test cd

[kswanson]

Probably been covered before but which track on the cd included with the sub is best to set the volume before running the sweep?

[Pete_Hsu]

Ken, the 50Hz test tone is a good starting point (I think that is track 14 or 15 on the test CD...)

Sincerely,

[godsmack129]

Can someone please explain how to do this cd with a SPL meter. I am really new to this. I have the VTF-2

[Pete_Hsu]

Hi,

Using the test tone CD with the SPL meter is quite straightforward. Start with the Radio Shack SPL meter set for "C" weighting and "slow" settings, placed at the main listening position ear level. Start with the subwoofer volume knob relatively low (say, 9-10 o'clock on VTF subwoofers, and 11 o'clock on STF/ULS subwoofers). Play the 50Hz test tone on the test CD, and adjust the receiver's master volume level until you see 80db on the SPL meter with this test tone.

So let's say that one is going to cross over subwoofer to mains at 80Hz. Write down the SPL measured from the meter for four frequencies directly above 80Hz, take the average, and then do the same for four frequencies directly below 80Hz. Then, if the average above 80Hz is, say, 3db higher than the average below 80Hz, simply increase the subwoofer channel level by +3db so that the subwoofer is level matched with the mains.

Note that you should also use the SPL meter to check that the subwoofer is in phase with the mains. When the sub is in phase with mains, one will get higher output near the crossover frequency. So before one does any level matching of subwoofer to mains, use the meter to help set the best phase setting on the subwoofer.

Sincerely,

[godsmack129]

Ok.I am doing something really wrong here .I did what you said in the first part by playing the 50hz test tone and matched it with the reciever to get 75db on the meter.And then i did what you said to do on the worksheet.This is what i got,

31.5 HZ= +3DB ON METER
40HZ = +1DB ON METER
50HZ = +75DB ON METER
63HZ = -4DB ON METER


100 HZ = -10DB ON METER
125HZ = -6DB ON METER
160HZ = 0DB ON METER
200HZ = -8 ON METER

Please can anybody please help me !!

[Pete_Hsu]

godsmack, are you using the analog meter?

Let's make this easier. Instead of using 75db @ 50Hz as a baseline, let's use 80db @ 50Hz as a baseline. Start by setting the radio shack analog meter to 80 (db) setting. Simply adjust the master volume level on the receiver until you see 0db on the meter when playing the 50Hz test tone on the CD. This means that the measured SPL is 80 + 0 db = 80db.

Now, at 31.5Hz/40Hz/50Hz/63Hz, and 100Hz/125Hz/160Hz/200Hz, write down the actual SPL that you see. For instance, if the meter shows +2 using the 63Hz test tone, then write down 82db (ie. 80 + 2) for this frequency. If the meter shows -4db at 100Hz, write down 76db (ie. 80 - 4) for this frequency. If the meter shows -7/-8/-9/-10db at any particular frequency, then you should change the analog meter to 70 (db) setting so that you can get a more precise measurement. Likewise, if the meter shows +7/+8/+9/10db at any particular frequency, then change the meter to 90 (db) setting to get a more precise measurement.

Then, show us the actual measured SPL at each of the frequencies you listed above.

Does that make sense?

Thanks

Sincerely,

[godsmack129]

Ok Pete.First Thank you for your help,and yes i am using a analog SPL meter.
I did what you said and started at 80.Here are the new numbers
31.5HZ 78
40 HZ 76
50HZ 80
63HZ 72



100HZ 70
125HZ 70
160HZ 76
200HZ 70


Now when i changed the meter knob to 70 or 90 the 100hz-200hz did not change from the numbers above.So what do you think?

[godsmack129]

Hey Pete,
By the way I am using a pioneer receiver,VTF-MK3 SUB,VT-12 SPEAKERS.And i did put my numbers in the work sheet. i am just not sure what you mean in the blue section "play 50hz warble tone and adjust subwoofer"?

[Pete_Hsu]

Hi godsmack,

When you play the 100/125/200Hz test tones, and you set the analog meter to 70 (db), does the needle rest on 0db? If so, then it is actually 70db. If you set the meter to 90 (db) position, then the needle should be off the charts (at the very min left end of the meter)...

The spreadsheet is just saying that you can use 50Hz warble tone as a baseline, so that when you play that test tone, the master volume level on the receiver is set so that the SPL meter shows 80db (or 70db, etc).

[cocobeli]

What is it that's happening just past the 3-minute mark on track 2? It sure flaps the cone on the ULS-15

—JED

[Pete_Hsu]

I think there is some ultra low frequency content on track 2 of the test CD, well below 10Hz (maybe 5Hz or something like that)? Probably just some noise on the track. The ULS-15 is one of the only subwoofers out there where you can hear that noise.

[bsoko]

Hi,

Using the test tone CD with the SPL meter is quite straightforward. Start with the Radio Shack SPL meter set for "C" weighting and "slow" settings, placed at the main listening position ear level. Start with the subwoofer volume knob relatively low (say, 9-10 o'clock on VTF subwoofers, and 11 o'clock on STF/ULS subwoofers). Play the 50Hz test tone on the test CD, and adjust the receiver's master volume level until you see 80db on the SPL meter with this test tone.

So let's say that one is going to cross over subwoofer to mains at 80Hz. Write down the SPL measured from the meter for four frequencies directly above 80Hz, take the average, and then do the same for four frequencies directly below 80Hz. Then, if the average above 80Hz is, say, 3db higher than the average below 80Hz, simply increase the subwoofer channel level by +3db so that the subwoofer is level matched with the mains.

Note that you should also use the SPL meter to check that the subwoofer is in phase with the mains. When the sub is in phase with mains, one will get higher output near the crossover frequency. So before one does any level matching of subwoofer to mains, use the meter to help set the best phase setting on the subwoofer.

Sincerely,

What if you have a digital meter from Rat Shack?

Bill

[Pete_Hsu]

You mean what about the digital meter in terms of correction factors?