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Boomer1950

69 yr-old guy needs advice with 1st DIY sub

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I'm recently retired & I'm spending even more time listening to my home theater system with my wife.  We use my system for movies & TV 60% of the time & music 40%.  I bought most of my current speakers 13 years ago.  I have Polk Monitor 70s up front - Monitor 50s as surrounds - I recently upgraded my center channel to a Polk CSiA6 (from a CSiA3) - I added 2 height speakers - Polk RTiA1s - last summer.  The only subwoofer I've ever owned is the Polk PSW12 - a "powerhouse" 12" ported sub with 100W.

My house was struck by lightening last summer & blew up all of my electronics.  I had a surge protector, but it had gotten too old to save my system.  The good news is I was able to replace my TV with a 65" TCL 4K TV - replaced my AVR with a Sony STR-DN1080 - a Sony UBP-X700 4K Blu-Ray player replaced my Blu-Ray player - and an Apple TV 4K replaced my old Apple TV.  I moved into the 4K/DolbyVision/HDR/DolbyAtmos world suddenly.  The new receiver improved the sound of my main speakers dramatically (this is my 3rd AVR in 13 years).  Unfortunately, it has also exposed my subwoofer as being woefully under-performing.

I have a tough room to work with in some ways.  It's 16' x 17 with a ceiling that starts at 9' on one side of the room & reaches 14' on the other side.  One wall has a double doorway leading to a small home office - another wall has a double doorway leading to the kitchen/dining-room & it also includes a pass-through window that's 60" x 32" - another wall has a stairway leading to upstairs & a hallway to 2 bedrooms.  One wall is solid, but it has a large window on it.  So... I'm forced to use a corner placement for my TV & my couch is diagonal in the room - parallel with the TV.  I'll add some pics to this before I post it.  Given the awkwardness of my room, my speakers are positioned fairly symmetrically for my listening position.  Everything looks & sounds better than it ever has, except for...

We are both retired, so an unlimited budget isn't in the cards.  My wife enjoys movies & music on my system, but she doesn't appreciate what we're NOT hearing on the low end.  She hears "better subwoofer" only as "even louder music & explosions".  I have a slight uphill battle for this project, so keeping it as "stealth" as possible is important - I'm thinking down-firing or dual-opposed end-table or coffee table.  I probably need to keep total driver cost around $400-$500, but I'm open to suggestion.  I believe DIY is my best option & I'd love a flat pack.  But I have a friend who makes cabinets for a living, so a custom design is doable.  However, I'm lost as to whether I'd be better served by two 12" or 15" drivers as opposed to one 18" driver.  Or, I'm torn between ported & sealed, of course.  I lean toward sealed, but I appreciate what a well-designed ported sub can do.  I don't feel compelled to  get below 20Hz.  Getting down to 20Hz would be wonderful.

I'm further handicapped by the fact that I only own a MacBook Pro, so most of the common subwoofer design programs are apparently unavailable to me.

I need you to put your best thinking caps on.  My problems are slightly different than the ones Ricci faces ("As usual with me it's not about the most I can get out of a single driver or for the least amount of cash but what can I get out of X amount of cubic volume for application X using whatever means necessary. Can't help it it's just what I find interesting anymore.").  I need to spend as little as possible, but receive the most performance possible.  Everything's easier when that pesky "cost" constraint is removed.

corner stuff.jpg

wall #1.jpg

wall #2.jpg

3rd wall.jpg

solid wall.jpg

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DIY is definitely the way to go if you want the most for your money.

You said that you'd love strong reproduction down to 20Hz, so a vented design tuned to 20Hz or a little lower would be your best bet. There are a few smaller designs on AVS, like the smaller ones from the Marty line which is pretty popular. They also seem to be very budget friendly and are not hard to build, plus I think you can also get flat packs. Add an NX3000D and you're golden.
As for your thoughts about 18" vs 2x12".. 2x12" will probably about equal the 18" in SPL, be more expensive but allow you to be more flexible with placement, so you can get a better room coverage. That being said, your room is actually pretty good for bass. The ceiling not being parallel to the floor for some parts of the room reduces room modes.

In any way, if you're fine with manual labour, I highly recommend getting into some woodworking. It's a lovely hobby 😊

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Thanks for the advice, Peniku8.  I have been sorely tempted by the Marty Sub Cube.  It really convinced me to go DIY - the cost/benefit was clear.  I thought the logistics of getting one of their flatpacks is somewhat complicated.  They like to ship 4 Marty subs to a customer & he tries to find someone to buy a couple in order to share the freight costs. Call me hornery, but I don't like that process.  I was impressed with the build of a MartySub & the kit is great with the interlocking structure.  It's not out of consideration.

 

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5 hours ago, peniku8 said:

As for your thoughts about 18" vs 2x12".. 2x12" will probably about equal the 18" in SPL, be more expensive but allow you to be more flexible with placement, so you can get a better room coverage. 😊

It’s actually 2 12” (amplifying both subs) almost equal a 15” and 2 15” almost equal a powerful 18”.  2 18” almost equal a 24” sub.  Generalization but fairly accurate. 

And I always recommend at least two smaller subs than 1 larger sub though I wouldn’t go less than 15” in size.  The reason for multiple subs is to even out the bass in the room, dismissing improvement above 4.  If you play a single sub in a room, walk around it and you’ll hear boomy bass in some areas such as the corners and in other areas the bass will be weaker.  So for best bass consider 2 of whatever subs you can fit.

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Thanks, dgage.  That question of two smaller subs vs. one larger sub has been a difficult issue for me. I thought two smaller ones were preferred, but it's nice to have that confirmed. 

