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Discussion Starter #1
So I'm entertaining the idea of building a DIY sub. I don't have the necessary woodworking tools myself but know someone who does. Let me put up a hypothetical budget of $600 for drivers, amp, and cabinet materials.


The room this will be used in is right at 1000 ft/cu, so pretty darn small. I want to achieve at least reasonably flat response down to 20Hz with the best possible sound quality within the posted budget. Currently, I am using an M&K MX-70. It's a dual 8" push-pull design with a 125W amp. It's extremely tight, but starts to roll off under 30Hz. For its size, the amount of bass it can put out is impressive, but it can sound strained or even bottom out easily with big movie soundtracks and some very bassy music.


My set-up is 80% of the time for music (and the MX-70 hardly lets me down here) but for the remaining 20% of the time watching movies or playing games, I want much more extension and power.


First, I don't know what design will suit my needs best. I'm leaning towards sealed for arguably tighter sound and a smaller footprint, but could go ported if it wasn't too big and didn't sound boomy. I think doing a dual push-pull, M&K style or otherwise, would give the least distortion but could I get similar results with a single 15" than with dual 12"s?


Basically, for all you sub experts, what would you build for a room this small to get the best sound and good extension?
 

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Discussion Starter #3

Quote:
Originally Posted by Jack Gilvey /forum/post/12915733


For that size room a sealed Rhythmic might be really nice. He offers a dual-12" kit for $599.

http://www.rythmikaudio.com/products.html

While that would bring the total over budget, those drivers look NICE.


Question though. On the site, it says a 2 cu ft sealed box is good for one driver. But with the dual option, it says 3 cu ft per driver. Why is that? That would mean I'd need a sealed enclosure of 6 cu ft? That's a lot bigger than what I was designing for...




edit: On the product page it says "Sealed 3 cu ft (2 drivers)" for the dual option. Now I'm really confused. A 3 cu ft box would be much more doable.
 

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Quote:
Question though. On the site, it says a 2 cu ft sealed box is good for one driver. But with the dual option, it says 3 cu ft per driver. Why is that? That would mean I'd need a sealed enclosure of 6 cu ft? That's a lot bigger than what I was designing for...


edit: On the product page it says "Sealed 3 cu ft (2 drivers)" for the dual option. Now I'm really confused. A 3 cu ft box would be much more doable.

I think it's 3ft^3 per driver for the dual (which uses a slightly different driver I believe, as does the "compact" kit). Since the dual kit (listed as currently unavailable) uses the same wattage into two drivers instead of one, I imagine Brian wanted to keep the low-end efficiency up with more Vb. I'll bet an e-mail to him would clear it up.

There's also the 15" kit, which calls for a 3ft^3 box. In that size room, I think you might be happy with the single 12, but the 15 offers ~5dB higher output.
 

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I don't own one of Brian's kits. That being said, unless you just can't fit a 3 cube box, I'd definately get the 15 HXO version even if you don't need all it's output in your 1k room. Bigger cone, less cone movement for the same SPL, lower distortion. Plus more versatile if you ever move to a larger space.
 

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Flat to 20Hz with $600 means ported for sure unless you want to use Linkwitz Transform, but then you'll need a LOT of power. Ported doesn't mean the quality is lower. People say sealed bass is "tighter," but that's a myth.
 

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Quote:
Flat to 20Hz with $600 means ported for sure unless you want to use Linkwitz Transform, but then you'll need a LOT of power.

The switchable eq (not a LT) in the Rythmiks would likely allow flat extension well below 20Hz in that room, so the question would be one of headroom and desired size.
 

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Discussion Starter #8
What about using two of the DS12VC drivers in a 3 cu ft box? Not a good idea?


Two of the Eminence Lab12 Gen 2 look like they would work well in a 3.5 cu ft box, but there are so many 12" subs out there I have no idea what would be best.


Also, do you think the benefits of a push-pull would even be worth it if I go for servos anyway? Making a sealed or ported sub with one of those 15" Rythmiks would be nice.


