Parametric Equalizer

[PENG]

Oh I've already used the YPAO and have set all my speakers to small with the crossover at 80hz. For my fronts I have a pair of Klipsch 28F. The manual says their frequency response is 35hz-24khz. For my sub I have a Klipsch R12SW. It's frequency response is 29hz-120hz. For my center channel I have a Polk T-30. Its frequency response is 38hz.-24khz. For my surrounds I have a pair of Klipsch bookshelf speakers R-15M. Their frequency response is 62hz-24khz.

I still don't understand what a center frequency is.

If I understood P.113 in the Owner's manual correctly, the RX-V681 allows you to copy the parametric equalizer values acquired with "Auto Setup" to the Manual fields for fine adjustment.

So if you ran YPAO (the "Auto Setup") already, following the instructions should give you a good starting point.

 

[TechHDS]

I knew that!

I did ... for subs. A big bump on the FR coming up from 0 Hz = high q = bad.

My mistake was equating Q with width instead of height on an EQ. Maybe the result of a mental coin toss. Maybe I should have gone with the drugs excuse.

Thank you. The only thing that sucks worse than being corrected is being wrong.

EDIT: Good thing you were paying attention today.

Edit 2: The manual is on a download here from Yamaha:

https://usa.yamaha.com/products/audio_visual/av_receivers_amps/rx-v681_u/downloads.html#product-tabs

I completely misinterpreted what is on page 114 by missing a k in 16 kHz and then further compounded the error by wrongly assuming that the next line was related.

Sorry about that.

I knew what you where trying to convey, yeah it was backwards but you where on the right track.

Mike

 

[LoriQ]

You can't adjust one frequency and even if you could, the phase shift would cause terrible problems, which is the reason lower Q filters are used in crossovers. However, higher Q can be used in digital filters but they still cause phase shift- all filters delay the signal and when added, phase cancellations occur.

Equalization is often more about removing energy than adding. The beauty of a parametric EQ is that the center frequency, amplitude and width of the range affected (range is the parameter) can be selected, compared with only choosing which band to use and adjusting its amplitude, which may not be exactly where the change is needed.

https://soundbridge.io/parametric-equalizer-2/

According to this video, you are able to adjust a specific frequency by thinning out the Q

 

[TLS Guy]

According to this video, you are able to adjust a specific frequency by thinning out the Q

Yes, but that comes at a huge price of increased frequency phase shift and that means time shift.

If you are going to use any form of Eq, then it has to be done with great finesse and subtlety.
Equalizers are quality spoilers and the best Eq is no Eq.

 

[TLS Guy]

Audyssey, Dirac etc., use DSPs, they are digital filters. The manually adjustable parametric equalizers are also digital filters.




Audyssey, Dirac etc., use DSPs, they are digital... The manually adjustable parametric equalizers are also digital filters so your remarks about the R/C resonant circuits don't really apply.

Below is an explanation by the Audyssey lab, that's about 8 years ago.

You keep making blanket style negative comments about Audyssey and Room EQ software in general, apparently based on your own experience with your equipment/room using the older version (XT). There are much more capable version Audyssey XT32, Dirac Live, Anthem ARC, Trinnov, RoomPerfect and others that a lot of people found effective and in some cases, have facts on their side.

https://audyssey.zendesk.com/hc/en-us/articles/212347763-MultEQ-vs-other-equalization-methods-

