Building a Silent Rehearsal Studio, and need answers.

lotyboy

Member
2010-12-20 3:51 am
I play in a band and have a very basic knowledge of audio electronics, and virtually zero knowledge of electrical engineering. I have done simple projects like create my own Yamaha Subkick, built a pretty sweet Contact Microphone, and of course I have customized my guitar with new pickups, volume/tone knobs, etc. I have even built my own guitar from scratch. My latest project is a little more ambitious only because I don't understand all of the elements involved and I am afraid I am missing something. So before I even begin I am hoping people who know more than me could shed some light on the subject.

Here is the deal:

There are times when my band needs to be able to rehearse in silence in order to avoid angry neighbors, etc. And for a long time I have been interested in buying one of these cool Jamhub devices.

http://www.JamHub.com

The JamHub allows every band member to plug in and basically create their own mix in their own headphones without effecting what the other band members hear. For example if I want to hear my own guitar a little louder than everything else I can turn down everyone else as much as I need to in order to make my own guitar stand out in the mix. The reason I haven't bought one yet is that there are a few things about the Jamhub that I don't like. First off it requires everyone in the band to sort of huddle around a small device in the center of the room. Second of all I don't want/need any of the built in effects that come along with it. Third at over $300 dollars I am certain I can build a comparable product for a lot less, that will better suit my needs.

So that's what I want to do. I want to build a simplified Jamhub, that is also modular so that every band member can have their own module at their respective amp allowing band practice to feel much more natural instead of everyone huddling together. Here is the setup, my drummer uses an acoustic drum set but has a digital drum set for silent practices. My lead guitar player, my bass player and myself all have amps with built in DI outputs allowing us to go directly from our amps into any recording device without risk of destroying said device.

So we already have all of the effect we could ever need built into our amps. Our amps also allow us to put as much volume into the device (within reason) as we need too while keeping the speakers silent. Thus the device can be passive and not require a preamp.... I think.

Here is what I drew in photoshop a few mins ago. (Click image for full size)

[IMGDEAD]http://img406.imageshack.us/img406/9570/inputmodules.png[/IMGDEAD]

This is by no means a proper schematic, for instance I don't have positive and negative wires in the diagram, it is really more of just a guideline so that I don't get lost while actually assembling this thing. Anyway I want to build 4 of these identical Input Modules, one for each band member. Into which we will each plug in our respective instruments off our amps. The amps will be amplifying the signal, but will not be heard in the room itself.


Each input module connects to the other input modules via the output jacks on the side, and input jacks on the top using standard ¼” speaker cables. This will allow all 4 players to hear all four instruments. Each player can then change the volume of the other players instruments, as well as their own via the volume knobs (might be replaced with sliders) on the device without altering what the other players hear. The Input modules job is to give every band member the ability to create their own personal mix via volume knobs/sliders.

Here is how the device should work: (Click image for full size)

[IMGDEAD]http://img840.imageshack.us/img840/9809/signalflow.png[/IMGDEAD]

As you can see there is a total of 4 signals going into each input module. #1 being the performers own signal coming in at the bottom of the device, and #2-4 being the other band members signals coming in at the top of the device from their respective input modules. Each signal has its own volume knob. Since obviously the signal cannot get any louder than it's source without a preamp built in, mixing will be done by turning down the things you don't need to hear as much, allowing the signals you do need, to stand out more in the mix. Your own signal is also split and sent to the other band members respective input modules via standard ¼” speaker cables so they can do the same, as well as forth output which can go to a mixer or recording device.

The result in a silent practice session to the outside world, while rocking out via headphones.

So I have a few questions.


  1. Do I NEED to put resistors in the Input Modules to keep all the channels from bleeding into one another via their connection to the headphones? Or is that not likely to happen?
  2. If so is 10k too much? Too little? I settled on 10k after finding a tutorial on how to make a mixing board online.
  3. Is my placement of said resistors correct? I assume the resistors need to go immediately after the input and immediately before the outputs to stop any signals from traveling back the wrong direction.
  4. Will I need a ground? I am assuming I will, and have planned to install a common ground for all of the components to connect to. But is this necessary? I have noticed in the guitars I have owned, a few were grounded to the bridge while others had no ground at all. So I am a little unsure about when a ground is necessary in passive devices.
  5. Will a built-in preamp be required to successfully send the signal five or six feet through standard ¼” speaker cables to the other modules? Or will the signal be strong enough to travel that far by itself?
I certainly appreciate any information anyone can give me, as I have said a lot of this stuff is still pretty new to me. If you'd like I will be happy to post photos of the device as I build it as well as when it is complete. Sort of a step by step type thing, if that's something the community would even be interested in.

Thank you in advance, I really need the help.
 