Every p/p M&K sub I've heard has sounded amazing though so there must be something to it...


edit: Also, this design looks like exactly what I'm after. Comments?
 

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Discussion Starter #9
Did some plotting with vented designs. I think I would be willing to go up to 5.5 cu ft so I modeled the Shiva-X, the Dayton 12" RS and the Rythmik 12" servo.


The Dayton was the flattest but the Shiva had the best balance of output and extension. This post is pretty much the design I'd want to go with. 5.5 cu ft would be slightly bigger.


I have a feeling this sub would just KILL in my room, but how good would it sound? Is the Shiva good for music? Would the Dayton sound "better"?
 

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I'll second the Rythmik Kits. I've got the DS12 kit in a 2cf box which has no problems flat well below 20hz in a 1500cf room. With your budget I'd shoot for the DS12D or DS1500.
 

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Pretty much all of these are great, but you really need to remember that xbl is just one way to get low distortion, and definitely not the only way, it just so happens that there have been several very low distortion designs recommended here and that is not what separates the shiva apart here. The Dayton RS subs are the lowest distortion subs that some of the diy reviewers have ever tested, period. The rythmic kits are also exceptionally low distortion as well, with a servo motor they are capable of exceptional linearity. Without some tests, its hard to say which sub has the edge in SQ, but personally, I'd throw my money on the rythmic 1st, the dayton 2nd and the shiva last, but keep in mind that theres plenty that the shiva outperforms. Where the shiva really shows its colors is in its ability to deliver about twice the output of these other subs and still sound great.


Just because he said he wants these for music doesn't mean that any of those three subs can't satisfy his needs for SQ, believe me, these drivers are top performers in the sq department, the only reason to get more expensive subs would be for more output or a smaller enclosure, there is no loss in articulation here.


The challenge lies in mating the drivers with the right boxes, in the wrong enclosure, any of these can sound like garbage, and in the right box, even lesser subs can sound incredible.


You have been given several great ideas, my favorites are dual rythmics and a single shiva X, the shiva will have an edge an output down low, but make sure you use a large enough port, this is absolutely critical. Many of us here are used to 4" ports being sufficient for 12's, that was when 12's with that much excursion were lower on the lineup of much more powerful subs, making 12's in those series's somewhat impractical to port. this is no longer the case with the shiva, it loves to be ported, but it needs at least a 5" port, and preferably a 6" port to keep that airspeed and compression down. This is where you can tell it was designed specifically for DIY home uses, Dan did (it was dan that designed these right?) a very good job in mating the vas/qts with the right bl and excursion to allow very large ports and nice big enclosures to get the job done, with a low enough fs to keep port resurgence from rearing its ugly head.
 

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Discussion Starter #13
Thanks for the helpful info. In WinISD though, for the single Shiva-X in a 5.5 cu ft box @ 17.6 Hz tuning, a 6" port would have to be 40" long.
A 4" would only have to be 17" which is exactly the length of the PE kits. That shiva build I linked uses a 4" port. Would it really be a compromise if it's not going to be pushed to its limits?


Also, with the shiva, if I make the enclosure 7 ft cu with the same tuning of 17.6 Hz, the graph looks ruler flat all the way to 20Hz with a -3dB around 16Hz. My question is, would this ACTUALLY be flatter in-room than the 5.5 cu ft box? Or would room gain boost the low output making the actual response much less accurate?


Basically, what should I be looking for in the graph to tell me that the sub will have a flat response in real life?


edit: And finally, does anyone still think a push-pull would be worth the extra expense, or would I get all the extension and low distortion I need from a single driver build?
 

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Quote:
Originally Posted by Pibbo /forum/post/12926509


edit: And finally, does anyone still think a push-pull would be worth the extra expense, or would I get all the extension and low distortion I need from a single driver build?

Depends on how loud you want.
 

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Quote:
Originally Posted by Pibbo /forum/post/12926509


Thanks for the helpful info. In WinISD though, for the single Shiva-X in a 5.5 cu ft box @ 17.6 Hz tuning, a 6" port would have to be 40" long.
A 4" would only have to be 17" which is exactly the length of the PE kits. That shiva build I linked uses a 4" port. Would it really be a compromise if it's not going to be pushed to its limits?


