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Old 8th May 2009, 05:25 PM   #3361
GM is offline GM  United States
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Quote:
Originally posted by Josh Ricci

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.
T/S specs since HR doesn't use Mms.........

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Old 8th May 2009, 05:48 PM   #3362
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Quote:
Originally posted by AndrewT
2100 sq cm of mouth area in a FLH will never get flat response down to 10Hz, even with corner loading.
Well, given a small enough Vb underground bunker I imagine it could, but it's academic because I didn't claim it would/could and AFAIK it would be useless anyway in any typical HIFI or HT app.

Regardless, unless the BW limits are defined as 'flat', then they are normally considered tuning frequencies, so my theoretical driver sim has a 10 Hz fundamental as shown and once damped should have at least a three octave usable ~flat BW based on my TL/pipe horn experience (not to mention DSL's and geitmans's measured responses as a frame of reference) and ~four octave tuning BW. I'd add that this assumes that HR is accurate enough, but I believe it's proven itself to be 'close enough' for the basic gain BW portion of its predictions that we can dispense with this disclaimer if the build mirrors the design input.

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Old 8th May 2009, 06:19 PM   #3363
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Default Re: Re: Impulse Response

Quote:
Originally posted by AndrewT
Am I reading the displays correctly?

Why all the ripples and delayed decay from the font loaded horn?
Yes.

Real world horn designs are almost always misaligned/compromised WRT the driver's specs to meet the needs of the intended app, so you get various throat, mouth distortions that cause reflections, pressure wave variations back to the driver if not damped as Dr. Geddes (foam insert) and/or Peavey (mouth foam surround) recommends. An optimized horn will have an impulse response that's 'close enough' to the driver's IB one and a compression horn's will be considerably better overall since its effective Qtc will be lower than the driver's Qts.

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Old 8th May 2009, 06:35 PM   #3364
JLH is offline JLH  United States
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Default Re: Re: Impulse Response

Quote:
Originally posted by AndrewT
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?

That tapped horn needs more work. Look at the impulse response of one of my tapped horns.

http://www.diyaudio.com/forums/showt...83#post1820883

Rgs, JLH
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Old 8th May 2009, 07:42 PM   #3365
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Default Impulse response

H Y'all,

The impulse response simulations in Post #3355 are for the same driver in equal net volume enclosures, all 1cft. They are not optimized examples of their respective class, but should suffice for this comparison as their responses appears typical.

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Old 8th May 2009, 11:28 PM   #3366
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Default Re: Impulse response

Quote:
Originally posted by tb46
H Y'all,

The impulse response simulations in Post #3355 are for the same driver in equal net volume enclosures, all 1cft. They are not optimized examples of their respective class, but should suffice for this comparison as their responses appears typical.

Regards,

A fronthorn should look more like this.
-One large peak and a delayed small one.
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Old 9th May 2009, 12:45 AM   #3367
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Hi electroaudio,

I posted an actual FLH example with build reference in Post #3340.

Regards,
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Old 9th May 2009, 01:38 AM   #3368
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Default JLH's B&C 8PE21 TH

Hi there JLH: The simulation for the 30hz TH shows he flattest frequency responce on the thread, which would cover the lowest note played by the piano (27.4hz) and cover the other orchestral bass instruments: string double bass, cello, bass clarinet, tuba, etc, this performance would be great for my listening. Did you post: a diagram, dimensions and does it use one or two B&C 8PE21's? What are your music listening observations of this TH? You have gotten a lots of laughs at our house from your "banned from the house" comments. .....regards, Michael
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Old 9th May 2009, 08:38 AM   #3369
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Quote:
Originally posted by tb46
Hi electroaudio,

I posted an actual FLH example with build reference in Post #3340.

Regards,

That looks normal.
I have to say that i really liked the words you used in post 3355 , but i just had to comment that the FLH was too odd to be called typical.

-I would have guessed bandpass.
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Old 9th May 2009, 10:39 AM   #3370
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Default Re: step response

Quote:
Originally posted by mwmkravchenko
The greatest difference between a SPL graph and a step graph is the information conveyed in the ability of the driver system/enclosure to reproduce a transient. The sharper the rise and fall the "quicker" the system. This is a function that is very dependant on voice coil inductance.

The ringing after the impulse are the box and driver trying to fall to a rest position. Obvious less is more here to.

Properly applied it is a very revealing test. It is akin to the resistance graph where all the wiggles relate to some kind of non-linearity.

I'm on a job site right now. But when I get home I'll post Joe D'Apollito's thoughts from his book on measureing loudspeakers.

What I know I learned from him!

Mark
There's a direct relationship between the amplitude/phase response and the impulse response of any loudspeaker, one is the FFT/IFFT of the other.

Anything which causes peaks in the frequency response (like an enclosure resonance) will cause ringing in the impulse response, which is generally undesirable but may or may not be audible.

Sharper rise/fall time simply means more HF bandwidth, and what limts the bandwidth (enclosure, voice coil inductance) makes little or no difference. For subwoofers the effect of voice coil inductance on limiting the frequency response is not usually a problem in itself, this happens well above the crossover frequency.

The real problem with high voice coil inductance is not so much that it limits bandwidth, but that it often varies greatly as the cone moves. This makes the bandwidth a function of cone position, which causes amplitude modulation of higher notes by lower ones as the cone moves in and out.

A driver with high but constant inductance is no different to an external inductor in series with the driver, like in a crossover. But this is difficult (and expensive!) to realise even using massive multiple demodulating rings and/or copper pole sleeves.

Ian
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