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Old 17th November 2011, 10:20 PM   #1
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Default Question About Appropriate Amp Power For Sub

i was not sure if this should be in the amp or sub section, so moderators, please move if this is incorrect.

i'm working on my first DIY sub project and have arrived at a few nice options - if WinISD is representative of response in my room. regarding appropriate amplification power - in determining how much power to look for in an amp, i am using the 'System Input Power' field in the 'Signal' tab and adjusting until i am just under the Xmax on the 'Cone Excursion' graph.

i am actually surprised at how little power i can use before exceeding the drivers Xmax... in a few scenarios it's far less than the rated power handling of the driver - as low as 150 Watts.

i commonly read about 1kW amps used in subs, so am wondering if i'm going at this the wrong way and misinterpreting what WinISD is indicating.

any advice on using WinISD to determine the correct amp output would be appreciated.
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Old 17th November 2011, 10:33 PM   #2
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What kind of sub are you building, ported, sealed etc. ? It sounds like you are doing it right (WINisd).
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Old 17th November 2011, 10:40 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

In WinISDpro you will quickly realise for a 1KW sub you need to choose the
bass driver very carefully and probably need to apply loads of bass boost
to get the thermal limit near the excursion limit at low frequencies.

You can EQ a driver with fixed volume displacement, excursion x cone area
to any frequency response you like. Given that, the frequency response in
box only determines how much power you need for the EQ, you make the
box smaller, you need more power for the same response, so you can
trade off reducing box size up to the power handling limit of the driver.

Unfortunately I don't think WinISDpro takes into account any bass boost
actively applied in most graphs, only the frequency response / excursion.

rgds, sreten.
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Last edited by sreten; 17th November 2011 at 10:43 PM.
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Old 17th November 2011, 10:42 PM   #4
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two small sealed subs... either a single down firing 10" driver (TC Sounds Epic 10 or Acoustic Elegance AV10H if they become available) in a 14.5 L (0.51 ft3) enclosure or dual opposed side firing 8" drivers (TC Epic 8 or Funky Waves 8) in a 16.2 L (0.57 ft3) enclosure. those enclosure volumes are my best estimate at internal volumes.

even with the relatively large Xmax specs for these drivers, the max input i can use before exceeding the Xmax on the Epic 10 is 280 Watts and on the dual 8's it's 350 Watts. i was pretty surprised at these results.
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Old 17th November 2011, 10:48 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by srosenberg View Post
even with the relatively large Xmax specs for these drivers, the max input
i can use before exceeding the Xmax on the Epic 10 is 280 Watts and on
the dual 8's it's 350 Watts. i was pretty surprised at these results.
Hi, so make them smaller and EQ, you will get higher power handling, but no more SPL, rgds, sreten.
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Old 17th November 2011, 10:49 PM   #6
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here's a screen shot showing the Cone Excursion, Eq and Input Power for the TC Epic 10. any more than 280 Watts, and I'm well past the Xmax. If i remove the Linkwitz Transform, i can use more power... trade-offs!

Does this mean I should not buy an amp that puts out more that 280 Watts? If yes, if the QSC RMX 850 a nice option?

-Scott
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Old 17th November 2011, 10:50 PM   #7
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I'll model them and see if I get the same results. But they sound right, 280-350w is a lot of power.
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Old 17th November 2011, 10:53 PM   #8
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Quote:
Originally Posted by revboden View Post
I'll model them and see if I get the same results. But they sound right, 280-350w is a lot of power.
I tried to upload the WinISD file i'm using for this particular driver but the file type is not supported.
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Old 17th November 2011, 10:53 PM   #9
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aah. look at the 'Amplifier apparent load power' under 'system overall'
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Old 17th November 2011, 10:57 PM   #10
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by srosenberg View Post
here's a screen shot showing the Cone Excursion, Eq and Input Power for the
TC Epic 10. any more than 280 Watts, and I'm well past the Xmax. If i
remove the Linkwitz Transform, i can use more power... trade-offs!

Does this mean I should not buy an amp that puts out more that 280 Watts?
If yes, if the QSC RMX 850 a nice option?

-Scott
Hi,

I don't think WinIsDpro models this properly, for a given box and driver
max power for the excursion limit is independent of any EQ applied.

So choose box size for amp power needed for max SPL standard sealed,
and then ignore the subsequent results for EQ, they are wrong AFAICT.

rgds, sreten.
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Last edited by sreten; 17th November 2011 at 11:02 PM.
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