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Old 29th September 2008, 12:09 PM   #21
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Using damping material inside the enclosure isn't neccessary in the frequency range which the cabinet is designed for.

Regards Johan
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Old 29th September 2008, 11:13 PM   #22
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Strictly speaking, that box isn't a tapped horn, since its internal waveguide isn't long enough to set up quarter-wave resonance at the low end of its response. A tapped horn only exhibits tapped behavior above the quarter-wave frequency of the pipe, where it can resonate alternately at quarter, half, three-quarter, and whole-wave frequencies - the secret to its smooth response.

Instead, Rademakers' box is more like ElectroVoice's "SubScoop" T18 and MTL-1X cabinets, which behave like a high-tuned bass reflex cabinet (I believe it's tuned between 45 and 50 Hz) in territory well below the frequency where the waveguide stops acting like a horn. The horn adds punch (and a somewhat rising response) above 80 Hz. I've found that Rademakers' box is a good choice for drivers with weak motors -- I've got a set of EVM-15L drivers that I may stick into cabinets like these. I did a design for a scaled-down version of the ElectroVoice T18 a while back that promised good results from the relatively wimpy drivers.

I wonder about Tom Danley's "invisible bandpass" CS30 subwoofer -- has anyone figured out what's going on inside one of those? Its impedance curve is near-flat, which means that there's no helmholtz resonance going on, and if there's any quarter-wave resonance, it's being cancelled by a complementary curve. My hunch? I think the CS30 may be a TH Mini in reverse -- with the smaller end of the horn being open to the outside, and the larger end being sealed behind the driver. Some hornresp modeling will be needed to confirm this, but that's my suspicion.
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Old 30th September 2008, 03:48 PM   #23
jbell is offline jbell  United States
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quote

Strictly speaking, that box isn't a tapped horn, since its internal waveguide isn't long enough to set up quarter-wave resonance at the low end of its response.

/quote

I've been trying (unsuccessfully, I think) to model rademakers style of cabinet in HornResp as a TH....

While doing so, I did come up with this that was of interest...
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