# CSS SDX15 question



## event horizon (Nov 12, 2009)

Hi again guys, been a long time unfortunately due to various issues....

Hopefully someone may be able to give me an answer before I go off & foul up in a big way :scratch:

I have four SDX15 drivers which I intend to put to good use next year when I can get my bench saw ouf of the garage. The thing is this though, I don't want to build a pair of subs, I want to make a pair of speakers :rofl2:

Now while I certainly have room for 600L per side (as long as they are kind of tall, I'm not sure I'm going to need 120Db @ 10Hz :rolleyesno: Also it'd be nice to keep them as small as possible, so I wondered about using the SDX in an Isobaric arrangement.

This would result in a ported enclosure volume of about 150L per speaker, which is nice & small :T I'd still get the same performance as two SDX15 in 300L enclosures each.

What I don't know is how noisy the rear magnet vent is going to be given a hefty drive?

Does anyone happen to know? 

Thanks in advance :T


PS, before the inevitable question arrises about the port size needed & the length of it to tune to 10-12Hz & move enough air, I won't be using a conventional port. I happened to stumble onto the Polk Powerport calculator on my travels which will allow me to make it work - just


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## Mike P. (Apr 6, 2007)

I can't speak for the motor noise but I'm curious why you want to tune it that low.


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## event horizon (Nov 12, 2009)

Hi, if you bump up the enclosure volume to 300L with a single driver (no isobaric as WINisd Pro appears to fluff it for some reason) the response is just about 100% ideal for a 4Db per octave rolloff below the lowest room mode in my room.

From what I have been reading this should result in a pretty flat response in the room right the way down to the tuning frequency. The thing is they'll be used for both music & movies, so I'd like to tune them as low as possible for two reasons 

First of these is there will be very little effect of the reflex on any music material until 25Hz is reached, at that point & below the port will influence things more. So it should sound pretty clean with music.

The second being that with such a low tune the driver will be a bit more protected from really deep sub bass signals in certain movies which I happen to possess 

I took a look at Cloverfields content a little earlier & thought I'd better not turn things up too loud :yikes:


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## event horizon (Nov 12, 2009)

By the way, does this forum accept zip files as uploads? If so I'd be happy to drop off this Powerport calculator for use by people on here.

Found it on another forum by the way, have been looking for it for a few years


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## Mike P. (Apr 6, 2007)

Yes, you can upload Zip files as long as the size doesn't exceed 9.77 MB. You start a thread for it in the Subwoofers General Discussion forum.

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/


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## event horizon (Nov 12, 2009)

Done...


So does anyone know how much noise the motor & vent on the back of the SDX15 will make facing out of the enclosure?

Help, I don't have a test enclosure to find out :rofl:


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## event horizon (Nov 12, 2009)

Well I decided to find out for myself & while I was at it I tested all 4 units  I'd hate to build anything to find one of them faulty as shipping back to the USA wouldn't be cheap 

Stuffing enough power into each them at 20Hz (free air) to generate approximately 50mm peak to peak excursion, I was immediately surprised at how little noise was generated by the vented pole on the backplate :T It appears to make more noise from the venting from the front of the magnetic assembly via the small vents in the basket between the rear spider & front pole piece, but once again nothing worth shouting about.

Any musical signal at the level I was feeding the drivers will totally swamp any noise generated, so it's good to go as all 4 drivers worked a treat :hsd:

So it's time to get designing a pair of 150L front left & right speakers :rofl:


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## Mike P. (Apr 6, 2007)

We'd love to see pics of the build process when it gets started!


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## event horizon (Nov 12, 2009)

I'd be only too happy to dump some in Photobucket & link to them, the thing is it won't be for a while yet as it's winter here & my bench saw is going to have to be outside. There will be some pretty big panels & I just won't have the room to do it in the garage :rolleyesno:

The good news is that I now know it can be done, only thing is that it'll be 180L internal volume & tuned to 11Hz. I have pretty much worked out the bass side of things, I'll have to change the shape of the interior end of the power port to kind of do a 180 instead of a 90 degree turn to get as big a port as possible to get air velocity down as low as possible. With low leaks I appear to getting an extended shelf response at -6.5Db & -7.5Db at 10Hz.

Looks like a pair should be good for 116Db @ 1M 10Hz not allowing for power compression, should be interesting :hsd:

No worries on the power amp side of things either, already taken care of by this beast  They'll be connected as an 8 ohm load where the PLM manages 2300W RMS per channel.


Once things get underway I'll get a thread going in full range speaker section :T


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