Optimizing speaker distortion

[UliBru]

why is it such an effort to get distortion results with AC? Couldn´t all necessary graphs be stored directly in according working directory and you just have to push a bottom to get distortion measurement result such as in REW or other programs? I really find me avoiding to use this function in AC as it is a mess to make quick distortion measurements here..maybe worth to think about it in an future update?

I'll put it on the list of ideas. Hopefully it will then migrate onto the todo-list someday

[Labdoc]

Hi Uli and Others,

A simple hypothesis: if a speaker driver does not like to play certain frequencies it will produce distortions in this range.

Returning to this post, to ask about measurement of Low Frequency (LF) drivers. In my case, the speaker is a bass reflex 3-way, large stand mount speaker. The LF-MF crossover is at 530 Hz. The LF driver is 10" (250 mm) diameter and there is a rear-facing port contributing to the LF range, which is specified as 48 Hz. The manual does not say whether this is - 3 dB, but I assume this is what is intended.

I am interested in measuring the LF driver distortion and frequency response, for the purpose of picking a suitable corner frequency for a crossover created in Acourate. Acknowledging that the room is a major factor in measurements of LF drivers, what is a practical approach for use in Acourate?

[UliBru]

The room is less important for distortions than the driver/speaker itself. So think about the allowed/safe range where the driver will play.
E.g. the low driver may play up to 1 kHz. And the mid driver down to 100 Hz.
So simply run a logsweep measurement without crossover in the safe range. You can usually run a near-field measurement,
The calculate the distortions and check if there are frequency regions where a driver shows higher distortions. E.g. the mid driver will may show rising distortions with lower frequencies as it is simply not designed to play bass.

[Mister Cool]

Dear all,

just to be clear, where the two mentioned files are comming from



1. LogSweep - Measurement - File -> is this the logsweep file for the given driver, which I try to analyse and optimize -> made in "near field" wo XOs and located in the project workspace (e.g. Pulse48R.dbl). It has to be loaded in Curve 1. On the screenshot we see an WAV file, but I presume, it could be a dbl file too

2. LogSweep - inverse - File -> where does it come from? Which file is it?
I know inverse from Macro 3, from linearisation process, from user\Documents\Acourate\LogSweep directory,...

[UliBru]

You find the logsweep measurement at \Documents\Acourate\LogSweep\Logsweepxx_rec.wav (xx samplerate) and/or in the workspace
The inverseXX.dbl is stored at the same document folder.
So you can use these files by the logsweep convolution.
Be aware about that the files will be overwritten with a next logsweep recording, especially with other parameters.

Acourate V2 will also save the logsweep parameters with the recorded sweep. So the inverse file is not necessary with manual logsweep convolution anymore.

[daltonleblanc2]

I need a little help on Log Sweep Extract pulses and harmonic distortion. Convolved log sweep and inverse. Loaded convolved file.

[UliBru]

Hello Dalton,

I see at least 2 points in your picture:
1. the logsweep data are not detected. The correct steps are:
- record pulse responses by the logsweep recorder. The recorded sweep is also saved in the workspace
- run the manual logsweep convolution and select the saved recording. Deselect Extract Pulses
- set the markers around the left or right peak in the convolution result
- calculate the distortions. The according window should display the correct logsweep parameters
2. the pulse display looks like a recording carried out with a USB mic. If this is the case it makes sense to check the timing (distance of Dirac pulses in the recorded sweep = Dirac option set in LSR) and to apply a SRC with a "corrected" samplerate.
The logsweep convolution/distortion calculation should be carried out on the "corrected" recording.

[daltonleblanc2]

Uli I'm getting the same screen shot. My steps are as follows using Earthworks M30
Log sweep recorder
Magnatude inversion, save file.
Log sweep convolution, save file.
Log sweep: Extract pulses & HD.
No start or end found.

[mnaganov]

BTW, Klippel has a fantastically informative poster on the sources of distortions in speaker drivers, including measuring and interpretation examples. It can be downloaded for free from their site: https://www.klippel.de/fileadmin/klippe ... Poster.pdf