• There are two fundamental differences from every other method available in AV receivers today. The first is that MultEQ is not based on parametric equalization. Parametric equalization relies on a few bands that are centered at certain frequencies. These bands do not provide sufficient resolution to address many room acoustical problems. Also, parametric bands tend to interact so that changes at one frequency have undesirable results at nearby frequencies. Moreover, parametric equalization methods use a particular type of digital filter called Infinite Impulse Response (IIR) that only attempts to correct the magnitude response in the frequency domain. These filters can cause unwanted effects, such as ringing or smearing, in the time domain particularly as the bands get narrower. MultEQ uses Finite Impulse Response (FIR) filters for equalization that use several hundred coefficients to achieve much higher resolution in the frequency domain than parametric bands. Furthermore, by their nature, FIR filters simultaneously provide correction in the frequency and time domains. FIR filters had been considered to require too many computational resources. But Audyssey solved this problem by using a special frequency scale that allocates more power to the lower frequencies where it is needed the most.
  The second major difference is that MultEQ combines multiple measurements to create equalization filters that better represent the acoustical problems in the room. Most other methods only perform a single point measurement and this can result in making other locations in the room sound worse than before equalization. There are some methods that use spatial averaging to combine multiple room measurements. Although this is a step above single-point correction, it does not provide optimum correction when discussing spatial averaging. For example, it is common to find a peak at a certain frequency in one location and a dip at the same frequency at another nearby location. The averaging methods will add the peak and the dip and this will result in an apparent flat response at that frequency, thus causing the equalization filter to take no action. MultEQ uses a clustering method to combine measurements so that acoustical problems are better represented, thus allowing the equalization filter to perform the appropriate correction at each location.

It did not say it was based on parametric Eq.

Analog Eq, introduces phase shift by employing an RC network. Digital Eq of ALL stripes does it by digital delay lines. Whilst analog is referred to as phase shift and digital Eq as time shift, the end result is the same. Time and phase shift are one and the same with an identical end result.

I know Audyssey is introducing time phase/shift. All versions would have to.

How to I know. Well my speakers have minimal phase shift. I also used an intensity difference, phase coherent technique for the many recordings made for radio broadcast rather then the ubiquitous phase and therefor time difference techniques. I did not use Eq of any type.

Now the algorithms that produce 7 channel from 2 channel and I'm specifically referencing Dolby P LIIx work by using the phase differences of direct and indirect sound. It actually works much better than you think.

Now these recordings when played back with PL IIx are really as good as discrete recordings. The surround and rear backs just produce the ambiance, but when the applause comes the bulk if the sound then comes from the surrounds and rear backs.

The effect is realistic with a fair reconstruction of the original acoustic space.

Now when you switch to the stored Audyssey settings it is virtually identical to seven channel stereo, The effect is ruined. I'm certain this has occurred because Audyssey has destroyed the carefully preserved phase relationships in the original recordings.

It is just not my recordings either. With Audyssey engaged the reproduction is markedly downgraded. This is especially true of the wonderful BBC broadcasts from the Proms from RAH. These have been fantastic these last few years.

Now I grant you most sources played are highly processed and already awash in massive trespasses in phase and therefore time, in which case the effect may be different. However because these recordings are awash in phase shift, especially from the use of multiple microphones, the addition of the phase/time shift of equalizers can make these time/phase shifts even more glaringly apparent. This effect of equalizers of all stripes has been known to recording and mix engineers for years. It is a major reason why highly processed music sounds so bad.

However on the bulk of the program I listen this is not the case. The whole approach to the recording of classical music is totally different from that in the pop domain.

If you are a lover of classical music with a large number of finely captured recordings, then my advice stands to avoid Audyssey and all others like the plague, no matter what the version.

 

[highfigh]

According to this video, you are able to adjust a specific frequency by thinning out the Q

You can't select only one frequency with an analog equalizer, but the slope of the band can be made very steep- just not without adding problems. There are no acoustical phenomena that occur at only one frequency, but feedback occurs over a very narrow range (being a couple of Hz away in the mid and high frequency ranges is close enough to excite the feedback event)- this is the reason for making the slope exceptionally steep. In most other installations, it's not needed. If the location is for public, mixed use, there's not a great reason for exacting treatment of the acoustics because it may end up being good for one use and bad for others. In some cases, like the school gym where I'm doing an upgrade of the audio system, the space has its original Luan plywood pegboard over fiberglass insulation, but the walls and floor are still very reflective with the exception of the front, which is where the stage is located an it has a heavy curtain. Still, it's not as bad as one would think when it's empty. Once it's filled with people, much of the sound coming from the in-ceiling speakers will be absorbed but it will never be a good-sounding venue unless they treat the back and side walls.

