[CRESCENDOPOWER]

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Originally Posted by sxr71 The second thing was that it really cut down the highs and made cymbals and such sound quite dull. Maybe you need headphones equalized for binaural recordings like the ER-4B to make it sound right. This is just a guess and I don't really know for sure. Maybe crossfeed + some sort of equalization will make it sound right to me.

These guys make amplifiers that might be what you are looking for:

http://www.headphone.com/

 

[mycoman]

To me and my tastes, crossfeed is an absolute necessary part of a really good headphone amp. With that said, I also think having the choice of using it is also necessary. As mentioned so many times here... not all recordings benefit from it like others. The ones that do benefit from it can be magical.

You can say whatever you want about HeadRoom products but one thing I find very difficult to find fault with is their crossfeed circuit design (or should I say its effects). In my experience, there is none better for what it is intended to do.

My Porta Corda comes very close but it seems the HR design is just a tad bit better.

As much as I love my Xin V6, I have to say that the crossfeed on it seems almost to be wired "backwards". That is, I get the fuller soundstage with the function switch in the "out of circuit" position. Perhaps I read the directions wrong and what I think is out of circuit is actually in circuit. Does anyone else notice this? Again, nothing against Xin and his obvious genius but I think it becomes clear that a lot of thought and trial and error evolution went into HR's crossfeed design. (btw, Xin's bass boost circuit more than makes up for any shortcomings that may be found in his crossfeed design)

Speaking of this effect we all know as "crossfeed", does anyone remember the Sonic Holography circuit in Bob Carver's products. The idea there was to actually cancel out the opposite channel (for a given ear) to give better separation and more of a "headphone effect" using stereo speakers. If you were in the sweet spot, it was simply amazing the result that could be acheived with high resolving radiators. It was this experience that sold me on the validity of crossfeed in a headphone amp. Just the right amount is a really good thing... but it has to be done right.

Good thread... David

 

[rickcr42]

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I suspect the question of crossfeed vs Dolby Headphone (DH) boils down to which enhances the headphone experience the most - or at least which do I prefer - even after the debits are considered (cost, noise, convenience, availablity).

totally different.not mutually exclusive but complimentry in fact.

Dolby Headphone is an attempt to simulate multichannel loudspeakers in a stereo headphone.sounds great with surround encoded DVDs but not so good with straight music CDs because the attempts at making the stereo signal a multi-channel signal sound unnatural without the added "visual" stimuli pf the video screemn which reallys is what holds everyhing together amd what makes the whole thing work

Headphone Crossfeed is the attempt to simulate "TWO" speakers in a stereo headphone.This in other words an electronic means to recreate the natural left and right channel crossing that occurs in a room with speakers in an environment where the left and right channels are TOTALLY isolated by your head being in the way.The old "hole in your head" syndrome

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Plus creating one DH disk allows one to listen to headphone-specific music on any machine with a player. One could also store it in an iPod.

once encoded onto a disc is playable on any format as would be any FX but again,for music not the best choice AND once coded to the disc you can never have straight stero playback of that disc for spoeaker use.it must always be used with headphones or it will sound bad.

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Since I wrote my post last night, I was able to do some more research.

Always a good thing and one lacking many times.Better to ask a question on research not understood than to expect others to do all the work

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What I haven't located yet is a program to convert straight WAVs to DH WAVs.

Chances are you will not.Dolby Headphone is a liscenced code and not open source so any such programs you find will only be legal if they "approximate" the technology and not if they are in fact the actual code.

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Rick or anyone have direct experience with DH or could identify the software/hardware I would need?

If you are up to it and you have the desire then do some heavy reading on the subject of headphones and multichannel emulation then go to Analog Devices,buy the SHARC DSP eval kit and code your own !

There ARE also at the same site the actual codes for the Dolby Heaphone Technology but you must be liscenced and that means meeting certain requirements.

I'll wrap up with a couple of points :

For movie viewing with headphones the best "surround sound" I have ever heard was a direct disc encoding ogf the dolby Headphone tecnology.this may be a case where leaving the control of the parameters is just better off left to the sound engineer who knows what sound goes where in the overall soundfield and not in the hands of a clueless consumer.

