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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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Boomer,

Something you need to ask yourself is how loud will you be listening?  Reference Level is what most folks compare their listening SPL to for movies/films.  In fact, most receivers have their volume knob in gradations in dBs below a 'zero' level, like -20dB. 

'Reference' in cinema size venues means peaks from the LCRS can hit 105dB, and from the LFE channel 115dB.  It is impactful and loud (no 'rewind' button in a cinema, you gotta hear it the first time).  It is hard to find a good enough cinema that can play at reference without significant strain to both equipment and audience.  Most play lower due to patron complaints.  My usual listening level is -15dB to -7dB below reference, my max is usually -3 to -4dB below.  Getting clean bass down to 20Hz and below at -10dB and louder does take some doing.  Getting clean bass at -20dB below reference is MUCH easier.  Getting clean (less than 5% THD, preferably lower) <20Hz bass at full reference level is not an easy undertaking in most cases; no matter what people on forums would lead you to believe.  Due to most home systems using a .1 channel for bass, most, if not ALL, of the lowest frequencies from the LCRS get sent to the sub as well as the LFE signal.  At full reference level, that can mean peaks in the range of 125dB, and as high as 128dB.  That takes some serious horsepower.  Listen at -10dB, and those numbers get more manageable.  At -20dB, and a lot of decent home systems can do it reasonably well, and I really enjoyed films through a -20dB system for a long time, until this one THX trailer distorted my subwoofer over and over again....and then I went down this rabbit-hole you found me in.

How low do the subs need to dig to?  Do you want to feel things shake in your house and fall off of shelves?  Put it this way: Most cinemas do OK to 40Hz.  Some good ones do well down to 30Hz.  I have yet to be in a cinema that can do 20Hz without significant distortion.  To get 'good cinema' sound, you only need 25-30Hz and up.  Films contain content much lower at times.  But if your goal is a 'cinema at home', you don't need support down to 10Hz (it is fun, though).  This is the data-BASS forum, after all...

Do your LCRS provide enough SPL that you are only looking for low end support to help them out?  This goes back to the 'how loud' question above.  At levels above -15dB to -10dB below reference, LCRS will start to sound strained, and listener fatigue can be the end result.  A lot of 'slam' and 'impact' come from good fidelity and SPL in the higher frequencies that the LCRS handle, and they need to combine with the sub system to provide a coherent wavefront to get that 'slam'.  It is hard to get in a small (home-sized) space.

How much space do you have to spare for subs?  No one is exempt from Hoffman's Iron Law, especially on a budget.  One of the systems I miss went down to 16Hz at -10dB below reference, but it required 36 cubic feet worth of subs.  However, it was in a basement, and that made those subs dig deeper than they would have in an open floor plan due to room gain.

What is a reasonable budget for you?

Answers to these questions will make things easier for the members here to make recommendations for you. 

I have been able to get 'budget' systems to sound 'decent' and dig pretty low and loud for the cash outlay, if you are willing to sacrifice some cubic footage and make some sawdust.

JSS

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Thanks, Max.  I think the number of variables involved in the selection of a subwoofer are somewhat overwhelming.  Your suggestion to determine a rational budget seems simple, but I think my problem is much more basic.  I have very little listening experience when it comes to various subwoofers.  The numerical expressions of how low, how loud & how accurate each subwoofer can reproduce bass don't mean much to me because I haven't heard a sufficient variety of subs with differing capabilities to understand the numbers.

But, I'm hoping to take a big step forward soon.  I haven't been able to go to Stereo Integrity yet, but I'm planning to go soon.  I'm excited about hearing a few different subs with someone who actually knows what he's talking about.  I won't be surprised when I decide to buy a SI driver after a visit, but I'll know it was an informed decision, at least. 

