About yesitsdrew5310

Hey, Im Drew Brashler. I started learning live sound at the age of 7. Instead of going to sunday school class I would sit with my Dad at the sound board and help him mix at church. Later in life I decided to attend the Conservatory of Recording Arts & Sciences in Tempe, Arizona. I learned quite a lot from that school. Now I am a professional wedding, portrait and commercial advertising photographer and the lead audio engineer at North Ridge Community Church.

Exciting News!

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Hi everyone! Thank you so much for visiting and watching my videos on YouTube and reading my information here on this blog. I have so many exciting things happening in these next few months that I am BLOWN away!

After a 1 year break from making videos and posting on the blog, I am happy to announce that I will be making a completely new series of training videos on the Behringer X32. So if you haven’t already, head over to my YouTube Channel and subscribe to keep up on the latest videos!

Today, I am excited to announce the launch of my new website www.dbbaudio.com! Over there you will not only find my latest information and posts, but you will find a forum to ask questions and a form for contacting me directly! Signing up at the forum is super easy by using your Facebook or Google+ account!

Announcing www.dBBaudio.com

I can’t wait to see all of you over there and to help you out with anything you need help with! Thanks so much!


Drew Brashler

Behringer X32 Update

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I last updated about the use of the Behringer X32 digital sound board back in September.  So today I am reporting on its use and quality over the last 1/2 year.

The Behringer X32 is sold as a 32 channel digital board.  As you may know, at North Ridge, we switched from a 48 channel Allen & Heath ML4000 and that we have a mono pa system.  The X32 is secretly a 38 channel board.  This is due to the 6 additional “aux inputs” on the back of the board.  These show up in the “AUX IN/USB/FX RETURNS” tab of the console.  These aux inputs are a line level input and have a gain adjustment of +/- 12 dB.  Because our system is mono, I am able to sum the Left and Right outputs of our CD player and computer into mono to take up one channel each.  For some stereo systems, you may have to use an external sub console for combining your audio/visual needs into a single pair of Aux In’s of the board.  Some Kramer Video switchers include audio switching internally, so this is another valid option.

The two most common questions that I get about this console are:

  • How does the console sound?
  • How is the quality of the console?

The sound of the console is very clean and clear.  In comparison to our analog Allen & Heath ML4000, I much prefer the X32.  The transients seem a lot more clear.  I was able to notice the largest difference on the clarity of our choir during our traditional service.  I could for the first time hear the pronunciation of the words they were singing.

Equalizers on the console are beautiful sounding.  It takes very little adjustment of the gain to notice the adjustment you just made.  The 800×480 TFT display gives you a graphical representation of the EQ, which for volunteers who haven’t spent the last 5 years perfecting their ears to discern frequencies, really enjoy.  I have had a lot of techs come to me and mention that EQ’ing a channel is much easier to understand with the graphical representation of it.

The built in compressor and gate give you a good handle of the dynamics of each channel, in combination with sub groups you can keep a very consistant level out sound in your venue or house of worship.

As far as specs go, the delay of the console from the XLR input to the balanced outputs is 0.7ms.  This is one of the lowest delays in the industry.  At a sample rate of 48 kHz, it has a frequency range of 10 Hz to 22 kHz at 0 dB to -1 dB over the spectrum.  Lastly it has a typical analog input to analog output dynamic range of 106dB.

Next question is about quality.  I purchased two consoles, one for each of our main rooms at North Ridge Community Church.  Both consoles have been consistant and flawless with no apparent problems at all, aside from the accidental routing issues from time to time which is a operator problem ;-).

The faders on the console are very solid feeling and the motion is very fluid.  Rotary knobs do not have a lot of slop and are a good size for fingers.  Changing pages on the console from channels 1-16 and 17-32, all of the faders flip very quickly and accurately.

Overall, I am extremely satisfied with the purchase of our two X32’s.  Training has been aided with my YouTube videos which can be found at http://www.youtube.com/kd7qcu.  Any sound tech that has mixed on an analog console can be brought up to speed on the X32 in about 30 mins to an hour.

