Subwoofer 101

[Ambugaton]

Afternoon all, my band is beginning to use subs here and there depending on the size of our venue and... as always... a couple questions/issues have come up.

 

EQUIPMENT:

 

- Soundcraft EFX12

- DBX 231 EQ

- QSC GX5 and GX7

- EV ELX115's on top and the ELX118's for subs (I know 15's/subs is not recommended but it makes more sense for us)

 

QUESTIONS:

 

1) Will using the high pass filter on the EQ have a negative affect on the bass response on the subs? It is rated for -12db/octave at 50HZ.

2) What do manufacturers mean when they rate subs at -3 db and -10 db... I guess I just don't understand it. the EV's are 50-200Hz @ -3db / and 35-200 @ -10db.

3) I currently go from mixer > GEQ > QSC amps with built in crossover > speakers. All are going through only 1 channel of the EQ. So any changes to the EQ affects EVERYTHING... I know the logical solution = dedicate separate EQs... but do I have any other options for the time being?

4) I keep reading about aux fed subs... it seems like it would be a simple way to get the inputs being fed to the subs on the 2nd channel of my EQ. Would anyone recommend this?

5) Whats the proper way to EQ for a kick drum? I have looked up a lot of EQ "recipes" but I feel like some more specific tips or something would be helpful.

6) Ummm.... that might be it for now.

 

Thanks in advance.

[wesg]

0) Warning, I am an amateur like you.

1) Yes. You must send the low frequencies to the subs if you want to hear them.

2) You can think of (50Hz, -3db) and (35Hz, -10dB) as points on the frequency response graph. http://www.ecoustics.com/articles/understanding-speaker-frequency-response/

3) Do not engage the low-cut (high-pass) on your GEQ. Let the crossover high-pass the signal to the tops, that's what it's for. You want to feed your crossover a full-range signal..

4) Somebody will recommend aux-fed subs. I won't.

5) I like to use a bit of compression on the kick and twist the knobs until it sounds good. (see 0)

 

Wes

[agedhorse]

1. Without a high pass filter (there is not a meaningful one on the amp) you will seriously limit the spealer's power handling for mechanical reasons.

 

2. The HPF on the eq is pretty high, I would be looking at something around 35-40Hz, but 50Hz is probably better than nothing, especially if you plan on adding any LF eq to kik and bass channels.

 

3. No reason to explore aux fed subs (not that there is a meaningful reason to anyway) since it's not an option with the crossover inside the amp's processing.

[witesol]

You can pull down the first 3 bands of that EQ and let 31.5 bell curve up to where the EV subs should probably go anyways..

 

EQ for a kick drum? pretty broad question, hard to just give an answer. What kick mic do you have? What does the drum sound like acoustically? Does it have damping inside it?

You have to sort out your PA system, get it balanced well before you can get a good sound...that sort of applies to everything I suppose..

Does that little mixer have a HPF? It does have a swept midrange EQ though.. The way I do kick drum is put the mic in or in front of it, set the input gain, push up the fader. If it sounds good you are done. If it needs something you could add it with the EQ but I prefer to take away what I don't like instead. A channel of compression might help tame the drummer's dynamics but if you don't have much experience they can make things worse.

[Shaster]

Unless it really kills the kick, I would suggest using the 50hz high pass filter as well, but depending on your graph, pulling the ultra low frequencies out of the graph could also work - YMMV. As stated 50hz is high but better than nothing = especially for someone just getting started.

 

Question number two basically means there isn't a whole lot of sound activity at 35hz - not a bad thing unless you're only doing EDM.

 

I will frequently use Aux Fed subs when I don't have a crossover, and I have a powered sub(s). In your case you would need at least one external crossover but possibly two (to match manufacturer's crossover responses to slopes and xover points).

 

It's entirely possible that you won't need to aux feed. Use your 100hz cut on all mic channels (including acoustic instrument built ins), also dump your channel lows on things like hi hats, trumpets and so on. and don't hype the channel bass on your kick.

