SDA SRS 3.1 MW6503 T/S Vas of 3.0 ft^3

freak1942
freak1942 Posts: 10
edited May 2010 in Troubleshooting
I am interested in the SDA SRS 3.1, want to make a replica of these boxes.
The relationship Vas of the 5 units against Vb boxvolume is not understood by me.
With panel thicknes of 20 mm the calculated netto box volume is 128 liter, minus drivers/pass radiator 121 liter.
Five drivers with stated Vas of 3.0 ft^3 or 84 liter, gives 420 liter.
It looks the box volume is too small, or am I overlooking something?
How can this work? (hundreds of them are sold to great succes)
Assuming the Vas of one speaker should be less or equal the Vb boxvolume for ideal working and low frequency bass.
After extensive research I found the VIFA PLW18 225/8SE a good replacement.
Fs= 29 Hz
Qms= 1.7
Qes= 0.32
Qts= 0.27
Sd= 150cm2
Vas= 68L
Cms= 2.2
Mms= 14g
Rms= 1,5
B.L= 6.6
Xover at 2kHz
Sens=90.6dB
(Price $140 in europe)

Who is shining some light in this matter
Regards freak1942
Netherlands
Post edited by freak1942 on
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Comments

  • Ricardo
    Ricardo Posts: 10,636
    edited May 2010
    Can you repeat the question please????
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  • ben62670
    ben62670 Posts: 15,969
    edited May 2010
    The way they get away with it is by using the passive to tune it.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • dubradio
    dubradio Posts: 181
    edited May 2010
    Freak,

    The reason for the smaller volume than what you would expect is due to the inclusion of the passive radiator, this allows for internal air expansion and thus we were able to utalize a smaller cabinet volume. The passive radiator also gives the driversmore dynamic bottom end when compared to a sealed cabinet. By allow the air to expand and contract is a very controled fashion by way of the passive radiator, we were able to give the speaker greater low end bass response without the less accurate response that a ported enclosure offers.
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  • freak1942
    freak1942 Posts: 10
    edited May 2010
    Thanks very much Kyle and Ben.
    It should have something to do with the pass. woofer, did not realised that directly, this is a Learning curve for me, with uppercase L.
    A vent port does not come insight, a calculation comes to a ridiculous result.
    That's why the pass. radiator, which should be one octave below Fbox I believe.
    This wisdom comes from the book of "Vance Dickason"

    The 12" PR of Dayton, SD315-PR, has Fs of 16.8 Hz, is 15Hz better ?
    PR Mms is 200g
    PR Cms is 0.45
    Vas is 480, this looks to low, read somewhere, double the surface of the 5 drivers total, comes to 680g ??
    A 15" PR will not fit the enclosure.

    For the PR Mms my humble calculation came out with a total mass of 250g for the SRS 3.2
    Formula found; Mmp=35.5 x Sdp^2 divided by Fb^2 x Vb results in 250g.

    For stuffing the box I found something in the SDA 1 upgrade papers.
    This is for short I know or not know, there is much to be absorbed, nevertheless a nice hobby

    Regards Laurens
    Netherlands
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