Would I purchase it again?  YES!  In fact with the new X32 Producer is a rack mountable version!  So, I would love to upgrade our mobile system to have this.  Please let me know if you have any questions.  Also if any of you are in the Phoenix, Arizona area and would like a hands on tour of the X32, drop me an email and we can set up a time.

Wireless Microphone Antenna Distribution on a Budget – Continued

WE HAVE MOVED! Please navigate to the current article links below to see the latest from dBB Audio!

  1. Wireless Microphone Dead Zones?!
  2. DIY Wireless Microphone Antenna Distribution – Antennas
  3. DIY Wireless Microphone Antenna Distribution – Introduction
  4. DIY Wireless Microphone Antenna Distribution – Part 2

In continuation to my previous post, I will start discussing how I solved the wireless distribution at my church in an economical way.

One of my many hobbies include amateur radio, which is the personal & experimental use of specific radio frequencies established by the FCC.  My callsign is KD7QCU.  Basically, I am a big nerd of radio stuff.  I get to talk to people all around the world with my radio and antennas outside of my house.  It is quite a fun hobby and our technological age with regards to RF has a lot to thank the amateur community for experimenting with radio.

This is me at the top of my ham radio tower that I purchased.

This is me at the top of my ham radio tower that I purchased.

I figured in my mind that because TV and the wireless microphones share the same frequency spectrum, some of the tv splitters might work the same with wireless microphones as they do with TV.  Thus we find ourselves looking at a two-way coaxial splitter.  This is something that you would connect your TV antenna to on one side.  Then the outputs would go off to your different TV’s allowing multiple TV’s to get the same signal.

The coaxial splitter uses transformers or different combinations of resistors to split a signal to its separate outputs.  Being that TV’s don’t transmit themselves, only receive signal, you can hook as many TV’s up as you want without causing harm to a television.  Wireless microphone receivers do not transmit either, they only receive.  So we can treat the wireless microphone receivers the same as TV’s.

I conducted a series of tests using the RFExplorer handheld RF spectrun analyzer.  This analyzer has a 50 ohm SMA antenna port on it, so to connect the antennas up to it, I needed some adaptors.  There was a SMA to BNC adaptor placed on the unit.  Then from there I used a length of LMR 200 coax to connect into the different devices in test.  A transmitter was placed onstage with a sine wave being played into it.  This assured even signal transmission levels as the level did not deviate in amplitude.

Screen Shot of the RFExplorer Spectrum Analyzer

First, I need to talk about an important unit, the dBm.  This is the power ratio in decibels (dB) of the measured power referenced to one milliwatt (mW).  dBm is a common unit for displaying signal strength.  -73 dBm is an “S9” signal strength on an S-Meter on a common ham radio.  Most 801.11 wireless network receive strength is between -70 dBm and -90 dBm with a maximum signal of -10 dBm to -30 dBm.

My first test was to test the signal strenght of a SLX body pack at different distances to see the dBm level.  I plugged in a Shure 1/4 wave vertical antenna into the RFExplorer for the test.  This is the stock antenna that Shure ships with their wireless systems.  I then measured the following levels at 3 different distances.

  • 10 feet = -30.5 dBm
  • 25 feet = -41.5 dBm
  • 50 feet = -52.0 dBm

The purpose of this initial test is to see how much signal should be going into the receiver at a max setting.  I would presume Shure would make their receivers work with the transmitter right next to it, without overloading the receiver.  Taking this presumption, I can now say that -30.5 dBm would be a good maximum receive strength to have at the receiver without causing any overload of the receiver.  So in any of my testing I am wanting to make sure the receiver does not receive any more signal than -30.5 dBm.

My next test would involve connecting the spectrum analyzer up to the stock antenna and Shure UA221 splitters which we use at North Ridge Community Church.  The purpose of this test is to see the effective signal that the SLX receivers are getting from a microphone on stage.  The arrangement of the setup you can see in this photograph below, it is part of the Shure dual side by side mounting kit, which uses two UA221’s to split two antennas off to the two receivers.  Note where the antenna is located, next to metal.  The signal strength read -68 dBm.

