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REW & Measurment mic, confirmation

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Norseman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Norseman Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2023 at 2:18am
for a four scoop, 4 kick system, is it possible to test only one scoop, one kick, one midtop for time alignment/IR, and apply this to all?

i understand this is not going to be accurate for the EQ etc as the coupling of drivers makes a propagation of waves all summed together at listening position, but would it be reasonable to do for IR timing only?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vertx Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2023 at 2:39am
I've not worked on such a system so I can only speculate.

What your saying I've done successfully for direct radiating ported/vented enclosures - Do an alignment for one half of the left stack, then applied thee settings to the full left stack, then the right stack, and it's been OK (read: better than nothing/gets you in the ballpack)

For horn loaded system, the extension of the horn path and radiating area you will see by adding more enclosures may have an effect on low frequency extension, which may impact your lower crossover point selection, which will impact your alignment settings. How much would depend really but you have nothing to lose by giving it a go and then reviewing before the gig with the full stack. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Norseman Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2023 at 4:08am
Originally posted by vertx vertx wrote:

Originally posted by Norseman Norseman wrote:

[QUOTE=vertx]1. Individually sweep drivers. Flatten response of individual components to taste

this is to be done without crossovers in place?

Both usually, but I like to start without filter in place at low volume, making sure you do not put too much low frequency thru a comp driver, for example.

The idea being the natural response of the driver without crossover filters will sometimes assist in picking a crossover point.

For instance, in a standard 2-way 12" woofer + 1" comp, I'd want to know the natural acoustic rolloff that the woofer has in the top end, and the comp/horn combo has in the low end, prior to adding filters. Picking then, ideally, a point where both have low distortion, equal on/off axis response that would only be improved by electrical crossover filters.

Sometimes seeing the natural driver rolloff of 6db or 10-12db per octave, for example, will determine the electrical filter one could use, i.e to get a 0db sum at crossover, with 24db per octave acoustic slopes, would require only a 12db electrical filter, which might combine with the natural driver rolloff, to form the 24db acoustic crossover slope if that's the intended target.

Intended application may also play into the above, for example using the same pair of 12" + 1" combo for HiFi listening levels vs PA listening levels, one might be able to crossover lower in the HiFi setting with lower levels, thus gaining closer centre to centre spacing between the drive units.





this is a good point.  i know that the 12s in my midtops can comfortably go down to about 80hz if needed, with authority, but i have kicks in between.  i will try and measure the natural roll off of each cab with no filters applied, and use REW frequency range feature with some leway for the sweeps to avoid any damage, and of course, use low volume.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Norseman Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2023 at 8:44am
as i understand it, REW can allow for you to input the sweep range for each sweep, so i imagine setting, say 900hz --> 20,000 hz may be an acceptable range for a comp driver whos spec sheet says 1000hz is the lower limit, without it breaking...

so similarly with woofers, maybe set the range to just outside its passband when running sweeps...?

this fellow in his presentation seems to think doing the timing this way then no longer is affected by choice of filters, and one can then choose the best filter for flat response summation...

i have no idea how phase factors into this however???  since filter choice affects phase would one then choose different filters based on what it does to the phase trace?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2023 at 9:00am
I believe REW starts sweeps at _half_ the specified measurement frequency - that is something to be very wary of
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Norseman Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2023 at 9:28am
meaning 40hz = 20hz?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2023 at 10:54am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 06 February 2023 at 11:44am
Originally posted by Norseman Norseman wrote:



this fellow in his presentation seems to think doing the timing this way then no longer is affected by choice of filters, and one can then choose the best filter for flat response summation...

i have no idea how phase factors into this however???  since filter choice affects phase would one then choose different filters based on what it does to the phase trace?



this is the way that makes sense to me. And it seems to work. But the consensus amongst people more experienced than myself seems to be that alignment should be done after filters have been applied.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Norseman Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2023 at 6:26am
round and round we go. lmao

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