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4 hours ago, Boomer1950 said:

Thanks, Max.  I think the number of variables involved in the selection of a subwoofer are somewhat overwhelming.  Your suggestion to determine a rational budget seems simple, but I think my problem is much more basic.  I have very little listening experience when it comes to various subwoofers.  The numerical expressions of how low, how loud & how accurate each subwoofer can reproduce bass don't mean much to me because I haven't heard a sufficient variety of subs with differing capabilities to understand the numbers.

But, I'm hoping to take a big step forward soon.  I haven't been able to go to Stereo Integrity yet, but I'm planning to go soon.  I'm excited about hearing a few different subs with someone who actually knows what he's talking about.  I won't be surprised when I decide to buy a SI driver after a visit, but I'll know it was an informed decision, at least. 

I hear you and understand totally.  Like, you can't just go to YouTube to see a video of what "20 Hz at 105 dB" sounds like.  And part of making the best of the budget is to avoid either over-buying or under-buying for your (as yet unknown) bass desires.  Being able to visit SI in person should help a lot with that.  Good luck!

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I'll throw my 2 cents in. You want stealth. Your wife likes low end but thinks that means louder. You haven't heard many different subs. Your current one is a 100 watt 12" ported.

Have you used your mic with the receiver to get an idea of SPL you're aiming for? If you're not sure of the setup sometimes it's easy to just buy a cheap SPL meter and walk around the room to get an idea of how loud you want it. If you're only playing 85db you don't need much...

Easy end of the scale (that will out play a 100 watt 12" ported) is flat pack from Parts Express with one of the Ultimax drivers. Or the Marty subs. If you want to buy the cheapest already made try an open box Monolith sub from Monoprice. They've got great reviews and specs.

Personally, I'd be tempted to put a tall (vertical) tapped horn behind the T.V. Or a skinny side firing tapped horn behind the plant in the picture labeled "Only solid wall"

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I did throw out tons of numbers....but lemme make it more manageable.

Do you and your spouse like how loud a good cinema is?  You can consider that 'reference'.

You can think of 10dB steps below that as each one being '1/2 as loud'.

When I used to demo my old system, I would tell people that it played at '1/2 the volume' of a good cinema, at 10dB below reference.

On my first ever HT, I rarely ever played louder than '1/4 as loud' as a cinema, or 20dB below reference.

As for frequency, I tell people that 40-50Hz is most 80s-90s hip-hop.  30Hz is around where some EDM music has their lowest bass, and as low as most good cinemas go; e.g. the low end of the sweep during Ironhide's somersault in the 2007 Transformers movie.  20Hz is something that is rarely achieved in a typical commercial setting, IME.  Hopefully this will change with products such as the Meyer VLFC, and it's role in the remix of Apocalypse Now.

From the Meyer Sound website:

"The system for the VR installation utilizes two different Meyer Sound systems. One is the 1100-LFC low-frequency control element, a staple in touring systems for artists as diverse as Celine Dion, Ed Sheeran and Metallica. The other is the new VLFC very low frequency control element, recently in production but with limited availability, that is bolstering the extreme low end on the current Metallica tour. The VLFC powerfully reproduces sound only in the single octave that bridges the threshold of hearing, between 13 Hz and 30 Hz.

“We developed the first versions of the VLFC for NASA to use in vibration testing,” says Meyer. “But we decided to continue development for uses in both cinema and concert applications. We have done extensive double-blind testing here in our own Pearson Theatre. There’s no doubt that people have a different psychological response when we add in or remove that extra octave from 13 to 30 Hz.”"

JSS

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Everybody"s input has been very helpful to me.  To get an additional viewpoint, my long-awaited (not really a "long" wait) visit to Stereo Integrity happened last week. Nick met me in the parking lot & called me over to the back of his Jetta.  He lifted up the hatch & showed me his new 15" SQL-15 he had mounted into a remarkably small box he bought for $20 for on Amazon.  He had a 1000w amp driving the sub.  He also had one of his mid-range woofers & tweeters on each door (he's now discontinued those speakers).  He cranked up the volume & actually played some pipe organ music for me first.

