Am I just thick?

[Alan Rothenbush]

I would like to flatten my listening room, using a lovely dbx 1/3 octave equalizer.

To that end, I've purchased a copy of Audiotool and a Dayton imm6 mic.

I've tested the mic using the builtin Android Sound Recorder app.  It works.  The sound quality is terrible, but it works.

The Audiotool generators work .. white, pink, sine, square .. all make the right noises.

I've downloaded and installed and loaded a calibration file, as per instructions.

But the RTA display shows .. garbage .. bars unrelated to the sound in the room.  The scope display though, it looks about right, albeit with lots of compression.

After an hour of manual study and diligent testing, I found the weirdest thing of all.

With the cable to the stereo plugged in AND THE STEREO TURNED OFF, I set the RTA to SPL.  Level shows 56 with all generators off, 92 with any generator on.  BUT THERE'S NO SOUND IN THE ROOM because the stereo is turned off.

Where did that 36 db of .. something .. come from?

Unplugged the cable to the stereo.  SPL = 56 with all generators off and 56 with any generator on, kinda as expected.

Plugged the cable back in, but stereo still off .. 92 when a generator is turned on.

What's it reading?

I am 2 minutes away from hauling out my 50 year old Heathkit tone generator and SM58 and analog level meter and doing this the old fashioned way!  At least I understood what was happening and what I was seeing.

Before I do that though, I have to ask .. am I just thick?  I ASSUMED Audiotool could make a noise and measure a noise at the same time, but maybe it can't!

Any thoughts appreciated.

Alan

[Julian Bunn]

Hi Alan,

That all sounds very odd! Can you perhaps make a screenshot of the display when you see the "garbage" RTA display? What exactly do you have plugged in to what ... and do you hear e.g. a sine tone through your stereo when the AudioTool generator is on? What does the Mic display look like at that point?

Julian

[Ian Eales]

 If you are using your phone as a generator, I'd suggest using a separate noise source

You can use a laptop with suitable cable from the phone jack

REW can generate any desired signals AND read the imm6

While I love AudioTool, I use it as check not system calibration.  

[Alan Rothenbush]

> If you are using your phone as a generator, I'd suggest using a separate
>noise source
>
>You can use a laptop with suitable cable from the phone jack

Yeah, that was next. 

My sine wave generator only does sines, not noise.  31 center frequencies, run through at least three times to readjust for interactions times 2 channels .. wasn't looking forward to it.  Sometimes the "good old days" really weren't.

>REW can generate any desired signals AND read the imm6

Had a quick look at REW.  Dismissed it because I didn't want to spend 8 hours learning it just to do a 2 minute calibration.

(I'm an OLD man .. 8 hours represents a significant chunk of the time I have left on this Earth.)

Audiotool seemed to have a more favourable learn-to-use ratio.

Might have to break down though, and do some reading.

AND buy a breakout cable AND resurrect an old notebook.  My current notebook has headphone only, no mic in.

(I wonder, how old a machine will REW run on?)


As I write this, I also have a thought.  The Dayton has a TRRS connector, and I THINK I read somewhere that the wiring is

T - L out
R - R out
R - Ground!
S - Mic

This seems weird to me.  I would have expected

T - L out
R - R out
R - Mic
S - Ground

Where the shield is connected to ground. 

There's actually a third option.  The ORIGINAL TRRS wiring came from the earliest iPods, and was

T - L out
R - R out
R - Video out
S - Ground

The connector on the tablet I'm using (4 year old Lenovo) is obviously wired for a mic.  But does it use wiring option 1 or 2 above; option 2 might explain my weirdness ..


However, if, as you suggest, I just go with some other noise source, it shouldn't matter how it's wired.


Alan

--
We can judge the heart of a man by his treatment of animals.

Immanuel Kant

[Alan Rothenbush]

Thanks for the reply!

Pics attached .. hope attachments are allowed.

Generator off, stereo off
Generating an 800 hz sine wave, stereo off
Generating an 800 hz sine wave, stereo ON
Generating an 800 hz sine wave, cable DISCONNECTED.



Alan

[Julian Bunn]

Interesting screenshots! I bet you are on to something suspecting the wiring, and that the ground in the headset output is not correctly wired to the stereo cable you are using. Do both channels sound like 800Hz sine on the stereo?

Regarding REW, I also tried it once, admittedly a bit half-heartedly, and found it overwhelmingly complicated, but it gets very good reviews and is obviously very powerful.

Julian

[Alan Rothenbush]

On July 21, 2026 2:52:42 PM PDT, Julian Bunn <jjb...@gmail.com> wrote:
>Interesting screenshots! I bet you are on to something suspecting the
>wiring, and that the ground in the headset output is not correctly wired to
>the stereo cable you are using.

I am "lucky" in that I have a decently new tablet that has died, and will be sent to the electronics recyclers.

Before it leaves though, I'm going to take it apart. This provides two benefits.

1. I get to take it apart! Always a bit if fun,
2. There is a good chance there's a TRRS jack in there I can steal to make my own cable and confirm my suspicion.

>Regarding REW, I also tried it once, admittedly a bit half-heartedly, and
>found it overwhelmingly complicated, but it gets very good reviews and is
>obviously very powerful.

Yeah, it looks like a wonderful product, but it's complete overkill for what I want to do, whereas Audiotool looks about perfect.

However, I remain suspicious of the mic input on the old tablet, even if it's wired "correctly". There's an awful lot of noise even with nothing plugged in. Plus, the frequency response is nonsensical. (I ran some tests using a standalone pink noise generator.)

What my ears .. aging or not .. told me DID NOT JIBE with what my eyes saw on the Audiotool screen. And the amount of EQ required to "make it flat" was nuts .. the full 24 db range of the EQ in the midrange alone. I know Klipsch aren't flat, but they're nowhere near THAT bad.

So next step was to bite the bullet, study some docs and give REW a try. First doc, "Getting Started" told me my old notebook was not going to cut it; the mic inputs were too poor. I would need to buy SOMETHING.

So, since it looks like what I have is not adequate .. that I'll have to buy SOMETHING, I think the plan is to buy a USB mic adaptor to use with my iMM-6 and run Audiotool with that setup, on a newer tablet.

Thanks for all the help!


Alan

P.S. Any suggestions for such a device .. inexpensive USB mic preamp ? It's really going to be a single use device; flatten my room with my 1/3 octave EQ and then put it all away.

[Alan Rothenbush]

Nope, not thick, just using the wrong tablet.

Turns out my wife's Samsung has a 3.5 mm jack and it appears to be wired correctly; my Dayton iMM-6 works just about perfectly.

So no studying of REW documentation, Audiotool docs only.  And more importantly, no added gear to buy.

Thanks to all who replied.

Alan