Audio processing explained

Most FM broadcasting transmission chains have at least a basic degree of audio processing included, in order to improve the audio loudness. The reason for this is related to the radio listeners’ typical environment: driving in the car, cooking in the kitchen, working in a factory, etc. These environments can be loud and radio audio needs to help to cut through this!

While this is the main reason for audio processing, it is also used for:

  • Consistent levels – so listeners don’t have to adjust the volume constantly
  • Consistent sonic signature/EQ – so a radio station can have a unique sound that is appropriate for their format of music
  • Optimization of the signal to noise ratio of the channel
  • Controlling the interference of neighboring radio stations through peak and bandwidth limiting

What is audio processing?

Audio processing uses a combination of compression and limiting to lower the dynamic range, reducing the peak to average the ratio of the audio at each subsequent stage.

audio processing BW Broadcast


1. Compression stage

Compression reduces the dynamic range of the audio slowly, in a manner similar to an operator riding the gain. Compression is usually performed on the RMS level of the audio waveform and is usually gated to prevent ‘suck-up’ of noise during silence or quiet periods. In addition, compression is usually multi-band.

2. Limiting stage

Limiting has faster action and higher ratios than compression. Audio is split into several frequency bands (often 4 or more) so that bass sounds, mids, and highs are processed separately. This prevents most of the problems you get with basic single-band limiters. Each band is compressed in dynamic range – the quiet parts are boosted and the loud parts reduced. It creates a denser, louder sound but can create intermodulation distortion if overdone.

Audio processing BW Broadcast


3. The clipping stage – FM & AM

Removes all audio above a certain clipping threshold. Reduces the peak to average ratio of the audio dramatically. It will produce harmonic distortion, and if overused it can also produce intermodulation distortion. The clipping stage has zero time constants, so it has no effect on surrounding audio.

Why do I need audio processing at my radio station?

Most radio stations, big and small, use audio processing in order to stand out from the crowd and get more listeners. The main benefits of audio processing are listed below:

  1. Increase overall audio level ‘loudness’ and improve the signal to noise: makes you sound louder than other stations and jump out at listeners. Maximize the headroom in the transmission channel, moving audio as far away from the noise floor as possible, which improves the signal to noise. It also aids listener ability in vehicles by having a consistently loud sound to combat engine and road noise
  2. Ensure audio level consistency to aid listener experience: listeners don’t have to constantly adjust the volume of the radio. 
  3. Over-modulation, distortion, and interference: too high audio level results in distortion in receivers and interference to neighboring FM or AM stations. Digital radio will sound terrible when 0dBFS is hit in the codec, with large amounts of distortion generated. However, too low audio level results in background noise being heard. Changing levels can result in noise, distortion, and listener adjustment
  4. Create a sonic signature to sound how you want to sound. A unique signature sound sets you apart from other radio stations and is something that listeners will recognize instantly

Audio processing solutions from BW Broadcast

For listeners, good radio sound is everything. It only takes them a few seconds to decide whether they want to keep listening to your station or switch to another. With the right audio processor, you can ensure a high-quality signature sound for your station and attract more listeners.

The BW Broadcast audio processors are popular among many radio stations around the world – from bigger networks such as BBC, to small community stations in Africa. These cost-effective, yet high-quality processors make sure that your audio is loud and clear. Available in different multi-band configurations for FM, AM, digital radio and web streaming. 

DSPXmini Encore audio processor

The original DSPXmini and DSPXtra audio processors have spent the last 12 years dominating the low-cost, high-value audio processing market, offering FM, AM, and HD versions to broadcasters who need to sound the best on a budget.
The Encore versions of this industry favorite now puts all models into a single box, along with platform-wide features such as intelligent PlanB audio backup and remote control monitoring.

DSPXmini Encore





Categories: Other Posts, Useful Articles

FCC loosens rules for translator location

Following the Federal Communications Commission‘s (FCC) newly modified rules, FM translators can now be located anywhere within the AM’s daytime service contour or a 25-mile radius of the transmitter, even if the contour is farther than 25 miles out. Previously, the rule said an AM station could place a rebroadcasting FM translator within the smaller of its daytime service contour or the 25-mile radius of its transmitter.

This means that the 2,000 or so US AM radio stations that rebroadcast on FM translators now have more flexibility in locating those FM signals. A search of the FCC’s database by engineering consulting firm du Treil, Lundin & Rackley, shows 157 commercial band FM translator service applications being accepted by the commission last week compared to approximately 24 the week prior.

