AVS Forum banner

Status
Not open for further replies.
1 - 20 of 27 Posts

·
Registered
Joined
·
764 Posts
Discussion Starter #1
I am thinking about going with a 5 channel amp and a 2 channel amp for a 7.1 system and to save money, I can go with a lower watt amp for the 2 channel. My question is if i am feeding 180w to two rears and 105w to the other two will that be a problem?
 

·
Registered
Joined
·
804 Posts
Shouldn't be a problem. You may need to increase the channels (in your receiver's menu) output from your receiver to the outboard amp for the channels that are receiving less power.


Basically turn your system on to a level that you normally listen at. Then use an SPL meter (or your ears) and adjust the channel output gain until all of the speakers are outputting the same db level at your listening position. You can use pink noise for this as well or use a soundtrack the you're pretty familar with.


Following this procedure, the gains for all channels will be set properly for your listening level.
 

·
Registered
Joined
·
701 Posts
No, It won't be a problem. From what I have seen/read, most people will put a more powerful 2 channel amp on their main speakers though not their surround channels. Use your SPL meter and calibrate properly and you will be fine. :D
 

·
Registered
Joined
·
545 Posts
"Shouldn't be a problem. You may need to increase the channels (in your receiver's menu) output from your receiver to the outboard amp for the channels that are receiving less power."


Not.


That has nothing to do with an amp's potential output, but rather the sensitivity of the speaker and distance to the listener.


You could probably get away with a few watts and probably never notice, especially when high-passed. 200w vs 100w = 3db difference at full volume, which would have probably deafened you by then anyway.
 

·
Registered
Joined
·
16,827 Posts
Quote:
Originally Posted by Clmrt
Not.


That has nothing to do with an amp's potential output, but rather the sensitivity of the speaker and distance to the listener.
Well, yeah, of course. ...............but that sorta "goes without saying" doesn't it?


What spillz said IS correct regarding the original poster's concern regarding running 2 speakers with a lower output amp than the rest of his speakers; Exeter will simply use his receiver/pre/pro's channel trim levels to adjust for any output difference, if there even is any. Yes, other things besides the rated power affect the amps output potential, but Exeter's speakers' sensitivity and distance from his listening spot remain a constant.
 

·
Registered
Joined
·
804 Posts
Quote:
Originally Posted by Clmrt
"Shouldn't be a problem. You may need to increase the channels (in your receiver's menu) output from your receiver to the outboard amp for the channels that are receiving less power."


Not.


That has nothing to do with an amp's potential output, but rather the sensitivity of the speaker and distance to the listener.


You could probably get away with a few watts and probably never notice, especially when high-passed. 200w vs 100w = 3db difference at full volume, which would have probably deafened you by then anyway.
What?


What I was suggesting is just as sivadselim said. Please explain to me how using an SPL meter at your listening position and adjusting channel trims to match output of all your speakers at your desired listening level is "NOT" :confused: correct...
 

·
Registered
Joined
·
545 Posts
Quote:
Originally Posted by spillz564
What?


What I was suggesting is just as sivadselim said. Please explain to me how using an SPL meter at your listening position and adjusting channel trims to match output of all your speakers at your desired listening level is "NOT" :confused: correct...
that's not my point.


The OP asked about using 105 and 180 watts in the same 7.1, and the effect it would have.


Of course you still have to trim for balance.


But you said you had to increase the levels for the amp with less power. What if the speakers on that amp are 8db more sensitive?
 

·
Registered
Joined
·
1,415 Posts
Quote:
Originally Posted by Clmrt
that's not my point.


The OP asked about using 105 and 180 watts in the same 7.1, and the effect it would have.


Of course you still have to trim for balance.


But you said you had to increase the levels for the amp with less power. What if the speakers on that amp are 8db more sensitive?
Give me a break. Are you always this anal and abrupt? I've seen you resond this way in other threads as well. If you were questioning speaker sensitivity, which is valid, you should have said so in your original response rather than just "Not.". :rolleyes:


The point of the question was can he get the same levels out of the surround running on the lower output amp versus the higher output amp. Calibrating with an SPL meter and adjusting the gain up or down will accomplish this.


That said, will he be able to achieve a reference level peak of 105 dB with that amp and those speakers? Possibly, but it is dependent on the seating position, sensitivity of the speakers, and room acoustics. I believe THX specifies for a 3000 ft^3 room, the front speakers need 100 watts RMS power and the surrounds need 50 watts RMS. This assumes speakers with a 4 ohm load, but I am not certain of the sensitivity.


This tells us a couple of things, either the THX standards account for the seating position being closer to the speakers or it is assumed that the peak SPL from the surrounds will be something less than 105 dB. My suspicion is the former as I have never heard of a different reference standard for THX by speaker position. Just use one of the SPL calculators available online and plug in your specs (watts, sensitivity, distance, number of speakers, etc.) and it will give you an idea of the peak SPL you can achieve from the surrounds.


