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Where will I get the most out of my 2 channel amp ??

post #1 of 22
2/19/13 at 4:36pm
Thread Starter 
Hi everybody!

Newbie to AVS forums here, but not necessarily new to A/V though. I may know just enough to confuse myself so I come to AVS to share my thoughts and hear yours.

So here it goes...

I recently upgraded my front stage of my 5.15 system along with adding a parasound 800II amplifier. My room now consists of 2 kef q900 mains, kef q600 center, kef iq5 rears and 2 kef kube 2 subs ran off Y-adapter from my marantz sr7002. I currently have the mains bi-wired using the front L/R and speaker C L/R channels. I purchased the parasound 2 channel with the intention of powering the lows on my q900's, however, after further thought my hunch is that there should be sufficient power to my mains with the bi-wire configuration. Perhaps I will get more from my amp by using it to power my q600 center...

..Or do you think my original plan is the route to take?

What are your thoughts on the matter? I know I could test it both ways, but I'm hoping do avoid the headache and time.

Any thoughts and input is accepted and appreciated!!

Thanks,

Ryan

Also, what are your thoughts on stereo subs??
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post #2 of 22
2/19/13 at 5:46pm
biwiring adds no power to anything. you could have a problem achieving an appropriate balance if you biamp with the receiver's amps taking the highs and the parasound taking the lows. For the Parasound to happen to have an input sensitivity that meshes precisely with the receiver's output levels to keep the tweeter in predcise line with the woofer(s) would actually be surprising.

"stereo" subs make no difference because our heads are too narrow to let us identify the direction from which low frequencies come. multiple subs, however, appropriately placed, can go a long way toward eliminating the big peaks and dips in bass response that occur in home sized rooms because they have dimensions well below the length of the bass sound waves.
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post #3 of 22
2/19/13 at 8:32pm
Thread Starter 
HHHmmm, Interesting.

Perhaps I have it all wrong...but..

If my receiver has a power rating of lets say 100wpc and I connect 1 channel to a 3 way speaker...is the signal not being split 3 ways?..in other words, 100 watts being shared by the bass, mid and tweeter. Now if I hook the speaker up to 2 channels,ch1 powers the bass and ch6 powers the mid/tweet , shouldn't the bass have 100w all to itself and 100w split between mid/hi for a total of 200w?

Please correct me if im wrong!
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post #4 of 22
2/19/13 at 8:42pm
Thread Starter 
My bad!

Thanks for the replay and sorry for the confusion, I got my terminology mixed up. I meant to say biamp all along, not biwire.

So being that I can biamp the mains with my marantz and not the center, leads me to think the parasound would be most beneficial with the center.
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post #5 of 22
2/20/13 at 11:31am
Quote:
Originally Posted by rchiggins420 View Post

HHHmmm, Interesting.

Perhaps I have it all wrong...but..

If my receiver has a power rating of lets say 100wpc and I connect 1 channel to a 3 way speaker...is the signal not being split 3 ways?..in other words, 100 watts being shared by the bass, mid and tweeter. Now if I hook the speaker up to 2 channels,ch1 powers the bass and ch6 powers the mid/tweet , shouldn't the bass have 100w all to itself and 100w split between mid/hi for a total of 200w?

Please correct me if im wrong!

If you actually double the power, the resulting loudness gain is 3 dB. One notch louder to most folks.

BUT, you are playing back real content, not white noise. And real content has at most 25% of total power going to the tweeter. Assuming (as is usually the case) the split is from tweeter to mid/woofer, the most additional output you could possibly gain with real world material is 25% more power. About one dB. Barely noticeable under most conditions.

More importantly, if you are not achieveing audible distortion without biamping, then biamping cannot do anything to improve the sound (although it might change it if the amps used have different input sensitivities). Clean power is clean power. A 100 watt amp doesn't always put out 100 watts. If additional power means you can get louder, that HAS TO MEAN that quieter uses less power. With reasonably normal speakers in a typical room, listening pretty loud (say 85 dB average) uses a whopping 2 watts or so. Your speakers' drivers just cannot feel, see, taste or smell the unused power that may or may not be present in the connected amps.