FCC FM Translators regulation updateImage: 

Industry-favorite transmitters

BW Broadcast has been a popular manufacturer for transmitter equipment over recent years. Our FM transmitters have been the industry’s chosen units across LPFM stations and community stations in the US and continue to receive positive feedback as truly reliable transmitters or exciters. Offering unprecedented performance and quality, these FM transmitters are feature-packed and sound great right out of the box.

If you are interested in placing a new FM translator following the rules update from FCC, then make sure you choose a high-quality product without blowing your budget.

TX300 – market leading audio performance

The most popular 300W FM transmitter in the world, the TX300 V2 can be found in LPFM stations, community stations, emergency broadcast kits, military applications and as a truly reliable backup transmitter or exciter for national broadcasters. Whatever the application, the TX300 V2 will take it in its stride. Now with built-in 4-band DSPX audio processing, Ethernet control and FSK IDer.

  • Integrated multi-band DSPX audio processing makes your station sound great, right out of the box
  • Comes with one of the cleanest exciters and an ultra-low distortion modulator, which make it a highly stable FM transmission system
  • Slide-in power supplies make the maintenance a breeze, which means that in case of major problems the supplies can be fixed in minutes
  • Configurable Status and Alarm ports control and signal to external equipment
  • Flexible and extensive Web Mail, SNMP, Telnet and Serial Remote Control that keeps you aware and in control of your station’s transmission
  • 2-year international warranty
  • 24/7 technical support



Don’t take our word for it. Hear what our customers say

Easy to install, super natural audio, reliability you can really depend on. No competition in the marketplace, professional natural audio, reliable and excellent value” – David Kennedy, WPBJ

Really like that BW Broadcast V2 exciter. Easy menu adjustment of frequency and power. Quick bootup, smooth power adjustment using one knob, and easy to read front panel LCD.  ”Nice job ole boy!”.” – Jeff Parker, Chief Engineer at Clear Channel Media and Entertainment

Besides our FM transmitters, we have also sold hundreds of single-box FM translators and RBRX Encore rebroadcast receivers to broadcasters across the States. Offering you unprecedented performance at an affordable price, you really can’t go wrong with investing in our technology.


Interested to find out more? Get in touch with our sales team now. Or better yet, find your local dealer to book a free, no-obligation demo to see for yourself!



Categories: Other Posts, Useful Articles

Future of FM Processing

We grabbed Scott Incz, BW Broadcast CEO and lead designer of the DSPX processor range to hear his thoughts on how the processing landscape will change over the coming years.

In the big scheme of radio broadcast audio processing, what’s the next frontier?

I believe that the next technological frontier that broadcast processing faces is in the delivery medium to the listener. With the rising popularity of on-demand services, I see the challenge is for audio processing to make use of future client hardware platforms to deliver the quality of today’s broadcast processing on mobile and utility devices. This is about optimizing processing and developing even more efficient algorithms that can run on low cost mobile and low cost utility devices.

I think a lot of the drive for loudness has come from listening to the radio in an automobile. Dealing with high noise environments that require audio with a low dynamic range but allowing people in a better listening environment to enjoy a higher fidelity version of the audio is an interesting challenge.

How has streaming changed the landscape; and what is BW Broadcast’s response?

The potentially massive audience provided by online streaming has resulted in it being so popular for broadcasters. The level of competition is also huge so it’s going to be hard to get a large audience; therefore the budget for streaming audio processing is usually much lower. BW Broadcast understood this decade ago and started adding value to their products by adding full bandwidth secondary outputs to its FM and AM processors that are optimized for streaming and digital radio. This has allowed radio stations to not only get a better return on investment from their audio processors but to sound great both on conventional radio and online. BW Broadcast recognizes and appreciates the impact of processing on codec technology and vice versa, and has multiple processing products that contribute to making streaming radio stations sound great – in fact, any digital station sound great, IP based or with data over an RF carrier like HD or DAB.

I personally believe that some audio processing will be in the client to give the listener more control of the sound and the environmental effects on the sound. It won’t be long before we will be designing client based audio processing for translucent touch screen shower cubicle speaker doors to cancel out the water noise.

Some audio processing is always required for radio and in the short term the requirement for audio processing won’t go away. In the future I think that an unobtrusive smart multiband device like the Ariane AGC leveler is the best way forward for radio stations, and then give the control to the listener in the client device.

What is your latest audio processor introduction?

