How to connect M-audio BX5a to your computer soundcard audio interface

M-audio BX5a is one of the best reference monitors that a beginner home studio engineer can afford.

This tutorial will illustrate two ways on how you can connect M-audio BX5a to your computer. The first method is regarding the use of PCI soundcards or on-board soundcards with M-audio BX5a. The second method is a more recommended which is to connect the BX5a to an external audio interface such as USB or Firewire audio interface.

Requirements in Connecting M-audio BX5a to PCI Soundcard

This is rather tricky especially for beginners. Most consumer PCI soundcards includes only one TRS stereo output (1/8 inch TRS jacks) commonly green such as #3 port shown below:

Well if you have PC speakers or headphones it will be very easy to connect since they only have one connectors going to the soundcard output. But things will be different with M-audio BX5a reference monitors to your computer. First, M-audio BX5a is a two-unit speaker system with each speaker has its own TRS/TS input (or even power supply). See below:

To connect the two units of BX5a to a single stereo output of your PCI soundcard; you need to buy the following connectors, cables and adapters to complete the connection:

1.) 2 pieces of TRS 1/4 inch male to RCA female adapter (one for each BX5a unit):

2.) One piece of Y cable (Two RCA male to single TRS 1/8 inch male):

Take note this is a Y cable, on the other end are two RCA male jacks while on the opposite end is a single TRS 1/8 inch jack. Select a high quality audio cable.

Final Steps to connect M-audio BX5a to PCI soundcard

1.) Connect the RCA male jack of the Y-cable to the female RCA jack of the adapter. This is how it looks like after joining these connectors:

Do the same for the other RCA male jack in the Y-cable. As a result the Y-cable is now converted to two 1/4 inch TRS jack male plug to a single 1/8 inch TRS jack male.

2.) Now you are ready to connect them to your M-audio BX5a and computer soundcard. First connect the TRS 1/4 inch male to the back of the M-audio Bx5a. Do the same for the other BX5a unit.

3.) Finally connect the 1/8 inch TRS jack to the back of your soundcard stereo output. You have successfully connected M-audio BX5a to your computer PCI soundcard.
4.) Plug the computer power to AC.
5.) Plug the M-audio BX5 to AC power. (Warning: Read the manual for safety instructions)
6.) Turn on your computer (boot). (Do not yet turn on BX5a).
7.) After the OS booting has been stabilized and turn on both M-audio BX5a unit. Turn the volume level at the back of your monitor to around half (50% maximum).
8.) Play some music and turn the volume level of your computer audio player to some reasonable volume. The BX5a should be playing the music.

Connecting M-audio BX5a with Firewire or USB Audio Interface

This method is much simpler make sure you have:

a.) Two pieces of 1/4 inch TRS male to 1/4inch TRS male cable (one for each M-audio BX5a unit)

Procedure to connect:

1.) Plug one end of the 1/4 inch TRS male jack of the cable to the back of M-audio BX5a unit.
2.) Plug the other end of the 1/4 inch TRS male to one of the audio interface main monitor output.
3.) Do the same for the other unit. In screenshot, see it below:

TIP: How to connect speakers to amplifier correctly and prevent damage?

This is an important tutorial on how you will connect speakers to your amplifier correctly and prevent any damage. First, you should know some basic electrical theory behind connecting speakers.

Introducing the Speaker Impedance Rating

One of the most important electrical characteristic of speakers is the impedance. Actually think of impedance as the opposition to electrical current flow. You should keep in mind the total impedance of your overall speaker system when wiring them. The speaker impedance rating is included in the speaker specifications. Since most speakers are rated at 8 ohms impedance, it is not safe to assume that all speakers have 8 ohms impedance rating. You should take a look at your speaker manual that list the impedance specification. For example one of the best PA speaker systems available; the Behringer Eurolive B215XL 1000-Watt 2-Way Pa Speaker System has the following impedance specification listed on its manual:

