isolation devices (Mechanical energy drain device)

[Buckle-meister]

Error correction algorythms do not cause audible problem until the errors are so huge that they stop the signal path. Anything less is just audio voodoo about its effect on sound so don't worry about it. Worry about room acoustics, not the non issues

(sigh). Alas, I'd love to make inroads with room acoustics, but I currently rent a flat, and doubt the owner would be particularly impressed if I started tacking stuff to the walls.

I never realized until I came to audioholics just how much difference room acoustics might make. What's that quote from a paper; "it's the first thing we start with, and the last thing we consider". I've lived in a few different places now. The Hi-Fi comes with me of course. Each time I move, I hear (to my ears) substantial differences. I'd guess this is almost entirely due to the differently shaped rooms etc.

Interestingly, I believe I already know that I could do with some kind of room acoustics for my present 4m x 4m (yes yes, I know it's the 2nd worst shape there is) room. When I do a frequency sweep, there are two or three points at which the diminishing tone 'swells'.

Would I be correct in saying that these are almost certainly at my room's 'modes'?

Regards

 

[WmAx]

Now, if you reduce that footprint by using our spikes, while the mass would be concentrated on those four points, the transferrence surface would also be reduced...in my mind, I would suspect the frequencies that could be conducted would also be reduced in bandwidth. Additionally, given the fact that we are interrupting that the wood-to-wood conduction by introduction of a dis-similar(an much denser)material(probably brass) that the amplitude of those remaining frequencies would be attenuated to a great extent...

The pressure per area is increased[coupling] by precisely the inverse proportion to reducing the surface area. To de-couple two surfaces that ultimately have to have some sort of contact for support reasons, you have to have one of two conditions: (1) A suspension/spring that has a resonant frequency below the band you want to filter. (2) A high co-efficient of damping[conversion of energy to heat] occuring within the frequency band of interest that essentially kills the motional energy. In practical situation(s), you want a spring suspension that has sufficient damping, otherwise excess oscillation will occur near the resonant frequency.

Re: spikes: it does not matter if the spike is brass, steel or titanium; the spike[a small and dense material with very high stiffness] is going to have a very high resonant frequency above those of interest/importance, therefor it is not going to filter the band(s) of interest. It will also have virtually no loss of energy within the frequency bands of interest, therefor it is also not a useful damping device. A spike is a coupling device. Damping or filtering of the vibrations transimitted through this coupling device will be entirely dependant upon the properties of the object it is coupled to.

-Chris

 

[jaxvon]

Yes indeed, those would be room modes. If you can't opt for bass traps or the like, you might want to try using a parametric EQ. Behringer makes a nice unit (the DCX2496). I'm not sure if the model is the same over on the other side of the pond though.

And lastly, have you seen this article? You might be able to make some traps and stuff that don't require wall mounting, if you are so inclined. You could also just buy some stuff from Real Traps.

 

[Buckle-meister]

Yes indeed, those would be room modes. If you can't opt for bass traps or the like, you might want to try using a parametric EQ. Behringer makes a nice unit (the DCX2496). I'm not sure if the model is the same over on the other side of the pond though.

Is there any reason that an offboard PEQ like the Behringer would be a better option than using the internal bass management PEQ in my Z9? Is the Behringer more comprehensive?

And lastly, have you seen this article? You might be able to make some traps and stuff that don't require wall mounting, if you are so inclined. You could also just buy some stuff from Real Traps.

No, I had not seen it. Thanks for that. I'll certainly give it some thought, but I'm generally quite the minimalist, so, we'll see...

By the way, is there ever a danger that by putting absorbtion up all over the place, a room becomes 'over-damped'?

Regards

 

[jaxvon]

No, your internal PEQ will work just fine. I didn't know what kind of a system you had. The Behringer unit offers more flexibility though.

Yes, you can over-damp a room, making it sound very "dead".

As far as room treatment goes, I would recommend that you at least put some treatment, either diffusion or absorbtion at the primary reflection points of your speakers. You'll need a friend to do this one, or some patience. Sit in your normal listening position and have your friend slide a mirror along each sidewall until you see your speaker in the mirror. That will be where you should place the treatment.

Bass traps can help alleviate room modes, but traps with parametric EQ will do wonders.

 

[WmAx]

As far as room treatment goes, I would recommend that you at least put some treatment, either diffusion or absorbtion at the primary reflection points of your speakers.

As always, I like to caution that this is variable. Given speakers with extremely linear off axis response[think of omnipolar dispersion], and if these speakers are placed at optimal distances from the walls[relative to psychoacoustic delay perception], damping the primary reflections may result in sound degradation so far as realisim of ambience. Of course, in most situations[the example I gve is not typical], at least some absorbtion of the primary points is beneficial.

