Love these forums.....all kinds of usefull and helpful stuff.....although they seem to like to go off into strange tangents now and then...(keeps it interesting though)...I am ready to take the plunge with the 950, and was wondering if the "rear surrounds" have much information present when playing with various types of 6.1 - 7.1 sources...I guess my question is, will a 200 watt amplifier be overkill for my rear surrounds.....is there much info to "amplify"? I'm using old JBL L100 floor standing speakers for my rear surrounds now (using a Parasound CSE6.1), with an old Fosgate 4100 amp @ 200 watts per channel powering them, and lets just say they don't kick butt in my set up......they add a little with some music and movies...nothing spectacular....I don't think it's the fault of the JBL's or the Fosgate amp, they both are definitely good quality, and have served me well over the years.......but I also don't have all of the newest surround options that are available now......and the various tweaks available to adjust for room, crossovers, etc........like with the 950......I know I'm still living in the 20th century, with o.l.d. equipment......I want to join the 21st century!!!! Just really curious about your thoughts on those "rear surround" effects through the 950.......

For movies, it is mainly ambience that is put into the surrounds most of the time. Occasionally, there is more activity such as specific pans of jets and such, and sometimes some low frequency effects creep into the surrounds. The surround speakers on a movie dubbing stage do not particularly have any huge low frequency capability, probably cutting off around 50Hz, so generally the mixing engineers do not put such material into them (I spend a lot of my working time on movie dubbing stages). For music SACDs and DVD/As, anything goes, although I would think that most mixing engineers would not put bass heavy instruments into the surrounds.

Generally, I would think that 100 or so watts would be adequate for your surrounds, especially if you use bass management and direct the low bass to a subwoofer. The low bass is where most of the power demand is, and removing this demand relieves your amplifier of having to deal with reproducing this frequency range, thus conserving power.

That being said, there is no downside to having 200 watts driving your surrounds. You will probably not utilize all the power, but on the other hand, it will not hurt to have it.

[This message has been edited by soundhound (edited May 16, 2003).]

You really want to match wattage for all speakers in your setup.

More and more mixing studios use large, matching monitors for all channels and are putting considerably more bass into the surround channels.

For music, you could have a lot of activity in the surrounds, although most mixes don't have a back surround encoded (unless you force the processor into a 7.1 matrix mode).

Dan

Sorry, that is not true for movie mixing stages. The surrounds are usually the same ones (or very close) to those seen in a local cinema, and they do not have much bass response below 50Hz or so. The L,C,R stage speakers almost always have two 15" woofers in an 8 cubic foot cabinet, tuned for 30Hz. The spectrum above 500Hz or so is covered by a constant directivity horn and compression driver, occasionally with a smaller horn and driver covering the highest frequencies. The subs usually contain a single 18" driver in an 8 cubic foot cabinet, and depending on size, the room may have from one to four of them. JBL is the dominant supplier in this market. Mixing stages for film do not use bass management as a home theater would.

The situation for strictly music mixing studios can be significantly different, as there are no real standards for the speaker array used in these rooms. Movie mixing stages must conform to standards so that the mixes performed in them will translate to all of the local cinemas with mimimal change in the sound of the mix.

[This message has been edited by soundhound (edited May 16, 2003).]

I've only been using a model 950 for a month or so, and it's my first experience with a 7.1 set-up. However I've spent a lot of time sampling all sorts of soundtracks / music, using all of the 950's modes, and with the exception of 7 STEREO mode, my conclusion is that there's not much in the center rear channels that is likely to strain most amp / speaker combinations.

All four of my surrounds are Bose 301 Series IIIs and all of them have more than 100 Watts available to them. The center rears normally have bridged NAD 2155s driving each of them (125 Watts continuous, 250 Watts peak), with the 950's center rear set to "small" with an 80 Hz crossover. However last week I took one of the amps out of the system to be used elsewhere for a while. I'm currently using the other unbridged to drive each center rear (55 Watts continuous, 100 Watts peak). I've not reduced my listening levels and to be honest I don't hear any "straining" of the center rears.