Thus it is shown to be in 8 ohms. On the other hand, car speaker systems tends to be rated at 4 ohms much lower than those commonly used in home studio PA speakers. In stereo speaker system, you will be using 2 speaker units each rated at its specified impedance rating. In large speaker implementation such as in concert venues and live shows, you might be using more than 4 speakers to 8 speakers connected to your amplifier. To give you a quick background about connecting amplifiers, mixers and speakers together, see a sample schematics provided by Behringer:

As you can see, it all starts with the audio mixing console. The mixing console conditions the audio input sources and the sound engineer will be adjusting settings to provide the best sound possible in the output. This audio input sources could be musical instruments of the live performing band or the microphones from the choir. Then the stereo output of the mixing console is then feed to a power amplifier which will apply a gain strong enough to be reproduced in loudspeakers you commonly see in concert venues and live stage shows. Finally the output of the amplifier is then feed to the power speakers.

Two ways how you can connect speakers to an amplifier

The impedance of the overall speaker system depends on the type of speaker connections. There are two ways how you can connect speakers:
a.) Series connection – connect the negative (-) terminal of one speaker to the positive terminal (+) of the next speaker until the entire speaker will be connected.

As you have observed, there are only two speakers in series. The negative terminal of 1st speaker is connected to the positive of the second speaker. But if you have three speakers in series, connect the positive to the negative, and vice versa.
b.) Parallel connection – connect all the positive and negative terminal of the speakers directly to the amplifier output (+ and -). This is probably the simplest way to connect speakers.

Image credits: Home Toys

Computing Speaker Total Impedance

According to Ohms law, the total impedance of speakers (Zt) connected in series is computed by:

Zt = Z1 + Z2 + Z3 +Z4 . . .

You simply add up all the impedance rating of all speakers in series. It is why in the above example of a series connection; the total impedance is 16ohms because:

Zt= Z1 +Z2 = 8ohms + 8ohms = 16ohms

In parallel circuits, the computation for total impedance (Zt) is using this equation:

1/Zt= (1/Z1) + (1/Z2) + (1/Z3) + (1/Z4) . . .

Using the previous parallel connected speakers:

1/Zt= (1/Z1) + (1/Z2) = (1/8) + (1/8); solving for Zt = 4 ohms

Observation: Connecting speakers in series will increase the overall impedance as seen by the amplifier. But connecting speakers in parallel will decrease the overall impedance.

Designing your speaker system and keeping it within safe limits

It’s tempting to rush by connecting your speaker systems in either series or parallel without ever looking at specs/manual. If you are lucky, you won’t have a problem but if not; it will permanently damage not only your speakers but your amplifiers as well. The common cause is “overloading”. This is characterized by excessive current flowing to the amplifier and speaker circuit. This mostly will happen if you connect speakers in parallel. It is because as you increase the number of speakers connected in parallel, it will significantly reduce the overall impedance as seen by your amplifier. If the impedance is reduced, electrical current will increase. Therefore in parallel speaker connections to your amplifier; you need to take note of this guideline:

Zt > Amplifier Minimum Load Impedance

The above equation means that your overall speaker impedance in parallel should be greater than the amplifier minimum load impedance (which you can see in the amplifier manual/specifications). If the amplifier is rated at a minimum load impedance of 2 ohms, then you should not connect speakers in parallel in such a way it will drop lower than 2 ohms. It should be more or give it a safety factor. Also in series speaker connections, this is a safe guideline to start:

Zt < 16 ohms

Some amplifiers are not designed to handle greater than that, so better check the amplifier specifications before you can increase the loads. The following are the advantages of connecting speakers in parallel:
a.) Maximum speaker acoustical output (subjectively “loud”) can be obtained because the power is not divided among speakers.
b.) Easy to connect and setup

The advantages of connecting speakers in series:
a.) Safe from electrical current overloading, because the total impedance is summed up. It will always be greater than the amplifier minimum load impedance.
b.) You can limit the power output to the speakers because low current is flowing in the speaker circuit (because of increased impedance). Limiting the power will decrease the acoustical power output of your speaker. This will put less stress to your amplifiers (and also speakers) because it is not heated and delivering high current unlike in parallel connection. As a designer, you can connect speakers with a combination of series and parallel and keeping in mind the guidelines mentioned previously.

Content last updated on October 13, 2012