This is how the dual mount SLX receivers look on the front. Note where the antennas are mounted.

This is how the dual mount SLX receivers look on the front. Note where the antennas are mounted.

After this test I decided to test the signal strength in the same configuration, but moving the 1/4 wave vertical antenna into open space, meaning nothing around the antenna.  The measured signal was now -56 dBm, a +12 dB boost.  The reason for this is that the metal from the rack and mounting hardware of the SLX receivers was affecting the antennas ability to receive.  Much like a tuning fork, antennas will resonate at certain frequencies, when metal gets near a tuned antenna, it will start to change the frequency that the antenna resonates at or change the impedance, both of which will affect signal quality, normally in a degrading way.

I was able to source a ham radio operator who manufactures antennas out of printed circuit boards.  His callsign is WA5VJB.  One of the antennas that caught my eye is a 400-1000MHz Log Periodic antenna.  This type of antenna is directional, high gain and has a wide bandwidth.  Also the 400-1000MHz has our wireless frequencies falling in that range.  Shure sells a similar and more polished version of this antenna, they paint theirs black, add a mount to it and sell it for $200-$300.  It just so happens that the WA5VJB log periodic can be grabbed for $25 off of his eBay store.  The antenna comes with a spot for an SMA connector to be soldered onto the antenna.  To complete the system, I needed to get an SMA to BNC adaptor cable which was sourced for $10-$15 off of eBay.

Log Periodic Antenna

Log Periodic Antenna

My next project was testing the Log Periodic antenna with the spectrum analyzer.  I setup my test again with the sine wave into the transmitter and placed that onstage.  The measured signal level came in at -43 dBm.  This is a +25dB gain over the stock 1/4 wave vertical mounted in the rack.  This antenna was attached to a clamp using a spring clamp, better results would be yielded if I removed the metal clamp and used a non-metalic mounting system.

Now that we have an antenna that yeilds better results than the stock 1/4 wave vertical, I want to be able to split this signal out to the different receivers.  When you split a signal from one to two you will have a 3dB or more drop in signal.  When you start splitting the signal to more devices you will have more dB loss.  This is one reason I wanted to have a high gain antenna like the log periodic, to be able to have enough original signal to split to the 7 receivers.

There are two main types of Coaxial Splitters, active and passive.  A passive splitter will use transformers and/or resistors to split the signal.  An active will split the signal using powered circuitry and most of the time add a small signal amplifier to boost the signal.  My first series of tests were to see if a passive two way splitter would produce the same results as the Shure UA221 splitter.

SVI SV-2G Two-Way Coaxial Splitter

I sourced a SVI SV-2G two way passive splitter with a bandwidth of 5-1000MHz.  One issue is that the TV Coaxial splitters use F-Connectors, and most of the wireless products in the audio industry uses BNC.  I decided to use an adaptor from F-Connector to BNC for the tests.

I attached the 1/4 wave stock antenna from Shure to the antenna port of the splitter.  I then tested both outputs of the splitter and measured an expected 3.5 dB loss (the specs called for a 3.5 dB loss).  The interesting thing is that the Shure UA221 measured a 4.0 dB loss.  By these measurements the SVI coaxial splitter outperformed the UA221.  I also listened to different audio coming through the wireless system to make sure that no audio degradation was present.  No distortion or degradation was present on the signal.

SVI SV-3BG Three-Way Coaxial Splitter

Next, was to test a three way splitter.  The SVI SV-3BG, same bandwidth of 5-1000MHz and an expected loss of 6.0 dB.  After connecting and testing the three way splitter, I found the same expected loss as detailed on the unit.

PCT-MA2-4P Four-Way Active Coaxial Splitter

After testing both the two way and three way passive splitters, I wanted to test an active splitter.  I found a 4 way PCT-MA2-4P active coaxial splitter, this requires a DC power source at 12-15v at 300mA.  The spec’ed gain is +8dB.  I connected and found the expected gain of +8dB.  I also tested audio quality and found no change compared to the UA221.

