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After reading Geoff's excellent walk through of the bass management system of modern BVs, I have been experimenting with different settings. My system is a BV11 with BL8000 as fronts and a BL14 (2.1) as sub/surrounds.
Does anyone have thoughts / experience with the pros and cons of changing the crossover frequency from the default 120hz?
I seem to remember that the THX standard is 80hz and at least the BL8000 should be able to handle frequencies down to 70-80hz fine. However, I am not so sure about the BL14 satellites, which might explain why the default is 120hz.
i have a 2.1 speak group with the BL8000s and the BL14 sub active for music, would the optimal crossover frequency be lower for this since the BL14 satellites are out of the picture?
Any thoughts would be much appreciated.
Moses
PS. Geoff's walk-through can be found here
Hi,
I'll make this answer the subject of my next blog posting!
However, when I did the original set of bass management tables for the first Video Engine release (the BeoPlay V1) I found that the optimal crossover for almost all combinations of BeoLab loudspeakers was higher than 120 Hz - if you're just looking at the measurements, that is... There were some specific combinations (but not many...) that were lower.
However, if you put your mass management crossover too high in frequency, then the re-distribution of the low frequencies to a different loudspeaker becomes audible - the higher the frequency, the easier it is to localise.
So, I made the decision to set the default to 120 Hz based on the Dolby recommendations for professional re-recording engineers who are mixing in 5.1. However, we also ensured that the value was editable by the end user - from 20 Hz to 300 Hz - just in case.
Unfortunately, I can't comment directly on the combination of BL 8000 and BL 14 without looking at the numbers. I'll dig around and find this out. However, I'll warn you now that this number is not as simple to arrive at as you may think - since it is highly dependent on how loudly you're playing. (Remember that ABL changes the low-frequency cutoff of all of our loudspeakers except for the BL5.)
All of that being said - I would highly recommend that you play with this frequency to see if you find something that you prefer over the default setting. Keep in mind that the 8000's are ported loudspeakers, and the lower in frequency the bass management crossover goes, the "weirder" (to use a technical term...) the phase response goes. Therefore, you might need to play with either the Time Alignment or the Allpass Frequency in the Subwoofer menu to get things to line up nicely... However, I guess that, since you have a BL14 2.1, you're probably not using the Subwoofer speaker role for it - so these controls won't have any effect.
More info to come - either here or on my blog page.
Cheers
-geoff
Thanks a lot for the detailed reply, Geoff. Much appreciated.
I will experiment a bit more and see which crossover frequency I think sounds best in my setup.
And to clarify, I am indeed using the "Subwoofer" speaker role for the BL14 sub in the different speaker groups (2.1, 3.1 and 5.1) that I have configured to include it.
Cheers,
PS. Looking forward to your next blog post!
mcmartiny:And to clarify, I am indeed using the "Subwoofer" speaker role for the BL14 sub in the different speaker groups (2.1, 3.1 and 5.1) that I have configured to include it.
In that case, two additional configurations you should try are:
- to set your BL14 2.1 to use only 2 channels of the BV11 with the Left Surround and Right Surround speaker roles. This way the BV11 will bass manage to what it thinks is two full-range loudspeakers, and then the BL14 DSP does the bass management split between the sat's and the sub.
- to set your BL14 2.1 to use 3 channels (Ls/Rs & Subwoofer) but to set the bass management menu called Enable Filtering for the Ls and Rs speakers to "Off". This will ensure that you're not bass managing twice on those channels (once in the BV11 and once again in the BL14 DSP).
Results may vary - whatever sounds best to you is the best choice to make. However, I expect that these two options are not immediately intuitive as things-to-experiment-with.
Geoff Martin: - to set your BL14 2.1 to use 3 channels (Ls/Rs & Subwoofer) but to set the bass management menu called Enable Filtering for the Ls and Rs speakers to "Off". This will ensure that you're not bass managing twice on those channels (once in the BV11 and once again in the BL14 DSP).
Oops. Sorry. Now that I think of it, this should happen automatically when you set your Speaker Types (or Speaker Connections - depending on which BV11 SW version you have...) Please ignore this one. I would have edited this out of my previous posting, but I'm using Safari on Yosemite - which, in BeoWorld world, is like doing the NY Times crossword in pen - there's no "do over's...."
Geoff Martin:- to set your BL14 2.1 to use only 2 channels of the BV11 with the Left Surround and Right Surround speaker roles. This way the BV11 will bass manage to what it thinks is two full-range loudspeakers, and then the BL14 DSP does the bass management split between the sat's and the sub.
Thank Geoff. Interesting approach. Would that still high pass filter the output to the BL8000s (set to the front speaker roles)? Also, how does the system know that it needs to route all the bass (including the LFE channel) to the L/R surround speakers, if their speaker type is BL14 (satellite) and not BL14 sub?
Thanks
Moses Martiny: Thank Geoff. Interesting approach. Would that still high pass filter the output to the BL8000s (set to the front speaker roles)? Also, how does the system know that it needs to route all the bass (including the LFE channel) to the L/R surround speakers, if their speaker type is BL14 (satellite) and not BL14 sub?
The video engine software contains a lookup table of parameters of loudspeakers in the B&O portfolio. One of those parameters is the "Bass Capability" score of the loudspeaker. So, when you (in the Speaker Connections) menu say "BeoLab 20" and "BeoLab 2", it "knows" how loudly those two loudspeakers can play at low frequencies. Depending on the relative difference in the maximum capabilities of the two loudspeakers being compared, then a decision is made in the SW to bass manage or not. The result of this decision is shown as a table in the Technical Sound Guide.
As for the BL 14 sub / sat: since the satellite signal must go through the sub for filtering (both highpass filtering and sound design), the TV is programmed to assume that the sub is the "woofer" for the satellite. Therefore, the BL14 sat and the BL14 sub have the same bass capability. This is to ensure that the TV does not redundantly do the bass management for the BL14 automatically. So, if you set your Speaker Connections to BL14 Sat & Sub, you'll see that the Bass Management defaults to NOT bass managing the sat's, since the TV knows that's being done externally downstream.
However, this will certainly apply a HPF to the BL8000's and send its bass signal to all BL 14 inputs. These are gain reduced by the correct amount in the TV (look in the Redirection Levels) to account for the summing back to the subwoofer in the BL14.
This may sound complicated (it certainly was for me when we originally mapped out the signal flow interactions between the two devices) but I can assure you that it all works out in the end.
If you choose to edit your Bass Management so that your BL8000's bass manage to the BL14 subwoofer ONLY (at an edited Redirection Level of 0 dB), then you'll get almost exactly the same result. The only difference would be in the crossover region of the BL 14's internal bass management which may leak a very small amount to the bottom end of the satellites in the automatically-chosen configuration.
Hope this helps.
-g
Thanks for the explanation, Geoff. Didn't realise that the bass management system always assume that BL14 satellites are paired with a BL14 sub but come to think of it, it makes complete sense.
I have tried your suggestion and routed the bass through the "surround" speaker roles. It seems to produce slightly more bass and a less directional "upper" bass which is exactly what I was after when posing my original question (on lowering the crossover frequency). I don't know if this is down to the small bass "leakage" to the BL14 satellites that you describe above or to some other effect of running the signal through the BL14's DSP instead of the BV11 one.
Thanks again for your detailed explanations and input, not every day that you are able to get this kind of insights from the people behind products you love and use. Really helps make B&O something special.
PS. I just distributed your insightful blogpost on 16 vs. 24 bit recordings to a number of people at work (I am in the music industry and the early reviews / tests of Neil Young's Pono player is currently a hot topic of discussion).