 

BTW, how are you currently assigning your amps to speakers? You didn't give us specifics - unless I missed something.

 

 

[Pro Sound Guy]

Your questions are all over the place man.

Get yourself some reading material and learn.

 

http://www.amazon.com/Sound-Systems-Optimization-Techniques-Alignment/dp/0240521560/ref=sr_1_1?ie=UTF8&qid=1406774369&sr=8-1&keywords=bob+mccarthy

 

[Craig Vecchione]

It's all good, and this is the place to ask.

[Ambugaton]

Thanks for all the info. To Pro Sound Guy... I figured the reason this forum exists and people continually monitor it... is simply because you enjoy talking about this stuff. I am no expert in this field but I am an expert in several other topics and generally I enjoy helping people out and sharing knowledge. Interacting with actual human beings makes me feel a little more connected to the information.

 

To Shaster: Even though I am a little underpowered at the moment I am powering both subs and tops with the GX7, so only 1000w going to each channel. Did you mean use the 100hz crossover on the amp? I don't have a 100hz cut on my mixer. The only thing I need to figure out now is how to get the kick and bass on a different eq channel. I can just insert the unused channel of the dbx into the drum kick channel on the mixer but I don't know how to get both sent to the same eq.

 

Once again I really do appreciate the info.

[Shaster]

Thanks for all the info. To Pro Sound Guy... I figured the reason this forum exists and people continually monitor it... is simply because you enjoy talking about this stuff. I am no expert in this field but I am an expert in several other topics and generally I enjoy helping people out and sharing knowledge. Interacting with actual human beings makes me feel a little more connected to the information.

 

To Shaster: Even though I am a little underpowered at the moment I am powering both subs and tops with the GX7, so only 1000w going to each channel. Did you mean use the 100hz crossover on the amp? I don't have a 100hz cut on my mixer. The only thing I need to figure out now is how to get the kick and bass on a different eq channel. I can just insert the unused channel of the dbx into the drum kick channel on the mixer but I don't know how to get both sent to the same eq.

 

Once again I really do appreciate the info.

 

I meant the 100hz (sometimes lower) cut on each individual channel. Under moderately loud conditions, not having a 100hz cut and running subs that aren't aux fed could be problematic - could be, YMMV.

 

With a different mixer, if you are only using the GX7 and are not using GX5 for monitors, you could take an aux from kick and bass, go to your other side of your EQ, go to your GX5, crossover your subs as per manufacturer's suggestion or amp limitations, take the low signal to your subs, and just forget about the high signal.

 

You would need to run another aux for monitors, to some powered monitors (or add another amp).

 

As you can see, you can't run aux fed subs with your current board unless you don't want monitors, or don't want FX - as you would need to use the FX out for monitors and the Aux 1 for aux feeding your subs. And IIRC there is no master for the aux 1 send! So as AH said, you don't have the gear to run aux fed. I mean, maybe there are ways to work around it, but why not just do it right?

 

With no 100hz cut on your channels, and only one sweep mid, and only one functional aux send, and no aux 1 master this would seem to be the wrong board for live sound for a band, even disregarding aux feeding subs. I used this board just for DJ/dance class duty and it was irritating and frustrating. Plus the mute button has no light. Grrrrr

 

If you want to stay Soundcraft, maybe try an FX16ii, otherwise get a MixWiz or a Zed series mixer both from Allen & Heath .

 

Have you tried this set-up with success? Perhaps your demands are less than I am imagining, and it's working, if so - carry on!

[abzurd]

Actually you still could run an aux fed concept by using the L & R on the mains. You'd run L to the low side of your crossover and R to the high side. Pan all channels you want no sub hard right and for the other channels come off hard right. You'll hear the lows come in as you move toward center. At center you're feeding full signal to both subs and mains. As you move left from there you are reducing the high signal.

 

Normally I'd say as a rookie no need to dive into aux fed subs, however, not having high pass filters on your channel strips, you will improve your sound by doing this as you'll keep all the low end gak out of the mic channels.

