Room FFT

KeithR · « **on:** 20 Jun 2012, 03:42 pm »

How bad is this, guys? My room is 24x23.5', but only use like 2/3 of it- it eats bass clearly. I did a Rives L1, so have ceiling tiles, floor to ceiling bass trap, and 6 panels throughout my room. I have bookcases along the back wall. Probably could use another rug or two, that I've neglected to do over the past two years.

Ideas?

JohnR · « **Reply #1 on:** 20 Jun 2012, 03:45 pm »

No sub?

jtwrace · « **Reply #2 on:** 20 Jun 2012, 03:46 pm »

What's the "Y" scaling at?

pelliott321 · « **Reply #3 on:** 20 Jun 2012, 04:03 pm »

Maybe you went too far with the room dampening.
As mentioned above looks like there is no sub and those monitors probably do not put out much below 60hz

poseidonsvoice · « **Reply #4 on:** 20 Jun 2012, 04:10 pm »

Quote from: jtwrace on 20 Jun 2012, 03:46 pm

What's the "Y" scaling at?

It looks like 10 dB scale. Look all the way to the right of graph he posted.

I agree, there seems to be no sub. Is there a way you can post your graph with more detail in the X axis, i.e. spread it apart a bit more so it's not so jumbled up?

Where is your microphone? Are you playing both speakers at the same time, or only one at a time during these measurements?

Thanks,
Anand.

jtwrace · « **Reply #5 on:** 20 Jun 2012, 04:13 pm »

Quote from: poseidonsvoice on 20 Jun 2012, 04:10 pm

It looks like 10 dB. Look all the way to the right of graph he posted.

Best,
Anand.

Good eye.

MaxCast · « **Reply #6 on:** 20 Jun 2012, 05:08 pm »

Is this the iphone app? My guess it is the mic in the phone and big room.

KeithR · « **Reply #7 on:** 20 Jun 2012, 05:30 pm »

sorry guys- I have different speakers (with built-in subs) now. that picture shows the room itself the best.

Here are a few others offhand:

KeithR · « **Reply #8 on:** 20 Jun 2012, 05:31 pm »

Quote from: poseidonsvoice on 20 Jun 2012, 04:10 pm

It looks like 10 dB scale. Look all the way to the right of graph he posted.

I agree, there seems to be no sub. Is there a way you can post your graph with more detail in the X axis, i.e. spread it apart a bit more so it's not so jumbled up?

Where is your microphone? Are you playing both speakers at the same time, or only one at a time during these measurements?

Thanks,
Anand.

from my listening position- I am using an iPad for this and Audiotools. both speakers playing wide band pink noise.

JohnR · « **Reply #9 on:** 20 Jun 2012, 05:33 pm »

Is the setup calibrated in any way? Sorry but if not it's sorta a waste of time.

KeithR · « **Reply #10 on:** 20 Jun 2012, 05:37 pm »

calibrated in what manner?

Audiotools is calibrated to use internal mikes for ipads/pods. fyi- my friend runs the same software in an untreated room and has rising bass (not surprisingly). i have only 1 bass trap in the room due to room config

my bass problem is that i have a large squarish room that can't pressurize.

TomS · « **Reply #11 on:** 20 Jun 2012, 05:38 pm »

Ah, Zu Def IV's with powered internal subs. It almost looks like the subs aren't being fed any signal at all to be 10-15db down starting at 120hz (?)

JohnR · « **Reply #12 on:** 20 Jun 2012, 05:55 pm »

Quote from: KeithR on 20 Jun 2012, 05:37 pm

calibrated in what manner?

Just that what's on the graph is fairly close to reality. It probably isn't, audiotools say "We have compensated for these mics as much as possible, but given the physics of the situation, the usefulness of the low frequency information is limited."

It's something to be aware of.

DTB300 · « **Reply #13 on:** 20 Jun 2012, 06:01 pm »

I have used the AudioTools app on the iPad and they do state there are issues with low end response using the internal mic.

