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Author Topic: Interesting woofer response  (Read 513 times)

Len Zenith Jr

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Re: Interesting woofer response
« Reply #10 on: October 19, 2018, 03:33:53 pm »


Correction: The shortest baffle dimension is actually 21.5 in. Pretty close. I should try extending the baffle and see if the step moves.

That would be a very definitive way of determining the response anomaly. The equation I gave is a very rudimentary way of determining baffle step frequency, which is more of a range than a step. You would have to integrate every infinite point on your cone with the distance to every infinite point on every edge of your baffle to get a better result. All while taking into account the volume of the box that takes away from the space. Rounded baffle edges behave differently than sharp ones, etc, etc.

The baffle step is the whole reason many home speakers have 1 tweeter and 2 woofers. While the top woofer plays its whole passband, the bottom woofer only plays from the baffle step down which adds 6dB down there to flatten the response.
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Frank Koenig

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Re: Interesting woofer response
« Reply #11 on: October 19, 2018, 05:55:45 pm »

That would be a very definitive way of determining the response anomaly.

I tried to do a quickie experiment using Smaart and its automagical windows but there are just too many reflecting surfaces anywhere around here. I need to wait until I get set up in a good measurement environment. I'll report back. Thanks for the help. -F
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Roland Clarke

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Re: Interesting woofer response
« Reply #12 on: October 22, 2018, 06:06:41 am »

Another vote for potential baffle step artefact.  Usually not a problem when people are crossing over subs around 80-100 hz.  If it were a resonance, I would expect it to be a sharper peak.
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Marcel de Graaf

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Re: Interesting woofer response
« Reply #13 on: October 22, 2018, 10:47:12 am »

Hi Frank,

Interesting topic.

I think its the baffle step. Linkwitz had investigate the baffle step in the past and well good described.

http://www.linkwitzlab.com/diffraction.htm.

In his reading there are two things going on. The baffle step AND the edge diffraction.

The baffle step isn`t part of the acoustic power (efficiency) response of the woofer. In basis it`s the acoustic dimensions that put extra forward directivity to the system. In theory a 6db/octave rise from low to high freq.

gr. Marcel
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Mark Wilkinson

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Re: Interesting woofer response
« Reply #14 on: October 22, 2018, 12:59:51 pm »



The baffle step isn`t part of the acoustic power (efficiency) response of the woofer. In basis it`s the acoustic dimensions that put extra forward directivity to the system. In theory a 6db/octave rise from low to high freq.

gr. Marcel

Yes, a change in directivity. 

Best literature I've found says the directivity increase begins when box dimension is about 1/10th wavelength, and is fully in effect when box dimension is 1/2 wavelength (potentially 6dB).
So maybe it is better described as a baffle ramp, than as a step.
I think it got the name step because once it reaches +6dB, there is no further dB rise with increasing frequency.

I guess I'd look at off-axis response for directivity changes.... vs your box dimensions,.....to try to separate natural response from any baffle step response.

 
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