I thought this thread was going to be about soundproofing a room so I was ready to go to town.

Since it is not, the only thing I can think of that might help you is to ask you if you have considered whether or not the drummer will be able to hear the other bandmembers over the sound of his drums even if you completely leave him out of the headphone mix? Also even if he uses his electronic drums it is very difficult to get them in everybodies headphone mix and still be able to hear anything else. You will have to get some DJ headphones rather than audio-mixing ones because none of them can handle the levels you will need IMO.
 

lotyboy

Member
2010-12-20 3:51 am
Yeah, Silent Rehearsal Studio does sound like it would be all about sound proofing. Sorry about that. But that's what devices like Jamhub are called. I should have just used SRS in my thread title but didn't think anyone would know what that meant.

Anyway, my drummer will be using a digital drum set for rehearsals. Also we have a good set of isolating headphones if outside noise is a problem. Just as a test I connected my amps DI to 5 sets of headphones (using Y cables) and didn't really notice any drop in volume, versus 1 set of headphones. Though the volume is always incredibly low via DI. They're built to send a safe signal to a mixing board, or recording device, so it's basically an unamped signal.

This raises a new concern that instead of too loud, the resulting mix might actually be too quiet to hear effectively.

So I found a clever way of adding a preamp to the device without having to build one. Amazon sells some really really small headphone preamps for a little over $5 bucks. It MIGHT fit inside my device, but even if it doesn't, connecting it inline between my device and the headphones won't be an issue.

I have also slightly modified the design since my last post. I think I need to use diodes as opposed to resistors, as I am trying to keep the sound from traveling in the opposite direction. Also, even though the output in my experiment was pretty quiet Db wise, I am concerned that the amount of voltage coming in through the various inputs (12v x 4) might overload the headphones, so to avoid that I have added a master volume knob to the headphone output which should allow the user to decrease the output to their headphones.

BTW I'm not planning on marketing this thing. I just want it for my own personal use. If anyone has any suggestions or comments please reply. Like I said I am really new when it comes to this sort of stuff and I am learning as I go.
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
This looks to me like a small monitor board with headphone outs instead of line level.
That is basically what a monitor board does, everybody gets his own mix.

Since this is a DIY forum, do you plan to build any part of this, such as the headphone amps? Or are you just looking for a plug and play system? Mackie makes pretty much what you need.
Mackie HMX-56
 
The real danger is that you kill your hearing.

Phones can be jacked very loud, and that will hurt your hearing.

You are used to hearing amps and drums live (also too loud - I wear hearing protectors myself) and you will not get the same sensation from headphones.

You should have no problem hearing drums or anything else - it's the same thing as listening back to a recording except ur playing live... this may help ur playing if ur not already semi-pro or pro level now.


Protect ur ears
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Yeah, I see what you mean. Bummer - I can't find one either. It seems that those who own them, love them. Don't know why they don't make them any more.

A standard mixer might do the trick, if you make clever use of the groups and aux sends. But it won't have all the headphone amps. Note: The HMX was line level input only, so you might need mic preamps if ever used a mic.

You could build something like this, but it's not going to be easy. I doubt you can get near the $300 target because you'd need so many parts. Looking at the Jamhub, I think it's going to be hard to do better. And you may actually enjoy the effects. Mixing in some reverb is going to make that headphone mix sound a lot better. Without it, it's going to be awfully dry.

So as much as I'm a "DIY-GUY", I think the Jamhub is going to be exactly what you need. Get a couple more remotes if you need them for you and the drummer, at least.
 
yeah IEM (In Ear Monitor)

these are my JH13 below (old pic, they have balanced cable now and the dac/amp I use now is fully DIY). I also think to do this anywhere near properly, your 300 dollar target is extremely optimistic and the time will be considerable. some issues; each of your headphones are going to have different sensitivity, differing degrees of isolation etc I also do not think you can do this well without buffering the signal.

in short, I think grab the commercial offering, or grab a second hand mixer with mic pre and some wireless transceivers to connect the headphones to.

also signals do not see road blocks (diodes)and turn around to go the other way ;) there is simply no potential for the signal to exist anylonger

and yes your mixer absolutely 100% needs a ground
 

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lotyboy

Member
2010-12-20 3:51 am
Thank you everyone for your help. Seeing as I am almost done with one of the units I have decided to finish it off just for the learning experience and see how it works. But ultimately I am probably gonna end up biting the bullet and buying a Jamhub or if I can find one used some where, one of those Mackie mixers.

As much as I have already spent on this one unit I am not even sure if it would be any cheaper to build one myself, at least not cheap enough to justify. Thank you again though everybody. I'll be around, but I am leaving town for awhile so have a happy new year!