Yes I believe that more power is always better. (Your 200 Watts should be more than enough.) But in practical terms there's not a lot of tough content showing up in those center rear channels - yet. The exception in the case of the 950 is, as I mentionned above, the 7 STEREO mode. That one definitely gives those channels something to do. But since I don't like the way it sounds, I'm not planning on using it at all.

Regards.

Jeff Mackwood

Some DD EX and DTS-ES soundtracks have quite substantial content in the rears...

If you ever decide to get into hi-res multi-channel music battle, such as with a universal player, most of those discs feature plenty of information in the surrounds. That's probably a given but I just wanted to point it out after demoing "Dark Side of the Moon" for a friend and watching his jaw drop!

"Some DD EX and DTS-ES soundtracks have quite substantial content in the rears..."


There may be "substantial content" in the surrounds of some movies, but if you did a spectrum analysis per channel and compared the content to what is in the other speakers (especially the sub) at that point, I think you would find that the total energy content at that point in the surrounds is quite nominal. This is simply because the surrounds in a cinema cannot take the extremely heavy demands of very low frequencies, and no mixing stage will put out a mix that would be incompatble with the end user (the neighborhood cinemas).

Hollywood may occasionally produce some really crappy movies, but the post production people who finish them know very well what they're doing

Low frequencies are the very area where most of the power demand resides, and if you eliminate them, much less power is required. You are also significantly reducing the power demand if you use bass management and have your surrounds set to "small"

For the record, in my studio I use tube amps rated at 60 watts per channel for my side surrounds and 40 watts per channel for my rear surrounds, and I do not clip these amps. I run these surrounds full range, and regularly play movies at the reference mixing level. I also play master music recrodings which can and do have significantly more dynamic range than what ends up in the movie's soundtrack.

[This message has been edited by soundhound (edited May 19, 2003).]

i'm a little confused (what else is new?).

by rear surrounds, i imagine you mean back surround and not surround.

this would limit your sources to DD-EX, DTS-ES and matrixed modes, as multi-channel audio only discs don't use these channels at all.

in any case, the general rule for selecting amplifier power is to use an amp that can deliver twice the power of the speaker's continuous power rating, or, 3 db headroom. in critical listening environments, the recommendation is for 6 db (4 times the speaker's cont. power rating) headroom.

this headroom is to insure that transient peaks are delivered to the speaker cleanly...no distortion. distortion (the amp into clip kind) is what kills speakers and can be damaging at surprisingly low power.

unless you have clip indicators on all of your amps and you watch them instead of the movie, you mostly won't know when the amps clip during a transient peak.

all of this means that if your speaker is rated at 100 watts, continuous, you should use an amp of 200-400 watts. this is playing it safe and is the main reason that higher power amps sound better (assuming specs that are real).

also to consider is the speaker's sensitivity. as i recall, soundhound uses horns that have extremely high sensitivity. this means that they require little power to acheive reference level (like, only a few watts) so 40-60 watt amps means he has gobs of amp headroom. my speakers require 10 times the power of soundhound's to reach ref level.

Bosso:

My surrounds are regular direct radiators, the same ones used in a lot of medium sized cinemas (JBL 8330). Since I mix for this enviornment, I need to have speakers similar to the ones that the music will end up on. Since a theater uses horns for the fronts, my fronts (which are horns) fit this requirement.

My only point was that generally (i.e. few exceptions), the power requirements for the surrounds for movie use are more modest then some would imagine.

For strictly music SACD etc, anything goes, and probably does, so this is where you would want to have sufficient power for those instances when a low synth note is coming from the surrounds, for instance. However, if the surrounds are set to "small", this bass would be re-directed to the subwoofer, lessening the power requirement significantly.


[This message has been edited by soundhound (edited May 19, 2003).]