For music reproduction with cans i find a crossfeed to be essential for much of my listening.Not all but still nice to have access to when I feel it is needed.Rather than being a "surround" technolgy or in effect a "special effect" that adds to the sound it is more "blending" of what is already there and helps move the image from dead left and dead right to slightly forward with a bit of L/R mixing.It adds nothing not already there.

 

[rickcr42]

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You can say whatever you want about HeadRoom products but one thing I find very difficult to find fault with is their crossfeed circuit design (or should I say its effects). In my experience, there is none better for what it is intended to do.

Agreed.the best out there and actually the first commercial implentation.Without Headroom we would not be having this conversation.
I know why theirs works better and have come reeeaaaal close to posting my thoughts but since they did the work the do not deserve me posting and then the DIYFP crew whipping out versions a week later at 1/4 the cost.
Paying an engineer,doing all the work and toutting the technology in print ads deserves better than that so i "zip it"

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Speaking of this effect we all know as "crossfeed", does anyone remember the Sonic Holography circuit in Bob Carver's products. The idea there was to actually cancel out the opposite channel (for a given ear) to give better separation and more of a "headphone effect" using stereo speakers.

Yup.And "Omnisonics processing" which lasted all of two years as a commercial "add on" with many well known companies offering a version.
I built the "poor mans" version from a magazine article and it was crapcanned soon after as a cool idea that just was not useful in everyday use.Too restricive and took away one of the reason for loudspeaker use which is group sharing and freedom from the cord.
By being locked into a single position an extended session could actually give you a stiff neck.

I always thought a "comprimise" device that relaxed the total subtractive nature and made the effect more diffuse would be better.The central position would not be as dramatic but with the effect being wider thus easily heard throught a wider range of seating positions more effective in real use.That was then though and this is now.Now I am satisfied to have :

1-passive crossfeed for stero music
2-passive ambience extraction for live music/passive surround simulation


Best case for Movies would be a stand alone Dolby Headphone Decoder.One that I am not stuck with it being wrapped in an entire receiver or bundled with a sound card I do not want but a small "black box" that I can simply flip a switch to insert into the signal path.Someone offers one at a reasonable "consumer level" price and not "audiophile" prices and I buy it !
Second choice/maybe first would be to have ALL DVDs encoded with Dolby Headphone.There is plenty of room on the disc if you take all the added crap they use as fillers of so why this is not the reality eludes my comprehension

As always just and opinion.Mine and mine alone

 

[sxr71]

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Originally Posted by mycoman To me and my tastes, crossfeed is an absolute necessary part of a really good headphone amp. With that said, I also think having the choice of using it is also necessary. As mentioned so many times here... not all recordings benefit from it like others. The ones that do benefit from it can be magical. You can say whatever you want about HeadRoom products but one thing I find very difficult to find fault with is their crossfeed circuit design (or should I say its effects). In my experience, there is none better for what it is intended to do. My Porta Corda comes very close but it seems the HR design is just a tad bit better. As much as I love my Xin V6, I have to say that the crossfeed on it seems almost to be wired "backwards". That is, I get the fuller soundstage with the function switch in the "out of circuit" position. Perhaps I read the directions wrong and what I think is out of circuit is actually in circuit. Does anyone else notice this? Again, nothing against Xin and his obvious genius but I think it becomes clear that a lot of thought and trial and error evolution went into HR's crossfeed design. (btw, Xin's bass boost circuit more than makes up for any shortcomings that may be found in his crossfeed design) Speaking of this effect we all know as "crossfeed", does anyone remember the Sonic Holography circuit in Bob Carver's products. The idea there was to actually cancel out the opposite channel (for a given ear) to give better separation and more of a "headphone effect" using stereo speakers. If you were in the sweet spot, it was simply amazing the result that could be acheived with high resolving radiators. It was this experience that sold me on the validity of crossfeed in a headphone amp. Just the right amount is a really good thing... but it has to be done right. Good thread... David

I noticed exactly the same thing with Xin's implementation. The soundstage actually becomes smaller with crossfeed. I think we're doing it right because the image actually does move forward and I followed the instructions carefully with regard to putting it in or out of the circuit. Also agree about Xin's bassboost - that thing is surprisingly good.


