How necessary is it to give extra power to sourround and rear?

Gizmo99

I see 5 and 7 channel amps and I was wondering if they are really necessary ? Does it make that much of a difference for the sourround and rears to get that extra power ? I could understand the left/Right/Center to get as much power needed. However, the sourround and rears are only for ambiance noise.......

treitz3

Extra power always helps. Processing is key.

Willow

I have 3 monoblocks for may mains and let my HK power the rears. In the future I plan on getting an external amp for the rears but not 200wpc like my mains.

janmike

I have a Proceed AMP5 with 250 of true power to each channel. But how much sound is there in the rear channels in HT?

Kex

Multi-channel amplification is probably more helpful for SACD and DVD-A. For HT, it is probably not that important since there is not much sound being sent to the rear channels. Listen up close to the rear speakers during movie playback or during CD playback in Dolby Pro-Logic mode: you will notice that not much sound comes through those channels most of the time.

PolkThug

What matters is if you can hit your listening position with the same sound pressure from any speaker.

Gizmo99

I neither listen or have the capability to do SACD (I have a PS3 but not sure if it does SACD) and DVDA so I think a three channel amp is all I need.

A offtopic question: adcom 5503 good enough to power LSI15/LSIC ?

dorokusai

PolkThug wrote: »

What matters is if you can hit your listening position with the same sound pressure from any speaker.

The efficiency of a loudspeaker is measured with 1 watt.

dbaldus

PolkThug wrote: »

What matters is if you can hit your listening position with the same sound pressure from any speaker.

So imagine this situation:

Someone gets a 3 channel amp to power their fronts and center then uses their receiver (with MUCH less power, say you've giving 200 wpc to the front 3 and 50 wpc to the rears) to power their rears. Then they calibrate their speakers so the pressure level is the same from the listening position in a 5.1 setup.

My question is this: are you wasting the potential of your fronts and center by "dropping them down" to produce the same pressure levels as your rears from the listening position? Or do the rears run much hotter than the fronts and center? Just curious how this works, because I am considering getting a 3 channel amp for my fronts (RTi70s) and center (CSi40) but letting my 247 power my rears since they are just R15s anyway...

dbaldus

Gizmo99 wrote: »

I neither listen or have the capability to do SACD (I have a PS3 but not sure if it does SACD) and DVDA so I think a three channel amp is all I need.

A offtopic question: adcom 5503 good enough to power LSI15/LSIC ?

PS3 does both SACD and DVD-A through the HDMI output - I have one myself and it works fine.

jayman_1975

dbaldus wrote: »

So imagine this situation:

Someone gets a 3 channel amp to power their fronts and center then uses their receiver (with MUCH less power, say you've giving 200 wpc to the front 3 and 50 wpc to the rears) to power their rears. Then they calibrate their speakers so the pressure level is the same from the listening position in a 5.1 setup.

My question is this: are you wasting the potential of your fronts and center by "dropping them down" to produce the same pressure levels as your rears from the listening position? Or do the rears run much hotter than the fronts and center? Just curious how this works, because I am considering getting a 3 channel amp for my fronts (RTi70s) and center (CSi40) but letting my 247 power my rears since they are just R15s anyway...

As a matter of fact...when I added my newly aquired to me 5 channel amp (using only front three channels of it right now) I actually had to raise the trim of the front three to match the rears being driven by my reciever. This was due to the difference in "amp gains". The seperate amp has a 2db gain less then my reciever. But this by no means says it is less powerful. In fact it blows the reciever clear out of the water. I do find however that the dynamics in the surrounds have improved now that my reciever only has to power those two speakers instead of all 5.

dbaldus

jayman_1975 wrote: »

As a matter of fact...when I added my newly aquired to me 5 channel amp (using only front three channels of it right now) I actually had to raise the trim of the front three to match the rears being driven by my reciever. This was due to the difference in "amp gains". The seperate amp has a 2db gain less then my reciever. But this by no means says it is less powerful. In fact it blows the reciever clear out of the water. I do find however that the dynamics in the surrounds have improved now that my reciever only has to power those two speakers instead of all 5.

Interesting. So the amp gain is what makes the difference? I was just imagining hooking it up and having a ridiculous amount of sound coming from the front 3 speakers and then a very small amount of sound coming from the rears. I know that is kind of how the rears typically are anyway (quieter, I mean), but I was just thinking that giving the fronts more power would widen the gap between the fronts and rears, giving an unbalanced sound until I recalibrated my speakers...

Early B.

Give every speaker equal power, and lots of it.

wingnut4772

Not as.. but I think it's important to a degree. I still had Outlaw Monos on my back speakers @200 watts per with an Earthquake Cinenova (300w) running the rest of the show.

venomclan

It also really depends on whether you are using much larger speakers for the front and small ones in the back (as most do), or have 5-7 speakers of equal size and demand. Surround speakers should always be set SPL wise - lower than the front 3 for HT use. Surround sound should be an echo or more distant effect, not a blast you away from behind speaker. Surrounds also tend to be closer to the listeners position than the front 3.

