General sub question

[basicsystem]

Although I have read through several threads and articles linked from those threads (such as Bass Mgmt 101), I am still not sure if I will benefit from a sub.

Here's my situation:
I have Polk SDA 1.2 reference towers as my main speakers (you will have to be a little older to remember those). Those speakers (supposedly) have very good base (15 in. woofers). However, in my room (about 20 by 25 with 20 ft. ceiling) I really don't feel much impact at the low end.

The Ultra 12 has a 12 inch woofer and is not rated as low as the Polks (for what that is worth). Will an Ultra 12 benefit me?

More relevant info: right now my Polks are driven by a NAD 7600 receiver (again you have to be older ...). The Polks and the NAD are in pristine condition.

I am going to upgrade to either the Emo XPA-2 or 2 UPA-1s to drive the Polks (and that may solve the problem). Like many people on these boards, I'm getting a headache trying to make that decision ...

My (wild) guess is that the Ultra will improve my bass because it has more displacement (and a different design) than the Polks. Is that logical?

The reason I am asking this question is because the Ultra 12 is on sale. If I am eventually going to get it, I might as well get it now ...

<I>ps - While writing this message my ERC-1 arrived (good timing).</I>

[jackfish]

The SDA 1.2 does not have a 15 inch woofer. The low frequency drivers are eight 6.5" midbass which couple a 15" passive radiator. I would think a subwoofer or two would help those Polks nail down the low end. The Polk SDA 1.2 has been measured to produce output of 25 Hz exceeding 100 dB. The Emotiva Ultra 12 will do much better than that.

[basicsystem]

Yes, jackfish you are right about the Polk drivers (duh). I'm beginning to lean heavily to the Ultra ...

fyi - The ERC-1 is very nice. The only thing I'm going to have to change is the silver trim pieces. With the silver and the blue ... there's alot going on there ...

[jackfish]

For those Polk SDA 1.2s I'd seriously consider a pair of XPA-1s if you can swing it. Those with an Ultra 12 or two in your relatively spacious listening area would kick some major ass.

[Animo]

My home made speakers have two 10 inch woofers in each cabinet.
They were designed to go down to 20Hz flat in room response. However, because of their design, they do not have the impact that one would get from a dedicated subwoofer (or 2). Personally, I feel that any full range speaker or monitor, will benefit from a dedicated sub. I then built a dual 13 inch driver subwoofer, and cannot believe the information, and impact that I was missing.

[basicsystem]

I ordered the XPA-2 amp today. I actually thought about two XPA-1 amps, but decided that was little bit too excessive (in this day and age). And if the XPA-2 doesn't seem sufficient (doubt it), I can always bridge it, right?

A question I never thought I would have to ask:
Should power calcs be based on max RMS? My stereo system has a single dedicated breaker. So I guess I should keep things under 1400 watts total?

My current plan is to get the XPA-2, a UPA-1 (center channel), a UPA-2 (surrounds), and an Ultra 12. That will put me over the 1400 limit (based on max RMS). Maybe max RMS is an unreasonably high limit?

[basicsystem]

I found a message buried in a thread about the XPA-7. Lonnie ran the XPA-7 full out and it only drew 2 amps. Power draw should be no problem. I got myself a little bit worried for awhile (especially since the back of the XPA-2 amp says 1500w max and the manual includes a warning about combined power usage).