DIY Subwoofer in 5.1 setup - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 10-27-2014, 12:12 PM - Thread Starter
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DIY Subwoofer in 5.1 setup

Hello. Have been looking and learning here for a long time, and am getting very close to the time to pull the trigger on my DIY sub build from the source here.

Naturally, much more to know than I know, or even to ask. Would it be rude or in violation of any rules if I asked some questions I asked elsewhere? I really want to hear what the sources of my build have to say, and what experienced users have to say, so that I can make good decisions.

Here it is:

Really want to get this subwoofer integration as right as possible, but am very aware of all that I do not know!

Here’s the situation:
1. Approximately 6,500 cu ft general area—vaulted ceiling great room, open to adjoining dining area (continuing the high ceiling, sharing the same back wall as the great room and the TV/AVR/main speakers), open to the kitchen through a pass-through.
2. Main listening positions range from about 5’ to 11’ from the front of the intended subwoofer, which will be positioned behind the MLP area.
3. Truth is, despite the greater perfection of multiple subs, that is a non-starter: my budget, aesthetic harmony, and WAF marital harmony and no-fly zone must be accommodated!
4. Importantly, my main purpose is HT enhancement. I have a Pioneer Elite 35 AVR, Klipsch KLF 30s as fronts, Klipsch KLF C-7 center, and Klipsch KLF 20s as surrounds.
5. Ear-splitting volume is not what I am after. What I want is to bring the low end of movie frequencies into the experience, while listening at typical volumes ranging from -35 to -25 (real “action” movies).
Not married to this “solution”, but based on what I have been reading, and upon the cumulative experience and comments (and urgings) of a number of Forum members here, I have migrated toward thinking that a DIY sub may offer the best overall solution. Specifically, the “Stonehenge” (30” x30” x 16”--the 16” depth has a lot of appeal!—tuning at 19Hz, and 5.4 cu ft internal volume) flat pack.

Seems that most subwoofer recommendations in my price range are a Dayton Audio UM-18” sub or an SI HT18. Any second or other thoughts?

Some “concerns” that I have are (comments about above welcome, too):
1. Don’t laugh, but am I likely to do damage to my physical structure (drywall, wall hangings, vases, etc.) if I do not often have very high volume—which some people enjoy and consider normal?
2. Given the distance of the sub location, is my MLP likely to really hear and feel the LFE of such a sub (box) and driver, without “extraordinary” volume?
3. If the port is to the right of the box (looking from the front), how far out from the wall should I put the sub? That distance plus the depth of the sub box is a large reason for the preference of the Stonehenge, at 16” of depth, along with the 19z tuning.
4. Have seen several different recommendations for amplifier. Based on only 1 sub (no chance of a 2nd down the road), and not needing or wanting ear-bleeding volume levels, what would work well? What about noisy fan issue and/or others—for someone not likely to “fix” it himself?
5. With respect to an amplifier and the one sub, what process do I go through to have the sub properly integrated and sounding right? Is one sub or process simpler (successfully) than another?
6. Given that the center channel speaker has a low range of 75Hz, and the KLF-30s are at 36Hz, what would be the proper crossover setting? I presume that I should take advantage of the 2 12” speakers in the 30s for most music? Where best to integrate the sub, relative to the center and mains?
7. Please inform my understanding: if my center channel has a low frequency of 75Hz, I presume that if I had the sub crossover at less than that level, I would have a gap or void in that frequency?

Many thanks for the thoughts and answers that are likely forthcoming. I do appreciate all your contributions to my education, and my listening pleasure!
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post #2 of 5 Old 10-27-2014, 12:34 PM
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I'll take a crack at some of these:
1. No
2. In my experience, 'feel' is based on a combination of how close you are to the sub and how much air its volume. If you go with a Stonehenge tuned to 19hz, you should be able to hear down to 19hz at moderate levels, but you likely won't feel anything if the volume isn't very high and you're not very close to it.
3. I wouldn't go any closer than two times the height of the port. A foot or so would be better.
4. Given your situation, I'd probably recommend a 1000w plate amp. You get much more performance per dollar by going with a pro amp, but then you'd have to probably swap the fan, mess with Spekon connectors, and implement a high-pass some way or another.
5. Depends on your avr and how serious you want to get and how much money you want to spend.
6. I'd still cross all channels at 80hz for movies, and music is up to your preference.
7. Yes
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post #3 of 5 Old 10-27-2014, 12:39 PM
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Ultimax 18 wont work well in Stonehenge . Si18 will.
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post #4 of 5 Old 10-28-2014, 06:58 AM
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On modifying a fan in an isn't too big of a deal. No bigger a deal than connecting wires to your subwoofer in all honesty; it just seems more scary because you are opening the magical cover. I just fear that going with a plate amp might take care your fan noise but I think you will leave so many other things on the table that your might be disappointed by the end result. You have a community here. If you do your part (take good pictures and ask thoughtful questions) then we will do our part (help you along).

I must be guilty because people say I am guilty because they chose to call me guilty because they refuse to see the truth. Much easier to be part of the mob..
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post #5 of 5 Old 10-29-2014, 07:17 AM - Thread Starter
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I thank you for your responses! I will get "there", wherever that is.


AVRs: Yamaha RX-A2030, RX-V575, Denon AVR-X1100W
Speakers: Polk RTi12, Polk RTi6, Polk CSiA6, Polk CS350, Infinity Beta 50, Beta 20, C360, Infinity Primus P362, Klipsch KSF-C5
Subs: Outlaw LFM-1 EX, Klipsch Synergy Sub-10
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