Another "DIY Subwoofer selection help" thread - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 6 Old 07-26-2017, 05:37 PM - Thread Starter
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Another "DIY Subwoofer selection help" thread

Hey guys,

I'm hoping to get some of the generous experts in here to lend a guy some advice. In the interest of being thorough, some background:

So first, the room: My home theater setup is in a common living room that measures 15' x 17' x 8'. The bad is that it has a 5' x 7'7" opening along one wall that opens into a 10' x 10' x 8' foyer / stairway combo. The ugly is that along the perpendicular wall to the first, there is a 6' x 7'7" opening that leads to a 12' x 10' x 8' "dining" room.

Second, my existing subs: 1 Dayton UM-1522 in a ~3.25 ft^3 net enclosure with 3lbs of acousta-stuff powered by a bridged Crown XLS-1002. The sub is EQ'd via my Anthem MRX-720's ARC software, has a 2nd order HPF @ 19Hz, and a 6th order LPF @ 110Hz. A 20Hz tone at -25 on the 720 will actively vibrate just about every wall in the house to at least some degree. To help smooth room response, I have a second BIC America F-12 that I'm looking to replace. Both music and movies are improved by the addition of the second sub, which is easily A/B'd on the same music at the same volume, with and without the second sub.

Sooo....I'm looking to build a replacement for the F12 and am looking for suggestions on drivers. I would prefer to build a ported enclosure, as I do not have the space requirements for horns. I also have the WAF to consider. My wife thoroughly enjoys the setup, and is very lenient and understanding in this area, but she's not going to tolerate another massive enclosure. She's also not going to be amenable to more than 2 subs in our current living room, so I can't expand to 3 or 4 sub enclosures.

My current contender is the Dayton Audio RSS390HO. For $179 shipped, it's a 15" driver, 800w RMS power handling, 21.5Hz Fs that can be put into a 2.72 (net) ft^3 enclosure, tuned to 23Hz with a 2" x 10" x 34" slot port. With port displacement, gasket displacement and bracing, that gives me a total ft^3 requirement of about 3.4 ft^3.

So, I'm interested in other drivers that might work better in a similarly sized enclosure and maybe have a better response / output curve. As modeled in WinISD (provided I did everything right), it looks like output is about 103dB SPL @ 20Hz with 800 watts. I had to add an HPF of 23Hz to prevent exceeding xmax, and port velocity is at just about 17m/s with a first port resonance of 199Hz.

I beseech the audio gods of AVS to grant me wisdom in this endeavor.

Last edited by protectedvoid; 07-26-2017 at 05:40 PM. Reason: (edited to add port displacement)
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post #2 of 6 Old 07-26-2017, 07:42 PM
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Depends on what your goals are.

You could substantially increase your mid-bass performance by adding a PA-460 ported to 40-50hz.
You'd gain about 14db above tuning over what you have now. 15" 86db/w vs 18" 98db/w. It only needs about 300w.

Typically 2 or 4 PA-460's will hit THX @ 10ft away. The the UM-15's you'd need about 8 of them to hit the same SPL.

Alternatively, if you just want more of the same, I'd get another UM-15 and put it in the same sized box.
You'll gain 6db at all frequencies in that case, but the power requirements double.

Or if you want to spend some money, maybe a B&C 18

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post #3 of 6 Old 07-26-2017, 08:30 PM - Thread Starter
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@BassThatHz , the idea of the bump in the midbass by using the PA460 is intriguing, but if my eyes are seeing correct, that looks like a 10 ft^3 enclosure, which is larger than the space I have available. I planned on getting another DriveCore XLS1002 and running it bridged to power this second sub, so safely ~800watts continuous power.

So, as you've modeled it, what happens to the Dayton HO cone excursion and port velocities when tuned at 19Hz w/ 800 watts?

I looked at the B&C drivers. Ideally, I think I'd like to keep the cost of the driver to $450 or less. At that price point, plus the cost of a second XLS1002, I'd be at ~$750 for amp/sub. Much higher than that, and I start approaching the price point of some of the commercial offerings I'm trying to beat.

To answer your question about the goal: My thinking was (and forgive my naivety here) that since I already have a sealed sub that does well in low end extension, that going with a ported sub might bump some of the > 30Hz range with more energy and provide more impact and energy to the room(s). I'd also like it to be fairly accurate, musically speaking, as we do tend to be about 70 / 30 movies to music.
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post #4 of 6 Old 07-26-2017, 09:11 PM
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Have you looked at a HT-18? I've no idea how it'd perform in a box that small.
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post #5 of 6 Old 07-27-2017, 05:36 AM - Thread Starter
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Quote:
Originally Posted by Roctopuss View Post
Have you looked at a HT-18? I've no idea how it'd perform in a box that small.
I had considered it, but wasn't sure if I could fit an 18" in that space. I'd need some help modeling that one as I'm still learning WinISD. From their specs, they indicate a ported enclosure would require 10ft^3 tuned to 25Hz, so that's larger than the space I have. Shrinking the enclosure and changing the port tune are obviously on the table, but then I'd have to balance that against an acceptable port velocity while also minimizing cone excursion. Certainly don't want to blow anything up.

But, I guess that opens up the possibility of moving to an 18" sub. Though, it's highly likely if I went with the HT-18 v2, I'd have to go sealed. That's a 4ft^3 box net...so only slightly larger than the enclosure my UM15 is in.
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post #6 of 6 Old 07-28-2017, 01:20 PM - Thread Starter
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Another question: Does distance from the side wall of the enclosure to the gasket matter much? For instance, if a sub has a cutout diameter of 14" and the sidewall on either side is 3/4" away, is that enough clearance on the sides? (a 14" cutout going into a 15.5" internal width).
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