Help needed: Planning to build a set of monitors for my home studio.

[docz]

It's been a while since my last post, and I have completed many projects since then. Now I'm pondering if I should try to make a set of near-field studio monitors for my home project studio. I've been working part time at a studio as a musician, and listening in the mixing booth on the monitors they use has opened a whole new world for me. I never thought monitors were necessary for my home studio projects, but hearing how easy it was to find problems in the mix and get it balanced on those monitors were worlds apart from the fiddling I do through my cans.

So I thought I would buy me some monitors. But after reading stuff online and hearing what people say, I have learned that unless I can fork out some serious cash, I'm not going to get anything near what I saw in the studio. I would be better off saving my cash and buy it when I can afford it.

Well since I'm married, and my wife would never in a million years let me spend the cost of our yearly family vacation on speakers, I thought I'd build some.

I have a bunch of stuff laying around, and I thought I maybe could use them. After reading, I discovered that the high end monitors rarely use high end speakers, they are more engineered towards a flat frequency response.

So I will try to use some of the parts I allready have, the object here is to get the best out of what I've got.

I have a bunch of woofers 8" with the following specs:

Frequency Response: 42 - 5000hz
Recommended crossover: <3500hz
Impedance: 8ohm
Sensitivity: 87db

A couple: 20mm Dome Tweeter

Resonany Frequency: 2200hz
Frequency response: 2000 - 45000hz
Minimum Impedance: 5.7ohm

So how do I go about designing a crossover for these two components?

I also have a selection of chip amps. I was thinking of putting in two TDA2030s in a sort of bi-amp'ed design, or is it better to do a passive crossover and build a power amp into the cabinet?

Thankful for any input,

DocZ

 

[richie00boy]

Sorry but unless you have equipment such as decent measurement mic the project is a non starter. Also from the specs you have given I doubt those are very good quality drive units, need proper Thiele-Small parameters and frequency response graphs.

You are correct that you would be best off building an active crossover with amp for each drive unit.

 

[docz]

Yeah, I gathered as much, but anyways, it would be nice to build them and see what the result would be, who knows I might get lucky. Worst case I might end up with a pair of relatively nice PC speakers.

I have never built a cross-over before, should I buy a ready made one? Or is it a simple task that I can read myself to completing?

DocZ

 

[Xeentje]

Never EVER go off of ready-made x-overs!
Especially for such a project, that has to have the MOST ACCURATE reproduction, it is important to have an x-over built to spec that takes driver and enclosure into account. With a ready-made one you'll never have this because they don't take driver-specs into account and they don't know what cabinet you'll be using to house the drivers. So those x-overs will never help eliminate negative influences!

What you need is driver T/S, simulation progs, measuring gear, interpretation- and tuning skills...
If you don't have at least those: Don't even think of starting such a project!

 

[richie00boy]

Crossover design is complex, but going active makes it one step easier as you can forget about driver impedance curves.

What is it that the monitors brought out that the headphones don't? Is it possible you could just buy some better headphones?

 

[Xeentje]

Headphones are a somewhat direct injection whilst (nearfield) monitors will be more accurate to what it will sound like in-room, which can give a whole other frequency-response to the human ear.

I think that's where headphones come short

 

[docz]

Ok, hehe, I didn't mean to hit anyones nerve or anything. I know that I do not have the skill - nor do I have the ambition to create a high end professional studio quality monitor. It was never my intention to claim that designing such high end products are a trivial affair. If you got that impression, I am truly sorry.

What makes me want another monitor source other than the headphones are two things:

1. Mixing my bass and kick tracks. The headphones really trick me, not only the amount of low frequencies in the mix, but also the tone of the instruments. Whenever it sounds great in the cans, they almost always sound way off in my car or regular hi-fi systems.

2. The stereo image is also off on the cans. And hard to get right. As it never sounds the same way as it does on a pair of stereo speakers. I guess it is because the cans really create two separate listening "rooms" and you don't get the same stereo perception as with two speakers infront of you.

I know I probably should go out and buy a set of decent monitors, but I thought it would be a fun project, and I would probably learn a lot from it. But if it really requires a bunch of special equipment and tools, then I guess I'll leave it alone. But still it would be fun to hear what I could accomplish with the spare parts I have laying around.

So let us forget about the "pro studio monitor" aspect, and move onto how I could make some powered speakers out of what I have.

So let's start with the crossover, I'm guessing a crossover is basically a HPF and LPF?

How do I determine the crossover frequency? Do I use the one that the woofer states is the ideal frequency? Or do I calculate it somehow? Since the tweeter's resonant frequency is about 2k, should I aim more towards that frequency? What is better? Tweeter twitting out mids, or woofer?

DocZ

 

[Brian Oshman]

Cans should never be used for mixing. They produce a false sense of imaging because your opposite ear cannot hear what the other one hears like you regularly hear things. They also do not use surrounding objects and the room for reflected feedback.

Monitors do not need to be elaborate, you just need to be familiar with what they produce and how that translates to other systems. That just takes practice. Any monitor will do the job as long as you familiarize yourself with the responses and using program material that you are familiar with is a good way to start along with taking your mixes to other systems to compare. After a while you will readily be able to tell what the mix needs on those monitors and it will translate to the hi fi, the car, the computer, the transistor radio, etc... with reliable results.

 

[PeteMcK]

most people on this site tend to approach things from a perfectionist point of view... but you already have the drivers, let's see if they are usable. First step is to get the complete parameters; do you have them (what brand & model are the drivers?)?,
if not, make a simple jig, download ARTA, and measure them, it's quite easy:
ARTA ARTA Download
ARTA Jig - AudioBlog: A simple loudspeaker measurement jig for ARTA

 

[oldmanaudio]

You may be better off with using a plate amp like the dayton MCA3545 sold by partsexpress. This amp has 4 selectable crossover points and 24 db/octave slopes. Then you could use a simple spectrum analyzer with the right setup (outside) to try and get the best response. This would be much simpler and you are more likely to succeed, plus you can plug right into your mixer board taking away the need for a power amp to drive them.http://www.parts-express.com/pe/pshowdetl.cfm?&DID=7&Partnumber=300-775&ctab=1#Tabs

 

[docz]

That ARTA jig, looks cool. I think I'll start by building that.

But a couple of questions, that I couldn't make out from the schematic:

1. I guess one of the RCA sockets is to connect to the LINE OUT of the soundcard? Where do the other two RCAs go? Is it two from the LINE OUT, and one to the SPEAKER?

2. It says to use two stereo mini-jack sockets, these are TRS, do I connect the tip and ring together in the jig?

DocZ

 

[PeteMcK]

The circuit could be drawn better; there are two PLUGS, the top one wired mono goes to the line out (it doesn't matter if you use L or R, you can choose in LIMP setup, but I'd use the tip, but don't connect ring & tip), the bottom two are Left and Right of a stereo plug which goes to Line in.
The original designer may have used sockets, but that means you need extra cables, using plugs means fewer interconnects, & better connections.
I used a couple of crocodile clips to connect the speaker.