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Audio in 2015 - a summary of trends


Kvalsvoll

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Thanks for the tip!  Between BruteFIR and the Windows convolver program, I will have a good starting point, code-wise.

 

For the build, I plan to go all-out and use the faster quad core Intel Haswell CPU that I can get for the TDP limit I opt to go with, probably 65 W or so.  I'm looking at putting it in this chassis, installing a half-height AVB bridging PCI-E Ethernet card, and running a real-time variant of Linux.  I'm not sure how much CPU power I need, but I basically want to do matrix FIR processing.  In other words, each input channel can feed into all the different output channels with different filters.  If that box doesn't provide enough CPU, I can just add another one because the beauty of AVB Ethernet is that it is very scalable.  For DAC/ADC, I'm looking at using this.  It's got 16 balanced analog ins and outs at up to 8V, Ethernet AVB, a compact footprint, and a killer price tag.  I am too lazy to dig up the link, but I saw some line measurements suggesting almost no bottom end roll-off.  This combination will make my current MiniDSP stuff look like children's toys.

sounds like a fun project :)

 

I know @mojave uses a motu 1248 and I believe their new range is DC coupled, he's probably a good person to talk to about that range. I have heard of some limitations with ethernet based devices regarding inability to handle automated sample rate switching, this was regarding rednet and dante though so not sure if the motu avb range is similarly afflicted. 

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I heard you mention you were doing a new speaker build.  Do you have a separate build thread somewhere?

...

 

This is the work of my company Kvålsvoll Design AS, so there will be no build thread, and I don't think it is appropriate to use this forum to promote what is planned to be commercial products, so no description either.

(None of these will ever enter the u.s. market, unless I move all my operations over, which actually may not be a bad idea, considering the difficulties of building a business in my country..)

 

I contribute here on data-bass to entertain myself, debunk some of the myths, and I hope some of what I write helps to increase awareness for good sound, and there is always something to learn from other.

 

It is important to show people what good sound means.

Currently we have a very unfortunate trend for sound - less people buy, less people bother to participate on forums, more and more people laugh at the whole audio thing because marketing from branding companies focus on nonsense and does not provide a sound experience that really matches the price tag.

Current trends on media production does not help.

 

If the general consensus is "everything sounds the same", "you can't reproduce like live anyway", "my cheap system sounds just as good" - then there will be no market for my products, because there is simply no interest in using resources on good sound.

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sounds like a fun project :)

 

I know @mojave uses a motu 1248 and I believe their new range is DC coupled, he's probably a good person to talk to about that range. I have heard of some limitations with ethernet based devices regarding inability to handle automated sample rate switching, this was regarding rednet and dante though so not sure if the motu avb range is similarly afflicted. 

It will definitely be a learning experience for me, but I believe the technology has huge potential.

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This is the work of my company Kvålsvoll Design AS, so there will be no build thread, and I don't think it is appropriate to use this forum to promote what is planned to be commercial products, so no description either.

(None of these will ever enter the u.s. market, unless I move all my operations over, which actually may not be a bad idea, considering the difficulties of building a business in my country..)

Come to the usa my friend. i will be your first customer.  :)

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Come to the usa my friend. i will be your first customer.   :)

 

Well, I believe you already have a decent setup, like most of the people on here.

 

One more thing I see when reading the posts with computer processing and all the flexibility and possibilities.

Didn't have that in the old days, now it is possible to do advanced signal processing and get proper time alignment and crossover and eq for large systems, including horns.

Requires some work and knowledge, but that is what the hobby is for.

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I will use this thread to post about articles and updates that may or may not be of interest from now on, no need to create a new thread each time I have something on my mind.

 

I am now working on a major update on the "How to set-up a home theater sound system" - more pictures, better pictures, updated content.

 

I intend to add 2 small sections on "Sound quality" and "Sound character".

Only a couple of lines on each subject.

Thing is, all discussion on these subjects tend to become obsolete when the basics are in place - the pure technical performance - frequency response, decay, reflections, directivity pattern, capacity.

Perhaps YOU have some thoughts on this?

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I intend to add 2 small sections on "Sound quality" and "Sound character".

Only a couple of lines on each subject.

Thing is, all discussion on these subjects tend to become obsolete when the basics are in place - the pure technical performance - frequency response, decay, reflections, directivity pattern, capacity.

