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Introducing RPlusD

May, 2013

RPlusD was created to meet measurement requirements for audio system playback in small and medium sized rooms. It was designed exclusively for this purpose and with end users such at HT installers, audio installers, playback studio acoustics, and serious car audio installers in mind. It is not a bench or lab instrument but could be used as such, but there are better analyzers for this purpose.

RPlusD is the latest software from etfacoustic. It is a very different and much better product than our first standard audio analyzer for the PC, ETF5.0 (others were written but were fundamentally different in operation).

RPlusD is simply the best available analyzer for the purpose of taking measurements for hifi sound reproduction systems in small and medium sized rooms available at any price. This is mostly because it was developed, in every way, with this exclusive purpose in mind.

Its test signal, the "hybrid sweep/MLS" gives advantages of both test signal types when the analyzer is used for its intended purpose. It has a stream lined user interface developed to view and process measurements in the way that they should be processed and viewed to have the following charcteristics:

The characteristics of good and useful measurements are:(1) verifiability, (2) relevancy, and (3) repeatability. Many analyzers on the market may be free or cheaper, but none or so thoroughly designed with goal of obtaining accurate, repeatable, and relevant measurements in mind using typical computer hardware.

RPlusD required a re-writing of the manual from ETF5.x, a re-evaluation of measurement methods, consulting with outside experts, and redesigning measurement techniques to ensure that the user would obtain accurate, verifiable and repeatable results when performing measurements of playback systems in typical home theaters as well as rooms as large as movie theaters.

RPlusD was not made for giant concert halls and it is unknown (by me) if these ("LTI based") measurement methods will work in these environments due to air currents and temperature gradients present in these spaces. I do not have faith that the "LTI" system assumptions are valid for these large spaces.

Before making a purchase of any analyzer, we recommend reading the RPlusD manual first, to see what is required for accurate, repeatable and verifiable results. Our experience shows that many users of lesser products take measurements that do not meet these requirements. The methods required in meeting these critical requirements are illustrated throughout the 160 page manual (mostly diagrams and graphics of example measurements). All operations of the software are carefully explained and illustrated. Most users only need to read the first four chapters to understand all the functionality for the software they require.

Consulting services are also provided for users that are uncomfortable with signal processing and EQ functions but comfortable enough with computers to operate the software. This costs $100.00 USD in addition to the program and includes file analysis and recommendations. Details on this are at the bottom of this document. This service is good for busy people who wish to learn the software functions quickly with their own room used as an example. It is also good for people that have specific acoustic problems they wish to solve.

The RPlusD enhancement license includes curve fitting for automatic filter estimation from measurements in normal rooms to isolate resonances and the ability to take measurements using a test signal CD, eliminating the normally required sound card - audio system electrical connection. This system is not ideal and details of this are explained and shown in the CD Test Signal window help link. This feature was written for experienced users that understand the measurements well enough to understand the parasitic effects of this new system of wireless data gathering. Dealers and installers will appreciate its (normally impossible)high resolution, speed and convenience.

The upgrade also now includes emulation of the Behringer DCX 2496 loudspeaker management system. This is a digital electronic crossover for bi/tri amplified speakers or to simulate crossovers in analogue systems for people wishing to build their own crossovers.

Most users will not benefit from having the upgrade and are just as well off with only the basic version.

FAQsList.PDF (read this first)

SoftwareFeaturesAndFunctions.PDF This is a product brochure showing screen grabs of all the RPlusD functions

RPlusD Demo Download

This software is very easy to set up and use if you are willing to read chapter 1 of the manual posted below on this web site. Its all we can do to make this as easy as possible.

RPlusDDemo.msi version 1.2.50

Size: 4 Mb

PLEASE NOTE: some studio type sound cards do not have windows WDM drivers as required by the software. These can always be found for free on the web. Type in "make & model of sound card + WDM Driver" into a search engine.

Windows 7,8 and Vista sometimes have the USB recording input set to mono, which will give non ideal results when testing the software for correct operation. This can be rectified by doing the following: Go to System Settings from the pull up menu on the left bottom of your screen (the Start Up). Go to System Settings, select Hardware and Sound Settings, then select sound or audio devices, go to recording and select microphone USB audio, deselect the mono switch so that the input can operate in stereo.

Description: This download contains the full version. A license number must be purchased from etfacoustic to access the full version.

The demo allows you to check your computer, mic & sound card for correct operation. You cannot take an actual useful room measurement.

RPlusD & Windows 10/8/7/Vista: Some very rare but easily fixed issues (Only users that receive error messages need to look at the PDF given here) No error messages means no problems and that necessary support files already reside on your hard drive, having been installed from other software install packages) Vista Issues.PDF

Problems that people have with the software result from not reading Chapter 1 of the manual. Other competitive software may seem to work when it is not connected correctly and will give inaccurate or erroneous results that are often interpreted as valid by new users. RPlusD is slightly more complex so that it only looks like its working when it is connected and set up properly, this almost ensures that the neophite user will have the software setup correctly when measurements are taken. Competitive and free software can look like its set up correctly but measurements can be wrong.

