How low my sub goes

[Brox]

How do I find out how low my sub goes at +-3 db? can you buy disks with different bass frequences on them to play. This way i can experiment with positioning etc.

Can anyone help?

 

[Jase]

Hi

You can download them. Burn them onto a CD and then play them. SINO10.mp3 is 10hz, SINO11.mp3 is 11hz and so on etc etc

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

Or try www.stryke.com for another test disc (Not tried these myself though!).

cheers

 

[Brox]

Thanks very much Jase - download in progress.

Can I use a normal SPL meter like the one from Tandy to measure the o/p.

 

[Jase]

Originally posted by Brox
Can I use a normal SPL meter like the one from Tandy to measure the o/p.

Yep, sure can. Also best to set your amp to Pro-Logic mode or PL2 - Cinema to get a better idea of what the sub is doing, re crossovers etc.

 

[Charlie Whitehouse]

Don't forget if you want to measure the response accurately, you need to make some adjustments to the raw measurements you get from the Tandy spl meter - it's not very accurate at the frequency extremes. See this earlier thread for a table of correction values.

 

[uncle eric]

Very good point Charlie
Eric

 

[Jase]

Thanks Charlie!

Forgot that important bit.

 

[Nic Rhodes]

just as a side point there is huge variability between Tandy meters as well as the inaccuracies!

 

[Charlie Whitehouse]

just as a side point there is huge variability between Tandy meters as well as the inaccuracies!

I have long suspected this but don't have any objective proof. But you do see quotes like this that suggest the inaccuracies are uniform across different examples of that meter model.

If you want to be truly accurate you would need a much higher instrument grade microphone & meter which would cost more than most of us would be prepared to pay.

I guess it's all relative and you get what you pay for. Within the +/- 3dB limits that Brox was talking about, those correction values should get him 'closer' to the true values, if not necessarily spot on.

 

[Nic Rhodes]

Originally posted by Charlie Whitehouse

If you want to be truly accurate you would need a much higher instrument grade microphone & meter which would cost more than most of us would be prepared to pay.

This is what I had to do. I now officially have 4 sound meters though I have basically given one to my dad. New one cost me an arm and leg though I can measure mechanical noise on players and accurate to 0.1dB.

 

[Brad_Porter]

Sorry - bonehead here.

When you say adjustments to the Tandy SPL, what exactly does that mean?

Are you saying that if you were measuring a 100Hz sound, which was reading 75db on the meter, the actual reading would be 77db as, according to the adjustment chart, toy need to add 2db?

Also, when you burn these onto a CD, do you have to convert the files to WAV or something for them to be able to play on a DVD Player....?

Sorry to be a pain............

 

[Charlie Whitehouse]

Exactly.

I'm also assuming that you'd be following the normal instructions when using one of these meters to set SPL levels and setting it to 'C' weighting and Slow response. In the 'C' weighting mode the meter will give the flattest response of which it is capable.

 

[Brad_Porter]

Thanks Charlie,

Also, do you point the SPL straight at the speaker or just hold the microphone to the air and measure each speaker that way? Is there a set time to hold it there etc......

Any tips for as near accurate as you can get with Tandy equipment would be lovely.

Regards,
Brad

 

[Charlie Whitehouse]

The normal recommendation is NOT to point the meter at the speaker in question. You should stand behind your normal listening position, facing forward, holding the meter at arms' length, so the meter is about where your head would be if you were sitting at the listening position, with the meter angled away from you at about 45 degrees.

Of course practical considerations may get in the way of this!

As for your question about burning .mp3s to disk for playing in a DVD player, you could try a search of these forums, or others here would be much better placed to advise you than me. It may depend on the capabilities of your DVD player.

 

[Brad_Porter]

Thanks Charlie.

BTW, I have just had a look at your Gallery of equipment. You have made me feel quite sick.

I think that you should sell up and immediately ship straight to me.

Cheers.
Brad