Nick from Anthem proposed the only potentially reasonable basis for biamping to make a significant difference that I've seen. Assume that without biamping you have audible distortion. Harmonic distortion is, by definition and in reality, creation by the amplifier (or speaker) of additional harmonic content above the frequency of a given fundamental. If you biamp, the amp driving the tweeter won't be distorting, because it's running at a quarter or less of the power being delivered to the woofers. While the amp on the lows almost certainly continues to distort, the highest frequency distortion products, which would go go the tweeter, don't make iit there, and you may have a less unpleasant distortion profile. That's as good as it gets, AFAIK.
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post #6 of 22
2/21/13 at 10:08am
Thread Starter 
Quote:
Originally Posted by JHAz View Post

If you actually double the power, the resulting loudness gain is 3 dB. One notch louder to most folks.

BUT, you are playing back real content, not white noise. And real content has at most 25% of total power going to the tweeter. Assuming (as is usually the case) the split is from tweeter to mid/woofer, the most additional output you could possibly gain with real world material is 25% more power. About one dB. Barely noticeable under most conditions.

More importantly, if you are not achieveing audible distortion without biamping, then biamping cannot do anything to improve the sound (although it might change it if the amps used have different input sensitivities). Clean power is clean power. A 100 watt amp doesn't always put out 100 watts. If additional power means you can get louder, that HAS TO MEAN that quieter uses less power. With reasonably normal speakers in a typical room, listening pretty loud (say 85 dB average) uses a whopping 2 watts or so. Your speakers' drivers just cannot feel, see, taste or smell the unused power that may or may not be present in the connected amps.

Nick from Anthem proposed the only potentially reasonable basis for biamping to make a significant difference that I've seen. Assume that without biamping you have audible distortion. Harmonic distortion is, by definition and in reality, creation by the amplifier (or speaker) of additional harmonic content above the frequency of a given fundamental. If you biamp, the amp driving the tweeter won't be distorting, because it's running at a quarter or less of the power being delivered to the woofers. While the amp on the lows almost certainly continues to distort, the highest frequency distortion products, which would go go the tweeter, don't make iit there, and you may have a less unpleasant distortion profile. That's as good as it gets, AFAIK.

Well when you put it that way, perhaps my parasound amp will be sufficent for powering the hi/mid and lows on my q900's. Would I not be getting the most out of my amp powering the mains?

Thanks for the info, it's been very helpful and somewhat humbling.
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post #7 of 22
2/22/13 at 9:08am
I really don't know what you mean by "get the most" out of your amp.

If it were me, I'd forego biwiring and run front left and front right of the Parasound, if I just had to get it into the system. (I actually never inserted my Bryston into my system iwwith either my Arcam or my Denon receiver(s).

Then I'd recalibrate the whole system. It's highly likely that the SPL from the parasound will be different from what it was using the receiver's internal amps, throwing things out of whack.

Which, again, is a significant reason not to biamp using the parasound. Unless you have accurate testing equipment and skills, how are you going to determine what trim levels are needed to put the Parasound into the right level to coordinate properly with the tweeters being driven by the receiver's amps?

And if you happen to believe that different amps sound different, why would you put what you must think is the inferior receiver amp in the critical band covered by the low end of typical tweeter crossovers? . . . . Better to run the speakers with one amp each, IMO.
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post #8 of 22
2/22/13 at 9:17am
Quote:
Originally Posted by rchiggins420 View Post

Hi everybody!

Newbie to AVS forums here, but not necessarily new to A/V though. I may know just enough to confuse myself so I come to AVS to share my thoughts and hear yours.

So here it goes...

I recently upgraded my front stage of my 5.15 system along with adding a parasound 800II amplifier. My room now consists of 2 kef q900 mains, kef q600 center, kef iq5 rears and 2 kef kube 2 subs ran off Y-adapter from my marantz sr7002. I currently have the mains bi-wired using the front L/R and speaker C L/R channels. I purchased the parasound 2 channel with the intention of powering the lows on my q900's, however, after further thought my hunch is that there should be sufficient power to my mains with the bi-wire configuration. Perhaps I will get more from my amp by using it to power my q600 center...

