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1,5" wave guide shoot-out
I'm going to do a measuring run on JBL M2, 4367 and VTX waveguides the next few days.
I will try a few different dia's in 2450SL, and 2451 cores. I'don't have an Mg dia and not sure it will take apart my other system to get to the Be's.
I will prost some findings here and if someone want the raw data just give me a shout.
Kind regards
//Rob
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Now, what do we want to know?
I have now completed the measurements and albeit not the same quality as anechoic they do give a reasonable picture of the various JBL 1,5" drivers on the VTX, M2 and 4367 WG's, on and off axis. At least the settings (HW/SW/room/settings/timing/temperature) are identical in all measures, which makes them direct comparable.
The result is about 400 measurement files at 50cm and 100cm distance for 30, 60 and 90 degrees. The files are done without any smoothing and include phase. I did do 3ms, 6ms and 9ms time windows for all combinations to make sure that I got reasonable low end data with a long window but also a short window to see the high frequency with limited room intervention. I used pairs of 2450SL, 2451SL, 2451&475Nd, 2430K and 2451h (Ti, only one). 9 drivers all in all.
I have long argued that the 4" drivers do sound good on these WG's and numbers seem to support that. Please bear in mind that these are raw files and would look significant "nicer" with some smoothing, as most (also JBL) manufacturers show them. It is also clear that 4" goes lower than D2 in these WG's and that 4367 provides horn load to a lower frequency that M2. M2 sure is nice off axis. Horizontal and vertical dispersion is NOT the same in the M2 as could be anticipated from looking at it.
Below are some graphs. You can see measurement data (distance, time window aso) in the graphs. SW is LspCAD 6 PRO with MLS pulses at max resolution. HW computer + Focusrite SOLO V3 soundcard, Earthworks M30 mic, and an Alesis RA300 studio power amp. All walls (and ceiling) had at least 8cm thick sound padding (with egg crate surface absorbers). Measures are 2-channel, meaning that one channel measures the power amp out and second channel the mic and we only project the delta. No capacitor, only a protection resistor in series, so phase is not tuned 90 degrees as in many other measures with protection cap.
Kind regards
//Rob