ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 [3] 4   Go Down

Author Topic: aux fed subs  (Read 10584 times)

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
Re: aux fed subs
« Reply #20 on: February 03, 2014, 06:32:10 pm »

I'm debating whether or not to try aux or group fed subs with the SM80/TH 118 setup. If anyone has tried this can you please chime in with some info?
Jonathan,

The SM80 response (without any processing) drops at around 12 dB per octave below 200 Hz.

Generally, aux fed subs are used with tops that are "full range", that is full range for most instruments other than bass, kick and low keyboards.

I'd consider the SM80 /TH 118 more of a 3 way system rather than a full range/sub combo, which could be done more effectively with a top like the SH-50 that has good response down to below 100 Hz, an octave lower.
Logged

Jonathan Betts

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 512
    • http://www.facebook.com/pages/JLB-Sound-and-Production/156817657745906
Re: aux fed subs
« Reply #21 on: February 03, 2014, 07:49:59 pm »

Thanks for the response Art. Appropriate use of HPF's, depending on the music style is probably the best approach for this system?

I had a BE come through last week to use the system in a small room for a hip hop act. One SM80/TH 118. He was concerned with the way the system DSP was configured, complaining that the tops and subs would not play well together. I told him to trust me. Put some audio through the system and a smile came to his face. Drum check he was even happier. He couldn't believe the sound coming from two cabinets and one amp with minimal processing.
« Last Edit: February 03, 2014, 11:04:11 pm by Jonathan Betts »
Logged

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
Re: aux fed subs
« Reply #22 on: February 04, 2014, 01:32:15 pm »

Thanks for the response Art. Appropriate use of HPF's, depending on the music style is probably the best approach for this system?
Yes, for a 3 way system (as opposed to a full range system with subs) appropriate use of HPFs is the way to go.

The use of aux fed subs has grown more popular than it was in the 1970s because more people now set their systems up with a huge LF "haystack" of 6 dB or more, the equivalent of turning up every LF channel EQ 6 dB or more.

If you equalize the system flat in the LF, and add LF to the channels that you want extra LF on, a 3 way system will perform just fine.

I use a three way system with acoustical crossovers around 100 and 1000 Hz, and have no problems with "vocals in the subs", or any other "mud" problems, yet 40 Hz is often the strongest frequency level in the mix.
Logged

Jonathan Betts

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 512
    • http://www.facebook.com/pages/JLB-Sound-and-Production/156817657745906
Re: aux fed subs
« Reply #23 on: February 04, 2014, 02:04:45 pm »

What is the benefit of "haystacking"subs? Isn't this why we have channel eq's? I can see maybe,   for playback music but for a live situation is this really desirable?
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 19222
  • Wichita, Kansas USA
Re: aux fed subs
« Reply #24 on: February 04, 2014, 03:06:42 pm »

What is the benefit of "haystacking"subs? Isn't this why we have channel eq's? I can see maybe,   for playback music but for a live situation is this really desirable?

Not in my opinion.  I'd much rather create the sounds at the input strips than use the subwoofer level control to create the sound at the loudspeaker system.

If Robert Scovill ever repeats his Complete FOH Engineer seminar....  (ping Scovi) a participant will get a fair bit of discussion of this... but starting with a "linear response" PA (what goes in electrically is what comes out acoustically) is the way I like to present a system.  Most BEs think we need more sub until I point out the drive level is -9dB (typically) relative to the mains.  They can decide if they want to use the channel strip EQ or the sub drive, and if they don't present a problem to the system, I sit back and let them work as they see fit.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Jay Barracato

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1958
  • Solomons, MD
Re: aux fed subs
« Reply #25 on: February 04, 2014, 04:17:21 pm »

Not in my opinion.  I'd much rather create the sounds at the input strips than use the subwoofer level control to create the sound at the loudspeaker system.

If Robert Scovill ever repeats his Complete FOH Engineer seminar....  (ping Scovi) a participant will get a fair bit of discussion of this... but starting with a "linear response" PA (what goes in electrically is what comes out acoustically) is the way I like to present a system.  Most BEs think we need more sub until I point out the drive level is -9dB (typically) relative to the mains.  They can decide if they want to use the channel strip EQ or the sub drive, and if they don't present a problem to the system, I sit back and let them work as they see fit.

If there ever was a topic that demonstrated the importance of compromise in system deployment, this is it.

I come in as being in agreement with Tim. Tuning the system flat and then boosting at the channel (assuming you brought enough sub) eliminates many of the reasons people give for liking aux fed subs. Vocal mics rumbling in the subs isn't a problem when the entire mix is not artificially boosted 9-12 db in the sub range at the dsp.

Basically it comes down to: there are instruments (kick and floor tom) that I want boosted in the subs, and instruments (Bass and keyboards) that I don't want boosted in the subs. I like the bass and keyboards to be mostly flat across the crossover. I think people are so into cutting eq's that they are afraid to boost, but if the system is well tuned you should be able to do both as much as you like. Therefore, many people seem to boost the subs across the board and then cut from the channels where it is too much. On the other hand, I would prefer the rig to be flatter and I can boost a couple channels as needed.

With a well designed system, this is probably a wash as to which is better. However, my experience is all too often aux fed subs are offered as an excuse for NO DESIGN. In other words,  the system tech didn't really put any thought into how the subs and mains combined. In all the rooms I have been through this seemed to be more of a problem in the medium sized rooms (say 300-700 capacity).

