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Discussion Starter #1 (Edited)
Hey All -

I am looking for some help in selecting and designing my subwoofer build. Hoping someone knowledgable here can give me a hand.

Our basement has a wall of built-ins so traditional systems are a no-go for me. Instead I'm going to be doing some heavy modifications to the existing cabinetry to incorporate 3 B&W CT7.3's and 2 built in custom subs. The room is around 750 sqft with 10ft ceilings.

As you can see in the picture below, the subs will go in the lower cabinet areas. These will essentially be cut out to the floor so the sub enclosures will be totally decoupled from the cabinetry. Options here include putting the subs on either the left or right area. I'm thinking albeit minor, the outside is closer to corners to get some corner loading so that functionally better. I'd like to create a 'speaker grill' that is essentially the existing door with the center replaced with wire mesh covered by speaker grill cloth.

The space I have for the subwoofer is about 16w x 28h x 23d. I would prefer to use that entire area to avoid creating a pseudo band pass with artifacts from the second enclosure...so I could build a small box, but the driver recess panel would need to be 16w x 28h. To give room for binding posts and driver excursion it'll take a few inches off the total available depth. I think we're looking somewhere around 4cuft available volume after bracing and driver.

I haven't purchased drivers or amps yet, so I'm curious what ya'all think. I was considering going with 2 Creative Sound SDX12's and inuke 6000dsp, but think started thinking that I *could* get 15's in that space too. Would something like an ultimax 15 perform better? Any other options? (That sweet car audio pioneer driver is for a visual only )

Given the amount of demo I need to do here, I'd like to get this right the first time, so any help would, thoughts, opinions be greatly appreciated.


Nik


9/2/16: Added the 'before' picture to OP
 

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Since your location is fixed, as is size, I guess the next thing to look at is displacement. You'll want to push as much air as you can using what you've got. Doing a quick (and rough) calculation, it looks like the Ultimax 15 has slightly more displacement due to the much larger Sd, but if you can fit a pair of SDX-12's, they'd move almost twice as much air as a single UM-15. They aren't cheap, but that's because they ARE a pretty formidable driver.

StereoIntegrity also have even higher excursion 11" and 12" drivers, the HST-11 and HST-12. I think the 11 offers similar displacement to the SDX, and the 12 actually beats out the single UM-15 for displacement. Definitely worth looking into!
 

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Discussion Starter #3
Thanks for the thoughts. That makes since -- I have a few less variables to work with given the built-in nature of my project.

I have a pair of SDX12's here so my first choice would be to use those, but I'm open to the Ultimax 15's. The SI drivers are nice, but out of budget for me :( 18's won't fit so that leaves out the SI 18DS4 which is closer to my budget(<$250 a driver)

I struggle to understand what is 'enough' when it comes to subs. I know that's subjective to a degree, but given the room size I'm in, with a typical seat position spl of around 65-70dbc, would two sealed ultimax provide significantly better performance than two SDX12's?

I'm trying to do some research on that to understand what objective measures there are. I'm most concerned with 20hz and up...don't think below 20hz is that important to me. I like tighter, more tactile bass that's well integrated...in the past I've usually found myself trimming down bass for nice integration versus running it hot for more pronounced effect.
 

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If you already own the pair of SDX-12 drivers, then that's what I would go with, personally. Sure you could squeeze more out of a pair of 15s (can you actually fit a pair of 15's in there?), but that may only matter at high listening levels. I would build with what's available, and see how I like it. You may decide you want more eventually, but at that point you'll likely be better served by adding a 2nd sub in a different location to smooth out the in room response, especially if your cabinet isn't in a great spot to produce bass.

"Enough" is pretty subjective, as you've noted. People are different, rooms are different, and setup is different. If there's any basic way to provide some kind of idea what level of performance you should shoot for, it is probably "sub displacement per room volume". I can't give you a number, but some of the more experienced guys can probably ballpark something for you.

It sounds like you're not trying to rattle the bones of everyone in your theatre, so I think the pair of 12s should provide nice output for you. Especially if you can take advantage of the DSP in the iNuke to tweak your final response. You'll probably be able to make the sub dig deeper and play flatter than most commercial options in that price range, and you will still have a more capable system than most average people out there.

On a side note... are you cutting up the B&W speakers to build your own enclosure to fit into the built-ins? What about selling them and just starting out with a DIY speaker project. I bet you can get better sound for less money... it looks like the CT7.3's had an MSRP of $1,500 back when they came out(!?) so if you can even recoup half of that cost you could pick up some amazing sounding kits and still come out ahead. Check out some of the SEOS speakers from DIYSoundGroup.com for an idea.
 

