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Old 7th May 2009, 06:53 PM   #3351
GM is offline GM  United States
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Quote:
Originally posted by AndrewT
10 to 80Hz is three octaves...........that will be massive.
Yeah, just calculating a theoretical 15" driver suitable for a ~3:1 CR to save time yields a ~913 L net cab which once damped should cover at least three octaves at reasonable efficiency:

GM
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Old 7th May 2009, 08:18 PM   #3352
Josh Ricci is offline Josh Ricci  United States
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Hey GM I notice that you and also HornsKeith used slightly different parameters for the LMS driver in your simulations. Any reason for this in particular?

Unless there is something better I will start looking at determining the folding scheme and general cabinet design for the 600L version I posted earlier. This should be fun...
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Old 7th May 2009, 09:06 PM   #3353
GM is offline GM  United States
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I always input the basics and let HR calculate/optimize as required since even measured specs can be off if for no other reason than the measurement program can have some different constants such as air mass (po) and speed of sound (SoS) than the simming program.

GM
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Old 7th May 2009, 10:17 PM   #3354
MaVo is offline MaVo  Germany
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Default Re: Impulse Response

Quote:
Originally posted by tb46
Hi MaVo,

I found this Wikipedia article informative:

http://en.wikipedia.org/wiki/Impulse_response

Regards,
Thanks tb46. The article speaks of measured impulse responses which can reveal where the speaker differs from the ideal model. Yet, i asked about a simulated impulse response, where all the artefacts that this article refers to wont be in.

To my knowledge, every impulse response shows a rise and fall before and after the spike, which are there because the speaker is allways a bandpass system. Then you have the small irregularities which can be identified with frequency response bumps. Basically, one can translate from one to the other, only that the frequency response shows the data in a more usefull manner.

Or did i miss something?
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Old 8th May 2009, 03:11 AM   #3355
tb46 is offline tb46  United States
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Default Impulse Response

Hi MaVo,

It is my understanding, that in a frequency response plot you are looking at two curves: 1. magnitude, and 2.phase.

The impulse response displays the reaction of a system to a stimulus against time, and the aspects of the frequency response can be derived from this reaction. The impulse response shows the relative magnitude and arrival times of the pressure wave(s) as well as the reflections and ringing produced by chambers, ducts and horns in the time domain, something I don't think you can get from the SPL and phase response bode plots.

I'm more than willing to confess, that the math involved is well out of my range, and thus I have to refer you to the reams of information on the net. Just chasing down some of the references in the wikipedia article has my head hurting. :-) Basically, I look at it as one more wrench in the tool box.

I'll attach a number of Hornresp impulse response curves for the MCM 55-241 in 1 cubic foot enclosures: closed, bass-reflex, front-loaded horn and tapped horn. I cannot get the same information from frequency response curves, and am trying to understand what it means in reference to subwoofers and particularly tapped horns.

Regards,
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Old 8th May 2009, 03:13 AM   #3356
Josh Ricci is offline Josh Ricci  United States
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Quote:
Originally posted by GM
I always input the basics and let HR calculate/optimize as required since even measured specs can be off if for no other reason than the measurement program can have some different constants such as air mass (po) and speed of sound (SoS) than the simming program.

GM

What do you consider the basics? I've always considered BL, RE, MMS, to be the most concrete parameters driver to driver. Vas, Q's,FS and the like float around substantially.
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Old 8th May 2009, 08:35 AM   #3357
MaVo is offline MaVo  Germany
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Hi tb46, now i see what you mean. Indeed an interesting thing, those impulse responses
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Old 8th May 2009, 10:33 AM   #3358
layertone is offline layertone  United States
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Quote:
Originally posted by layertone



I will certainly chime in with some photos soon with my Lab12. I'm using 3/4" apple ply. Decided to use a 12x14x1/2" Green edge clear acrylic for a driver access panel (also able to see the lab12)

Thanks

I'm chiming in as promised!!!

http://www.diyaudio.com/forums/showt...hreadid=143714
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Old 8th May 2009, 02:10 PM   #3359
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by GM
calculating a theoretical 15" driver suitable for a ~3:1 CR to save time yields a ~913 L net cab which once damped should cover at least three octaves at reasonable efficiency:
2100 sq cm of mouth area in a FLH will never get flat response down to 10Hz, even with corner loading.
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Old 8th May 2009, 02:18 PM   #3360
AndrewT is offline AndrewT  Scotland
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Default Re: Impulse Response

Quote:
Originally posted by tb46
The impulse response displays the reaction of a system to a stimulus against time, ,
Am I reading the displays correctly?
The closed box gives best response.
The reflex is less good and out of phase.
The tapped horn is the worst.
Why all the ripples and delayed decay from the font loaded horn?
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