[grendel]

I'm rather new at DIY (if i had a nickel for every time i've read that on a discussion forum...) and quite a novice at woodworking as well, but I'm itching to tackle a sonotube sub project.  I've spent the better part of a day looking across the web at information, but it's possible it hasn't all settled into my brain quite yet -- I thought I would get opinions from you all before I bought anything.

The story so far:
Location: I have a living room in an apartment that is about 12x15 or so, opening on to a kitchen and dining room area that are another 10x20 or so together.  

Purpose: Mostly music.  It will perform home theater duty as well, but that's very secondary.  

Plan:
I'm thinking about an Adire DPL 12 in a downfiring, sealed sonotube that poses as an endtable in the corner of the room.  
The DPL12 would be mated to a Parts Express 250w amp (with bass boost?) that i imagine would be external.
According to my calculations, using 24" sonotube with 20" internal height would give roughly 92 L, or 3.4 cu ft.  Someone on some forum somewhere (wow, i really am awash in information...) said that the DPL12 should have 3-3.5 cu ft. of space, ideally. I imagine they were assuming polyfill stuffing.

Any comments? Suggestions on how to make it better/different? I'm still tossing around ways to create the round endpieces...with just a cabinet saw as a tool, i'm not sure how possible that will be. I may need to talk to a local carpenter...?

Thanks for any help you can give!

[randytsuch]

I'm rather new at DIY (if i had a nickel for every time i've read that on a discussion forum...) and quite a novice at woodworking as well, but I'm itching to tackle a sonotube sub project.  I've spent the better part of a day looking across the web at information, but it's possible it hasn't all settled into my brain quite yet -- I thought I would get opinions from you all before I bought anything.

The story so far:
Location: I have a living room in an apartment that is about 12x15 or so, opening on  ...

I have seen places that sell sub enclosures, I think diycable does, and parts express.  Some people sell the enclosure pieces (easier to ship), then you put the pieces together, and then add the driver and amp.  If you are a novice, might consider this approach, as it would be easier then building your own enclosure.

There are places that sell  drivers, and also have plans for enclosures, I remember seeing these, adire might be one of them.

Randy

[Jason1]

www.acoustic-visions.com

[WerTicus]

yeah pently of places will sell you a really great 15mm ldf box for a subwoofer... w00t!

the sono tube sub's a winner, and sealed is the way for musical so yay... good luck with it and let us know how it goes!

[grendel]

True, I thought of buying a sub enclosure. But i'm a dangerous mix of cocky and cheap, so building a sonotube seems to appeal to me...I haven't found a dealer nearby that sells < 12" sonotube yet but I still have some calling to do. If that doesn't work, of course, a square enclosure a  la  partsexpress is a possibility.

Jason1 -- I called Kyle from acoustic-visions last night to order the amp and driver. Great guy!  I wouldn't hesitate getting an enclosure or whatever else from there.

WerTicus -- i will keep you all posted. I look forward to being able to post a bragging-rights thread with pictures and such. That is, if it turns out to be even mildly photogenic...

[theint]

I would not get the bass boost built into the amp. I assumne you are getting a half descent speaker. Flat response always sounds the tightest.

[WerTicus]

its sealed so it will fall off and need equalisation or bass boosage.

[grendel]

Thanks theint.  Sounds like a good call.  The idea of artificially boosting a particular frequency does sound kind of like it's making up for a bad speaker, doesn't it?

On that note, purchases are made:  partsexpress amp (250w, no bass boost), Adire DPL12, binding posts. I'm still trying to scratch up sonotube (have to call some local concrete supply people).  Still thinking of interesting ways to cover it as well; I'll have a tabletop of some sort but not sure about outer covering yet. Creative ideas welcome.  Anyone tried faux leather yet?

[grendel]

Hmm..interesting WerTicus. I suppose it's something I'll have to check out -- the PartsExpress amp has instructions for adding bass boost (changing a resistor on the amp), so I can play with it a bit and see how it seems.  Equalization I can understand I suppose, but adding a spike at a particular frequency doesn't sound (from a purely theoretical level) very "realistic".  Perhaps it's just a preference thing.

[grendel]

(perhaps I shouldn't make calls about the theoretical -- i'm obviously painfully new at this)

[EProvenzano]

You won't necessarily be adding a 'spike' in the response. The idea will be to add a few db's of boost at a specfic frequency; when coupled with room gain, will yeild a flat in-room response.
The sealed sub you plan on making will likely roll off a little quicker than room gain will add to the response. Therefore the boost at 20-24 hz is required to bring you flat response. This is all very dependant on your sub, room and speaker positioning.
I like you're idea of setting up the system, later doing some listening evaluations, and tweaking the PE amp as necessary.

