Holm Impulse analysis Scanspeak speakers

SergeDufour · 19th October 2010, 01:58 AM

I built my speakers based on a scanspeak design (see pict)
I hooked up the holmimpulse-measurements software and my laptop to my sound system and a nice Rode NT1A microphone. My towers are two ways, with two woofers and one tweeter that I built. The output is impressive and the plot too !

The result of the holmimpulse analysis (pict) is impressive but whatever is the deviation, how ones make those so called corrections to the speaker ? I love the way it sounds but if I can improve it further....

I cannot change the crossover because its design is according to specifications. I can certainly put more or less damping material inside the tower as well as changing the aperture which is toward the floor.

Advices ?

jr · 19th October 2010, 02:17 AM

Judging by the frequency response plot, there seems to be something wrong with either your measurement setup, your speakers or both.

kbgl · 19th October 2010, 02:39 AM

It looks like you have some bad measurements. Check the gating and set it to about 700 hz. Measure from about 6 or 7 feet from the speaker. Make sure only one speaker is playing. Move the speaker away from any walls or objects. Turn off the phase graph too. Post a new graph. Look only at the response above 700 hz. (for now.) You may have a sound card setting issue.

studiotech · 19th October 2010, 03:42 AM

The Rode Nt1 is not really suitable as a measurement mic unless you can make a calibration file for it. See freq response here:

http://aus.rodemic.com/downloads/nt1..._datasheet.pdf

Greg - tech - www.phatplanetstudios.com

Pano · 19th October 2010, 02:08 PM

Agree with the above, you've got some problems. Be sure to run just 1 speaker at a time. You might also try 1/6th octave smoothing on the plot. It's in a pop-up when you click the "options" button.

scott wurcer · 19th October 2010, 02:42 PM

Quote:

Originally Posted by studiotech

The Rode Nt1 is not really suitable as a measurement mic unless you can make a calibration file for it. See freq response here:

http://aus.rodemic.com/downloads/nt1..._datasheet.pdf

Greg - tech - Phat Planet Recording Studios - Orlando Florida - Audiophile Quality Recording, Mixing, Mastering, Production

I agree, the Rode is a large diaphragm mic and is not flat enough to use without cal and is also not omnidirectional. You would be better off with a small omni capsule mic.

SergeDufour · 19th October 2010, 03:17 PM

Quote:

Originally Posted by scott wurcer

I agree, the Rode is a large diaphragm mic and is not flat enough to use without cal and is also not omnidirectional. You would be better off with a small omni capsule mic.

I just realise my mistake. My mike is really a Rode NT-2a which is patern selectable, so yes omnidirectional.

And about its response : seems pretty flat to me (see pict !)

Pano · 19th October 2010, 03:50 PM

It's certainly much flatter than your measurements!

Just remember the bump at the top when you measure.

doug20 · 19th October 2010, 03:53 PM

The plot looks like it has lots of noise to me. Did you run sound card calibrations? Do you have them saved and checked before running measurements.

Your impulse should more look like this...it should not have noise in it.

Paul W · 19th October 2010, 04:56 PM

Was the crossover design optimized with actual driver measurements on your baffle?

19th October 2010, 04:56 PM	#10
Paul W diyAudio Member Join Date: Oct 2003 Location: North Georgia	Was the crossover design optimized with actual driver measurements on your baffle? __________________ Paul The Octagon

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19th October 2010, 02:17 AM	#2
jr diyAudio Member Join Date: Nov 2004 Location: Sydney	Judging by the frequency response plot, there seems to be something wrong with either your measurement setup, your speakers or both.

19th October 2010, 02:39 AM	#3
kbgl diyAudio Member Join Date: Apr 2010	It looks like you have some bad measurements. Check the gating and set it to about 700 hz. Measure from about 6 or 7 feet from the speaker. Make sure only one speaker is playing. Move the speaker away from any walls or objects. Turn off the phase graph too. Post a new graph. Look only at the response above 700 hz. (for now.) You may have a sound card setting issue.

19th October 2010, 03:42 AM	#4
studiotech diyAudio Member Join Date: Jun 2004 Location: Orlando, FLA	The Rode Nt1 is not really suitable as a measurement mic unless you can make a calibration file for it. See freq response here: http://aus.rodemic.com/downloads/nt1..._datasheet.pdf Greg - tech - www.phatplanetstudios.com

19th October 2010, 02:08 PM	#5
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Agree with the above, you've got some problems. Be sure to run just 1 speaker at a time. You might also try 1/6th octave smoothing on the plot. It's in a pop-up when you click the "options" button.

19th October 2010, 03:50 PM	#8
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	It's certainly much flatter than your measurements! Just remember the bump at the top when you measure.

19th October 2010, 03:53 PM	#9
doug20 diyAudio Member Join Date: Mar 2009	The plot looks like it has lots of noise to me. Did you run sound card calibrations? Do you have them saved and checked before running measurements. Your impulse should more look like this...it should not have noise in it.

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