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Author Topic: HP filter really needed?  (Read 5497 times)

Ivan Beaver

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Re: HP filter really needed?
« Reply #50 on: July 08, 2016, 07:01:20 pm »

Did somebody say phase?  Wait, I've heard of that.

When two frequencies collide, what's out of phase here is in phase there.  And maybe a few degrees less over there.

Gimmie a beat!

Phasers set to stun captain.

 :) :)
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Chris Grimshaw

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Re: HP filter really needed?
« Reply #51 on: October 10, 2016, 06:41:32 am »

To answer the original question, I'd say you absolutely need a HP filter.

I recently destroyed a Beyma 15P1200Nd during testing, as the software was running the sweeps an octave past what I asked it to do (turns out its in the manual, who knew?). Set for 30Hz-100Hz sweep. Cabinet is a 1/4-wave transmission line that tunes to the mid-30s. Push the levels up for a high-power sweep and bam, 500w+ of 15Hz sine. The driver is rated for (and manages) 52mm p/p travel before damage, which was very impressive to watch. The cone got itself some fold lines and had to be reconed, to the tune of over 100.

Sure, the phase will go wonky at the bottom of the passband, adding a little group delay (the audibility of which is contested). Better than your bass going to mush because the kick drum port puts out a poof of air at infrasonic frequencies and you haven't set a simple filter. Or maybe someone will drop a mic. Whatever. Its not worth the risk.

Chris
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Ivan Beaver

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Re: HP filter really needed?
« Reply #52 on: October 10, 2016, 08:24:12 pm »


Sure, the phase will go wonky at the bottom of the passband, adding a little group delay (the audibility of which is contested). Better than your bass going to mush because the kick drum port puts out a poof of air at infrasonic frequencies and you haven't set a simple filter. Or maybe someone will drop a mic. Whatever. Its not worth the risk.

Chris
It is all mater of compromise.  It is real easy to get "hung up" on the little "perfections" and then destroy the loudspeaker.

Often having the speaker live to play another day is more important than somebody being happy with a proper "alignment".
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

John Halliburton

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Re: HP filter really needed?
« Reply #53 on: October 11, 2016, 09:09:09 am »

Below port tuning or horn loading the driver is no longer damped by the enclosure meaning it operates as if it was out of the box hanging in free air and could be driven to it's mechanical limits with relatively little power, so if you want to keep your drivers functional you would be well advised to always have a low cut/high pass filter engaged.

Not entirely true.  The Orbit Shifter has a sealed rear volume for the driver, so there is always some physical resistance to cone motion below resonance. 

Best regards,

John
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Art Welter

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Re: HP filter really needed?
« Reply #54 on: October 11, 2016, 11:16:27 am »

Not entirely true.  The Orbit Shifter has a sealed rear volume for the driver, so there is always some physical resistance to cone motion below resonance. 

Best regards,

John
John,

The operative word is "some", which is the same air spring as expected from a small rear chamber, same as any sealed sub. If you measure it's distortion below Fc, you will notice the excursion rapidly exceeds Xmax with far less than full power, though not quite as badly as a TH or BR below Fb.

Art
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Jim McKeveny

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Re: HP filter really needed?
« Reply #55 on: February 01, 2017, 05:35:05 pm »

That may be all well and good, but at midnight on a Saturday-what am I going to do to get new drivers in the cabinets to play till 2am?

IIRC the late, great M.L. Procise once said: "BAD sound beats NO sound every time"
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