testing - Home Theater Forum and Systems - HomeTheaterShack.com

Old 09-21-09, 07:23 AM Thread Starter
Shackster
speedie

Join Date: Aug 2009
Location: fremantle west aussie
Posts: 47
testing

I was wondering if crossover verification could be achieved by the use of only a sound pressure meter
Would this idea work?
With testing for db drop in xo area could we say remove the minus lead from each driver to get readings i.e. check woofer only followed by each driver in order
It seems to me that db should be similar to say series or parallel concepts
I guess what I am trying to say is that if there is a db variation then the crossover is not a flat response?
Would anyone like to shed a little light!
Cheers speedie
speedie is offline

Old 09-21-09, 07:54 AM
HTS Senior Moderator

Join Date: Apr 2006
Location: Katy, Texas
Posts: 8,809
Re: testing

Not sure what you're saying there - remove the minus lead from the speaker and it won't work.

There is a way to check crossover function with an SPL meter. A bit crude and not highly accurate, but it will verify if it is working or not. You’ll need some sine wave tones both at the crossover frequency and an octave higher or lower (depending on if you’re checking a high pass or low pass).

For example, let's say your receiver has an 80 Hz crossover with a 24 dB/octave slope. If wanted to check if the crossover for your main speakers was working (high pass), you’d take a reading of an 80 Hz sine wave at say, 90 dB. One octave below 80 Hz is 40 Hz, so if the crossover is working properly, a 40 Hz sine wave should read somewhere in the neighborhood of 66 dB (90 dB - 24 dB = 66 dB). Make sense?

For a subwoofer (low pass), it would be the same thing, only the sine waves would be 80 Hz and 160 Hz.

If you don’t know what the crossover slope is, this method will give you an idea, by how much less the second sine wave reads compared to the first – i.e., 12 dB, 18 dB, etc.

You can download sine wave test tones at the link for the BFD Guide at the top of the page, if you need some.

Regards,
Wayne

Wayne A. Pflughaupt is offline
Old 09-21-09, 08:14 PM Thread Starter
Shackster
speedie

Join Date: Aug 2009
Location: fremantle west aussie
Posts: 47
Re: testing with SPL meter

Wayne cheers
what i was trying to get my head around is this
We all try for a flat response with crossover design so if the lead to the woofer was removed it would add nothing to the meter reading so the spl is coming from the other drivers etc etc.
Would this give some indication to which driver is inefficient
having said that if the graph depicts a flat response and we know that the point is lower ie 6,12,18,24 points lower, where does the extra db come from to get our flat line response?
cheers Speedie
speedie is offline
Old 09-22-09, 07:49 AM
HTS Senior Moderator

Join Date: Apr 2006
Location: Katy, Texas
Posts: 8,809
Re: testing with SPL meter

Okay - I get it now.
Quote:
speedie wrote: View Post
Would this give some indication to which driver is inefficient
It could, yes
Quote:
having said that if the graph depicts a flat response and we know that the point is lower ie 6,12,18,24 points lower, where does the extra db come from to get our flat line response?
From the output of the next driver, that is "picking up" where the other leaves off.

Regards,
Wayne

Wayne A. Pflughaupt is offline

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