SoundEasy measurement box – build guide
How to make a SoundEasy measurement box / rig ?
Having a SoundEasy measurement box will make things much easier when taking impedance and SPL measurements. I made a probe build before, but I found its build quality flimsy. Also, it took a bit of effort when switching between impedance calibration, measurement and SPL. Making this box will require some extra components, terminals and connectors. As a result, it will be more costly, but if you use SoundEasy a lot, it will make sense.
The box will feature 2 XLR ports which you will connect to the sound card (you can use any type of connection here). Additionally, there will be 2 banana plug connectors for the amplifier, and 2 banana plug connectors for the speaker. On the other side, we have 4 switches. These will be used to switch from one setting to another, without disconnecting cables.
Let’s take a look at the circuit diagram. I tried to make everything as clear as possible. We will get to the actual build in a moment. But try to look at the diagram, and imagine that the connectors are on one side, and the switches are on the opposite side. The schematic tries to emulate how it will look like in reality (not just an electrical overview). I used different colors for the wires, so you can easily follow them and don’t mix them up.
The switches are ON-ON switches. I wrote in orange the different functions they switch between. There is no real purpose for this in an electrical diagram. However, it does make things a bit clear on how it works. More on that later.
What’s important to know is that this schematic will be the baseline. After that, everyone can build the box how they imagine it and with whatever they have available. You can use different connectors, solder cables, crimp cables, use a circuit board. It’s up to you, how fancy you want to do it. In what is about to follow, I’ll show my vision on it.
List of components
I’m going to link every components which I used and the tools you are going to need. Some components will not be the same as I used exactly, but it will be an equivalent. So here is the list of components you will need :
- Electrical box.
- Resistor 47 kOhm – 2 pieces.
- Resistor 22 kOhm – 2 pieces.
- Capacitor 20 uF – 1 piece. (I used 18 uF because it’s easier to find, cheaper, and offers better protection).
- Resistor 10 Ohm – 1 piece.
- XLR female connector – 2 pieces (personal preference / other connectors can be used).
- Banana plug – 4 pieces (2 pairs).
- Banana terminal socket – 4 pieces (2 pairs).
- ON-ON toggle switch – 4 pieces.
- 1.5 mm / 16 AWG wire – several meters.
- 3-way connector – 2 pieces (optional).
- Wire crimp connectors – few pieces (optional).
- Ground bar – 2 pieces (one with 4 terminals and one with 6).
Tools used :
- Power drill.
- Step drill bit.
- Cable stripper (optional).
- Crimping tool (optional).
- Soldering iron.
- 3 mm drill bit with equivalent bolts and nuts to fix the XLR connectors to the box.
- 8 mm wrench – for the switches and banana connector nuts.
- 6 mm wrench – for the XLR connector nuts (your mileage may vary).
- Plastic adhesive.
Step 1 – Cutting holes
The first thing to do when building your own SoundEasy measurement box, is to cut the holes for the different connectors. There are 3 types of holes : the ones for the banana connectors and switches (same diameter), for the XLR connectors, and for the bolts of the XLR Connector.
To make these holes, I suggest using a step drill bit.
My advice is to use some electrical tape, so you know when to stop :
- 6 mm for the banana connectors and switches.
- 26 mm for the XLR connectors.
- Normal 3 mm drill bit for the bolts that hold the XLR connector.
Before drilling the holes, use a pencil and ruler to draw a horizontal line. Then, carefully mark the spots where you will drill. This will ensure that the connectors will look aligned and symmetrical.
After I drilled the holes, I realized that they are not placed like in the electrical schematic, but the other way around. I hope this backward positioning wont confuse you too much.
Step 2 – soldering the connectors
Solder the banana female connectors
This is the easiest one to do. Just solder a cable to the connector. Do the same for all 4 female connectors.
Solder the male banana connectors
Next solder a long cable to the male banana connectors. You will need one pair to connect to the speaker, and another pair to hook up the amplifier. Optionally, you can solder some alligator clips at the other end of the speaker wires. This way you can easily connect the speaker for measurement.
Solder the XLR connectors
The female XLR connector has 3 pins. If you look closely, they are numbered (1, 2, 3).
- 1 – Cable shield (ignore this one).
- 2 – Positive terminal.
- 3 – Negative terminal.
Solder two cables on pin 2 and 3. If you don’t have different color cables (like I do), make sure you use some black electrical tape on the end of the negative wire. This way you can tell each other apart.
