[Capmerkev]

Hi, I was wondering how much of a difference it makes to only use the line in with a RS meter without soundcard calibration, for measuring with the RTA and the pink noise file burned onto a cd with the output muted for a rough measurement of low frequency room response.

The reason I am asking is that I only have a laptop and a RS meter. I live in a small Canadian town and I cannot find a external sound card.

I have a two channel audio room and for the moment I am only trying to find the best bass response for seating/speaker position so I am only looking at a narrow frequency range.

 

[NCDave]

Hi Kevin. I've not used RTA.

But if you are just looking for the best place for speakers and seating, and not worried about trying to do any equalization right now, then you are doing a relative measurement, not an absolute measurement. "Relative" in this case just means "what's better"? So, I'd say you are just fine with no calibrations at all for quick-and-dirty relative measurements.

When I was looking for a good place for my sub, I just put the sub at the listening position, and played some bass tracks, while checking various possible sub locations with the RS meter. Your better because, even without a calibration, severe peaks and nulls will show up and are likely to be more-or-less valid (you'll know they are there, just not exactly what level they are at.)

This all assumes you are able to get your laptop settings and RS meter connections proper in order to get a graph to appear in RTA.

 

[brucek]

I live in a small Canadian town and I cannot find a external sound card.

We know you have the internet, so why don't you simply order one on-line?

You require an external soundcard with a line-in and line-out. The laptop will usually not have a line-in. That's a requirement.

brucek

 

[NCDave]

Hmmm, already having the Line In was kind of implied in the first post...

Capmerkev, if you are thinking "Line In," but actually only have a "Mic In" on your laptop (like I have on mine), the RS meter levels will probably be too high.

Also, the external sound card that lots of people use here is not available any more (or hard to find), but they have a new version which might work ok, called "Creative Labs Sound Blaster X-Fi Surround 5.1 24-bit USB External"

 

[Capmerkev]

Sorry perhaps I should have explained this a little better. I not sure if I know less about room acoustics or computers.

For the moment I am trying to find the best low frequency response seating/speaker position for a two channel audio room. I do not intend to use an EQ, but in the future I will be adding room treatments.

Yes, I did mean mic in and do realize that I will not get a truly accruate measurement from a laptop without an external soundcard.

I have a small room which certainly does not have a very flat frequency response(previously I had been trying to use a test cd with low frequency sine waves and the RS meter but found it could take a very long times when trying to test multiple postions).

I was off work this week and had intentions of finding the room responses. But when I tried to find an external sound card I found that I will have to try to order one from somewhere(nobody could help me locally). Realizing this will take anywhere from a week to month to get one. By that time my week is over and I am back to work.

I been playing with REW and speaker/seating positions on my time off. What I had done was copy the Pink Noise PN file and burnt it on to cd. I muted the output volume of the laptop and used the cd to check levels to set the input level to -18 and calibrated the slp meter to 75db with the cd. Then I used the pink noise pn cd with the RTA and was only looking at the 20-300 range. I was not using a soundcard calibration file which measured similar to the output of the builtin laptop speakers(no bass,lots of midrange, and limited highs, cannot expect anything less from these type of speakers).

My thoughts had been that muting the output of the computer, not using a soundcard calibration file and playing the cd from my stereo the effects of the soundcard would be lessened. Although I still used the mic input, I had set it to -18 on the meter level and set the spl to 75db which never drove into clipping with the pink noise.

Anyway I do understand that I cannot get a truly accurate reading without a proper soundcard. I guess I was only hoping if this show where might be close to best place for positioning by looking at the peaks and dips and trying to find the smoothest response. Do you feel that this could put me in the close ballpark until I can get an external soundcard, and then I would only have to do some minor positioning tweaks for a flatter response.
thanks for your time

 

[brucek]

My thoughts had been

Incorrect, unfortunately. The mic input has horrible response characteristics and makes the measurements meaningless.

Buy a soundcard and do it right, it doesn't take that long once you get set up. There will surely be a day in the future that you can do it. Until then, enjoy your system....

brucek

 

[NCDave]

I'm not going to be of any help here, Kevin. I'm not sure of the procedure for RTA.

I do know that the Mic In level is much different from Line In. Mic In is WAY more sensitive than Line In. So you're going to have to dial the input level way down to compensate for the relatively high output level from the RS meter.

Will it work to get a graph to appear in RTA? Yeah, maybe. If you have the time to play with it, and are not worried about damaging the Mic In, then go ahead and play. But as brucek explained, the results may not be all that meaningful. It would be interesting to see if you can get any decent curve without having a ton of noise in it.

If you are going to play, I would suggest that you try to stay in the lower end of whatever range you are using on the RS meter. That will help keep its output level lower so you don't have to use as much attenuation on the computer.

 

[Capmerkev]

I do appreciate your responses and hope I did not sound like I was trying to disagree or disregard any advice. I was only trying state what I had meant a little more clearly.

I had been looking forward to trying to tune my system a little better during my time off. But was a little heartbroken when I found I could not buy a soundcard in time. I was just trying to make the most of my situation.

As I said earlier, I do not know much about computers(aside from turning them on/off and going onto the internet). As Dave stated, the soundcards that a lot of people use here are not made anymore. And I am unsure which ones will work correctly with REW.

I have been looking on the internet for a soundcard, but I have been trying to look within my own country if possible (absolutely nothing personal, only trying to keep my shipping costs down and avoid the black hole they call Customs). From the sites I looked at there is much available, but I did see the Creative Labs Sound Blaster X-FI Surround 5.1 24 Bit USB External which Dave had mentioned

Will this be an acceptable soundcard for using with REW?

 

[Capmerkev]

Hi maybe another question is would be will this be compatible with my computer?
This is probablya simple answer for someone that has a little understanding about computers.
I have a laptop with Windows XP and a Intel Centrino Duo processor.
I looked in the system requirements section for this soundcard( sorry I am unable to provide a link) on Creative Labs website.
Windows XP seems to be fine but I am unsure of the processor.
It says I need an Intel Pentium 4 1.6 GHz, ADM Athlon XP 2000+ or equivalent processor.
Looking in my system properties I believe I have 2 Intel Core 2 proccessors.
Is Intel Centrino Duo the same or equivalent as Intel Pentium 4?
Please let me know if I should have asked this in a different section