Getting an idea of the big picture

[Consul]

I got some great information out of the first thread I posted here, but I'm thinking I need to step back and evaluate my goals.

I'm currently building a small basement music studio (13 feet by 17 feet by 6.5 feet high, masonry walls, open-joist ceiling stuffed with fiberglass), which will naturally include a monitoring system. At this point, I'm still convinced I can build something better for cheaper than buying it. The problem, of course, is that speaker design is so exact and complicated that it could be it's own university degree.

Right now, I'm favoring most a system using full-range speakers. The reason for this has to do with the critical midrange - that range of frequencies between 200hz and about 2khz that holds the majority of musical information. If at all possible, I'd like to avoid crossing over anywhere in that range, except nearly every two-way design I've run across on the web does exactly that.

So, my thinking is, at the moment, to find a good, smallish full-range that covers 200-18khz nice and smoothly, and then cross over at 150-200hz or so to let a woofer fill in the bass. Also, I plan to soffit-mount these monitors, so they will for all intents and purposes have an infinite baffle. These baffles will be aimed in toward the mix position at 30 degrees, relative to the back wall, thus forming a 60-60-60 triangle between both speakers and the listener.

What would be cool is if I could find drivers that would mount right into the wall, no enclosure. The area behind the baffles could be stuffed with fiberglass to accommodate this. I would most likely do a modular design, with the drivers themselves mounted on a piece of MDF, which then plugs into the wall.

So, my question to all of you is, am I onto something, am I off my rocker, or should I stop trying to play a big boy's game and go back to my tinker toys?

As an aside, I'm experienced with electronics and design, and am currently an engineering student, so you don't have to dumb things down for me too much.

Thank you all for your time.

[Geoff H]

I think you are onto something. Setting the monitors into a masonry wall will provide a solid bafle, less colouration in the critical midrange. There are plenty of drivers that will work in less than a cubic foot of enclosure. There is an advantage in pushing the system resonance up a bit in that application.

Look for something with a higher efficiency, they tend to be better on transients, and it wouldn't hurt to port the enclosures. That will provide less cone movement when bass gets in, even though it will be down a fair bit.

I haven't heard them, but from what I have read the Fostex range should have something suitable. The drivers for a foldback system would also be suitable. JBL comes to mind.

Think about brick enclosures for the bass, placed under the uppers. I would start with JBL there.

[Consul]

Hrm, I guess I could've been clearer. The soffits won't be masonry. That's just what the walls of the basement happen to be made out of. The soffit will most likely be gypsum board and 2x4s, like any other wall.

Although the idea of making brick soffits is intriguing.

I've posted this pic before, but this is an idea of what I have in mind:

http://img174.imageshack.us/my.php?i...tstudiohf1.jpg

(Ignore the fact that I drew the speakers as MTM for the moment. Also, the side treatments are not going to look like that. I really need to update this drawing.)

Thank you!

[planet10]

I've put a pair of CSS FR125 miniOnkens into a monitoring environment with good success. The same driver could be mounted in a sealed cavity in the wall.

dave

[Consul]

Of course, frequency response is only part of the picture for critical listening. Transient response and damping is a large part as well. I've noticed that most speaker makers don't even publish those waterfall graphs that show that kind of information.

As far as I can tell, paper cones with a big magnet are my best bet. At least, that's what I've been able to divine from what little is out there.

[Consul]

Oh, hey planet10. We posted at the same time.

Yeah, I ran across those FR125's while surfing around, and they look pretty damn close to what I'm after, at least from what I can gather on the spec sheets.

[planet10]

The FR125 don't have as magical a midrange as the similar size Fostex, but do have a very flat FR (where the Fostex -- at least unmodified -- are a bit more challenged), and work well in a sealed enclosure (should be smaller than what you have illustrated (10-13L)), and are quite tolerent of amplifier sonics (but do prefer a nice SS PP amp -- ie most of them).

The FR125 is somewhat limited efficiency & level wise but if you are going to cut them off at the bottom that will go a long wasy to ameriolating that issue.

dave

[Consul]

Thanks! Actually, I don't think level will be much of an issue, since this is such a small room to begin with. I'll likely be bi-amping a full-range with a woofer using an active crossover. I'm just out to get the most accurate sound I possibly can, and I just have this suspicion that the right full-ranger can really help me there.

As for a cabinet, well, mounting raw drivers right into the wall would be nice and easy, but if I have to hang a cabinet behind the soffit, I will. That's not a problem.

[planet10]

Originally posted by Consul
As for a cabinet, well, mounting raw drivers right into the wall would be nice and easy, but if I have to hang a cabinet behind the soffit, I will. That's not a problem.

I suspect there will be framing behind those soffits, so a subenclosure using that framing wouldn't be too hard -- the rest could be used for the woofers.

dave

[ScottG]

With this sort of configuration you have several issues..

1. Acoustic Resistance w/ insulation.. Generally not a good idea with paper drivers unless the material is at least 5 inches away from the driver. Increasingly harder/thicker materials seem to be less effected by this.

2. Flat on-axis response.. The driver you use here should be flat on axis with a good off-axis response.

3. Absoprtion with the reflection between the drivers, particularly for higher freq.s. Obviously here you have shown an absorber behind your monitor. Note that it may NOT be advantageous to have absorption panels to the out"sides" of the speaker.

Now issue #1 suggests a non-paper driver UNLESS you can deal effectivly with the insulation batting. IF not I'd suggest looking at a woven driver like carbon fiber of glass fiber OR a doped paper design. This suggestion "bridges the gap" subjectivly between a paper driver and something like a aluminum/magnesium driver, while still providing a driver less sensetive to acoustic resistance.

#2 is FAR more limiting.. flat on axis designs are tough to come by..

Most expensive to least expensive:
http://www.madisound.com/pdf/scanspeak/12m_4631g00e.pdf
http://www.madisound.com/pdf/audax/hm100c0.pdf
http://www.madisound.com/pdf/seas/h1262.pdf
http://www.madisound.com/pdf/vifa/mg10md09-08e.pdf

At least from the graphs here the least expensive (the vifa) is actually the most linear..

Now there is no way to say which driver will have the best subjective response in this application, but its likely that the Scan Speak has an "edge" here (at a MUCH higher cost). Still, I'd bet that the vifa is pretty good.

There are of course other drivers like the HiVi B3S and the Aura NS3, but these are decidedly less efficient (Tangbands seem to straddle the eff. topic between the two types of drivers, BUT are often a bit less linear than their graphs would imply). (Note that the expensive drivers from Jordan and Bandor are more like the paper drivers, so they are not included because of their "sensetivity" to acoustic resistance.)

IF it were me - I'd prob. pick the Vifa driver for this application OR a good coaxial driver with an appropriate crossover (..but that costs considerably more).

http://www.madisound.com/cgi-bin/ind....3480&pid=1961

http://www.bmspro.info/photos/bmspro...BMS_5CN140.pdf

http://profesional.beyma.com/ENGLISH/producto.php
the 8BX

http://www.radianaudio.com/products/...iewC=8_ceiling

Of these the easiest would be the seas - its more linear. The most difficult would prob. be the radian, BUT it quite possible would provide the best sound. (..give and take and all that.)

For simplicity sake then the Vifa is a "no-brainer", and probably the best overall choice for this application.