 

[TLS Guy]

You can't select only one frequency with an analog equalizer, but the slope of the band can be made very steep- just not without adding problems. There are no acoustical phenomena that occur at only one frequency, but feedback occurs over a very narrow range (being a couple of Hz away in the mid and high frequency ranges is close enough to excite the feedback event)- this is the reason for making the slope exceptionally steep. In most other installations, it's not needed. If the location is for public, mixed use, there's not a great reason for exacting treatment of the acoustics because it may end up being good for one use and bad for others. In some cases, like the school gym where I'm doing an upgrade of the audio system, the space has its original Luan plywood pegboard over fiberglass insulation, but the walls and floor are still very reflective with the exception of the front, which is where the stage is located an it has a heavy curtain. Still, it's not as bad as one would think when it's empty. Once it's filled with people, much of the sound coming from the in-ceiling speakers will be absorbed but it will never be a good-sounding venue unless they treat the back and side walls.

Yes, feedback control is the best use of parametric Eq. That is widely used in PA systems.

There is however a much better way to control acoustic feedback in PA systems, that at least in North America is rarely used or even known about and that is 1 to 5 Hz frequency shift.

This was a technique developed by the BBC in the sixties, using of all things tubes.

The frequency shifters,which are now analog solid state devices have been made by Surrey Electronics in the UK since the seventies. I still have one, that I used extensively from that time and ALWAYS included one in my PA installations. The one I have is still in production.

This is the one I have.

They also make rack mounted balanced units.

The fixed frequency shift is not audible, but highly effective in killing feedback and increasing forward gain. It is also far easier for inexperienced people to use.

I have never run into a person in North America who uses, or even knows about this highly effective technique. As far as I'm concerned a unit like the above should be part of the basics of any PA system, but over here never is. To me that is really strange.

 

[PENG]

Analog Eq, introduces phase shift by employing an RC network. Digital Eq of ALL stripes does it by digital delay lines. Whilst analog is referred to as phase shift and digital Eq as time shift, the end result is the same. Time and phase shift are one and the same with an identical end result.

You are missing the point, that doing it digitally do not have the inherent difficulties that the analog filter designers have to face. Try solving an analog design issue or optimization that requires Laplace and Fourier transforms!! Using computer programs, you don't have to be an EE or mathematician to do it well. You obviously have electrical/electronics knowledge so you should know that full well, so sorry about stating the obvious.

I know Audyssey is introducing time phase/shift. All versions would have to.

Of course, and they seemed proud doing it in the time domain. Audyssey, and I am sure Dirac, Trinnov and others all play in the time domain, one can assume some do it better than others, but the top sellers all do, except I am not sure YPAO, only because they refer it as PEQ so I do not know that for sure.

How to I know. Well my speakers have minimal phase shift. I also used an intensity difference, phase coherent technique for the many recordings made for radio broadcast rather then the ubiquitous phase and therefor time difference techniques. I did not use Eq of any type.

Let's be fair, you know what you do, but I doubt you know what Audyssey, Dirac Live, Anthem ARC do, and they all seem to be very protective (rightfully..) of their proprietary stuff. No offence, I do have faith in the NA Ph.D programs, as I do in the medical programs, at least those who subsequently worked in their field of expertise in both related industries and reputable universities.

Now the algorithms that produce 7 channel from 2 channel and I'm specifically referencing Dolby P LIIx work by using the phase differences of direct and indirect sound. It actually works much better than you think.

You should know by now that if it is something I "think", or opine, I usually would say so, otherwise it is not what I "think", and I have not said anything about DPLIIx.

Now these recordings when played back with PL IIx are really as good as discrete recordings. The surround and rear backs just produce the ambiance, but when the applause comes the bulk if the sound then comes from the surrounds and rear backs. The effect is realistic with a fair reconstruction of the original acoustic space.

