Can you tell us about how heavy the 950 is?

While I know that one of the beta testers (RAF) is doing this, I personally would only put the ICBM before the 950, never ever after it. Follow:

The signal coming into the 950 goes through processing that includes bass management and time alignment. If your speakers are not all the same distance from your seating position, then the time alignment will compensate by applying appropriate delays to each set of channels. Now, if you apply bass management to those channels after the delays are incorporated, you could be asking for trouble.

Just one example: imagine taking the bass from your small fronts and small surrounds and outputting the combined result via the sub out. If the front and surround channels have different delays applied to their respective signals, they may then end up out of phase (slightly or severly) with each other when their bass info is combined. This can cause all sorts of re-inforcing and cancellations (bass peaks & dips) in the sub channel output. Now imagine combining the bass from each group of channels (fronts, centre, surrounds, LFE) each with its own delay, and you have the recipe for a possible sonic mess. Not a good idea, IMHO.

Which is why it's always better to have bass management before time alignment; or in this case, have the ICBM before the 950.

Also, if you do use 2 subs, you'll have to make sure they are the same exact distance from the listening position since you can't level match and time align them independently.

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Sanjay

[This message has been edited by sdurani (edited February 14, 2002).]

I'm not sure this would really be a problem with subs, except in extreme cases, as the frequencies involved are so low. At 100 Hz, each sound "wave" is going to be about ten or eleven feet long. I don't think a delay of two or three ms is going to put that wave significantly out of phase. At 30 Hz, your waves are about 35 feet long... the problem would be even less obvious.

Matthew,

Agreed. It may not make much difference at very low frequencies; especially for small rooms. If you've got a 1ms or 2ms delay at 20Hz or 30Hz then the problem (while there) will most likely be inaudible.

However, it is not uncommon in some home theatres to have speakers which have a 5 to 10 foot difference in distance from the listening position. A 5ms or 6ms delay on a 80Hz or 100Hz signal (both of which could end up in the subwoofer) would place one signal 180 degrees out of phase with the other. While you wouldn't get perfect cancellation (they are different signals after all), you will get bass problems. Even small delays can lead to the bass sounding muddy instead of tight.

The bottom line was that there is a chance of creating bass problems by placing the ICBM after the 950. And my point was that I don't think it's worth the risk to do that when the solution is so simple: place any bass management before the 950. You can get lucky with the former set-up, and either not have a problem or have phase problems that are inaudible; but what do you have to gain by taking that risk?

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Sanjay

Stereo subs.

I agree, though, that bass management is better done within the processor. For the time alignment reason and also because I'd rather have it done in the digital domain.

Hence, my wish list for the 950 successor includes dual sub output. Who knows if they'll put it in? I can think of many uses for it though.

I plan on putting my ICBM after the 950, and I don't think time alignment will be an issue. Correct me if my logic is faulty.

I am setting the center and surround crossover point at 60, 80, 100 - whatever works. Then set for no sub. Not sure exactly this is done in the 950, but I'm sure there is a way to send all bass material to the mains.

The 950 center and surround output go directly to the amps, but the main L/R goes to the ICBM first, using it as a stereo crossover for the main outputs. There I set the main crossover to whatever I want (60 or 80 Hz most likely). No recombining of delayed bass to send to the sub, just a redirection of the bass in the mains, which is all of it since I set the 950 for no subs. I can have stereo subs, or mono - the ICBM can do either.

In the past, I have had very good success with slightly different crossover frequencies for the HP (to mains) and LP (to subs). I can do this by splitting the main L/R signal out of the 950, and sending a full range signal to the sub and use my sub's continuously variable LP crossover for the bass. Now I have independently variable HP and LP crossover points.

I also want to have the option of 4th order L-R crossovers for the mains. The ICBM only allows 2nd (12dB) order Butterworth HP, and either 2nd order or 6th order or LP. But... with the set up described above, I have lots of unused inputs available on the ICBM. So I can set the ICBM for 12 dB HP and LP. Take the main L/R outputs and feed them into the L/R surround inputs. The surround outputs are now actually the main L/R signal filtered by 2 cascaded 2nd order Butterworths. There you have it - a 4th order (24dB) L-R crossover! In case you are unaware, a 24dB L-R is 2 cascaded 12dB Butterworths.

So if you think about it long enough, the ICBM is a VERY flexible box, particularly if you aren't using it to cross over all channels of your HT system.

