. The mass market companies will say anything to sell their product. It's probably something like 100 KHz at -60 dB if it reaches that high at all.

You said you need a flat frequency response to 50 KHz. It's very, very difficult (and hence expensive) to get that kind of extension. I'm sorry I think it's probably impossible to find speakers that reach that high under $500.

Whatever you go with, make sure the frequency response measurements include the range they allow (i.e. +/- 3 dB).
 
May 15, 2006 at 10:48 PM Post #6 of 10

tennisets

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Actually, why do you need a conventional audio speaker at all? It seems to me you would be much better off seeking out a speaker designed to reproduce only ultrasonic signals. I think you're barking up the wrong tree, though where you should turn instead I have no idea.
 
May 15, 2006 at 11:01 PM Post #7 of 10

BradJudy

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Does she need to be able to produce sound below ~10kHz as well? If not, how about just picking up a pair of supertweeters like these: http://www.av123.com/products_produc...s&product=77.1

Or any of several ribbon tweeters by themselves with a simple high-pass filter to block anything below say 5kHz (depending on the tweeter). If you don't need the lower frequencies, then there's no need to buy entire speakers.
 
May 15, 2006 at 11:03 PM Post #8 of 10

Ferbose

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Quote:

Originally Posted by BradJudy
Does he need to be able to produce sound below ~10kHz as well? If not, how about just picking up a pair of supertweeters like these: http://www.av123.com/products_produc...s&product=77.1

Or any of several ribbon tweeters by themselves with a simple high-pass filter to block anything below say 5kHz (depending on the tweeter). If you don't need the lower frequencies, then there's no need to buy entire speakers.



My friend needs frequencies down to 500-1000 Hz.
Therefore, I think most super-tweeters can't satisfy.
 
May 15, 2006 at 11:35 PM Post #9 of 10

Wodgy

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Your friend needs to be realistic about what she wants... first: how flat the response needs to be, and second: what off-axis behavior she needs.

As far as I know, there are no commercially available dome, compression, bullet, or piezo tweeters that are remotely flat to 50kHz. The ones that advertise extreme extension (45kHz, etc.), usually are 12dB to 18dB down at 50kHz. Not flat at all, and that's on axis only, off axis the drop off is much more rapid. Ribbons come closest to flat, some being "only" 6dB down at 40kHz or so.

(Despite all the advertising by Sony et. al., no, there are no 1 inch dome tweeters in the world that are flat to 50kHz, not even the expensive Accuton ceramics. Some of the Accuton 3/4 inch diamond domes may do this, but at a raw cost of $2600/tweeter.)

So first off, if her research requires flat response out to 50kHz, she's going to have to invest in expensive measurement gear (standard microphones do not go out that far) and equalization to compensate for the realities of physics. If +/-10dB at 50kHz is good enough, then an appropriate ribbon may satisfy her needs. Some of these would be appropriate:
http://www.madisound.com/cgi-bin/ind...=9914729.28395

The other problem is off-axis behavior. High frequencies are very directional, with quite a drop off even 15 degrees off axis. Obviously, insects are not stationary and fly around. She needs to keep them flying within a 30 degree window from the tweeter in order for them to receive the high frequencies. Ideally, this means the tweeter should be placed far back from the insect cage or housing, and a tweeter be selected that has high enough power handling to compensate for the dropoff due to distance.

Anyway, what she should do is purchase a single reasonably flat commercial speaker, say a single Paradigm Atom, along with a ribbon tweeter with good extension. Put a cap and l-pad on the tweeter to cross it over to the commercial speaker. That's the only way she'll get reasonably close to flat extension out to 50kHz on her budget.
 
May 16, 2006 at 5:21 AM Post #10 of 10

Ferbose

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Quote:

Originally Posted by Wodgy

As far as I know, there are no commercially available dome, compression, bullet, or piezo tweeters that are remotely flat to 50kHz. The ones that advertise extreme extension (45kHz, etc.), usually are 12dB to 18dB down at 50kHz. Not flat at all, and that's on axis only, off axis the drop off is much more rapid. Ribbons come closest to flat, some being "only" 6dB down at 40kHz or so.



How about this 1" dome tweeter in Tannoy's studio monitors?
http://www.tannoy.com/Default.asp?Id=5274

When Tannoy says frequency response is 60Hz-51kHz for their pro-audio monitors, I tend to beleive it is really +/-3dB flat in that range.

BTW, my friend's insect is fixed on a table, so off-axis response is not an issue.
 

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