-Chris

 

[jaxvon]

Good point. Keep that in mind if you decide to buy Ohms, Mirage Omnistats, MBL Radistahllers, or German Physiks speakers.

 

[WmAx]

Is there any reason that an offboard PEQ like the Behringer would be a better option than using the internal bass management PEQ in my Z9? Is the Behringer more comprehensive?

Depends. Is the PEQ in the Z9 a real[discrete control over frequency, bandwidth[Q] and gain of the filters] parametric equalizer? The Behringer, of course, has features/controls that allow for a huge level of control over speaker performance; the DCX2496 is much more than just a simple parametric equalizer.

-Chris

 

[Buckle-meister]

Given speakers with extremely linear off axis response[think of omnipolar dispersion], and if these speakers are placed at optimal distances from the walls[relative to psychoacoustic delay perception]...

Em, sorry WmAx, I know you were only trying to help me, but that's way over my head. My Mission Elegante speakers are very good quality to be sure, but I doubt they are so unique that they are extreme at anything, though I can't say this definitively.

Is the PEQ in the Z9 a real [discrete control over frequency, bandwidth [Q] and gain of the filters] parametric equalizer?.

I believe so, though I'm on shakey ground here a little. The Z9's automatic callibration YPAO, which checks Wiring, Distance, Size, Equalizing and Level:

"incorporates three parameters; Frequency (adjustable in one-third octave increments between 63Hz and 16kHz), Level (adjustable in increments of 0.5dB between –20 and +6dB) and Q factor (adjustable between the values 0.5 and 10) for each of the 10 bands in its parametric equalizer (plus 5 subwoofer bands)."

I think that if using the manual PEQ, I am only able to adjust frequencies and levels between 1.0 and 12.7kHz and -9 and +3dB respectively, i.e I cannot get access/adjust Q-factor. In addition, the Z9 also has a 9-band graphic equalizer to adjust frequncies and levels from 63Hz to 16kHz and +/-6dB respectively. Furthermore, the tone control can be engaged to adjust the 125, 350 and 500Hz frequency bands by +/-6dB.

This is where I really fall down I'm afraid . I just dont know enough about PEQ's or the mechanics of the parameters I'm changing to set them up, though I'd dearly love to, as I find this kind of stuff very interesting (recall all my CD/DVD-A/SACD questions WmAx).

Is it beyond the realms of possibility that I could learn enough to know what I would be doing? Is this kind of thing only for custom installers?, and should I therefore forget about it? Any help would be very much appreciated.

Regards

 

[mtrycrafts]

Em, sorry WmAx, I know you were only trying to help me, but that's way over my head. My Mission Elegante speakers are very good quality to be sure, but I doubt they are so unique that they are extreme at anything, though I can't say this definitively.



I believe so, though I'm on shakey ground here a little. The Z9's automatic callibration YPAO, which checks Wiring, Distance, Size, Equalizing and Level:

"incorporates three parameters; Frequency (adjustable in one-third octave increments between 63Hz and 16kHz), Level (adjustable in increments of 0.5dB between –20 and +6dB) and Q factor (adjustable between the values 0.5 and 10) for each of the 10 bands in its parametric equalizer (plus 5 subwoofer bands)."

I think that if using the manual PEQ, I am only able to adjust frequencies and levels between 1.0 and 12.7kHz and -9 and +3dB respectively, i.e I cannot get access/adjust Q-factor. In addition, the Z9 also has a 9-band graphic equalizer to adjust frequncies and levels from 63Hz to 16kHz and +/-6dB respectively. Furthermore, the tone control can be engaged to adjust the 125, 350 and 500Hz frequency bands by +/-6dB.

This is where I really fall down I'm afraid . I just dont know enough about PEQ's or the mechanics of the parameters I'm changing to set them up, though I'd dearly love to, as I find this kind of stuff very interesting (recall all my CD/DVD-A/SACD questions WmAx).

Is it beyond the realms of possibility that I could learn enough to know what I would be doing? Is this kind of thing only for custom installers?, and should I therefore forget about it? Any help would be very much appreciated.

Regards

Since the direction mentions the Q as having a range, then it looks like that is adjustable as WmAx was asking Maybe that part needs careful adjusting?

 

[WmAx]

Em, sorry WmAx, I know you were only trying to help me, but that's way over my head. My Mission Elegante speakers are very good quality to be sure, but I doubt they are so unique that they are extreme at anything, though I can't say this definitively.

I apologize for the lack of clarity. If you quote a specific statement or term that is not understood, I will elaborate.

"incorporates three parameters; Frequency (adjustable in one-third octave increments between 63Hz and 16kHz), Level (adjustable in increments of 0.5dB between –20 and +6dB) and Q factor (adjustable between the values 0.5 and 10) for each of the 10 bands in its parametric equalizer (plus 5 subwoofer bands)."