Perhaps YOU have some thoughts on this?

This should be quite interesting.  While in principle, it's possible to specify ideal parameters for each of these, a real-life system will inevitably involve compromises somewhere, even with "cost no object".  This is especially true with regard to room acoustics.  The hard part is deciding which combination of compromises is preferable, and I think there's a lot of unknown territory here.

 

To elaborate on the subject of room acoustics, it's not enough to merely talk about the items you mentioned.  This is especially the case in small rooms where reflections are rarely diffuse enough to be considered "reverberant" in a statistical sense.  I believe a full understanding of the quality and character of the sound depends on the full impulse response, not just in a single location but in a region surrounding the head.  And even that's not enough.  While we may debate whether or not particle velocity is relevant for perception of low frequencies, it is well established that particle velocity matters substantially in the upper mid range where the ear is most sensitive and where most of the "information content" of sounds reside.

 

(Shameless plug for use of diffusers in room treatment follows.)

 

As a case in point, by adding or removing diffusers at key locations in my room, the impulse response measurements barely change at all, but the

subjective change in the sound is dramatic, especially if there is any reverb (natural or artificial) in the content.  Listening with the diffusers in place is far more pleasurable than without as they make upper mid and high frequencies much easier to resolve while reducing their harshness.  Let's just say you'll have to pry these diffusers out of my cold dead hands!  On the flip side, their use has also revealed deficiencies in my current speakers that were not previously audible, so I'm now in the process of designing replacements.  As for why the impulse response measurements reveal so little change, I suspect that part of it is that the diffuse energy is harder to see in the IR without using a different sort of analysis than is available in e.g., REW.  Furthermore, the diffuse energy may difficult to discern from noise in the IR.  With the right analytical tool and higher SNR in the IR measurements, the difference may become more apparent.

 

It is very interesting to me that the ear can discern sound at very low SPL relative to the main signal if that sound is highly diffuse in time.  I guess it shouldn't be surprising because studies indicate that the loudness we perceive has more to do with energy arriving over time periods of roughly 10-80 ms than SPL.  Substantial sound energy diffused throughout that duration can sound quite loud despite the fact that the SPL may be negligible.

 

By the way, the diffusers don't just improve the sound in the listening area but in the rest of the house.  Even the sound in the bedroom at the opposite end of the house is much better with diffusers placed in my listening room.  The sound retains a wonderful spacious quality that is otherwise is lost upon moving outside of the listening area.  I highly recommend experimenting with diffusion in your listening space if you have not done so already.  The effect is truly transformative.

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Good post @SME, especially because you mange to focus in to one specific subject; diffusion, and elaborate on that.

 

The article has a dedicated Room Acoustics chapter, but since this article is meant to cover everything on a few pages, it simply can not cover everything in detail.

The concept of diffusion and how it works is one of the things I have deliberately left out.

 

And I believe you are right about diffusion being important.

 

This is another example of how simple measurements does not show the complete picture, because the direction of the sound field is missing, and it is not possible to retrieve that information by analyzing a standard frequency sweep measurement in any way.

 

The velocity measurement experiments revealed some interesting aspects of the sound field up into the midrange.

Since the velocity measurement is directional by nature, it will also provide information about the direction of the sound field.

 

I believe it is important to reduce the level of early reflections, and create later reflections with a diffuse pattern.

And both room acoustics and speaker radiation pattern matters for the resulting sound field.

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Good post @SME, especially because you mange to focus in to one specific subject; diffusion, and elaborate on that.

 

The article has a dedicated Room Acoustics chapter, but since this article is meant to cover everything on a few pages, it simply can not cover everything in detail.

The concept of diffusion and how it works is one of the things I have deliberately left out.

 

And I believe you are right about diffusion being important.

 

Thanks for the acknowledgement.  You are right that diffusion may be too complex of a subject to cover in a brief article.  It may at least be worth mentioning because of the substantial impact it can make.

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Interesting.  Do you ever have issues relating to HDCP encryption?  Can you point me to more info on these creations?

 

I'm actually looking to build a highly-specialized PC dedicated to audio processing very soon but am planning on going with many analog ins/outs.  It's a bit of a drag to have to have an additional ADC/DAC in the chain, but I tend to think it's a very minor compromise relative to the capabilities it will give me.  I'm planning on running 14 independent audio channels in my living room to 5 speakers (2-way active) and 4 subs.  I'll primarily be using it for room correction, crossovers, bass EQ, and perhaps eventually to handle direct music playback.