I wanted to go into further testing of the amplified version compared to the UA221.  I was worried at first of the amplifier inside of the splitter adding in noise.  I attached the log periodic antenna to both the Shure UA221 and the PCT-MA2-4P and tested signal strength, noise floor level, and then calculated the signal to noise dB difference.  Here is what I found:

Log Periodic into UA221

  • Signal Strength: -46 dBm
  • Noise Floor: -94 dBm
  • Signal To Noise: 48 dB
  • Gain Compared to 1/4 Wave rack mounted Antenna: +22 dB

Log Periodic into PCT-MA2-4P

  • Signal Strength: -36 dBm
  • Noise Floor: -88 dBm
  • Signal To Noise: 54 dB
  • Gain Compared to 1/4 Wave rack mounted Antenna: +34 dB

Not only did the PCT-MA2-4P allow the connection to twice the amount of devices, but also outperformed in the signal strength and signal to noise measurement.  Comparing the signal strength of the amplified PCT-MA2-4P (-36 dBm) to the SLX transmitter at 10 feet (-30.5 dBm) has this still in a safe range for not overloading the receiver.

At this point, I knew this was promising!  The use of inexpensive television coaxial splitters was a formidable option for wireless system antenna splitting.  I am going to lead this post to an end.  In the next post, in the following weeks, I will show you the application of using an 8 way active coaxial splitter in a wireless microphone system.  Please if you have any questions, feel free to leave me a post below.

P.S. Some of you may argue that the TV Coaxial splitters are 75 ohm and that the conversion of a 50 ohm antenna to the 75 ohm splitter back to the receiver looking for a 50 ohm load will apply more loss than I measured here.  While yes you do have a bit of loss from the conversion of 75ohm to 50ohm (less than a dB of loss), the spectrum analyzer, just like the wireless receiver has a 50 ohm connector on it.  So any losses created by the 75-50 ohm conversion would be already calculated in my tests.

Wireless Microphone Antenna Distribution on a Budget – Introduction

WE HAVE MOVED! Please navigate to the current article links below to see the latest from dBB Audio!

  1. Wireless Microphone Dead Zones?!
  2. DIY Wireless Microphone Antenna Distribution – Antennas
  3. DIY Wireless Microphone Antenna Distribution – Introduction
  4. DIY Wireless Microphone Antenna Distribution – Part 2

The microphone is an essential tool to an audio engineeer, being able to reproduce a sound wave into an electrical current created the ability to use a audio reinforcement system.  In 1953, Shure Brothers designed and marketed a “Vagabond” system which dates to be the the first wireless microphone system for performers.  This system claims to have a range of approximately 700 sq ft, which equates to 15 feet from the receiver.  Shure Brothers is now called Shure Incorporated, which many of you use in your venue or house of worship.

Wireless microphones in a house of worship make services and productions very clean with no wires onstage.  Added to the cleanliness, you also have the ability to move around stage without getting tangled wires.  Some disadvantages with wireless microphones, appear when they start receiving radio frequency interference.  Some things like Radio Frequency (RF) signal gain, intermodulation distortion and receiver desensitization can wreak havoc on the audio coming from a wireless microphone.

Today, I am documenting a long experiment of mine, designing a wireless microphone RF distribution system at low cost.  When a venue has multiple wireless receivers, one will deploy a antenna distribution system to use one antenna for multiple receivers.  By doing this, it will reduce the clutter in an audio rack.  Also, the use of a high gain directional antenna can be employed to reduce the possibility of interference from other RF sources.

As you may know, most of the wireless microphones share the same frequency spectrum as the over the air television stations.  This includes VHF, Very High Frequency (30-300 MHz), and UHF, Ultra High Frequency (300-1000 MHz) as the main two.  To add to this, the digital TV transition that started in June of 2009 has reduced the available frequencies in that spectrum.  You can read more about this is my earlier blog posting which explains the differences between digital TV and analog TV and how they are laid out in the 6MHz allotment inside their channel.

