Cab someone explain what is going on here? Strange room measurements difference

[Mentalrudy]

Hard to know what you're hearing particularly. Where are the consultant's graphs of before and after?

Hi Chrispy,
Here are all data measured by the firm.
Pic 1: before, sitting down at LP
Pic 2: before, standing up at LP
Pic 3: before, graph overlay sitting (purple) vs standing (red)
Pic 4: before, spectogram sitting
Pic 5: before, spectogram standing
Pic 6: before, RT-60 sitting
Pic 7 idem but standing
Pic 8 - 12: room modes calculated by Amroc
Pic 13: SPL after, sitting at LP
Pic 14: spectogram after, sitting
Pic 15: RT-60 after, sitting

And then, just for fun 'after' measurements were made with the addition of a sub, but without crossover/high pass (because of teh limitations of my amp) just to see if a sub would make a difference:
Pic 16: 16, with sub, no crossover, at LP sitting
Pic 17: with sub, no crossover, LP moved 1-2 feet forward. Gave best result subjectively
Pic 18: proposed crossover settings by firm

When reviewing these measurements carefully, maybe it's worth giving it a shot by swapping the amp to an amp with bass management and crossover + dsp, and moving the LP forward. Like f.i. the new NAD 389 or even just by adding a minidsp. My only reservations about the minidsp is the quality of the analog inputs (my listening is 75% vinyl). Although one could argue that what is gained by adding bass management and dsp will vastly outweigh the quality loss from the analog inputs on the minidsp. Am I correct?

 

[HarmonicTHD]

Hi Chrispy,
Here are all data measured by the firm.
Pic 1: before, sitting down at LP
Pic 2: before, standing up at LP
Pic 3: before, graph overlay sitting (purple) vs standing (red)
Pic 4: before, spectogram sitting
Pic 5: before, spectogram standing
Pic 6: before, RT-60 sitting
Pic 7 idem but standing
Pic 8 - 12: room modes calculated by Amroc
Pic 13: SPL after, sitting at LP
Pic 14: spectogram after, sitting
Pic 15: RT-60 after, sitting

And then, just for fun 'after' measurements were made with the addition of a sub, but without crossover/high pass (because of teh limitations of my amp) just to see if a sub would make a difference:
Pic 16: 16, with sub, no crossover, at LP sitting
Pic 17: with sub, no crossover, LP moved 1-2 feet forward. Gave best result subjectively
Pic 18: proposed crossover settings by firm

When reviewing these measurements carefully, maybe it's worth giving it a shot by swapping the amp to an amp with bass management and crossover + dsp, and moving the LP forward. Like f.i. the new NAD 389 or even just by adding a minidsp. My only reservations about the minidsp is the quality of the analog inputs (my listening is 75% vinyl). Although one could argue that what is gained by adding bass management and dsp will vastly outweigh the quality loss from the analog inputs on the minidsp. Am I correct?

I have not looked into the details. But all graphs are heavily smoothed (frequency) and employ partly different axis ranges which makes it is unnecessarily difficult to read something meaningful out of it. (At first glance the RT60 hasn’t changed much).

Can you ask for the raw data? For example REW (a common software to create this type of measurements and graphs). creates files with .mdat ending. This way you can apply your own smoothing, overlay the graphs and do better analysis. Afterall you paid for the data.

 

[OldHvyMec]

6 bass traps is not much for a typical room. Especially if they are not located optimally in relation to the problem room modes. Keep in mind that Helmholtz resonators are relatively inefficient, when comparing surface area to absorbed energy.

Few corner bass traps work. Cancel the peak frequencies in the bass region and go from there. The only way to do it properly is Helmholtz adjustable. They do not tame or trap a frequency. They neutralize it. There is a huge difference in the quality of the tunning. Most of the passive material used are very inefficient compared to a simple 7.00 usd quilted moving blanket layered in a 3.5" or 5.5" box frames. A heavy purpose size rug in front of the seated position (s).

Suttle diffusion is usually the key. I use live bamboo and cannabis plants. The ceiling is a choice. I don't like the studio look at all except in a studio. I use a drop panel in front of the seated position in one room on the ceiling. First points are treated one at a time. When "A" tone goes flat remove the last panel. I use heavy floor to ceiling curtains. They open or close as needed. Box frames, distance or curtains for the back wall. It took me about 4 months to tune two rooms and shop 40 years ago. The only thing that changed was my ears. BTW they look like any other room or any other shop (s).

All but a front room is being repainted and cleaned. My house is a disaster.
I finally found my oldest buddy a turtle. He's a million years old. I thought he went to heaven.

I put a tree on his back, moving diffusion. You put food down and he moves that way. You just have to listen.. Sorry no measurements. It is entertaining though.

 

[FeddyLost]

Without at least one pair of mdat files "before and after" it's not easy to tell what is going on in reality.
Regarding graphs that I see, I'd say you need to add up some bass, depending on your tastes, but anyway THIS must be heard like bass-light or thin.
If you are listening at low levels, this effect would be even more prominent.