At NAB 2013 we revealed our new V2 FM transmitter range, for which we won an industry award at the show. Among the features that engineers loved was the inclusion of an embedded DSPX family 4-band audio processor, from which users can adjust from the front panel and the remote control interfaces.

Never has such a powerful processor been included as standard with an FM transmitter, and never has an FM transmitter sounded so fantastic out of the box.

Although it is not strictly a new processor from a technical perspective, the Ariane Sequel AGC leveler is now being manufactured under the BW Broadcast label since we took over the rights to it earlier in the year from TranLanTech.

DSPX-FM Audio Processor

For the full interview with Scott, download the new Radio World e-Book ‘What’s New in Audio Processing?’:

Download e-book Now




Categories: Useful Articles

Get Your Station Online

Streaming your radio station online is now a necessity to provide your listeners with as many possible ways to ‘tune in’.  With the popularity of on-demand services growing, and 3/4G coverage extending radio stations can’t afford not to have an online stream.  Thankfully, with the right equipment and streaming provider it is very simple to get your station online.

Step 1 – Process the Audio Correctly

The first consideration is audio processing – online streaming has very different requirements to broadcast processing for FM.  There is no pre-emphasis, 15kHz low pass filtering or composite clipping.  A station faces two choices, buy a dedicated streaming processor, or find a broadcast processor with dual processing paths.

The DSPX-FM is perfect for web-streaming with dual processing paths

The DSPX-FM is one such processor, with a composite output to feed the stations FM transmitter and analog and digital AES/EBU either of which can feed the web stream.  Dual processing paths allow the web stream to be processed simultaneously, with full 20Hz-20kHz output. The FM analogue path has a multi-band distortion-controlled clipper, while the second path, tapped via analogue and AES/EBU digital output connectors, incorporates a bit rate optimized, look-ahead limiter. The included 16 factory presets, as well as intuitive local and remote interfaces help you get your DSPX-FM setup fast. Whether you are a processing novice or expert, you’ll easily achieve a signature sound for your station’s format – both over FM and online.

Step 2 – Convert to an IP Audio Stream

Once your audio has been processed and ready to distribute, you will need to use an IP audio encoder to convert the audio to a digital IP stream. There are many ways to do this, from dedicated hardware to software solutions that run on a PC or Mac. Our suggestion is a dedicated hardware solution such as the Sonifex PS-Send. It has no moving parts and is passively cooled so is ultra reliable and doesn’t require any maintenance.

Sonifex PS-SEND has all the right connections

The PS-SEND has balanced analog and AES/EBU inputs which allow simple connection to the DSPX-FM. All the configuration settings for the unit are accessed via a local web-server built into it and it supports G.711, WAV and MP3 Layer 1/2 codecs.

Step 3 – Choose a Streaming Radio Provider

The hardest part of getting a station online is choosing a streaming radio provider – there are so many options available. Each have different packages and website integration options and it can seem impossible to compare each to decide which is right for your station. As well as the features each provider offers, it is important to consider service uptime records, and support options should you have any issues.

We’ve done the hard work for you, after testing many options BW Broadcast has partnered with Wavestreaming as we feel they offer the best combination of features, value and support for professional broadcasters. Established in 2004, Wavestreaming has grown to become a market leader in online radio; providing broadcasting solutions to over 5000 stations worldwide.

Their audio streaming services and embeddable radio players enable a multitude of clients including commercial radio stations, DJs, record labels, religious and charitable organisations, sport & news broadcasters and media companies, to easily broadcast to their audiences. Wavestreaming’s network of strategically located servers provide an uptime of 99.9%, ensuring constant 24/7 connectivity to your listeners. The server capability is strengthened by their close partnership with SHOUTcast. Used by over 50,000 radio stations worldwide, SHOUTcast is the industry standard platform for stations who want to broadcast online.

Wavestreaming have a package for all stations

Firstly, you’ll need to choose the level of service you want. Their packages priced at $29 to $99 per month are designed to suit most small to mid sized stations but can be indefinitely scaled as a station grows. Larger enterprise solutions are also available and Wavestreaming’s internet radio packages provide you with all the bandwidth and speed you’ll ever need, whether you are a local station or an internationally recognised brand.

Once you have selected and purchased the package that’s right for you, you will be given access to Wavepanel, Wavestreaming’s custom software which is your control centre for managing your station. Once you are set up, a web player can be easily customised and embedded into any existing website. You can even broadcast directly onto your Facebook page or straight to your listeners iPhone.

