• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

3 way DSP XO

RayDunzl

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,200
Likes
16,982
Location
Riverview FL
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia

Short speaker cables. The amp would have to reside in the AV cupboard and would require about 15m of speaker cable. I wouldnt have the amp next to the speakers. Much better to run the balanced input signal over that distance to the speakers.
 

Fitzcaraldo215

Major Contributor
Joined
Mar 4, 2016
Messages
1,440
Likes
632
Short speaker cables. The amp would have to reside in the AV cupboard and would require about 15m of speaker cable. I wouldnt have the amp next to the speakers. Much better to run the balanced input signal over that distance to the speakers.

Makes sense from an economic packaging point of view, and I do believe in short speaker cables where possible. Might need a long power cord to the speakers, but so what.
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Ok, some measurements. This was a quick and dirty, Acourate corrected measurements were taken at the listening position without having linearised the drivers first. Mainly I was being impatient :) , but this way I can see if there are significant differences when I do get to linearise the drivers. Measured with an Earthworks M23.
XO at 600Hz and 5kHz with Acourates default Neville Theile 2nd order.

xo response.PNG


Frequency Response - Im tilting down from 1kHz to about -5dB 24kHz

The intention is to use 2 subs crossed over at 50Hz, but this is just the speaker.

FR.png


Distortion - need to check out the Woofer distortion, higher than expected. Seems odd, wondering if REW is ok with the delay the convolver is making and tracking harmonics through the sweep.

Distortion.png


Impulse response - wow. might look at fine tuning with the pre ringing

IR1.png


IR2.png


Group delay

GD.png


RT60 - Pretty much within EBU studio recomendations

RT60.png


reverb2.PNG


Clarity - Still havent got to grips with this measurement

Clarity.png


Waterfall

waterfall.png


waterfall2.png


IACC

IACC.PNG


How does it sound? Clean, clear and neutral, but not in a boring way, just no emphasis on any part of the frequency range. Very dynamic with instruments separated out in the mix very easily. Big improvement in soundstage/envelopment. Very pleased so far, some of the best sound I have had at home.
 
Last edited:

Brad

Active Member
Joined
Nov 8, 2016
Messages
114
Likes
35
You may want to use acourate for the distortion measurements, letting the log-sweep recorder apply the filters. See Mitch's book for a good description.
I'll have to go and look up what this clarity measurement is now...
 

RayDunzl

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,200
Likes
16,982
Location
Riverview FL
Distortion - need to check out the Woofer distortion, higher than expected

Use single tone on woofer/low frequencies to verify. RTA works for that.

Music rarely "sweeps" anyway.

---

There's a new Stepped Sine Test (not swept), also, available from the RTA window (newest REW versions). I tried it like once.

---

Let's see the phase display, too. Maybe L/R/Both.
 
Last edited:
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Use single tone on woofer/low frequencies to verify. RTA works for that.

Music rarely "sweeps" anyway.

---

There's a new Stepped Sine test, also, available from the RTA window. I tried it like once.

---

Let's see the phase display, too.

Will try it out. Thanks

Phase left

phase.png


right

phase right.png


GD

gd 2.png
 
Last edited:

RayDunzl

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,200
Likes
16,982
Location
Riverview FL
Phase - ok, similar to my JBL at listening position. It straightens out a lot if measured nearfield. I blame Wide Dispersion reflections, since the panels can throw a flat phase to the listener.

At the couch. Blue JBL, Green MartinLogan

upload_2017-7-26_23-34-31.png


Somtimes the first kink is as low as 200Hz or so, passive cross to woofer is 180Hz
 
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
I will measure the corrected system tonight with Acourate but here is the pre correction phase and GD (just the XO) measurement.....mmmm....

phase.PNG


gd.PNG



Convolution test output

phase
conv phase.PNG


GD
conve gd.PNG
 
Last edited:

