Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Tim Hawn]

If you're going to use an aux fed sub, must you sacrifice control of the sub frequencies on your graphic EQ?

Currently I do a mono FOH mix with aux fed subs.  Mix 1 (full range) goes to the graphic EQ and then to the right input of a stereo 2-way crossover.  Mix 2 (subs) goes directly to the left input of the crossover.  The sliders below 100Hz, therefore, control nothing.  

I typically don't need the graphic below 100hz, so this is not really a problem.  I am just curious as to how others mitigate this issue.

-TH  

[Nick Aghababian]

I wouldn't use Aux's for subs, and expecially not full range speakers. I am a firm believer in letting your crossovers do their job.

I would suggest hooking up your mains to the EQ, EQ to the Crossover, (depending on what subs and full range speakers you have) set the crossover to about 100hz, then LF to the sub amp, and HF to the full range amp.

[Garry Wilson]

When I run aux fed subs, this what I do;

I do not use the crossover on the tops, I let them run full range. So signal path is; mixer (mains) out, to EQ in, EQ out, to the amps. I do have an comp/lim in the signal path.

For Aux Fed Subs; Aux out, Crossover in, Crossover LOW out, to amps. Crossover frequency selection is base on which Tops I use.


I find that typically the way the "Tops/Mains" sound with an external crossover unit at around 90hz - 100hz takes a lot of the fullness out of the vocals and this is where your conventional setup with subs help. This doesn't come into play if the Tops are running at full range.

Most EQs will have a 40hz filter(or some other) anyway, so I'll engage that and normally won't have to mess with the EQ sliders from 100hz on down anyway, but the control is there if needed.


Hopes this helps, because I get excellent results in my Aux Fed setup.


Garry W.

[Brian Houchin]

Nick Aghababian wrote on Fri, 04 August 2006 14:44

I wouldn't use Aux's for subs, and expecially not full range speakers. I am a firm believer in letting your crossovers do their job.

I think he is asking whether or not people running sub feeds on an aux are running them through an EQ or bypassing and going straight to the crossover, not whether or not to use aux fed subs.

[Chris Hinds]

Hi Tim,

When running subs on an aux I've generally always connected the aux direct to the processor and taken the main mix via the graphic, just as you are doing now.  If I have needed any processing below 100Hz I've used the Parametric EQ in the DSP to achieve this, however in an analogue setup you would have to add another graphic.  I can't imagine the need for this though unless you are running a feed from a DJ where you want to send the signal to the subs but the subs feed back into the turntables.  I would say most of the LF feedback issues would be resolved by having most sources not linked in to the subs.

Hope that helps

Regards

Chris

[Geri O'Neil]

Aux-driven subs are, for practical purposes, best done with a digital speaker processor. Drive the mains with one or two inputs of the processor and the subs with a single input. Since you (usually) don't dedicate a 1/3-octave grahpic EQ to the subs, you'll have some parametric EQ control should you need it. If you're stuck using an analog crossover to low-pass subs, then it would be good to have something for some EQ control, again  should you need it. But not totally necessary. 20hz to 80hz, where most subs low-pass anyway, is 2 octaves, so it's up to the user's needs as to whether or not they will need EQ. On our MX-8750s, I have 6 bands of parametric EQ on the inputs and 5 bands on the outputs. That's 11 bands of EQ, plenty of EQ for 2 octaves of sub energy (I have been fussed at by a couple of bands guys for not having a graphic EQ on the subs and that tells me that the guy doesn't understand the nature of  parametric EQ.
Keep in mind that the speaker processors will usually have comp or limiting abilities as well. I've said this before and I've been met with much disagreement, but in this day and age of inexpensive digital processing and with the performance that even small club providers are expected to deliver, there's no reason to use an analog crossover anymore. It's fine if you do and get acceptable results for whomever you're responsible to (yourself, your band, employer, etc.).

Geri O

[Dave Rickard]

Nick Aghababian wrote on Fri, 04 August 2006 13:44

I wouldn't use Aux's for subs, and expecially not full range speakers. I am a firm believer in letting your crossovers do their job.

Nick,

Have you read this article?   http://www.prosoundweb.com/install/tech_corner/auxsubs.shtml

I ask because you are relatively new here.  Many have found this to be a fine technique.

Dave

[Dave Rickard]

Tim,

The info here--  

ftp://ftp.eaw.com/Processor_Settings/Current_Products/Subwoo fer_PROCS_rev2.pdf  

--suggests that EQ would be beneficial in most cases.

That said, I use an EQ before my analog crossover, but if I need a spare graphic that day, I eliminate it.

Geri O's points are always worth noting, but you already knew that.

Dave

[Greg Cameron]

Hi Tim. If you want to add EQ for aux fed subs using analog processing, you'll want to go the Parametric EQ route. A regular 3rd octave EQ is nearly useless for tweaking only subs, as only a few sliders will fall within the band pass of the subs. With the correct multi-band parametric, you can use all the filters within that narrow band and have good control of the affected bandwidth using the Q controls. On my setup, I run the tops off of a processor, with a BSS graphic at the input. I uses the HPF on the BSS to roll-off signal to the tops. The slope is 12dB/oct, pretty slow. I set the HPF usually between 120-160Hz depending on the venue. The subs are processed with an Ashly parametric EQ, BSS analog crossover, Symetrix limiter, are low passed between 60-70Hz. The setup works very well.

As others have stated, a digital processor with the right number of in's and out's can handle all of this for you. Since my mains and subs are Rat Sound, I use their method which means analog processing for the subs.

Greg

[Mike {AB} Butler]

Nick,
As one who has been using the aux-fed-sub technique for the last ~7 years, I'm curious what your issues are. I think it's a fabulous way to get response from the inputs you ONLY want to feed to the sub, as well as tonally shape the sound balance (less or more than unity). A standard LP fed sub has none of these things.. and can actually cause problems on inputs you don't want to see problems on.. such as vocals..
Regards,