# Raising subwoofer height



## KevinG (Oct 9, 2010)

So, they say a subwoofer would benefit from being 25% along any room boundary, including height. What I'm trying to figure out is where I should be measuring from for my SVS-PC13-ULTRA. It's a tall cylinder...so is the "sub" at the bottom where the woofer is? Or is it at the top where the ports are?

Any thoughts?

Thanks!

(BTW, the reason this is in the REW forum is because that's what got me to this point! I'm trying to dial in my theater with REW and my new U-Mik1. Hope this isn't considered an inappropriate question for this forum)


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## jtalden (Mar 12, 2009)

My overall thought is that the answer is not too important in the overall task. 

A favorable SW location is also dependent on the LP location and other room characteristics. While it may be a very good candidate, I don't think "1/4 the distance" is a reliable prescription for a favorable result. 

Using REW it is better to just measure the results at the optional locations. We are basically trying to find a location with relatively smooth SPL so that EQ can be effectively applied to fine tune the result. An optimal location is not necessary.

We can model the response of a cuboid room in REW to see the impact of the SW and LP location changes on the SPL and possibly that is what you intend. To answer your question, I would expect standing wave predictions of the port frequencies to be best modeled at the port exit location and the higher SW frequencies to be best modeled at the driver location. [As a hobbiest my expectations are not as reliable as a professional/expert one would be however.]


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## KevinG (Oct 9, 2010)

It was mostly just a curiosity. I had read that and wondered which "end" of my cylindrical sub "mattered."

Unfortunately, my room isn't cuboid. It has openings at the front and rear right sides to other rooms, and the ceiling has two soffits, and there is a closet (for equipment) in the left rear. Maybe it would help to ignore those oddities, and plug the numbers into REW, but I'm guessing that the oddities matter, and the results wouldn't be that meaningful.

For now, I've got two obvious places for the sub, the front left corner yields a large (well, thin, but deep) null at the listening position right around 35hz. Yuck. Another position on the left wall yields a large (similar) null somewhat higher up in the 57ish region. I'm going to start playing with other positions along the front wall (which will be behind the motorized screen when it is in the down position.)

If you *have* to have a null, is there a preferable frequency at which it should fall, or, stated another way, are there particular frequencies which are important enough to the enjoyment of music/movies that we should make sure don't fall into a null?

Thanks!


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## jtalden (Mar 12, 2009)

To your question: If those were the only choices I would rather have the null at 35 Hz as there is less music content the lower we go. I suspect there may be differing opinions on this however.

Also:
The REW simulator currently has no way to properly mix the combined response of 2 different heights into the combined modal response of the room at the LP. We can't just look at the separate runs and draw any conclusions. I have no idea if the relatively small height difference would be significant or not. I didn't point that out above and should have.


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## KevinG (Oct 9, 2010)

As it turns out, I'm not sure any of it matters (well, to me anyway, it probably matters a lot to others.  )

By changing my x-over from 120 to 80, and changing my sub's phase to 180 degrees, I was able to *significantly* flatten my response... Then I let REW do its magic to update my FBD, and I'm a really happy camper (in the bass range, anyway). This weekend I'll try playing with the windows EQ to try to flatten the rest of my spectrum.

Thanks for the assistance!


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## RossoDiamante (Aug 12, 2013)

REW sounds like a great tool to start making some of the decisions required to make a room sound good. I'm looking forward to my own measurements and tweaking going forward. 

A question that I would pose to the general audience, however, is whether objective changes shown on these graphs reliably translate into "better" sounding. I wonder whether "better" in the context of home theater acoustics will end up being like color preference for walls and carpet. There really isn't a right and wrong answer, only what you like and don't like.


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