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  #1  
Old 04-17-2010, 03:25 AM
cherryfields cherryfields is offline
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Default Bass management question

Hi
I'm thinking about adding a sub to my 5.0 Adam A7 monitor system to get a better picture about what's going on in the low end area.

How do you connect your subs?

Are you using a bass management system (hardware / software) or are you just adding the sub to the main Left/Right speakers

I do mainly sound editing / sound design but I also write and produce music when I'm in the right mode.

Any suggestions?

My room is pretty small ca 14 m2

Cheers / Mike
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  #2  
Old 04-17-2010, 06:07 AM
BradLyons BradLyons is offline
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Default Re: Bass management question

About 12-years or so ago, Event Electronics released a set of monitors that never caught on....in fact, they died a miserable death. However these were some of the best studio monitors ever built for the home studio. These monitors were called the TRIA's and consisted of (2) smaller speakers and a single subwoofer. Not that the monitors themselves were amazing because they weren't, but the combination of this speaker helped a home studio get a more accurate mix due to the issues that plague ALL typical home studios with standing waves and the loss of bass frequency. The reason these speakers failed is that the manufacturer relied on the retailer channel to educate the end-users which never really works. You see, everyone wants the biggest, baddest looking speakers they can buy that has the most bass kicking out they can hear. BUT, this isn't really a good way to buy monitors :) The reason that the TRIA's worked, well I'll get into that below.

BEFORE you decide to purchase a subwoofer, let's address the room first. Starting with a room that is properly built in terms of the angles of the walls and the makeup internally will have major impacts on the frequency, accuracy, and bass response of a room. Unfortunately for a home studio, this isn't exactly easily accomplished. You can pretty much guarantee the wall construction is a standard 2x4 stud spaced 16"-24" across with NO support in between them. Often you might have standard insulation at best, but often nothing in the interior walls. This creates for a hollow source that resonates at lower frequencies. By placing wedges in between the studs at various intervals known as "stingers" or "stringers" (I forget! LOL) can do WONDERS for your room. This is ideal in construction, but if you feel like ripping out your drywall to do so---it is worth the effort. Likewise stuffing the interiors with mineral fiber will make incredible results!! Often placing foam in the room makes it sound like the problems are fixed, but that is only on the high frequencies because that is what you can actually audibly hear, but the low frequencies will still build up and cause headaches. By placing THICK bass traps whether that be in foam or fabric wrapped mineral fiber in your corners, on the rear wall, and even on the front wall in front of you will drastically help assist these problems, although it won't exactly eliminate them.

I say all this because I do believe subwoofers are an advantage to a home studio due to acoustics issues of the rooms themselves. They actually allow you to hear the bass in the mix position rather than lose them in a standing wave. In short, a standing wave is where the wave has no where to go. Bass frequencies are loooong waveforms and move much slower. They can't escape a corner or back wall before they get hit with the next wave unlike high frequencies which are short, fast wavelengths. This is why placing foam in a room immediately eliminates "slap echo" but what you can't hear is what is causing the problems. These bass frequencies are tricky, but to those of us with experience know exactly how to fix them.....and that's why you're hear, asking for a subwoofer :) SO BEFORE YOU GET A SUB.... have you treated your room? I'm not asking about re-construction, but seriously treated the room for bass frequency? Those A7's have some good bottom-end, but I'm willing to speculate that your room isn't allowing those monitors to work. Please advise as to how the room is treated and the exact dimensions (I'm not sure what you mean by 14ca2m)......
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  #3  
Old 04-18-2010, 04:09 AM
cherryfields cherryfields is offline
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Default Re: Bass management question

Hi Brad
Thanx a lot for your very informative information, you're absolutely right about the room situation. My room is 3,90 x 3,35 metres and 2,70 metres height and I have put some Auralex pieces on the walls I also have one of the 3,35 walls covered with a think backdrop 30 centimeters from the wall.

Right now I'm having 2 pretty nasty frequencies going on in the low range 104 Hz and 141 Hz and if I can't manage to sort this out somehow then I will get another edit room. In fact I'm having an engineer looking at the problem right now.

My question regarding the bass management was more like how do you all have this sorted out.
I know a lot of pretty busy studios having 5.0 speaker system with a sub simply hooked up on the main Left/Right mix which seems a bit strange in my opinion.

Thanx again for the info and guess I should check out this forum regarding my room
http://www.johnlsayers.com/phpBB2/index.php
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  #4  
Old 04-18-2010, 06:13 AM
BradLyons BradLyons is offline
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Default Re: Bass management question

The room isn't big, but it's not tiny. My room is 12ft deep by 10ft wide, give or take. BUT the way I designed the walls, the construction, and how everything is positioned was in great detail. Room treatment can only go so-far, because what's in the walls is more important (to the actual acoustics response of the room modes) than what's on the wall. For example, here's my drawing of the layout:

http://www.theaudioprofessional.com/...20design_1.jpg

In my room I have JBL LSR6328's which are thumping monitors! I do a lot of bass-heavy mixes. I'm guessing your speakers are right up against the front wall? Sit at the very back wall and let me know how different it sounds v/s sitting in the mix position. If you hear a ton more bass, then we know what the solution is......
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  #5  
Old 04-18-2010, 06:37 AM
Postman Postman is offline
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Default Re: Bass management question

Quote:
Originally Posted by cherryfields View Post
My question regarding the bass management was more like how do you all have this sorted out.
I know a lot of pretty busy studios having 5.0 speaker system with a sub simply hooked up on the main Left/Right mix which seems a bit strange in my opinion.