The switcher is an HDFury PCI-MATRIX 44UHD and it removes any HDCP encryption. You can remove HDCP encryption with an $18 HDMI splitter. HDFury is coming out with a new product to remove HDCP 2.2 encryption or convert between HDCP 2.2 and HDCP 1.4 encryption to make products compatible.

 

The HDMI input cards I've used are Blackmagic Design's Decklink Mini Recorder and Intensity Pro 4K and the Hauppauge Colossus 2.

 

If you want a multi-channel card, then I would suggest the Motu 16a for inputs and outputs or the Motu 24Ao if you just want outputs. These are the best pro-audio devices for use with an HTPC that I've ever used. 

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Thanks for the acknowledgement.  You are right that diffusion may be too complex of a subject to cover in a brief article.  It may at least be worth mentioning because of the substantial impact it can make.

 

I do mention that it is not desirable to add too much absorption, a totally dead room will not sound pleasant and may feel uncomfortable to be in.

Such as add slats over absorptive walls, leave some space in between ceiling clouds.

But I do not go into detailed lectures trying to explain why.

 

For 2-channel the situation is a lot easier as well, with speakers all around you will get reflections from all over the place.

 

At this level the first thing is to get them to understand that a modern living room with no curtains and bare walls will never sound reasonable.

Just adding absorption in the ceiling and perhaps some panels on the side walls will make a huge difference.

 

On the local hifi-forum I found yesterday a thread about "can you have resolution without getting the hard sound".

Here I would expect to see a discussion on such as speaker selection horn vs dome-tweeters, different approaches for room acoustic treatment, including diffusion.

What I find is a discussion on the sound differences between amplifiers - one is more open, but sounds hard, another sounds softer but not open..

Since those differences only exist in their minds, something else is causing those observations. 

It is obvious that even enthusiasts do not listen with the ears.

In this world it is difficult to get through with the message, the myths are very well established.

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I would definitely read a series of articles authored by the principles on this thread, in addition to the summary article. I know very little about diffusion, but I do like the DIY absorption I have treated my room with. Before the absorption, directional cues were not as precise as they are now.

 

JSS

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I have added more content and updated this article, but really for you @maxmercy I doubt you will find much you did not know already, in fact, I think you will find things you will not agree on - because this is meant for a much wider audience.

 

But the pictures will be nice, when I eventually get all those 3D renderings completed..

I have updated the web pages, they look great now.

 

Yes, taking control of early reflections really makes a difference, much better and more exact placement of sounds, and it just sounds better, with more separation between the instruments/sounds.

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I would definitely read a series of articles authored by the principles on this thread, in addition to the summary article. I know very little about diffusion, but I do like the DIY absorption I have treated my room with. Before the absorption, directional cues were not as precise as they are now.

 

JSS

 

Did you ever get those bass traps finished?

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The switcher is an HDFury PCI-MATRIX 44UHD and it removes any HDCP encryption. You can remove HDCP encryption with an $18 HDMI splitter. HDFury is coming out with a new product to remove HDCP 2.2 encryption or convert between HDCP 2.2 and HDCP 1.4 encryption to make products compatible.

 

The HDMI input cards I've used are Blackmagic Design's Decklink Mini Recorder and Intensity Pro 4K and the Hauppauge Colossus 2.

 

If you want a multi-channel card, then I would suggest the Motu 16a for inputs and outputs or the Motu 24Ao if you just want outputs. These are the best pro-audio devices for use with an HTPC that I've ever used. 

 

Interesting.  I planned on building my processor using a tiny chassis that only allows for a single half-height PCI-E card for which I planned to install an Ethernet AVB card to interface with the Motu 16a.  Perhaps I should reconsider?  Do you know anything about Linux compatibility for these HDMI input cards?  How about the Motu interfaces?  I figured I might have to do some kernel hacking to successfully interface to the Motu(s) over Ethernet AVB, but it'd be nice to know if these can be made to work out-of-the-box via USB 3.0 instead.

