Room acoustic measurement - something strange with my Yamaha R-N602

nabeshima

Standard Member
Hello everybody,
last week I spent some time with a friend doing some acoustic measurement on my hifi set up to have fun but also check what to improve on the current system.

I had no idea about how the process works till we started but now I am so much into it that I am thinking of buying all I need to run the measurements myself!!

The tools used for the measurement (gently provided by my audiophile friend) were REW software and miniDSP UMIK-1

I will upload the results of the measurement in next couple of days as soon as my friend shares it with me but I wanted to start the thread to seek for some help / suggestion on the type of analysis that should be done on a system.

System
Integrated Amp Yamaha R-N602
Speaker set 1 Q Acoustics 3050i
Speaker set 2 Wharfedale Diamond 9.1
TT Dual 505-2

Measurement Approach
  1. Measurements were made activating and deactivating the Pure Direct function of the Yamaha amp - Pure Direct Means Pure Fidelity
  2. We alternated the speakers set and we combined both set - Yamaha currently support combined speakers
  3. With Pure Direct deactivated we tuned Bass and Treble to try flatten the curve

Result
From the profile of the measurement we saw a strange pattern no matter of the different tests we run
  • a flat-ish response on frequencies between 200-20k Hz
  • drop after around 20k Hz (depending on the speakers)
  • A very weird response within 40-200 Hz with
    • Spike in the low range 40-100 Hz
    • drop around 100Hz
Questions
I was surprised by the similarity of the profiles measured and I started feeling the Amp has its "signature" amplification and that looked not normal: (a) spike on low frequencies followed by a (b) drop around 100Hz and then a (c) stable output thought the speakers' range. What I will try to answer is
  • Is the profile seen normal for the Yamaha R-N602 ?
  • Is there something in the room set up (carpet, furnitures...) that can have such a destabilising impact on the response?
  • Can i measure the output of the AMP without the speakers?
  • How are the speakers performing in the same room with a different amp?
  • How is the Yamaha R-N602 performing in the same room with different speakers

Recommendation received
My friend has recommended a few things to improve the overall the sound:
  1. Add a crossover and a subwoofer to separate the 40-200 Hz frequency
  2. Consider the option of adding a super tweeter to extend the high frequency range

Room

Screenshot 2022-02-17 at 21.02.15.png
 
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Ugg10

Distinguished Member
Anything under 200HZ will be room cancellation/reinforcement and not likely a function of your amp or speakers. 100Hz is a wavelength of 3.4m. There is a room modeller in REW where you can see the dominant frequencies in your room, see if this equates to the peaks/dips you see in your measurements.

You will probably find if you move the microphone position around you will get very different readings. Also for the same mic position you will get different left and right speaker readings if okayed separately.

One method is to take readings of the stereo speakers playing together at a number of positions around the seating position and then use REW to average them, you can then tweak this averaged signal. This is in effect what Dirac / arc / room perfect do in an automated manner. Iirc there are tutorials on the REW site for this.
 
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nabeshima

Standard Member
Anything under 200HZ will be room cancellation/reinforcement and not likely a function of your amp or speakers. 100Hz is a wavelength of 3.4m. There is a room modeller in REW where you can see the dominant frequencies in your room, see if this equates to the peaks/dips you see in your measurements.

Thanks @Ugg10 for the response. It definitely gives me some more confidence but at the same time the room cancellation / reinforcement is something I don't know how to address.

Do you think it is worth to take the measurement in a different room , much smaller than the one I currently use and validate the impact o of the room cancellation / reinforcement?
 

Ugg10

Distinguished Member
To remove the room effects typically you measure the woofers and the port at about 1cm distance (from the centre dust cap and the port entrance) to give you the below 200Hz response, then do the mids and tweeters at around 1m distance but then in REW you need to gate the results to get rid of the room reflection. Typically this is around 4.5ms gating. You can then splice the three together to get a quasi anechoic response for the speakers. The other way is to do the measurement of the speaker outside on a 10ft high platform or using a ground plane method.

Moving to a smaller room is likely to give more reflection than a larger room and will not be representative of the other larger room. The only ways to get rid of bass peaks and nulls is to either move the speakers to positions where they are minimised at the listening position, treat the room with bass traps (not usually very nice looking) or use a DSP to correct them. However, you may find that even though the frequency response may be a bit rough, subjectively they sound OK.
 

nabeshima

Standard Member
The other way is to do the measurement of the speaker outside on a 10ft high platform or using a ground plane method.
Are you referring to this? Loudspeaker Ground - Plane Measurement

It is getting advanced to me but actually I like the idea of going through all of this!
I am not after the perfect sound, but I like the idea of knowing better what I am listing to and improve it. I also want to make sure that if I will invest in upgrading my system I know exactly where to put the money. Could be speakers, could be amp, could be anything that will help reduce the room effects. Only thing I can't really change is the room unless I go for a divorce :):)

or use a DSP to correct them.
This is something I need to understand the meaning. Bare in mind there is a lot I don't know about hifi including DSP (searching on the net right now).