[Craig Vecchione]

All things considered, you've got a good small rig. It's got limitations, and you have to work within them. I'm reading a lot of concern on your part about EQ, but what you've got is plenty good to use with a very minimal amount of EQ tweaking. Less is more in this game. Aux fed subs are not all you may think they're cracked up to be, and if you don't have a lot of stage rumble or other low-end problems, there's nothing to gain by all the added complexity, especially when your rig isn't set up to accommodate it.

Regarding kick drum EQ...first things first. Does the kick sound good acoustically? Does it sound the same when mic'd? Remember that a lot of the kick sound is NOT in the subs. Also keep the rig's limitations in mind. You won't get chest pounding kick with a pair of ELX118's unless the room is tiny. But you will be able to get a good present kick sound. Practice using prerecorded material and the EQ, raise and lower sliders until you can hear what each change does. Again, go easy, less is more.

 

[Ambugaton]

My setup is working pretty well actually... but I am always looking for improvement. We play in and around a bunch of small towns and we definitely have the best sound out of anyone I have heard around here, except for a couple of the bigger bands that have $20k sound systems. Most bands around here are using behringer or very old and outdated PR215s or the JBL JRX215s.... lots of 215s around here for some reason.

 

I may be wrong here but if everything from the mixer goes through the QSC crossover at 100hz doesn't that do the same thing as hitting the 100 hz cut for each channel? I assumed the crossover would keep that low end out of the tops by itself. I think what I will do for now is just use the 2nd channel of the eq as a direct insert into the kick drum channel and see what the results are. As far as the kick sounding good acoustically... I don't know, it does sound about the same when mic'd, but I just get too much click and upper mids. I think having the kick on a separate eq is all I need though. Thanks guys.

[Shaster]

Actually you still could run an aux fed concept by using the L & R on the mains. You'd run L to the low side of your crossover and R to the high side. Pan all channels you want no sub hard right and for the other channels come off hard right. You'll hear the lows come in as you move toward center. At center you're feeding full signal to both subs and mains. As you move left from there you are reducing the high signal.

 

Normally I'd say as a rookie no need to dive into aux fed subs, however, not having high pass filters on your channel strips, you will improve your sound by doing this as you'll keep all the low end gak out of the mic channels.

 

Given that I've previously used the L/R method to aux feed, and even suggested it to others, I'll just claim my omission is due to the heat! That and it's too hot to drink coffee in the morning. Guess I should work on making some ice coffee...

 

 

[Shaster]

My setup is working pretty well actually... but I am always looking for improvement. We play in and around a bunch of small towns and we definitely have the best sound out of anyone I have heard around here, except for a couple of the bigger bands that have $20k sound systems. Most bands around here are using behringer or very old and outdated PR215s or the JBL JRX215s.... lots of 215s around here for some reason.

 

I may be wrong here but if everything from the mixer goes through the QSC crossover at 100hz doesn't that do the same thing as hitting the 100 hz cut for each channel? I assumed the crossover would keep that low end out of the tops by itself. I think what I will do for now is just use the 2nd channel of the eq as a direct insert into the kick drum channel and see what the results are. As far as the kick sounding good acoustically... I don't know, it does sound about the same when mic'd, but I just get too much click and upper mids. I think having the kick on a separate eq is all I need though. Thanks guys.

 

Well that's great, I'm glad your system's working for you.

 

The 100hz crossover point on your amp is just that - a 100hz crossover point. Sounds roughly above 100hz go to your tops, and sounds roughly below 100hz go to your subs. I say roughly because it is not a hard and fast cut off point. So no, 100hz on your crossover is not the same as a 100hz cut on your mic channel. In the first scenario your mic simply goes to both the top and the sub. In the second scenario, most of the signal below 100hz just gets dumped into the galaxy far, far away. Luckily for you, this doesn't seem to be a problem. It often is for me, but situation can differ.

 

BTW I wasn't intentionally insulting your board. They are good sounding mixers and very handy. I've just been frustrated with that particular model in the past, but if it's working for you then as I say, carry on mixing.