 

Also for the Motu units, do they exhibit any thumps on the outputs upon power on or power off?  It's a seemingly trivial thing, but it's one of my biggest gripes about my MiniDSP 2x4.  The power-off thump is worse and involves a brief DC pulse at the full rated output voltage.  That combined with the fact that the auto-on feature doesn't work on the plate amps on my current subs so I end up leaving them on all the time.  I was in the shower one morning when a freak lightning strike hit some power lines somewhere nearby causing a momentary power loss.  I about jumped out of my skin from the ensuing thump which made the thunder crackle seem weak in comparison.  I can only imagine how much crazier it would be if I had 4 X 18s or 8 X 15s running along with a high sensitivity speaker build.  That sort of event could easily top out at 140 or even 150 dB.  Ouch.

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Did you ever get those bass traps finished?

Sadly, not yet.  I have been making ballgloves in the interim:

 

https://goo.gl/photos/2g1BqakX8YrGUXUo6

 

But I hope to get the bass traps and the 7.1 Audio Test Disc done soon.

 

 

Kvalsoll,

 

I'll definitely have a read.  I always like hearing other's viewpoints on room acoustics.  There is so little hard research/recommendations/guidelines out there.  Toole basically summarizes work done so far in his book, but no clear guidelines or why one approach over another is better is really discussed.  I probably over-absorb in my room, but only to take the room as 'out of the equation' as I can.  I don't think my room is 'uncomfortable' in any sense.  I'm sure adding diffusion in front of many of my panels could help MF/HF while still absorbing LF, and if it also removes some of the harshness, that would be icing on the cake.

 

JSS

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Sadly, not yet.  I have been making ballgloves in the interim:

 

https://goo.gl/photos/2g1BqakX8YrGUXUo6

 

But I hope to get the bass traps and the 7.1 Audio Test Disc done soon.

 

 

Kvalsoll,

 

I'll definitely have a read.  I always like hearing other's viewpoints on room acoustics.  There is so little hard research/recommendations/guidelines out there.  Toole basically summarizes work done so far in his book, but no clear guidelines or why one approach over another is better is really discussed.  I probably over-absorb in my room, but only to take the room as 'out of the equation' as I can.  I don't think my room is 'uncomfortable' in any sense.  I'm sure adding diffusion in front of many of my panels could help MF/HF while still absorbing LF, and if it also removes some of the harshness, that would be icing on the cake.

 

JSS

 

I have already added more to the acoustics chapter.

It is a very complicated subject, and ideally I would want to present easy, simple solutions that will work for everyone.

Then more people will achieve really good sound, and that will again lead to more interest and focus on sound, because it pays off.

 

One problem with this kind of article is that the ideas and principles presented can only reflect the authors opinion on the day of writing.

Next week I may find that what I believe now is wrong.

If you have an open mind, and continue to investigate and analyze, this will always be the case, that you have to reconsider and change your mind.

 

The article is easy to update, but what about the people out there that have put a lot of time and effort in implementing solutions that they now suddenly find is wrong..

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Still working on the article, and the pictures are nice.

 

Now it has a Table of contents, 38 pages, much more information ("too much information"..), I have removed most of what I really don't believe myself.

Still, it is more likely to scare off potential newcomers due to the technical oriented text and too much content - but, you really need to know all this..

 

Maybe later tonight, at least I can have a preview for data-bass ready..

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Preview:

http://www.kvalsvoll.com/Articles/HowtosetupaHomeTheaterSoundSystem.pdf

 

This is the pdf-version, I have read through this to see if there are major flaws, but I do not expect to do any major changes now.

Enable the "Show Document Outline" in the pdf-viewer and you get a table of contents.

 

I will update the web-page version soon.

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It is done.

 

http://www.kvalsvoll.com/Articles/HowtosetupaHomeTheaterSoundSystem.htm

 

With 40 pages it is likely to scare off rather than inspire, when the typical customer for ht-sound expects to buy some boxes, unpack and then - great sound.

Problem is, it isn't that simple.

And that is my intended message here - you need to do it right, and if you do, there is no "can't hear the dialogue", "no one listens that loud at home".

 

But you all knew that, so enjoy the pictures and graphics instead.

 

It is by no means a complete guide, I have tried to focus on the parts that are usually missing.

 

There are no changes from the -pdf I posted a link to earlier.

Web version has clickable pictures for zoom.

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