Couple plate and front firing

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Bill Fitzmaurice
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Re: Couple plate and front firing

#16 Post by Bill Fitzmaurice » Thu Oct 03, 2019 9:31 pm

They have an effect down to the frequency where the total length of the horn plus the plate equals 1/4 wavelength. Horn length determines how low the horn loading extends, mouth area determines how low flat response extends.

Droogne
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Re: Couple plate and front firing

#17 Post by Droogne » Mon Oct 07, 2019 5:10 pm

    Bill Fitzmaurice wrote:
    Thu Oct 03, 2019 9:31 pm
    They have an effect down to the frequency where the total length of the horn plus the plate equals 1/4 wavelength. Horn length determines how low the horn loading extends, mouth area determines how low flat response extends.
    I guess cornerloading in room theoreticaly needs the same 1/4th wavelength requirements?

    what about the mouth area? Cant find the formula.. Is there a simple rule of thub to estimate how big the horn needs to be to support a flat response down to a certain frequency?

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    Bill Fitzmaurice
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    Re: Couple plate and front firing

    #18 Post by Bill Fitzmaurice » Mon Oct 07, 2019 5:32 pm

    Corner loading is totally different. Google 'loudspeaker spatial loading'. A perfect horn would have a mouth perimeter of one wavelength.

    AcousticScience
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    Re: Couple plate and front firing

    #19 Post by AcousticScience » Fri Nov 15, 2019 9:42 am

    A V-coupler on direct radiator subs might amplify the harmonic distortion. It would sound "louder" if you're doing metal with muddy bass lines but not cleaner.
    Fake corners would need to be rigid, otherwise they'd just vibrate instead of reflecting back the bass in phase. Corners with walls too short would amplify the upper bass more than the lower bass. I've tested this. I'm not sure if it takes a whole wavelength as I haven't been in any room big enough to test this.

    As for commercial subwoofer SPL ratings:
    Using Xmax figures and two B&C 18SW115 drivers, the displacement SPL at Xmax in a 40Hz tuned even frequency response double eighteen worked out at about 136dB continuous (Calculated on hornresp by me). Allowing to push above Xmax but below Xlim might yield a decibel or two.

    The maximum sensitivity of a double 18 with lighter weight drivers with a 40Hz tune I have computer run is about 105dB 1m with 2 watts (2.83v 4 ohm). I suppose if I made the box huge so that 40Hz played much louder, or perhaps the midbass is louder, or horn loading the harmonic distortion, I could possibly get 107dB with 2 watts, but a max SPL of only 132-3dB continuous with B&C 18TBX100 drivers in around 380 litres. The 141 dB figure - well two Danley Sound Labs TH118 might do it....

    As for power compression, a higher power handling driver will run cooler at the same power as a lower handling one so saying "power compression above 500 watts" is meaningless as it depends on the driver. I'd expect a Kappalite 15 to compress a lot more than the B&C 18 with 500 watts, and a Skytec driver to compress even more assuming it could take 500 watts.

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