With wireless systems, you need to first select a good frequency for your system to operate on.  At my church, North Ridge Community Church, we use the Shure SLX microphones with the H5 Frequency Band (518-542 MHz).  This occupies over the air television channels 21-27.  One of the main areas of problem in that frequency range lay in channel 24 (530-536 MHz).  Channel 24 in Phoenix, Arizona is home to KTVK-DT aka 3TV which uses a 1000kW transmitter.  Because this station is so powerful I have programmed our wireless channels to be outside of this spectrum range.

Here is why, when channel 24 is pulled up on the spectrum analyzer inside our building where our receivers are located, the measured signal strength is -69 dBm.  Outside our building it is about -48 dBm.  The signal of a SLX handheld up onstage measured to our receivers current location is -68 dBm.  If a wireless pack was to use the same frequency as the 1000kW TV station, the TV station would overpower the wireless pack.  Which would make your receiver have a lot of issues passing clean audio.

The main problem churches/venues will run into is interference from situations just like the KTVK-DT transmitter. So, before going and spending money on higher gain antennas, wireless antenna distribution, coax, or new wireless systems, please check your local TV stations and how they match up with your wireless frequencies.  A good place to start if you don’t have a spectrum analyzer is www.tvfool.com.  You can input your address and see what television stations you will receive.  Also check http://en.wikipedia.org/wiki/North_American_broadcast_television_frequencies to translate the television channel into the frequencies in MHz.

The best tool to have is a Radio Frequency Spectrum Analyzer, I purchased my church a RFExplorer handheld spectrum analyzer which views the frequencies 240-960 MHz.  There are add on boards which allow you to view 15-2700 MHz which includes WiFi frequencies.  Using this tool will aid in finding specifically if your church/venue has any interference issues with RF.  You can purchase this tool at: http://www.seeedstudio.com/depot/rf-explorer-model-wsub1g-p-922.html?cPath=174.

Place your wireless systems on frequencies that do not currently have anything transmitting.  If you find yourself with lots of interference, place your wireless systems where there is the least amount of signal.  Placing the wireless system over the lowest power television station is a valid option if you have no other open spaces.  The Federal Communications Commision, FCC, is who allocates the radio frequency spectrum and allows the television stations to occupy those frequencies.  It is said that they allow at least one 6 MHz chunk in every city free for alternate use such as wireless microphones.

Now that you have your wireless systems on correct frequencies, we can now take a look at the receiver end.  It is best to place the receivers as close to the wireless transmitter as possible.  This will allow the strongest signal possible.  I did a bit of testing, and with the SLX bodypack at 10 feet from the receiver it measured -30.5 dBm.  When moved to 25 feet, the signal dropped to -41.5 dBm.  When moved to 50 feet, the signal dropped to -52 dBm.  As you can see, the closer the receiver is to the transmitter the better signal received.

Line of sight from the antenna to the receiver is also important.  Walls, people, audio racks, even metal near the antenna can affect the receive signal strength.  At North Ridge Community Church, NRCC, we placed our receivers in an audio rack at the front of house, FOH, mixing position.  We felt that this location served better for troubleshooting reasons incase we lost audio from the pastor.  The antennas for the receivers are behind a small 4 inch thick wood framed wall, and mounted in an audio rack to the stock brackets that come from Shure.  By taking the antenna from free space (nothing around it) and moving it down into that rack the signal dropped from -56 dBm (open space) to -68 dBm (rack mounted).  That is a 12 dB loss just by having the antennas mounted in the rack which the receivers are in.  By keeping a clear line of sight from antenna to transmitter, you can keep your losses to a minimum.

Here lays my problem which I wanted to fix.  I have seven wireless receivers, all with two antennas each, having 14 antennas mounted in free space is going to be an eyesore!  I wanted to find a system that would allow me to use two antennas and split them off into the 7 different receivers.  Shure came to the rescue with the UA844SWB which is a 4-Way Active Antenna Splitter.  This in combination with two Shure UA874 Directional Log Periodic Antenna you can distribute your two antennas to 4 wireless receivers.  At a total cost of around $1,200 for only 4 receivers, totaling in at $2,400, my church did not have the budget for that!

