[samplesj]

I need to add a sub to the bonus room and I was going to "borrow" the sub from the HT.  It makes a good excuse to upgrade.   So I'd like to add a DIY sub(s) based on the 12"

The HT is a closed 15x20 room.  Its got a good amount of treatement but I still have some work to do to find the best spots for the RealTraps.

If I'm calculating the number right it looks like it should be over 100dB at our seating (14') [87dB sens + 200 watts (dropped to 128 for easier calcs) = 108].  Even though that isn't reference I'd be happy with that because we don't listen at reference or even close.  I'm a little worried about pushing it too hard though.   I have room for a second, it fits within the budget for the project, and I have secured WAF, but I don't want to get it if I don't really need it.  Less $ (and time) on subs means more $ (and time) on DVDs.

I only know enough to be dangerous so feel free to let me know if this is a bad idea.

BTW: Does anyone have the specs for the PR-12A.  I tried to use WinISD to figure this out myself, but I can't find the specs for the PR-12A.  I tried using the same specs as the SW-12A but then I couldn't duplicate the 2.6 cu ft box.

[Danny Richie]

All good questions.

For what it is worth I did have a company in the Dallas area hold these to a 106db level (in room) and sent them sine wave signals all the way down to 20Hz at that power level. They didn't drop off the 106db level until 22Hz.

Still I think this was driving them to their limits.

Here is what I would recommend.

Use two woofers and two PR's. Put each in their own air space but in one box.

Use this amp: http://www.apexjr.com/Apexsenior.htm

I had this amp tested and it actually maintained less the .1% THD to a 400 watt level into a 4 ohm load.

Our woofers are 8 ohm loads so you can parallel them on this one amp and it will drive them really well.

Plus, this amp as a boost circuit that can be adjusted to give +2db of boost in the 20-22Hz range. This makes the woofers about 1db down at 20Hz.  

As for modeling it here is what you need:

Use a box volume of 2.4 cubic feet.
Use a Vap of 6 cubic feet.
Use a Fp of 12.2Hz

I have measured the tuning frequency using an impedance sweep and it creates a tuning frequency of 22.3Hz. This is using the PR as is without added or taking away mass.