1/3 octave increments? If that is true, then I don't think it's a very good parameteric equalizer[due to this coarse resolution]. 1/3 octave from 63 Hz is 84 Hz, for example. What do you do for a peak at 74Hz, for example?

I think that if using the manual PEQ, I am only able to adjust frequencies and levels between 1.0 and 12.7kHz and -9 and +3dB respectively, i.e I cannot get access/adjust Q-factor.

Can't access the Q-factor in manual mode? IMO, the PEQ is not very useful considering the two issues you have brought to attention.

Is it beyond the realms of possibility that I could learn enough to know what I would be doing? Is this kind of thing only for custom installers?, and should I therefore forget about it? Any help would be very much appreciated.

Regards

Really, anyone can manually optimize response using some widely available[and now low cost] tools[SPL meter, test tones and graph paper + parameteric equalizer].

-Chris

 

[Buckle-meister]

Since the direction mentions the Q as having a range, then it looks like that is adjustable as WmAx was asking Maybe that part needs careful adjusting?

I don't understand what you mean?

Regards

 

[Buckle-meister]

I apologize for the lack of clarity. If you quote a specific statement or term that is not understood, I will elaborate.

HaHaHa. Are you kidding? I didn't understand any of the paragraph in question!

1/3 octave increments? If that is true, then I don't think it's a very good parameteric equalizer[due to this coarse resolution]. 1/3 octave from 63 Hz is 84 Hz, for example. What do you do for a peak at 74Hz, for example?

Again, I'm on very shakey ground, but isn't Q-factor to adjust the width of a particular frequency band? If so, wouldn't the Z9 be able to adjust the 74Hz (example frequency) indirectly?

Really, anyone can manually optimize response using some widely available [and now low cost] tools [SPL meter, test tones and graph paper + parameteric equalizer].

Well now, this makes me very happy, because I already have the RadioShack analogue meter and the Rives test disc 2 (calibrated tones to the meter). Graph paper I can easily get (or, I gather, I could just use Excel?).

But what about the parametric equalizer? Albeit may be coarse, do you think I could (temporarily) use my Z9's? And, more importantly, whether I use the Z9's or end up purchasing something like the Behringer, what is it that I am actually going to do? This is what I think I would do; can you correct me/elaborate as necessary please?

1. Using the test tones, measure (calibrated to say 75dB) and plot them in (say) Excel on a graph of SPL (vertical-axis) against Frequency (horizontal axis). This will give me the frequency response of the speaker in question, for my room, at the listening position.

2. Determine the amount of +/- that I need to adjust each band of the parametric equalizer to give as close to a straight line (flat) response as possible on the plot.

Regards

 

[WmAx]

HaHaHa. Are you kidding? I didn't understand any of the paragraph in question!

Okay. I'll quote my original statement and then re-word it to make it more clear.

Wmax stated: "As always, I like to caution that this is variable. Given speakers with extremely linear off axis response[think of omnipolar dispersion], and if these speakers are placed at optimal distances from the walls[relative to psychoacoustic delay perception], damping the primary reflections may result in sound degradation so far as realisim of ambience. Of course, in most situations[the example I gve is not typical], at least some absorbtion of the primary points is beneficial."

Clarified: It is not always optimal to damp/absorb the points of 1st reflection. If you have a speaker, for example, that has full range omnipolar[even frequency response at every horiztonal angle through it's entire bandwidth] speaker, the reflections are beneficial to percieved realism of spatial effects/ambient environment of a(the) recording(s). For the reflections to be beneficial, the speakers need to have a minimum of 5 ms(milliseconds) total delay difference comparing the direct sound of the speaker arrival at your ear and reflected sound arrival at your ear. Optimally approx. 10 ms. Since 1ms equals roughly 1 foot, that means the sound has to travel approx. 1 foot to equal 1ms delay. You need to calculate the elapsed distance from the speaker to reflection point center and then to your head position. Now measure the speaker position from your head. Find the difference. [Example: Speaker is 6' directly in front of you. Wall is 3' from point on speaker where sound is dispersed. Speaker delay: 6 ms(6' in front of you). Reflection delay: 12 ms(3' to wall, 9' from wall to your head). Difference: 6ms between direct sound arrival and reflected sound arrival. Obviously, setting speakers this far from walls may be problematic in many home environments. To easily find the actual difference in your environment, use a mirror to find the points of 1st reflection(have assistant move mirror on front and side walls until you can see speaker in mirror from listening position). Use a tape measure to aquire values of direct arrival and total elapsed distance of reflected sound from 1st point reflections. According to psychoacoustic research, 5ms minimum difference is beneficial to ambience/spatial enhancment. Under this time difference will tend to create degraded sound quality, a muddy sound is probbly appropriate description. 10ms is optimal. However, remember that I mentioned the dispersion characteristics. If the speaker does not have a frequency response at the angle of reflection that closely resembles the on axis/direct frequency response, then the reflection should be damped/absorbed at least partially. Also, in any case, if the speaker can not be spaced from the wall to have an elapsed direct. vs. reflected difference of at least 5ms, it should be damped/absorbed.

