Comparison of small room acoustic models for home listening spaces - Page 12

http://www.parts-express.com/pe/show...number=390-801

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http://www.bhphotovideo.com/c/produc..._Dual_Pre.html

+ some monoprice cables + a cheap/used mic stand off craigslist

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http://www.hometheatershack.com/roomeq/

Understatement of the year .

It should be abundantly clear to all by now, that neither of you can show a single measurement of a single living room/basement/HT room turned into a control room/studio for "critical listening", taken by either of you, including your own. Pure vaporware.

vaporware? lol it's not a "product" like how he references harman for his speaker company's business model. it's managing the specular energy with respect to time. that's all it really boils down to. he's simply restricted to the flatland that is the frequency-domain, so i don't fault him too much.

it's also comical he continues to refer to this as the "padded cell", when the ideal concept one provides is to use reflection/redirection (splayed walls) to attenuate the high-gain early reflections - minimizing the broadband absorption within the room.

speaking of which, has he been able to provide meaningful 3space volumetric power response measurements for his speakers yet?? "let alone meaningful measures showing the speakers actual interaction with boundaries in various spatial loading configurations sufficient for users to actually judge the response when not suspended in free space in an assumed anechoic chamber" ?/

Yes. An example of your small room turned "critical listening" room/control/studio model. RFZ/LEDE whatever. Your room. Your measurements.
Not talk about hypotheticals. Real, in room measurements/why/how/where.

Ah, learning from the master Red Herring maker amirm eh?
Sure, I'll play - Nope, these aren't for control room/studios. They are for living rooms. So just like Revel, Infinity or Paradigm et al, no 3space studio/control room measurements.
But perhaps you could show yours. Wall mount Studio JBLs right? Nice!
Not even a photo eh?
Hmmm...I wonder why...

cheers,

AJ

You will notice my comment about that room is specifically the look of it, not the implementation cost. But yes, for those of us who are not particularly interested in hanging hand-cut extruded styrofoam in our rooms due to aesthetics (not to mention the fire hazard/health hazard if they ever caught fire! EPS gives off seriously toxic fumes if it catches fire), buying that many pre-made diffusers would be a pretty penny indeed.



What part of my year-long build thread, including *excavating my basement* solely to build tiered seating in my home theater, suggests to you I'm not interesting in putting in the effort? Or that I'm not currently doing so?

At this point I'm strongly considering 1D diffusion (made of wood, not styrofoam) across the back wall of my room. Don't know yet if I will build it because it has implications for my window covers, my minibar, and my equipment rack. I need to think it over some more. Audio quality is not the overriding concern in my room.

And considerable may be a considerable understatement! Again this cuts to the very heart of my RFZ measurement examples query - if there's not a single example of someone who has succeeded in replicating the theory as a DIY exercise, then what chance do you or I have? (insert snide comment from dragonfyr here)

I'm willing to go fishing, but only if someone has first demonstrated there's fish to be found.

Later today I will have some time to measure my room. The I will see what my treatments have accomplished. To recap, I have SSC traps behind my false-/screen-wall (installation documented here)and the entire space then lined with 2" Linacoustic. Front 6' or so of wall covered with black carpet floor to ceiling for light control, and same carpet but in a blue up to seated ear level. First reflection points on front ceiling, left and right front and rear wall have 2" OC SelectSound.

My ears tell me I have over-dampened the room. The decay measurements seemed to show not even 200ms. On top of that, I will be adding more traps in the rear, so replacing at least the rear ... and maybe all in-room first reflection .. absorbers with diffusors is something I need to look at.

Measurements later, then the "analysis" can begin.

i've already showed you Nord's room but it doesn't seem to meet your full criteria because the diffuse decay isn't high enough (and i already outlined many days ago that he is still working on it - the 2D diffusers function as absorbers and really attenuate the returns - hence why 1Ds are preferred for such a scenario).

that's like asking to see if someone achieved a "20-20khz flat response" and then invalidating the entire room because it is only +/- 5dB flat and not +/- 3dB.


then why are you the noisiest signal in this thread?

and if you have the room and seating distance location, you can use a diffractal (nested diffuser) to get a lower design frequency and thus higher gain (lower freq) diffused returns.



just a little extra woodworking...

