Manufacturer Mmd/Mms Specs

[Robert Dunn]

Does anyone use Mmd instead of delta-mass/volume for T/S parameters? If so, how do you determine what value to use?

For example, Peerless specifies Mms and SB Acoustics specifies "Moving Mass incl. air, md" (isn't that self-contradictory?). Since neither provides details on their measurement technique, I'm not sure whether the Peerless Mms is really Mms (if so, I suppose I could calculate Mmd) or even what SBA is specifying.

[billfitzmaurice]

Re: Manufacturer Mmd/Mms Specs

Does anyone use Mmd instead of delta-mass/volume for T/S parameters? If so, how do you determine what value to use?

If you use WinISD you don't need to worry about it, the program will calculate it for you when you enter the driver data.

[feyz]

Re: Manufacturer Mmd/Mms Specs

Mms's definition is moving mass including air. Mmd is the moving mass of the moving parts of the driver only, without the air it moves. There is some air mass that moves along with the driver surface all the time, Mms includes this also.

The mass you will measure using delta-mass or volume will measure Mms, because it includes the moving mass of air.

In the box simulation programs you usually use Mms.

[fastbike1]

Re: Manufacturer Mmd/Mms Specs

In some. WBCD and Unibox don't need mms.

Mms's definition is moving mass including air. Mmd is the moving mass of the moving parts of the driver only, without the air it moves. There is some air mass that moves along with the driver surface all the time, Mms includes this also.

The mass you will measure using delta-mass or volume will measure Mms, because it includes the moving mass of air.

In the box simulation programs you usually use Mms.

[Jeff B.]

Re: Manufacturer Mmd/Mms Specs

If you use WinISD you don't need to worry about it, the program will calculate it for you when you enter the driver data.

....but then you would have to already know the Vas.

I think he's trying to find Vas.

[billfitzmaurice]

Re: Manufacturer Mmd/Mms Specs

....but then you would have to already know the Vas.

I think he's trying to find Vas.

I never considered that; when manufacturer specs are incomplete I'd expect for Mms or Mmd to be missing, but never Vas.

[Jeff B.]

Re: Manufacturer Mmd/Mms Specs

I never considered that; when manufacturer specs are incomplete I'd expect for Mms or Mmd to be missing, but never Vas.

It sounded like he was measuring T/S parameters himself, and when you do there are a couple of different ways to extract Vas from it. I think he was considering the method of entering Mms but was looking for some clarifications.

[Robert Dunn]

Re: Manufacturer Mmd/Mms Specs

It sounded like he was measuring T/S parameters himself, and when you do there are a couple of different ways to extract Vas from it. I think he was considering the method of entering Mms but was looking for some clarifications.

Thanks, guys. Jeff is correct.

Actually, I use LEAP's LTD models instead of TS-based calculations but this requires 8 or 10 measurements, half each with and without added mass, and it takes quite a while. If I had confidence in what the manufacturers are quoting, I could use that instead of the added mass measurements and cut the number of measurements in half. That would be, like, really nice.

[Pete Basel]

Re: Manufacturer Mmd/Mms Specs

Robert - I have a feeling that we might be thinking along the same lines here:

http://techtalk.parts-express.com/showpost.php?p=1806575&postcount=47

[Robert Dunn]

Re: Manufacturer Mmd/Mms Specs

Robert - I have a feeling that we might be thinking along the same lines here:
http://techtalk.parts-express.com/sh...5&postcount=47

I think so. As you note, Vance Dickason uses Mmd in VoiceCoil which is what got me started investigating. I just don't seem to find clear specs. Perhaps he gets his spec directly from the manufacturer....