This long sticky
at the top of this forum contains all of this information. You have to weed through the extra nonsense, but its all there. Also, check out the links in Marti's first post. Having said that...

Many "audiophiles" just attach a sub that gets signal from left+right, or all channels, and tune the speaker's gain and position to a personal preference. They are adding sub woofer output to their main speakers. What results is anyone's guess. This might result in a pleasant sounding system, but more than likely it is not a linear system.

Some music systems favor two subs, on left and right. That was fine when there were only two playback channels, assuming the sub+main is linear. You're just extending the bass response of the left and right speakers. I suppose you could have 5 or 7 subs now, but that seems kind of impractical or impossible.

For bass redirection, the goals is that speakers+sub setup should sound the same as full range speakers. The sub only provides bass playback that the main speakers are unable to reproduce. The sub can be positioned within the room to leverage speaker loading at various frequencies (relative to the listening position), and maybe provide a flatter playback at the listening position. Moving the sub away from the main speaker, though, presents other response problems around the bass redirection frequency. The room is a huge factor in bass response, too, so moving the sub speaker around can help even out room-induced problems for the listening position. You MUST use a realtime sound analyzer during system setup to keep response linearity. Most small rooms, like yours, cannot provide reasonably flat response anywhere. The trick is to control and balance the variables for best compromise at a listening/mixing position. A couple of parametric equalizers, to tackle bad resonances, may be helpful. Room treatments like bass traps, are BY FAR the best investments.

Having a single sub works well here, since all low bass emanates from a single point in the room. Only one set of compromises need be made. (Five fullrange speakers in a small room provide five different bass challenges.)

There are three approaches to bass redirection in pro setups. In consumer systems, there are lots of variations.

1. NONE. Each speaker is full range. (Surrounds are not required to have full bass extension, but it is better if they do.) The sub speaker is used only for LFE (the "point one" channel), it gives 10db of gain, and its upper frequency is limited to approx 120hz. This is Dolby's recommended practice for film theater work because this is how film theaters are set up for Dolby playbacks.

2. Bass redirection of 80hz and below to the subwoofer, and the subwoofer boosts the level 10db. This is the DTS approach. The main speakers do not need to have full bass extension since they are never required to play sound much below 80hz. This has the unfortunate consequence of emphasizing any rumbles and bumps in the main channels by 10db. A pro mix shouldn't have extraneous rumbles and bumps, they will have been heard and removed during editing and mixdown. Since the mixdown and subsequent playbacks are heard through systems adjusted the same way, all is good. (If anyone knows more current information on the DTS approach, please correct me! I never use this one.)

3. Bass redirection from only the surround speakers, or optionally from all main speakers, into the subwoofer. The sub speaker level is adjusted to provide "flat" response for the main channels. Then, the LFE channel into the sub speaker is adjusted to provide exactly 10db of boost. Note that only the LFE channel's sound is played 10db hotter. Main channels should sound the same whether played through a full range speaker or through the bass-redirected system. The redirection frequency can be anything, perhaps 40hz, 80hz, 120hz, or whatever is best for total system+room performance, but the LFE channel should provide an upper frequency cutoff (120hz is typical).

There are other bass management scenarios, for instance there is one that does like the DTS system but alters the gains so a main channel's bass is reduced by 5 or 6 db when redirected into the sub woofer (compared to the LFE). The reasoning behind such an approach is incomprehensible to me.

My fingers are tired and I've only scratched the surface.
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  #6  
Old 04-18-2010, 08:11 AM
cherryfields cherryfields is offline
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Default Re: Bass management question

Hi again
Here's a rough drawing of my room incl some gear
http://files.me.com/mikael.korner/m54ygm

Thanx Mr Postman regarding the bass management and setup question, you're absolutely right it's actually all in there in the room calibration thread that I have been reading so many times looking for directions regarding dia norm etc. Don't know why I never vent through the thread looking for info about the physical setup (sorry for my laziness)

This sounds like the way to go (in my head) when I have sorted out the room situation

3. Bass redirection from only the surround speakers, or optionally from all main speakers, into the subwoofer. The sub speaker level is adjusted to provide "flat" response for the main channels. Then, the LFE channel into the sub speaker is adjusted to provide exactly 10db of boost. Note that only the LFE channel's sound is played 10db hotter. Main channels should sound the same whether played through a full range speaker or through the bass-redirected system. The redirection frequency can be anything, perhaps 40hz, 80hz, 120hz, or whatever is best for total system+room performance, but the LFE channel should provide an upper frequency cutoff (120hz is typical).

cheers / Mike

PS! I used a very nice system called RT-Capture 2 when I tried to calibrate my room, I use it a lot in live mixing situations
http://www.wavecapture.com/
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  #7  
Old 04-18-2010, 09:05 AM
Postman Postman is offline
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Default Re: Bass management question

Okay, placement within the room is yet another issue. Yours is not quite to either prevailing method. There are Dolby and ATSC documents that specifically go into placement.

