Mic impedance: my brain hurts... at DVinfo.net

Al Osmond · October 26th, 2002, 02:41 PM

My mind goes blank when I try to get my head round microphone impedances. Could some sound engineer please help with this one?

Using an XL1s with MA200, I have tried connecting a camera-mounted Sennheiser MKE300 into one channel and a fishpole-mounted Sennheiser K6/ME67 into another, hoping to use the balance control to match the levels.

Alas, while the K6 gives excellent audio, the MKE300 always produces a significantly lower level.

Belatedly (?) studying the specifications I find that the K6 is nominally 200 Ohm (Minimum terminating impedance 1K Ohm), while the MKE300 is 2K Ohm, (suitable for 2K7 Ohm systems).

Is this the source of the problem? I am aiming to buy a second K6, maybe with a short module, for use on the camera. The MKE300 doesn't inspire any confidence in its robustness; it feels like a plastic toy. In fact, when the battery expires I will have to throw it away as the plastic cap refuses to unscrew and will probably snap off as soon as force is applied. If anyone wants it I will throw it in their direction. :)

Al

Don Palomaki · October 30th, 2002, 06:04 PM

Nominal impedance of the ME66/K6 and the MKE300 are both 200 ohms, so impedance is not an iimmediate issue. However, the recommended terminating impedance can be an issue - because the XL1/MA200 is a 600 ohm load, the MKE300 will run out of gas a lot earlier with high sound levels than the K6/ME66 combo, and the increased loading may cause changes its frequency response from the nominal specification.

More to the point the ME66/K6 combo has a rated output of on the order of 50 mV/Pa while the MKE300 is more like 16 mV/Pa, about 10 dB less. This is probably the main reason for your inbalance. The low frequency roll off of the MKE300 may add to a thinner sound too.

The MKE300 is marketed as a consumer camcorder mic, not as a professional product.

Are you tossing the MKE300 for free?

Al Osmond · November 1st, 2002, 10:06 AM

Don, thanks for that!

I didn't have, or couldn't find, the specs for both mics to make a complete comparison. The main reason for the imbalance certainly seems to be the difference in output.

The MKE300, as you say, does have a noticeably thinner sound but the most obvious difference is in the audio level.

As for tossing the MKE300, since it only weighs about two ounces I doubt if I could toss it more than twenty yards, let alone as far as Northern VA. :) But once it has been replaced with something more suitable, I think I'll let it go to a good home.

Al

Don Palomaki · November 2nd, 2002, 07:21 AM

You can find the PDF version of the spec sheet for both at the www.sennheiserusa.com web site. Go to products->microphones->specialty for the MKE3000 and ->K6 for the ME66. You have to burrow down a bit further to find he PDF spec sheet, which is more complete (and accurate) than the quick tech data on the web page.

Al Osmond · November 2nd, 2002, 07:31 AM

Thanks again!

I just took a look at the USA site as opposed to the plain cooking international version, which is a less friendly site. Downloaded all the relevant PDFs and a few irrelevant ones besides.

All looks like excellent bathroom reading... :)

Al

October 26th, 2002, 02:41 PM	#1
Al Osmond Regular Crew Join Date: Jun 2002 Location: Thame, United Kingdom Posts: 42	Mic impedance: my brain hurts... My mind goes blank when I try to get my head round microphone impedances. Could some sound engineer please help with this one? Using an XL1s with MA200, I have tried connecting a camera-mounted Sennheiser MKE300 into one channel and a fishpole-mounted Sennheiser K6/ME67 into another, hoping to use the balance control to match the levels. Alas, while the K6 gives excellent audio, the MKE300 always produces a significantly lower level. Belatedly (?) studying the specifications I find that the K6 is nominally 200 Ohm (Minimum terminating impedance 1K Ohm), while the MKE300 is 2K Ohm, (suitable for 2K7 Ohm systems). Is this the source of the problem? I am aiming to buy a second K6, maybe with a short module, for use on the camera. The MKE300 doesn't inspire any confidence in its robustness; it feels like a plastic toy. In fact, when the battery expires I will have to throw it away as the plastic cap refuses to unscrew and will probably snap off as soon as force is applied. If anyone wants it I will throw it in their direction. :) Al

October 30th, 2002, 06:04 PM	#2
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,487	Nominal impedance of the ME66/K6 and the MKE300 are both 200 ohms, so impedance is not an iimmediate issue. However, the recommended terminating impedance can be an issue - because the XL1/MA200 is a 600 ohm load, the MKE300 will run out of gas a lot earlier with high sound levels than the K6/ME66 combo, and the increased loading may cause changes its frequency response from the nominal specification. More to the point the ME66/K6 combo has a rated output of on the order of 50 mV/Pa while the MKE300 is more like 16 mV/Pa, about 10 dB less. This is probably the main reason for your inbalance. The low frequency roll off of the MKE300 may add to a thinner sound too. The MKE300 is marketed as a consumer camcorder mic, not as a professional product. Are you tossing the MKE300 for free?

November 1st, 2002, 10:06 AM	#3
Al Osmond Regular Crew Join Date: Jun 2002 Location: Thame, United Kingdom Posts: 42	Don, thanks for that! I didn't have, or couldn't find, the specs for both mics to make a complete comparison. The main reason for the imbalance certainly seems to be the difference in output. The MKE300, as you say, does have a noticeably thinner sound but the most obvious difference is in the audio level. As for tossing the MKE300, since it only weighs about two ounces I doubt if I could toss it more than twenty yards, let alone as far as Northern VA. :) But once it has been replaced with something more suitable, I think I'll let it go to a good home. Al

November 2nd, 2002, 07:21 AM	#4
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,487	You can find the PDF version of the spec sheet for both at the www.sennheiserusa.com web site. Go to products->microphones->specialty for the MKE3000 and ->K6 for the ME66. You have to burrow down a bit further to find he PDF spec sheet, which is more complete (and accurate) than the quick tech data on the web page.

November 2nd, 2002, 07:31 AM	#5
Al Osmond Regular Crew Join Date: Jun 2002 Location: Thame, United Kingdom Posts: 42	Thanks again! I just took a look at the USA site as opposed to the plain cooking international version, which is a less friendly site. Downloaded all the relevant PDFs and a few irrelevant ones besides. All looks like excellent bathroom reading... :) Al