The only issue I have had with the App is from 65Hz down, the response is always rising quickly. I have not contacted the company yet about this issue.

The rest of the FFT meausres/looks very close to other programs I have used with external mic's (berringer, RS, etc.)

MaxCast · « **Reply #14 on:** 20 Jun 2012, 06:20 pm »

Quote from: DTB300 on 20 Jun 2012, 06:01 pm

I have used the AudioTools app on the iPad and they do state there are issues with low end response using the internal mic.

The only issue I have had with the App is from 65Hz down, the response is always rising quickly. I have not contacted the company yet about this issue.

The rest of the FFT meausres/looks very close to other programs I have used with external mic's (berringer, RS, etc.)

that's what I have read too. All various iOS devices have different mics. I have used FFT on a iphone4 but don't remember it falling like that. Good to know that from 65 up...it's close

Keith,
Nice room. Did Reves to a measurement on it?

poseidonsvoice · « **Reply #15 on:** 20 Jun 2012, 06:38 pm »

Quote from: JohnR on 20 Jun 2012, 05:55 pm

Just that what's on the graph is fairly close to reality. It probably isn't, audiotools say "We have compensated for these mics as much as possible, but given the physics of the situation, the usefulness of the low frequency information is limited."

It's something to be aware of.

So, I assumed wrong. I assumed there was some degree of calibration here. It is even more important in the low end since most mics have poorer accuracy in this region (and in the top register as well like 10-20khz). In any case, talking about that FFT is a moot point if the mic is questionable. There is also the issue with reflections that occur when both speakers are playing and measured at the same time, so you end up seeing more peaks and dips than what is really there (i.e. above 300 Hz).

Any chance you can borrow a calibrated mic (like a Behringer ECM8000 from Cross Spectrum), a mic preamp, laptop, boom mic stand and make some detailed measurements without smoothing? I'm probably asking for too much but this is the acoustics circle no?

Best,
Anand.

KeithR · « **Reply #16 on:** 20 Jun 2012, 10:05 pm »

Thanks guys--Rives has not measured this room, as that costs an extra 1.5k thereabouts. To be honest, I wasn't really focused on the bass---more on that 100hz and up response and what improvements could be had. It seems like my treble really looks to falls off quite a bit, although it doesn't seem particularly warm in room. There is no issue with treble and these mikes from everything i've read.

I can also try my iPhone as well I guess- maybe that is the difference between the bass. Will do that this evening.

I don't have access (or desire in particular) to all the regular acoustic tools (REW, sound card, laptop, mike, boom, etc).

jtwrace · « **Reply #17 on:** 20 Jun 2012, 10:08 pm »

Quote

I don't have access (or desire in particular) to all the regular acoustic tools (REW, sound card, laptop, mike, boom, etc).

Well, then good luck.

MaxCast · « **Reply #18 on:** 21 Jun 2012, 03:11 pm »

Quote from: KeithR on 20 Jun 2012, 10:05 pm

Thanks guys--Rives has not measured this room, as that costs an extra 1.5k thereabouts. To be honest, I wasn't really focused on the bass---more on that 100hz and up response and what improvements could be had. It seems like my treble really looks to falls off quite a bit, although it doesn't seem particularly warm in room. There is no issue with treble and these mikes from everything i've read.

I can also try my iPhone as well I guess- maybe that is the difference between the bass. Will do that this evening.

I don't have access (or desire in particular) to all the regular acoustic tools (REW, sound card, laptop, mike, boom, etc).

I'll be interested in seeing the comparison between the ipad and an iphone. Please state which models you use.

To carry a step further on the cheep ($100 for meter, beheringer ufo, and cables) you could use REW and a rat shack meter for the low stuff. That's my goal, I have the stuff but not the time

*Scotty* · « **Reply #19 on:** 21 Jun 2012, 04:03 pm »

Keith,if you have AudioTools you also have the RTA program. It would be interesting to see if it agrees with your FFT measurement in the bass spectrum.
Scotty