Cosmik

Major Contributor
Joined
Apr 24, 2016
Messages
3,075
Likes
2,180
Location
UK
Phase - ok, similar to my JBL at listening position. It straightens out a lot if measured nearfield.
A few thoughts:
1. Measuring phase and therefore frequency response at the listening position is like using a camera without a lens to measure the performance of a TV - reflections bouncing around the room fall on it. The image looks 'random' but it isn't - it is consistent with the room. Frequency response and phase response are tied together. A lens can make sense of it, as can deconvolution.
2. Our hearing seems to be the audio equivalent of a lens - we "hear through the room" as Floyd Toole says, or we can consider our hearing to be deconvolving what falls on our ears to isolate the source; we can identify a neutral speaker regardless of the room. If we attempt to 'correct' the no-lens image, then when we fit the lens, we will reveal a now-unnatural image. I think this is one of the reasons that DSP does not yet have a great reputation - people haven't thought it through and, armed with the tools, are mistakenly going into flat-line frenzy because they can.
3. Near field measurements work until the wavelengths of the frequencies you are measuring get short compared to the diameter of the transducer.
4. Our audio antecedents built anechoic chambers for a reason - if only the measurement at the listening position matters, why did they bother? We can get the same benefits in an ordinary room by combining low frequency near field measurements with pseudo-anechoic gated measurements at higher frequencies.
5. Non-ideal dispersion will interact with the room, and cannot be totally corrected for. There is always going to be some subjective element to this. However, dispersion can be improved 'at source' by various measures such as going three-way instead of two, etc. The Kii Threes of this world do it actively by design. The remaining effects can be predicted and corrected for with theoretical curves whose depth is set by ear.
 
Last edited:
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
OK, here are the acourate measure results of amplitude Phase and group delay

Not consistent with REW, BUT REW may be upset by the massive convolution delay (0.7secs) even though I did use the "wait for timing reference" option.

Acourate / REW experts, ideas? :)

upload_2017-7-27_18-1-28.png


upload_2017-7-27_18-2-24.png
 
Last edited:
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Cant seem to get the distortion calculation to work, just says the selection is too short??????

Anyhoo re-measured with REW, direct and close. Bugger all wrong with this.

distortion1.png


distortion2.png
 
Last edited:

RayDunzl

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,200
Likes
16,982
Location
Riverview FL
Cant seem to get the distortion calculation to work, just says the selection is too short??????

Single tone?

Maybe I misunderstand, but, I meant:

Use the Generator tool to make a sine wave
Monitor with the RTA window and its Distortion Panel (numerical display)

example:

upload_2017-7-27_15-54-35.png
 
Last edited:
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Thanks, Ray, understood, just didnt have time last night to try out. I did the sweep just to check there wasnt anything untoward going on, which there appears not to be. I will try the single tone tonight.

BTW the "too short" error was from acourate not REW.
 

RayDunzl

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,200
Likes
16,982
Location
Riverview FL
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Hi Ray, performed the single tone distortion measurements. Mic was at about 3cm with volume set to about 85 dB at 1 metre, so not blasting. Distortion seems nice and low, increasing at very low frequency but that is to be expected and will be a non issue when the sub is integrated.

Woofer. XO will be 50Hz to 700Hz
20hz.jpg 30hz.jpg 40hz.jpg 50hz.jpg 60hz.jpg 70hz.jpg 80hz.jpg 90hz.jpg 100hz.jpg 200hz.jpg 300hz.jpg 400hz.jpg 500hz.jpg 600hz.jpg 700hz.jpg 800hz.jpg 900hz.jpg 1000hz.jpg stepped.jpg
 

Attachments

  • 20hz.jpg
    20hz.jpg
    139.8 KB · Views: 161
Last edited:
OP
March Audio

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
6,378
Likes
9,317
Location
Albany Western Australia
Hardly seems worth performing the additional driver linearisation in Acourate. Their basic response from close in measurements are generally +- 1dB within the ranges I will be using them. I think Mitchs advice in the book said +-2 dB.

fr1.png fr2.png
 
Last edited:

RayDunzl

Grand Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
13,200
Likes
16,982
Location
Riverview FL
That all looks pretty satisfactory to me...

Good job.
 
Top Bottom