Again, I'm on very shakey ground, but isn't Q-factor to adjust the width of a particular frequency band? If so, wouldn't the Z9 be able to adjust the 74Hz (example frequency) indirectly?

Yes, Q adjusts width of the band. This is to account for the width of the peak. If you adjust the width of the band to affect a frequency that is significnatly off of center because the specific center frequency can not be specified with the equalizer, then you will have to affect frequencies besides the one you are attempting to target, as a consequence.

Well now, this makes me very happy, because I already have the RadioShack analogue meter and the Rives test disc 2 (calibrated tones to the meter). Graph paper I can easily get (or, I gather, I could just use Excel?).

Yes, you can use any method you wish for plotting the response.

But what about the parametric equalizer? Albeit may be coarse, do you think I could (temporarily) use my Z9's? And, more importantly, whether I use the Z9's or end up purchasing something like the Behringer, what is it that I am actually going to do? This is what I think I would do; can you correct me/elaborate as necessary please?

The Z9's selectable frequencies may end up aligning very close to the problem bands, if you are lucky. Maybe the auto E.Q. function will work optimally[You must confirm with measurement]? The problem with an outboard equalizer is finding a way to use it on your amplifier. If you only use it on a subwoofer, then it's easy: put in line between the pre-out sub line signal and sub lin input signal. Things may get tricky if you want to use it on the main speakers and subs, unless your reciever has main pre out/in loops on the back or a tape loop function that always works regardless of selected modes.

1. Using the test tones, measure (calibrated to say 75dB) and plot them in (say) Excel on a graph of SPL (vertical-axis) against Frequency (horizontal axis). This will give me the frequency response of the speaker in question, for my room, at the listening position.

Right. I would do this in 1 Hz resolution from 20 Hz to 125 Hz. 2Hz resolution is also sufficient. A wider band of analysis would be desirable, but it will become very tedious, even by 125 Hz.

2. Determine the amount of +/- that I need to adjust each band of the parametric equalizer to give as close to a straight line (flat) response as possible on the plot.

To determine bandwidth[Q] setting, refer to the frequency response peak of interest. Look at the maximum SPL value of the peak(this will be the center frequency). Look to the right and find the point where the peak has reduced by 3dB, this will be the HF 3dB down point. Now look to the left and find the point where the peak is down by 3dB, this will be the LF 3dB down point. Q will be center frequency divided by (HF 3dB down point minus LF 3dB down point).

Example: Center=100Hz, LF 3dB=75, HF 3dB=175.

Q = 100/(175 - 75)
Q = 1.0

-Chris

 

[Buckle-meister]

WmAx,

Thanks for the very indepth description provided.

Can you confirm something for me?

It seems that I can only enjoy the benefits of Yamaha's PEQ; I cannot adjust it's own PEQ measurements made during YPAO setup. If I am to overide this, I must use the GEQ as I described before. To determine which will be the most beneficial (though with Q-factor adjustability, I reckon it'll be YPAO), I need to somehow measure Yamaha's own results. Would this work?:

If I record SPL's with the meter, played through my system with bass management, at the GEQ band positions and plot the results, then I should be able to make a comparison with the settings I would be able to make myself, again from using the meter against the GEQ's bands, but this time with the bass management bypassed.

True?

Regards

 

[WmAx]

Right. You will have to (1) Measure the response in room with no PEQ or GEQ. (2) Measure the response with the automatic PEQ system engaged. (3) Try to correct the problems in no. 1 with the GEQ and then meausre. (4) Compare manual GEQ vs. automatic PEQ results. Pick and use the one that achieved the flattest response.

-Chris

WmAx,


It seems that I can only enjoy the benefits of Yamaha's PEQ; I cannot adjust it's own PEQ measurements made during YPAO setup. If I am to overide this, I must use the GEQ as I described before. To determine which will be the most beneficial (though with Q-factor adjustability, I reckon it'll be YPAO), I need to somehow measure Yamaha's own results. Would this work?:

If I record SPL's with the meter, played through my system with bass management, at the GEQ band positions and plot the results, then I should be able to make a comparison with the settings I would be able to make myself, again from using the meter against the GEQ's bands, but this time with the bass management bypassed.

True?

Regards

 

[Buckle-meister]

Thanks WmAx.

My Z9 is away on a small 'holiday' at the moment , but when it returns, I'll run this test. However, since this thread will almost certainly have dropped off the (very short) end of the thread list, I'll start a new thread in 'Room Acoustics, System Layout & Setup' if I have any further queries.

What are the odds?!

Regards