First, are the smaller boxes your A7's? What are the two larger boxes? Where is your video screen?

For all small rooms, the speakers should be equidistant from listening position. All speakers should be the same distance from your ears and on the same plane. In practice, the surrounds may be a different height than the fronts, all in an arc across the front and back, all angled somewhat toward the center listening position. It is generally recommended that the left and right speakers be 30 degrees away from center, and if only two surround speakers they are at 120 degrees away from center (behind you). Obviously, this is intended for one and only one optimum listening position. You can compensate for speakers being closer than others using delays, but equidistance is what is recommended.

Dolby’s practice in large theaters is different, since the listening area is very large. The front speakers are in a straight line behind the screen, since anything else is impractical. There is no chance that all listeners can be equidistant from the speakers, so no attempt is made to accomplish that. The surrounds are diffuse due to many speakers around the room, above head level and angled down. The surround is no longer point sourced but more “omnipresent”. There may be a delay applied to the surround speakers to give a rough compensation for the close distance of surrounds to listeners.

Dolby also provides guidelines for screen size vs. rooms size, and speaker placement behind the screen. They end up putting you in the same rough 30 degrees off center placements. They also prevent listeners being too close to any front speakers.

In small rooms, realize that if the front speakers are not soffit mounted (speaker face flush with the wall), you will have bass frequency irregularities, comb filtering. These problems add to the other room issues. If the speakers are backed up against the wall you'll get mostly increased bass with one or two irregularities, and when you get several feet away the whole comb filter effect becomes less important (and the bass boost from wall/corner placement is correspondingly decreased). Between those two extremes you can have the most trouble. It comes from bass reflections off the wall combining with direct bass, thus reinforced bass with comb filter effect. It helps to put THICK absorption behind the speakers. That will tighten up the imaging and hopefully decrease some of the bass reflection as well. Keyword there is THICK. Thin absorption on the wall doesn’t do anything to bass. You’ll find commercial products on stands that you can place around the speakers that do the same thing.

The more absorption you have in corners, the better off you’ll be. They are one form of bass trap. Another concern in small rooms is the balance of total absorption vs. reverb decay. Too much absorption above bass frequencies makes the room unrealistically dead. This is where diffusion comes in, but this is getting too much for one post.

Brad’s points about construction are all on the mark (absorption in the wall cavity and randomized stringers to reduce single frequency resonances). Materials are a huge factor too, they help determine what/how much is reflected back into the room, or absorbed, or passed along to the outside.

Of course, most of us have no control over how a room was built, so measurements and intelligent treatments are in your plans.
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Old 04-18-2010, 10:11 AM
cherryfields cherryfields is offline
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Default Re: Bass management question

Thanx again
The small boxes are A7 and the two bigger ones are my NS10m. All seven speakers are on speaker stands at the same height.

I use two 24" Screens just under the speakers.

The Ls and Rs speakers are a bit to far compared to the others but someone placed the entrance so that I constantly ran into the speaker stand when it was placed a bit more suitable... Like you mentioned "most of us have no control over how a room was built" If it wasn't for my lovely wife I would have turned my living room into a nice edit room but I guess that would cost me way to much money to cover the costs for making that deal (huh)

My 3 room studio suite (there's a few more rooms plus kitchen and wc) is definitely not the best option for this kind of work but it's in the same building as I work as a full-time soundengineer so there's some other benefits but I am really looking for something more suitable

Thanx for all the advices

cheers / Mike

PS! I will make some serious adjustment to the setup and make some new measurements this upcoming week so hopefully there will be some improvements done
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Old 04-18-2010, 10:47 AM
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Bob Olhsson Bob Olhsson is offline
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Default Re: Bass management question

I'm not a popular guy with folks who sell subs. To be blunt, the low-end doesn't translate well at all to other listening environments unless we are talking strictly about the sub doing LFE with nothing else being sent to it. The only way I could ever get them to translate was using a separate one located right next to the main driver turning it into a bi-amplified full range system. There's a huge difference between fun recreational listening and a mixing tool.

Bass management is magical thinking from the daze of early stereo in the late '50s where people didn't want two large speakers in their living rooms. The problem is trivial to demonstrate by adding a sub to a full range system and then switching between full range stereo or surround and bass managed. The audible difference is night and day.
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Old 04-18-2010, 12:04 PM
cherryfields cherryfields is offline
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Default Re: Bass management question

Hi Bob
Thank a lot for your input, so if I manage to sort out the room problem alt move to a better sounding room I should get my hands on 5 pieces of nice sounding fullrange speakers plus a separate sub for the Lfe (right)

Pretty obvious I guess and in my case I figure I should start right away with the room situation before even thinking about buying a sub.

cheers / Mike

PS! I really like your stuff at the Womb (great forum)
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