Just got my 950 yesterday. It is everything I wanted except one small glitch. 6 channel pass through bass management cannot really be turned off. I Have an ICBM and want it to do all of my bass management. This is impossible with the current design.


Desperately wanting to not return my 950 and start looking all over again, I popped the lid and discovered the built in bass management to be a simple analog circuit on the 591 card inside. I'm testing a relatively simple "Non-Factory Authorized" modification that allows for a true 6 channel pass through. Over the next week I'll document my findings. If anyone is interested in the details....Let me know

Effects on the warranty of any internal modifications?

There is a way not to get double bass. Just use the 80 Hz analog crossover.

You can also use an ICBM for the entire unit. Config the 950 so that all speakers are large, with no sub (that reroutes the LFE to the mains). Then just connect the 5 but not the .1 of the 5.1 pre-amp outs of the 950 to the ICBM, and let it tell re-route the relevant info to the sub output.

Courtesy Dre J's solution for the Rotel 1066 on HTGuide and HTF...

When the analog bass management in the 950 is OFF, are the LCRLsRs full range? If they are not, I would be interested in what you do, as I would be doing my bass management externally also.

I'm sure there may be some negative effects on the warranty. But it's either this or start looking all over again for a pre/pro in my price range.

The LCRLsRS pass through is a full range, analog, clean as hell pass through when the bass management switch is in the off position. My problem is only with the Sub output of the 6channel pass thru. This output gets bass information from the other five channels added to it regardless of the analog bass management switch position. In fact, inside the unit there are basically 6 relays that switch the signal back and forth between full range (bass management off)and hipass filtered (bass management on, but the relay for the sub output has been linked out. So the sub output is always exactly the same signal regardless of bass management switch position.

This is an unacceptable combination if you want to use an external bass management solution on the 950 output AND you have a DVD-A or SACD Multichannel format player using the 6 channel pass through. If you have the above combination, "doublebass" is your problem too. I personally won't even put the thing back in my rack until I find a solution.

I made the same argument last winter, but, nevertheless, my 950 just arrived a few minutes ago. I'll just have to use analog 80hz and stop thinking about it.

Fortunately, I won't be using the pass-thru that way. I have an analog 60Hz crossover in my main left/right feeds, to direct sub-bass to my four subwoofers, so I can get stereo sub-bass when playing CDs etc. I set all but the front left/right speakers to 'small', with the 950 set to 'no subwoofer'. I REALLY agree though that the 950s set up is brain dead in not passing an unaltered .1 signal when the crossover is off. Warranty or not, if you don't have any failures in the 950 in the first weeks or so of operation, then the chances are very good it will continue to work forever. I would go in and rip that crossover out and fling it ! (assuming of course that your know what you're doing, electronically (-:

What totally surprises me is the fact that the Outlaws won't even agree that this is a brain-damaged setup. Thankfully, it doesn't affect me (yet) because I haven't made the jump to DVD-A yet. But I have a setup that could benefit quite a bit from the ICBM's added BM flexibility.

This seems all the more odd coming from the very company that revolutionized the whole BM discussion with the excellent ICBM product.

I sure hope that their next pre/pro fixes this problem.

If you manage to find a workable workaround (read: I can do it even though I don't know how to use a soldering iron) I'd love to see it. I'd be happy even if it completely disabled the analog BM; i.e. the rear-panel switch doesn't do anything in either position. That would make me free to add an ICBM. And, ironically, to give the Outlaws more of my money.

Maybe we can make them a deal: they let us keep the factory warranty; in exchange, we do this "NFA modification" ourselves and give them another $250 for an ICBM.

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Matthew J. Hill
matt@idsi.net

if you use the icbm with x-overs set to 40, speakers set to "large", toggle switch set to "off" and adjust your subwoofer x-over to blend with the speakers...someone please tell me how you get double bass. the only way there will be double bass is if the engineer intended it to be there anyway.

would someone who has the time, inclination and equipment please use the above scenario and graph this "double bass" while playing an sacd or a dvd-a disc? same passage of the same disc on the same system, first graph through the 950 and second graph through whatever prepro is supposed to be different as to "bass management".

the icbm is no more than a multi-channel active high-pass filter with subwoofer level adjustment.

to "manage" bass, you need subsonic filters, time delay, parametric eq, filter damping adjustment, room acoustic treatment, polarity switch, phase adjustment, variably adjustable sub x-over and quality monitoring equipment to make the adjustments.

not to mention that, for playback to be accurate for multichannel scad/dvd-a, you need 5 matched full range speakers, set equi-distant from your ears dead on the arc of a circle.

if you have all these requirements, then you probably didn't wait for a 950 prepro to round out your system, but i do, and i did, and i am thrilled with the 950. mostly, because of it's outstanding bass sound.

i would certainly see that all the above requirements are met for sacd/dvd-a multi-channel playback before i pitched my 950 because of double bass is all i am saying in the end.

First I'd like to say that I love my 950...BUT

Simply stated:

Bass management should either be ON or OFF,
not some in between state which is the reality of the 950s' bass management.

If it is on, then no exteral bass management device can be used

If it is off, then an external solution must be provided.

That having been said, if you have a 950 and want to use an external bass management solution, you will be unable to properly reproduce the original recording.

I'm an electronics field engineer for Solid State Logic Inc. and am professionally involved in the configuration and setup of most high end studios capable of 5.1 for DVD-A and SACD on the East coast. I know exactly how bass management works in the very studios that create these mixes.

Back to the reason I started this. I have succesfully modified the 591 card in the 950 so that when bass management is OFF it is really OFF. It is a very simple mod, but requires not drinking any coffee for 24 hours and some extremely proficient soldering skills. In the process of doing this I discovered the original design was even more flawed than the existing one. Originally the circuit was designed so that when BM is OFF, the .1 output consisted of a full range sum of LRCLsRs and the .1. There is an after production mod that defeats the switch for the .1 output. So basically when you flip the ON/OFF switch absolutely nothing happens to the .1 channel.

This mod has given me a true, unaltered 6 channel pass thru. Unforunately, the internal (On screen) BM operates in the same way as the analog pass through. I have no idea how one would go about modding that. The negative effects of it can be greatly reduced, though by setting all the crossover points to 40 cycles. I don't mind that as it actually sounds kind of nice to have a little bump below 40HZ. Keep in mind, this is will not faithfully reproduce the original mix though.

Please, everyone keep in mind that all of this is only ever an issue if you want to use an external bass management solution, and in the end...

IF YOU ARE HAPPY WITH THE WAY YOUR SYSTEM SOUNDS, THERE NO REASON TO LISTEN TO ANYTHING I HAVE SAID HERE.

ssltech: Well? Where are the pictures and detailed instructions? Not that I'd do it... but I am curious.