It was impressive.  The vibrations from the extremely deep bass hit me hard in the chest (& everywhere else).  Nick said one note was 16Hz. I believed him.  It was very deep & loud.  My poor wife was in the back seat & during the demo she told me her hair was blowing from the air being moved by the sub.  It's not a big surprise.  The Xmax on this driver is 28.4mm.  That's not 38mm Xmax like his HST-15 mkII, but it's pretty damn good. Air was being moved - a lot of air. 

Anyway... after a long & enjoyable demo ( including every type of music) & me quizzing Nick about every bass topic I could think of, we began to say "Good-bye" - but even that took a few minutes.  He's just a really nice guy.  In addition, he was incredibly patient & knowledgable.  Of course, I left knowing I would buy one of those babies.  They won't be ready to ship until late December, but I'm in no hurry. 

Now I need more specific advice.  I've decided to build a ported sub with ST's 15" SQL-15 driver.  Nick recommended 1000w for the amplifier & I'm considering a Crown XLS 1002 with 1100w @ 4 ohms bridged.  From SI's website: Ported = 3.75 ft^3 tuned to 29 Hz.

I have a Mac & no easy access to a PC, so my access to speaker design software is limited.  I found a limited web-based subwoofer design program, but I'd appreciate any feedback on the sketch I'm u ploading.  I like the idea of a "pipe" port, but I have an open mind.  How many braces should I add inside?  All suggestions are welcome.

Subwoofer Box for 15 inch subwoofer | Ported Box | Pipe.jpg

SQL-15 15″ – Stereo Integrity.jpg

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Glad your wife didn't veto your purchase after what she had to "suffer" through, lol.

Keep in mind that a subwoofer in a car get a lot louder than it does in a house where there's a lot more space to fill.

If building a vented sub, the tuning frequency is very important because the sub won't play much content below the tuning frequency.  So at 29 Hz, you'll be missing out on most of the content below.  If you want to *just* get to 20 Hz, maybe aim for a tune of like 22 Hz.  Also, I think a 4" diameter port is a bit small.  You need enough area to avoid chuffing and compression at high output.  How much you need depends on what the overall design looks like, but for a 15" woofer like that, I think you'll want at least 2 x 4" pipes.

Do you want to tune lower?  The trade-off is that you need to make the vent longer or the box larger, keeping the vent area the same.  Working from the numbers you posted, a pair of 4" x 20" pipes ought to get you a tune around 22.5 Hz.  Actually, it'll be lower for that particular cabinet if the pipe exit is near the wall because the wall effectively extends it.  Alternatively, you can make the cabinet larger, and this will also help boost the output around the tuning frequency.  You may want to look at simulations though to see what you're ultimately likely to end up with.

If you do decide to use one or more 4" pipes, this product is real hard to beat if it works for your cabinet design.  The flares help a lot with improving performance at high output.  They are also very easy to install.  If you decide to use them, I recommend using the formula included in the manual to calculate the length because it takes into account the flares properly.  And also keep in mind again that if the exit is near the wall, it'll tune lower than expected.  (Don't let them exit less than ~3-4" from the back to you don't constrict the flow there too much.)

I think the XLS 1002 amp is a good choice as it includes DSP which you need for a vented design to apply a high pass filter to protect the woofer from frequencies it can't play.

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That ported design on Nick’s site is for car enthusiasts that want to get the most bass response from their sub.  I agree that 29 Hz tuning is too high.  There are generally two camps of home theater subwoofers enthusiasts, those that are content with 20+ Hz bass content and those that want the ability to reproduce bass below 20 Hz.  With my 24” subs, obviously I’m in the under 20 Hz camp and feel there is a lot of content there.  But even if you’re in the 20Hz camp, a 29 Hz tune is way too high for home theater in my opinion. You’ll be missing many explosions as there is a lot of movie content under 30 Hz. IMO, you’d be better off buying a few more subs and going with sealed.  Extra amp channels is fairly cheap and those subs aren’t too expensive.  Plus you‘ll gain the benefit of more even bass from more subs in the room.  Use the Multiple Subwoofer Optimizer to align them and you’ll have deep, even bass throughout the room.  You could always start with 2 subs and add more later if you want more output and more even bass throughout the room.  That’s what I’d do and what I’d recommend.