Regarding the Carver Sonic Holography concept, someone posted here about a certain line of Polk Audio speakers that do the same thing in the speakers/crossover. I don't know how it sold you on crossfeed because the two concepts are completely opposite in nature. Unless you are looking for that middle ground between the loudspeaker and headphone experience; which might be worthwhile.


Regarding Headroom's crossfeed, I wish they made a stand-alone crossfeed circuit. Maybe it's time for me to just try a Headroom Micro Amp w/ Desktop Module for home use.

 

[rickcr42]

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Regarding Headroom's crossfeed, I wish they made a stand-alone crossfeed circuit.

Has happened but not cost effective and do not sell very well.the response from the consumer is "why should I pay X$$$ for a stupid crossfeed when for a couple of more dollars I can get a crossfeed AND a headphone amp ?"

what many fail to realise is fully 75% of the cost of any audio product is in the chassis and power supply so it is far cheaper to add more stgaes internally than to offer two seprate devices each with their own chassis and power source.That is the bassis of the Integrated Amplifier and the Receiver which are built purely for cost savings but if you want the best separates are and will alwys be the way to go.Expensive but better.

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Maybe it's time for me to just try a Headroom Micro Amp w/ Desktop Module for home use.

You could do a lot worse and not a whole lot better if at all for the price.

What you get with the "established" companies is long term support and a fully engineered product that will not be "new and improved" every six months or every year.
No "opamp" rolling or capacitor swaps to make something work to your expectations,no hidden glitches that you need to have explained to you after you blew up your amp,no "you can't use this amp with this XXX",but ready to rock out of the box with full backup from the company if anything does go wrong

No small thing in my mind and for many other who want to listen to the music and not play with a "new toy"..

 

[Tyll Hertsens]

Great discussion guys, just thought I'd add a couple of comments:

First, HRTF means "head related transfer function." An HRTF is the formula needed to change the nature of the origional sound so that it includes the information your brain needs to percieve it as comming from somewhere in space around you. The HRFT varies as you move the speakers left to right, but it also varies with many other things (the shape of your ear, the acoustic impedance of your ear canal, the up-and-down position of the speaker, ect). The HRTF in current HeadRoom amps is done in the analog domain and really only concerns itself with the time delay and eq change with left-to-right position of the speaker. Because Dolby headphone is done in the digital domain, it can provide much more complex calculations in their HRTF and likely includes things like pinna reflections and ear canal resonances, in addition to interaural time and eq changes. Dolby headphone also creates some acoustic information about a virtual room in which the speakers are placed, and provides some artificial wall reflections and room reverberance. Like Rickcr42, I find Dolby headphone provides an excellent sens of immersion in an acoustic environment for movies, but I also find that the provision of a room acoustic is so strong that it creates a "boxy" room sound that is distructive to fidelity for music listening. BTW, Rick, I think when you feed Dolby headphone with a 2 channel signal is switches over to a two speaker model for HRTF synthysis, so I don't think it remain in a 5.1 channel mode for 2 channel music. Pretty sure, but not certain.

Earlier in the thread someone asked about higher bit rate DSP synthesis. One thing to understand here is the HRTF calculations are significantly complex. If you are inputting a 16/44.1 input data stream you may have to internally upsample, at least in bit depth, in order to make accurate calculation that can be converted back to 16 bit depth and retain fidelity. So, many times, in fact all the time if you want to retain the same level of fidelity, you have to do the math at a higher resolution than the input and output signal. If you want to do good, real time DSP work with, let's say, a 96/24 original signal and want to output a good 96/24 output, you'll have to increase the bit depth inside the DSP processor to maybe 32 bit words. The point I'm trying to get at hear is the you should not expect hi-res DSP HRTF processors to take anything more than 16/44 is ins and outs for the forseeable future because you would have to use EXTREEMELY expensive hi-speed, hi-res DSP chips. As it is, if you do top notch DSP work on 16/44 data streams you DSP part cost can easily be $50 each! Go up to the next step in resolution and you may be talking about $200 parts---if such a beast is even available.

