Unfortunately my engineering degree is in mechanical so my electronic skills are not up to par with the experts in this forum. I need help trying to take the known paramters from all of my equiment and settings and trying to determine the power output (watts) that my surround back speakers are receiving at a given db level on the Model 950 without any measurements....pure theory.
Parameters:
Acurus A200 - 200 watts output at 1.1 V for full output
Klipsch KSB1.1 - 92 db sensitivity. 75 watt max.

I want to compare the output voltage at say, -10db on the Model 950 to the input voltage on the Acurus A200 to find the wattage that the speakers would be seeing.

Does this make sense, is it possible, what other suggestions would anyone have. I am trying to determine at what level on the Model 950 I might blow the KSB1.1 off the wall!

Well, amplifiers for home audio are voltage devices in that they regulate (or try to) their output voltage based on their input voltage. So the first step is to convert to volts. Assuming a reasonable load this simplifies things a lot.

Once everything is in volts all you need is to convert a linear scale to or from db, depending on what exactly you want out. The db scale is set up such that each 'bel' (Alex ? ) is ten times as large as the preceeding 'bel', with each bel divided into ten 'decibels'.

If all you're worried about is your speakers surviving, I wouldn't. Any reasonable speaker can absorb an amazing amount of clean music signal, as long as the bass information isn't beyond the capabilities of the driver(s) and the spectral and temporal distribution is anything close to typical for music.

Thermal limitations (which is what watts are) seldom are a factor in a HT system. Physical limits can be in the case of too much deep bass into a speaker not able to reproduce it, but this is generally a very audible problem long before anything detonates.

Every speaker I've ever blown was from too little power with only one exception.

Thanks for the feedback. I have my rears crossed over at 80 Hz which is above the minimum db rating on these speakers. I guess my real test would be to only turn on their amp and "crank it up".

"Every speaker I've ever blown was from too little power with only one exception."

So before Scott takes your advice... just how many speakers have you blown up?? hehe just kiddin!

"I have my rears crossed over at 80 Hz which is above the minimum db rating on these speakers."

That should be fine. You'll damage your ears before your speakers. Being surrounds, you'll fine they'll probably never hit their 75W max more than the rare few seconds (and I'm guessing that's the RMS rating).

And 80Hz is perfect for those speakers since it'll only make the woofers sound cleaner and more open by not having to play that deep bass at the same time as higher sounds.

And it's not a good idea to run your speakers to their F3 point anyway. What's that Klipsh ~35Hz or something like that?
1) A company might rate 'low' to look good (or rate 'in room response' without saying it). I mean how many customers test the anechoic response of the F3 point of their speakers right??
2) Typically crossing speakers an octave above is better so you get no dip before you cross into your sub.

The 950's x-over is very steep so no reason to cross your speakers lower when the sub should be non-directional and far better designed (and positioned) to play 80Hz and below.

actually, the ksb 1.1 is rated, 2.5 db down, at 91hz. given that it's a 5.25 bass driver, i think i would try a higher high pass point.

imo, you definitely have enough power to land those 5.25 speaker cones onto the floor at 80hz high pass.

also, if you listen to sacd or dvd-a, no high pass is applied digitally, so definitely switch ON the analog bass management toggle on the back beforehand. also, the 6 channel bypass level is higher at -10db than digital surround formats.

BoB: Just curious, is there any way to judge *roughly* what the -3dB point of a speaker would be, simply considering the size of the midrange/woofer? (I'm thinking 6.5".)

[QUOTE]Originally posted by Kevin C Brown:
[B]BoB: Just curious, is there any way to judge *roughly* what the -3dB point of a speaker would be, simply considering the size of the midrange/woofer? (I'm thinking 6.5".)
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kevin: the only experience i have with 6.5", 2-ways has been studio monitors. companies like tannoy usually publish very real specs for these and the -3db point is mostly around 50hz. lesser quality is around 65hz.

are you buying or building?

Thanks for the comments. One question, I have Klipsh RS-7s (wide dispersion) as my side surrounds. They are capable of a lot lower frequencies(49Hz I believe) and 150 watts max. They too are driven by an Acurus amp. The problem is the crossover control for the back surrounds and side surrounds is the same so would going to 100Hz be too high for the RS-7s. I was trying to stay at 80 Hz to stay close to the octave multiples.

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scott....i'm sorry for the misinformation in that i did not catch that you said your ksb 1.1 speakers were used for surround BACK (one day i'll learn to pay attention when i read). in this case, i'll say you are aok to use 80hz for the hp point.

i should have asked first, but what are you using for FL/FR speakers? (i see now that you use rs-7 for the surrounds).

as you know, the sacd/dvd-a comment i made does not apply to sb, so please ignore. how do you like the klipsch speakers, btw?

Technically it is possible to tune any given driver to almost any range, but in reality most of the really goofy variations come down to being what I call 'engineering stunts'. The reason is simply that although it may produce a clear tne at a low frequency a typical smaller driver cannot generate a useful quantity of output at the low frequency extreme and so the design will be impractical.

So in practice you see low frequency extension typically (roughly) follows the radiating area of the low frequency drivers. Some bass systems DO use multiple smaller drivers to good effect, though.