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Call me crazy but I'm not running a high pass filter on my DS21 with an inuke 3k bridged to it. I don't think the driver can be bottomed out. I think Data-bass confirmed this but not 100% sure. As the voice coil moves farther out of the gap, the motor has less power over it, which along with the restrictions from the suspension creates a situation where the cone simply cannot move far enough to crush the former. It will however probably sound like crap flopping around at 10hz.
 

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Discussion Starter #62
Call me crazy but I'm not running a high pass filter on my DS21 with an inuke 3k bridged to it. I don't think the driver can be bottomed out. I think Data-bass confirmed this but not 100% sure. As the voice coil moves farther out of the gap, the motor has less power over it, which along with the restrictions from the suspension creates a situation where the cone simply cannot move far enough to crush the former. It will however probably sound like crap flopping around at 10hz.
Is this ported too? I don’t know much about this stuff but this was also somewhat my impression. If you have any more information or data on this I’m all ears! I’ll set a HPF since my receiver seemingly can do it, but I would like to set it so I can still get some of these low frequencies
 

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Call me crazy but I'm not running a high pass filter on my DS21 with an inuke 3k bridged to it. I don't think the driver can be bottomed out. I think Data-bass confirmed this but not 100% sure. As the voice coil moves farther out of the gap, the motor has less power over it, which along with the restrictions from the suspension creates a situation where the cone simply cannot move far enough to crush the former. It will however probably sound like crap flopping around at 10hz.
I'm with ya - I'm running a 14hz HPF on my 18hz mini-Marty's (18" LaVoce's on a NX6k) just because at that point, it's just flopping around like a fish out of water - I don't have enough power to bottom the driver which is fine by me - it lets me beat on them like they owe me money :D
 

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Mine is ported, 12 cubic feet roughly 20hz.

Some reading from databass:

Quote from DB:
The driver produced heavy distress and distortion noises in the deep bass during this sweep and was clearly way beyond its linear excursion envelope. One take away from this is that the 21DS115-4 driver seems to be nearly impossible to mechanically bottom.

Souce for that quote:
 

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Discussion Starter #65
Mine is ported, 12 cubic feet roughly 20hz.

Some reading from databass:

Quote from DB:
The driver produced heavy distress and distortion noises in the deep bass during this sweep and was clearly way beyond its linear excursion envelope. One take away from this is that the 21DS115-4 driver seems to be nearly impossible to mechanically bottom.

Souce for that quote:
Very interesting! Why would it sound like crap at 10hz though? Because 10hz generally sounds like crap, or because this system isn't really made for it?
 

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Because the voice coil was out of the gap and the distress noises caused by the surround and suspension.


Sent from my iPhone using Tapatalk
 

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And cone excursion is just slightly touching xmax at 10hz. This makes me infer that a HPF is not needed as long as I am not playing the 10hz frequency around 110dB.
Ah ok.

There are a couple of more things to consider though:

- The excursion plots are for single frequencies, and the excursions requirements are at least somewhat additive; fully additive if the waveform peaks of two freq's coincide in time

- You might not hit xmax, but the closer you get the higher the distortion.

- Driving the sub at any freq below which it can produce useful output is a waste of excursion and amp headroom and needlessly increases distortion, compression, and the probability of clipping.
 

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I wonder what distortion sounds like below 15hz. I mean we can't hear 15hz right? At that point it's just shaking the floor and walls, and I'm not sure what the distortion of a shaking floor feels like. I realize driver noise and port noise are worth caring about, but the distortion that modeling software or a measurement mic indicate at 15hz doesn't matter to me if I can't hear it.

Now if you're driver can smash it's former on the back plate or pull the cheap glue apart at 20mm, then sure a high pass filter is necessary. Otherwise what are we worried about?
 

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I don’t have one set up for my NSW’s. I think the only time I drove them to distortion was forgetting about the beginning of EOT.


Sent from my iPhone using Tapatalk
 

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No not at 10hz. 110dB at 60hz. The way I modelled was to see where the peak of 110dB is going to be reached. And it's being reached at 60hz with 50w input power.

Sent from my GM1917 using Tapatalk
But what db of output are you getting at 20hz, 30hz, etc? Seems like you'd be not flat and missing out on a lot of low end the way you have it set up, no?
 

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Discussion Starter #74
How do high pass filters work? Let's say I decide to put in place a HPF at 20hz with a 16db per octave slope. This means that I get full volume at 20hz and then 10hz would be 16db quieter, correct?

My question is: does this apply only to max volumes, or to all volumes? Like if I am listening to something quiet, is all 10hz content quieter? or does the filter only apply at the highest volumes?
 

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Discussion Starter #76
You can approximate the effect in your model when you add the filter in
was this reply for my question? I don't know what you mean by model since I am not modeling anything. My question is more of a general question since I don't know when HPFs "turn on". Is it always at any level, or only when approaching max levels or reference or what?
 

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Discussion Starter #78
Not exactly; most HP filters are down some number of dB (differs w/filter type and order), and aren't at full attenuation slope at the nominal freq.
Maybe I’m not understanding sorry. If my receiver is at max level, does the HPF have the same impact as if I’m at -40db? Like if 10hz reduced by the same relative amount (eg 18db)
 

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I don't know when HPFs "turn on". Is it always at any level, or only when approaching max levels or reference or what?
Forgot to address that; standard filters work at all levels.

More sophisticated DSP processing, such as powered subs and outboard DSP processors, have dynamic processing that varies the level at which filtering starts, and/or the the nominal HP freq.
 

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I don't believe so. Please see measurements below. See the top line. It's reasonably flat. Excellent output. View attachment 3095841
[/QUOTE]

Huh, interesting. I was assuming going off your model on the last page, it looks like you're down 10db at 20hz compared to at 60hz. Doesn't show up here though. Maybe if you kept increasing the output level to a 110db sweep instead of 80bd it would? I dunno just guessing
 
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