I assume you are just stating your opinion based on your own experience that may or may not be mostly subjective. Incidentally I like DPLIIx too, but I am not sure if I'v lost sleep over losing it to DSU, even though I don't have any height speakers yet.

Now when you switch to the stored Audyssey settings it is virtually identical to seven channel stereo, The effect is ruined. I'm certain this has occurred because Audyssey has destroyed the carefully preserved phase relationships in the original recordings.

Audyssey never stated they even touched the phase in the higher frequencies, and you can limit its effects to the subwoofer only, or with the App you can set the upper limit too. Also, I have plots to show their effects on phase shift for the lower range, no evidence of your claim, that you are so "certain" about.

It is just not my recordings either. With Audyssey engaged the reproduction is markedly downgraded.

Totally subjective, and highly dependent on how you set things up.

If you are a lover of classical music with a large number of finely captured recordings,

I am a lover of classical music. I also know Audyssey is far from being a perfect solution. I fully agree it cannot(no REQ can, I would think..)make bad speakers sound good, or make less accurate speakers more accurate in most rooms.

then my advice stands to avoid Audyssey and all others like the plague, no matter what the version.

Again, I do not think Audyssey (and others) is perfect, far from it. For one thing, I know in my room(s),after each Audyssey run, I have to manually set the crossovers to order to get the best looking FR graphs. For example, the difference between XO60 and XO80 for my FR and FL are very significant if plotted with FR+FL and subs on, or all 7 channels+subs on, yet with the FR+FL or subs only they all look good. As I mention, I really like your idea of variable/user adjustable crossover slope as I "think" that is at least one reason why Audysessy could not do better in integrating highly bass capable speakers with the subwoofers. Audyssey claimed XT32 has the resolution to integrate, even for the "large" setting, but I know it is not the case for my setup in my room. I do give them the benefits of doubt, that they don't have control of the "slopes", but this is just my opinion, and I do believe it could also be one of the reasons why there are no consistent views on the effects of REQ in their rooms. It may also be true that not everyone would prefer more accurate bass response. Dr. Toole obviosuly thought most people do prefer more accurate response but I suspect he would also agree that may not be the case if we focus on the lower range say 20 to 120 Hz for example.

It seems to me you are really just stating your subjective view (not necessarily facts), and one that seems somewhat extreme. I wouldn't "advice" anyone, but would suggest that people be open minded, research the topic while paying less attention to subjective views, and then try what they have and paid for. If Audyssey, YPAO, or whatever, offer no improvements, then try the bypass option, or turn it off completely.

 

[TLS Guy]

You are missing the point, that doing it digitally do not have the inherent difficulties that the analog filter designers have to face. Try solving an analog design issue or optimization that requires Laplace and Fourier transforms!! Using computer programs, you don't have to be an EE or mathematician to do it well. You obviously have electrical/electronics knowledge so you should know that full well, so sorry about stating the obvious.



Of course, and they seemed proud doing it in the time domain. Audyssey, and I am sure Dirac, Trinnov and others all play in the time domain, one can assume some do it better than others, but the top sellers all do, except I am not sure YPAO, only because they refer it as PEQ so I do not know that for sure.



Let's be fair, you know what you do, but I doubt you know what Audyssey, Dirac Live, Anthem ARC do, and they all seem to be very protective (rightfully..) of their proprietary stuff. No offence, I do have faith in the NA Ph.D programs, as I do in the medical programs, at least those who subsequently worked in their field of expertise in both related industries and reputable universities.



You should know by now that if it is something I "think", or opine, I usually would say so, otherwise it is not what I "think", and I have not said anything about DPLIIx.



I assume you are just stating your opinion based on your own experience that may or may not be mostly subjective. Incidentally I like DPLIIx too, but I am not sure if I'v lost sleep over losing it to DSU, even though I don't have any height speakers yet.



