How would these settings affect my HPF? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 17 Old 05-01-2019, 08:44 AM - Thread Starter
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How would these settings affect my HPF?

Subsonic Filter
Selects a subsonic filter with -3dB @ 18Hz, Q=.8.

Bass Boost
Selects a bass boost filter with +3dB @ 25Hz, Q=1.4.

EQ
The freq. knob selects the frequency for the filter,
the bandwidth knob selects how wide or narrow the filter is
(the higher the bandwidth, the broader the effect), and the
level knob can be used to add up to 6dB of boost or 14 dB
of cut.


If I had the above subsonic filter set at 18Hz, but then also EQ boosted at the lowest setting (same, 18Hz), to the max +6b & widest Q=1 bandwidth, what will the effective cutoff be then? I'm particularly interested in knowing if possible how far down that would put me at 16hz.
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post #2 of 17 Old 05-01-2019, 09:07 AM
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What equipment is being used to apply these settings? Are you unable to apply the settings as a test and measure the response?

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post #3 of 17 Old 05-01-2019, 10:11 AM
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So I modeled a ported UM18 and applied the filtering (Red). I'm getting an F3 of about 12.8Hz. Green is without filters.
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post #4 of 17 Old 05-01-2019, 10:26 AM - Thread Starter
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Quote:
Originally Posted by johnson636 View Post
What equipment is being used to apply these settings? Are you unable to apply the settings as a test and measure the response?
Sorry I should have clarified- these are settings on a subwoofer amplifier I'm thinking about buying. Only problem is its subsonic filter is a little higher than I'd prefer.

Just curious if boosting at the hpf frequency and the bass boosted well compensate at all, or will it completely neuter the sub in the teens
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post #5 of 17 Old 05-01-2019, 10:28 AM - Thread Starter
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Quote:
Originally Posted by Funkeye View Post
So I modeled a ported UM18 and applied the filtering (Red). I'm getting an F3 of about 12.8Hz. Green is without filters.
Very cool, thank you! That looks perfect

Edit - in fact from the looks of that graph it might be overcompensating, for 1200w on a 16hz tuned sub could be trouble in low teens. Might dial the boostand q down a little.

Last edited by Leon!; 05-01-2019 at 10:49 AM.
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post #6 of 17 Old 05-01-2019, 10:41 AM
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Quote:
Originally Posted by Funkeye View Post
So I modeled a ported UM18 and applied the filtering (Red). I'm getting an F3 of about 12.8Hz. Green is without filters.
You should check your excursion and port velocity
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post #7 of 17 Old 05-01-2019, 11:05 AM
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Quote:
Originally Posted by notnyt View Post
You should check your excursion and port velocity
Excursion was good until 300W and port velocity can be tamed with huge ports (4 x 4" x 26"). The box would be huge as well. I only did the model to see how the filter settings affected response without emphasis on the system. Of course the driver specifics were not mentioned in the OP.

Last edited by Funkeye; 05-01-2019 at 11:21 AM.
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post #8 of 17 Old 05-01-2019, 11:20 AM - Thread Starter
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Quote:
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Quote:
Originally Posted by notnyt View Post
You should check your excursion and port velocity
Excursion was good until 300W and port velocity can be tamed with huge ports (4 x 4" x 26"). The box would be huge as well. I only did the model to see how the filter settings affected response without emphasis on the system. Of course the driver specifics were mentioned in the OP.
Box is already built, 14cf net with 8"dia. X 35 1/2" port. Just using a PE spa250dsp, which I assume is < 250watts, it's already as much output as I desire, and doesn't start making undesirable noises until I hit right at 8hz, which happens in quite a few movies.

So I have to get a HPF, Just if I'm having to buy a stand alone eq or DSP, I'd just assume get a more powerful amp with it onboard. Especially want to play it safe with 1000 more watts, mid teens would be great.
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post #9 of 17 Old 05-01-2019, 11:22 AM
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Quote:
Originally Posted by Leon! View Post
Box is already built, 14cf net with 8"dia. X 35 1/2" port. Just using a PE spa250dsp, which I assume is < 250watts, it's already as much output as I desire, and doesn't start making undesirable noises until I hit right at 8hz, which happens in quite a few movies.

So I have to get a HPF, Just if I'm having to buy a stand alone eq or DSP, I'd just assume get a more powerful amp with it onboard. Especially want to play it safe with 1000 more watts, mid teens would be great.
What driver?
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post #10 of 17 Old 05-01-2019, 11:26 AM - Thread Starter
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Quote:
Originally Posted by Funkeye View Post
Quote:
Originally Posted by Leon! View Post
Box is already built, 14cf net with 8"dia. X 35 1/2" port. Just using a PE spa250dsp, which I assume is < 250watts, it's already as much output as I desire, and doesn't start making undesirable noises until I hit right at 8hz, which happens in quite a few movies.