Solder the switches
Now this is the hard part, which will need some explaining. I would also encourage you to use a multi-meter, to check the connections. You don’t want to solder the wires, only to find out that you mixed the pins up. Problem is that the switch has 9 pins. Only 3 of them are important.
The middle one is the negative terminal and either the top or the bottom is the positive terminal, depending on the switch position.
This is the polarity of the switch. Again, make sure you check it using a multi-meter. Set the multi-meter for Ohms and see if you get a reading. If you do, than those are the pins in question. As I wrote in the electrical schematic, the negative terminal is the “IN” and the positive terminals are the “OUT”s.
After everything is soldered, secure the connectors to the box, and it should look something like this :
You will need 2 pairs of matching bolts and nuts to secure the XLR connectors to the box. Furthermore, a tiny wrench is also needed to fasten the nuts snugly. For the banana connectors and switches nothing extra is needed. They are provided with a fillet and a nut already on it. Take it off, place it on the other side of the wall and tighten it up using a small wrench. Finally, our SoundEasy measurement box is starting to take shape.
Step 3 – Build the probes
To make things easier when building the probes, I used a 3 way connector and crimped the resistors to it. You can solder them or do as you see fit.
Make the necessary connections using the soldering iron and then tuck them wherever is more convenient.
I placed the first probe on the side wall.
The second one is placed somewhere randomly inside the box.
Step 4 – Connect the resistor and capacitor
Follow the schematic and solder the resistor and capacitor to the appropriate wires. For the probes I didn’t use any electrical tape. However, I placed the resistor and the capacitor pretty close together and I didn’t want to risk any short circuits.
I tucked them in a place I found convenient, which is under the banana connectors.
Step 5 – Hook up the ground bars
If you look on the schematic, there are 2 places where more than 3 cables bunch up. As a result, using ground bars will makes things a whole lot easier.
You will need one with 4 terminals and one with 6. I managed one with 4 and one with 8. Make sure they are not touching each other or the other components, and you’re gold. After setting this up, pretty much all the cables are connected. In conclusion, the SoundEasy measurement box is almost complete.
Next, you have to fix all the components in place using plastic adhesive.
Final step – put the lid on the box
Finally, all you have to do is to screw the lid on top of the box. Optionally, you can mark the switches and connectors using a permanent marker. And there you have it, the SoundEasy measurement box is complete :
How to use the box
Well, there are 2 types of measurements : SPL and impedance. Therefore, let’s discuss both of them.
For the impedance measurement you will need to have the following setup :
These are the connections you have to make. However, on the front panel the switches need to have a specific positioning :
- BOTH switches to impedance position (DOWN).
- The position for the Measure – Calibration switch is determined depending on what you want to do. First of all, you do the calibration and set it in the correct position. Secondly, you turn it up to “Measure” position and do impedance measurements.
- The last switch has no purpose when the first 2 switches are on the Impedance position. It has no effect, either up or down.
For the SPL measurement you need to unplug the 2nd probe from the sound card and connect the microphone there. You can leave the 2nd cable (that you just disconnected from the sound card) connected to the SoundEasy measurement box.
As for the switch positions on the front panel :
- First 2 switches on the SPL position (UP). Both of them!
- The next button Measure – Calibration is useless. Its position is of no matter when the first 2 switches are on the SPL position.
- The last switch, set it to TWT position (UP), when you are measuring a tweeter. This will protect the tweeter because it will filter the lower frequencies (which are irrelevant for a tweeter). Set it on the full position (DOWN) to make full range frequency response measurements. Therefore, the last configuration you will use for mid-range, woofers etc.
A SoundEasy measurement box will save you a lot of hassle when making a lot of impedance / frequency response measurements. In the absence of one, you will have to move around cables / probes. However, if you have one, you only have to flip some switches. Therefore, much more convenient.
In the end i want to compare the impedance measurement with another device to test for consistency. I measured a speaker in bass reflex enclosure, so you will see two impedance spikes. Here is the graph using the Dayton DATS :
And here is the impedance chart using the SoundEasy measurement box :
If you look at the graph they are almost identical. Within the margin of error. I marked the 1 kHz point on both graphs. You can see that the DATS graph shows 8.70 Ohms and SoundEasy shows 8.72 Ohms. I’m definitely pleased with the results. Have fun with your measuring contraption!
- Image source : link.