..Or do you think my original plan is the route to take?

What are your thoughts on the matter? I know I could test it both ways, but I'm hoping do avoid the headache and time.

Any thoughts and input is accepted and appreciated!!

What is the problem that you are trying to address? What reliable evidence do you have that your AVR was not capable all by itself?
Quote:
Also, what are your thoughts on stereo subs??

They can provide two advantages:

(1) Greater uniformity of the sound field. IOW, widen the sweet spot.

(2) 3 dB more bass.
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post #9 of 22
2/22/13 at 10:13am
Thread Starter 
Quote:
Originally Posted by arnyk View Post

What is the problem that you are trying to address? What reliable evidence do you have that your AVR was not capable all by itself?


No evidence, just going by ear. But it sounds as though my AVR's amp's are "hitting the ceiling" if you will. Having all channels driven, I have noticed when a soundtrack demands bass that it takes away from the highs. I can hear the tweeters sort of "fade" during an explosion. My thought, and maybe i have it all wrong, is by inserting an amp somewhere will free up some overhead on the AVR.


jHAZ you mentioned:

"Then I'd recalibrate the whole system. It's highly likely that the SPL from the parasound will be different from what it was using the receiver's internal amps, throwing things out of whack."

What if I hold out and buy another parasound, only a 6 channel with the same power rating as the 2, use it to power the rest of the speakers? Will that better balance SPL from speaker to speaker?
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post #10 of 22
2/22/13 at 10:40am
Thread Starter 
As for stereo subs...

I absolutely loved them for stereo "pure direct" music!

However, being that I'm gearing towards cinema now... I recently switched back to using the single sub pre-out with y adapter, opposed to L/R pre-out stereo subs . My ear could distinguish that the center and rears lacked any lows that should of been there had I been using sub out. I have both subs stacked on one another just to the left of my front left speaker, before they were directly behind the L/R speakers. The bass does not fill the room like it used to, I need to mess around with placement. Is there a general rule of thumb as where to place 2 subs in a room?... for a starting point, then I can the make minor adjustments from there.
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post #11 of 22
2/22/13 at 11:40am
Quote:
Originally Posted by rchiggins420 View Post

No evidence, just going by ear. But it sounds as though my AVR's amp's are "hitting the ceiling" if you will. Having all channels driven, I have noticed when a soundtrack demands bass that it takes away from the highs. I can hear the tweeters sort of "fade" during an explosion. My thought, and maybe i have it all wrong, is by inserting an amp somewhere will free up some overhead on the AVR.


jHAZ you mentioned:

"Then I'd recalibrate the whole system. It's highly likely that the SPL from the parasound will be different from what it was using the receiver's internal amps, throwing things out of whack."

What if I hold out and buy another parasound, only a 6 channel with the same power rating as the 2, use it to power the rest of the speakers? Will that better balance SPL from speaker to speaker?

re separate 6 channel amp, if you still use the stereo parasound, IDK. You'd have to look at the parasounds' specs. Arcam at least used to make a big point of gain mateching their amps so that no matter what the amp's ultimate power, 1 volt in gave the exact same output from amp to amp. Not necessarily true of other brands (or ARcam wouldn't have made a big deal of it).

If everything runs off one amp, of course all the individual amps in the multichannel amplifier casing are going to be the same (or close enoubgh). And two of the same model stereo amps should have the same gain structure. but you can't count on the same gain between two different models of amps even if they are from the same manufacturer.

re less highs on loud passages, actually, if you were running out of power with your existing amps, you'd get distortion. And added THD actually adds higher harmonics, so it might actually make the highs sound louder (and harsher). Maybe you're just reacting to a change in balance in the program material to have a more bass-heavy profile . . .
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post #12 of 22
2/22/13 at 11:42am
Quote:
Originally Posted by rchiggins420 View Post

As for stereo subs...

I absolutely loved them for stereo "pure direct" music!

