Need some audio math help

I use my sim racing rig a lot. I've been using headphones while racing to not disrupt the families sleeping habits. Headphones lack bass. After much deliberation I came to the conclusion that I needed a tactile transducer, other wise known as a bass shaker. For those that don't know these mount to a chair or seat and vibrate when the low frequency sounds hit. So you can "feel" the bass while it not being audible.

So being a cheap bastad I just ordered the cheapest crap I could find.

This is the tactile transducer I found for ten bucks. http://www.daytonaudio.com/index.php/tt25-8-puck-tactile-transducer-mini-bass-shaker.html

The specs are;

15 watts RMS

30 watts max

8 ohm

frequency response of 20-80hz

I found this amp to drive it. http://www.amazon.com/Lepai-LP-168HA-40-Watt-Amplifier-Output/dp/B0070Z87YO/ref=sr_1_8?s=electronics&ie=UTF8&qid=1428633091&sr=1-8&keywords=lepai+audio+amplifier

I found an independent test of the amp that gave these specs;

11 watts RMS @ 4ohms

28 watts max @ 4ohms

Those are from the subwoofer circuit. It says the amp will go from 2-8ohms.

Now this is where my lack of math skills come into play, and I complicated the equation by adding a second transducer just before checking out.

So leaving the second one out for a little bit I figured the amp will be putting out 5.5 watts RMS and 14 watts max at the 8 ohms of the transducer. Does that sound right?

Now lets throw the second transducer into the equation.

If I wire the two transducers in parallel, I would get 4 ohms, correct? At 4 ohms I'm back to 11 watts RMS an 28 max, correct? But I've also upped the power handling capacity of the speakers up to 30 watts RMS and 60 max correct?

If I wire them in series I would get 16 ohms, correct? At sixteen ohms the amp is only putting out 2.75 watts RMS and 7 watts max, correct?

If those are correct I think I can safely say the wiring them in series is out. Firstly because the amp doesn't say it can go to 16 ohms and also because the power is so low.

So I guess my main question is would it be better to run one transducer at half the power handling capacity or run two in parallel getting more power but at a little less than half the power handling capacity?

Also, I have seen some problems reported with the crossover not working. One video had the crossover set a 50hz and it was still making noise through the speaker at 1000hz. I'm not sure what it means to a transducer but would adding some low pass filters help? If the transducer only responds from 20-80hz would it even try to reproduce the higher frequencies?

If you wire in parallel, it'll halve the resistance, so it'll go down to 4 ohms. If in series, then it'll go up to 16. If you have 4, you can do a series/parallel to get back to the original 8 ohms.

Crossovers are not hard limits. They start attenuating at the crossover frequency at a slope.

So...my math was correct then?

I'm not sure about the power handling part, but the rest of it sounds right.

But the answer is really to wire them in parallel if the amp can handle a 4 ohm load.

Okay, no that we have the wiring figured out, I have been overthinking the mounting.

I could mount them directly to the chair, and isolate the chair with some rubber at it's mounts to get all the vibration in my body.

Or, I could mount them directly to the frame of the rig, isolate that form the floor, and get vibration through the whole thing.

I'm not sure which would be better.

This is what I'm working on.

You berkeleyers will sit and expound for hours about politics, religion and F7...but no one has any input into the optimal placement for tactile transducers in a gaming rig!? I see how it is!

We had one at work and they had mounted one on the underside of the seat bottom. The other one was on the back of the pedal assy.

In reply to Scott_H:

Did you try it out? If so, how was it?