REW First Measurement

[mhconley]

I ran REW yesterday on my stereo system, not the A/V system I listed in my profile. My stereo consists of the following equipment: YS-Audio Audio Experience Balanced A2 preamplifier; ICEpower 1200AS1 & Tube Fantasy 300b PSET monoblocks; Von Schweikert VR-4 Gen III HSE speakers; Topping DX7 Pro DAC; Volumio on Raspberry Pi4; Pro-Ject Phono Box RS phono preamp; Opera Consonance LP-2.0 turntable; Mørch UP-4 tonearm and a Grado Sonata 2 cartridge. The ICEpower amp is on the woofer module of my speakers and the 17W PSET is on the tweeter midrange module. I use a Yisheng HiFi Relay Volume Control on the ICEpower amps to balance them with the PSET amps.

My room is odd shaped and untreated. My amps sit between my speakers:

Just to the right sits my LP storage (IKEA Expedit) and preamp:

This image shows the relation of the Expedit to my speakers (covered with boxes when not in use):

This is the layout of the room:

There is a Kurzweil Mark 150 digital baby grand piano on the angled wall. The wall behind my chair is kneewall that is just slightly higher than the chair. The opening next to my chair is into a good sized living room and the open doorway on the left is the kitchen.

Here is a psychoacoustic smoothed plot of my first set of measurements taken from my listening position (L+R .mdat attached):

Red is R, green is L and blue is L+R.

I have six 2' x 4' 2" rockwool acoustic panels that I used without measurement in a prior home that I can use in this room. I'd like to reduce the suckout at 110Hz and hopefully address the entire range between 65 and 450Hz.

The Von Schweikert crossovers are acoustic fourth order at 150Hz and 1600Hz.

My question is that now that I have my first set of measurements, what is my next step?

Thanks,
Martin

 

[DanDan]

Acoustic treatment would radically improve your listening experience at relatively small cost. As you can see you have some VLF rumble. If those speakers have Reflex ports you could try blocking them, completely with a bung, or partially with cotton wool. You have a massive hole at 100Hz up to 200Hz. I recommend moving the speakers and listener positions to all viable locations, without any preconceptions.
Try close to boundaries, almost touching. Try everything!

 

[mhconley]

Thanks. I’m going to start moving things around, play with placement of my acoustic panels and taking measurements. I’ll be back...

 

[DanDan]

You are welcome. I recommend playing with Source and Listener positions. Treatment location follows those.

 

[pinox67]

Dips and peaks in low frequency bands are mainly due to room resonance modes, that can be more or less excited by louspeakers position. A big contribute is due to the reflection of sound from loudspeakers with the near front wall and corners. Moving loudspeaker can help yes, but I think it would not sufficient to correct the frequency response. I would suggest to use some bass traps in the corners to absorbe sound. Try to measure spl in these positions and you will see on which audio bands (those with a too high level) you should act. Also flat reflective walls do not help to spread well the sound in the middle-high audio bands, making sound harsh and not 3d. You should try with some panels that Absorb or better diffuse the sound. RT60 graph by REW can help you to see on which audio band the sound has a too much reverberation to control. Try to do similar treatments on specular walls.

 

[ola1]

Probably the most important but disputable point is how are you measuring/

What kind of microphone?

Are you using any calibration for your microphone...

So lets get that out of the way. Considering what you have already spent on gear, depending on how accurate your intentions are, spending a bit on a microphone which has calibration would be my 1st stating point.

Then what is the height of the measurement microphone, relative to the speakers...

Why, in a non concentric set of speakers, what you hear is an interaction between all the drivers, at the listening position..

Therefore the distance from the measurement microphone to each of these drivers is significant.. there will be some interaction, between the same frequencies coming out of each adjacent driver (frequency wise) ....at the measurement position.

Guess what even in the most high end professional studios, the measurements are not flat, cos of this interaction alone...

Then we hae coupling between the speakers and the floor.............and between the speakers and the closest walls - i,e SBIR, which boosts and cancels frequencies.....

So play around with moving the speakers nearer to or away from the closest boundaries and pick your nicest poison. Nothing will be perfect only less worse..

Then there is speaker bounce....which is the coincidence of direct and indirect sounds, some bouncing on the floor before reaching the listening position.

Some absorption on the floor a this bounce position, typically carpeting will help....

Then there is what I call a weakness in all measurements, a variance between what is measured and what we hear......

IMHO, most tools like REW use an averaging method, which makes it difficult to accurately separate the direct signal from the reflections,

I tend to use longer sweeps, the theory being there is more information, but this also has a flaw, cos it also rings out the resonances in the speaker cabinet pretty well, which may be a good thing.

