Acoustic Simulator

[EloyDark]

Hello from a new member of the forum (although I have been reading, I have never posted again).
I have been interested in headphones for about 2 years, I have done a lot of reading and have some equipment that is quite good as I believe. I am now interested in building an acoustic simulator for my head-fi system, but most of the diy crossfeed designs available are really simple and not very adjustable. This is also true for most crossfeed programs for computers. What I am looking for is something better, something that is worth building and integrating it on my system's chain!
Do you have any recommendations or ideas?
What kind of Crossfeed do you use in your head-fi system?
Thanks in advance

 

[JamesL]

I haven't tried it, but tangent offers a crossfeed pcb/kit for a $12.
Also, meier audio offers public schematics for a crossfeed design. I think they offered pcb boards at once, but I think you'll have to protoboard or p2p.

 

[EloyDark]

Yes I am aware of both of these schematics but they are not exactly the best options for audio fidelity. Full of capacitors on the signal paths, they will certainly destroy the signal before you know it. What I was searching for is something with active components that could mix the channels in a controllable way. Something like an active DSP, like the digital equalisers. Any ideas?

 

[Fixz8]

Quote:

Originally Posted by EloyDark /img/forum/go_quote.gif Yes I am aware of both of these schematics but they are not exactly the best options for audio fidelity. Full of capacitors on the signal paths, they will certainly destroy the signal before you know it. What I was searching for is something with active components that could mix the channels in a controllable way. Something like an active DSP, like the digital equalisers. Any ideas?

That's really contradictory. If a single capacitor in the signal path is going to wreck the integrity of your signal... using a DSP and having to go through a ADC and DAC is going to be much worse.

So you're looking for a crossfeed with some sort of equalizer capability? So you would have a control for overall "crossfeed strength" and then individual controls for certain frequency ranges? Sort of like a volume knob and then low/mid/high settings on a car stereo?

 

[EloyDark]

Quote:

Originally Posted by Fixz8 /img/forum/go_quote.gif That's really contradictory. If a single capacitor in the signal path is going to wreck the integrity of your signal... using a DSP and having to go through a ADC and DAC is going to be much worse.

That is why I was searching for something with a digital input so I would "change" the signal and then put it in the DAC for convertion, I guess that's all too ideal to be constructed! If I were to put capacitors, then there would be no point in building amps like the Dynalo and Dynahi! The capacitor is not just put in the signal, it is also crossing on a very sensitive area! That is exactly what I am trying to avoid. I have tried some software crossfeeds but they are not exactly what I wanted!

Quote:

Originally Posted by Fixz8 /img/forum/go_quote.gif So you're looking for a crossfeed with some sort of equalizer capability? So you would have a control for overall "crossfeed strength" and then individual controls for certain frequency ranges? Sort of like a volume knob and then low/mid/high settings on a car stereo?

Yes, kind of like that but not that simple, more like a Behringer DEQ2496 (I know that's too much to ask

) but with crossfeed options as well...

 

[EloyDark]

I have just found out that Behringer has a product called VIRTUALIZER PRO DSP2024P that has psychoacoustic capabilities such as Stereo Imager and Binauralizer with some adjustability. Has anyone tried it? Although it's not exactly DIY what I am asking right now, the thread began with a DIY topic

 

[dgbiker1]

Sounds like you need Rockbox. It has everything you want built into the software, and you don't need to go through A/D then D/A conversion (which can be far worse than adding passive components in the signal path).
EDIT: Ahhhh, I see what you're saying with the digital input!

 

[EloyDark]

By Rockbox you mean the firmware for the mp3 players? How would rockbox be helpful in what I want? :S (confused once more)

 

[utilisateur]

I think Rockbox would only help you if you had an Ipod or other Rockboxable dap as source..

The ideal solution for a digital playbackchain would be a FIR filter imo. If your RCD991 is your main source and DAC though that might not help you..

I think it would be doable to implement a FIR crossfeed filter to be used with foobar - there are already some people feeding a FIR filter from foobar..

Although i'd actualy love to do just this i have not had the time to look further in to it..

