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Old 5th August 2011, 01:25 AM   #141
djk is offline djk
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A note about a high Q filter.

I just built four 35hz PPSL for PA. The 6th order Q=2 filter needed was done inside a DBX 234 crossover. The DBX comes with a 40hz filter with two 0.15F caps with a 19.6K (R5, R15) and a 39.2K (R6, R16) resistor. Changing these to 7.5K and 121K respectively gives 35hz with a Q=2.

I could have done the same thing with the 50hz filter in the DBX 231 EQ, or the bass amp with its 30hz/50hz filter.

Another way to do it with a DSP crossover is to set the filter to 35hz, and then use 9dB of boost with a Q=2 35hz EQ. The filter is -3dB at 35hz, so the result is 6dB or total boost (not the 9dB you dialed in).
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Old 5th August 2011, 07:41 PM   #142
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Quote:
Originally Posted by djk View Post
A note about a high Q filter.

I just built four 35hz PPSL for PA. The 6th order Q=2 filter needed was done inside a DBX 234 crossover. The DBX comes with a 40hz filter with two 0.15F caps with a 19.6K (R5, R15) and a 39.2K (R6, R16) resistor. Changing these to 7.5K and 121K respectively gives 35hz with a Q=2.

I could have done the same thing with the 50hz filter in the DBX 231 EQ, or the bass amp with its 30hz/50hz filter.

Another way to do it with a DSP crossover is to set the filter to 35hz, and then use 9dB of boost with a Q=2 35hz EQ. The filter is -3dB at 35hz, so the result is 6dB or total boost (not the 9dB you dialed in).
A while back I checked out the response of my DBX 223 crossover with the 40 Hz HP engaged.

The curve looks like what a 24 dB per octave slope should until about 10 Hz.

Though it would provide adequate protection for most musical sources, the rising response below 10 Hz could be a problem with dropped needles and some sound effects etc.

Did you happen to check the response of your DBX 234 before and after modification?
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Old 5th August 2011, 09:04 PM   #143
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The below 10hz problem is the bypass switch circuit for the filter, if you remove R24, 21 it behaves as it should.
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Old 7th August 2011, 08:47 PM   #144
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The below 10hz problem is the bypass switch circuit for the filter, if you remove R24, 21 it behaves as it should.
Interesting, why would DBX put in R24, 21 when it makes the below 10hz problem ?
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Old 8th August 2011, 01:11 AM   #145
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I don't know, it makes no sense to me. I can send you the schematic if you need it.
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Old 8th August 2011, 08:04 PM   #146
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Default Which woofer for hifi?

djk: May I ask which woofer you would prefer for a pair of PPSL bass bins:

1. Eminence Kappa LF-2, or

2. The Martin Sound Pro, order #1844 (see link) that I know you have used before?

The application is for hifi (not PA).

Thanks a lot!

Best regards
Peter
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Old 10th August 2011, 11:21 PM   #147
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For hi-fi?

Probably the #1844 tuned to around 27hz.
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Old 11th August 2011, 08:11 AM   #148
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For hi-fi?

Probably the #1844 tuned to around 27hz.
Hi djk,

Thanks a lot!

Best regards
Peter
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Old 12th August 2011, 07:18 PM   #149
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Originally Posted by jdubs View Post
djk, the whole cabinet rotated 90 degrees as shown in your second pic vs. your first pic. I just need something that is taller than it is wide and rotating your entire cabinet design 90 degrees accomplishes this.

Not sure how the plans would change other than adding the brace in the port.

Thanks,
Jim
EAW has a cabinet similar to the ones in the second picture.

EAW: FR250z

18 sound has a design like this also
Eighteen Sound Kits

how do these designs differ in sound compared to having the drivers mounted in a slot?

also 18 sound shows a dual 18 bandpass
Eighteen Sound Kits.

on a good note, i have some money saved for new drivers. just don't know whether to build a 4 taped horn cabinets or 2 PPSL cabinets.
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Old 13th August 2011, 11:30 AM   #150
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I’m ready to make some more sawdust!
Thanks to Les Hudson comments about “this is the best sounding subwoofer that I’ve ever heard” I will be making a ppsl subwoofer. And thanks to DJK, I will be making it per the cut sheet on post 115. The only difference is I want the port on the bottom as per the pic on post 10. Don’t know if the Eminence Kappa Pro-15lf-2 15” is the “best” or not but it should be good enough for my future surround sound. Being a newby, I am not sure what a Q=2 filter at 35hz is or what people say tuned to around 27hz means.

I have about five sheets of 5*5 baltic birch that I was going to use for a Klipsch clone but the ppsl looks far simpler to build and may even sound better.
So if anyone has any tips, comments feel free. And DJK, if you have the time I would appreciate it if you could upload a cut sheet so my sub will look like Les’s sub wuth the port on the bottom. If not I am certain I will muddle thru the build.

Regards,

jea
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