another cardioid question

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   hi, i'm just about to have enough subs in my arsenal to give proper cardioid stuff a go.

rear sub located 1/4 wavelength behind the front sub(s) (0.8 m)
rear sub  delayed 1/4 wavelength (2.3 ms)
rear sub polarity reversed

i'm wondering how acoustically similar the cabs have to be to get the desired response, my understanding is to do it "exactly" they have to be identical, but if they are similar enough the effect will still be there, just less pronounced.

the cabs in question are WS218X copies. 4 are identical and loaded identically (b&c), 2 (reversed) are close enough, but loaded with different drivers (RCF).

to add further deviation, i don't have a unified amp set up for my bass section - each pair is run off a different amp.

i'm not after a perfect set up here, just a good enough effect so as to reduce SPL to the rear due to noise concerns. your thoughts and experience appreciated. 

Edited by teeth - 16 February 2023 at 10:19am

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teeth Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 05 July 2021 Status: Offline Points: 565	Post Options Post Reply Quote teeth Report Post Thanks(0) Quote Reply Topic: another cardioid question Posted: 16 February 2023 at 10:14am
	hi, i'm just about to have enough subs in my arsenal to give proper cardioid stuff a go. rear sub located 1/4 wavelength behind the front sub(s) (0.8 m) rear sub delayed 1/4 wavelength (2.3 ms) rear sub polarity reversed i'm wondering how acoustically similar the cabs have to be to get the desired response, my understanding is to do it "exactly" they have to be identical, but if they are similar enough the effect will still be there, just less pronounced. the cabs in question are WS218X copies. 4 are identical and loaded identically (b&c), 2 (reversed) are close enough, but loaded with different drivers (RCF). to add further deviation, i don't have a unified amp set up for my bass section - each pair is run off a different amp. i'm not after a perfect set up here, just a good enough effect so as to reduce SPL to the rear due to noise concerns. your thoughts and experience appreciated. Edited by teeth - 16 February 2023 at 10:19am

csg Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 17 September 2007 Location: bedford Status: Offline Points: 6086	Post Options Post Reply Quote csg Report Post Thanks(0) Quote Reply Posted: 16 February 2023 at 11:10am
	Dissimilar subs does not preclude use in a directional array but it would certainly be worthwhile measuring the two different subs for time/phase so you can correct for any differences. This may result in a change of placement or time correction. In more general terms please remember that directional arrays are at times very useful but at other times they can cause as many problems as they solve, by way of increased overall energy exciting tent or venue surfaces causing greater, still omnidirectional leakage.
	“The fact is this is about identifying what we do best and finding more ways of doing less of it better”

airbell Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 11 June 2009 Location: Berlin, Germany Status: Offline Points: 284	Post Options Post Reply Quote airbell Report Post Thanks(0) Quote Reply Posted: 21 February 2023 at 7:56am
	After testing a lot in my opinion it is in general always better to use the same subs and amps instead of mixing different ones, even if the phase and frequency response look more or less the same! But if you have the same enclosure with the same tuning and only different drivers but with similar thiele small parameters it should work fine together and so cardioid should work too. As csg wrote, is always better to measure than only to calculate the delay, and take care that you have enough distance from the subs to the microphone. Edited by airbell - 21 February 2023 at 7:59am