Freq Sweep

[ezc]

This may be a dumb qusetion, but how can I do a FR Sweep in my room with my spl meter & test tones,to test my sub? Once done how should I adj my sub?

[Dr. Spec]

http://clubpolk.polkaudio.com/forum/showthread.php?s=&threadid=8824

Go to the last post for starters.

[burdette]

http://members.tripod.com/~terryctheater/shivaphotoalbum/page11.html

That is the site.. do these correction factors look like the correct ones? I'm really leaning towards picking up the RS cheap meter today.

10Hz add 20
12.5Hz add 16.5
16Hz add 11.5
20Hz add 7.5
25Hz add 5
31.5Hz add 3
40Hz add 2.5
50Hz add 1.5
63Hz add 1.5
80Hz add 1.5
100Hz add 2
125Hz add .5
160Hz add -.5
200Hz add -.5
250Hz add +.5
315Hz add -.5
400Hz add 0
500Hz add -.5
630Hz add 0
800Hz add 0
1kHz add 0
1.25kHz add 0
1.6kHz add -.5
2kHz add -1.5
2.5kHz add -1.5
3.15kHz add -1.5
4kHz add -2
5kHz add -2
6.3kHz add -2
8kHz add -2
10kHz add -1
12.5kHz add +.5
16kHz add 0
20kHz add +1

[Dr. Spec]

Yes, these are the same CFs as one the other site. I use both sites - I just had that other one bookmarked so I used it.

The RS meter is an outstanding value for $35. You will never regret getting one. I have a spreadheet which autmatically factors in the CF at each frequency in the sweep. I already sent it to HBomb. You can use it too if you want.

Doc

[burdette]

Given that the sweep has many more frequencies than there are correction factors, what did you do for the tones between corrections? Extrapolate? Average?

I just made a CD and a speadsheet covering 40 tones, but there are only 11 frequencies that sort of match up for the corrections, and even those don't match up cycle to cycle....

Thanks.

I just realized that I missed the 100 Hz tone when I made the CD... not going to burn a new one for that.. but it does mean my last reading will be 94.4 but the final correction is at 80.... anyway....

[burdette]

Guy1: Can I help you find something?

Ya, I'm looking for the $30 sound pressure level meter that Radio Shack carries... the analog version.

G1: ... uh.. sound pressure?

Ya, you hold it in your hand.. it has a microphone on top, you use it to measure sound pressure levels...

G1: I think that would be over ....... [walk walk... nothing..] Do we carry a sound pressure level meter that you hold in your hand?

Manager1: Sound PRESSURE?? I think we have sound level meters. Sound PRESSURE?

Ya, esss peeee elll... sound pressure level meter...

[meanwhile G1 checks computer]
G1: We're supposed to have the one in the back. [walk walk]

I want the analog version, with the meter that swings back and forth (appropriate hand gesture)...

G1: Here it is... this is the digital version...

You don't have the analog?

G1: No.. this one is digital.

How much is that one?

etc etc etc.

They checked another store in town and that RS had one.. the display... but it was on sale, so I am a happy new owner.. even if I about stumped the RS staff.....

I guess to be fair, the box does say "Sound Level Meter".. but I would've thought they might've heard of SPL before....

[Dr. Spec]

Ha! What an experience! RS is selling a ton of those things - you'd think they'd be a little more up on the product.

Anyway, good deal - ya got an analog one!

As for the CFs, obviously the best is to interpolate. If you want my interpolated numbers for the RS CFs, just let me know and I'll email you the file Excel file which does it automatically.

Even if you make an educated guess at values between numbers it will be close enough. The important thing is that the CF gets progressively larger as the frequency drops but it becomes a non linear progression towards the 20 Hz and below range.

Doc

[Kenneth Swauger]

Hello,
I have a modification that can be done to the Radio Shack SPL meter that improves the low end response. It involves changing the inter-stage coupling capacitors. If you'll give me your U.S. Mail address I'll be happy to send it.
Regards, Ken

[VE6OHV]

Ken

I would love to get that info. on the correction for the rat shack meter - Tho I have a canadian mailing adress - Does that work for ya?

[Dr. Spec]

http://www.gti.net/wallin/audio/rsmeter/33-2050/33-2050.html

Here ya go guys. Save the stamp Ken, unless your data shakes out differently that this write-up.

Sunfire has a similar write-up in its owner's manuals.

Doc

[tryrrthg]

For everyone that has been looking for test tones I found these... I haven't tried them but if someone can try them and let us know how they work that would be great!

http://www.snapbug.ws/sinewaves/

[burdette]

What are you guys doing.. do you download these and play them as MP3s? Or do you convert them to CD format?

I burned a disc on Friday but am not that happy with it.. just not sure of the quality of the tones I found.

I'm downloading all the ones from the link above and will burn a disc today... so which format?

I can play MP3 files on my DVD player.. well, heck, I guess I can play it on the DVD player regardless... I can play it on our old CD player only if I convert to CD format.

Just curious...

[tryrrthg]

I plan on burning them to a CD. that way they can be used on any player. You can probably try both ways and see what works best, since CDR's are only about 50 cents a piece...

[ezc]

Dr. Spec
Thanks for the info, I have not had a chance to try it yet let alone watch any movies. Been a busy week, I should get a chance early next week. Ill post when I get it done.

Thanks