# 15 Hz, 102 dB and . . a CRT



## rick57 (Jul 30, 2007)

Hi,

I have a 15 inch driver that in a DIY EBS alignment can produce with 100 watts, 102 dB at 15 Hz, using only 30% of its 14.4 mm Xmax. :bigsmile:

The EBS catch is its big. Ok, I'll put it under the TV. 

Initially I thought of the ease of construction of Sonotube (cardboard constriction cylinder), under a table. Though Id need to also to locate or build table of the right height & length to hide it from wifey and support the 80 cm/ 31 inch CRT TV. 

So maybe just build a 250-300 odd litre/ 10 cubic foot box (maybe sheet flooring) providing both the sub box and support for the TV in one. But . . I suspect that a box producing 102 dB at 15 Hz sitting under a TV is not good for the CRT. 
Though is it no worse than the effect of the soundwaves? :dunno:

Please advise . .

Thank you


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## bobgpsr (Apr 20, 2006)

Careful! The magnet on the sub driver may (likely) will affect the convergence of a CRT TV. Best to keep 4 to 6 ft away.


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## Mike P. (Apr 6, 2007)

I have to agree with Bob. If you already have the driver, see how close you can get to the TV before the magnet starts affecting it. Place a piece of 3/4 MDF betweem the TV and the sub driver to get an accurate representation. If you do build a box for the sub, use 3/4" MDF or 3/4" void free plywood. I'm not sure what "sheet flooring" is or if it comes in 3/4 inch.

_""........102 dB at 15 Hz, using only 30% of its 14.4 mm Xmax.""_

What sub driver are you using?


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## Sonnie (Apr 11, 2006)

Another thing would be the constant vibration sent to the TV. While it might be only a minute amount, over time I could imagine it wiggling things loose and possibly moving the lenses.


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## rick57 (Jul 30, 2007)

The subs are diy . . 

within here: http://repairfaq.ece.drexel.edu/sam/crtfaq.htm#crtemf

I came across this simple suggestion:
A tin can over the magnet will reduce the external field by about 50%.
If more shielding is desired, put additional cans over the first, in
layers, like Russian dolls. (Tin cans are made nearly entirely of
steel).

"sheet flooring" seesm to be an Australian term eg http://buybuildingsupplies.com.au/hmr-tg-particleboard-flooring-19mm-3600x900mm-p-997.html 
What's it called in the States?


The sub driver is (one of the last of) the Adire Shiva 15 inchers.


Issue *probably resolved: Collo's sonotube software here
http://www.subwoofer-builder.com/sonosub.htm
tells me that to tune to a lowly 15 Hz, with the drivers high Xmax,
mounted horizontally, sag will be a problem . .

The drivers could be pulled out & rotated periodically, or the
sonotube itself could be rotated. I think rotating a sonotube would be
easier, and avoids creating a massively heavy box . .

And the direct contact of sub & CRT case is avoided, with a little
space for sheets of extra magnetic insulation if needed.

Make sense?

Cheers


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