Bass Management

[jimsiff]

I'm trying to figure out the best way to deal with bass management for my system. I think I'm stuck using an 80 hz crossover for DD/DTS since my Pioneer 54tx jumps from 50 to 80 hz, and the 340s don't go down to 50 hz.

I just received my Pioneer dv-563a uniplayer. My receiver doesn't do any processing for the analog 5.1 input, so I'm looking at an Outlaw ICBM. It has the ability to crossover at 60 hz. I wonder if it would be better to use 60 hz so bass is less localized. I would guess the amps in my receiver would be taxed more crossed at 60 hz than if I used 80 hz.

Would a 60 hz crossover be worth it? Have any of you played with different crossover frequencies? Have you observed noticable improvements in bass with a lower crossover? Did you notice a definite lack of amplifier headroom crossed at 50/60 vs. 80?

I'm not ready to consider outboard amps at this stage, especially if I get 340s for the rear instead of 170s and get an ICBM. In any case, I guess I'd just need to play around.

Opinions and personal experience welcome...

[Mag_Neato]

I have 170's and tried different crossovers with my Outlaw 1050.

80 and 100hz were virtually identical, and 60hz left a noticable hole in the frequency response. I have it at 80hz with no problems.

The crossover is not a brickwall.........response rolls off from that point. Linkwitz-Riley crossovers have a filter slope of 24db/octave.....meaning the spl at 20hz is 24db less than at 40hz(an octave above a given frequency is double that frequency......someone correct me if I'm wrong).

I'd leave it at 80hz.

[Kpt_Krunch]

Jim - I have the ICBM for bass managment and I use it at 80hz cross over for all the speakers. My receiver (an H/K 520) only does bass management for the digital stream (DD and DTS), not for analog multichannel. The Pio player when set to small does the following:

DVD-A - X-over at 200hz
SACD - X-over at 120hz

When set to large - the Pio sends the full frequency range sans the .1 channel info to each speaker.

When I purchased the ICBM and set it up with my original setup - the improvement in sound was dramatic to say the least. When I got my Ascends, the 340's and 170's, I crossed them over at 80 hz. The reason why is in the ICBM manual it states that for optimum peformance you should check the specs of your speakers to determine how low they will go at -3db's (if listed). Whatever that number is, go to the next highest setting on the Outlaw ICBM. A buffer of 20 hz should be used. So, in other words, if you speakers go to 35 hz, then you would set the cross over at 60 hz. The 340's go down to 50 hz, and the 170's to 63 hz (typical in-room response) so I just decided to go 80 across the board. I have experimented and switched the fronts (all 340's) to 60 hz, but I didn't notice any improvement.

As Mag_Neato already mentioned, this cutoff is not a brick wall, there is a rolloff at that point that blends in with your sub. This is why Outlaw Recommends going at least 20hz over the rating of the speakers for the cutoff - so you are guaranteed to hear everything. Also, from what I have read, the less lower frequencies the speakers have to produce, the better they will work for you. The 170's should probably be set at 100hz as there is only a 17hz difference, but I feel it is close enough to 20hz to leave it at 80, and it sounds great to me

Hope this helps you out.

[jimsiff]

That makes sense... is the crossover slope for the ICBM 24 db/octave? Crossed at 80 hz, the amps in the receiver aren't working as hard, so my chances of running the receiver into clipping should be less.

[jimsiff]

Nevermind... I should just RTFM! It looks like they use 2nd order 12 db/octave crossovers for all channels except the sub channel which can use 2nd or 6th order. Given that, I wouldn't want to go lower than 80 hz for even the 340.

Somebody correct me if I'm wrong, but if I used 60, the output is only 4 db down at 50 hz. With 80, it's 9 db down at 50.

[GaryB]

Nevermind... I should just RTFM! It looks like they use 2nd order 12 db/octave crossovers for all channels except the sub channel which can use 2nd or 6th order. Given that, I wouldn't want to go lower than 80 hz for even the 340.

Somebody correct me if I'm wrong, but if I used 60, the output is only 4 db down at 50 hz. With 80, it's 9 db down at 50.

Your estimates are probably pretty close. Don't forget - most people do - that the output is already -3 dB at the crossover point for Butterworth filters (likely what the ICBM uses) and -6 dB at the crossover point for Linkwitz-Riley filters (the THX standard, and used by many AVRs).

I agree with Kpt_Krunch - an 80 Hz crossover is likely the optimal choice for a mixed CMT-340/CBM-170 system.

[jimsiff]

Your estimates are probably pretty close. Don't forget - most people do - that the output is already -3 dB at the crossover point for Butterworth filters (likely what the ICBM uses) and -6 dB at the crossover point for Linkwitz-Riley filters (the THX standard, and used by many AVRs).

I agree with Kpt_Krunch - an 80 Hz crossover is likely the optimal choice for a mixed CMT-340/CBM-170 system.

I haven't purchased my surrounds yet, even though my sig says I have 170s. I'm debating going with 340s for the surrounds. I know it's probably overkill, but what the hey. Even still, I think 80 hz is probably the best.

So Butterworth 2nd order filters are -3 dB at the crossover point? I guess that makes sense since the crossover blends the output of the sub and satellites at the crossover frequency. I'm going to dive in and google crossovers so I can get a better understanding. I've got the basics, but a deeper understanding can only help.

[Nicholas Mosher]

My pre/pro has a switch on the back to crossover my 170s in analog bypass. 80Hz or nuthin . I'm curious how 60Hz would sound with the 170s though...

[curtis]

I don't think the ICBM can adjust for distance settings, right?

[Nicholas Mosher]

I don't believe so.
Neither does our 2900's with SACD's. Oddly enough it does for DVD-A though...