Tips for woofers/mics/amplification and impedance

freakout · 18th November 2009, 02:50 PM

Hallo everyone. I'm currently working on a couple of projects and i've
got several doubts regarding amplification and impedance. long story short:
i have a DYH-810 8'' woofer and i'm trying to understand what kind of amp should i connect, and that is where understanding impedance really comes into play. Since the woofer is 4OHM, i suppose i should connect an amp with an output impedance which is LOWER than that, am i correct? this statement comes because i used a small tube amp which i have, which has an output impedance of 51OHM and the efficiency of the woofer was *really* poor. also: i've got a number of contact mics(piezo discs) and for another project i have to use one as a mic and one in output, as a sortof speaker. so question is: what kind of amplification should i use for the "output contact mic" and for the "input contact mic", so to speak? should i always follow the low-to-high impedance combination? thanks in advance guys

thermal runaway · 18th November 2009, 04:48 PM

Regarding the speaker , as long as the spec of the amp states that the impedance range is from 4 ohms you won't have a problem. Valve amps are different , they have an output transformer and it's important the speaker connected matches the output impedance of the transformer. Some valve amp transformers have a number of impedance taps so that the speaker can be matched.

Can't help you with the mics , never did much with them.

PeteMcK · 20th November 2009, 12:09 AM

A piezo mic will need a high input impedance, of the order of 1 megohm.
some info on using them as out devices:
Lynn and Steve's Piezo page

Enzo · 20th November 2009, 07:42 AM

A 51 ohm output? I have never seen that. Printed on it, or did you determine that somehow? Keep in mind resistance and impeance are not the same.

freakout · 20th November 2009, 10:58 AM

PreSonus

go in "tech specs" and it shows it, assuming that i understand the thing correctly...i'm also using this tube pre for piezos, sometimes, and it doesnt work too bad.

18th November 2009, 02:50 PM	#1
freakout diyAudio Member Join Date: Nov 2009	Tips for woofers/mics/amplification and impedance Hallo everyone. I'm currently working on a couple of projects and i've got several doubts regarding amplification and impedance. long story short: i have a DYH-810 8'' woofer and i'm trying to understand what kind of amp should i connect, and that is where understanding impedance really comes into play. Since the woofer is 4OHM, i suppose i should connect an amp with an output impedance which is LOWER than that, am i correct? this statement comes because i used a small tube amp which i have, which has an output impedance of 51OHM and the efficiency of the woofer was really poor. also: i've got a number of contact mics(piezo discs) and for another project i have to use one as a mic and one in output, as a sortof speaker. so question is: what kind of amplification should i use for the "output contact mic" and for the "input contact mic", so to speak? should i always follow the low-to-high impedance combination? thanks in advance guys

20th November 2009, 12:09 AM	#3
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Western Sydney	A piezo mic will need a high input impedance, of the order of 1 megohm. some info on using them as out devices: Lynn and Steve's Piezo page __________________ Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency

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18th November 2009, 04:48 PM	#2
thermal runaway diyAudio Member Join Date: Mar 2007 Location: West Mids , UK	Regarding the speaker , as long as the spec of the amp states that the impedance range is from 4 ohms you won't have a problem. Valve amps are different , they have an output transformer and it's important the speaker connected matches the output impedance of the transformer. Some valve amp transformers have a number of impedance taps so that the speaker can be matched. Can't help you with the mics , never did much with them.

20th November 2009, 07:42 AM	#4
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	A 51 ohm output? I have never seen that. Printed on it, or did you determine that somehow? Keep in mind resistance and impeance are not the same.

20th November 2009, 10:58 AM	#5
freakout diyAudio Member Join Date: Nov 2009	PreSonus go in "tech specs" and it shows it, assuming that i understand the thing correctly...i'm also using this tube pre for piezos, sometimes, and it doesnt work too bad.