# All things the same-why are these waterfall measurements different?



## jlird808 (Nov 2, 2010)

These test were taken just seconds apart:



















How does a 60hz resonance just disappear like that? I've noticed while using REW that freq plots rarely change very much, but waterfalls can vary quite a bit.

Can someone explain this to me? Sometimes I'll be deadset in building a tuned trap to treat a resonance, but then a test will show that it's not there.

Sorry if it's a noob question.

Thanks!

Also....would u consider the 60, 80, and even that ~225hz resonance a "problem"?


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## Phillips (Aug 12, 2011)

jlird808 said:


> These test were taken just seconds apart:
> 
> 
> 
> ...



To me it doesn't look like a 60hz resonance, (see how it doesn't decay at all) this happens to me occasionally.

It could be a few things e.g. power.

Send some frequency graphs as well.

Is this mains or subs or both etc.


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## jlird808 (Nov 2, 2010)

Phillips said:


> To me it doesn't look like a 60hz resonance, (see how it doesn't decay at all) this happens to me occasionally.
> 
> It could be a few things e.g. power.
> 
> ...


Thanks for responding....









I'm a home recording guy, so this is a project studio setup, with two Yamaha HS80m full-range monitors.










An older but floor layout, but pretty much the same (more bass trapping now):










I ran some sine sweeps and there is excess 60 & 80hz in the floor-wall corners flanking the desk. Found em using an SPL meter.

Is there anything I can show u? My PC is right below the desk, could that put out a tone that low? 

Thanks again!!

Just learning about RT60 testing...does this help? Does this look ok? From what I've read, if I'm between .3-.5, I should be good


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## Phillips (Aug 12, 2011)

jlird808 said:


> Thanks for responding....
> 
> View attachment 39569
> 
> ...



Can you post seperate speaker measurements L&R and combined 1/6 smoothing. With REW i tend to use this, as this is more what we hear. 1/12 smoothing is good too to see what is happening. I like to try and keep the response -+5db in the bass region with 1/6 smoothing.

Also i notice a big drop off in the high end about 6.5k up.

The T60 is ok but ideal to have as even as possible. Mainly down in the 350-800hz region could be improved. 

Do you use power or battery for your laptop when measuring?

With the bass region once measured seperate speakers by moving the speaker/listening position might improve this region.

Which mic/pre setup do you have. Is the mic calibrated?
SPL meters are good to a point.


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## Wayne A. Pflughaupt (Apr 13, 2006)

jlird808 said:


> How does a 60hz resonance just disappear like that?


 It’s not a resonance. Any audio signal, once it ceases, will fade away. That’s a steady-state signal from something like an air conditioner, refrigerator, washing machine, etc. So yes, it can “just disappear.” :T



> Also....would u consider the 60, 80, and even that ~225hz resonance a "problem"?


Not as big a problem as the big hole in response between 40 and 80 Hz.

Waterfalls are useful for FYI and to gauge improvements when treatments are added, but that’s about it...

Regards,
Wayne


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## Barleywater (Dec 11, 2011)

AC line interference, acoustic or electrical is steady state. This is small concern if not present in recordings. Symmetry of speakers to sidewalls may make imaging good enough for basic panning in mix, but sidewall, front wall make EQ of mix unlikely to work well when played back elsewhere. 60-80Hz is dominantly floor ceiling mode. Trapping these wavelengths would pretty much require filling entire space that rig is in.

Careful EQ of setup may help, but sweetspot will be fairly small in which response is accurate.

Regards,

Andrew


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## mtbdudex (Jan 2, 2008)

Ha, I've seen that before in my own set-ups, it's classic 60hz ground loop....sometimes very-very slight, check your connections tight, everything plugged into same 120v circuit.
See this here, same









When I plug my iMac into the wall plug circuit, which is different than my sub circuit, it always shows up.
Just means I need to get a few more wires out, hence the orange 120v ext cord that plugs into my 20a furhman delay


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## jlird808 (Nov 2, 2010)

Phillips said:


> Can you post seperate speaker measurements L&R and combined 1/6 smoothing. With REW i tend to use this, as this is more what we hear. 1/12 smoothing is good too to see what is happening. I like to try and keep the response -+5db in the bass region with 1/6 smoothing.
> 
> Also i notice a big drop off in the high end about 6.5k up.
> 
> ...


Thanks for everyone's comments!

Im using the desktop to measure, not a laptop. Measuring with a Dayton EMM6 with a (supposedly) unique cal file. 

I'll try re-measuring this weekend one speaker at a time and post the results.

60hz could be ground hum hmmm...? I wish I knew more about electrical systems. I've got a lot of cables plugged into 3 power strips that all run to one paired-outlet....probably super stupid :dumbcrazy: No other outlets around though :sad:

I dont know what to say regarding the drop-offs at 6.5k and between 40-80. Regarding the 6.5k, a touch of the mic would resolve that, but maybe cause a dip elsewhere.

For the 40-80hz dip, I've found it hard to resolve that, maybe I need to build a tuned panel trap for those freqs? Im running out of space for broadband bass trapping. Also, I thought that SPL measurements weren't as important as waterfalls when it comes to low end measuring? I thought controlling the roll-offs/resonances was more important. Plz correct me if I'm wrong.

I'm just learning about RT60, so forgive me. How would I go about bringing that 350-450hz hump down....just more treatment for those frequencies? 

THANKS!!! :bigsmile:


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## Wayne A. Pflughaupt (Apr 13, 2006)

jlird808 said:


> 60hz could be ground hum hmmm...? I wish I knew more about electrical systems.


I doubt it’s from a ground loop. If it was it wouldn’t have “just disappeared” the way it did. It’s most likely from an extraneous source.

I dont know what to say regarding the drop-offs at 6.5k and between 40-80. Regarding the 6.5k, a touch of the mic would resolve that, but maybe cause a dip elsewhere.



> For the 40-80hz dip, I've found it hard to resolve that


How ‘bout equalizing?

Regards,
Wayne


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