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kasmira 21st February 2012 02:44 AM

My room, its acoustics, and my massive learning experience
 
2 Attachment(s)
Hello all! I'm sure most of you have seen my name randomly about the forums the past few months.

I just want to say thanks to everyone for their wonderful insight. This specific part of Gearslutz has a relatively tight-knit family that I've come to be very thankful for.

So, I've been busy building some panels. Not quite finished YET, but I've finally started to use REW and get the hang of it (I think)

My final plan is to have: (at least, until I test it and decide I need more :P)
2 - Floor to ceiling 15" soffits - Pink Fluffy R30
2 - 2' x 4' x 6" - Roxul AFB (2.5 pcf)
5 - 2' x 4' x 4" - Johns Manville Linacoustic RC
2 - 2' x 4' x 2" - CertainTeed EI-475 (For a porta-vocal booth)

All of these are currently built, except the soffits. I will probably end up building a large trap for my awkward back wall eventually

So far, I have made a TON of mistakes while building these, but, I'm sure I'll be able to conquer most of these little projects from now on with confidence. Very excited to build some more now that I've figured out what works best for me.

Once I finish all the panels and get everything situated correctly in my room, I'll be sure to move stuff out of my room, and test it, and move the panels in, test, move them around, test, etc and will post pictures of my room as it goes around.

Here are the current waterfalls and fr for my room. Hopefully, I've done these tests right. Freq response was measured with each speaker separately, and then averaged. Waterfall was done with 8 sweeps, both speakers on. I assume 8 sweeps would probably give you the best results.

Assuming I've done the tests correctly (they were done with a cardioid mic, though :/) then my room is looking pretty good already. I have a massive spike at 55hz or so - but I haven't built my 15" soffits yet. Hopefully those will take a big bite out of that. They will be floor to ceiling (8') and 15" square. I did buy the insulation for them yesterday, just have to wait till my next paycheck to buy the wood and build em.

Glenn Kuras 21st February 2012 05:56 PM

Quote:

2 - Floor to ceiling 15" soffits - Pink Fluffy R30
That is going to help but don't think it would solve it either. They are smaller then I would recommend and only 4 of them. 55hz is no small task to tame but just keep moving forward (things are looking good) and just add more if need be.

kasmira 21st February 2012 08:13 PM

Quote:

Originally Posted by Glenn Kuras (Post 7589638)
That is going to help but don't think it would solve it either. They are smaller then I would recommend and only 4 of them. 55hz is no small task to tame but just keep moving forward (things are looking good) and just add more if need be.

Yeah, I'd like them to be larger but the 15" just seems cheaper to build. The rolls of R30 that are 15" wide are insanely cheaper than the 2' x 4' batts in my area. The 15" wide rolls are $13 - which breaks down to $.41/ft&178; whereas the 2' x 4' batts break down to $.75/ft&178; - almost double the price. With a single roll, I can make two full 15"x15" soffits that are almost exactly 8 ft tall. Definitely more worth my time.

If I don't tame that decay as much as I like, I can always look into building two more soffits, again, for a killer price (other than the damn fabric mezed)

Even then, my room doesn't seem to look too bad, the entire room is already within a +/-6db (12db total) range, which is better than expected. Its just that super long decay time that's going to kill me. Especially since I do edm, I need some good response in this room.

I do only have some KRK Rokit 5 G2s in the room right now. Was going to upgrade my monitors a while ago but, within the suggestions of the acoustics forum I decided to do treatment first.

It is seriously astounding how much better my room sounds now. I have never experienced stereo image like this since I started producing. I didn't even know my Rokits went this low in frequency. After putting the panels in my room I feel like I DID upgrade my monitors. I can't wait till I actually do get some better monitors in my treated room, now. Until I get these soffits built I'm still stuck mixing bass in my Beyerdynamic DT880 Pros (which isn't too bad of a thing, I do love these headphones) but at least I can write stuff on my speakers now and not have it sound like shit.

Going through some of my previous mixdowns I can now understand why certain things don't sound like I thought they should in my car. Loving every minute and dollar I've spent on treatment.

Do my graphs look correct, though? I did only use a cardioid mic, I don't have an omni available (I never record anything) so I'm not expecting the graphs to be perfect, but as long as it shows me roughly where my long decays are, I can get to treating those areas.

How much of a difference am I looking at between using a cardioid vs an omni mic?

DanDan 22nd February 2012 03:44 AM

Good
 
Good stuff.
I wouldn't call the spike at 55Hz massive, nor the length of the mode(s) disastrous. And apart from that one anomaly the Waterfall is looking quite decent. It may be possible to move the listener position to diminish that modal boom. It may also be possible to shift the speakers to minimise it. If speakers were in a null of that mode it would not be well driven.

