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Amps with Adjustable Crossovers/Bi-Ampable?

#41
Actually, there are two delays one must consider: FOH (particularly mains) vs backline and FOH vs itself (mains vs subs). From what Bill Fitzmaurice states, correction with the backline has more of a sonic impact. IIRC, the DriveRack allows delay adjustment in terms of distance (feet / meters) between FOH and the backline. 1 ms per foot is about right so I run mine at 7-8 ms. Top-end is 11 ms.

The technique I described earlier can be used with some success among like enclosures when adjusting for "staggered" multiple positioning in large venues (churches, halls, etc.). This is what true pro soundguys do for a living!

Riis
 
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#42
Downunderwonder said:
you seem to confuse polarity with phase response. No assumption resides in the procedure. It works for any and all combination of reversed leads speaker wiring and phase response.

It's my conjecture that your success in flipping polarity on proven matched cabs indicates your amp or a cable was miswired.
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I have a clear understanding of the difference between phase and polarity. Phase is time based whereas polarity is not.

The amp was completely stock and all patching is internal. I performed a polarity test on both the speakers and the speaker leads. I am pretty sure it's just the design of the crossover and entirely normal. Not possible to recheck my work at this time as I accidentally shorted a test lead in the amp and released some magic smoke.

Regarding the assumption. The second step listed in the procedure above is
Zooberwerx said:
*Reverse the polarity on one of the two enclosures, not both.
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Downunder, You do realize that polarity has not been standardized in the audio industry. Attaching a battery to a speaker (matching + to + and - to -) will cause the cone of one brand to move out, and the cone of another brand to move in. How can you dispute this? Depending upon the vintage of the speakers, this can even happen within one brand. [Invalid or Expired Link Removed]
 
#43
Wasnex said:
I have a clear understanding of the difference between phase and polarity. Phase is time based whereas polarity is not.

The amp was completely stock and all patching is internal. I performed a polarity test on both the speakers and the speaker leads. I am pretty sure it's just the design of the crossover and entirely normal. Not possible to recheck my work at this time as I accidentally shorted a test lead in the amp and released some magic smoke.

Regarding the assumption. The second step listed in the procedure above is


You do realize that polarity has not been standardized in the audio industry. Attaching a battery to a speaker (matching + to + and - to -) will cause the cone of one brand to move out, and the cone of another brand to move in. How can you dispute this? Depending upon the vintage of the speakers, this can even happen within one brand. [Invalid or Expired Link Removed]
Click to expand...

Not disputing anything. The 9v test works perfectly well. I should rephrase the statement: "...once we've established the speakers are responding in identical fashion, reverse the polarity (+,-) of only one enclosure". This is fairly easy for me as I use banana plugs frequently.

As far as polarity standards, I don't have a clue...but we do have a SASE thread around here somewhere that may be able to produce a standard. That being said, I have yet to run across any line of enclosures that are purposefully or routinely wired opposite of those I've encountered.

Riis
 
#44
Zooberwerx said:
As far as polarity standards, I don't have a clue...but we do have a SASE thread around here somewhere that may be able to produce a standard. That being said, I have yet to run across any line of enclosures that are purposefully or routinely wired opposite of those I've encountered.

Riis
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I wrote
Wasnex said:
Downunder, You do realize that polarity has not been standardized in the audio industry.
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Correction..there is a polarity standard for professional speakers but there are still drivers and systems in use that do not comply. My apologies for misstating. If in doubt I suggest confirming the polarity of you speakers.
 
#45
No. The test takes care of whatever is produced. Starting out with the reverse polarity of the intended setup gives the operator an earful of cancellation which is far easier to zero in on than a summation boost. The system delay so callibrated gives the exact same end result regardless of whatever which way it was connected before being reversed.
 
#46
Downunderwonder said:
No. The test takes care of whatever is produced. Starting out with the reverse polarity of the intended setup gives the operator an earful of cancellation which is far easier to zero in on than a summation boost. The system delay so callibrated gives the exact same end result regardless of whatever which way it was connected before being reversed.
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Basically you are claiming it doesn't matter whether the speakers starts out in polarity or out of polarity. If that is the case, why bother flipping the polarity switch at all. Simply delay until you get a null. Well you can do that but it will degrade the transient response of the system somewhat. See attached.