So I have to get a HPF, Just if I'm having to buy a stand alone eq or DSP, I'd just assume get a more powerful amp with it onboard. Especially want to play it safe with 1000 more watts, mid teens would be great.
What driver?
Ultimax 18"
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post #11 of 17 Old 05-01-2019, 11:52 AM
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Quote:
Originally Posted by Leon! View Post
Ultimax 18"
Lucky guess!


Quote:
Originally Posted by Leon! View Post
Box is already built, 14cf net with 8"dia. X 35 1/2" port..... want to play it safe with 1000 more watts, mid teens would be great.
High pass = 18 Hz, 0.8Q
EQ = @18Hz, Q=1, Gain=1
Power = 1000W
Port velocity = 18.7 m/s
Excursion = 22.4mm
F3 = 16.1 Hz


Anything I'm missing?
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post #12 of 17 Old 05-01-2019, 01:05 PM - Thread Starter
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Quote:
Originally Posted by Funkeye View Post
Quote:
Originally Posted by Leon! View Post
Ultimax 18"
Lucky guess!


Quote:
Originally Posted by Leon! View Post
Box is already built, 14cf net with 8"dia. X 35 1/2" port..... want to play it safe with 1000 more watts, mid teens would be great.
High pass = 18 Hz, 0.8Q
EQ = @18Hz, Q=1, Gain=1
Power = 1000W
Port velocity = 18.7 m/s
Excursion = 22.4mm
F3 = 16.1 Hz


Anything I'm missing?
Haha yeah I was wondering how you already knew.


Edit- no you're not missing anything, it is a 1000 w amp, thank you!

All of that looks good though, excursion and velocity?

Last edited by Leon!; 05-01-2019 at 01:21 PM.
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post #13 of 17 Old 05-01-2019, 01:19 PM - Thread Starter
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So that's with the level knob turned to 1 right?

That graph looks so awesome, and safe. Thanks so much for taking the time to do that for me.
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post #14 of 17 Old 05-01-2019, 08:03 PM - Thread Starter
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Ordered the amp! Thanks all, now feel confident I can still push high output into the teens without damaging my driver thanks to Funkeye's work.


Super excited, greatly appreciated.

Last edited by Leon!; 05-01-2019 at 08:07 PM.
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post #15 of 17 Old 05-06-2019, 01:26 PM - Thread Starter
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Quote:
Originally Posted by Funkeye View Post
So I modeled a ported UM18 and applied the filtering (Red). I'm getting an F3 of about 12.8Hz.


Green is without filters.

Quote:
Originally Posted by Funkeye View Post
Lucky guess!




High pass = 18 Hz, 0.8Q
EQ = @18Hz, Q=1, Gain=1
Power = 1000W
Port velocity = 18.7 m/s
Excursion = 22.4mm
F3 = 16.1 Hz


Anything I'm missing?

I stuffed a removable chimney in the end of my port, to temporarily experiment with 16hz vs. 14hz tune... think I'm safe with the amp settings you provided that resulted in an f3 of 12.8Hz, using that 14Hz extension, or still should keep the gain lower? It looks like the only thing that changed between each combination of settings you calculated, is with the EQ, from "Gain = 6" (12.3Hz) to "Gain = 1" (16.1Hz).

So far with only 250w I think I prefer the 16hz tune, but the 1,000w amp arrives wednesday.

(I shoved this tube extension with the foam in the end of my port):






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post #16 of 17 Old 05-06-2019, 08:40 PM
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It looks like the only thing that changed between each combination of settings you calculated, is with the EQ, from "Gain = 6" (12.3Hz) to "Gain = 1" (16.1Hz).
The "Gain=6" model was not with your box. It was auto-generated from WinISD, and very large in size, much larger than yours. Ignore this one.

The "Gain=1" model was based on your box, port dimensions, and power requirements you specified.
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post #17 of 17 Old 05-08-2019, 02:46 PM - Thread Starter
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IDK how much outut I'm losing in the low teens, going from 16hz tune with a 250w amp with no HPF, to a 14hz tune with 1,000w amp but also 18hz HPF (+ the Gain 6/Q1.0 EQ boost also at 18hz), but the latter still seems much more impactful down low. ALso it no longer makes any unwanted output in certain super low bass heavy scenes that I'd known to happen without a HPF, even with only 250w.

Anyway feel like its perfect now, does not seem like I'm leaving too much on the table down low with the HPF.
Very impressed with this amp.

Last edited by Leon!; 05-09-2019 at 12:53 PM.
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