If the room was small, with a SOS system plus subs or a 1 over 1 stack, the distances were short enough that any crossover problems were probably minor, especially compared to room mode effects. Therefore, it was not as noticeable. In larger rooms, either the system tech got the design right or the coverage was so uneven, I basically had to pick one reference point and mix for that point. It was in the medium sized rooms (probably a small show tech/company expanding into bigger places), that I saw the greatest variance and misapplication of aux feed subs, including having no crossover at all. (That is more common than one might think.) I also think that many of those techs did not realize that the poor crossover design could affect the sound well above where that crossover was. It was not uncommon to find timing based buildups or pits anywhere from 125-250 hz depending on the slope of the crossover.

So at this point, as someone who mixes quite a bit on other peoples systems, I don't really care whether the subs are on an aux or not; I care about how the subs interact with each other and the mains.

For the record, I find myself cutting the lows in a lot of modern dance music when played through a full range system. The combination of the boost in the recording and then the boost in the system is just too much for me.

And if I didn't convince anyone away from aux fed subs, let me say, outdoors on a windy day, it is really nice to have the subs on an aux. So it is a compromise, use it when it gives yo a benefit.
Logged
Jay Barracato

Jim McKeveny

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1043
Re: aux fed subs
« Reply #26 on: February 04, 2014, 04:24:11 pm »

The haystack tuning isn't that prevalent anymore. (Thank the stars). However, the definition of "sub" isn't particularly locked down.

Bottom octave: 20hz-40hz? This was my first exposure to the concept. Fulton J-Modular, Infinity Servo-Static, Dahlquist. (This neatly coincides with the introduction of "super" tweeters, which handled the top octave of 10khz - 20khz).

The sub-mission creeped (crept?) across a broader range, despite obvious IMD issues at all power levels.

Define  & agree on what are "sub" frequencies (as determined by acousticians, not marketers), and then we can move forward on "best practices" for mixing...





« Last Edit: February 04, 2014, 04:30:05 pm by Jim McKeveny »
Logged

Luke Geis

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1515
    • Owner of Endever Music Production's
Re: aux fed subs
« Reply #27 on: February 04, 2014, 08:01:32 pm »

I completely agree with the flat system, what goes in comes out idealism. I prefer to tune the system as flat as possible too. However I am not a fan of boosting frequencies more than 3db or so. I tend to believe that if the frequency gain wasn't there to begin with, then artificially adding it ( via an active EQ filter ) will only introduce phase and distortion artifacts, albeit minimal or marginally existent? I equivocate it to photochopping....... Yes you can make the picture look better and perhaps more natural, but it's still not the original and it must not have been right to begin with. Reducing gain from the EQ filters has reduced artifacts in contrast to adding gain. Another thing to point out is that it is generally not a good idea to increase gain at an instruments fundamental frequency. Increasing 80hz to add more punch to a kick drum just tends to make it more muddy and thuddier. It also detracts from the bass guitar who's fundamental falls right there as well ( 82hz to be precise ). Decreasing gain at 80hz on the kick can make the bass stand out, or visa versa ( reducing bass guitar at 80hz can help the kick punch through ). Increasing gain at the higher harmonic frequencies can add something that can be beneficial to the mix. It can add clarity and presence that otherwise didn't exist before. But it's a slippery slope. I think many people are used to PA's that have diminished top end extension as a result of the environment and or sub par equipment and tuning. So adding a lot of high end is the means to that end. I find when the system is well tuned and flat out to about 16K and higher, I use little to no EQ and find reducing it helps bring that sweet top end into play. In most program material nothing exists beyond 16K anyway, so I tend to not worry about anything after that. But I still want to be as flat as I can be from about 40hz-20hz.

I am finding more and more these days that kick is getting heavier in the 50hz area with lots of attack ( on recordings ), but typically has a fundamental frequency of about 40hz.. A 5 string bass has a fundamental frequency of about 30hz and now with extended range guitars being more prevalent, a guitar with a low f# is reaching down to the 46hz area. I own an 8 string guitar and let me tell you that you don't need a bass guitarist with the thing........ That being said, sub systems playing music with a full 88 key piano may want to be flat down to 30hz. The low A on such a piano is 27hz! I would define a sub system to be one in which can extend down to 30hz within 3db of the rest of it's range. Is this common? No.... Is it possible? Yes..... Is it practical? Probably not most of the time. A typical rock band with no keys probably only needs a system that can get from 40hz up to 16khz. A progressive rock band with keys, and all other forms of instrumentation will want 30hz-20khz resolution. I don't think extension down to 20hz is needed. I honestly believe that extension down to 30hz, is a little over the top, but I like to have it if I can. I have a pair of SRX subs that can almost get me there.
Logged
I don't understand how you can't hear your self

Jason Lucas

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 806
  • Hillsboro, OR, USA
Re: aux fed subs
« Reply #28 on: February 04, 2014, 09:36:13 pm »

Don't forget there's more to the bass guitar than just the fundamental of the lowest note it can produce. A good bassist is going to playing a lot more notes than just the low E.

I don't concern myself with fundamental frequencies, I simply try to make the bass sound as balanced as I can.
Logged
There are three things I hate: Harsh highs, hollow mids, and woofy bass.

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 19222
  • Wichita, Kansas USA
Re: aux fed subs
« Reply #29 on: February 04, 2014, 09:44:22 pm »

I completely agree with the flat system, what goes in comes out idealism. I prefer to tune the system as flat as possible too. However I am not a fan of boosting frequencies more than 3db or so. I tend to believe that if the frequency gain wasn't there to begin with, then artificially adding it ( via an active EQ filter ) will only introduce phase and distortion artifacts, albeit minimal or marginally existent?

{big ol' snip}


"Flat" is not the same as "linear."  Scovi also spends some time driving home that concept.  That the terms have been incorrectly used as synonyms makes that a task of re-education.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut
Pages: 1 2 [3] 4   Go Up
 


Page created in 0.049 seconds with 21 queries.