Good luck!
EP

[WerTicus]

any sealed design will fall off faster than a ported.... so you need to compensate for this

for example the 80litre sealed shiva falls off at around 30 hz so if you dont compensate for this your not getting much 'sub' out of your subwoofer

If you compensate its going to require a lot more power... I wouldnt know if 250w would be enough for you at your desired volume, but you can therefore make it go down to 17hz

You just cant achieve the 'virgin' 'tightness' with anything other than sealed... though transmission lines come close, but they are heaps of work to make.

[_scotty_]

WerTicus,  Here is a link to graphs illustrating that exactly opposite of what you stated as the relationship between vented and sealed alignments
is actually the true state of affairs.  http://www.audioasylum.com/forums/pi/messages/2062.html

 The black line on the graphs is the amptitude response of the system
being discussed in the text. The dotted line shows the 3 db. down point.  As you can see from the graphs a sealed system that is critically
damped to use the authors term has a 12db/oct slope below system resonance and a vented system has a 24db/oct slope below resonance.

[WerTicus]

opsy...

yup thats right it dosnt actuall fall off faster it falls off slower

but ... what i ment to say was the sealed box drops below -3 db at a higher frequency than the ported and as such requires compensation to hit those lower frequencies with a flat response.

thanks for pointing that out there scotty!

[PeteG]

Grendel

I've had good luck so far with a 75liter sealed box using a Adire DPL12 driver. I'm trying to find time to play with the damping & placement, right now I have some humps & nulls but thats from the room I will have to get another parametric EQ to fix it. I made two subs for 2ch music system not HT.

Here's some good info for the Adire DPL12 sealed box
Adire DPL12

[grendel]

Nice pic, PeteG.  Out of curiosity, why a 75 liter box?  Was it for sound reasons or mainly space concerns?  

_scotty_, very interesting link.  The rolloff does start quite high with a sealed box. Perhaps a basic question as followup: How does one determine the "optimal" damping? I'm afraid my models for the cabinet size I'm talking about have looked more like the overdamped models in the pictures; Wayne Parham in that link mentioned that the distortion would rise as a result.  Perhaps that's just basic speaker theory that I've passed over, sorry.

[_scotty_]

A total system Qtc.of .707 is generally considered the best use of a woofer
in a sealed box design. The response has no dips or peaks in response and has the best bass extension for the box size used.  If a sealed system
 is equalized to achieve a lower 3db down point it will always come at the price of increased bass distortion. The in room response gain due to room loading effects has not been mentioned.  With the slower rolloff rate a sealed system has it can have a 3db. down point in the middle 20's
depending on the position in the room and its original 3db.down point.
 PeteG,your in room bass response anomilies can be mostly eliminated with a third sub operated in the rear of the listening room with the amp that drives it operated out of phase with the front channels.  This is best done with a plate type sub amp with fully adjustable phase capability.      You can simulate most of the effect by placing one of the subs you built in the back out of phase and run it at a much lower level than the front,ideally you would not know it's on until you turned it off.

[PeteG]

Scotty
I have a older 8" sub w/plate amp and with a phase switch.
Any help with room response I'll try, but my wife is going to kill me.

Thanks Pete

[grendel]

Thanks _scotty_.  I had read somewhere that a lower Qtc (.6 or so) was preferred by "audiophiles" (i presume because the 3db down point was higher but the curve was flatter up until that point?) and a higher Qtc (up to .9) as being for home theater, presumably because it got down low but had a "boomy"/distorted response. A Qtc of .707 was characterized as a compromise between home theater & audiophile; since I figured I was more interested in music than home theater I aimed lower (perhaps deep inside there's a audiophile-wannabe).  
Unfortunately, I didn't quite understand what I was reading at that point.

With a Qtc of .707 in mind, I'll refactor the size of my enclosure.  
Room gain is another issue I haven't even begun to tackle yet;  I'm not even sure how tol measure my room gain when i get things set up.  More FAQs to read, I'm sure...

Good to hear these things before I build! Thanks all!

[_scotty_]

PeteG, Is there is anyway to sneak it into the back of the room and maybe put a potted plant on top, you could call it a new plant stand. The sub is about what I had in mind it doesn't have to play as loud as the mains to cancel out part of the problem because the bass is attenuated by leakage out of the room and absorption by the room furnishing and the
building structure. I would try crossing over the rear sub at 150Hz and
working your way down from there.  Room interaction effects become progressively more pronounced below 150Hz. If you crossover too low you will miss the midbass problem region which is usually a result of room dimensions and resonant modes. Good luck. If it is working correctly your
wife will never know its on.