 

[YngwieJMalmsteen]

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Originally Posted by rickcr42 I will not comment on the Headroom matrix because even though I know how it works it is their design and if they wanted the actual design details out would have posted them on their web page.

Ah, but they have. If you look to the left you'll see that tyll has actually published 5 pages about it on the website, lots of interesting stuff in there, too. For example: "The current HeadRoom crossfeed circuit uses a two-stage active filter that provides about 400 uSec of delay and a gentle frequency response roll-off starting at about 2 kHz." BTW rick, you're comin up on 10k pretty fast, I think it's about time for a ban.

I LOVE crossfeed; I didn't anticipate using it much when I got the amp but now I couldn't live without it. The added warmth is as likely to be a benefit as a detriment, and with DT 880 is nearly always a benefit. I think headrooms is the most convincing because of the active circuit (more delay time), and from what I've read the newest line of amps' crossfeed is significantly improved from older headroom models.

It seems to me that your ears locate in the same way your eyes do, and that your brain needs to be able to triangulate to locate accurately.

 

[rickcr42]

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BTW, Rick, I think when you feed Dolby headphone with a 2 channel signal is switches over to a two speaker model for HRTF synthysis, so I don't think it remain in a 5.1 channel mode for 2 channel music. Pretty sure, but not certain.

Actually never considered that Tyll.Thanks for the heads up.(more research

)

And I also find the same sonic signature to be true when using Dolby Headphone for music only reproduction while finding it totally enjoyable for movie FX which is also not surprisingly what I find with the big rig.

surround sound is fine for movie viewing but for music totally artificial sounding except for the original Hafler Dynaquad passive ambience extraction device used with two additional speakers and that only for live performances micced "honest".That is where there is a natural L-R ambient componant anyway with the device just doing extraction and not simulation.

So it just may be that no ambience simulation method used solely for music like the "music Mode" of Dolby Headphone will ever sound realistic unless it is either

A-already a live event with the "hall" information intact and just waiting for extraction (and the extraction method modified to a HRTF for cans) or
B-Specific Mixes down in the studio like the former SQ type Quadraphonics decoders but this time done right-as an ambience extractor and not as a special effect of a totally unreal event as was done in the eighties and what meant the technology was doomed to fail

Last frontier in music is the time/space relationship if you think about it.Everything else is pretty much just a refinement of something else

 

[Lazarus Short]

...which lets me use crossfeed with non-Headroom heaphone amps. When I got it, I wondered if it really DID anything, but the former owner explained that the effect is very low key, and I did find that I could listen longer and/or louder to headphones by using the devise. It's now permanent in my system.

Laz

 

[rickcr42]

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Ah, but they have. If you look to the left you'll see that tyll has actually published 5 pages about it on the website, lots of interesting stuff in there, too. For example: "The current HeadRoom crossfeed circuit uses a two-stage active filter that provides about 400 uSec of delay and a gentle frequency response roll-off starting at about 2 kHz."

Yeah,Tyll gives a lot of "clues" going all the way back to the original headwize article some 6-7 years old now but still is way over the head of many "would be" amp manufacturers who need the design done for them even to the point of "what size resistor do I use for....." and a week later they are selling amps thinking putting the parts in a pretty box makes them a designer.

Not me ! Nope ! My attitude is "do your own dirty work"

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BTW rick, you're comin up on 10k pretty fast, I think it's about time for a ban.

and way overdue if according to my "fan club"

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I LOVE crossfeed;

one of those deals where you don't think you need it until you get used to it then if taken away you miss !

 

[Tyll Hertsens]

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Originally Posted by rickcr42 So it just may be that no ambience simulation method used solely for music like the "music Mode" of Dolby Headphone will ever sound realistic unless it is either

Ah ha! I caught you! You didn't mention: C) Meant to simulate a perfect listening environment when the audio is reproduced on 2/5 speakers.

The assumtion here (as you so very well know and have state so many times before

) is that that's what the guy who designed the sound was mixing it for. I think that if you're going to synthesize a room, synthesize a really good sounding one---not some stark set of walls.

