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Battletroll

In-wall speaker wattage

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I’m finishing up the basement with a 7.1 movie theatre. The room length is 17’ 9” and width is13’ 8”.   It’s time to buy the in-wall speakers, I’m struggling with the wattage on most of them being 75 watts / 300 watts. I’m assuming the rms is 75 then?  My stereo is 150 watts, I’m concerned these speakers won’t work for my left and right:

R-5502

Pro-250-RPW 

 

This works but is an older thx model

kl-6502
 

would love the THX-8000-L but it’s overkill for the room size and too pricey right now. 
 

can someone please provide some input would I be good with the pro-250-rpw or r-5502, or any other input is appreciated. 
 

thanks,

Battletroll

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On 11/1/2019 at 8:47 PM, Battletroll said:

I’m finishing up the basement with a 7.1 movie theatre. The room length is 17’ 9” and width is13’ 8”.   It’s time to buy the in-wall speakers, I’m struggling with the wattage on most of them being 75 watts / 300 watts. I’m assuming the rms is 75 then?  My stereo is 150 watts, I’m concerned these speakers won’t work for my left and right:

R-5502

Pro-250-RPW 

 

This works but is an older thx model

kl-6502
 

would love the THX-8000-L but it’s overkill for the room size and too pricey right now. 
 

can someone please provide some input would I be good with the pro-250-rpw or r-5502, or any other input is appreciated. 
 

thanks,

Battletroll

 

 @Battletroll  I just noticed that no one has answered you in a month and 1/2.  Sorry about that.  Or, did you duplicate your post on some other thread?  I'll take a look.

                                                                                                                                                                                                         Ask Klipsch support, as well as us. 

 

You may want to crossover to your sub at a higher frequency than the typical 80 Hz to keep the high intensity bass out of the in-wall speakers.

 

Things to think about:

  1. What is the volume of your room in cu.ft.?  If you have an 8' ceiling, your room volume would be about 1,941 cu. ft.
  2. Will your room be acoustically live, medium, or dead? 
  3. How far away from the front speakers will you sit?
  4. "         "         "         "    the subwoofer  "         "          " 
  5. Would you say you will play movies Loudly?  Medium level?  Low level?  THX, for a room your size (if you have an 8' ceiling, and medium liveness), modifies its recommended PEAK levels due to the influence of early reflections, which make these lower peak levels SOUND LIKE  THX reference level peaks in a commercial movie theater, even though they are 7 dB lower.  So, instead of 105 dB full scale (loudest peaks) through each regular speaker, they recommend 98 dB peaks at your ears, and instead of 115 dB full scale (loudest peaks) through the subwoofer, they recommend 108 dB peaks at your ears.   Indoors in a room of average liveness, you lose about 3 dB for each doubling of distance (not the 6 dB loss per doubling you would get outside, with no walls).  So, if you have speakers of 92 dB, 2.83v, 1m sensitivity (= 92 db, 1w, 1m into 8 ohms), and you sit 4 m (about 13' 2" ) away from the front speakers, that's 2 doublings, indoors, so your 1 watt needed for 92 dB  transforms into 4 watts needed at 13 feet for the same 92 dB.  But you need 98 dB peaks through each main speaker for something that SOUNDS LIKE reference level in your small room.  So, for just a very brief time, you will need 6 dB more through each main speaker for a maximum instantaneous   peak.   For you, that would be 16 watts, since for each 3 dB increase you need to double the wattage.  So, if your main speakers can really take 75 watts "continuous" power [perhaps what is slightly incorrectly nicknamed "RMS," power, perhaps not], then I would feel confident it would take instantaneous peaks of 16 watts, or even 32 watts, to build in a safety factor. 

 

Subwoofers are a whole different animal, since they have their own built-in amplifier, and the sensitivity of the speakers inside is almost never given.  Look at the "Maximum SPL," and remember that is probably at 1 meter away, so do your calculations.

 

Why then do we heat about blown speakers?

 

  • Film buffs go wild an play louder than reference, or incorrectly predict a peak that is coming, or practice volume riding and blow it.
  • Filmmakers go wild.  They can't change the full scale peak level, fs, on the film or the Blu-ray disk, but they can record most of the film softly, to trick you into turning up the volume, permitting higher (dramatic!) peaks than you are expecting.  Watch out for the bass at the  beginning of Edge of Tommorrow, I think it's called.  Action picture excess can be a problem, especially through the subwoofer, but things like gunfire often have a leading edge of a peak up in the range of the main speakers.
  • People set their main speakers for "Large."  Don't do this, even if you end up getting physically large speakers.  Set all speakers to "Small," sending the deep bass to the sub only, letting it do the heavy lifting.
  • Frequency sweeps or test signals are sent through at too high a volume.  Some tweeters, especially, are very delicate, and will only take a few watts.  In music, these frequencies are as much as 15 to 20 dB below the lower mids and bass, but not in test signals!
  • Most AVReceivvers are power rated quite misleadingly (compared to a separate power amp).   I'm assuming that your AVR (if that's what you have) is rated at 150 watts per channel.  The honest way to rate them is at 20 to 20,000 Hz, all channels operating  (to properly stress the power supply), into 8 ohms, at a low distortion level (usually @ < 0.1%).  Almost no AVR manufacturer does that, unless that spec is buried and in fine print.   The truth can be seen in some bench tests by magazines like Home Theater or, occasionally, Stereophile.  Many of the more acceptable AVRs will fudge the spec to "with 2 channels operating."  Long ago, somebody here suggested that, on the average, a name brand AVR with a 2 channels operating spec would put out about 70 to 80% of the rated power with 5 channels operating.  Who cares?  You don't want the AVR clipping, due to not enough power, because most people here (not all) think that is very hard on tweeters.

Must run ... you might want to check my hurriedly done math.

 

 

 

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