Regarding possible fraud - it's also requires total understanding of what is going on and what was in your agreement with acoustic company and existing restrictions.
I suppose that people did everything that was possible in your situation, budget and aesthetical restrictions, and it was effective, because RT60 dramatically reduced.
And then they thought that all is done and you shall further fight with your sound by yourself, because agreement mentioned exactly this.

I'd rent something decent with automatic room correction and try to use it with your speakers and subwoofer at least if you don't want to investigate REW and everything around it by yourself. Or buy UMIK and measure what do you have exactly now. It will not hurt even if you will reposition your speakers or add subwoofer. SOme objective measurements are always better than nothing.

For further constructive discussion would be great to see original mdat files, scheme and pictures of your room and your equipment. Maybe you'll just need to add single subwoofer or reposition MLP to get bass back...

 

[Deleted member 48726]

There is an app on apple app store. It's called "KRK Audio Tools" it can be used as a tone generator and show the SPL spectrum in real time. Even without REW and a UMIK you should be able to measure peaks and nulls with this tool. It's free.

 

[FeddyLost]

I tried some reverse engineering to understand what can lead to such FR graph in room with your dimensions ...
Something like that, maybe - but not so exaggerated.
For example, it's like Dynaudio C1 on Stand 6 and high seat.
Woofers and listeners have collected a lot of modal zeros, so we see effectively roll-off below 85 Hz while C1 themselves are flat down to 40 Hz.

So, I'd recommend you at least download REW and check what positioning is possible in your case.
In such big room it's a lot of options to have upper bass more or less flat if room is dedicated.

 

[Mentalrudy]

I have not looked into the details. But all graphs are heavily smoothed (frequency) and employ partly different axis ranges which makes it is unnecessarily difficult to read something meaningful out of it. (At first glance the RT60 hasn’t changed much).

Can you ask for the raw data? For example REW (a common software to create this type of measurements and graphs). creates files with .mdat ending. This way you can apply your own smoothing, overlay the graphs and do better analysis. Afterall you paid for the data.

Good tip,
I asked but data weren't retained.

 

[Mentalrudy]

I tried some reverse engineering to understand what can lead to such FR graph in room with your dimensions ...
Something like that, maybe - but not so exaggerated.
For example, it's like Dynaudio C1 on Stand 6 and high seat.
Woofers and listeners have collected a lot of modal zeros, so we see effectively roll-off below 85 Hz while C1 themselves are flat down to 40 Hz.

So, I'd recommend you at least download REW and check what positioning is possible in your case.
In such big room it's a lot of options to have upper bass more or less flat if room is dedicated.

View attachment 259832

thank you for going through the trouble. Indeed, a rolled off low and supressed low mid, which makes everything sound hollow and thin. A bit like the PC speakers you'd hook up to your computer in the late 90's.

 

[Mentalrudy]

There is an app on apple app store. It's called "KRK Audio Tools" it can be used as a tone generator and show the SPL spectrum in real time. Even without REW and a UMIK you should be able to measure peaks and nulls with this tool. It's free.

Hey thanks man, that was a really fun app. Made me see the value of getting a calibrated usb mic and doing the rew measurements myself.

 

[Mentalrudy]

Hi everyone,
thanks for joining in on this discussion. Conclusions to me, so far, is that my hypothesis of fraud can be ruled out. Accoustic treatment, especially when there are budget and aesthetic constraints, cannot fix any dips and nulls. It can merely improve what is already there. And their tuned bass traps do seem to work at some frequencies, like f.i. the 130 hz one is performing very good. They took away some of the peaks in order to make the dips and valleys less obvious, and I guess that's really all you can do with treatment, apart from controlling the reverberation time. Anyhow, I'll do some measurements myself and I'll try out some room correction. A mini dsp flex could be put in between my preamp and amp and isn't that expensive, so I think I'm gonna give it a go.

 

[FeddyLost]

Anyhow, I'll do some measurements myself and I'll try out some room correction. A mini dsp flex could be put in between my preamp and amp and isn't that expensive, so I think I'm gonna give it a go.

I'd strongly suggest repositioning as first option if that possible.
Or maybe hooking additional subwoofer for LF augmentation below 100 Hz.

Adding some equipment without automatic calibration into existing system is not just plug and play.

 

[Mentalrudy]

I tried some reverse engineering to understand what can lead to such FR graph in room with your dimensions ...
Something like that, maybe - but not so exaggerated.
For example, it's like Dynaudio C1 on Stand 6 and high seat.
Woofers and listeners have collected a lot of modal zeros, so we see effectively roll-off below 85 Hz while C1 themselves are flat down to 40 Hz.

So, I'd recommend you at least download REW and check what positioning is possible in your case.
In such big room it's a lot of options to have upper bass more or less flat if room is dedicated.