https://www.andyc.diy-audio-engineering.org/mso/html/index.html

 

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Thanks for the advice.  Dgage, I would have never been satisfied with the tuning used in my first attempt.  I went back to the modeling software I found & set the port tuning to 16Hz & it generated new plans.  I'll upload them.  I wish I could afford to build 2 subs right now, but it's not feasible.  I need to build one sub & try to maximize its performance.  

SME suggested using 2 ports - that's probably a good idea.  The revised plans I'm uploading indicate one 3" x 16.87" port.  If the port length is correct, will 2 ports 3" x 8.44" produce the same result?  I am very aware that the port length may not have been calculated well, so any confirmation will be appreciated.

SQL-15 Ported Sub.pdf

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Hi guys - I did a bunch reading since my last post.  Shoulda done it before I posted that last message.  I'm more educated about the relationship of the size of the box, diameter of port, number of ports, and the tuning of the sub.  I knew so little when I started researching DIY subs that I'm constantly amazed at what I still don't know.  I guess it's a good thing that I don't mind laying out my ignorance in front of all you more knowledgable people.

I'm back at the "drawing board" to decide how low I'd like to tune my sub, how large of a box will be acceptable in my room, how many ports am I planning & the diameter of the ports. So, until I can get my head around the various parameters left for me to determine, I'll be working on these variables.

It's like I've been thinking from the beginning - answering a few questions (how big of a driver, which driver, how much power, ported or sealed) just opens the door to additional questions.  I'm glad I enjoy solving puzzles.

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After working with some box modeling software I've come up with a new design.  To the basics: I'm planing to use a 15" SI SQL-15 driver (with dual 2 ohm voice coils) & a Crown XLS1002 amp, 1100w bridged @4 ohms.  My plan now is to build a 7 cu.ft. box (26'" x 20" x  29.35") with two front-firing 4" ports tuned to 16Hz.  The ports will be 36" long - necessitating a curve in the PVC ports.  I have a friend in the cabinet business & he will cut all of the MDF for me.  I plan to assemble the box & ports myself. I've decided to put this sub between my L&R speakers & under the center channel.  This will allow me to hide most of the box from view, but this location has restricted me to 20" high & 26" wide.  The depth is variable.

Because I only have access to a MacBook I've been unable to do any modeling using the driver I've selected.  I don't know if tuning the box to 16Hz is reasonable for this driver, amp or box size.  I'm not ready to start cutting MDF, so I'd like to know where I may have gone astray and/or made unreasonable assumptions.

https://subbox.pro/en/b/wikqDKNb2 - the mock up of my current design. This program doesn't give the option to move the ports to the front or to indicate a curve in the port.  Based on my research the length of the ports should be 36" - not the 33.83" indicated in the box design program.

All feedback is appreciated - even if it (once again) exposes my ignorance. I have so much yet to learn.

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A better option than a simple 90 degree short radius elbow fitting would be a sweep elbow. Here is a table on the frictional losses of different pipe diameters and the types of fittings. http://media.wattswater.com/orion-hp-frictionloss.pdf

4" long radius sweep elbows are utilized in electrical service installations, you may be able to source something locally.

If you are on Mac or Linux, you could use Wine to install WinISD, if you desire. Regarding port length, this depends on how close in proximity the port inlet and outlet are to boundaries, this can change the actual installed length for the desired tuning, and if an inner flange or torus is used on the end of the pipe.

 

 

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Thanks, Ukko.  I noticed the sweep elbow you mentioned when I was looking for components for the ports.  It looked preferable to the 90º angle piece.  I will be able to source the pipes & fittings locally.

I haven't tried Wine to run WinISD.  I'll give it a try.

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