I have several questions regarding the ICBM, but first let me describe my setup and my objectives. At present, I don’t yet own either an ICBM or a good subwoofer. I’m hoping you guys can help me determine whether the ICBM can function as I hope it will if used in a somewhat unconventional speaker/subwoofer configuration that I’m considering buying.

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Introduction:

My current system consists of the following:

Panasonic RP91 DVD-A player (built-in DD & DTS decoders)
Arcam AVR200 receiver
Arcam 2-channel amp
floor-standing speakers here
bookshelf-sized surrounds and centre here and here
an old, poor-quality subwoofer

I unfortunately have a square-shaped 13’ X 13’ listening room, which presents a dilemma when only one subwoofer is available. Corner-placement = severely unbalanced bass from left to right. Middle-wall placement = sloppy, inefficient bass output and magnetic interference with a television. In researching possibilities for a 2-subwoofer solution, I came across the Vandersteen 2Wq model, which looks very promising for music, and should be adequate for movies as well in a small room like mine. Here are two links: Product Info and Reviews

This subwoofer purposefully has no RCA inputs, only speaker wire inputs. Details on connectivity can be obtained using the links above, but simply put, each sub would share the same signal as either the (L) or (R) front speakers... there are no other possibilities. For all intents and purposes, my system would now consist of two truly full-range (L) and (R) front speakers capable of deep bass. Buying these things would constitute an awfully big investment for me, and I doubt I’d be willing to do so unless the ICBM is capable of performing full, uncompromised bass management via the front channels, without connecting a subwoofer to the subwoofer outputs. There's no rush, so anyone who wants to take a crack at this can take their time.


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Questions: - always assume that the LEFT/RIGHT RECOMBINE switch = ON

A.
First off, I need to know if the .1 channel will be reproduced properly when distributed to the main speakers. Consider the following scenario: Suppose you have 3 identical subwoofers, each of which is set to precisely the same volume. Now connect one subwoofer to the ICBM’s subwoofer output, and the other two subwoofers to the ICBM’s (L) and (R) front outputs. Now connect something with deep bass into the ICBM’s LFE input, but nothing else. If you were to toggle between
a) RECOMBINE OFF
b) RECOMBINE ON (with the solo subwoofer deactivated)
would the perceived volume of the LFE channel be the same for both configurations? For my proposed setup to work, they would need to be within a few decibels of each other.

B.
Will the LFE MIX knob still work, so that the .1 channel can be fine-tuned independently of the rest? (I could still adjust the volume from within the Panasonic’s menu, so this is a matter of convenience, and not a deal-killer if it doesn’t work... but it would be nice if it did)

C.
What happens to the deep bass from the centre channel? Is it halved and sent to the front speakers? (Pretend that in the same example above, you simply plugged the source into the centre channel input and the solo subwoofer into the centre channel output, instead of using the subwoofer input/output.)

D.
What happens to the deep bass from the surround channels? Will the ICBM correctly distribute the deep bass from the (L) and (R) surround channels to the corresponding (L) and (R) front speakers, or will it simply half the signal for each surround channel, sending it to both front speakers equally?

E.
Use of the MONO/STEREO switch in a setup like the one I’m considering isn’t documented in the manual. Is the ICBM capable of preserving the stereo image for the surround channels? Would there be any unexpected side-effects to using this switch?

F.
The front LEFT/RIGHT crossover control won’t have any effect on the sound from any of the speakers, will it?

G.
Will the SUBWOOFER LEVEL control have any effect on the strength of the subwoofer signal being routed to the front speakers?


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Additional Questions:

H.
The LOWPASS SPECIAL/NORMAL switch isn’t fully documented. In a standard single-subwoofer setup, does this switch change the slope of the crossover on the subwoofer only, or does it also contour the slope of any speakers being crossed-over? In a setup like mine which has no subwoofer, will this switch still affect the subwoofer signal (which is being distributed to the front speakers), or does it only pertain to the signal being sent to the RCA-style subwoofer output jacks?

