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Discussion Starter #1
hey all,

Im looking at building my frist DIY Sub, a sonosub to complement my pc13ultra to even out the bass response in my room. While I was at it I was thinking of doing something bigger.

my initial plan was to go:
h 47 x w 20
dual 3.5 inch ports with a 1 inch flared exit 22 inches in length
18 inch driver

but Im wondering if something like that would completely out class my svs sub to the point that i end up not solving the issues I was looking to solve with dual subs.

I could do something similar with a smaller diameter
h 47 x w 17
Single 4 inch ports with a 1 inch flared exit 22 inches in length
12 inch driver


Thoughts?
I was really hoping for some good driver recommendations from folks with more experience than myself.
 

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Just depends on budget. You can design a great 12" ported enclosure but you need to define what are SPL needs are. An 18" can be great but probably not going to do very well with small port sizes like you have mentioned. Need to simulate the cabinet and look at port speeds to keep the port from singing.

There are LOTS of 18's out there so I will wait to hear back from you and then make a suggestion.
 

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Discussion Starter #3 (Edited)
hmm, I did model it out in the sonosub application Both configs had a target of 16hz and there were no warnings. Dual 3.5" ports have about 35% more volume than a single 4 inch and just shy of a single 5 inch port

Ill do some more research and update on the ports.


budgetwise I have about 600 bucks for the sub, not including amplification, Ill figure that in separately from the sub build.

Something interesting to note is the sonus sub app required at least 4.5 inches between the sub and the floor, I notice my svs pc13-ultra doesnt even seem to have 1/2 that much space. I wonder how and how much that affects performance.
 

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Something interesting to note is the sonus sub app required at least 4.5 inches between the sub and the floor, I notice my svs pc13-ultra doesnt even seem to have 1/2 that much space. I wonder how and how much that affects performance.
Reducing the space between the driver and the floor (or a wall for a side-firing setup) effectively mass-loads the cone, lowering the F3. This is similar to the "proximity effect" with microphones, where where bass repsonse is inversely proportional to the distance from the source to the mic element (though they function on completely different principles). With a speaker, by placing a rigid boundary near the cone you reduce the elasticity of the air column in front of the driver while simultaneously turning that column into a quasi-Helmholtz resonator. The properties of the resonant space you create are dictated by the rigidity of the boundary, the surface area of the speaker plus its baffle, and the distance to the surface. By varying the distance to the surface, you can "tune" the resonator.

You might now be wondering why this isn't done more often... the answer is that nearly every downward-firing subwoofer is designed with this effect in mind, and side-firing subs are specifically neglecting it. Like any design approach, it has its pitfalls. One of the most obvious is that "articulate" bass passages tend to suffer because higher frequencies are rolled off a bit. The other thing to note is that there is a maximum distance at which the effect occurs, and a range where you can audibly detect it. Farther away and it disappears... too close and the sub starts to choke because the air can't respond to the motion of the cone. Attempting to overcome the deficiencies created by an inadequate air space in front of the cone with additional power can result in damage.

In your case, taking the recommended 4.5" gap to the floor and cutting it in half will likely have a pretty noticeable effect on the performance of the system. My guess is that you'll end up with a sub that rumbles pretty well but doesn't handle music as well as it could because the port resonance and the air-gap resonance will not be aligned. You'll end up with a less-than-flat response curve, and a measurable disparity in phase response in the frequency range between those two points. Again, those are just my guesses... but they're based on experience with varying the size of an air gap on a sealed down-firing sub many moons ago.
 

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Discussion Starter #5
DQMclain thats some great info, thanks for the reply, depending on how the project turns out I may tinker with the svs's air gap, either that or Ill sell it and build my 2nd diy!

chrapladm I did some additional modeling for the 18 inch option

end cap to end cap dimensions
h 43 x w 22
D 6 x L 25 port with 1 inch flared ends
18 inch driver
18.5 tuning target

With some driver recommendations I could model around that driver, That seems ideal, Ill do some more forum digging in the mean time.
 

