[daMaster]

I'd like to use Sound Forge to generate all the test tones I need to measure my subwoofer's in-room response (from 10 Hz to 200 Hz). Can anyone please tell me what parameters I should use when synthesizing with Sound Forge:

(1) Waveform shape: sine, absolute sine, square, saw, triangle, etc.? I assume its sine, but would like a confirmation please.

(2) Amplitude: 0 db? Or less? Does it matter?

 

[Terry Montlick]

Sine. All the other waveforms simply add higher frequency harmonics.


0 dB amplitude will give you maximum signal-to-noise. This is more than adequate for any subwoofer. Just make sure the volume isn't cranked up too high.


- Terry

 

[daMaster]

Thanks much Terry! So should I use a lower amplitude than 0 dB, like -12? If I use the 0dB test tone, what level should I be looking for on my SPL (by lowering/raising my master volume control on my AVR)?

 

[daMaster]

Never mind my last post, I don't know what I was thinking! Of course, I want maximum signal-to-noise so I'll go with 0 dB amplitude.

 

[Ethan Winer]

DM,


> I want maximum signal-to-noise so I'll go with 0 dB amplitude.

 

[knutinh]

why are you using a "stone-age" measurement method such as test tones?


K.

 

[Ethan Winer]

Knut,


> why are you using a "stone-age" measurement method such as test tones?

 

[knutinh]

Have you tried the mls measurements of Angelino Farina?

http://pcfarina.eng.unipr.it/aurora/home.htm


Free plugin to the syntrillium cool edit software (now adobe)


MLS/synchonized swept sine gives certain advantages:

*time windowing (for direct sound or reflected sound)

*better frequency resolution

*All information is contained in an impulse response, meaning that a single measurement may be postprocessed to give you any information that you want

*good snr characteristics




regards

Knut Inge

 

[Ethan Winer]

Knut,


> Have you tried the mls measurements of Angelino Farina?

 

[daMaster]

Thanks for the responses folks. I just measured all the test tones I generated and I don't seem to have any hole between 10-200 Hz, so that's good news.


Just one more question: when measuring these test tones should I set my receiver's bass out to: SWFR or BOTH (both meaning sub and front speakers)? I watch movies with it set to BOTH, so I should be measuring frequency response that way, right? Or do I only wanna be measuring frequency response of my sub (by setting bass out to SWFR)?

 

[Ethan Winer]

DM,


> I don't seem to have any hole between 10-200 Hz I watch movies with it set to BOTH, so I should be measuring frequency response that way, right?

 

[daMaster]

Quote:

Originally posted by Ethan Winer DM, > I don't seem to have any hole between 10-200 Hz

 

[Ethan Winer]

DaM,


> based on the graph I plotted with the frequencies I measured at, the frequency response curve was pretty flat I had a dip at 63 Hz which I managed to resolve

 

[daMaster]

Actually, I used this spreadsheet that I found on this forum as a basis for my test tone frequencies and I thought it was a generally well-accepted test on this forum: SPL Compensator

 

[Ethan Winer]

Da,


> I thought it was a generally well-accepted test

 

[daMaster]

I'm a big fan of proper calibration, and that's why I bought an SPL meter, DVE and Avia to fine tune the sound and picture of my HT. Despite that, I'm not a die-hard hardcore calibrator, and having done the 3rd octave freq. response check and having resolved a minor dip at 63 Hz, I'm very happy with the way my HT sounds. Don't you think that for most general, mainstream calibration purposes a 3rd octave test is sufficient?

 

[Ethan Winer]

DaM,


> Don't you think that for most general, mainstream calibration purposes a 3rd octave test is sufficient?

 

[catapult]

Quote:

Then you measured wrong. Every room in the world has peaks and severe nulls

Some rooms are worse than others. Ironically, small, purpose-built sound rooms with solid construction are much worse than than a typical open-floor-plan living room with stud walls, lots of windows and lots of doors and openings to other spaces. In an open, light construction room, with careful positioning of the money seat and the speakers well away from the walls, you can usually avoid deep nulls if you work at it a little. The "bass traps" were built in by the architect and the contractor.

 

[Ethan Winer]

Cat,


> In an open, light construction room, with careful positioning

 

[knutinh]

But do you need more resolution than the ear has?