Also, with the shiva, if I make the enclosure 7 ft cu with the same tuning of 17.6 Hz, the graph looks ruler flat all the way to 20Hz with a -3dB around 16Hz. My question is, would this ACTUALLY be flatter in-room than the 5.5 cu ft box? Or would room gain boost the low output making the actual response much less accurate?

Don't worry about ruler flat responses, your room will take care of anything ruler flat and throw 3-10dB dips and peaks at it until its pretty messy. You could use the 6" flared port and just tune to 18Hz, with a bit of stuffing this will drop a bit too. 36" is kinda the rule of thumb around here for port lengths, some people like to keep them under, others go out to 40 sometimes, its really up to your setup. We generally go a for response that curves downwords a bit very gently before it hits 20Hz. How much boost your room gives depends entirely on the size and shape of the room and the subs placement and your listening position.

Quote:
Originally Posted by Pibbo /forum/post/12926509


Basically, what should I be looking for in the graph to tell me that the sub will have a flat response in real life?

Again, this depends entirely on your sub and room, generally speaking, I go for sub thats gently 3-5dB down at 20Hz and 6-10dB down at the tuning, but in the end, I sometimes am just trying to make it work out, and so I try not to caught up with this, it depends from driver to driver, some do funky things, I like it when they don't.

Quote:
Originally Posted by Pibbo /forum/post/12926509


edit: And finally, does anyone still think a push-pull would be worth the extra expense, or would I get all the extension and low distortion I need from a single driver build?

I really don't recommend a push pull, its a lot of money and for what? Your not getting the benefits of a ported sub, (or pr'd) or both drivers. There was only one time that I have recommended a push pull/isobaric subwoofer, and that was with some $25 buyout subwoofers, don't design your $600 sub around this.


*Edit* You can also try a 5.5" port from here http://www.harvel.com/pipepvc-sch120-dim.asp
 

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Quote:
I really don't recommend a push pull, its a lot of money and for what? Your not getting the benefits of a ported sub, (or pr'd) or both drivers. There was only one time that I have recommended a push pull/isobaric subwoofer, and that was with some $25 buyout subwoofers, don't design your $600 sub around this.

It's not isobaric he's referring to, just push-pull with drivers acoustically in-phase but one mounted in reverse and electrically out-of-phase (as shown on the Rythmik site). If using two drivers anyway, there's no reason not to go this way, but I wouldn't base a design on it.
 

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Discussion Starter #18
Ok. So I remodeled the drivers with the gradual roll-off in mind and ended up with a 4.5 cu ft box for each (much more doable for me). The Shiva has the most output down low, but the Dayton isn't far behind and looks flatter in the midbass. With what you said about the Dayton being very low distortion and having great sound quality, I think I'd want to go for that. It's also the cheapest of the three.



Now, how does stuffing change the perceived volume of the enclosure? Also, if you do multiple ports, they each have to be the same length as if you had one, right? Two would just make the vent speed half that of a single?


For my purposes, I need either a downfiring port or frontfiring. In my position, would you go for a frontfiring woofer with a downfiring port, a frontfiring woofer with a frontfiring port, a downfiring woofer with a downrifing port or a downfiring woofer with a frontfiring port?



Thanks.


edit: PIC!
 

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I would put money on this one..... there is no way that the Dayton is going to beat the Shiva-X. I has just barely over half the available excursion and moving air is what bass is all about. Even if the Dayton was a couple percent better THD at low-levels (which I'm doubtful that it is considering what I know about both), you would still be giving up a significant amount of headroom across the range just for a meaningless difference in THD at low levels. That doesn't make good sense.
 

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Discussion Starter #20
Aw, just when I thought I had it figured out...


Ok, well if I went with the shiva, looks like I'd pretty much be copying this verbatim, which makes things easier on my end.


However, that amp is no longer available. Is it worth it to get the SE for $250, or are there other 300-500 W amps that would be just as good for less?


edit: Hmm, maybe this amp?
 
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