I was doing some searching, but failed Can you explain nature of the relationship between "lower design frequency" and "higher gain?" Why (or how) does one lead to the other? A link would be fine if an explanation is too technical and long - Thanks!

lower frequencies contain inherently more energy content. there has been measured some useful scattering an octave below the design frequency of the schroeder reflection phase grating diffuser, but larger wavelengths will simply see a flat wall. making the diffuser large with respect to lower wavelengths will spatially disperse and diffuse those wavelengths.

diffractals are like multi-way speakers in a sense...

although respect must still be paid to minimum seating distance. so there are room size constraints there as well no free lunches in acoustics rarely

they can be used in smaller sized diffusers to get good diffusion coefficient in the higher freuencies (which otherwise wouldnt be possible in a non-nested diffuser due to viscous losses of such very thin wells)


or can be used to lower the design frequency (see ceiling of blackbird C which will diffuse to 50hz iirc - the 2D PRDs form a larger 2D PRD) - 7ft deep diffuser

So, when you say "higher gain diffused returns" you mean that the diffused return is higher gain than it would be with a simple diffuser? And that's because of the additional low frequency energy included in the diffused return?
Thanks for taking the time.

Did you have a point that is on the topic of this thread?

you asking me?

If so then yes. The thread is asking for help etc etc (without going waay back to find the exact wording) about treating a room. It has gotten heated many times for various reasons, one of those being that we have an opinionated person who has nothing to contribute to the topic of the thread.


I wonder why he is allowed to continually derail thread after thread? And wonder why (if it is me you addressed your question to) you question me and not him? What has he contributed to the topic of the thread in your opinion?

I am interested in learning more in this area, which is why I am following it. It would be good sometimes on this forum to simply be able to let a thread run of it's own course and follow it's own path. If someone is not interested in the topic at hand are they unable to stay out of it?

Whatever nuggest of good info is now buried under mountains of crap. Because too many allow these sorts of distractions to go uncommented upon.

The minute someone (like localhost as well) point it out it is they that get questioned on this topic?

So please, yes, show us your mesaurements, am looking forward to them very much. And when you do, I hope that they can be accepted and analysed within the context of the topic at hand, not have them sniped at by an opionated know nothing who has never taken the time nor effort to do the slightest thing in this area.

No - to my eye there is *zero* gain in the diffuse decay relative relative to the ISD gap. It's not like there is some and I would like to see more. To use your analogy, it's like if I asked for a graph showing flat 20-20khz and you pointed me to one that only showed 500Hz-15kHz. Thats great, but its not what I asked for. I will certainly continue to follow the thread in question to see if he is able to get the results I'm looking for.



It is not I who has a littered trail on this forum of hyperventilating against nearly anyone and everyone. If that is not Noise I don't know what is....

It is true your signal level is high but your SNR is shockingly low, and it does you no favors.

Now, to ask a relevant question instead of just more bickering - I'm wondering about the effectiveness of diffusion on the back wall in spots where the back row of seating is effectively blocking the direct line of sight from the front row seating position to the diffusors in question (or indeed in cases where the seating has a high back which would impede that same path).

My assumption is that, by the very nature of the diffusors, this would be a minor effect, since the goal is to spray that sound back at you off of other walls anyways? But perhaps I am mistaken.

Along that same line of thinking, is it worthwhile to place 1D (horizontal) diffusors very low or very high on the wall, or should they be mostly centered around ear level?

To Localhost127. In the pic of that room in post 349, what do you suspect the hardwood floor and the mixing board is doing to the sound? Also, is there a actual patern to the difusers or is it totally random?

in what sense? the board generally serves the dual purpose of also blocking the floor reflection, as the speakers are placed many feet in front of the board to eliminate working surface reflection (also while you'll see the boards angled downwards slightly).

if you notice in Non-Environmental room there is still reflective floor and front wall - even though the speaker-listener response is entirely anechoic.


RPG diffusers like in the photo are usually of the primitive root or quadratic residue number theory (PRD/QRD respectively). PRDs in the case of that room (the RSA encryption fans will understand)

if you're interested, QRDude (software for QRDs) has an absolutely wonderful technical guide that's easily digestible for the novice -
http://www.subwoofer-builder.com/qrd.htm

Yes, there is a mathematical pattern to the quadratic diffusors. They are Not random. The pattern is designed to achieve a flat power response.

