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Author Topic: JBL SRX715 Not Over Impressed  (Read 9619 times)

Dennis Wiggins

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Re: JBL SRX715 Not Over Impressed
« Reply #40 on: February 07, 2013, 12:35:11 pm »

Reply #2

You have to mount the cabinets so that the HF horn is at least 1 foot above the patrons heads.  Any lower, and the HFs will be blocked by those closest to the speakers.  You will get no penetration.  It is a fallacy (mostly) that you will get "more bass" by putting them on the floor.  What you are really doing is blocking the highs, not increasing the lows, causing you to turn up the HFs.  Subs make great, stable, speaker stands.  Don't leave home without them.

-Dennis
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Dennis Wiggins

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Re: JBL SRX715 Not Over Impressed
« Reply #41 on: February 07, 2013, 12:43:19 pm »

Reply #3

If your source material is MP3s, I cannot help you any further.  MP3s have no useable bass, very distorted midrange, and extremely distorted highs; all due to the extreme compression.   Further compression by DSP limiting just makes it worse.  The output appears (on a 'scope), and sounds, like the output of a square wave generator.  Look up the effects of square waves and driver diaphragm failures.

Google this:  square waves tweeter failures

-Dennis
« Last Edit: February 07, 2013, 12:53:42 pm by Dennis Wiggins »
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Jay Barracato

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Re: Re: JBL SRX715 Not Over Impressed
« Reply #42 on: February 07, 2013, 02:36:49 pm »

Reply #3

If your source material is MP3s, I cannot help you any further.  MP3s have no useable bass, very distorted midrange, and extremely distorted highs; all due to the extreme compression.   Further compression by DSP limiting just makes it worse.  The output appears (on a 'scope), and sounds, like the output of a square wave generator.  Look up the effects of square waves and driver diaphragm failures.

Google this:  square waves tweeter failures

-Dennis

A audio myth that refuses to die. Transducers are killed by heat or over excursion. Compressing the signal has no effect until you raise the volume to compensate for the gain reduction. A compressed signal has a higher average energy compared to peak volume. This equates to heat. The shape of the signal is meaningless.
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Jay Barracato

Dennis Wiggins

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Re: Re: JBL SRX715 Not Over Impressed
« Reply #43 on: February 07, 2013, 02:41:12 pm »

...Compressing the signal has no effect until you raise the volume to compensate for the gain reduction. A compressed signal has a higher average energy compared to peak volume. This equates to heat...

That was exactly my point. 

We are trying to solve this fellow's dilema from the operator's POV; not the transducer's.

Perhaps I should have stated that an MP3 further comressed will "approach" the shape of a square wave.  A more technical term might be a "high duty cycle" waveform.

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

I think that we are talking about the same thing.

-Dennis
« Last Edit: February 07, 2013, 02:58:23 pm by Dennis Wiggins »
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Jay Barracato

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Re: Re: Re: JBL SRX715 Not Over Impressed
« Reply #44 on: February 07, 2013, 03:14:34 pm »

That was exactly my point. 

Perhaps I should have stated that an MP3 further comressed will "approach" the shape of a square wave.  Better?

-Dennis

The shape doesn't matter, and even if it did, at the extreme situation the transducer does not follow the same wave pattern as the input. The transducer still has to deaccelerate, stop, and then accelerate every time it changes direction. Since this cannot happen instantaneously the transducer may not follow the electrical signal.

A square wave with less energy than the speaker can convert to motion and heat is perfectly safe. A perfect sine wave with more energy than the speaker can convert to motion and dissipate as heat will destroy the speaker.

I see this as a simple conservation of energy problem. The shape of the wave is really meaningless (especially given the complexity of a true musical signal, as opposed to the simpler models we tend to think about). All waves regardless of shape transfer energy. This just comes down to how much.
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Jay Barracato
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