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[Karl Winkler]

Scott,
I suspect you are probably right about the variant in intermod products across brands causing the problem.  However, I was assuming (perhaps wrongly) that generated harmonics would be the same across brands, determined by the root frequencies, rather than the brand of transmitter.

I used the AT frequency algorithm because the majority of the product being used was from them. I will download WWB but I don't have any shure product. Does it compute for other brand products as well?

I agree with others pointing out that the root cause is improper frequency coordination, and in general too close spacing between carriers. True, different products react differently in terms of IM products, but the fundamental math isn't different, as long as the proper space is given between carriers, based on receiver filtering capability. 250 kHz is definitely too close for almost all analog FM based systems, period. And others have mentioned that 400 kHz is a good standard min. spacing, with 1 MHz between mics and IEMs. If I'm doing a coordination, I try to have 500 kHz min spacing. From there, IAS or WWB or Wireless Designer (Lectrosonics) or Sennheiser's version will all make the appropriate calculations.

In addition, I know you've tried both active and passive paddles on your mic system, but I would stick with passive, especially if the mics work well on their own with a passive antenna system. Try to eliminate any gain stages that are not needed.

[Ike Zimbel]

I agree with others pointing out that the root cause is improper frequency coordination, and in general too close spacing between carriers. True, different products react differently in terms of IM products, but the fundamental math isn't different, as long as the proper space is given between carriers, based on receiver filtering capability. 250 kHz is definitely too close for almost all analog FM based systems, period. And others have mentioned that 400 kHz is a good standard min. spacing, with 1 MHz between mics and IEMs. If I'm doing a coordination, I try to have 500 kHz min spacing. From there, IAS or WWB or Wireless Designer (Lectrosonics) or Sennheiser's version will all make the appropriate calculations.

In addition, I know you've tried both active and passive paddles on your mic system, but I would stick with passive, especially if the mics work well on their own with a passive antenna system. Try to eliminate any gain stages that are not needed.

+100, and further to Karl's point: Frequency coordination programs do not eliminate IM products, they simply predict them so you can avoid putting a working frequency where an IM product could appear. If two mic freqs are only 250 KHz apart, there is simply no space for an IM product to land between them without getting into both mics.

[Andrew Roberts]

+100, and further to Karl's point: Frequency coordination programs do not eliminate IM products, they simply predict them so you can avoid putting a working frequency where an IM product could appear. If two mic freqs are only 250 KHz apart, there is simply no space for an IM product to land between them without getting into both mics.

Thanks everyone for your comments. I have downloaded IAS and will run things through that to coordinate. I will additionally move the IEMs to the top of their range to get them further away from the mics. Further, I will strive to avoid <400kHz between channels but these 500s are a bit more challenging to get quantities from in this area. The 600s were more forgiving but.....Grrrrrr.

I will report back after a couple shows.

[ProSoundWeb Community]