However, being that I'm gearing towards cinema now... I recently switched back to using the single sub pre-out with y adapter, opposed to L/R pre-out stereo subs . My ear could distinguish that the center and rears lacked any lows that should of been there had I been using sub out. I have both subs stacked on one another just to the left of my front left speaker, before they were directly behind the L/R speakers. The bass does not fill the room like it used to, I need to mess around with placement. Is there a general rule of thumb as where to place 2 subs in a room?... for a starting point, then I can the make minor adjustments from there.

almost certainly differences in the sound in room are due to different placement of the subs not different electrical connection. Although you now fill in if your center and surrounds have limited bass extension . . . you need a head several feet wide to get your ears far enough apart to be able to distinguish direction from which sounds below, say, 80 Hz come . . .
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post #13 of 22
2/22/13 at 2:46pm
Quote:
Originally Posted by rchiggins420 View Post

As for stereo subs...

I absolutely loved them for stereo "pure direct" music!

However, being that I'm gearing towards cinema now... I recently switched back to using the single sub pre-out with y adapter, opposed to L/R pre-out stereo subs . My ear could distinguish that the center and rears lacked any lows that should of been there had I been using sub out. I have both subs stacked on one another just to the left of my front left speaker, before they were directly behind the L/R speakers. The bass does not fill the room like it used to, I need to mess around with placement. Is there a general rule of thumb as where to place 2 subs in a room?... for a starting point, then I can the make minor adjustments from there.

Generally, the further apart you can get them, the better - but this is not a hard and fast rule by any stretch. Setting up multiple subs is very much trial-and-error - I'm personally in the middle of triple-sub-set-up-hell. eek.gifsmile.gif
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post #14 of 22
2/22/13 at 4:59pm
there's a Harman white paper on the subject of placement of 2 subs, but while it's instructive, for most of us who don't have rectangular rooms with no openings, There have been several interesting threads over in the subs forum on placement of multiple subs, and you likely could turn up the link pretty quickly over there.
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post #15 of 22
2/25/13 at 10:14am
Thread Starter 
Thanks for all the advice!

After taking in to consideration some of the valid points made here,

I have decided to sell the 2 channel parasound and my 2 subs.

I will likely stick with the amp in my marantz,however...

I can get a 3 channel acurus a100 for $300 to power my front stage. L/R/C will all be getting the same output from the Acurus, but then I am back to trying to match the rears, they would still be running off the marantz. So I am not sure what to do there yet. I don't know if it will make a significant difference over the marantz, not enough to justify the $300. What do you think?

As for the subs...

I have come to the conclusion that my room is to large for the kef kube 2's. Even with 2 subs, I have tried placing them in different areas and they just don't shake the room like i want. So I am looking into getting a sunfire TS-EQ12 2700 watt sub. The way I figure, it should be about 15db louder then both of my kubes combined.

Thanks again!

Ryan
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post #16 of 22
2/25/13 at 2:36pm
Quote:
Originally Posted by JHAz View Post

you need a head several feet wide to get your ears far enough apart to be able to distinguish direction from which sounds below, say, 80 Hz come . . .

Huh??? How come?
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post #17 of 22
2/25/13 at 3:13pm
^^^

Because of the length of the sound waves at those lower frequencies.
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post #18 of 22
2/25/13 at 3:41pm
Quote:
Originally Posted by Alan P View Post

Because of the length of the sound waves at those lower frequencies.


What's the formula for calculating this?
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post #19 of 22
2/25/13 at 3:43pm
http://www.sengpielaudio.com/calculator-wavelength.htm
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post #20 of 22
2/25/13 at 3:48pm
And what, our ears need to be 1/2 the wavelength apart... 1/4 wavelength apart?
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post #21 of 22
2/25/13 at 4:04pm
http://en.wikipedia.org/wiki/Sound_localization#Evaluation_for_low_frequencies
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post #22 of 22
2/25/13 at 7:13pm
Quote:
Originally Posted by Alan P View Post

^^^

Because of the length of the sound waves at those lower frequencies.

The wavelength of 80 Hz is about 14 feet. That works out to be a phase shift of about 2 degrees per inch. Thing is that the ear is sensitive to phase shifts at frequencies these low, which is not true above 1 KHz or so.

I don't know what the threshold of hearing phase shift at this frequency is, but the ear might be this sensitive (or not). We're talking detection of something like 12 degrees.
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