Vas calculation

[didelcas]

Hi, I'm new on this forum and I was wondering if someone can help me out with the Vas calculation for a couple of woofers that belonged to my father back in the 70s and I'd like to put in use again.

The woofers are the Pioneer PW-A30
Pioneer PW-A30

The info available both online and on the original operation guide is as follows (it all seems to be presented very differently than the specs on new speakers):

Form: 30cm cone type Woofer
Impedance: 8ohm
The minimum resonance frequency (fo): 20Hz - 30Hz
Play frequency characteristic: fo-3kHz
The maximum input: 60W
Rated input: 30W
Output sound pressure level: 97dB/W/m
Cross over frequency: 3kHz or less
Qo: 0.3(fo:25Hz)
The total magnetic flux: 180,000 maxwell
Flux density: 12,000gauss
Equivalent mass: 46gr
Baffle aperture: 270phimm or 310phimm
Dimensions: Diameter 340x depth of 135mm
Weight: 6.7kghe

Additionally I've measured the speaker dimensions:

Effective cone diameter: 27cm
Mounting depth:10,5 cm
Magnet diameter: 18 cm
Magnet height:7 cm
Linear excursion: (don't know how to measure it)
Driver Displacement = 0.06 ft3

This is all the info I have about the speakers and I don't have any king of audio or electronic measuring equipment, so if someone knows how to calculate the Vas of these speakers with this numbers I'd appreaciate it very much.

Here are some pictures of the same type of speakers.

http://www.hifido.co.jp/photo/08/191/19175/d.jpg

https://auctions.c.yimg.jp/images.a...fyftk858-img600x450-1491710163cxdc7r14322.jpg

Thanks so much

Diego

 

[Lojzek]

I bet you have some kind of a sound card and even the cheapest ones are good enough to measure impedance. There is free software to measure impedance and calculate TSP. That's the easiest way to accurately find all the parameters. There is actually enough data to calculate Vas but one must assume the Fs to be between 20-30 Hz.

 

[Lojzek]

I think this computes right.

 

[didelcas]

Thank you so much Lojzek!!

 

[GM]

I think this computes right.

No clue without my Excel calculators, but was thinking using a passive radiator [PR] calculator since we have Fs, Mms, piston dia., so inputted it and Fs, then changed encl. volume [Vb] till it all worked out at 46 g = 319 L: mh-audio.nl - Home

A quick sim here matches up with the published response well enough when Qo = 0.3 Qts: mh-audio.nl - Vented System

That said, as old as the drivers are, odds are they're way out of spec now, so may be worthless.

GM

 

[Lojzek]

Mh-audio must be out of tune for the 1.unibox, 2.woofer box and circuit designer and 3.formulae that I have used from a book give the same results.

 

[GM]

Could be, again no clue without my Excel WS, so obviously can't compare to Unibox either.

GM

 

[Dave R]

Vas can be calculated from Sd, Fs, and Mms.

Vas = (rho*c^2*Sd^2)/(4*pi^2*Fs^2*Mms)

See previous results by Lojzek in post #3.

But as GM noted, the age of the drivers leaves you wondering about their condition and remaining life. Even if they are functional, actual measurements would be best.

 

[audfrknaveen]

Vas can be calculated from Sd, Fs, and Mms.

Vas = (rho*c^2*Sd^2)/(4*pi^2*Fs^2*Mms)

See previous results by Lojzek in post #3.

But as GM noted, the age of the drivers leaves you wondering about their condition and remaining life. Even if they are functional, actual measurements would be best.

Hi Dave,

Thanks a lot for the formula.
Please correct me if the below understanding is wrong ..
I guess we can take Rho as 0.5
And C is nothing but Cms

Am i right Dave ??

 

[David McBean]

I guess we can take Rho as 0.5
And C is nothing but Cms

rho = density of air = 1.205 kilograms per cubic metre.

c = velocity of sound in air = 344 metres per second.