Did this make any sense?

Cheers,
Chris

Chris,

Yes, that does make sense. In essense you have done most of your bass management (re-routing bass from other channels to your mains) before the time alignment step. At that point you're basically splitting the signal from your mains and directing the correct info to the correct drivers (Left low-pass to the Left sub, Left high-pass to the Left speaker; Right low-pass to the Right sub, Right high-pass to the Right speaker).

Clever! It never occured to me to use the ICBM as simply a crossover instead of a complex bass management tool.

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Sanjay

Sanjay,

I notice that you mentioned that I'm using the ICBM after the pre-pro and that you would never do this because of time alignment issues. While I don't share the same passion that you have for time alignment and its implications I can appreciate and respect your position.

However, let me clarify my use of the ICBM with the 950 a bit. Ideally, I would not have wanted to use the ICBM at all since the 950 offers bass managment internally. However, having both a 5.1 DVD-A player and a 2 channel SACD player (my Sony 9000ES), then without the ICBM I would have to choose which unit to connect to the direct analog inputs for bass management. (That's a bit like you asking me who my favorite grandchild is!).

I figured out a way to connect the ICBM after the pre-pro (as mentioned in the ICBM manual) for processing STEREO signals from the SACD player. First I pass the L and R front channels and the Subwoofer channel from the 950 through the ICBM. Then the four surround channels go directly from the 950 to their respective amps. Therefore, the issues you raised with time alignment and, more specifically, phase prolems introduced by the surround channels into the ICBM are not applicable here.

Would I prefer *not* using the ICBM after the 950? Of course, and for some of the very reasons you mentioned. The less pieces in the puzzle the better. But until I eventually get a single player for both DVD-A and SACD multichannel (like the new Pioneer or such) this at least gives me some bass management of SACD 2 channel sound.

I'm continuing to investigate some alternative ways to get energy to my subwoofers from SACD 2 channel without the ICBM and if I come up with any viable options I'll share them (probably over on the HTF since my time to surf all the sites is limited)

Take care.

Hi Robert,

Thanx for the clarification; much appreciated. You're essentially doing what Chris does. The bass routing/combining and subsequent time alignment has already occurred (and in that order) inside the 950 before you pass your mains & sub channel info to the ICBM. Done this way, very little (if any) bass re-routing occurs after the time alignment.

What I was wary about was using the ICBM as a full bass management tool after you've time aligned your speakers using the 950. In that case, you'll be taking signals form the mains, centre, surrounds & LFE channels each with their own individual delay and combining them. As opposed to your set-up, the above configuration can lead to all sorts of phase & timing problems.

Of course, you may not be experiencing these problems because you're not doing heavy duty bass re-routing & combining with your ICBM. However, think about the impression others are getting about your experiences. Folks, like me for example, read that you are using an ICBM after the 950 and that you are not experiencing any of the possible problems that can occur, and then get the impression that they can do the same. Do they know that you're not using the ICBM to combine bass info from various channels? If not, they may be in for a surprise when they hook up their ICBM between their 950 and their amps and expect everything to sound like a coherent soundfield.

You may want to clarify this at some point (even if it's only at HTF).

BTW, as to my passion about time alignment, let me ask you a simple question: do you use time alignment on the receivers or pre/pros in your home theatre? If so, why?

Best Regards,
Sanjay

Hey Folks,

Matthew asked how much the 950 weighs - I'm not going to unhook it to weight it, but it's somewhere in the 15-20 lb range.

Dimensions are: 5" high, 17" wide, and 14.5" deep.

I had commented before that my wife and I couldn't hear a difference when switching between the coaxial input and the analog input. Well, I revisited that test yesterday when the wife was out shopping.

Is there a name for that magic volume level where your speakers disappear and you only hear the music? On my system, that's around 70dB. At that level, if I try to audition just one track, I often end up listening to the whole disk. Well, while I still didn't hear a difference at wife-friendly levels, I did hear a difference at my personal reference level - and I prefer the sound from the 950's DACs.

The difference is subtle, similar in my opinion to when I swapped in better interconnects. Using mostly acoustic material during my tests, I found the 950 has a better soundstage, and that it sounds crisper without being bright or shrill. One of my favorite disks is Muddy Waters, "Folk Singer" (MFSL gold disk) and it just sounds amazing through the 950. A little bit of glare that I hadn't noticed before was removed going through the 950's DACs.



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JeffLH