Help modifying the BASH 500 amp.. - AVS Forum
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post #1 of 8 Old 06-06-2012, 01:52 PM - Thread Starter
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A friend of mine recently purchased the BASH500 amp and we want to modify the high-pass filter to 17 or 18hz. I know its the R17 and R18 resistors, just don't know what to change them to.

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post #2 of 8 Old 06-06-2012, 02:25 PM
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Is this what you are looking for?

http://www.parts-express.com/pdf/300-752.pdf
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post #3 of 8 Old 06-06-2012, 02:29 PM - Thread Starter
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So is "bass boost" the same as a hi-pass filter? I just need to know which resistors to use to make the cutoff 17hz or 18hz.

In terms of LFE, size does matter!
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post #4 of 8 Old 06-06-2012, 03:15 PM
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No, they aren't. I misread your post, sorry!
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post #5 of 8 Old 06-06-2012, 04:28 PM
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Quote:
Originally Posted by Favelle View Post

So is "bass boost" the same as a hi-pass filter? I just need to know which resistors to use to make the cutoff 17hz or 18hz.

The link provided is the correct one.

The BASH500 amp offers both a signal boost and a high-pass filter, depending on the resistor values.

If your friend purchased the amp from parts-express recently the amp might already have the HPF you want, as a couple of commentors on the site indicate the default HPF is now between 17-18Hz. (see quote below)

Comment from parts-express.com
"The new resistor values on the PE BASH 500w (or at least the resistors that were on my recently purchased amp) are: R17: 25,000 Ohm R18: 68,100 Ohm. These are much more useful that the old values for most DIY projects. The new Fc = 17.36 Hz; Q= .817; Boost peak is at about 35 Hz with a gain of .28 dB; Gain at Fc = -1.75dB"

If your friend's amp doesn't already have these values, you can use the Fc column of the referenced PDF tables to find the correct values. Given you want approximately 18Hz cutoff, you could use the R17=20 and R18=75 for a HPF cutoff of 18.7Hz and a 1dB boost at approximately 27.5Hz (as seen in the 1dB boost table). You could also try the values posted by the commentor, although I'm not sure if the Fc, Q, and boost have been confirmed for those values.
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post #6 of 8 Old 06-06-2012, 07:06 PM - Thread Starter
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Quote:
Originally Posted by dboff01 View Post

The link provided is the correct one.
The BASH500 amp offers both a signal boost and a high-pass filter, depending on the resistor values.
If your friend purchased the amp from parts-express recently the amp might already have the HPF you want, as a couple of commentors on the site indicate the default HPF is now between 17-18Hz. (see quote below)
Comment from parts-express.com
"The new resistor values on the PE BASH 500w (or at least the resistors that were on my recently purchased amp) are: R17: 25,000 Ohm R18: 68,100 Ohm. These are much more useful that the old values for most DIY projects. The new Fc = 17.36 Hz; Q= .817; Boost peak is at about 35 Hz with a gain of .28 dB; Gain at Fc = -1.75dB"
If your friend's amp doesn't already have these values, you can use the Fc column of the referenced PDF tables to find the correct values. Given you want approximately 18Hz cutoff, you could use the R17=20 and R18=75 for a HPF cutoff of 18.7Hz and a 1dB boost at approximately 27.5Hz (as seen in the 1dB boost table). You could also try the values posted by the commentor, although I'm not sure if the Fc, Q, and boost have been confirmed for those values.

Thanks! What is the benefit of the "bass boost"? Why would someone choose 1dB over 4dB..or vice versa?

In terms of LFE, size does matter!
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post #7 of 8 Old 06-06-2012, 07:16 PM
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Quote:
Originally Posted by Favelle View Post

Thanks! What is the benefit of the "bass boost"? Why would someone choose 1dB over 4dB..or vice versa?

If you were using the amp in a sealed enclosure, you may want to boost the signal to provide a flatter response. It basically acts as a single channel of EQ capability built into the amp.

Simulator programs like WinISD Pro can be used to see the effects of boosts and filters on your frequency response when designing your own subwoofer box.
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post #8 of 8 Old 06-07-2012, 12:17 AM - Thread Starter
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Quote:
Originally Posted by dboff01 View Post

If you were using the amp in a sealed enclosure, you may want to boost the signal to provide a flatter response. It is basically acts as a single channel of EQ capability built into the amp.
Simulator programs like WinISD Pro can be used to see the effects of boosts and filters on your frequency response when designing your own subwoofer box.

Makes sense, thanks dboff0!

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