I need to replace my Nad M25 Power amplifier.

[Pablo2k]

Pablo..
Do not use a bridged amplifier with those loudspeakers..
Typically, a bridged amplifier for home applications do not like low impedance loads..
If U want or need the high power, procure an amplifier that is capable of putting out the target spec without bridging..

Just my $0.02...

I’m reading that between 160w and 80w it’s only a 3db difference.
I usually listen to movies at -20db on the receiver.
So I guess going from 5ch at 160w to 5ch at 80w might not be a problem for me?

 

[AcuDefTechGuy]

I’m reading that between 160w and 80w it’s only a 3db difference.
I usually listen to movies at -20db on the receiver.
So I guess going from 5ch at 160w to 5ch at 80w might not be a problem for me?

I think a solid high quality 80W x 5Ch driven amp that is stable down to 2 ohms is usually more than enough if you are sitting about 12' away (LP).

I used to own a 50WPC Harman Kardon AVR that did just fine powering 5 large speakers in an 18x20 room w/ 12' LP.

 

[PENG]

I’m reading that between 160w and 80w it’s only a 3db difference.
I usually listen to movies at -20db on the receiver.
So I guess going from 5ch at 160w to 5ch at 80w might not be a problem for me?

Most likely not a problem, but did you use the calculator?

 

[Pablo2k]

Most likely not a problem, but did you use the calculator?

102.3 down to 99.3 if I’m at 20’ 2 channels
All 5:
106.3 down to 103.3db

 

[PENG]

102.3 down to 99.3 if I’m at 20’ 2 channels
All 5:
106.3 down to 103.3db

Did you mean you sit 20 ft from the 683?

 

[Pablo2k]

Did you mean you sit 20 ft from the 683?

Yes.
My room is about 14 feet wide by 24 feet long.
There are windows at 0 feet and 24 feet.
The back of the front speakers are about 18 inches from the wall and about 11 feet apart; these are the 683s with the htm61 in the middle.
On the back wall, so almost 24 feet away, are my 684s, also about 11 feet apart, but 4 inches from the wall.

The subs are by the 683s (two Def Tech supercube reference)
I either sit near the back wall to the left or about 19 feet away to the right.
This is not a dedicated theater room, it’s like a family room filled with toys in the middle no matter how many times I pick them up! Kids 5 and 9...

If I’m alone watching a movie, I would move lazyboy chair in the middle of room at about 16 feet from the mains.

 

[PENG]

Yes.
My room is about 14 feet wide by 24 feet long.
There are windows at 0 feet and 24 feet.
The back of the front speakers are about 18 inches from the wall and about 11 feet apart; these are the 683s with the htm61 in the middle.
On the back wall, so almost 24 feet away, are my 684s, also about 11 feet apart, but 4 inches from the wall.

The subs are by the 683s (two Def Tech supercube reference)
I either sit near the back wall to the left or about 19 feet away to the right.
This is not a dedicated theater room, it’s like a family room filled with toys in the middle no matter how many times I pick them up! Kids 5 and 9...

If I’m alone watching a movie, I would move lazyboy chair in the middle of room at about 16 feet from the mains.

If you sit 16 feet from the mains then by THX standard (85 dB spl average 105 dB peak) you will need an amplifier that can deliver about 500 WPC into 4 ohms. 85 dB average is loud, something like what you would experience in a movie theater that follows that follows the THX stamdard. Problem is, the 683 is not designed to handle more than 200 W, except for the short duration dynamic peaks.

The Monolith can do about 350 W into 4 ohms at 0.1% THD so I would say they are a good match for the 683.

With the help of two or more good subwoofers, even a 200 W X 5 can get you THX reference level of 85 dB average if 5 speakers are firing to the same level.

If you don't listen to the 85 dB average (THX/cinema) spl, and is happy with 75 dB average instead, then a 200 W X5 Monolith will do well with those speakers, with a comfortable margin of 9 to 12 dB of headroom. I find 75 dB average for movie is loud enough.