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Discussion Starter #5
I'm leaning toward using the SDX12's. One driver on each side (the picture of the built in is mirror image on the other side). I wonder if I could build the enclosure to fit 2 drivers on each side (4 total) but only use one driver now. As budget allows, I could pick up another two in the future to increase output, or leave as it is. Could do something temporary in the box to reduce volume to keep Qtc around .5?

I just want to make sure I'm not making a major mistake or forgone opportunity by not going with another driver option. I'm thinking it might be diminishing returns for my requirements unless we talk ported. The SDX12 from my research and attempted modeling in winisd would require port lengths that are too long. PR's can't be used due to the built in nature. Only a different driver would open up porting opportunities I think.

On the CT7.3's....I just got a great deal on those so that, along with the sub integration, is what's driving me to modify our trimwork. So, no -- definitely not cutting those apart! Just modifying the top built in section there in the L/R sides to flush fit the CT7.3's. The CT7.3's are a great fit, physically, for my constrained location options.

Setups like mine are a mess of compromises, but I have to work with what I've got. I would have liked to DIY using the DSG kits, but I just really don't have the time now.
 

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OK, so there is another cabinet on the other side? That should help spread out the sound. I'd say go with a sealed enclosure for each one that's large enough to add a 2nd if you really feel you need it down the road.

I haven't modeled the SDX in any varying sizes, but I think it should still do fine in the larger space, especially with the ability to use EQ.

Sent from my LG-H812 using Tapatalk
 

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Discussion Starter #7
OK, so there is another cabinet on the other side? That should help spread out the sound. I'd say go with a sealed enclosure for each one that's large enough to add a 2nd if you really feel you need it down the road.

I haven't modeled the SDX in any varying sizes, but I think it should still do fine in the larger space, especially with the ability to use EQ.

Sent from my LG-H812 using Tapatalk

I think that sounds like a good plan!
 

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Discussion Starter #13
Owen, Vin -

Thank you all for your help and thoughts. This trim cabinetry stuff is sooo time consuming for an DIY level craftsman like myself. I'm going to build some vented boxes later this year to play around with options, but for now to keep my sanity in check I just went with some sealed enclosures. I've been working on this every night after work for over 3 weeks now and I still have a ways to go!
 

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Discussion Starter #16
Updated Pics...

80% trim work done. Still have final speaker grill frame w/ routered edges to match the rest to make that will go over the L/R speakers. Need to decide on grill cloth or material for subwoofer faux doors. Lot's of little finish work things to do including lots of magnets (lower baseboard trim will be removable, magnets added to subwoofer doors to keep things from vibrating). You'll also notice the trim piece I built to cover the project hole in the ceiling.

What you don't see. I had to reroute all my cabling to the side closet and pull a bunch of new speaker wire (belden 10awg) since the old wire was too short for the new location. Ran new power to the equipment room.

Final equipment list:

Project: Mitsubishi HC5
Screen: 102" Stewart Firehawk G3
Pre: Marantz AV7200MKii (USPS lost the first one in transit, so ordered a new one today)
Mains Amp: 7x B&O Icepower 500asp
Sub Amp: Ashly PE-3000 w/ DSP
Front LCR: B&W CT7.3
Rear and Side: In ceiling Energy Veritas
Subwoofer: 2x CSS SDX12's in 2.0cuft sealed
Seating: HTMarket Southampton Top Grain

Excited for the outcome, but still a lot of work to do!
 

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I just finished a sealed 18in project using the Stereo Integrity HST18MKII . Its BEAST but just wanted to add a vote for SI as they are designed to work in smaller sealed enclosures... IMO I would go with 2 of the HST12MKII 12's ....They do play REALLY LOW !!
 

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Discussion Starter #19
Good progress since I last checked in! The front left and right look great. The centre isn't TOO far below the others and should sound just fine. Nice clean work so far, can't wait to hear how the subs turn out.

Sent from my LG-H812 using Tapatalk
Thanks, yeah the center channel positioning is not ideal, but with the close distance of seating to the projector screen, the inclusion of a TV also, and desire to get the speaker integrated into the cabinetry it was the best I could do and crossing my fingers on the final outcome. Dispersion graphs for the ct7.3's make me think I have a better than normal chance of this still sounds good. I did a little geometry to ensure the angle of the center channel directly hits ear level at the seating position.

One option i have would be to turn the L/R upside down to get the tweeter closer to the bottom? Might play with that one day...


Nik
 

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I can't see if the center channel speaker can be angled up a bit to the listener. It does not have to be square to the cabinet. A laser pointer with a square can help you get the angle.
 
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