In the next few weeks, I will be explaining how I solved this issue on a budget using some creative thinking and knowledge of radio frequencies.

Finding Gold in Random Places

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When coming into a new position at any location where you are the lead tech I strongly recommend looking at EVERY system in every venue of your location. This last week, I was introduced to a room that I have never been in that had an audio system installed in it. I for one didn’t know the room existed nor even had an audio system installed.

Installed in the audio rack that held the mixer was a digital CD/DVD audio recorder, the Tascam DV-RA1000 which is a high resolution audio mixdown recorder that can record 192kHz/24-Bit audio to a DVD or normal resolution to a CD.

The unit was not connected to anything and wasn’t even plugged in! This CD recorder was much better quality than the Tascam CD-RW750 which we have been using to record our sermons for years. The DV-RA1000 includes internal DSP for limiting/compression and EQ not to mention a lot of different inputs both digital and analog.

The largest benefit was the time it takes to finalize the CD. With the CD-RW750 it took about 1.5 minutes to complete a CD after the recording has been stopped. The DV-RA1000 takes less than 30 seconds. Also the time it takes the unit to stop recording and be ready to record a 2nd track is much less time.

All in all it was a great decision to switch to this unit, but even better is that I didn’t have to spend any money as we already had this. I just had to find it! So the moral of the story is that you need to look in all of your rooms/systems/venues and document every piece of gear you have.


Large Format Audio Console vs. Behringer X32

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Just posting some photos of the difference in size that our old Allen & Heath ML4000 48-Channel board compared to the new Behringer X32.

What is great is that I have removed 14au of gear by upgrading to the Behringer X32.

Sound quality between the two is night and day. Without the gates engaged the noise level of the ML4000 us much higher than the X32. Also the clairity of the audio is amazing. The slightest adjustment with the eq is noticed quickly. With use of the gates the system is so clear now.

I am blown away by this mixer.

Behringer X32 Digital Audio Console

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At North Ridge Community Church we have two main rooms that we use for different things. We have our large room, the Worship Center, and then we have our smaller multi-purpose room, the Ridge Cafe. Both rooms introduce some issues as far as mixing goes.

The Ridge Cafe’s mix position is up on a elevated balcony which is intertwined with AC ductwork, AC units, Electrical conduit and condensation lines. You actually have to duck under these to get to where the board is. Whenever mixing here the best way is to mix via the headphones and then go downstairs and compare.

Worship Center has an elevated audio/video booth against the back wall. It is a clear line of sight to the stage and speaker cluster but is not in a accurate position of where the speakers are hung.

When deciding on what board to get we wanted to have an iPad app to be able to mix from. That way our audio techs could walk around within the congregation to get an accurate position to hear their mix.

Next priority was being able to save and recall scenes with flying faders. Being that our rooms see a lot of different ministries, the multi-use function of the room required each ministry to have their own board setup to facilitate their needs.

Consistency and ease of training was also a big requirement at the church with all of the volunteers. So having matching boards or at least same manufacture would help this a lot. We wanted to have a sound tech train in one room and be able to cover a position if needed in the other.

With those requirements the boards we were to select from included the Yamaha LS9, PreSonus StudioLive, and most resently the Behringer X32.

I ruled out the StudioLive as it does not have flying faders. Having the ability to recall scenes for our different ministries at the church. One thing I loved about the StudioLive is the ability to record the 24 individual tracks at the same time to a computer digital audio workstation, DAW.

The next board, the Yamaha LS9, at around $6-7k, had a higher price point. However, this board included flying faders and the ability to save and recall scenes. The board did not have the ability to record more than just the stereo bus.

