http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

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Cheap Acoustic Simulator (Crossfeed) for Headphonesby faxwork on November 14, 2010

Table of Contents

Cheap Acoustic Simulator (Crossfeed) for Headphones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro:   Cheap Acoustic Simulator (Crossfeed) for Headphones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1:   What is a crossfeed? (Theory) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 2:   Tools & Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 3:   Protoboard Substitution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Step 4:   Build . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Step 5:   Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Step 6:   Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Step 7:   Final Thoughts and Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Intro:  Cheap Acoustic Simulator (Crossfeed) for HeadphonesHi! Welcome to my second instructable! Don't forget to rate and comment! :D

First off, what is an "acoustic simulator"?

It can be anything to simulate the effect of being in a room, creating an effect of open space, or even give the illusion of hearing sounds from different directions. This isusually achieved through software. Results vary, as there is coloration to the sound and the simulations can be very invasive to listening.

Unlike software implementations, what I will show here is a simple hardware solution to get rid of the "in-head" effect that headphones have. It is not designed to give theillusion that you're in an auditorium with reverb. Rather, it is designed to simulate the feeling of hearing audio in front of you. Its purpose is to improve the soundstage.

The main goal is to reduce fatigue and make headphone listening natural and pleasant.

In this instructable, I will show my build of a Linkwitz crossfeed . This particular design was modified by Chu Moy , the person responsible for the famous "cmoy"headphone amp design. I take no credit for this design, only my simple modifications.

Step 1: What is a crossfeed? (Theory)When you hear sounds panned hard right/left with headphones, you don't hear anything in your other ear. In real life, you always hear sound with both ears. A personspeaks to the right of you. Do you only hear them with your right ear?

In reality, you're hearing with both. Your brain recieves signals from both ears and interprets the direction from which the sound is coming from. You may be hearing tothe right of you, but your brain also interprets if the sound is close, far,  in front of, or behind you. When you listen to audio with headphones, this directional information islost.

To remedy this, we welcome the crossfeed . A crossfeed circuit bleeds the left and right channels just a bit to give off  that lost sense of direction. While it does not givethe illusion of surround sound, it does give you the feeling of listening to audio from speakers in front of you rather than through headphones on your ears.

Music from live performances and orchestras sound particularly good with a crossfeed. Mono recordings and music that generally sits "in the middle" will not benefit froma crossfeed much, or at all.

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Image Notes1. Grado SR80i headphones.

Step 2: Tools & ComponentsOther than the cost of shipping, the components required to build this circuit are fairly cheap. If you cut the cost of enclosure, protoboard, and tools, you can probablybuild one with very little money. You may even have some of the parts lying around from other projects.

Because I was aiming to spend as little money as possible, I made some changes to the modified Linkwitz crossfeed that is presented by Chu Moy .

The original circuit had a switch for bypass and another to adjust the "perspective" of the crossfeed effect. I did not use these. A bypass would only be good if you wantedto compare before and after crossfeed. The other switch was not used, as I did not care to adjust the crossfeed from my final setup and wanted to save a little moremoney.

Test the circuit on a breadboard, if you have one. You may want to make changes as stated in the notes below.

Tools :- soldering iron and solder- small screwdriver- scissors / wire cutter

Components :- 2x 150 ohm resistor (R1)*- 2x 100 ohm resistor (R2)- 2x 910 ohm resistor (R3)- 4x 330 ohm resistor (R4,R5)- 2x 0.22 uF, 35V film capacitor (C1)- 2x 1.20 uF, 35V film capacitor (C2)**

- 2x 3.5mm audio jack***- 3.5mm male-male cable to connect to devices***

- jumper wire- protoboard / cardboard(?)- something to put it in

*You can experiment with the soundstage and 'open-ness' of the sound by using different values of R1. Lower values will make it feel as if you're hearing things fartheraway, while larger values will bring sounds closer towards the middle. The "perspective" switch in Chu Moy's original schematic switched between values of this resistor.

