problems in high freq. but not in measurement?

[oneofakind]

Hey there,

i have new speakers (JBL L100 Classic MKII) and if i turn the volume up, i get really annyoing distortion (?) and scratchy noise in higher frequencies. I have a naked conrete wall to my left and i "hear" that the annoying hiss sounds come from that. I've put up a bed mattress behind me and to my left on the walls and the problem was gone. So i do some room absorption on these walls next.

But now my question: I measured my room with a UMIK 1 and REW but couldn't see the problem in the measurements. The measurements in higher freq. look pretty good (to me)

How does this come?

smoothing is 1/6, measured at 80db

 

[ppataki]

Reflections are visible on the Impulse Response curve
You could post that so we can take a look at it (or post the whole mdat file)

 

[DSJR]

I appreciate the room may well be the issue (do you toe the speakers to face you rather than pointing straight ahead?), but it'd also be nice to know the amp being used please as in my time, I've known so many that 'let go' badly when clipping point is reached, with tweeter blowing consequences...

 

[oneofakind]

Reflections are visible on the Impulse Response curve
You could post that so we can take a look at it (or post the whole mdat file)

uh i don't know much about that graph. I upload the mdat as a .zip

do you toe the speakers to face you rather than pointing straight ahead?

Yea i tried both and many other placements. The problem was only gone when having the mattress behind and beside me.

but it'd also be nice to know the amp being used

i tried: Technics SU-G700, Yamaha AS-701, Marantz NR1508 and some cheap SMSL amp. All sound the same

 

[ZolaIII]

What's the positioning of speakers? Can you put speakers better so that you get more dispersion from wall behind? Show the FR and waterfal along with RT60 decay times and clarity after fixing the room mode 43 Hz with PEQ. The 200~250 Hz boost is typical for those speakers and easy to fix (and a good think they have all that possibility of output there on the long run).

 

[ppataki]

uh i don't know much about that graph. I upload the mdat as a .zip

Thanks for sharing the mdat file

Here are some things I can see that could explain what you hear

Taking a look at the IR curve I can see a huge reflection here:

You can see those two huge spikes - there shall be only one of them (the impulse). The other is the reflection

Ideally you shall see something like this:

Try putting absorption sheets on the critical wall (5cm thickness shall be fine) and then re-measure the system to see/hear the difference - there shall be a huge difference before/after

Then if I check the Spectrogram (Wavelet) I can see oscillation in the higher frequencies:

Ideally you shall see something like this:

Again, this shall be much better after applying some absorption sheets on the wall(s), treating the first reflection points

After you are done with that I would recommend using some digital room correction too (REW or others like Dirac Live) - will make a HUGE difference

Good luck and let us know your progress
Happy New Year!

 

[oneofakind]

What's the positioning of speakers?

Unfortunately i can't get them more out of the corner.

Show the FR and waterfal along with RT60 decay times and clarity after fixing the room mode 43 Hz with PEQ

Right now i only have a Marantz NR1508 pre out to Audiophonics MPA-S250NC power amp. I guess the Marantz only has normal EQ and not PEQ? I'm not sure. Maybe i'll buy a minidsp and put it between both amps in the future.

The 200~250 Hz boost is typical for those speakers and easy to fix

how?

 

[oneofakind]

Again, this shall be much better after applying some absorption sheets on the wall(s), treating the first reflection points

After you are done with that I would recommend using some digital room correction too (REW or others like Dirac Live) - will make a HUGE difference

Good luck and let us know your progress
Happy New Year!

Thank you very much! Now i know what to look for in the measurements after i did some room treatment. In the long run i wanna integrate a minidsp 2x4 with Dirac but for now i want to get as best as possible results in pure direct.

Thank you and happy new year to you too!

 

[Digital_Thor]

Try and look into 2 things for starters.

Look at the way your speaker has a dispersion, way different than speakers with bigger waveguides, coaxial designs and narrow cabinets.

Second... Use gating/windowing in your measurements at both on and off axis, to make sure that you only see what the challenges are, exactly for your set of speakers.

My findings, after doing exactly that.... And trying out the difference by going to tons of demos, friends and doing all sorts of DIY. Is, that less acoustically treated rooms, are mostly nicer to listen to music in, when using speakers that have a slightly narrow dispersion, which also is smooth and controlled - imo.

EQ can do wonders. But the source and the loudspeaker itself, play a much more important role. Isolating and understanding the difference in measurements. Greatly increase the chance of using eq most successfully.

 

[ZolaIII]

View attachment 339026
Unfortunately i can't get them more out of the corner.


Right now i only have a Marantz NR1508 pre out to Audiophonics MPA-S250NC power amp. I guess the Marantz only has normal EQ and not PEQ? I'm not sure. Maybe i'll buy a minidsp and put it between both amps in the future.


how?

As much as I can see you could move entire setup a bit from side wall and back wall to the corner cauch and tilt the speakers towards listening spot a bit.
You can try for free with PC using EQ-APO and REW (exporting to APO). The mood (43 Hz) rings a lot being 6 dB up and masks a lot of everything else. It's very common place for a such. You first do it with no smoothing and then measure again with that PEQ active and do the rest of the bass EQ-ing with 1/6 smoothing and only then we can even talk about what you are getting in highs. Also it's import that you match the SPL out of L & R chenel as speaker close to the side wall and in corner will have more gain from refractions.

 

[oneofakind]

I already moved them out as much as possible and tilted them.

You can try for free with PC using EQ-APO and REW (exporting to APO).

That's a good idea but unfortunately i don't have a PC nearby. Only a macbook and i can't find a EQ-APO alternative for mac for free.

My findings, after doing exactly that.... And trying out the difference by going to tons of demos, friends and doing all sorts of DIY. Is, that less acoustically treated rooms, are mostly nicer to listen to music in

fair enough but i already know that i absolutely loved the sound with the two big mattress behind and beside me.

 

[ZolaIII]

Huh you could try out JRiver (one month for free) but again I would prefer you do that on Windows and with WDM JRiver driver as output. Anyway the 43 Hz room mode ringing is your main problem and when you resolve it (narrow PEQ) and make uper bass more controled you have done 90% of work which can be done (with L R leveling of course). You need to do this in DSP form as acoustic treatment won't help (big resonator could but you won't have place for it). Playing with mattress is praiseworthy.

 

[oneofakind]

I would prefer you do that on Windows and with WDM JRiver driver as output.

Could i achieve the same with Roon integrated EQ?

 

[ZolaIII]

Could i achieve the same with Roon integrated EQ?

You can but in any case it won't be on a system level so you won't have measurable (with REW) in site of what it actually did and will stick only to the Roon's output.
Edit: in case of Roon or JRiver or anything else REW doesn't support direct export to you manually by hand input REW default calculated PEQ's for desired range of frequencies.

 

[Sokel]

You can but in any case it won't be on a system level so you won't have measurable (with REW) in site of what it actually did and will stick only to the Roon's output.
Edit: in case of Roon or JRiver or anything else REW doesn't support direct export to you manually by hand input REW default calculated PEQ's for desired range of frequencies.

He can do what whatever measurement he wishes through any media player by downloading the desired IR signal (or sweep,or whatever) from REW's generator (use of save) and then measure with the "from file" function after loading the IR file and the time reference enabled.

You just hit "measure",playback it from whatever MP and that's it.
I do it all the time measuring whatever I use in foobar and comparing it with REW's raw measurement.

 

[ZolaIII]

@Sokel yup he can tho it ain't exactly handy. I do it only for final calibration as I apply the RBA R128 to the white noise from file to take it in account for loudness normalisation (even it's minimumal and under 3 LUFS for such).