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mikeyd, I think if you're generally happy with the PC13 Ultra, I'd try to put together a similar(ish) sub in appearance and output. Err on the side of overkill, because you'll likely be able to get pretty good performance with a $600 budget excluding the amp. I'd start out looking at similar sized drivers, if a visual match is at all important to you... on the high end, the Stereo Integrity HST-11 or HST-12 would basically eat up your whole budget, but I'm guessing would be capable of crushing the SVS. Maybe look at the Dayton Ultimax 12" (around $180) or the Dayton Reference HO series 12" (for about $150). The Creative Sound SDX-12 falls somewhere in between (just under $300).

Others with more experience modeling all of those will likely chime in to steer you in the right direction. But it is important to know some key information. We have your budget, and presume the baseline for performance is at least to match the PC13. Is the form factor important? Would a visual match be preferable, or can you go off the reservation and build way bigger? If the goal is really just to even out response you won't need to go too crazy.
 

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Discussion Starter #7 (Edited)
I'd like to step up a bit performance wise compared to the ultra. I recently got new denon and LCR and I'm having issues integrating the sub to my liking. The mains dig pretty deep and are very articulate. Particularly with music, I feel that I'm loosing the tight fast punch the mains put out with the sub on. Maybe I just like the Yammy sound better, hard to say yet. That's all probably best for another thread if I don't get it ironed out.

I'm flexible on enclosure design and size. I have moderately large open area and high vaulted ceilings only 2 parallel walls, the front and back unfortunately and they are the tall walls of the vaulted ceilings.

Tube pros are:
Cost, I have a local source for a 24 x 12' for 100 bucks,. I could build 2 and sell the pc13

Placement, my sub currently sits to the left and behind the center channel , I can place the 2nd sub in the same spot but on the right side

Simplicity, easy to build.

If you tell me a box would be better I can do that, I have a big table saw, router and whatnot for woodworking. My stipulation on a box is no MDF. I'd rather work with plywood.

I can flex the budget, I've got about 1400, but I need 2 more volt-10's for heights and an amp for the new sub. Ideally I can build a great sub better than my current one, power it with a big inuke, sell the pc13 and use that money to build the 2nd sub and power it with the inukes other channel.

The ultimate goal though is good even bass. The pc13 is the best sub I've heard,. I've never experienced dual subs so I have no reference points for what better should sound like.

I think I answered everything and then some.
 

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Hi Mikey. This thread speaks to me a lot. I bought a pc12plus and needed more since I have so much airspace, so I built another one using a bash amp and TC sounds epic 12. The benefit of smoothing was good but I didn't really maximize that until I used REW and EQ and added a 3rd sub(long story), but man the extra headroom was almost more worth it. I was thinking in your case a Dayton ultimax or a stereo integrity driver(which I don't know a ton about except they seem to be amazing). My goal is actually 4 rhythmik audio FV15hp's but my wallet and wife seem to be in disagreement with me. So since rhythmik supports diy, I'm thinking I'll buy amps and drivers from them build 2 into sonosubs. Not sure if that helps any but I think it would be worth an email to them. I think a driver/amp kit is about 600 bucks. Should kill your ultra and be more articulate. Fwiw, I love my setup and most do, but I just have too much airspace to fill with 3, 12 inchers. Also, 100 bucks is a rip for sonotube. My local place cut mine(16x36") and for 21 dollars I was done with that part. I'm fixing my computer right now. Maybe I am help with modeling if I get it done before your sub is built lol. Hope that helps some. Fwiw, I love the cylinder design.


Sent from my iPhone using Tapatalk
 

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Stepping up performance would require at least a sealed 18 and a big amp. If wanting to evenly spread out the bass I would suggest at least two 18's or four and placing them sporadically around the room. So many variables though. Four ported 15's would sound quite nice also. Tight on money you could use the Alpine SWS 15's. Variables variables variables.