So many factors to consider, my view is this :

1. Because of the multifactor nature of acoustics, do not worry too much about each aspect. a bit here a bit there. fix what you can within budget.

2. DSP done right can take things one step further, especially if you accept a compromise that this will only improve the end result predominantly at the listening position..., if you want the best results. Any DSP solution that attempts an averaging of positions is simply giving you an average result everywhere, rather than a best effort at the listening position. I accept the compromise of listening in a compromised smaller area, cos I prefer the higher quality of correction from a measurement at the listening position.....

I apologise teh DSP method I have found to work convincingly will take too long to explain, but just to give you hope, it does work, and works very well, with aforementioned compromise..

3. Live with the result of your best effort....

4. It is an evolution not a revolution, some of this takes time to fully understand and learn and improve your results.. You are not likely to get it right the 1st time, cos it does take a while to think through the problems and apply logic, sometimes doing unconventional things.......

Do you realise that the audio from both speakers will also interact with each other at the listening position... so your lovely measurements are only a partial reflection of the truth...

I would not recommend using the Psychoacoustic view measurements, much easier to go with the direct measurement of the microphone and take it from there.....The psychoacoustic introduces one more anomaly in the interpretation, best avoided IMHO. nice for academia research, but just one more thing to worry about when you already have many other factors to deal with and resolve...

With speakers close to two walls, also bouncing off a ceiling, and floor, that' a very complex interaction especially in the low end...DSP or EQ filter to cut out the boominess below about 80 Hz is a quick fix. works wonders.

 

[linearphase]

Thanks. I’m going to start moving things around, play with placement of my acoustic panels and taking measurements. I’ll be back...

I see a dimension but can you interpret it for me? Moving speakers and LP are the first steps. That huge dip can not be equalized, if you are even considering that. EQ is required in most every room despite what you may hear. But you have to manipulate the response by placement optimization before you even consider trap placement and quantity. If you cannot get the response flatter with placement it would take a lot of trapping to fix this large and broad of a dip. The 57;Hz peak is not a problem, the dip is.
I suspect the issue is the size and shape of the room combined with the openings into the other rooms. This can easily form resonant structures that do this your response.

 

[linearphase]

The file you attached contains only the RIGHT speaker.

The wall behind my chair is kneewall that is just slightly higher than the chair.

How much higher?
Consider remeasuring with the mic about 5ft from the back of the chair.
The right speaker is too close to the right wall,

I see big spikes in the energy time curve (ETC) at 2, 3.6 and 4.5 mS. The last one corresponds roughly to a half wavelength at 100Hz and that is where you have your big dip. Look for an object that would have path distance of 5ft longer than the distance from the woofer to the mic position you used. Could well be the floor or the ceiling or maybe he wall behind the chair or even the back of the chair itself.

The response above 450Hz looks great.

Google "calibrated acoustic string" to see the technique to identify these objects. It is very easy and useful to use.

 

[berthos]

First of all, are you satisfied with your listening experience ? I agree with all the preceeding replies. According to the mesurements, you’ve got nothing after 12 kHz that’s surprising. Maybe due to the microphone. I have no knowledge on rooms acoustic treatment but I am becoming familar with dsp corrections (dirac live on minidsp Ddrc-24 and umik microphone). It is very usefull to heard a kind of really improved flattened response on a small listening area.

 

[linearphase]

The high frequency response of the speaker depends on the type of speaker, more specifically the power response. If the speaker is Omni for example it will have declining high frequency response and still sound fine. I am not familiar with the polar response of this speaker but it looks like the mid/ tweet points towards the ceiling. This is consistent with the decline above 10KHz shown.
At this point in the discussion I do not think this should be of much concern.

 

[DanDan]

Location Location Location. It looks like your room has no treatment at all, except windows, which absorb LF, and record collection and couch, which will do something. The two biggest surfaces in your room are floor and ceiling. Can you treat either?

 

[berthos]

Ok I agree my remark about the 10kHz is inapropriate. I was doing the same measurement on my system comparing a DIY supravox TQWT and my reference Pierre Etienne Léon speakers. With the monitor position with angle 0° to the listening position the response curves show the linearity up to 15 KHz for the TQWT and to 18 kHz for the PEL.
For your measurements, you should try the position left and right from the window. It seems to be the position with best symetry. You should also try several distance from wall. You should also try both 0° and 30° angle. Let us know if the 50 - 500 Hz response is modified.

 

[berthos]

According to the distance between your speakers < 4 meters. A reference article on the monitor position available in tech.ebu.ch/docs/tech/tech3276.pdf