After all of the typing, I am very certain that 105 watts x 2 to the rear surrounds will more than generate 105 dBs.
 

·
Premium Member
Joined
·
9,326 Posts
Ok guys...DO NOT let this get into a attack match.


Comments like...


"Give me a break. Are you always this anal and abrupt?"


And


"You have GOT to be kidding me."


...are not welcome and offer nothing to the chat.
 

·
Registered
Joined
·
1,415 Posts
David, point taken, and I should not have said it but comments like "Not." on a repeated basis are pretty condescending.
 

·
Registered
Joined
·
764 Posts
Discussion Starter #13
Lots of input here. The speakers will be the same. I was going to put a 5 channel amp on the fronts, center, and two rears and a 2 channel amp for the remaining two rears. But Raving's post made me think maybe I should do a nice 2 channel amp for the l/r and a lesser watt rated 5 channel amp for the rest. The center doesnt need much does it?
 

·
Registered
Joined
·
6,946 Posts
The center is very important and from most posts on the subject I can recall, seem to indicate the center should be comparable power-wise to the front/main speakers. But is it absolutely necessary, likely not.


I would also consider using a decent 2-ch amp for the fronts and a 5-ch amp for the center and surrounds.


I have 250 w/ch on the front three and 120 w/ch for the side and rear surrounds. I have no trouble setting the channel trims with reasonable ranges.


The trims for my setup are:

Left front: 0dB

Center: +0.5dB

Right front: +0.5dB

Left side: -0.5dB

Right side: -2.0dB

Left rear: +4.5dB

Right rear: +2.5dB


Note that in general, the surrounds for the left side need to be louder for my arrangement. The big difference between the sides and rears is mostly because they are from a different mfg. and the difference in trims is close to the difference in rated sensitivity between the brands. The remaining difference is attributable to listening position difference between side and rear.


Seems to work fine for me.
 

·
Registered
Joined
·
16,827 Posts
Quote:
Originally Posted by clrmt
Would some EE chime in and set me straight?
We don't need an EE. And I'll attempt to set you straight.


The answer to the original poster's question is:


NO, IT WILL NOT BE A PROBLEM.


Why will it not be a problem?


BECAUSE HIS RECEIVER/PRE/PRO MOST LIKELY WILL ALLOW HIM TO ADJUST THE OUTPUT OF EACH OF HIS CHANNELS INDIVIDUALLY.


THE SPEAKERS' SENSITIVITY AND DISTANCE ARE INCONSEQUENTIAL TO THE DISCUSSION AND A COMPLETELY MOOT POINT. AS I SAID, THAT'S SOMETHING CONSTANT AND INVARIANT THAT ISN'T GOING TO CHANGE OR BE DIFFERENT WHETHER EXETER USES A SINGLE 7 CHANNEL AMP OR 7 MONOBLOCKS. HE'LL STILL HAVE THE INDIVIDUAL CHANNEL TRIMS TO COMPENSATE FOR ALL THE VARIABLES WHICH AFFECT EACH CHANNEL'S OUTPUT, BE THAT SENSITIVITY, DISTANCE, ROOM EFFECTS, AMPERAGE, ETC., ETC., ETC..
 

·
Registered
Joined
·
545 Posts
Quote:
Originally Posted by sivadselim
We don't need an EE. And I'll attempt to set you straight.


The answer to the original poster's question is:


NO, IT WILL NOT BE A PROBLEM.


Why will it not be a problem?


BECAUSE HIS RECEIVER/PRE/PRO MOST LIKELY WILL ALLOW HIM TO ADJUST THE OUTPUT OF EACH OF HIS CHANNELS INDIVIDUALLY.


THE SPEAKERS' SENSITIVITY AND DISTANCE ARE INCONSEQUENTIAL TO THE DISCUSSION AND A COMPLETELY MOOT POINT. AS I SAID, THAT'S SOMETHING CONSTANT AND INVARIANT THAT ISN'T GOING TO CHANGE OR BE DIFFERENT WHETHER EXETER USES A SINGLE 7 CHANNEL AMP OR 7 MONOBLOCKS. HE'LL STILL HAVE THE INDIVIDUAL CHANNEL TRIMS TO COMPENSATE FOR ALL THE VARIABLES WHICH AFFECT EACH CHANNEL'S OUTPUT, BE THAT SENSITIVITY, DISTANCE, ROOM EFFECTS, AMPERAGE, ETC., ETC., ETC..
OK, I know that. Everybody KNOWS that. Read the 2nd sentence in paragraph one of post number two.


That sentence says "You may need to increase the channels (in your receiver's menu) output from your receiver to the outboard amp for the channels that are receiving less power".


That's what I don't agree with. Does the use of a low powered amp automatically mean that those trims will be higher than the others?


No.
 

·
Registered
Joined
·
16,827 Posts
IT SAYS MAY, DOESN'T IT?!?!?!?!?


WHAT IS IT YOU DISAGREE WITH?
 
1 - 20 of 27 Posts
Status
Not open for further replies.
Top