You could try this atleast as a temporary solution =)

 

[EloyDark]

Quote:

Originally Posted by utilisateur /img/forum/go_quote.gif I think Rockbox would only help you if you had an Ipod or other Rockboxable dap as source.. The ideal solution for a digital playbackchain would be a FIR filter imo. If your RCD991 is your main source and DAC though that might not help you.. I think it would be doable to implement a FIR crossfeed filter to be used with foobar - there are already some people feeding a FIR filter from foobar.. Although i'd actualy love to do just this i have not had the time to look further in to it.. You could try this atleast as a temporary solution =)

I have tried some FIR filters with foobar such as bauer Stereophonic-to-binaural, Crossfeed and I have just tried the one you recommended (Yohng 4 Front) but they are not really adjustable.

The one you recommended is the worst I have tried (no hard feelings

) because I feel it alters everything. It is as if it is trying to emulate a concert hall by adding a lot of echo...

Any other recommendations?

 

[dgbiker1]

Quote:

Originally Posted by EloyDark /img/forum/go_quote.gif By Rockbox you mean the firmware for the mp3 players? How would rockbox be helpful in what I want? :S (confused once more)

Yes, that rockbox. It has a very customizable crossfeed and equalizer built into it.

 

[utilisateur]

Sry i just listened to it again after recommending it (wrong order

) and found out the same thing, its simulation is quite nice but its not trying to give a more natural feel with your headphones but to emulate a preset room with speakers... sry

I couldn't get that bauer plugin to work but the others didn't impress me much either..

I will stick my head into FIR filter implementation anyways for a future speaker project but a considerable amount of time will pass until then.. guess i cant help farther ..

->X2 on your original question

 

[EloyDark]

@dgbiker1
I was pretty much referring to chain-reproduction machinery. I could use Rockbox when I buy a portable mp3 player but this is not my "main" question. What I am searching for is something I can connect to my main source (either Rotel and PC if it is Hardware or just my PC if it's software)

@utilisateur
Don't worry, after all just trying is not bad, I didn't have to pay anything to try it so it's OK
The bauer is not that hard, it is installed the same way other foobar plugins are installed. However it is very much like the other crossfeeds.

So we actually do have something that is really hard and noone has found a decent way to implement it. So when I have some more free time, either I have to start studying some DSPing or try some of the psycho-acoustic products already available in the market.
Thx

 

[utilisateur]

I've been thinkering around it again,partially because of that Smyth DSP
and because i'm going to build a simple analog Crossfeed for a StarvingStudent..

1 Shouldn't the delay be adjusted to the users head?
Of course natural crossfeed only handles IID ITD as a simple aproximation of HRTF
but would an adjusted circuit not be superior?

2 The Smyth virtual Surround Technolgy seems to be great from what those who heard it say
but its downside is it mimics a real speaker setup with wall reflections and other possible side effects which imho are detrimal to headphone playback

-> Which effects beside IID and ITD are important for spatial localisation?
Aparently Pinnae reflections dont have to be adjusted to ones ear as the brain is capable of adjusting to an altered pinnae shape
(Shown by psychoacustic experiments at the U of Nijmegen)
So theres still the Interference with the head

In the end Binaural recordings are at least in theory a step ahead and cannot be reached by postprocessing
but if the Smyth System left such a great impression
the effect that can be achieved seems to be great..


I thought it might be interesting to discuss the psychoacoustical background as far as our combined cognition might serve us
[size=xx-small]I do not want to reverse engineer the Smyth Virtual Surround Technology it just served as an example[/size]

 

[EloyDark]

Yes, now we have something serious to begin with.

I haven't seen the Smyth DSP up till now and I must admin I am impressed. This is very close to what the ideal should be, but the price tag is really high. For something like that, microphones and special measuring equipment is needed in order to measure the HRTFs and then "input" them in the signal.

Of course this is only on the correct track but not perfect yet. IMHO since it uses DSP it should have digital inputs, the A/D and D/A that happens in the box is not necessary. Also as you have said, this system can only measure your HRTF for THAT ROOM. What are we trying to achieve, why are we using headphones? If I used something like this I would probably listen to all of my room's resonance frequencies. This is what I am trying to avoid, that's why I thought that it's easier and perhaps more convinient to make something that is adjustable, you can alter the equalisation, the time delays, the equalisation of the time delays etc etc.

Binaural recordings really are the best, but just like high end productions, they are very rare, I will not limit my music choices because there are no recording for my system!

Reverse engineering such an equipment is really very hard, I don't have that kind of ambition, I am just searching for something that can take the headache out of me and give me the oportunity to expirement further more!