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getafix 10th October 2003 01:50 AM

help interpreting graph
2 Attachment(s)
plugged some figures in Unibox and came out with this graph for a vented enclosure:

kelticwizard 10th October 2003 04:11 AM

You have two Tang Band 4 inchers in a ridiculously large enclosure, tuned far too high. That is why you have the huge peak just before cutoff.

Since there are 28.3 Liters in 1 Ft³, this enclosure is 5.3 Ft³! That is big enough to fit a 15 incher into, instead of two 4 inchers.

I suggest either a sealed box with 13 Liters, or a ported box with 19 liters tuned to 50 Hz.

See if the dark blue line doesn't look better. That is, a flat line all the way down, untiil it turns downward for the cutoff.

getafix 10th October 2003 04:50 AM

2 Attachment(s)
i tried to change the volume in Unibox... didn't know that I could do that :)...

anyway, the graph looked much better... is this basically the shape that one has to achieve whenever designing vented or sealed enclosure?

wintermute 10th October 2003 09:10 AM

That looks much better. I usually play around for a while until I get something pretty flat, with as low a 3db point as possible without compromising the flatness too much. It's interesting to change things like the port length, or box volume, just to see how it afects things.

Have fun :)



Vikash 10th October 2003 09:51 AM

Don't forget that appropriately coloured red line cutting through the graph! This show that the drivers have reached max linear excursion (xmax) at ~175Hz. So at 80w input, flattening out the bottom octaves by changing box volume, tuning etc. makes no difference.

Alter the power handling figure until you find a point where the red line does not intersect with the black line within the required range (or using the second Unibox graph might be easier - peak cone excursion graph).

wintermute 10th October 2003 12:45 PM

Good point Vikash. As I found out before, that point can be surprisingly low too!

getafix 12th October 2003 12:52 AM

thanks for the info... i'll try to modify some of the figures later

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