# 2 subs - different tuning



## dougc (Dec 19, 2009)

I have two SDX-15 that I was going to build two separate identical 6.8cu ft 19hz enclosures for. I screwed up the measurements and ended up with 5 cu ft at 22hz as my final finished product on the first one. It is suitable for movies, but doesn't have the upper end impact that I enjoy with music. I tried the SDX in a 2.375 cu ft eclosure tuned to 34hz and love the sound for music. I want both sounds. I have two EP2500 and a Reckhorn B-2

Any issues with having them tuned differently?

Would there be much difference making the higher tuned box the same size? I already have the panels cut and ready to glue

Does 5cu ft at 34hz, two 11.2" long round ports sound right?

Or would 31hz, two 8.8" long be better?



Thanks
Doug


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## Mike P. (Apr 6, 2007)

A 31 hz tuning would have less of a hump in the response compared to 34 hz. With 1000 watts and a HPF at 17 hz you're at Xmax at 15 hz. With this port air speed you need a 8" diameter port 22" long. Or Three 4" flared ports 19" long each.


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## dougc (Dec 19, 2009)

thanks Mike - is there anything I can do with the two 4" holes? The ports are loose, but the sides and bottom of the enclosure are already glued together. I want to avoid building it again from scratch if possible. I could always port the 3rd 4" out the front and use a 90 on the inside. It would barely fit behind the magnet.


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## Mike P. (Apr 6, 2007)

You can use two 4" ports 11" long each if you use a HPF around 30 hz if the input power is at max. Depending how loud you listen to the sub, you can vary the HPF with the Reckhorn if port noise is an issue.


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## SteveCallas (Apr 29, 2006)

Having one sub tuned to 34hz and the other tuned to 22hz will essentially make output below ~30hz worthless unless you run the 22hz sub twice as hot as the 34hz sub. In the ranges where both subs are playing, output will be increased up to 6db, so below ~30hz, where only one sub is doing anything notable, output is down up to 6db.

Can you make adjustments so that both subs are tuned to ~28hz?


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## dougc (Dec 19, 2009)

I could chop down the ports on the inside of the finished one to 14.35" and drop in some chamfered rings around the tubes. Using both subs was with the intention of the 6db increase. Maybe I should build the new one the same way and see how they sound together before I start chopping things up. If the output still is terrible, I retro both of them.


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## Mike P. (Apr 6, 2007)

> Using both subs was with the intention of the 6db increase.


Steve is correct, I was under the assumption one sub would be used for music and the other for music.


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## dougc (Dec 19, 2009)

You both are right in my intention! I will use them at the same time for music and movies, and am thinking that the 6db boost with both tuned the same might end my dissonance for the poor output of my finished sub. If I am still unhappy, I can always pull the sub out and shorten the ports to support a lower tune. 

I want both: low as I can go, and the boom


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