A pair of 18HST's in 15cuft each ported at 15hz would be quite nice. Add in whatever amp you can afford. SO let us know on how many subs your looking at building. The Dayton Ultimax is a great sub also. The HST seem to perform a touch better on the ultra low end though and have more Xmax. A pair of 18's might be slightly more expensive than a single 24" also.

Is your room on a concrete slab? Do you have multiple spaces for subs? And what are your preferences for bass? DO you like it flat or do you enjoy a healthy rising bass curve?

I have been busy as of late and a bit slack at helping. So I will try and assist a bit more over the next few days. I love my bass and I have had many different setups. I do prefer a rising response myself. One of my favorite setups was four 15's in dual opposed sealed cabinets. Sounded great for me and being on a suspended floor was overkill to say the least. A pair of ported 18's would have been PLENTY for my wants.

So let us know more about your wants and what your dealing with.
 

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Ideally I can build a great sub better than my current one, power it with a big inuke, sell the pc13 and use that money to build the 2nd sub and power it with the inukes other channel.
I think this will be your best bet. I'm not sure what the market is like for used SVS subs, but you should be able to get something reasonable for it I would hope.

I would tentatively say a pair of 18" Ultimax subs (sealed or ported, in tubes or boxes, whatever your preferences) would be pretty amazing. This is a quick and dirty "for my own curiosity" comparison, but let's see how a UM18 sonosub stacks up against the PC12 Plus. Pic 1 shows the output graph from the SVS site.

Pic 2 shows just taking a VERY quick look in WinISD... the UM18 in an 11.5 cubic ft enclosure, ported, tuned to 16 Hz (white line) and sealed in the same volume (yellow line) would use a 24" sonotube about the same height as your SVS, including feet. I'm assuming 1,200w for each one, using a single iNuke 6000 channel. Output seems substantially higher, and this is for a single one.

Yeah, using a 24" tube that's a pretty massive sub, but even cutting it in half it's still workable. The catch is you would definitely need some kind of DSP to add a high pass filter to keep excursion in check below tuning, and you'd want to measure in room and tweak the response further. So an iNuke DSP or a standard version and MiniDSP or something.

UM18-22 - $280(?) x 2 = $560
iNuke 6000 - $350
MiniDSP balanced - $125
That's $1,035 for a pair of pretty bumpin' subs (not including enclosure materials, taxes, shipping, etc.). Moving down to the UM15 (15" version saves you about $100 per driver, and you could probably move down to the iNuke 3000 to save another $120), will still be better than the SVS, especially with some EQ.

Just my $0.02 on a Friday afternoon when my brain capacity is rapidly diminishing.
 

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Discussion Starter #11
Feeling under the weather today so those be a short post.


chrapladm - concrete slab foundation, carpeted floors. A house curve seems to sound better than flat. I posted about my listening area in the last one, I don't mind sharing some pics if that matters to anyone.

Will the ultimax 18 be good for:
music
quieter 60db listening or is it more of a come alive at higher sound levels type of driver?
Big xmax isn't as good for music right?

I like the idea of 2 tube subs with 18's. I'll play around with the modeling programs some more also. Modeling is new to me but I learn fast usually. I'd like to see 20 and 22 vs 24 diameter keeping under 50 inches tall.

I have a Behringer fbd for EQ. It's not fancy but it gets the job done.

Thank you for the responses, it's greatly appreciated

Mike
 

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In terms of a driver's "musicality", Xmax isn't necessarily a good indicator. What's far more important is it's Qts. This is a unit-less measure derived from it's mechanical and electrical "Q" parameters, which are descriptions of how much control the suspension (mechanical Q) and motor assembly (electrical Q) have over the motion of the cone. A low Qts has relatively stronger motor/suspension, and can react strongly to a signal. Higher Qts usually means weaker motors and looser suspension... but unfortunately, it's not that straightforward.

The short version is that in the world of low frequency, a higher Qts driver (neglecting all other parameters) wants a bigger encloser, and a lower Qts driver wants a smaller enclosure. However, one cannot design a box effectively using Qts alone as Vas (the volume of air that, when compressed to 1 m^3, exerts the same force on the cone as the suspension) and Fs (cone resonance in free air) are critical parameters.