I used to have my surrounds turned up but experimented a bit and now have them set lower then they need to be, with much better performance. As for power, you will have no problem with lower power to the rears. I was using 250 watts up front and 60 to the back with no problem. Put the best amp you can afford on your fronts and do not be afraid to use a receiver or low powered amp for the rears. While extra power usually cannot hurt, I do not see spending the extra $ to run excessive and unused power to the rears for HT use. That is, unless you are using huge speakers for surround. Multichannel audio would be a different story. But wait until Cathy comes with the usual canned response.
Venom

bbeacham

venomclan wrote: »

Surround speakers should always be set SPL wise - lower than the front 3 for HT use. Surround sound should be an echo or more distant effect, not a blast you away from behind speaker. Surrounds also tend to be closer to the listeners position than the front 3.

The front, center, surrounds, and rears should be calibrated with an SPL meter to produce the same sound level at your primary seating area. It is up to the producer of the DVD/SACD to determine if the sound level from the different channels is the same, higher, or lower.

venomclan

bbeacham wrote: »

The front, center, surrounds, and rears should be calibrated with an SPL meter to produce the same sound level at your primary seating area. It is up to the producer of the DVD/SACD to determine if the sound level from the different channels is the same, higher, or lower.

Let me rephrase, I was referring to db not to hz settings. I do advocate the use of an SPL meter.
Venom

PolkThug

I have a dedicated amp for my rear 6/7 channels. If the EX,ES or Discrete 6th channel sound is on the source, I want to hear it at the volume it was intended.

PolkThug

If a baby is burping from the 5th channel at 750Hz, at 20db below reference, then that is how loud I want to hear it from my listening position.

This chart should sum things up.

Meeks32

Gotta remember, when you unload the front 3 speakers from the receiver & only have the rears running, you are going to be putting out more wattage to the rears than the **x7 wattage rating says.

cfrizz

Darla did you always have separate amplification for your speakers or did you have a receiver before it? If so, once you calibrated everything how much of a difference did you notice coming from the amped backs opposed to the receiver running them?

For me again, it was a night & day difference going from having the receiver drive my backs to having the amp do it. Rather than the sounds/music being muffled it is now distinct & clear.

wingnut4772 wrote: »

Not as.. but I think it's important to a degree. I still had Outlaw Monos on my back speakers @200 watts per with an Earthquake Cinenova (300w) running the rest of the show.

dbaldus

Meeks32 wrote: »

Gotta remember, when you unload the front 3 speakers from the receiver & only have the rears running, you are going to be putting out more wattage to the rears than the **x7 wattage rating says.

So how many will I be putting out to the 2 rears with my AVR 247?

http://www.harmankardon.com/product_detail.aspx?cat=REC&prod=AVR%20247

Just from looking at it, I'd say 65 instead of 50, but I wasn't sure? Thanks!

Meeks32

dbaldus wrote: »

So how many will I be putting out to the 2 rears with my AVR 247?

http://www.harmankardon.com/product_detail.aspx?cat=REC&prod=AVR%20247

Just from looking at it, I'd say 65 instead of 50, but I wasn't sure? Thanks!

Dont know, hard to say. The AVR 7300 put out 40 more watts per channel in 2ch mode than 5ch, but thats a much different beast.

dbaldus

Meeks32 wrote: »

Dont know, hard to say. The AVR 7300 put out 40 more watts per channel in 2ch mode than 5ch, but thats a much different beast.

Would there be a spec somewhere that would tell me, or is this a situation where my "mileage may vary"?

bbeacham

dbaldus wrote: »

Would there be a spec somewhere that would tell me, or is this a situation where my "mileage may vary"?

The spec link you provided specifically says 65W/ch in stereo mode. That means 2 channels driven. Generally this implies the 2 fronts, but, unless HK has some really crazy hardware design, the odds are that any 2 channels will give 65W/ch.

jayman_1975

Interesting. So the amp gain is what makes the difference? I was just imagining hooking it up and having a ridiculous amount of sound coming from the front 3 speakers and then a very small amount of sound coming from the rears. I know that is kind of how the rears typically are anyway (quieter, I mean), but I was just thinking that giving the fronts more power would widen the gap between the fronts and rears, giving an unbalanced sound until I recalibrated my speakers...



You are close. The amp gain is how loud it will be relative to volume vs another amp. The gain on my Anthem is 29db vs 31db on my Arcam. Therefore...at any given volume level...the Arcam will always be 2db higher right? That's why i had to adjust the trim to level the two out. At least i think that's how it works.