Sub-woofer distortion

vicmilt wrote on 1/30/2006, 6:25 PM

Having spent most of my life producing video for 5" TV speakers, I recently encountered a new (for me) problem.
Advice sought.

In playing back a video produced with ACID loops, on a super-Gucci sound system - there came across super loud subsonic bass noise, although on a regular TV there wasn't any hint of a problem.

What could have caused this, and is there an easy solution (like broadcast color filter is to video) to this problem?

Or do I need to equip my setup with a whole sub-woofer based editing sound system?

v

Comments

busterkeaton wrote on 1/30/2006, 6:56 PM

The easy solution is to use the EQ and drop off the very low end.

As to why it was there, don't know, -- probably it was there all the time, but your audio monitors didn't pick it up.

Spot|DSE wrote on 1/30/2006, 7:07 PM

Vic,
the distortion or low frequencies were likely always there. If you're mixing this sort of audio, it's a good idea to have at least a good set of speaks with minimum 6" drivers, and it's even better of course, to have a small sub, depending on the size of room you're in.
As Buster mentioned, using an EQ to roll off the low end will work, but it's a better idea to be able to hear what's going on.
Mixing audio with cheap speaks is like color correcting with a monochrome monitor.

DrLumen wrote on 1/30/2006, 7:16 PM

You might check the project audio properties and try different low pass filter frequencies to reduce the sound it's trying to reproduce . Not sure how much difference it will make as it depends on the cause of the distortion. If the sub driver is not blown (cone loose or voice coil damaged), lowering the volume and/or changing the LFE should help.

Just a thought...

farss wrote on 1/31/2006, 4:15 AM

Boy is this a timely topic!
Today I got caught out at the other end of the spectrum. Sent off DVD a few days ago to client, zillions of stills set to narration from clients client. Today client comes back with complaint about a few "glitches" in one of the audio tracks.
Well yeah I kind of noticed them too but a) not my recording / editing and b) didn' t sound that bad.
Ha, silly me, the client has all the studios fitted out with the second most expensive Genelecs money can buy. The offending "glitches" are cuts at around 1/2 FS, no doubt on the clients monitors they sound like something that'd strip the enamel off teeth.
A bit of work with Mr Pencil in SF should fix it OK.

Just wish I could afford Genelecs like they've got although I doubt the neighbours would agree.

Bob.

JohnnyRoy wrote on 1/31/2006, 5:15 AM

> Just wish I could afford Genelecs like they've got although I doubt the neighbours would agree.

Even if you don’t have Genelecs, having a fairly decent audio set up is critical if you are doing commercial video.

Vic, I have an M-Audio Firewire 410 with M-Audio Studiophile LX4 2.1 System + LX4 5.1 Expander System and the difference in audio quality when I got these over my existing Audigy 2 ZS with their 5.1 surround speakers was astounding. It was like someone removed the cotton from my ears. If you are just using the motherboard audio without any subwoofer, you are in for a shock if you upgrade to something like this. This is not an overly expensive setup but it will give you a much better audio reference for your projects. Especially if you are composing music in ACID.

~jr

busterkeaton wrote on 1/31/2006, 5:24 AM

I just bought the M-Audio LX4s. Pretty nice. They ain't Genelecs, but I would be amazed if they didn't show that something was there on the low end.

I got the 2.1 system for $200 at Sam Ash. I think that's the cheapest you can find them these days. I remember about a year ago some places were blowing them out for $280 for the whole 5.1 system.

busterkeaton wrote on 1/31/2006, 5:32 AM

Just searched on these from Froogle and there are a bunch up on Ebay right now, with still pretty good prices. I was looking at ebay for a while on these and usually the prices were higher. (I also knew that Sam Ash had the price on the for a while.)

Anyhow there are three systems for bid for about $100 with 1 day left and one of those is the full 5.1

DJPadre wrote on 1/31/2006, 5:39 AM

there are afew ways to deal with plosives in the sub channel whle mixing, alot of info can also be sought from Dolby.com

If u have the SOnic foundry noise reduction plugins, u can run the "clipped peak restoration" filter on your LFE track. I do this with -4, -6, -12, and -18 cuts with compression activated when a peak is hit.

There used to be a bug in vegas which would randomly peak the sub up to +17db... with 6c, i can see theyve fixed this issue...

another option is to cut the lower frequency to remove any inaudible Low frequencies... if u look at a subwoofer, youll notice how even though u may not hear it, the cone is still fluctating. This is rampant with vynil sources and alot of outdoor audio wher wind is concerned.
The parametric EQ on this cuts that out, allowing a cleaner pass of frequencies u can hear. If u dont cut those inaudible frequencies, This constant movement of the cone is literally displaced, therfore causing distortions in the "proper" recording. U might have the cleanest sound, but if ur subs are flying, its still goign to sound like 6 hours after a bad curry...

theres alot more to audio than meets teh ear...

as for monitors, i find berhinger truths to be rather brilliant.. if they sound good on these, theyll sound good on anything..

craftech wrote on 1/31/2006, 6:31 AM

Vic,

The simplest explanation of the problem is that the crossover frequency on the subwoofer is set too HIGH.

John

busterkeaton wrote on 1/31/2006, 7:20 AM

There used to be a bug in vegas which would randomly peak the sub up to +17db... with 6c, i can see theyve fixed this issue...

If you opened a project made it a previous version of Vegas, is it possible it would still be there?