A very "musical" sub can be designed with a low Qts driver in a small box, as can a high Qts driver in a bigger box... ports, sealed, IB, LLT, horn-loaded... if the design is good for the driver (and the intent of the system), any of it can work.

As for low-level listening, what's going to be make-or-break here is system sensitivity. Feeding a subwoofer signal levels below "reference" with a low-sensitivity driver will be underwhelming, and if you compensate with more power at lower levels, balance and system integration at higher levels may be off and require adjustment. 88.6dB nominal isn't amazing... but it's perfectly workable. The box will help, and with two separate drivers and boxes, your sensitivity is increased by a significant margin and you're much more likely to overbalance the rest of your system than you are to under-balance it. That's an easier problem to solve in the long run. In any case, you're pretty likely to notice the "come alive at higher volumes" phenomenon. It takes vastly more knowledge and experience than I have time left in my life to learn before I can tell you how to get around that problem... that's why good subs are expensive. When it comes time to drop the hammer and dispense some indiscriminate justice, more is more. The 22mm Xmax from those Daytons will displace more air, which is directly proportional to the happiness of the listener and inversely proportional to the happiness of their neighbors.

EQ - the Behringer FBQ is a much more powerful tool than a lot of people give it credit for. You're in good shape there.
 

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Discussion Starter #13 (Edited)
Hey all, moving a little slow, been fighting the flu since friday.

Ive been playing with winisd and want to make sure some of my conclusions are correct.
box volume is directly related to the tuning point, port length lets you tune the response curve,
Is there a good resource you can point me to to read, I prefer to understand at least a small percentage of what im doing before winging the rest.

Ive not been unable to get as flat a graph out of winisd as the previous poster so Im definitely missing something.
{Edit} I figured out the flatter looking graph
 

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Hey all, moving a little slow, been fighting the flu since friday.

Ive been playing with winisd and want to make sure some of my conclusions are correct.
box volume is directly related to the tuning point, port length lets you tune the response curve,
Is there a good resource you can point me to to read, I prefer to understand at least a small percentage of what im doing before winging the rest.

Ive not been unable to get as flat a graph out of winisd as the previous poster so Im definitely missing something.
{Edit} I figured out the flatter looking graph
Unfortunately, setting a box volume and tuning the response curve with the port length is not quite that simple. Yes, the box volume will affect the the tuning point, and yes the port length affects the point at which the port resonates, and yes adjusting the port length will move the resonance frequency of the port and therefore alter the curve of the box. HOWEVER... the total volume of the port is subtracted from the total volume of the port. So an increase in the length of the port results in an increase in the volume of the port, which is then subtracted from the volume of the box. So by increasing the port length without the corresponding change to box volume, you lower the port resonance, but raise the box resonance. If you compute the box volume based on a desired tuning point for the system as a whole, and that volume takes into account the air displaced by the port, and the port dimensions are optimal for the desired tuning point, you'll get a nice curve. If you shorten the port length, it's resonance goes up, but the box volume increases lowering the tuning point of the box. The inverse is true for an increase in port length... longer port means lower port resonance, but smaller box volume and corresponding higher tuning point. Either way you adjust, you're moving away from an optimized system... at least on paper.

The other thing to keep in mind is that the relative volumes make a difference. If you have a small box and a large port, a change to the port length is going to be a larger change to the box volume relative to the total and have a larger effect on the tuning point. Again, the inverse is true... for a large box with a relatively smaller port, changing the port length will amount to a smaller change in the box volume relative to the total and have a correspondingly smaller affect on the tuning point.

It would be nice if something were just easy for a change. Sorry about that.

I use this handy-dandy calculator from Mobile Information Labs to calculate a port length for a given tuning point.
http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL Port lenth 1.htm

It doesn't make account for any of the effects described above, but for a given box volume and tuning point and port diameter (or area for a square port) it will tell you how long the port needs to be.

Hope that helps more than it hurts. Or Hertz.
 
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