View attachment 259832

Hi Freddylost,
Well, since you are 'addicted to fun and learning', as your handle says, you'll be pleased to learn how insightfull this simulation is. Without having a calibrated mic and without running rew (yet), I did some crude measurements with the KRK app, a db-meter app and plotted the data myself in excel. And lo and behold (in attachment): the grey graph - which is measured sitting on the bench at the current main listening position - follows your simulation almost exactly. Also interesting to note is that the blue line (sitting down at alternative available listening position) and orange line (standing up at current mlp) sometimes follow the grey line more or less but often are the complete mirror image. Amazing how such a crude measuring method corresponds to this simulation, even though even the scaling of the graph is different! Anyhow, this experiment taught me that - alas - my bad sound are modal problems, and not caused by SBIR. That means to me that it will be impossible to correct with room correction or by adding a sub (that will suffer from the same modal problems - as the Elac software visible in my first post already exposed). Only thing I can do is find a good position to minimize the damage, maybe to an extent that eq will have some effect. Are these conclusions correct? In that respect the blue line seems the most promising candidate, but I will see what I can do by being creative with room lay-out and feng shui;

 

[Deleted member 48726]

Hi Freddylost,
Well, since you are 'addicted to fun and learning', as your handle says, you'll be pleased to learn how insightfull this simulation is. Without having a calibrated mic and without running rew (yet), I did some crude measurements with the KRK app, a db-meter app and plotted the data myself in excel. And lo and behold (in attachment): the grey graph - which is measured sitting on the bench at the current main listening position - follows your simulation almost exactly. Also interesting to note is that the blue line (sitting down at alternative available listening position) and orange line (standing up at current mlp) sometimes follow the grey line more or less but often are the complete mirror image. Amazing how such a crude measuring method corresponds to this simulation, even though even the scaling of the graph is different! Anyhow, this experiment taught me that - alas - my bad sound are modal problems, and not caused by SBIR. That means to me that it will be impossible to correct with room correction or by adding a sub (that will suffer from the same modal problems - as the Elac software visible in my first post already exposed). Only thing I can do is find a good position to minimize the damage, maybe to an extent that eq will have some effect. Are these conclusions correct? In that respect the blue line seems the most promising candidate, but I will see what I can do by being creative with room lay-out and feng shui;

This graph looks fine to me. What is the issue? -Looks like a sub is solving the issue quite well. With a crossover it should be even better as overlap and cancellation is minimized.

PICTURE FROM OP, pic. #16, experiment with added sub (without xover)-->

 

[Mentalrudy]

This graph looks fine to me. What is the issue? -Looks like a sub is solving the issue quite well. With a crossover it should be even better as overlap and cancellation is minimized.

PICTURE FROM OP, pic. #16, experiment with added sub (without xover)-->

Well, because of the excessive smoothing on these graphs, I don't find they correspond well into what I'm actually hearing. And a sub won't solve the huge dips I measurend in the 200 hz and 450 hz region. Both very important regions for the body and bloom of especially male voices and the warmth of music. But it could certainly make things better, no doubt.

 

[Deleted member 48726]

Well, because of the excessive smoothing on these graphs, I don't find they correspond well into what I'm actually hearing. And a sub won't solve the huge dips I measurend in the 200 hz and 450 hz region. Both very important regions for the body and bloom of especially male voices and the warmth of music. But it could certainly make things better, no doubt.

Oh. Yeah, but I didn't see what smoothing is applied. Sorry.

Your dips are above the transition frequency. So it's reflected waves. Room acoustics should be the remedy. Either electrically or physical. Or both.

 

[FeddyLost]

Anyhow, this experiment taught me that - alas - my bad sound are modal problems, and not caused by SBIR. That means to me that it will be impossible to correct with room correction or by adding a sub (that will suffer from the same modal problems

If your placement and dips/peaks distribution have good correlation with an easy simulation offered by REW, most probably sound issues are linked with modal issues.
Adding a sub will easily help if it will be properly placed (i.e. you directly sit on it).
For best results you'd better play with placement of your speakers in room or use extended DRC/bass management.
If your source is mostly vinyl, I'd play with placement and light room treatment.

Since you don't provide any objective information regarding your room, equipment and placement options available, I had to imagine how one managed to almost completely lose bass in such big room after professional room treatment. That's possible only if you collected a lot of nulls and cut the peaks with bass traps.
I don't know if you really own Dyns C1 and placed them like I imagined, but I think that even repositioning speakers and MLP and playing with height of MLP can significantly chage your experience.

In that respect the blue line seems the most promising candidate

This line looks nice.
Not sure how much can we beleive to these measurements, but I'd give a try at least.

And a sub won't solve the huge dips I measurend in the 200 hz and 450 hz region

Investigations of narrow deep dips in midrange is troublesome because they can be induced by *BIR issues or some floor/wall bounce if you have hardwood floor and flat ceiling.
Even applying some absorption not always helps, so it's another issue.
Proper understanding of origins and real importance of some notching at these frequencies requires a lot of measurements and trial and error, because AFAIK floor bounce is almost inevitable in home conditions with single woofer speakers.

 

[FeddyLost]

it will be impossible to correct with room correction or by adding a sub

Again just guess about adding a subwoofer without repositioning everything else
I'd hook it just to try out.

And if you really want to make these experiments faster, it would be nice to know all the important info you hide.