 

[Pablo2k]

If you sit 16 feet from the mains then by THX standard (85 dB spl average 105 dB peak) you will need an amplifier that can deliver about 500 WPC into 4 ohms. 85 dB average is loud, something like what you would experience in a movie theater that follows that follows the THX stamdard. Problem is, the 683 is not designed to handle more than 200 W, except for the short duration dynamic peaks.

The Monolith can do about 350 W into 4 ohms at 0.1% THD so I would say they are a good match for the 683.

With the help of two or more good subwoofers, even a 200 W X 5 can get you THX reference level of 85 dB average if 5 speakers are firing to the same level.

If you don't listen to the 85 dB average (THX/cinema) spl, and is happy with 75 dB average instead, then a 200 W X5 Monolith will do well with those speakers, with a comfortable margin of 9 to 12 dB of headroom. I find 75 dB average for movie is loud enough.

Wow, That’s a lot of power.
My 160w was more than brought for me since I never listened to reference level.
My M15HD was always between -30 to maybe tops -20db volume.

 

[PENG]

Wow, That’s a lot of power.
My 160w was more than brought for me since I never listened to reference level.
My M15HD was always between -30 to maybe tops -20db volume.

But you can't go by the volume position unless that unit has been calibrated to a certain standard. For example, if you had run Audyssey properly, then Vol 0 should get you reference level at you main Mic/seat position. Actually I should emphasize that this is the case for Denon and Marantz units and I am not really sure if it is the same for the NAD M15HD.

By the way, what are the min/max, i.e. the range for the M15HD's volume control?

 

[Pablo2k]

But you can't go by the volume position unless that unit has been calibrated to a certain standard. For example, if you had run Audyssey properly, then Vol 0 should get you reference level at you main Mic/seat position. Actually I should emphasize that this is the case for Denon and Marantz units and I am not really sure if it is the same for the NAD M15HD.

By the way, what are the min/max, i.e. the range for the M15HD's volume control?

Volume goes from -77db to +5.5db
It’s pre outs are rated at 8 Vrms 600ohms 0.005%thd

 

[PENG]

Volume goes from -77db to +5.5db
It’s pre outs are rated at 8 Vrms 600ohms 0.005%thd

Fyi, below are the ranges of other AVRs, it may not seem much numerically, but you already know that 3 dB means a factor of 2 in terms of power output.

Denon, Marantz: -79 to +18
Yamaha : -80 to +16.5
Sony ES : -92 to +23
Onkyo : -81.5 to +18
Arcam : 0 to 100

So you can't go by the volume position alone. I did read the manual, but for an expensive unit I was disappointed to find so few details in it, compared to the more mass produced D&M, Onkyo and Sony's.

Question remained: Did you run Audyssey and have it turned on? That would have made a difference too to the correlation between the volume setting and the sound level you are getting from the calibrated position.

By the way, the M15HD is not rated 8 V 600 ohms at 0.005%, it is 2 V, according to the manual. 8 V is the maximum.

 

[AcuDefTechGuy]

If you don't listen to the 85 dB average (THX/cinema) spl, and is happy with 75 dB average instead, then a 200 W X5 Monolith will do well with those speakers, with a comfortable margin of 9 to 12 dB of headroom. I find 75 dB average for movie is loud enough.

I hate THX theaters because they are way too uncomfortably crazy loud for me.

 

[Pablo2k]

Just to update to everyone, and not leave this post completely hanging.
I brought the Mcintosh MC126 home and it didn't work, turns out my coworker never tried it so i returned it.
I got a Crown XTi2 4002 (650wpc 8ohms) from another co-worker for $200 which is a really good price, and I purchased two Crown XLS 1502 (300wpc 8ohms).
I will keep my Nad M25 and eventually have it repaired, a local shop by me said their estimate is free.
Thank you for all your help.
Very knowledgeable people here!