Floor Monitor Concept Plans
Rather than trying to give you a plan that is overly complex, I looked towards a simple design, including conceptual design logic, so you can get a feel for what is involved in building a usable floor monitor.
This design does not take into account any speaker parameters (not that many Floor Monitors are sonically designed, rather, they are functionally designed - as a result they are not very accurate - definately not flat frequency response, nor do they have exceptional bass response. However, these are not usually issues for Floor Monitors). There are many shapes of Floor Monitors, all have the same sorts of issues when designing them - allowing the people on the stage to hear the mix.
In this set of simplified plans, I have left a lot of details out, because, unless you are used to working with complex angles in wood, you might need to locate someone who has done it to help you. Someone with experiance in this area should be able to work from the plans shown and deal with the effects of having angles cut in parts of the wood. If you can see that there are cuts to account for, then its going to be simpler to make them.
The width of the cabinet (not shown on the drawings) is 20 inches. If you make it a little wider or narrower, its not that important.
The cabinet is sized for a 12 inch Musical Instument Speaker, and a Piezo tweeter - since you can use any Piezo tweeter that you want as long as it can handle 75 watts or more, I leave the diameter of the hole for the tweeter to you. Buy your tweeters before cutting the hole for it.
This set of plans shows a port. This is just a round hole cut into the speaker baffle board. I suggest 3 inches in diameter. This is here because the actual internal volume of this Floor Monitor is very small, and the Port will give you better bass response.
I don't advise using MDF (particle board). I suggest 3/4 inch plywood and 3/4 inch square pine bracing, except where angles are cut into bracing - there I suggest using 1 X 3 (actually 3/4 X 2 1/2) pine furring strips.
The Cut-Out is large enough to fit 2 of the 1/4 inch phone jacks side by
side, mounted to a metal plate that is screwed to the cabinet.
Aluminum or Steel mounting Plate
This side view shows the various angles that are needed, and should highlight
that you have to deal with them when the material is has angles on multiple edges.
Glue and screw the braces in place. The Speaker Baffle Board needs
to lay flat on the supporting braces (it will be screwed onto it).
Center the Speaker hole from top to bottom of the Speaker Baffle Board,
offset to the Right (as shown), leaving at least 2 inches of room on all sides of the Port
hole and Piezo.
The goal was to design the simplest possible Floor Monitor with the fewest odd angles in it. Why 50 degrees and not 45? If you have 50 degrees, you also have 40 degrees (if you flip it over onto its backside). More than 45 degrees is good when you have a small stage and you have to stand close to the Floor Monitor. Less than 45 degrees is good when you have a larger stage and the Floor Monitor is further away from you - often this allows each Floor Monitor to be used by more than one person. 5 degrees may not seem like much, but it can make a big difference. Some Floor Monitors are set to 60 degrees (or 30 degrees, depending on how you switch it around). I find 50 degrees quite effective.
To allow you to easily hook up 1, 2, 3 or 4 of these Floor Monitors, I suggest a 16 ohm 12 inch Musical Instrument Speaker, wired in this fashion:
Pick which ever your power amp can handle (make sure it can handle 4 ohms if you use 4 Floor Monitors).
The cable used is 18 or 16 gauge zip cord (not sheilded wire) with 1/4 inch Phone Plugs on each end. Other connector types could be used.
If you want to use a 10 inch Speaker instead of the 12 inch speaker, all dimensions remain the same, except the speaker opening (shown as 11 inches here) becomes 9 inches in diameter.
Paint the inside, underneath the Port, black - it looks better (I normally spray any place inside a cabinet that can be seen from the outside flat black).
Note: Add rubber feet (4) to the bottom of each cabinet.
If you use 8 ohm speakers, and you can only drive an 8 ohm (or higher) load, you will need to wire up your speakers in Series to be able to use these. Other combinations are still possible, however, they will require a bit of thinking and planning during setup. See: Speaker Wiring/Loading Examples for more information.
16 ohm speakers were chosen for simplicity of setup and use. There are many sources of these, an example would be Parts Express. Parts express also has other parts (Piezo, bolt down speaker grills for the woofer, connectors, etc).
You might want to cover this cabinet in indoor/outdoor carpeting after it is assembled. You might also want to add a carrying handle. If you do add a handle, don't put it on the back - doing so will restrict your ability to use the Floor Monitor as both a 50 degree (normal) or 40 degree (flipped on its back) Floor Monitor.
Steve Dallman writes
Piezo tweeters are seen by the power amp as a capacitor. Some power amps (such as Kustom)
can't handle a capacitive load. When that happens, the amp goes into thermal
runaway and it can take the amp out.
To remedy this, simply add a resistor in series with the piezo. The resistor can be anywhere
from 2 to 20 ohms and I'd suggest using at least 5 watts handling. I generally use
an 8 ohm/20watt from Radio Shack.
The resistor will not change the response of the piezo, and it will help protect
the piezo from burnout as well.
Piezo tweeters are seen by the power amp as a capacitor. Some power amps (such as Kustom) can't handle a capacitive load. When that happens, the amp goes into thermal runaway and it can take the amp out.
To remedy this, simply add a resistor in series with the piezo. The resistor can be anywhere from 2 to 20 ohms and I'd suggest using at least 5 watts handling. I generally use an 8 ohm/20watt from Radio Shack.
The resistor will not change the response of the piezo, and it will help protect the piezo from burnout as well.
NOTE: Floor Monitors really need thier own amplifier and level control. 100 watts of power at 8 ohms should be the minimum power you have available for Floor Monitors.
NOTE: All cabling and wire listed as a 'gauge' on this website is AWG. See the SWG to AWG conversion table to help translate if you use SWG gauges.
Questions? Comments? .
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