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kelossus

Speakers with L-Pad. Driver SPL matching?

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With older speakers in particular a lot were outfitted with l-pads on MF/HF/UHF drivers. I have a pair here and there is no indication as to what is a flat or even response.

 

As a baseline is it sensible to sweep each driver at a given frequency within its range and match the SPL of all drivers. From there I could tweak/flavour the voicing.

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Yes. It will be good to see the manufacturers spec from your own sweeps. It may or may not look like a good graph when done but it is what it is. Measure your speakers in the same spot under same conditions and see how they compare to each other. Then tweak with the pots as you suggest to get the best sound to your ears. I'd also measure a few off axis ones 15, 30, 45, 60 to check the off axis power response as well.

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Sorry I misused the word "sweep". What I did was use a signal generator at a specified frequency within each drivers range. E.g. 600hz for Mid-bass, 5khz for HF and 15khz for UHF. I had the SPL meter 5cm from each driver and matched the SPL's with the L-Pads.

 

The L-pads on each speaker did not end up being exactly the same. Particularly on the tweeters, one l-pad is a fair whack higher but each driver is now outputting the same SPL. The drivers are 50 year old and alnico magnets are a little prone to demag so I am not too concerned with the variances.

 

I will remeasure the system shortly as this change would require a resweep for my Deqx EQ.

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I'd use the free program rew to do a sweep. It will tell you more than just singular frequency steps. You may find one of the tweeters has a dip in the frequency range where you tested but the rest is similar to the other speaker. If this was the case then the tweeter will only be matched at the frequency point where you measured and the rest may be out.

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