[cameraman]

I have an idle 10B SUB crossover I am considering using to add bass to my center channel. I used it years ago in a 2.1 system where I summed the L/R channel and set the high-pass at 80 Hz with a 6-db slope and the low pass at 80 with an 18-db slope.

I also have available amp channels to reconfigure and assign from either a 4BST, 6BSST or 7BST. I have all the needed equipment so there is no cost involved; I just want confirmation I have a reasonable plan that can improve my system sound.

I would use just one 10B SUB channel in stereo mode and start by trying 200 Hz high/low pass. Should I also start with the same 6-db high-pass slope and 18-db low pass slope? I understand this would minimize phase issues.

The Center Channel would then handle 200 Hz and up, the sub-woofer/bass bin would handle center channel content 200 Hz and below. I can then re-run Audyssey and see where the AV processor puts the new crossover. I would probably still change the Center speaker size to small.
 
I plan on using a 10" AuraSound NS10-513-4A in a 1 cubic foot sealed enclosure or a 9" ScanSpeak Revelator 23W/4557T00 with a 9" 23W/0-00-02 Passive Radiator in a 1 cubic foot enclosure. I can physically place them near the CC. Either of them can comfortably handle 200 Hz or even higher if needed.

Background of why I am looking into this:

I ran Audyssey MultEQ XT32 again with my AV Processor after adding a new 18” sub-woofer to my system and noticed Audyssey set the center channel crossover to 150 Hz.

I am currently just running a single sub-woofer and it is installed in the front of the room to the right of the center channel and while the dialog sounds fine now I can hear CC content coming from the sub-woofer. I am concerned since I plan to add additional sub-woofers farther from the center channel, the content below 150 Hz will throw off the sound stage.

I could still set the AV Processors’ center speaker size to small, sending 80 Hz and below to SUB 1/LFE. This would keep the center dialog, especially male voices, tied to the center channel.

I run an Infinity Compositions Prelude system. The Compositions Prelude Center Channel Model P-CC specifications:
Frequency Range: 80 -20,000 Hz, 120 – 20,000 Hx +/- 2 dB (-10 dB @ 80 Hz)

[ragg987]

If I understand this correctly, the issue you are trying to solve is that the centre channel sounds below 150Hz are currently being sent to an off-centre sub and hence you can pick up some of the audio as off-centre.

Have you tested shifting the centre crossover to a lower frequency? If you can get it to work at 80-100Hz (bearing in mind the capability of your centre speaker) this should reduce the off-centre localisation by a substantial amount, perhaps enough that you will no longer hear it (this is the standard multi-channel sub wisdom). I have no experience of Audyssey and I prefer to tune these aspects manually using REW and my ears.

If above is not satisfactory, then you can either replacing your centre speaker or trying to add a sub - both with the same goal, to extend the frequency response of the centre.

Adding a centre sub to extend the response is going to be hard to integrate properly - you need to factor in the cross-over frequency and phasing, plus the impact of the low- and high-pass slopes.

[cameraman]

Thanks for the response.

The Center Channel may just have a limitation as the specs suggest. Why do you think it is difficult to integrate a bass bin to the center speaker? I used the 10B Sub in a 2.1 channel arrangement and it worked great.  I am not interested in adding a center that doesn’t match my front R/L. This room is for movies almost exclusively.

While I would prefer the 10B SUB had a 150 Hz option, wouldn’t the same 6-db high-pass slope and 18-db low pass slope I used before at 80 Hz work equally well at 200 Hz? I should be able to adjust the levels and the 6 vs 18 slope settings should address potential phase issues.

[ragg987]

I can't comment on the 10B, have no experience.

Difficulty in integrating stems from having to control the variables. The 10B can probably control them all (not sure if it can do phase), but how do you evaluate if you have dialled in a good setting? Reason I believe it will be difficult is that this is what speakers designers do when creating speaker cross-overs, and they have lots of equipment to measure / test and analyse.

Experimentation may be the key, so do try and let your ears decide. I would be inclined to try lowering the cross-over on centre first. Spec say -10dB @ 80Hz, so perhaps 90Hz or 100Hz would be a sensible level to crossover?

[brucek]

While I would prefer the 10B SUB had a 150 Hz option, wouldn’t the same 6-db high-pass slope and 18-db low pass slope I used before at 80 Hz work equally well at 200 Hz? I should be able to adjust the levels and the 6 vs 18 slope settings should address potential phase issues.

Yes, I suspect the 6 vs 18 slope settings would address potential phase issues, but I don't feel that's the issue.

Bass frequencies (20Hz-80Hz) are the most problematic as a result of room resonances that are set up between parallel surfaces (walls, ceilings, floors). These axial modes create standing waves that cause cancellations or peaks at various locations in the room, so careful subwoofer speaker placement is important at these frequencies. The subwoofer can be located at the best spot (without the worry of directionality or soundfield) to reduce peaks or valleys at the listening position for the best low frequency sound. Obviously this isn't possible if you've assigned those low end frequencies to your center channel.

The center channel requires directionality and is placed in the center between the mains. It's a decent idea if you want to bass manage that signal and send the centers' low frequencies to a subwoofer, freeing the center to do its job, but since frequencies above 80Hz are easily localized, then your idea of directing up to 150Hz to a sub isn't a great way to go.

The subwoofer is designed for the under 80Hz spectrum and can be placed anywhere in the room since frequencies below 80Hz aren't localizable, it allows a lot of flexibility of location for the sub to minimize room modes. 

brucek

[cameraman]

I seem to be having trouble explaining myself.

I will have at least two and possibly three true sub-woofers to handle LFE and content below 80 Hz.

I will have an additional mid-bass woofer/sub-woofer associated with the CC and exclusively to handle center channel content between 80 and 200 Hz with the center channel handling everything above 200 Hz and the true sub-woofers handling everything below 80 Hz. This mid-bass sub-woofer can be placed very close to the center channel.

I would then have, essentially, a 4-way center channel and either of my available 9 or 10 inch drivers can handle up to 500 Hz. My matching L/R mains are already 4-way with built in 12" subs.

Audyssey  may not be embraced on this forum but It does wonders in my room and Audyssey has flexibility in raising crossover points but recommends against lowering them.

Thank you.