Re: Free download spectral analyser.



Iain Churches wrote:

"west" <nospam@xxxxxxx> wrote in message
news:JCa4i.4904$qp5.1653@xxxxxxxxxxx

"maxhifi" <no@xxxxxxxx> wrote in message
news:PJ94i.200007$DE1.48419@xxxxxxxxxxxx
2nd the vote for TrueRTA - it's nice software

BUT

watch out for noise from your sound card contaminating the results,
especially at low levels, and mic calibration is multiplying the errors
of
your mic times the errors of your soundcard.

It's much better to get a dedicated meter if you're doing serious work -
for
example the Quest Soundpro is a really nice instrument.


"Kalman Rubinson" <kr4@xxxxxxx> wrote in message
news:qop153tpfabdff9s9su1sufeokopmsu342@xxxxxxxxxx
On Mon, 21 May 2007 00:18:40 GMT, Patrick Turner
<info@xxxxxxxxxxxxxxxxxx> wrote:

What the best free software download for
audio analysis at least 20Hz to 20kHz, or wider BW?

I tried Steve Ekblad's site with a lot of stuff but nothing I
downloaded
and saved
in my program files would set up and run automatically.

I want to set up a dedicated W98 PC to just provide the displayed
response from
speakers in my test room instead of using my slow manual 1/3 octave
filtering
analog unit.

TrueRTA is free for the low-rez version and higher rez options are
inexpensive. It is a basic RTA.

RoomEQWizard is not a spectral analyzer but it is a superior tool
suite for measuring speaker response in-room. It's free, too.

Kal

Hi Kal: What sound card, without breaking the bank, would you recommend
that will be good for most of the audio programs and tests (good S/N, IMD,
freq response, etc.)? Perhaps good enough to enjoy some CDs while working
and transferring LP to CDs should fit the bill.

Hi West. You need to be able to see and measure what is happening
way beyond 22kHz, particularly if you are concerned with phase
shift and stability issues. That's why so many workshops seem still to
use dedicated instruments.

Cordially
Iain

Thankyou everybody for the response to my question..

I only want to measure speaker behaviour with the software,
to save precious time.

Presently, I use old fashioned analog gear I built myself.

This gear has a pink noise source, with flat distribution of energy
from 20Hz to 30kHz when filtering with a bandpass filter with same Q =
12 along the band,
and the filter I built is an opamp with bridged RC T filter in the NFB
path and some slight
positive FB to raise the Q, but give the same level and shape of
selectivity acoss the
band.

The band is divided into 3 sub bands 20-200, 200-2k, 2k-20k,
and the filter R elements are switched to give filter F0
at 20, 25, 32, 40, 50, 60, 70, 85, 100, 130, 160, 200 for bass
and x10 for mids, and x 100 for treble, simple.

Si I have 33 rest F for the whole audio band and I find it
just tells me enough.

Microphone is a home made electret with guranteed response from Hi-Q
International in Melbourne.

Mic signal is amplified and sent to the filter, and a peak reading amp
with slow
decay detects the noise signal and converts it to a slow decaying dc
voltage.
This feeds another opamp with logarithmic transfer and this powers a
125mm wide
analog meter which is zeroed by level to the centre position.
Voltage levels from the mic are displayed in db steps, to the meter then
easily
reads +/- 20dB levels each side of centre, ideal for audio measurements
because
many speakers I test after working on them have large unwanted response
variations
with first attempts to get them flat after the first trial of the
theoretical crossover.

It would make things a lot easier if I could just move the mic around
and get say
6 quick responses within a metre of the listening position,
then average them all.
Making 6 response tests with each one taking 15 minutes by using the
switchable
bands and F switch takes a lot of time if I take 6 tests.

Rooms are not perfect, but I have some speakers which measure quite well
in my rather nice large room. My efforts as a builder 30 years ago
left a valuable enduring legacy.
Getting any speaker to give a +/- 2dB response at 4 metres
is doing alright; many high brow brands measure +/- 6dB.

At the moment, I have got the ER Audio ESLIIIB panel ready again for
another test.
Its the fifth time I have stretched a membrane, and this time with over
twice the
0.8Kg recommended membrane tension.

I also have coated the stators with about 0.8mm thick layer of silicone
to prevent the membrane getting too
close to the stators and remaining stuck, as soon as the bass LF signals
swing the membrane
over what seems to be a critical distance.

I will be having more to say soon in another post about the progress
with the ER Audio ESL III3 kitset that
I have been really struggling to assemble.

But to facilitate the measuring process, and maybe even try measuring
amplifiers, I will find a good PC program set up in a spare W98 based PC
to be quite useful.


I will try to dowload and instal what some of you have so kindly
suggested.

Iain mentioned pc software for audio analysis had limited bandwidth, and
I'd agree;
one needs more than 20Hz to 20kHz for amps; more like 1Hz to 1MHz,
so until I do get something more soopery doopery to do what the free
download pc software cannot,
the reliable methods with CRO and meters and some home spun THD/IMD
measuring kit
will continue to play the major role.

Patrick Turner.
.

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