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Should I port block my SVS 20-39 PC+?

1130 Views 6 Replies 4 Participants Last post by Ron Temple, Dec 29, 2005

DavidHir

Discussion Starter · Dec 28, 2005

Just received my 20-39 PC+. I got it calibrated with the rest of my system last night and I am very impressed.

However, I'm not sure whether I should port block or not.

I am looking for the deepest, tighest bass. And I generally don't listen to super loud levels (usually no higher than negative 6.5 db on my receiver). It for home theater use only.

My room is about 4500 cubic feet (17 X 19 X 18 at ceiling peak). Also, there are two large openings into the room (kitchen and foyer).

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OvalNut

· #2 · Dec 28, 2005

That's a pretty big room to fill, and my initial take is to leave the ports open and run it in 20hz tune. That way you won't be potentially compromising dynamic range and/or risk bottoming it when playing at louder levels.

It doesn't take long to plug one port, set the subsonc filter and bump up the subwoofer level at the receiver 1.5db. Try it and see if you like the sound better that way. Try it with some very demanding bass demo material, and start out a little below your normal listening level. Then keep rerunning that same scene at 1db higher increments until you reach your normal listening level. As long as the sub doesn't bottom or produce noticable port noise you should be safe. At that point it's a question of whether you like the sound in 20hz vs 16hz tune. Let your ears decide.

Tim

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UNICRON-WMD

· #3 · Dec 28, 2005

Well, I port block both my 2 subs to 16hz but you are "playing with fire." You're running a single 12" sub in a OPEN 4500 cu ft room at -6.5db from reference level. I can here your sub bottoming already

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Ron Temple

· #4 · Dec 29, 2005

Well timing is everything. I received mine last night as well, but without as many challenges. My room is 2000^3 with a 5' opening into another 2500 which opens into another 2500. My rig faces away from the opening with the sub corner loaded in the left front. I'll never play mine that close to reference, probably no more than -17. I was going to try the 16hz tune this weekend. Do you think I'll have any problem?

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DavidHir

Discussion Starter · #5 · Dec 29, 2005

Most of the time, I'm probably in the -10 to -15 range. I'll try experimenting...for now, I'm going to leave them out.

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OvalNut

· #6 · Dec 29, 2005

Ron,

You'll have to run it pretty hard to pull off a 16hz tune.

My room is 2520^3 with a 6' wide opening into another 1340^3. I had a 20-39 PC+ initially and ran it +4db hot in 20hz tune at about -15db MV, and could tell I was really stressing the driver during certain extreme hits like the pod race tunnel explosion in TPM.

Once I tried the 16hz tune, I picked up occasional port noise/amp clipping(?) during things like the water bubble explosion in Revolutions, any material with a peak centered around 16-18hz. Based on the above, I went back to 20hz tune with the 20-39 PC+.

If you want to go 16hz, consider moving it nearfield. Once I changed to a PC Ultra, I moved it behind my couch and the 16z tune is the answer for me now. Part of that is the Ultra itself, but the nearfield placement helps.

... my $0.02

Tim

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Ron Temple

· #7 · Dec 29, 2005

Thanks for the advice Tim...as par for the course, I'm pretty jazzed about my new purchase with stock tuning. I'll probably experiment, but I appreciate your comments and will watch closely for signs of distress. Right now, I'm sitting at -6 trim about 1/4 gain on the sub and I'm getting more output than a couple of Cadence subs( which is to be expected).

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