I decided on pulling the trigger on the Behringer X32 for some of the following reasons:

– 32 mic in, 6 line in, 16 mix buses, 6 matrix mixes, LCR or LC+R setups, AES/EBU output, 16 assignable balanced outputs
– Flying faders
– Ability to save and recall scenes (up to 100 scenes per show currently firmware 1.08)
– Up to 10 iPads can connect to the board at one time with the xicontrol app (also a monitor mixing app for the iPhone is in the works at Behringer)
– AES50 digital snake will allow remote stage boxes (Behringer S16) to add additional patchable inputs to the X32.
– Record 32 separate tracks to a DAW over USB 2.0 or FireWire
– Compressor, gate, adjustable low cut, 4 band fully parametric eq, and channel delay on each channel
– Adjustable delay on the control room speakers and headphones

The list keeps going of how flexible this board is. Also the X32 interfaces with the Behringer P16 which is Behrimger’s version of the Aviom personal mixer. So on to of the 16 buses the X32 also gives you 16 assignable outputs specifically for the P16.

All of this comes in at the price point of $2899. I was able to purchase two X32’s for the price of one Yamaha LS9. The flexibility that will come with adding the Behringer S16 16 input/8 output stage boxes that transfer over the AES50 protocol, will be huge for my church.

With any company/product/console reliability is a large concern. Behringer has their 3 year warranty on the X32 so that makes me feel a lot better about the purchase and the fact that Midas was the majority of the design for the X32 almost alleviates the concern. But only time will tell.

I have a bunch of videos on the Behringer X32 on my YouTube channel which you can find at http://www.youtube.com/KD7QCU.

If you have any questions on the board please watch the videos or post below. After mixing with the board for the last 3-4 weeks I am blown away by how awesome this board is. Uli Behinger an his team has really found the right design for this!


Stereo to Mono Conversions

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At North Ridge Community Church in our Worship Center we have a mono system.  Mono meaning that there is no left or right, there is just the one speaker.  Our room doesn’t have a good shape for everyone to get a good stereo feed, so mono it is.

Almost every CD player, computer, MP3 player or media player is in stereo.  On a sound board, to get these media devices connected, you often have to use a stereo channel or two mono channels (one for left and one for right).  With a mono audio system you combine the left and right channels inside the sound board to send to your speakers.

Most churches require a lot of media devices to play from.  At NRCC we have a computer, iPhone/MP3 player, CD Player and DVD player.  If you add that up that is 8 different connections into the board for 4 devices!  If your church has a smaller format audio console, those add up quick and take up your channels!

One way to fix this is by using a stereo to mono summing circuit.  This isolates the left and right signals and then joins them together to form one output that you can send to the sound board.

As we can see in Figure 1, we have our left and right channels.  The easiest way to think of this is, think of an RCA cable.  So you have your red and your white cables.  The pin that sticks out of the RCA is the positive, the part on the outside is the ground or negative.  This circuit takes the positives of both the left and right, puts them through a 1,000 ohm resistor, joins them together and then puts it into one single RCA jack.  This circuit works well, you may loose a bit of volume using this, but it’s nothing a gain adjustment can’t fix!

One way to improve on this is to add an audio isolation transformer to isolate the audio ground.  By isolating the audio ground you remove any chance of ground loops (humming/buzz).

As we see in Figure 2, there is a transformer added into the mix.  This transformer, in a simple way of thinking about it, copies what is on the left side and pastes it on the right side while keeping both sides electrically isolated from each other.

In the photograph above is a old broken “Live Wire Solutions Direct Box SPDI” in which I removed the transformer.  I separated the two 1/4 inch jacks and connected them together via 1k resistors, this goes to the -20dB pad switch, then goes into a 1:1 audio isolation transformer and then gets connected into the XLR connector.  Pin 3 and Pin 1 are connected together on the XLR connector.  Positive is connected to Pin 2.  This box is now converting my stereo feed into a mono feed.

By making cables or small converter boxes you can “sum” the stereo to mono before your mixer and save yourself some channels.  If you have any questions feel free to post below!

ClearSonic IsoPac A Review

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As seen earlier in the blog, we received our drum isolation booth.  I figured I would put up a review on it here.

