My first Sub Sim with W8-740P

[will_raymo2000]

Hi,

Only just started playing around with WinISD, although have been reading lots recently about it.

I inputted all the T/S params into WinISD for the TB W8-740P and was playing around with vented, closed, bandpass enclosures but settled on a Vented enclosure. I played around with the enclosure volume size etc until I got a nice freq response. F3 at 35hz and 207hz (which I assumed was ok for a subwoofer?)

However looking at the impedance graph for the driver it has two huge peaks. First peak at 20.7Hz at 64ohms and then a dip then second peak at 46Hz at 39ohms. Is this normal?!

Finally, is the transfer function magnitude graph the overall freq response of the box?

Thanks!

[will_raymo2000]

After some more playing and reading I have come up with (what I think, for a beginner) is quite a decent design.

The group delay worries me slightly as I have read that a higher group delay causes a loose base sound. I think the SPL looks good for 50w but the speaker can take a lot more grunt according to the datasheet. I have simulated at Linkwitz 4th order at 150hz but plan to have a variable crossover on the final build.

The dimensions I worked out is 12" by 12" by 20". The port is 1" x 12" and is just over 28" long. Internal volume is just over 1ft^3 or 30L.


Opinions/improvements?

[chris661]

Originally Posted by will_raymo2000

Hi,

Only just started playing around with WinISD, although have been reading lots recently about it.

I inputted all the T/S params into WinISD for the TB W8-740P and was playing around with vented, closed, bandpass enclosures but settled on a Vented enclosure. I played around with the enclosure volume size etc until I got a nice freq response. F3 at 35hz and 207hz (which I assumed was ok for a subwoofer?)

However looking at the impedance graph for the driver it has two huge peaks. First peak at 20.7Hz at 64ohms and then a dip then second peak at 46Hz at 39ohms. Is this normal?!

Finally, is the transfer function magnitude graph the overall freq response of the box?

Thanks!

Yes, the impedance peaks are normal. A decent solid state amplifier simply won't care if they're there.
A valve amplifier (ones with high output impedance) will care, and tend to interact more with the impedance curve leading to... Unexpected results.

Looking at the last sim window you posted, it looks to me that the cabinet is a little too large: there's a peak in output around port tuning, which you can get rid of simply by losing a litre or two.
The transfer function is the frequency response of the driver. You can add other drivers and the program will attempt to match the driver sensitivities to directly compare the bass response. I tend to use the SPL chart, as this takes power input and driver sensitivity into account - more useful, IMO in comparing drivers.

Chris