Please note that if you want to learn how to work with REW (Room EQ Wizard) used in this post, you can get Manual Calibration with REW Guide to help you out!
What is Yamaha YPAO and YPAO R.S.C
If you have a Yamaha Surround Sound Receiver from the last few years, it will most likely have a room calibration system called Yamaha Parametric [Room] Acoustic Optimiser. In simple terms, using a microphone, YPAO will take you through a process to optimise the speakers in your room to ensure you get the best surround sound experience from your receiver. You should use it when you’re setting up your Yamaha receiver for the first time and every time you move your speakers to a new position or new room.
If you’re a beginner to home cinema, you should refer to your receiver’s manual (or read my new article here), go through the YPAO process and stop reading here. At the same time, if you are an advanced reader and want to understand how to get the very best out of your receiver, keep reading. Since there isn’t a lot of information on the internet about YPAO, this article will go into some fairly advanced topics. Please read the basic and intermediate articles on SimpleHomeCinema first if you’re new to home cinema. Our advanced articles will not explain basic terminology.
Please note that not all statements are backed up by measurement graphs, but the article was written after being in email communication with the engineers at Yamaha Japan who designed YPAO (with the help of Yamaha Australia, thank you!) and taking hundreds of measurements and configurations for testing. These may be published at a later time. For the benefit of contributing to the community, the findings are published without wait.
The Difference between YPAO and YPAO R.S.C
Basic YPAO will do the following:
- Measure and set speaker delays (called – inaccurately – distance)
- Measure and set speaker levels / volume
- Measure the frequency response of your speakers and use a parametric equaliser (PEQ) to flatten the frequency response of the speakers/room in the frequency domain only (what it is doing really is match the timbre of the speakers to each other)
YPAO R.S.C (R.S.C. stands for Reflected Sound Control) is more advanced. It actually has TWO sets of filters:
- It will measure the impulse response of the main speakers (not the subwoofer even if the model has sub EQ) AND will create filters that will modulate BOTH the phase and the frequency of the response. This is to allow for removing the first reflection of the speakers in the room and it allows YPAO to tackle both the dips and the peaks in the frequency response. YPAO basic will only be able to tackle the peaks effectively and do a hit or miss with the dips. This is true of any type of parametric EQ. These filters are not actually displayed on the screen and are not editable.
- The second set of filters are only in the frequency-domain with a minimum phase: these are the PEQ filters that are used in the YPAO basic equalisation. But here, more broad filters can be used since the main / most difficult issues in frequency response have been corrected.
This is why manual editing of filters for YPAO and YPAO R.S.C have to be done differently. Let’s have a look…
How to tweak YPAO and YPAO R.S.C manually
So why would you tweak YPAO and YPAO R.S.C.? There are two reasons:
- Even when they have the capability on the higher-end receivers to do subwoofer equalisation, they don’t actually set filters that work in more difficult rooms. Yes, the subwoofer is the most important speaker to equalise.
- YPAO and YPAO R.S.C. don’t always get the filters right. Sometimes a manual calibration will get more precision.
What do you need to manually calibrate YPAO and YPAO R.S.C.?
- A high-quality USB microphone like the UMIK-1 OR if you have a receiver with YPAO R.S.C. the microphone that came with your receiver and a cheap USB sound-card with microphone line input. Please note that I have tested the YPAO R.S.C. microphone against a calibrated UMIK-1 and the microphone is accurate enough to calibrate to 1/6 octave resolution. You should NOT be working with a higher resolution anyway, especially since YPAO can only do about 1/3 octave resolution accurately, which is plenty to get your speakers sounding fantastic.
- REW – Room EQ Wizard. You will need to Google this program and download it from Home Theatre Shack.
- An strong will to learn and succeed if you’re new to equalisation.
How to set up the receiver
All Yamaha receivers give you the option to copy one of the equalisation curves to the manual curve for editing. This may be a good starting point for you. To find out if it is, measure your speakers both with the EQ off and on and see which response is flatter / closer to where you want it to be. Start there.
Alternatively, clear the manual PEQ settings and start from scratch by measuring the response.
IMPORTANT POINT!!! With YPAO R.S.C, when you copy one of the YPAO curves (such as Flat or Natural), the Impulse Response Filters (IRF) will also be copied, even though they are not editable. This means that you need to copy the curve and then MANUALLY set all filters to 0 decibels and measure your speakers that way if you want to start from scratch but still keep the IRF filters.
A proof for this is measuring the manual EQ on with all PEQ filters in the 0dB position and EQ off (called YPAO Through) to see what the IRF filters are doing. You will notice a difference and that is the first layer of filters being applied by YPAO R.S.C. The following diagram illustrates the difference. The centre speaker was measured both with no EQ (pink line) and with the manual setting with all EQ filters set to 0dB and only IRF filters active (darker purple line). You can see that the purple line is smoother especially in the 80Hz to 500Hz where YPAO R.S.C. is most active. Ignore the subwoofer measurements (below 80Hz).
How to equalise your speakers
Mathematically, YPAO’s 1/3 octave resolution is enough to get a flat enough frequency response for all your speakers. This is in spite of the fact that people on the forums like to complain about YPAO not giving us a higher resolution.
Adding YPAO R.S.C to the mix and you have way more resolution AND manual control to get excellent sound rivalling equipment costing 10x as much, if you’re willing to do the work. Here are some charts to prove this from a purely mathematics point of view, and then I’ll tackle reality. Darker purple line is the original response. The pink line is the new predicted response with only 6 filters, all configurable in YPAO.
As you can see on the before and after frequency response curves calculated by REW, you can match the response of all speakers within 2db of the desired curve using only the YPAO PEQs. That is not perfect but pretty close.
Ok, so how does this work in reality? REW’s predictions for cutting filters will be 95% spot on regarding how the PEQ filters will behave. The other 5% is slightly different behaviour OR – in the case of YPAO R.S.C. – an interaction with the Impulse filters. So set the filter, and re-measure.
Peaking or boosting filters will almost always not behave how you expect them to and may even cause audible artefacts. This is because dips in frequency response are most often than not will be due to standing waves, which PEQ cannot correct effectively or if it can, it will only do so for certain listening positions, while produce artefacts for others.
This is why you should equalise using only cutting filters if you can or if you cannot, use careful listening and re-measurement of all listening positions to ensure the filter hasn’t caused artefacts. To be perfectly honest, having played with different PEQ filters with or without impulse filters applied, in 99% of cases narrow Q boosting filters used to tackle sharp dips will produce some kind of artefact that is audible to trained ears. For untrained ears, this may not be so, but it is best to leave them be or lower the rest of the frequency spectrum instead.
There is a lot more to say about YPAO, but this is the take-away:
- YPAO’s resolution is enough to correct frequency response to 2dB to the desired target. It will take time to experiment with the filters, though, to get this right.
- YPAO R.S.C. applies impulse response filters that are not editable but will copy over to the manual setting.
- Use cutting filters only to avoid audible artefacts, especially if you have any critical listeners in the audience. Otherwise re-measure all listening positions.
- Use the subwoofer EQ on the higher-end models to equalise your subwoofer. Again, use only cutting filters here and tackle dips in the response by moving the subwoofer to a more ideal location in the room. PEQ is not there to do that.
Should you have any questions regarding more advanced set-up of your Yamaha receiver, please contact us at Simple Home Cinema. Happy listening!
Please note that a follow-up to this article has been posted here.
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