Audyssey never stated they even touched the phase in the higher frequencies, and you can limit its effects to the subwoofer only, or with the App you can set the upper limit too. Also, I have plots to show their effects on phase shift for the lower range, no evidence of your claim, that you are so "certain" about.



Totally subjective, and highly dependent on how you set things up.



I am a lover of classical music. I also know Audyssey is far from being a perfect solution. I fully agree it cannot(no REQ can, I would think..)make bad speakers sound good, or make less accurate speakers more accurate in most rooms.



Again, I do not think Audyssey (and others) is perfect, far from it. For one thing, I know in my room(s),after each Audyssey run, I have to manually set the crossovers to order to get the best looking FR graphs. For example, the difference between XO60 and XO80 for my FR and FL are very significant if plotted with FR+FL and subs on, or all 7 channels+subs on, yet with the FR+FL or subs only they all look good. As I mention, I really like your idea of variable/user adjustable crossover slope as I "think" that is at least one reason why Audysessy could not do better in integrating highly bass capable speakers with the subwoofers. Audyssey claimed XT32 has the resolution to integrate, even for the "large" setting, but I know it is not the case for my setup in my room. I do give them the benefits of doubt, that they don't have control of the "slopes", but this is just my opinion, and I do believe it could also be one of the reasons why there are no consistent views on the effects of REQ in their rooms. It may also be true that not everyone would prefer more accurate bass response. Dr. Toole obviosuly thought most people do prefer more accurate response but I suspect he would also agree that may not be the case if we focus on the lower range say 20 to 120 Hz for example.

It seems to me you are really just stating your subjective view (not necessarily facts), and one that seems somewhat extreme. I wouldn't "advice" anyone, but would suggest that people be open minded, research the topic while paying less attention to subjective views, and then try what they have and paid for. If Audyssey, YPAO, or whatever, offer no improvements, then try the bypass option, or turn it off completely.

You have missed the point. Time and phase are different words for the same thing. They are interchangeable. When you shift one you shift the other.

I do not use height speakers. This system is 7.1 and will stay that way.

 

[PENG]

You have missed the point. Time and phase are different words for the same thing. They are interchangeable. When you shift one you shift the other.

I do not use height speakers. This system is 7.1 and will stay that way.

I suggest you read more and try to understand what people wrote.... For example, I didn't say anything about time/phase being different, or not..

The thread is about PEQ so may be time to be back on topic. We can always agree on what we can agree..

 

[highfigh]

Yes, feedback control is the best use of parametric Eq. That is widely used in PA systems.

There is however a much better way to control acoustic feedback in PA systems, that at least in North America is rarely used or even known about and that is 1 to 5 Hz frequency shift.

This was a technique developed by the BBC in the sixties, using of all things tubes.

The frequency shifters,which are now analog solid state devices have been made by Surrey Electronics in the UK since the seventies. I still have one, that I used extensively from that time and ALWAYS included one in my PA installations. The one I have is still in production.

This is the one I have.

They also make rack mounted balanced units.

The fixed frequency shift is not audible, but highly effective in killing feedback and increasing forward gain. It is also far easier for inexperienced people to use.

I have never run into a person in North America who uses, or even knows about this highly effective technique. As far as I'm concerned a unit like the above should be part of the basics of any PA system, but over here never is. To me that is really
strange.

It makes sense to address feedback in this way- it removes the problem without creating a total cancellation at that frequency. I used a Behringer equalizer in a bar, partially because it has what they call a 'feedback destroyer' and I never heard it feed back, nor did they ever complain about it. When the bar changed ownership, I bought most of the system and used it for the fitness facility where I installed the audio system- they use headset mics and roam around the rooms, with in-ceiling speakers and the sub on a side wall, so it was important to eliminate the problem. I may add something to the school gym I'm working on, but with the DSP in the amplifier, I don't think I'll need to- when I tested the mic, I only heard one note of feedback but that was without the sub.