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Maximize the Thump

#22
Originally posted by BillyB_from_LZ
Hey Petebass...you had suggested modeling.
Click to expand...
Me? Modelling? Have you seen what I look like? And I hate photo shoots :)

How about modeling an Eminence Kappa Pro 15LF in a BE size cabinet with and without porting (tuning freq...um I don't know how about trying 35, 40, 45 and 50 Hz).
Click to expand...

I guess we could give it a go but I don't own "Leap". That's probably the only speaker modelling program that does excursion properly. WinISD pro has excursion graphs now but they apparently don't take into account the non-linear behavior of the speaker's suspension system, so they're of no use really. I went to their online forum to ask about this and the program designer himself jumped in to help out. He basically showed me how you use the Max Power graphs to determine how many watts a speaker can take before hitting X-max and at what frequency. This gives an indication of excursion but I have no idea how he calculates it. I did ask but he ignored the question. Bgavin would probably know........

How big is a BE cabinet anyway?
 
#23
Pete...how come that Right Said Fred song is playing in my head right now?:D

Anyway, according to Bagend.com the S-15D is 18.5 by 18.5 by 15.5 inches overall. Looks like 3/4 in. thick plywood for the box and the baffle is set back 1 to 1.5 inches. From that I guess the internal volume of the box is about 2.2 cubic feet or 60 litres, not considering the volume that the driver or the port tube occupies.
 
#24
Originally posted by BillyB_from_LZ
Pete...how come that Right Said Fred song is playing in my head right now?:D
Click to expand...
For the same reason I've got the Zoolander movie playing in my head right now :)



60 litres, not considering the volume that the driver or the port tube occupies.
Click to expand...

I just used 60 litres because that'll do for the purpose of this exercise.

Have a look at the attachment. Yellow=sealed, Green=tuned to 30Hz, Orange =40Hz, Pink-50Hz.

This is the conce excursion graph I mentioined previously. I've changed the power to reflect a 600w signal going into the speaker. The white line is actually the curser but I placed it there to reflect this speakers x-max of 4.8mm.
As you can see, this graph suggests all of these cab configurations hit X-max at 173Hz at full power. We all know this speaker can go lower than that and not distort. This graph hasn't taken into account the effect of the spider and surround of the speaker in taming the speakers excursion.

So what is the real world distortion characteristics of this speaker? I need to show you another screenshot so I'l have to start a new post.........
 
#25
This graph shows the maximum power this speaker can handle before hitting x-max at a range of frequencies.

As you can see all of these cab configurations can handlw 600w of power and not distort up to 115Hz (better than the 173Hz suggested by the other graph). At frequencies below that, it takes less watts to hit x-max. If you're pumping the full 600w into this speaker, you could hit problems below 115Hz.

The worst performer of the ported cabs seems to be the cab tuned to 30Hz, distorting at a mere 197W at 60Hz. Tuning to 40Hz get you 240watts at 70Hz. Tuning to 50Hz get you 297W at 80Hz.

But how does this affect frequency response?

New graph - newpost..........
 
#26
All three cab configurations net a similar -3dB point of about 100Hz. The the differences are evident in the frequencies below that.

As I suggested in the beginning of the thread, the lower the tuning of the cab, the more area under the curve.

So which one produces more thump? Why are you asking me? I like it punchy :)
 

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