Polarity.png
 
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#48
Downunderwonder said:
If you can hear 1/200th of a second of missing half a transient I think your ears must be way better than mine. That's 5ms.
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Don't be silly, I can't hear a 5ms delay in the start of a sine wave at 100 hz. But music is not about sine waves. I believe it's important to get the alignment right so the system performs properly across the entire crossover region and not just at the specific crossover frequency. I am not versed enough in crossover design to explain how phase varies throughout the crossover region or the impact that 5 ms of group delay might have on linearity above and below the crossover point. To be honest I believe the results vary depending upon the frequency range, the specific crossover design, as well as the drivers and cabinet tuning. All subjects that are way beyond my knowledge level. If your happy aligning your subs within 5ms, or are willing to accept errors of 30ms or more it's all good to me. Hope you have a great holiday my friend. :thumbsup:
 
#49
I don't know what linearity means but you seem to have confirmed my assertion.

Above and below the crossover point one can expect much diminishing effects with a decent slope of filter. Clear of the crossover, phase or group delay is completely immaterial.

I would expect phase response to vary far less than the crossover wrt frequency. Quid pro quo, it still doesn't matter what naked polarity you start out on when you begin the process.
 
#50
Downunderwonder said:
I don't know what linearity means but you seem to have confirmed my assertion.

Above and below the crossover point one can expect much diminishing effects with a decent slope of filter. Clear of the crossover, phase or group delay is completely immaterial.

I would expect phase response to vary far less than the crossover wrt frequency. Quid pro quo, it still doesn't matter what naked polarity you start out on when you begin the process.
Click to expand...

Here's an article on group delay you may enjoy. group_delay
 
#53
Count Bassie said:
Well. I hope you guys have gotten something enlightening out of this. No need to thank me. :D

I DO appreciate all the help and good advice, many thanks! And here's hoping your holidays are renewing and happy. Peace! Off to go hop this mess up...
Click to expand...

Well, if you understand at least 50% of what has been presented, you're far more knowledgeable than the scourge of soundguys populating CraigsList and can walk away comfortable in knowing there's more to the puzzle than volume & EQ sliders. BTW, the left-column graphics in #46 are an accurate depiction of the procedure I laid out earlier.

Riis
 
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#54
Zooberwerx said:
Well, if you understand at least 50% of what has been presented, you're far more knowledgeable than the scourge of soundguys populating CraigsList and can walk away comfortable in knowing there's more to the puzzle than volume & EQ sliders. BTW, the left-column graphics in #46 are an accurate depiction of the procedure I laid out earlier.

Riis
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I think I'm actually taking something away from this I can use. Thanks again for the helpful info and your time.
 
#57
Count Bassie said:
Yes, and I have never understood its purpose! So if I turn down the front fx send vol knob to zero, toggle that hi-pass, and send to a poweramp, only the low freqs will go there?
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I think not. Maybe yours is different but not likely.

I am pretty sure the loop is a parallel blend. Front fx knob controls fx return blend level. What I don't know is whether the unaffected portion contains highs when you engage high pass on the send.

Afaik the split is done for the dual compressors so it's my guess the lows are just lows when fx level is blended back in from the front level control. That one wouldn't be doing anything in this setup.

What I am hoping for you is a flukey good enough result. The Trace would be amping the lows. The fx send level is on the back with the switch. It can do instrument level up to line level so won't be any problem driving a power amp.
 
#58
Downunderwonder said:
I think not. Maybe yours is different but not likely.

I am pretty sure the loop is a parallel blend. Front fx knob controls fx return blend level. What I don't know is whether the unaffected portion contains highs when you engage high pass on the send.

Afaik the split is done for the dual compressors so it's my guess the lows are just lows when fx level is blended back in from the front level control. That one wouldn't be doing anything in this setup.

What I am hoping for you is a flukey good enough result. The Trace would be amping the lows. The fx send level is on the back with the switch. It can do instrument level up to line level so won't be any problem driving a power amp.
Click to expand...
Interesting- any idea what that crossover point is? Might it be defined by the graphic eq's "Sweep" knob? Now that would be cool...
And so the hi-pass toggle sends highs to an external FX thingy, and keeps lows out so as to avoid a muddy end result... Your thought being to use that Send to send the signal instead to the power amp. Diggy!
I'm in the middle of a house rehab thing, but soon as I can I'll try it. Many thanks, Wonder-dude!
 
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#60
Downunderwonder said:
I think the EQ balance controls relative levels of the highs and lows after the compressors. So you could prove or disprove my guesswork by cranking left and right.
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That 250 SMX just needed an adjustable crossover and a lo or hi send to have brought it into the realm of "ultimate"! Just my humble opinion...
(I wonder if one could be modded in?)
 

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