One more question for you is around the mic to use. I assume the software is a good one, should I continue using the miniDSP UMIK-1 ? I am thinking of buying one not to be dependent on my friend otherwise will have to wait a little bit to continue with this exercise
 

Flobs

Active Member
Check your speaker positions, at a guess the bass is seeing the whole 'open plan' and about 7.4m.
make sure your left fronts are not 1.50m from the side wall or 2.40m though that seems unlikely however one of the right fronts might be). Whilst your at it might as well verify that none of your fronts is 1 meter from the 'front wall'.
I really hope this helps after verification and having moved the speakers if necessary retake the measures of course not warranted if the speakers remain in the same place.
Btw what is the floor, wood, carpet, tiles ..., and what are you using between speakers and floor?

All measures are to center of mid and bass drivers

Adding a sub might be enjoyable.
I don't see the point of super tweeters as most people can not hear much above 18kHz (or is it just me and my age?). It might cause you to get tinnitus whilst listening though.

That is open plan at the back isn't it? (if so might be worth considering moving the sofa toward the speakers. Though correct the speaker poistions 1st if required.
 

nabeshima

Standard Member
Will check the exact position in terms of distance and post it later on....

Btw what is the floor, wood, carpet, tiles ..., and what are you using between speakers and floor?
Floor is carpet. The external speakers (Q Acoustic) are floorstanding speakers with metal stand spikes. Internal speakers (Wharfedale) are bookshelf speakers fitting in an Ikea kallax bookcase.

That is open plan at the back isn't it? (if so might be worth considering moving the sofa toward the speakers. Though correct the speaker poistions 1st if required.
Not sure if you mean behind the sofa or the hifi. Behind sofa is a big glass door (with light curtains) while back of the hifi is wall with a tv
 

Flobs

Active Member
Floor is carpet. The external speakers (Q Acoustic) are floorstanding speakers with metal stand spikes. Internal speakers (Wharfedale) are bookshelf speakers fitting in an Ikea kallax bookcase.
That should be fine, I have a tiled floor and get awful reflections if I don't take action.

Not sure if you mean behind the sofa or the hifi. Behind sofa is a big glass door (with light curtains) while back of the hifi is wall with a tv
I mean to the right of the sofa, there's a room with a, blue grey, rectangle in it.
This is where I think the 7.4 or so meters are coming from. If I'm correct your central listening position would be near/close to the 45Hz reinforcement, 90Hz cancellation etc these will be reinforced by misplaced speakers.
If your dividing walls are like mine (plaster board, much like having paper walls) then for bass you'll have to consider the whole 'downstairs' area (a lot of guessing on my part but not uncommon situation).
 

Flobs

Active Member
that's a dining area, not separated by any wall.
Ok, if the walls are paper between the lounge and 'kitchen' the bass see's all that area to the right (i.e lounge, kitchen? and dining room) and needs to be incorporated into any plans and placements. So a measurement from the lounge, left hand, wall to the dining room, right hand, wall would be useful. I've been guessing about 7.5m. This will confirm my guesses or not so far.
 

nabeshima

Standard Member
Ok, if the walls are paper between the lounge and 'kitchen' the bass see's all that area to the right (i.e lounge, kitchen? and dining room) and needs to be incorporated into any plans and placements. So a measurement from the lounge, left hand, wall to the dining room, right hand, wall would be useful. I've been guessing about 7.5m. This will confirm my guesses or not so far.
Uploaded a new floor plan with some additional measures....
Room width measurement (including dining area) is 7.2mt long - you were not that wrong
Speakers distance from wall .9mt left , 1.4mt right
 

Flobs

Active Member
Uploaded a new floor plan with some additional measures....
Room width measurement (including dining area) is 7.2mt long - you were not that wrong
Speakers distance from wall .9mt left , 1.4mt right
From that your speakers aren't at 1/5 or 1/3 and my thinking about the dining space is probably on a tangent to nowhere. I was just wondering what size room the bass might be seeing (having had problems with that myself).
The thing to play with would be distance of your main speakers from the wall behind them or experiment with the bungs for the reflex ports.
I'll wait for you to post the results now.
 

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