**Changing C2 will alter the threshold frequency and depth of the crossfeed. I used a 1.0 uF capacitor instead of 1.2 uF. More explanation on threshold frequency andhow this works can be found here .

***Depending on the type of input you're using. You may want to use RCA or 1/4" jacks and cables.

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Image Notes1. Hammond 1591MSBK

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Step 3: Protoboard SubstitutionI did not have time or money to go out and buy prototype boards, so I decided to improvise. As you can see by the image below, instead of protoboard, I decided to solderon top of cardboard . It is much like point-to-point soldering, only you have something to hold everything in place. I cut a piece from a box, as it has more than one layerand doesn't bend or fold easily.

The first thing you should do is figure out the layout. If you decide to follow my simple circuit, I have provided some images on what the layout should look like. While itisn't the most compact, it is very easy to follow.

Simply poke holes with your small screw driver to where the components will be placed.

Image Notes1. Poke holes based on layout.

Image Notes1. First try. Decided it wasn't good enough and did another.

Step 4: BuildThere are a few ways you can go about soldering the components to each other on the cardboard. I went ahead and placed all the components on the board and bentthe leads, to prevent them from falling off of the board.

Make sure to bend the leads, that are to be soldered to each other, in the same direction and group them where applicable. You can do one entire channel first, and thenthe other. Depending on your soldering skill, you may or may not want to solder one component at a time. Soldering groups of leads seems to be much easier.

*Be careful when soldering R5, as the leads may touch. They are arguably the most important resistors, as they are the ones where the signals are being crossed intoeach other.

Forgive my drawings, they are not to scale.

The layout follows the modified schematic in the last image. Original can be found here .

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Image Notes1. Use your scissors or wire cutters to trim the lengths of the component leadsbefore soldering.

Image Notes1. All components for one channel.

Image Notes1. Left and right channels cross. Check that R5 leads do not touch each other.2. Jumper wire.3. Jumper wire.4. Jumper wire may not be needed if you stretch the R4 lead towards C1.

Image Notes Image Notes

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

1. Grey areas are where the components are soldered together. 1. Shared ground between channels.

Image Notes1. Not a single burn on the cardboard!

Image Notes1. Completed with audio jacks.

Step 5: TestingHere comes the best part of DIY. Testing!

To test the crossfeed, all you need is some music to listen to.

If you want to see how much audio is bleeding into each channel, connect the crossfeed to your computer using a 3.5mm male-to-male extension cable and open up yourfavorite media player. Switch all output to either the left or right and see how it is. If all sound on one side seems louder than all sound on the other, you may have donesomething wrong. Check your connections!

Be aware that there will be a total volume drop due to the crossfeed. This is normal.

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Image Notes1. Hard left. You should still be able to hear something on the right channel.

Image Notes1. Hard right. You should still be able to hear something on the left channel.

Step 6: EnclosureOnce done, you need to put it in something.

I happened to have an extra enclosure laying around and decided to use that. You can use anything you want. Much like the popular cmoy headphone amp, you can tryputting it inside an altoids tin. To match the "protoboard", why not put it inside a small cardboard box? Use your imagination.

I really like these hammond cases. I tried putting a headphone amp in this particular model, but it came out very, very cramped. It seems fairly roomy for the crossfeed,and matches my amp perfectly.

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Image Notes1. Hammond 1591MSBK

Image Notes1. Some of the plastic had to be cut for audio jacks to fit properly.

Image Notes1. Completed with audio jacks.

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

Step 7: Final Thoughts and ImprovementsIt takes some time to really notice the impact of this crossfeed circuit. At first, I barely noticed it and almost wrote off the whole idea to be nonsense. After a good hour orso of listening, I decided to not use it and immediately noticed the difference. Your mind needs a little bit of training to get used to the feel of listening, and is well worththe time.

Because of the volume drop, it is important to use good, clean amplification before or after the crossfeed circuit. It works great when paired with a cmoy headphoneamplifier. While not having a good amplifier or sound source may discourage you from building this, it is still fun to try out and only requires a few components to build.

