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Re: More on time alignment. Wayne? [message #3671 is a reply to message #3659]

Thu, 31 August 2006 10:11

Wayne Parham
Messages: 18680
Registered: January 2001

Illuminati (33rd Degree)

I'm saying use of the phrase "time alignment" is a marketing ploy. It is not an accurate way to describe what is being accomplished with proper driver placement and crossover design. Baffle position is important, and tilting the baffle is one way to set position that can also be aesthetically pleasant. But the use of the phrase "time alignment" has always been marketing rhetoric.

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Links to articles about phase related issues [message #3673 is a reply to message #3668]

Thu, 31 August 2006 10:56

Wayne Parham
Messages: 18680
Registered: January 2001

Illuminati (33rd Degree)

I did a few searches here and in the other speaker forums on ART for posts about "phase", "time alignment" and other related things. Here are a few of the threads I found:

Intermodulation, phase and Doppler distortion, and then some, π Speakers forum post containing several links to discussions about phase related issues
Time Alignment - Horn/Compression & Woofer, High-Efficiency Speaker forum thread about physical alignment
Can't reproduce a square wave, Speaker forum thread about what happens when a square wave is sent to a loudspeaker
Bandpass subs, High-Efficiency Speaker forum thread with references to transient response and group delay
Blind testing and what I would like to see done..., General forum thread with references to phase-related issues

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Thanks I will check them out. NT [message #3675 is a reply to message #3673]

Thu, 31 August 2006 12:02

Mr Vinyl
Messages: 407
Registered: May 2009

Illuminati (1st Degree)

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Re: More on time alignment. Wayne? [message #3679 is a reply to message #3671]

Thu, 31 August 2006 15:24

GarMan
Messages: 960
Registered: May 2009

Illuminati (2nd Degree)

Wayne, I think one of the issues is that there are different people are using the term "time alignment" in different ways and nobody's bothering to ask what each other means.

My take is that time alignment is possible WITHIN limited ranges of the frequency range and is neccessary for smooth FR. With current driver technology, time alignment is not possible throughout the entire FR.

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Re: More on time alignment. Wayne? [message #3681 is a reply to message #3679]

Thu, 31 August 2006 17:47

Wayne Parham
Messages: 18680
Registered: January 2001

Illuminati (33rd Degree)

The thing is, the companies that boast loudly about "time alignment" usually use it as a way to set themselves apart and I think that's disingenuous. It has always appeared like sales rhetoric to me, since the companies that make an issue of it are doing nothing different than others loudspeaker manufacturers. Their "alignment" is no better than anyone else's - It is a 1/4λ match perhaps but certainly not a true zero phase alignment. So to use the term to set themselves apart smacks of marketing mumbo-jumbo to me.

For decades, most every loudspeaker manufacturer has taken steps to match the subsystems for proper summing. Altec recommended a simple procedure to match the HF and LF drivers in the crossover region back in the 1960's and then revisited it with an application note (link below) in the 1980's. This phase matching is done for summing, to reduce the amount of destructive interference. The idea is to prevent two adjacent drivers from cancelling each other through their band of overlap, causing a spiked dip in response. A frequency response anomaly is what you'll hear if there is a problem with summing, not the time offset.