At North Ridge Community Church we have a very nice acoustic Pearl Custom drum set.  The kit sounds really great and with our drummers they can really make it come alive.  The problem is, that our drum set sits so far forward on the stage, the congregation gets a full ear of drums.  Also to make this a bit more problematic, we mic the drums and put them through the PA.  So when listening to the worship set while in the room your ears hear not only the kit sound but also the sound from the PA.  This makes the sound a bit muddy and hard to decipher where to listen.

Other issues of the acoustic set, is that the stage monitors had to be loud enough to let the musicians hear themselves.  Adding into this, we have a choir that sings in our traditional service.  The choir microphones picked up a LOT of drums and not much choir.  Because of this I had to place 6 microphones onstage to close mic the choir, as you may know, every mic added lowers your gain before feedback in a live situation.  This was problematic for us as we couldn’t get enough volume out of the choir before feedback would induce.

Enter ClearSonic IsoPac A!  This shipped in via 8-9 boxes, the heaviest being 116 lbs!  After opening up all of the boxes and recycling those it was time to build the booth.  The clearsonic panels come assembled and ready to fold out to surround the drums.  They ship with a paper protective cover that you need to peel off.  The manual states that once the paper is removed from the panels you cannot return it anymore.  After removing the paper from the main shield and the upper set of shields you need to place some plastic connectors to attach the upper to the lower set of clearsonic panels.  I got an extra helper to aid me at this point.

After getting all of the clearsonic panels built it was time to setup their “sorber” panels that go behind the drum set.  Once those were in place I moved the drum set into place.  Following the drum set was to wrap the clearsonic shield around the front and sides of the drums.  The sorber lids go on top being supported by two telescoping metal support bars.  Sorber panels attach via Velcro stickies to the clearsonic panels.  After adding the final touch of a fan to keep the drummer cool you are finished!


There is plenty of space within the booth.  It is quoted to be 7 ft wide, 9 ft long and 6.5ft in height.  Because it is a booth that you setup yourself you can fit it into any shape you need to.

Aesthetically it is beautiful.  This is the nicest looking booth I have seen.  Most of the booths that you see are pretty atrocious.  ClearSonic offers this in a light grey and a dark grey version for the sorber panels.  I decided the dark grey to match our color scheme of the church.


Cable routing is easy, there are small 45 degree cutouts between each clearsonic panel.  Also there is the space between the sorber panels and the clearsonic shield.  Along the same topic with cable routing, depending on how much stuff your drummer has setup in there, I found there is plenty of room for normal microphone stands.

Cooling is a large problem and concern with drummers and isolation booths.  The IsoPac A is NOT fully sealed off.  The back part of the booth has about a 1.5ft gap between the roof and the rear sorber panels.  This space as well as a fan makes it quite nice inside.  I added one more fan sitting on the ground to point up towards my drummer.

Upon walking into the booth and closing the sorber panel behind you, it gets very quiet, to the point where if someone is talking outside the booth, you can’t hear them unless they yell.  Playing drums inside the booth is pleasing, the sorber panels do their job of absorbing a lot of the reflections inside of the booth.

Volume savings are amazing.  Before the booth our drum set in the congregation and onstage would get to 95dB easy.  After installing the IsoPac A the dB level is at 70-75dB.  AMAZING!  Onstage we had to put the drums into the monitors for the musicians to keep on time.  Overall stage volume lowered as we were able to drop the volume on the stage monitors.

The choir no longer complains about the drums being too loud on stage.  And I have been able to reduce to 4 microphones for the choir which has allowed me to get 6dB more gain out of the system for the choir.  The bleed into the choir mics has reduced tremendously.

My only complaint about the booth is that it is dark.  To compensate for this we added a small halogen parcan inside to light up the drummer.

Overall for less than $2k getting the benefits of this drum isolation booth was amazing.  Very much worth the cost for this.  Aesthetically pleasing and with huge volume savings are the biggest pros with this.  ClearSonic makes other sizes and products to aid in lower stage volume and isolation of instruments.  Check them out online at http://www.clearsonic.com.