The slight downward slope towards LF I would rather see the other way. Maybe moving speakers closer to the front wall would give a little boost.
Turn on the Sig Gen with Frequency Follows cursor ticked. Slide the cursor over the 55Hz area. Move slowly and carefully, there may be two or even more modes very close to each other. Try to find maximum resonance. You can use the SPL meter. When the room is booming nicely walk about, find the hottest spots where trapping is possible. Make a map of the peaks and nulls which will hopefully confirm which mode is the main culprit. This will help inform listener and speaker positions. Keep an open mind, trappable hot spots could be a ceiling corner, or could be over the whole boundary. Don't forget the ceiling.
That is where you should place your LF trapping.

Quote:

Do my graphs look correct, though? I did only use a cardioid mic, I don't have an omni available (I never record anything) so I'm not expecting the graphs to be perfect, but as long as it shows me roughly where my long decays are, I can get to treating those areas.

How much of a difference am I looking at between using a cardioid vs an omni mic?
The measurements seem pretty good although if you have or can borrow an SPL meter you could try level calibrating. No big, it would just have realistic SPL on the vertical axis.
Even as they are, they work and they do show the 55Hz boom clearly.
To find out the difference a cardioid makes try turning it 90 degrees, then the full 180, i.e. sideways then backwards, all horizontally of course. You could also try vertical just in case you are missing a height mode. Look for differences in the Waterfalls.

Running 8 sweeps improves the Signal to Ambient Noise Ratio of your measurements, good for the Waterfalls.

DD

kasmira 22nd February 2012 11:59 AM

Quote:

Originally Posted by DanDan (Post 7591659)
Good stuff.
I wouldn't call the spike at 55Hz massive, nor the length of the mode(s) disastrous. And apart from that one anomaly the Waterfall is looking quite decent. It may be possible to move the listener position to diminish that modal boom. It may also be possible to shift the speakers to minimise it. If speakers were in a null of that mode it would not be well driven.

Well, that's all good to hear! I seriously cannot believe how much of a difference it has made. Once I get everything built I will be taking multiple measurements and posting them here. My room is 10'x10'3"x8 which is a pretty generic size so with my experience I hope to be able to show that there is hope for us in small rooms. My room sounded terrible before.

As my room is small there isn't much room to move listening position. My speakers are currently 6" away from the front wall both with a 2'x4' 6" thick trap of Roxul AFB 2.5 pcf in between the wall and speaker to help eliminate some SBIR for at least that boundary. I will try relocating the traps elsewhere and changing their position closer and further away from the wall, though moving them further from the wall will place me in an odd triangle with my speakers (too wide). I still haven't played with mode calculators and similar software yet so I'm sure I'll be able to come up with some better placement plans for my traps when I get there. Right now, they are pretty much randomly thrown about.

Quote:

Originally Posted by DanDan (Post 7591659)
The slight downward slope towards LF I would rather see the other way. Maybe moving speakers closer to the front wall would give a little boost.

I didn't even really notice that so thanks for pointing it out. Is it likely that this downslope could be from my mic or the fact that my speakers are just 5" KRK Rokits? Or a combination of both, perhaps?

I respect the time you put into posting in this thread Dan, I will be sure to follow your advice for placement (mapping the room, etc)

Can't wait to finish these soffits, might not be able to get them finished for the next couple of weeks though (damned traffic ticket) but I'll definitely be updating this thread. After I'm satisfied with the treatment, next project is a nice desk to work on! I don't have any rack gear so I'm sure it won't be as complicated of a build that's normally seen on here, but my desk barely fits both my LCD monitors and if I set my keyboard in front of me I can't even set my phone anywhere mezed

Again a big thanks to everyone who spends their time on these forums. I understand your time is worth money and this place is a ****ing goldmine. I would be sitting on a nice, newer pair of monitors right now with a room that still sounds like hell if it weren't for you guys!

DanDan 22nd February 2012 03:39 PM

Slope
 
Yes a cardioid is likely to have an LF roll off as are the Rokits. I overlooked that.
However the booming mode is exactly identified. Better mic or speakers won't change the mode's frequency.
The mode calculators can predict the modes which is useful, but the frequencies will not exactly match your measurements. The measurements are correct.

The Signal Generator trick, seemingly simple, stimulates the problem and shows exactly the best place to treat it.

I say this to everyone dealing with LF now. The future IMHO:-http://www.gearslutz.com/board/studio-building-acoustics/667929-my-experiment-metal-panel-absorber.html

DD

kasmira 6th March 2012 09:27 AM

2 Attachment(s)
Unexpected learning experience #1
Google Sketchup

Wow, is this program fun! Plus, the idea of the community getting involved to create thousands of pre-built to scale items is just wicked. It can be easy to say "Oh man, they don't have this modeled? Lame" - but realize just how many items there are otherwise that people spent their time making so you or someone else could use it in your drawing. Awesome.

Google has some great, simple "how-to" videos on YouTube if you haven't found them. Check them out at youtube.com/sketchupvideo

So, without further ado, here's some beautiful modeling I did of my room. Its missing some headphones, mics, webcams, my car keys, phone charger, etc. but you can get the general idea of whats goin on in here. Still haven't done a simpler floor plan with dimensions yet, but that will be coming. Anyways..:


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