LX Mini style diffusers for open baffle mid/HF

Is there any consensus about whether Linkwitz LX Mini Style absorber stuffed cylindrical diffusers mounted behind OB midranges do anything beneficial for sound? It seems they are quite well hidden in the "shadow" of the magnet structure, so I can't see much energy making it into the cylinder. I made a crude set and didn't measure much difference to frequency response. Obviously, FR is only part of the story, or maybe I didn't stuff the cylinder tightly enough. However, I haven't noticed any other designs using this configuration, have they been proven to be useless?
 

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I'd be inclined to do some test measurments before coming to a conclusion. My guess is a larger diameter shorter length tube would work better, but not look as good.

Erin's measurements here: https://www.erinsaudiocorner.com/loudspeakers/linkwitz_lx_mini/

The mid/high polars look quite good.
Yeah, pretty good null at 90 degrees. Too bad the tube provides the supporting structure for the driver, otherwise I’d try To persuade Erin to measure them without the diffuser.
 
Actually, since I have the data, I may as well share it. Top level conclusions:
  • Diffuser does not impact on axis performance
  • Diffuser significantly reduces cardioid null bellow 3kHz (but it's still 15 dB down from on axis)
  • Very little change to response at listening position
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That’s an interesting speaker,
An LX 521 with a bass reflex cabinet for the woofer? Are you using dsp or?
Looks like it may be more suitable for smaller rooms. I’m considering an LX mini build. Any suggestions?
Thanks
 
Actually, since I have the data, I may as well share it. Top level conclusions:
  • Diffuser does not impact on axis performance
  • Diffuser significantly reduces cardioid null bellow 3kHz (but it's still 15 dB down from on axis)
  • Very little change to response at listening position
View attachment 1083624
Interesting measurements. Thinking how such big diference is at 1khz with and without diffuser at 90deg. Looks like dipole moves to cardioid side at these frequencies. Shape of polar response changes but on axis should change a little in such case…little strange IMHO
 
That’s an interesting speaker,
An LX 521 with a bass reflex cabinet for the woofer? Are you using dsp or?
Looks like it may be more suitable for smaller rooms. I’m considering an LX mini build. Any suggestions?
Thanks
Yeah, dsp. Two of these For 8 channels of fun:
https://www.parts-express.com/Dayton-Audio-KABD-4100-4-x-100W-Bluetooth-Amp-Board-with-DSP-325-434

With a sub woofer as well.
If you’re prepared to buy a calibrated mic and enjoy playing about, I’d suggest rolling your own vs building a straight LX mini, much more fun. 😄
 
Interesting measurements. Thinking how such big diference is at 1khz with and without diffuser at 90deg. Looks like dipole moves to cardioid side at these frequencies. Shape of polar response changes but on axis should change a little in such case…little strange IMHO
I would expect the fact the side null effect is confined to low kHz range is related to wavelength and the distance between the diffuser and the cone, which is approx 10cm. I don’t think the loss of the 90 degree null is desirable. I expect the benefit, such as it is, is the minor reduction in rear energy. I measured less than 2 dB, but a different magnet structure, and a wider or more heavily stuffed pipe could increase that significantly. I don’t have the Linkwitz plans, so I don’t know how much stuffing he recommended. Mine was quite loosely filled.
 
That’s an interesting speaker,
An LX 521 with a bass reflex cabinet for the woofer? Are you using dsp or?
Looks like it may be more suitable for smaller rooms. I’m considering an LX mini build. Any suggestions?
Thanks
i have a pair of lxmini. happy with them overall, can be a little bit shouty on some recordings, maybe you can try Erin`s dsp corrections if you can get a hold of him. the L16 woofer is quite capable for its size.
 
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