Wavestreaming’s Advanced Features

Wavepanel has some incredibly powerful realtime analytics and tracking capabilities that enable you to gain valuable insights into your listeners. These stats allow you to identify trends and make more informed decisions about your listeners. Twitter integration is also available that automatically updates your followers with your ‘now playing’ information.

  • 8 Year Track 99.9% Uptime Records
  • Geo-location – Lets you see where your listeners are located
  • Radio Directories & Apps – free listing (SHOUTcast, TuneIn, iTunes + more)
  • Cross Platform Compatible – Tune in Online, iTunes, Windows Media, Winamp etc
  • Player suite uses Latest HTML5 technology
  • Works on mobile, tablet and desktop
  • Customisable themes
  • Easy Facebook integration

With their full suite of tools and unparalleled uptime, Wavestreaming make it easier than ever to get your station up and running online, whilst enabling you to seamlessly integrate with your existing systems.

They can even provide you with a range of free and custom training packages to get you quickly up to speed.  Click the banner below for more information.



Categories: Useful Articles

Exciters, how to choose?

Remember Vinyl and tapes? Then along came CDs – and the majority agree that was a big leap forward in audio quality. Then came MP3s and we were sold on how digital progression could give us less for more. Same great sound but in less bits, so we could get more on our computer or download faster. It wasn’t long before people realised that although MP3 offered data reduction improvements with its obvious benefits like music streaming, there was a penalty in audio quality.

In the broadcast industry, an advance to digital technology has opened up many a passionate debate. DAB was promoted as the future 20 years ago, but it’s poor coding technology and the desire to squeeze more stations in the same amount of digital bandwidth has seen a reduction in quality for the listener compared to analog FM. The same debate rages for IBOC/HD and other new broadcast systems.

The perception that digital is better has recently crossed into the analog FM transmitter industry. Although the authors of this article and the author of the referenced white paper acknowledge that a correctly designed direct to channel digital synthesis of the FM carrier dramatically improves the audio and RF performance of the FM signal, we look to highlight, like MP3,  that just because a transmitter generates it’s signal digitally (DDS) it doesn’t always make it perform better.

The picture above illustrates a clean  FM transmitter as shown in the report below.

The attached white paper was written as a study of the noise performance of Direct Digital Synthesis (DDS) and analog FM broadcast transmitters, comparing performance when un-modulated, modulated with single frequencies and modulated with audio. The tests are carried out on three transmitters, two implementing DDS: a PTEK FM150ES and a Zhongchuan Digita  ZHC618F-100W, and one analog: a BW Broadcast TX150. Although the commonly held belief is that DDS provides considerably greater performance compared to analog  transmitters, the white paper demonstrates that this is not the case for the devices tested.

The tests show that for the two DDS devices chosen, the RF spectral output of the transmitters does not conform to the ETSI EN 302 018-2 european harmonised standard for FM broadcast transmitters, making them unsuitable for use in many countries. In some cases they may also become dangerous to use as they cause interference in bands reserved for aircraft automatic landing and communications systems. Throughout all of the tests, the analog BW Broadcast TX150 conforms fully to the standard. The results are plotted as frequency spectra given with 1MHz bandwidth to see spurious signals close to the carrier, and at 50MHz to see signals further from the carrier.

The picture above illustrates two different transmitters with the same modulation.

One is digital and marketed as state of the art, while one is analog and may be considered older technology. Which is which? Click the report link below to see if you guessed right.

Comparison of Exciter Methods – BW Broadcast Whitepaper





Categories: Useful Articles

Getting the Most from RDS

Is you using RDS to allow your station to be seen as well as heard? Perhaps you are but have often wondered if you are getting the best from the features available to better engage your listeners. This document written by Alan Jurison is ideal for those starting out with RDS, or those wanting to exploit the standard and start using advanced features like content tagging.  Five helpful features can be downloaded below:

Chapter 1 – What You Need To Know
Chapter 2 – Optimize Radiotext Send Rate
Chapter 3 – Optimize PS Scroll
Chapter 4 – Injection & Pilot Synchronization
Chapter 5 – Radiotext Plus Holds Promise

Simply enter your email address below to display the download link:

Your Email (required)



Categories: Useful Articles

Thanks for sigining up

Your email has been added to our mailing list.

Close window 


Coming Soon

Close window 

Logged out

You have now logged out

Close window 

Thank You

We will contact you shortly

Close window