For some reason the idea of dual opposed 15" drivers in a "coffee table" appeals to me. The table would sit parallel to my seating position with the drivers firing to the left & right.  Neither driver would have any obstructions near it.  The idea of having a relatively vibration-free coffee table/subwoofer has grabbed my attention.

Will this configuration provide any of the benefits of having two separate 15" subwoofers?

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18 hours ago, Boomer1950 said:

Thanks, dgage.  That question of two smaller subs vs. one larger sub has been a difficult issue for me. I thought two smaller ones were preferred, but it's nice to have that confirmed. 

For some reason the idea of dual opposed 15" drivers in a "coffee table" appeals to me. The table would sit parallel to my seating position with the drivers firing to the left & right.  Neither driver would have any obstructions near it.  The idea of having a relatively vibration-free coffee table/subwoofer has grabbed my attention.

Will this configuration provide any of the benefits of having two separate 15" subwoofers? 

A D.O. 15" cabinet would not likely gain the benefit of having multiple subs in different parts of the room because they are too close together.

There are pros and cons to using a coffee table sub.  Usually the best place for a sub is as close as possible to the longest and most rigid walls.  However, this location also tends to accentuate room resonances the most, which is an issue that EQ (or "room correction") might be able to help with.  Placing it away from a corner, as would be done for a coffee table sub, will excite fewer resonances.  However, you'll likely get a lot less low-end output/efficiency and potentially a major dip in response somewhere, depending on the distance of the "table" to your major wall.

What other potential placement options do you have?  The corner with your gear is likely to be the best location for output/efficiency.  Because your room is so large and you don't have a big budget for subs and amps, I agree with the recommendation for a vented design.

As far as woofer size is concerned, it's not that important by itself.  What's important is how the particular driver fits into the overall design (including satisfying space constraints).  Different drivers have different excursion capabilities, which affects overall output potential in addition to diameter.  For the same "style" of driver, you typically get more bang-for-the-buck by going bigger, to a point.  For home theater style subs, 18" seems to be the sweet spot for value.  I am personally partial to pro-style drivers, which have less excursion than typical HT subs but which are easier to find in 21", which I'd say is their value sweet spot.

I realize you probably weren't even considering 18" or 21".  If only you knew whether or not you would be satisfied with two subs using 15" or smaller, you would have no reason to consider something bigger.  However there is a very well-known tendency for DIYers, upon completing their first subs, to immediately decide they want *more* subs.  Most consumer subs don't have the output to play movies even at medium volume without struggling.  They may sound loud in the process but not good.  When you have clean bass, you may be inclined to turn the volume up (or turn up just the sub) more than you used to.

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On 9/7/2019 at 9:47 AM, Boomer1950 said:

Dgage, one other thing... Do you have a 15" driver you prefer. I realize you don't use 15" drivers much anymore. Is the Ultimax 15" a good choice?

I use Stereo Integrity subs for my commercial subs so I’m partial to those and know they perform well.  The HST-18 is a really powerful driver that is one of the most powerful you can get.  SI also makes smaller diameter subs using the same magnet-motor in the HST-11, 12, 15, etc thought they may be more expensive than many other drivers.  But I heard the HST-11 and a pair of those were impressive in very small enclosures so while the value may not be there, you have a lot more flexibility with placement.  

 

‘And I’m not a big fan of dual-opposed simply because their advantage, vibration canceling, isn’t that big a difference with a well-built large single sub.  And the disadvantage of placement options is what I really dislike as their best placement is midwall running parallel to the wall and not many have that position available.  

 

‘’And if you’re thinking a coffee table, I’d personally go for a well-built down-firing coffee table.  Or a pair of end tables or similar, which you can spread out a little better.  

 

Also think about size vs location in respect to your main listening position.  Maybe place a larger sub near the front of the room and a smaller driver near your primary seat.  The SI HST series could help with this as the sonic signature is the same while the output is slightly different, stronger up front with a larger driver, and less output near your seat since you don’t need the closer sub to play as loud to keep up with the front.  

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And I just talked to Nick of Stereo Integrity and he’ll be coming out with a more sensitive and less expensive set of 12 and 15” subs near the end of the year, which might be worth checking out.  They’ll also dig pretty deep in a fairly small enclosure, 2 cuft for 15”.  However I wouldn’t consider those if you’re wanting to move forward in the next month or two.

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You guys are so helpful. I was afraid my problem wouldn't get any attention, since I wasn't planning to build four 21" subs 😉

In my recent travels around the subwoofer universe I had discovered Stereo Integrity.  Everything about their drivers looked great - if expensive - to me. They became my "aspirational" choice.

The truly amazing thing is I live less than 2 hours away from SI. I'm a NC guy - born & bred. Do you know whether visitors are welcome at their facility?  I don't plan to be a pest, but the opportunity to see one of the best driver manufacturers in person is very compelling.  I'm in no hurry to buy a driver.  I'm enjoying the research. But, I would dearly love to be able to end up with a sub from SI.  It's more than worth it to me to wait until they release their new subs later this year. Thanks again, dgage  

 

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You may not be able to hear the SQL-15 in a theater room but you can hear it in Nick’s car.  Reach out to him, his email (sales@) is on his website and ask him if you can come hear it, he is a very gracious host though his email habits aren’t the best.  If you don’t get an email response within a few days, PM me and I’ll ping him.  He also has the HST-11s in his home theater in a dual-opposed square tube but that tube is probably too heavy to move just due to the 70lb magnet motors on the HST series.

 

And yes, I wasn’t sure I wanted to respond to someone who might ONLY want 12” subs.  Lol!  Glad you’re here and glad we provided some useful info.  Great and incredibly knowledgeable people on this forum.

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