A pro talks about bass management issues for surround *music* playback (1 Viewer)

[Kevin C Brown]

LS3/5a: bingo, that's the one. For kicks over the past year or so, I've had subscriptions to the 2 ch UK mags Hi Fi Choice and Hi Fi News. I am frankly surprised by how many bookshelf monitors they review where they include comparisons to this speaker. And ... there is currently more than one British manufacturer that has current models that try to emulate this little guy's sound. Thanks for the link to that site.

 

[LanceJ]

No problem.

You might also want to check out KEF's online museum of their past models:

"The Museum of KEF History"

BTW: I sent you a PM (the forum's PM system has become very inconsistant about PM notifications. Also, having to constantly readjust the "show messages from" thingy so I CAN see my PMs is a weird thing to do and has caused me to miss messages for days until I realized what was happening).

 

[LanceJ]

I've got another issue that I've been holding back, but this might require the help of a HT guru or a professional surround mixing engineer:

Say you've got a 5.1 music mix where *no* b.m. was used in its creation, so of course any bass frequencies below 80Hz from varying instruments is being sent to all the monitors (the studio version of a home system's satellites). Remember: the mixer is using full-range monitors to put this mix together and obviously he has determined the precise amount of bass that is being sent to those monitors to get the music to sound right. >>> foreshadowing section : in studio photos the monitors are almost never seen sitting in corners because full-range speakers shouldn't be in a corner in the first place.

Next...........

Now we're in Regular Joe's living room with his Average 5.1 Surround System. In the corner he has a nice sub with a 12" woofer, but is using sats with 4" drivers, so he has to use b.m. with this speaker system.

Reminder: subs usually produce the most bass sitting in or near a corner since corners act like horns for low bass, amplifying those frequencies, compared to being located along the wall somewhere, behind a couch, etc.

Now Regular Joe loads his copy of the above-mentioned surround album into his player. The b.m. splits up the signal and sends the sounds below 80Hz to the sub as designed.

We now have a speaker (i.e. the sub) reproducing signals that were originally designed to be generated by a speaker not sitting in a corner.

Question: will the levels of those bass signals from all five of those sats be at the correct level now?

I'm wondering because when I've played around with my own system and used b.m., the bass generally does become quite a bit louder, but that's understandable because of the scenario described above.......but is that the CORRECT amount of bass I should be hearing??? For example on the Beck Guero dvd-audio, the bass can become especially overbearing when I use b.m.

For those that know: to set the subwoofer's level on a system that uses b.m., do those calibration discs send a full-range signal only to the sats (& not the sub); or just the sub only?

Because if it sends signals to the sats ONLY, this should eliminate the level problem I am asking about....I think.

But if its sends info just to the subwoofer, I think there might be a level problem.

Obviously if you don't own any measuring gear, the sub can be set by ear for whatever amount of bass you wish, something that's been done for years, though I do understand the desire to make sure it's at the *best* level (the instruction manual that came with my entry-level Pioneer speakers even mentions using a test meter for their calibration). I'm a full believer in science and its related fields, but I'm also not a slave to numbers and standards in a field where there exists such huge (sonic) gray areas i.e. we're not trying to send a probe to Saturn here.

BTW: I also think this might apply to movie soundtracks but am not that familiar with movie engineer's mixing habits, but also notice *them* using large monitors quite often.

 

[Kevin C Brown]

The levels should be fine. Remember, the system has already been calibrated to the correct levels with the sub in the corner. All the reciver or pre/pro is doing, is redirecting the low freq material. No level change should be occurring.

Remember, theoretically, a sub *should* be better at reproducing lower freqs than speakers can. (Unless you have speakers that are flat to 20 Hz. Or a crap sub. ). So you might simply be hearing more bass, because that's what was there in the first place that wasn't being reproduced adequately by the mains.

Plus, there is a dynamic range issue. If the mains are having to play both low and high freq material, they will be limited in their dynamic range simply because of how much power it takes to play low freqs. But ... liberate the mains of the low freq info by sending it to a sub, and you now have more power available for the mains info.

With that being said, there is one more tidbit that most people get backwards. How exactly do you calibrate a sub? If you use Avia or most reciever or pre/pro test tones, due to the fact that the Radio Shack meter is *less* sensitive at lower freqs, if you calibrate perfectly flat, then in actuality, the sub is 2-3 dB too loud. Think about it for a second and it will make sense. So the sub *should* be calibrated to a level 2-3 dB below the speakers for the best theoretical matching level. But, a lot of people actually calibrate their subs "hot" and that just adds to the ... "problem".

 

[LanceJ]

Much ado about nothing, eh?

I wasn't sure if I thinking too much or if it was just too much coffee.

Check out what Abbey Road studios uses for some of their mastering: REALLY full-range monitors