Subsonic filter for my sub?

[cameron paterson]

I have an XLS 2502 Crown amp pushing my sub. Its tuned at 20hz. Would like a subsonic filter with the extra power of the amp. A cheap subsonic filter but not the little harrison plugs that go with the rca.

 

[lovinthehd]

Minidsp.com has devices you can use

 

[everettT]

the crown has a high pass filter in the eq settings fwiw.

 

[lovinthehd]

the crown has a high pass filter in the eq settings fwiw.

Not that low of one, hpf in the xls is for xover use, not one low enuf for his sub.

 

[cameron paterson]

anything cheaper than the minidsp stuff?

 

[KEW]

It looks like there is a fixed 6dB/octave HP filter at 20Hz hard wired into the Crown Drivecore pro amps:
http://techtalk.parts-express.com/forum/tech-talk-forum/1325083-crown-xls-1502-subsonic-filter-confirmed

6dB/octave is not very aggressive and I could see that room gain might offset it, if room gain exists at subsonic frequencies, but at least the signal being sent to drive the subwoofer has reduced power for the lower frequencies.

 

[KEW]

I have an XLS 2502 Crown amp pushing my sub. Its tuned at 20hz. Would like a subsonic filter with the extra power of the amp. A cheap subsonic filter but not the little harrison plugs that go with the rca.

You didn't define cheap, but here is a $180 solution:
http://www.kabusa.com/frameset.htm?/accesss.htm

Crap, their website will not allow me to link to a specific product!
Use the link above and scroll down to the bottom of the items being sold (with prices listed).
Look at "KAB Great Sound Escorts (Active)" and find RF-1 (Rumble filter)

SPECIFICATIONS

• -3dB @ 20 Hz 18dB/Oct
• Unique Active Vertical Cancellation below 140 Hz
• Dual Voltage Regulation
• Output 5 Vrms
• THD <0.05%
• Noise -95dB
• Dimensions 4.5" x 3" x 1.25"
• Shipping Weight 4 Lbs
• Power: 24VDC,0.75A Meanwell GE18I24-P1J

But before you spend money, there is some relevant information on the product page:

But the main source is feedback exciting the natural stylus/arm resonance between 7 and 12 hz. This produces a slow easily visible in and out motion of your woofers. If you cannot see this motion, the RF-1 will not solve your feedback problem. If you can see this motion, the RF-1 will solve your feedback problem.
And with rumble eliminated, the soundstage becomes more "still" and the bass actually tightens up because the woofers are no longer modulating and the power amp is no longer wasting current resources on sub audible noise.

If you driver is not moving around without producing sound, I'm not sure you have a problem! Setting a lit candle in front of the speaker is a good way to detect driver motion from the LP.

I do not know this product, but it seems to be a competent solution. I'd imagine there are several choices in the rumble filter category, and generally, they should offer exactly what I think you want: aggressive roll-off of subsonic frequencies (added to the 6dB/octave you already have)!

 

[everettT]

Did you not install the dayton plate amp?

 

[cameron paterson]

I sold the Dayton plate amp and now have the XLS Crown.

 

[Alex2507]

It looks like there is a fixed 6dB/octave HP filter at 20Hz hard wired into the Crown Drivecore pro amps:
http://techtalk.parts-express.com/forum/tech-talk-forum/1325083-crown-xls-1502-subsonic-filter-confirmed

6dB/octave is not very aggressive and I could see that room gain might offset it, if room gain exists at subsonic frequencies, but at least the signal being sent to drive the subwoofer has reduced power for the lower frequencies.

You probably mean infrasonic ... and why wouldn't room gain exist? ... and why doesn't it exist at higher frequencies? Where's the cut off and why is there a cut off?

 

[KEW]

You probably mean infrasonic ... and why wouldn't room gain exist? ... and why doesn't it exist at higher frequencies? Where's the cut off and why is there a cut off?

Subsonic?, infrasonic?. My Sansui integrated had a "subsonic filter" which was labeled 14Hz, so I am used to calling it subsonic (and the OP called it a subsonic filter in the title). I remember watching my woofers move in and out (large excursions) without making a sound. When I flipped the switch I could rarely see them move much at all.
Room gain probably does exist at the lower frequencies, but you wouldn't hear it; but I don't know that for certain, so I said "if it exists"
Data-Bass has some good info! Here is a plot of room gain for a specific scenario:

And here is link to rest of article!
https://data-bass.com/data?page=content&id=80

 

[Alex2507]

Subsonic?, infrasonic?. My Sansui integrated had a "subsonic filter" which was labeled 14Hz, so I am used to calling it subsonic (and the OP called it a subsonic filter in the title). I remember watching my woofers move in and out (large excursions) without making a sound. When I flipped the switch I could rarely see them move much at all.
Room gain probably does exist at the lower frequencies, but you wouldn't hear it; but I don't know that for certain, so I said "if it exists"
Data-Bass has some good info! Here is a plot of room gain for a specific scenario:

And here is link to rest of article!
https://data-bass.com/data?page=content&id=80

Kinda cool the way room gain works for <12Hz. It's also cool how sub 2 fixes sub 1 but sub 3 effs 'em both only to be further remedied by sub 4. You know what that means. I need 2 more subs.

 

[TheWarrior]

and why doesn't it exist at higher frequencies? Where's the cut off and why is there a cut off?

Wavelength! The Transition Frequency changes room to room, but it is the point at which bass stops being omni directional and gains forward bias as frequency increases.

20 hz = 56.5 feet in diameter
80 hz = 14.1 feet in diameter
120 hz = 9.4 feet in diameter
20 khz = 0.56 inches in diameter

When you have giant sound waves interacting with an enclosed space, it mostly induces room modes and standing waves between parallel boundaries, some call that 'Room Gain' (Resonance was used in the article).

But as frequency increases, the wavelength gets smaller at which point 'Room Gain' is really more an issue of 'Room Treatment' and how many reflective surfaces you have.

None of which is really the rooms fault, just naturally occurring phenomena that has to be dealt with in any sound reproducing system!

 

[lovinthehd]

Wavelength! The Transition Frequency changes room to room, but it is the point at which bass stops being omni directional and gains forward bias as frequency increases.

20 hz = 56.5 feet in diameter
80 hz = 14.1 feet in diameter
120 hz = 9.4 feet in diameter
20 khz = 0.56 inches in diameter

When you have giant sound waves interacting with an enclosed space, it mostly induces room modes and standing waves between parallel boundaries, some call that 'Room Gain' (Resonance was used in the article).

But as frequency increases, the wavelength gets smaller at which point 'Room Gain' is really more an issue of 'Room Treatment' and how many reflective surfaces you have.

None of which is really the rooms fault, just naturally occurring phenomena that has to be dealt with in any sound reproducing system!

Wavelengths expressed in diameter?

Article on the Schroeder frequency https://www.soundandvision.com/content/schroeder-frequency-show-and-tell-part-1

 

[TheWarrior]

Wavelengths expressed in diameter?

Article on the Schroeder frequency https://www.soundandvision.com/content/schroeder-frequency-show-and-tell-part-1

How else would you express the length of a 3D wave?

 

[KEW]

How else would you express the length of a 3D wave?

Linear distance of one full cycle?

 

[lovinthehd]

How else would you express the length of a 3D wave?

I think wavelength pretty much covers it.

 

[Alex2507]

How else would you express the length of a 3D wave?

seven fifths