OK, we know that simple on axis, straight into the speaker frequency measurements aren’t the whole story – getting a range of measurements at different angles gives a better idea for speakers getting general use, not the whole glued to the magic sweetspot that a lot of hifi has.
So it was time to do some directivity measurements. I don’t have the a licensed copy of ARTA so I can’t do the heatmaps ala Gainphile’s site – but at least Room EQ Wizard is a nice free package that makes it fairly easy to overlay lots of frequency response graphs in different colours.
To do the directivity plots, I took the entire speaker (box + waveguide) outside and sat them on a turntable made (with help from Col) from 2 bits of marine ply attached together by a lazy susan bearing purchased from Ebay. My backyard isnt huge so I could still have some environmental effects – but there is no ceiling and it should be bigger and less obstructed than the loungeroom.
The below measurements were done with the mic @ 2 metres distance, pointing direct into the compression driver. Then the turntable was rotated 7.5 degrees and another measurement taken, up until 60 degrees off axis. I then smoothed the response graphs to 12/octave to make them more readable.
I turned off the crossover, so lower frequency was only being attenuated by the 66uF protection capacitor – which gives a single order high pass filter @ about 400hz
I did leave in the miniDSP correction I was using for the PH916.. this was set up to give as flat as possible on axis response:
First I measured the PH916, with the following response:
Then I measured the LTH142, with the following response:
Now one gotcha here is I used the same EQ settings, and the LTH142 measures a bit brighter above 7khz than the PH916, so its a bit harder to eyeball and compare directly.
But the results are interesting, the PH916 has a closer spread below 10khz, so better directivity. But more chaotic dips above 10Khz. The EQ I am using has a big notch at 11.5khz – looking at the graphs this only helps on axis, and maybe makes things worse with the PH916 off axis.
For starters I’m now crossing over at 700hz to avoid the first dip at 600hz.
Also as a comparison I took a measurement of the Lorantz woofer the same way:
though this is using a 2khz LR24 cutoff. as expected, no directivity issues. Not sure what the huge dip at 280hz is??
Also to measure the angles properly I purchased a CRAFTRIGHT 300MM DIGITAL ANGLE FINDER (i.e. protractor) from Bunnings – this is a handy but of gear, I’ve used it to toe in the speakers in the loungeroom so they are 22.5 degrees off axis pointed at the couch (about 3M away) – this translates to a very slight toe in. For now I’ll use the 22.5 degree toe in as the basis for measurements.
Dip at 280hz may be baffle step?
YEs, very possibly! I’m currently running with a MiniDSP curve made fairly flat at listening position (22.5 degrees off axis) across the board so hopefully that has taken that all into account.
Of the Faital, Pyle, and Eighteen Sound (plus any other waveguide/horns you’ve tried), which do you prefer? I was very interested in the XT1464, until I saw measurements showing that it probably beamed worse than an Eminence HE2A (exponential flare, 2″ exit). And now, this PH916 has caught my eye. You’re the only person I’ve found who has posted any info on it. I’m looking for the smoothest constant directivity horn I can get in a 2″ or preferrably 1.4″. Thanks for the info you’ve posted.
I’m limited to 1.4″ waveguides if I stay with my chosen HF144 compression driver for these speakers, and I don’t want additional variables in the mix from throat adapters etc.
But the XT1464 is audibly a definite step up from the PH916 for my usage of it. The PH916 was OK though. But my waveguide search has stopped now I have the 18sounds, for my situation (medium size loungeroom, listening position about 3M from speakers) they are great.
I havent got around to hauling all the gear outside to repeat the measurements with the 18sound however, I will do so when I get around to making the enclosures, as I need to redo the crossover config in the MiniDSP really rigorously. But even with my current “she’ll be right mate” quick setup they are sounding very good to me.
Got it. The XT1464 is currently at the top of my list then. I appreciate the info! Thanks from Texas.