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TDA MT121 - HR Plots
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levyte357- View Drop Down
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    Posted: 28 March 2013 at 11:40am

http://forum.speakerplans.com/simplified-mt121-plans_topic16270.html

Originally posted by levyte357 levyte357 wrote:

For those of us who weren't aware they were here.

Originally posted by Three-Bee Three-Bee wrote:




img218/8403/tdamt121gk5.jpg




Attempted plot from TDA MT121 plan,



Comments?


Edited by levyte357- - 28 March 2013 at 3:20pm
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Dref View Drop Down
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Points: 287 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Dref Quote  Post ReplyReply Direct Link To This Post Posted: 28 March 2013 at 12:51pm
Hi Lev

There will be a front chamber (Vtc) because of the shape of the cone.
Making the rear chamber smaller will improve the response.
Try and play around with the directivity function. (Ctrl+R)
A proper build subwoofer will be the only thing in a room that is not shaking.
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levyte357- View Drop Down
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Originally posted by Dref Dref wrote:

Hi Lev

There will be a front chamber (Vtc) because of the shape of the cone.
Making the rear chamber smaller will improve the response.
Try and play around with the directivity function. (Ctrl+R)


Cheers for that.

Really trying to sim TDA MT121 as is, to get realistic plot of how cab performs with various drivers.

So, what would suggested refinements to above input values be, for existing design?
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Is not hornresp only accurate up to a certain freq? If so what is that "cutoff"?
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I've just loaded mine with BMS 12N610's and 4550's on RCF HF64 horns if you fancy toying with that combo. Gonna try and get some smaart plots over this weekend incase your interested. 
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I think the rear chamber volume should be less than 20 L. As far as I can calculate from the dimensions, the rear chamber is 15.7 L in its empty state. So try with 8-10 L.

Also the constant directivity option is very unfair for such a narrow dispersion horn. Try to make an on-axis(0 degree) plot with an 8 L rear chamber and lets see how that looks.
A proper build subwoofer will be the only thing in a room that is not shaking.
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levyte357- View Drop Down
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Originally posted by Dref Dref wrote:

I think the rear chamber volume should be less than 20 L. As far as I can calculate from the dimensions, the rear chamber is 15.7 L in its empty state. So try with 8-10 L.

Also the constant directivity option is very unfair for such a narrow dispersion horn. Try to make an on-axis(0 degree) plot with an 8 L rear chamber and lets see how that looks.


Will be interesting to see real plot vs HR sim, to identify the inaccuracy.

Trying to identify best drivers for cab, then where eq will be needed to flatten response.
Some of us need exceptionally flat 200-500hz response.


Edited by levyte357- - 29 March 2013 at 12:45pm
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levyte357- View Drop Down
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Points: 8517 		Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 03 April 2013 at 11:47am
Originally posted by Dref Dref wrote:

I think the rear chamber volume should be less than 20 L. As far as I can calculate from the dimensions, the rear chamber is 15.7 L in its empty state. So try with 8-10 L.

Also the constant directivity option is very unfair for such a narrow dispersion horn. Try to make an on-axis(0 degree) plot with an 8 L rear chamber and lets see how that looks.


Done



Does this seem a little too optimistic ?
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MarjanM View Drop Down
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Yes it does.
Marjan Milosevic
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https://www.facebook.com/pages/MM-Acoustics/608901282527713
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levyte357- View Drop Down
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Originally posted by MarjanM MarjanM wrote:

Yes it does.


Hmmm..

Trying to find well suited driver, simming with parameters first..

But if sims not accurate, what then..

Some of us can't afford testing with conveyor belt of driver purchases.
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Possible to purchase test and return? I know Parts Express here lets us do that
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Something went wrong with your sim?

Here is my sim:


Try to find a driver with a lighter cone.
If it has to be a Kappa then go for the non Pro version.
A proper build subwoofer will be the only thing in a room that is not shaking.
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