If any of you can shed some light on these uncertainties, it would go a long way towards helping me decide whether using these 2 Vandersteen subs is a viable option or not. This is a bit of a brain teaser, and if I’ve missed anything, feel free to point it out. Thanks in advance.

Jennifer

Let me explain what I did which I doubt will answer all your questions, but maybe provide some insight.
I have the following configuration, which is a bit unorthodox but works out well for me.

I don't have a 'square room' and found excellent coupling while not ideal but 'good' non-localization by using a corner area (adjacent to a main wall) and experimenting with the position of the sub within that area.
Get on the floor with some heavy bass music and crawl around the room to find the point where the bass is difficult to localize. The more areas where it is difficult to localize the better, especially around the main listening area of course.
I have all satellite speakers and a powered sub.
So first of all, I have all satellites set for LARGE so the ICBM does all the work of a crossover. The one exception is the setup in the DVD player, where I left the rear speakers set to SMALL so they would not deal with any frequencies below 100Hz (the default of the player).
The reason I did this is I only use the rear surrounds with the player.
I either listen in 5.1 EXT or Stereo.
I also took the SUB OUT in the DVD player so all LFE information will be directed to the Front MAINS.
Again, the ICBM will crossover the bass info to my sub which is just 'hanging' on the output of the ICBM. No LFE signal input.
A quirk of my system is I have the 3 front channels driven by an external amplifier, which are fed by the 3 pre amps out of my receiver, to the ICBM, and to the amplifier so all frequences above 80Hz are only processed.
Based on this configuration, I have the LCR speakers set to 80Hz, the surrounds set to bypass, (they are still amplified by the receiver but cut off at 100Hz by the DVD player, remember?)
I have no need to use 'recombine' since I am not dealing with any full range speakers.
I do use 'special' for the filter slope because I am using a THX speaker system. The 'special setting' is one you need to experiment with, the same goes for any polarity setting on the sub. The sub is set for external and I use both level settings on the ICBM and sub set at 0 gain which gives me about 80db with a 75 db test on Avia which apparently has a miscalculated subwoofer output signal.
The left/right mono/stereo are mainly for one or two subs. They will have little if any effect on one sub.
I think you might be better to use a quality sub(s) that WILL allow you an external input (ie; from the ICBM).
I would 'round up' the bottom end of your main front left and right speakers, if they go down to 40Hz, I would cut them off at at 60Hz, etc.. and let the sub handle all below that.
This will take some 'load' off your main amps and let the sub work those. This may even make your mains sound more detailed.
The subwoofer level on the ICBM has no effect on the other speakers.
Is your center channel the same size as your front L and R? IF so, they should be 'cutoff' at the point as your L and R front speakers.

[This message has been edited by DaleB (edited November 22, 2002).]

[This message has been edited by DaleB (edited November 22, 2002).]

Thanks for the quick reply.

On several occasions I've tried to find the best place for my subwoofer... crawling around and so forth, just like you mentioned. After having lived with my present setup for nearly a year now, experience has made it clear that any "deep bass upgrade" I make will involve using 2 subwoofers. Square-shaped rooms are vilified for their poor acoustics, and where deep bass is concerned, a single sub just presents too many drawbacks, whereas 2 symmetrically placed subs can alleviate many of these problems.

To be honest, I'm confident that I'd have no trouble putting together a normal system that has a couple of conventional subwoofers. Hook everything up, set the crossover levels, fiddle with the relative volumes, and pray the house was built with stern stuff. Piece 'o cake!

Nope, my goal here is to find out, with the help of ICBM owners, if this thing can perform full bass management via 2 full-range main speakers only, without connecting a subwoofer to the SUB OUT jacks as one normally would. Why? Because after reading about these Vandersteen subwoofers, I think they may offer great potential for 2-channel and multichannel music. It's worth investigating.

I guess it's possible that the ICBM wasn't really designed for this purpose, but I hope one of you can prove me wrong!

Vandersteen certainly makes fine speakers, and if that is the course you are considering, the ICBM is not going to help you.
You may (if you haven't already) download the ICBM instructions (pdf.) and study the various configurations.
I don't believe any will fulfill that configuration as shown on the Vandersteen site.
Good luck in any case!