Mic/Preamp Requirements

Our solution, a combination USB preamp and mic with an internal loop back connection on the reference channel, is no longer available. There are many low cost devices sold on the web, however, for accurate and reliable measurements, a reference channel is required. This is often impossible with low cost USB microphones. RPlusD takes input from the right channel input of a sound card (from the microphone preamp) and outputs the test signal from the right channel output to the system under test which is usually the left or right input of an audio system.

The left channel output is connected directly to the left channel input and provides a reference signal. This facilitates the verification of measurement correctness. If this important connection is missing, measured data is often junk data or noise, but cannot be identified as such and gets interpreted as measurement by neophite users. The reference channel connection permits RPlusD to measure the physical microphone-speaker distance in the setup, which when compared with physical distance in the system under test, forms a verification of the measurement. This all important connection is missing from low cost solutions. This connection also permits the precise frequency response correction of the sound card used.

The Behringer ECM 8000 is a low cost calibrated microphone and there are many preamps available that will amplify the output to be suitable to drive the line input of a sound card. The system consisting of a microphone, a microphone preamp, and a sound card permits the reliable and accurate collection of data using RPlusD. In this configuration the mic is connected to the input of the preamp.The output of the mic preamp connects to the Right LINE IN connection of the sound card. The Right LINE OUT connector supplies the test signal to the audio system. The left channel LINE OUT is connected directly to the left channel LINE IN, forming the reference channel, for which only the sound card is measured

This solution requires more connections than single channel non referenced measurements, requiring only output of the sound card connected to an audio system and the input connected to a microphone WITHOUT the reference channel connection.This reference channel connection is required by RPlusD for accurate data taking. Systems that do not require these connections are substandard and may lead to erroneous data collection.

We have not yet found a low cost USB microphone that satisfies the basic requirements of reliable measurements. The Behringer ECM 8000 microphone and a suitable preamp can usually be found for less than $150.00 USD.

RPlusD Manual & Documentation

GettingStarted.PDF This is a minimal instruction set to get the software up and running. Users of the consultation service need only read this.

RPlusDManual.PDF Full Manual (nearly complete)

RPlusDExampleFile.zip The example measurements file can be downloaded and opened in the demo version of the software.


I do provide free assistance to users of the software who are just getting started to ensure that measurements are being taken correctly. I also answer questions by email regarding specific technical questions. Some users have requested a closer consultation for measurement interpretation. This process costs $100.00 and takes the form of the process outlined below. This process takes the user 1 - 2 hours and usually takes the following steps:

(1) Initial equipment description, monitor speaker type make and model number & room layout diagram required from user by email. A drawing done in 2 color bitmap form should be sent in allowing me to open the bitmap file and add markings and suggestions into the file and to resend it as part of communications.

(2) Help to ensure that the connections are made correctly. This process is outlined in the above "GettingStarted.PDF" posted file. The user must get this part working but does not have to learn anything else.

(3) Email description of measurements to be taken - marked on the bitmap that describes the listening area.

(4) The user emails the measured results in a zip file format (Specific Instructions will be provided- dependent on number of measurements to be taken)

(5) I interpret the measurements and give some recommendations as to what can be done to achieve target measurement response improvements

(6) The user emails new measurements taken after changes have been made and we evaluate the affect of changes on the measurements to see if additional improvements can be made

A maximum of 2 hours is spent on this consultation. If more time is required then additional payment will be negotiated.

Advice is also provided for people that do not wish to use the software. The consists of advice on room treatments that is based on no conflict of interest, as we do not sell room treatments and can give unbiased opinion.

Customer Feedback

Geoffery Ellis, musician, project studio owner and musical instrument maker:

May 26 2007

"As a musician and project studio owner, I place a tremendous amount of importance on having a work space that is a clean acoustic environment for both recording and mixing. But even though Iíve become familiar with computer-based recording, I donít have a scientific understanding of acoustics--I want my room and speakers to sound good, but that is about the limit of my understanding. I spent a lot of time building my studio and making it into the best sounding room possible given the limits of the space, and I knew that the final icing on the cake would be the tuning of my monitors.

That is why I was thrilled not just to find the R+D software, but to also find that itís creator, Doug Plumb, was offering a consulting service that allows me to get the most out of it. Doug walked me through the set-up, providing advice on the correct type of measurement microphone and sound card, helping me get set up to take my measurements, and then (most important of all) interpreting the results and providing me with a working solution.

Since ďtime is moneyĒ, I saved a lot by taking advantage of this service--it would be a value at twice the price."

David Rich, Phd Signal Processing, Technical Editor of Sensible Sound:

April 6 2007

The ETF 5 measurement system has been instrumental in many of my TSS reviews on speakers and electronic equalizers. A reasonable starting point to use this inexpensive software packages a computer's internal sound card and the microphone in a Radio Shack sound level meter. Better results, like the ones I present in TSS, are obtained with an external sound card and calibration microphone. ETF Acoustics has recently introduced RPlusD, which is designed for analysis of combined room and speaker response characteristics.. The GUI is much improved over ETF 5.

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