The crossfeed filter also works surprisingly well when coupled with my Playstation 3 and cmoy headphone amp. There was some benefit when playing first-personshooters online with headphones on. It was easier to determine where sounds were coming from in-game and it felt a lot more natural with the crossfeed on. If you didn'tsee it, check out my quick and dirty way to use headphones with a PS3 .

In the future, I want to build an improved cmoy headphone amplifier with this particular circuit built in. Some simple improvements I plan are to shrink the size of mylayout, use smaller sized capacitors to save space, and to possibly include a rotary switch to adjust the soundstage.

Well, those are all my thoughts for now. I hope you enjoyed reading my instructable. Don't forget to rate and comment! I appreciate any thoughts or criticisms. If you haveany improvements or suggestions, give them! Thanks. :]

Image Notes1. CMoy headphone amplifier.2. Modified Linkwitz Crossfeed.

Image Notes1. Connected to Zune.

Image Notes1. Connected to Playstation 3.

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

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Comments

14 comments Add Comment

 onlinemastering says:  Mar 14, 2011. 1:50 AM  REPLYThis is an excellent project, one of the best on instructables (still I am an audio geek i woudl say that). Perfect and highly useful prooject for beginningelectronics. Thanks for sharing this, really enjoyed the read.

SafeandSoundmastering services

 7wist says:  Dec 22, 2010. 5:08 PM  REPLYThanks a ton man, I just soldered this up my my dads Christmas present :)

 faxwork says:  Dec 24, 2010. 2:03 AM  REPLYWhat a great gift idea! I hadn't thought of that.

Tell me if he likes it. :]

 killerjackalope says:  Nov 15, 2010. 6:37 AM  REPLYGreat build, I wonder it it's easier to have a physical crossfeed or not, with digital music being to ubiquitous. Though I suppose a couple of hours building thiswould be way faster than fiddling with every song...

 faxwork says:  Nov 15, 2010. 11:31 AM  REPLYI've noticed that many software crossfeeds can be invasive and can color the sound a bit. I built mine in about an hour, not including time spent designingthe layout. :D

If you want more options, consider looking in to switching between different R1 resistors. This will enable you to adjust the soundstage to your choosingon the fly.

Thanks for the comment. :)

 killerjackalope says:  Nov 15, 2010. 12:36 PM  REPLYGood to know, I may well build one depending on my ever changing sound setup, really taken to using my little bluetooth speaker about the houseand just bringing it with me but this would be great for the bus etc, using big cans seems to make the issue more apparent than leaky earbuds...

 faxwork says:  Nov 15, 2010. 12:48 PM  REPLYIt's really great to have on the go, but the only problem I have now is finding a short 3.5mm cable to use it with. Having a cable from my soundsource, between the crossfeed and amp, and my headphones is a bit much. :/

 killerjackalope says:  Nov 15, 2010. 2:48 PM  REPLYMight be better with a small cable soldered direct to the board rather than a jack.

You get short cables in audio shops, also handsfree kits etc often have odd length cables with them if it's any help...

 faxwork says:  Nov 15, 2010. 3:05 PM  REPLYI'll consider the idea. I just hate that it feels so "permanent". :p

Maybe I'll replace my input with RCA jacks instead. I see RCA to 3.5mm adapters everyhere.

 killerjackalope says:  Nov 15, 2010. 3:29 PM  REPLYHow about wiring on a little cable but keeping the input too? Just a couple of inches of cable you could slide away when you're usingthe input...

http://www.instructables.com/id/Cheap-Acoustic-Simulator-Crossfeed-for-Headphone/

 faxwork says:  Nov 16, 2010. 10:11 AM  REPLYSounds good, but I would still need to find a cable to tear apart. :|

 killerjackalope says:  Nov 17, 2010. 4:28 AM  REPLYEh there's always a rub, old headphone cord? Though the wires are a little fragile...

 Lexx217 says:  Nov 15, 2010. 2:11 PM  REPLYthanks you :)

 faxwork says:  Nov 15, 2010. 2:31 PM  REPLYWelcome. :p