Piezo Tweeter L-Pad?

Ling Gowa · 24th November 2009, 06:15 PM

I have a friend who has a piezo that is about 105 db and we would like to lower that a lot. Is an L-Pad for a piezo any different that a conventional one? Any good reccomendations?

Jonathan Bright · 24th November 2009, 07:27 PM

Yes, they are quite different. Because they are highly capacitive by nature you can/should use series capacitors to attenuate them. There is a table in Bost's original JAES article from the 1970's. I can't remember the exact values but small caps (bi-polar) under 1uF will achieve a uniform reduction in level. (Series resistance causes high frequency roll off.) Now, having said that, I think people have used L-pads too. Have you tried a Google search? There have been a few sections of DIY books that look at this issus.
But putting 0.47, say, in series will difinitely produce a noticable difference.....I think.

Ling Gowa · 24th November 2009, 07:42 PM

What happens when you put a resistor on the positive?

Jonathan Bright · 24th November 2009, 08:04 PM

Morning Ling, well it is morning here in Australia.
A resistor (30 to 50 ohms) feed to the speaker will cause a hi-frequency roll off of a few db at the top end. It doesn't matter which terminal +ive or -ive.

BTW I did google "pizeo tweeters" and found very useful site. It is the 3rd or 4th entry and is a forum from "audiokarma". The guy there is a bit digmatic and wrong in what he says about series resistance but he does have the L-pad circuit you are looking for. Try that and see if it is helpful. Good luck, Jonathan

DigitalJunkie · 24th November 2009, 08:50 PM

IIRC,Motorola suggests a small resistance in series with their piezo tweets,forget the exact reason why though.

Godzilla · 24th November 2009, 09:53 PM

Here is some information i put together based on my experience with piezos...

Piezo Super Tweeter

I like them and use them often in most, but not all, of my projects. Hope it helps.

Godzilla

Ling Gowa · 24th November 2009, 09:55 PM

Now that's well done info. Thanks.

24th November 2009, 06:15 PM	#1
Ling Gowa diyAudio Member Join Date: Aug 2009 Location: Barrie, Ontario	Piezo Tweeter L-Pad? I have a friend who has a piezo that is about 105 db and we would like to lower that a lot. Is an L-Pad for a piezo any different that a conventional one? Any good reccomendations?

24th November 2009, 07:27 PM	#2
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	Yes, they are quite different. Because they are highly capacitive by nature you can/should use series capacitors to attenuate them. There is a table in Bost's original JAES article from the 1970's. I can't remember the exact values but small caps (bi-polar) under 1uF will achieve a uniform reduction in level. (Series resistance causes high frequency roll off.) Now, having said that, I think people have used L-pads too. Have you tried a Google search? There have been a few sections of DIY books that look at this issus. But putting 0.47, say, in series will difinitely produce a noticable difference.....I think. __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

24th November 2009, 08:04 PM	#4
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	Morning Ling, well it is morning here in Australia. A resistor (30 to 50 ohms) feed to the speaker will cause a hi-frequency roll off of a few db at the top end. It doesn't matter which terminal +ive or -ive. BTW I did google "pizeo tweeters" and found very useful site. It is the 3rd or 4th entry and is a forum from "audiokarma". The guy there is a bit digmatic and wrong in what he says about series resistance but he does have the L-pad circuit you are looking for. Try that and see if it is helpful. Good luck, Jonathan __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

24th November 2009, 09:53 PM	#6
Godzilla diyAudio Member Join Date: Nov 2005 Location: New York	Here is some information i put together based on my experience with piezos... Piezo Super Tweeter I like them and use them often in most, but not all, of my projects. Hope it helps. Godzilla __________________ www.zillaaudio.com/bib/bib.asp www.ZillaAudio.com

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24th November 2009, 07:42 PM	#3
Ling Gowa diyAudio Member Join Date: Aug 2009 Location: Barrie, Ontario	What happens when you put a resistor on the positive?

24th November 2009, 08:50 PM	#5
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	IIRC,Motorola suggests a small resistance in series with their piezo tweets,forget the exact reason why though.

24th November 2009, 09:55 PM	#7
Ling Gowa diyAudio Member Join Date: Aug 2009 Location: Barrie, Ontario	Now that's well done info. Thanks.

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