Been a while since I've posted here, but this forum was always a source of inspiration and I thought I'd post my latest loudspeaker development here.
I'm listening to 3-way dipoles, bass is handled by Eminence Beta 15A in a (shallow) Y-Frame + T-Bass circuit (as developed by the late Graham Maynard here on diyaudio). An Y-Frame, like a U-Frame exhibit a quarter-wave resonance at tha back which needs to be dealt with, options are:
- damp it (as in NaO speakers)
- EQ
I've experimented with a third: placing a monopole (mid) woofer in the Y-Frame cavity that radiates in anti-phase. In my case, an 8" Monacor SPA-8PA in ~6L, which has the required sensitivity. Turned out it works rather well and you get some extra things for free:
- reduced back radiation at the respective resonance frequency, in my case ~250Hz. This happens to be a wavelength very close to the first reflection dip off the front wall, so it's very beneficial if you - like me - are forced to place dipoles relatively close to the wall
- no need for an extra amp channel (with a sensitive enough monopole driver). In order for it to work, the monopole should be subject to the same quarter-wave peak as the bass driver, that is, radiate into the cavity.
- subjectively, the midbass is punchier - in spite of the rather subtle effect at the front - compared to the plain dipole (both equalized flat)
Attached a measurement at the back. One can see the original response with the resonance, the bandpass output of the monopole "filler" and the end result. Surely can be done better, especially with an extra channel of DSP nd amp.
I'm listening to 3-way dipoles, bass is handled by Eminence Beta 15A in a (shallow) Y-Frame + T-Bass circuit (as developed by the late Graham Maynard here on diyaudio). An Y-Frame, like a U-Frame exhibit a quarter-wave resonance at tha back which needs to be dealt with, options are:
- damp it (as in NaO speakers)
- EQ
I've experimented with a third: placing a monopole (mid) woofer in the Y-Frame cavity that radiates in anti-phase. In my case, an 8" Monacor SPA-8PA in ~6L, which has the required sensitivity. Turned out it works rather well and you get some extra things for free:
- reduced back radiation at the respective resonance frequency, in my case ~250Hz. This happens to be a wavelength very close to the first reflection dip off the front wall, so it's very beneficial if you - like me - are forced to place dipoles relatively close to the wall
- no need for an extra amp channel (with a sensitive enough monopole driver). In order for it to work, the monopole should be subject to the same quarter-wave peak as the bass driver, that is, radiate into the cavity.
- subjectively, the midbass is punchier - in spite of the rather subtle effect at the front - compared to the plain dipole (both equalized flat)
Attached a measurement at the back. One can see the original response with the resonance, the bandpass output of the monopole "filler" and the end result. Surely can be done better, especially with an extra channel of DSP nd amp.
Attachments
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