REW for the first time

[arivel]

I'm currently trying this:

Peace Equalizer, interface Equalizer APO / Peace Wiki / General FAQ

sourceforge.net

it's free . All right ?

 

[arivel]

Is there a way to check the correct functioning of the bass reflex port?

 

[arivel]

hello everyone .
i want to use the method described in the following two web pages to measure the small-thiele parameters of my speakers .

Impedance Measurement

Thiele Small Parameters

a non-inductive resistor is recommended but there are many types of resistors with this characteristic . can you recommend the right one ?.
bye thanks

 

[dcibel]

Any resistor is fine really. REW's calibration process will compensate for the resistor and test lead inductance, so I'm not sure why the recommendation is for a "non-inductive" one. Besides, a standard low resistance wirewound 10W sand cast resistor has an inductance in the 0.001mH range, not very significant in the context of speakers and crossovers. My test jig uses a normal 5W sand cast 10 ohm resistor, and it's perfectly fine.

My jig is made for use with a power amp, as well as loopback for speaker measurements:

Dual Channel Measurement Jig - HTGuide Forum

Here's a schematic for a simple dual channel measurement jig, which can be used with ARTA, REW, or SoundEasy.

www.htguide.com

On the port measurement topic, of course "there is a way", multiple ways in fact. One would be to measure nearfield response of the woofer output, and port output. These two measurements can be combined for a total response similar to the software cabinet model. Alternatively, the speaker low frequency response can be obtained using a "mix in box" method. This method can provide a good detail of the total low frequency response output, but won't be able to separate the woofer output from the port output.

 

[arivel]

interesting your system.
going back to the link I posted, it seems that in reality on the REW page 3 measurement methods are proposed.
1) direct use of the audio card outputs with a 1KOhm resistor
2) use of a headphone amplifier with a 100 Ohm resistor
3) use of a power amplifier with a 33 Ohm resistor
but the image on the page only shows connection diagram number 1).
where are the other two connection diagrams?.

 

[dcibel]

1 and 2 are the same, 3 I have provided for you, it is the same but with a voltage divider at the soundcard input to step down the signal to "line level".

REW it a tool, how you use it is up to you. All methods of connection that produce a signal at the soundcard input for analysis are possible. Impedance measurement is simply to create a voltage divider between the driver and a known constant resistance.

 

[arivel]

what do you think about this tool ?.

Audio Measurement Pre-Amplifier – Part 1 – Motivation and Circuit Design – Toli's DIY

 

[arivel]

if instead I decide to use the sealed box method how many liters should the total volume of the box be for 12" ,15", 18" speaker drivers?
thanks

 

[dcibel]

Ideally a volume a little less than expected Vas parameter.

 

[arivel]

unfortunately I don't know this data (vas)

 

[arivel]

hello everyone.
I created the RIG to make the impedance measurement. I need this to subsequently obtain the small-thiele parameters via the known volume method.
Evidently I must have done something wrong. I made two measurements, one of these was made before the three calibrations, the other measurement was made after.
The one made after does not even remotely resemble an impedance curve.

 

[dcibel]

You're going to need to show your work. Wiring diagram of what you've done, and MDAT file including open circuit and short circuit calibrations, and settings used for calibration, Rsense and Rinput.

 

[arivel]

hi. i solved the problem on the impedance measurement but after this i have to face another problem. every time i switch from the impedance measurement via headphone output-resistor to the SPL measurement in frequency via power amplifier, i have to change the circuit. instead of building the box specifically designed for these applications, i thought of buying another audio card to use alongside the emu0404 that i already have. one card will be used to measure impedance and the other card instead for SPL. in this way a simple switch is enough and nothing else. i am undecided whether to buy a card with (USB3 - USBc) or buy a card that has many inputs and outputs but with USB2. with a wideband USB do i get advantages when i do the measurements? if not then i turn to cards with many inputs and outputs with USB2 and a halved cost. what do you recommend?

 

[sm52]

For any measurement, one USB connection of the external sound card to the computer is enough. There is no difference between USB2.0 or USB3.0 or USBC for measurements. But if you plan to listen to music in headphones through an external card, then a map with USB3.0 or USBC is better. A little.
Inputs and outputs for measurements are required 2+2. So choose a high-quality sound card with 2 inputs and 2 outputs and USB for communication with a computer.

 

[dcibel]

It seems a bit silly to me to purchase a second sound card when a few resistors will do.

Dual Channel Measurement Jig - HTGuide Forum

Here's a schematic for a simple dual channel measurement jig, which can be used with ARTA, REW, or SoundEasy.

www.htguide.com

 

[arivel]

It seems that the box you propose uses the power amplifier and this is dangerous because it could burn the inputs of the sound card. I instead prefer to use the headphone output and be more relaxed.

 

[dcibel]

You can pick whatever voltage divider fits your needs. Add some zener diodes for protection if you're prone to doing silly things, personally I don't find myself running a measurement with input gain and output volume at max, something tells me I should look at the knobs before I run the measurement. You do what ever works for you.

 

[arivel]

I have the possibility to buy used sound cards at a very low price (saffire, steimberg, ultralite etc.) but I have to choose between USB2 or FireWire 400. They are not recent because they are devices that are about 10 years old but even the emu0404 that I already have is not young. It remains to be understood if USB2 or Firewire400 is better for audio measurements. What do you recommend? Bye and thanks

 

[dcibel]

FireWire died years ago, go with USB interface if you want to be able to use it easily with any modern computer.