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Originally Posted by rickcr42 Yeah,Tyll gives a lot of "clues" going all the way back to the original headwize article some 6-7 years old now but still is way over the head of many "would be" amp manufacturers who need the design done for them even to the point of "what size resistor do I use for....."

It's over my head. I needed real engineers to do it. But, in terms of normal analog audio engineering it's a pretty trivial problem, and I have provided enough information for an engineer to fairly easily replicate it.

 

[rickcr42]

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Ah ha! I caught you! You didn't mention: C) Meant to simulate a perfect listening environment when the audio is reproduced on 2/5 speakers

Ooops ! What I meant to say was...um.....er...OK.I take the hit

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I think that if you're going to synthesize a room, synthesize a really good sounding one---not some stark set of walls.

Exactly.Remeber the old Yamaha Ambience Syntesizers ? Pretty good implementation of the "venue" even though the technology at the time had severe limits.
Instead of some "room" you had a choice of presets for specific (sometimes very specific down to hall name !) arenas and you would suit the music to the "this is possible" room size PLUS had the ability to even firther "tweak" to your favorite position in the audience.
So Rock would be anything from "Bar" to "small arena" or "large" arena and with the grand daddy of "outdoor stadium" (which was also dead on for Marching Band music)
Then you had "jazz club" for small groups,"Cathedral" for pipe organ music plus sevaral concert halls for classical.

One thing about the devcie that was a total turn off for me even though i admired the effort was the fact that everything had to go through this device before it reached the power amp so whatever its circuitry colorations/limitations so would everything going through be effected.not good if you have a transparent or personally satisfying "sound" that is then sent to a bazillion transistors and hundreds of capacitors

The core idea though was music is not a static medium and you need to fit the "room" to a venue that could conceivably support it.Having a 25 piece marching band in your living room is not possible but the "illusion" can be as long as you keep your eyes closed (my theory on the eye/ears/brain connection where one tells the truth and the other lies and means not beleivable at all.The never talked about "visual" part of audio reality

)
With the small scale performance,that is maybe a solo vocalist accapello or the singer/guitar player and in a larger room a piano or possibly trio you need zero artificial enhancements as long as you can get the dynamics right which to me on the "realism " scale are far more important than getting the tone right if realism is the goal.to add an effect to a room sized performance can only sound artificial since there will be no actual "space" to simulate !

So the DSPs all fall down by trying to make the ROOM sound like surround instead of removing the room boundries from the equation and creating "space" and without ever taking into consideration the actual music type and if it even fit the "this is it" model.

I hate to single out a legitimate product in public for abuse but while the movie mode of Dolby surround can be very effective the music mode falls short and is comprimised.Then again they are far smarter than me so maybe I am off base on the "why".

rick don't always know which road to take but when he arrives at the destination no one needs to tell him "you are here"

 

[mycoman]

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Regarding the Carver Sonic Holography concept, someone posted here about a certain line of Polk Audio speakers that do the same thing in the speakers/crossover. I don't know how it sold you on crossfeed because the two concepts are completely opposite in nature. Unless you are looking for that middle ground between the loudspeaker and headphone experience; which might be worthwhile.

It sold me on crossfeed for headphones because it is, in an abstract way, a very similar concept even though their actual mechanics are opposite (one cancels out and the other adds). Mixing time delay and signals that are meant to "fool" the brain, they both have in common. If it worked for speakers, I figured it had an even better chance of working for headphones.

 

[Skylab]

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I LOVE crossfeed; I didn't anticipate using it much when I got the amp but now I couldn't live without it.

Same here. It was crossfeed (Headroom's, initially) that made me discover I could actually enjoy headphone listening deeply. Prior to that I was strictly a speaker guy at home.

I have owned amps with Crossfeed from Headroom, Meier, and Xin. I find all to be effective, although I prefer Meiers because, best I can tell, it does not introduce frequency-response deviations. Headroom's does. I'm not sure why this is. Xin's "Xinfeed" is good, but I agree that it seems to shrink the soundstage slightly, whereas both Meier's and HRoom's expand it as well as bring it forward.