The diffusors pictured with Bob Ludwig are QRD (quadratic residue) diffusors, the QRD diffusors pictured above those in Blackbird are a modified QRD known as a 'diffractal' - nested QRD units effectively covering an enhanced frequency range, while the diffusors which are effective down to ~110 Hz used in Blackbird Studio (that look like lots of sticks) are PRD (primitive root) diffusors. Both are mathematically based.

And as local has suggested, the technical tutorial afforded in QRDude is first rate and Highly recommended.

The mixing board is positioned relative to the speakers such that reflections are minimized and those that exist are redirected AWAY from the listening position. This is a fundamental design element.

Reflections from the floor are controlled both by the controlled dispersion/Q and mounting of the speakers, and also by virtue that the board can, in a studio, be used to block and/or redirect such energy (either by absorption at the expense of energy lost, or by redirection to preserve the energy).

I have a diffusion question.
I've read many times where diffusing, as opposed go absorbing, helps to preserve "precious" energy.

I understand that the overall level / power response will be lower through absorption. But what I'm wondering is why it's precious?

Is it in terms of how a loss of energy means one will have to turn up amps more (which may require other amps/speakers) to attain the desired level?

I have certainly experienced that, after adding FRP absorption panels. But in my case, I have no headroom (need better speakers). For others with headroom to spare, I imagine they can afford the energy loss.

I didn't get into the theater yesterday, but should have time today. I did manage to attach RCA phono interconnects to the L, C and R analog bypass inputs and install the latest REW on my laptop. So I should have data later today.

With respect to members being off-topic and disruptive, the recommended course of action is to report the posts to the mods/admins. That is way for them to be commented upon.

Jeff

kromcamp, with three speakers arrayed across the front, would not the area that is "in the shadow" of one head for one speaker not be lit up by the other two speakers? How big are your heads?

Jeff

Hmmm. I have never used the term "precious". "Finite". "limited", certainly, but never "precious".

But the energy is finite. It means that for a given response, the amount of non-direct specular energy available to bounce about the room and to later return to the listening position is finite.

What is absorbed is effectively lost to the system, (and assuming a perfectly resistive surface and ignoring air resistance), that which is redirected is preserved, and that which is diffused is reduced due to the large degree of loss imposed by diffractive losses and superposition.

Thus if a later well behaved laterally arriving exponentially decaying semi-diffuse soundfield is a goal, then ALL (as in as much as possible) of the available energy must be preserved so that it may be returned to the listening position.

And this has nothing to do with amplifiers. This is the case for ANY given gain level of the direct energy. If you want to turn the gain up so that the direct signal is 130 dB continuous so that the gain of the gain of the indirect returned energy is proportionally a bit greater, that is your choice (and not one I recommend), but it makes little difference to the relative levels between the direct and indirect energy.

The fact is a room is filled with a MYRIAD sources featuring an acoustical impedance that are not completely resistive and which therefore add to energy loss, and diffusion is simply one rather inefficient (lossy) method to provide this energy return in the more diffuse manner desired.

no - it was about using geometric reflective surfaces to attenuate (redirect) early high-gain indirect signals instead of broadband absorption ... where the specular energy can be redirected away from the listening position towards the rear wall diffusers (effectively managing the specular energy within the space and utilizing it appropriately). broadband absorption is soaking up the finite amount of sonic specular energy within the room. diffusers are in themselves absorbers as well...

think about the size of the head/body and how larger wavelengths will diffract around...

simplifying ... sit in the near-field of your speakers and hold up the palm of your hand to block the speaker. some HF energy will be blocked while larger wavelengths will still make it to your ears

Lol, right on!

Take this a few steps further, there is no unified shadow.
Each source's direction of incidence is different, and so the location/orientation of what small high frequency 'shadow' that does result.
Now factor in all of the either indirect signals that are incident and that issue becomes a very small factor indeed.


And is now a good time to ask why the "multi-quote " function does nothing of the sort?????

Yeah I was thinking that'd be a lot better than my trying to analyze the center using Dolby PL II Music mode like I was doing.

Yesterday I connected the center to stereo left and disabled the others, but then I saw how the left channel's mcacc eq was of course applied.