[IronGiant]

In order to design a box, you need to know the characteristics of the driver. The most useful ones are the thiele parameters. The better quality the driver the more of these are likely to be available, have a read here:

Thiele/Small - Wikipedia, the free encyclopedia

WinISD takes these parameters and designs a box to suit. You need to decide if you want a sealed or a ported sub and whether you want a box or a cylinder. I used to be able to punch these numbers into WinISD but if the program has changed massively I'm sure some of the other guys here can help me out

Dave

[Russell.Williams]

Originally Posted by gperkins1973

The other option I was thinking about last night was a tall square sealed sub with 4 15" subs, 1 above each other on each side then I could place in the corner.

I have a mac at work but I can't find any software available for the mac.

Graham

What exactly are you trying to achieve?

Russell

[gperkins1973]

Russell,

Right here goes....

I am thinking of something like the seaton submersive with dual opposing drivers. In the submersive they are 15" drivers but I was thinking of 18" driver instead with a behringer 2500 or 4000 amp. I need a sub that is much better with music than the PB13 and goes as low. My main issues with the ultra is that it doesn't have enough upper bass slam. Perhaps I am being a bit greedy.

This is the reason I think sealed is the best option for me but I want lots of bass, even more than the PB13 can offer.

Or even two 18" sealed boxes maybe. I am open to suggestions as this is really unknown territory to me.

cheers

Graham

[Russell.Williams]

The figures I'm getting for a 15" driver in a 75L sealed cabinet would already make a PB13 blush. Assuming 800w out of an EP2500, it models in WinISD as producing 106dB @ 20Hz but bear in mind that's sealed, so roll off is much shallower than a ported sub. At the same time the un EQ'd response will give up to 120dB in the upper bass so using EQ it should be perfectly possible to achieve a solid 109dB performance with an F3 around 20Hz with only a sealed 12dB/octave roll off below that.

That's before factoring in room gain (6dB/octave below the first room mode frequency in my room) and the fact that I'm going to build two subs giving another 3-6dB of gain.

If I don't get at least 110dB @ 20Hz I'm going to cry.

You'll have to ask Moonfly what he's got planned.

Projected figures aside, the point is we're going to be using Acoustic Elegance AV-15X drivers which we've chosen because of their very clean and extended upper bass response, precisely because of the music performance we're chasing.

For mentalists chasing sheer SPL then the CSS SDX-15 Subduction may be a better bet, but it's high inductance rolls it's FR off a lot earlier, which also slows it's transient response.

Russell

[gperkins1973]

Russell,

The figures I'm getting for a 15" driver in a 75L sealed cabinet would already make a PB13 blush. Assuming 800w out of an EP2500

I take it that is a single sealed square box sub. What are the dimensions of that box.

The other option is to use passive radiators but I am not sure how quick subs roll off with PR's.

Any ideas what a dual 15" sealed sub would be like in terms of dimensions based on the sub you are using just to get an idea.

cheers for all your help in this Russell. Much appreciated.

120db without room gain at 20hz . I'm almost wetting my pants!

Graham

[Moonfly]

Originally Posted by gperkins1973

The other option I was thinking about last night was a tall square sealed sub with 4 15" subs, 1 above each other on each side then I could place in the corner.

I have a mac at work but I can't find any software available for the mac.

Graham

This is software for the mac for running projected sub simulations:

MacSpeakerz, Loudspeaker Design Software for Macintosh: Demo Download Page

Should help with any ideas you have.

Originally Posted by IronGiant

Damn, don't I even get an honourable mention for spilling the beans

Dave

No, you get a slapped wrist

For those that are interested I guess I may as well share my plans. The amp of choice for me (which I have already purchased) is an EP4000, which should give me around 2 x 1400watts. Thats 1400 per driver so possibly a 2800 watt sub . After my MK demo Ive decided to follow in their footsteps try reproduce a push/pull dual driver design and using the 2 15" drivers Russell has pointed out.

Heres what I'm thinking, and what and why I gonna build. Ive settled on a box of around 150 litres (PBU is around 110 IIRC) that will be 500 x 500 x 1000. I'll place one driver on the bottom firing in and the main driver on the front face a la push pull. The drivers were chosen as Russell says for upper bass prowess, and to give me plenty of depth AS WELL I'm going with a large box and 2 large drivers. I'm hoping I'll get an amazingly musical sub that goes low as easily as the Ultra. I'm going sealed to move away from all that chuffing debate and I'm supplying it with plenty of power to help offset the slight inefficiency that can arise from going with a push pull. The push pull should help keep distortion to a minimum as the sub is pushed a bit harder to so I'm hoping for a very accurate sound.
So to sum up, hopefully I'll be left with a sub thats deeper than my old one, louder, more accurate and better with music. A big ask I know, but the more I thought about it the more I felt I just had to try.

SWMBO decided to leave my camera in the town center in a bar, but I'll try sort that so I can put a full progress build thread up for anyone wanting to follow it.

Initial projections look impressive as Russell says. I'm hoping my larger box will go a bit deeper so a side by side test of the finished products will be extremely educational if russell is up for it. Anyone who knows me also knows I dont mind giving the odd demo too, so there may be a chance it goes up for review, especially if Russell gets involved.

So much for keeping it to myself

Should even make this sound good:

http://www.youtube.com/watch?v=ACsYW...eature=related

That ones for any radio one fans out there

[m4rky_m4rk]

I take it you have resorted to self build because there is no commercially available sub that can do what you want within a reasonable budget?

Why not an IB using the room upstairs

I am hoping to get a new house built with dedicated HC room. Cellars are very common here and no doubt I will have a cellar. It may be an ideal opportunity to go the IB route. The trouble is I know nothing about self build of subs. So the chat here may help me on my way in the learning curve.

[Zorba_8]

Originally Posted by Moonfly

SWMBO decided to leave my camera in the town center in a bar, but I'll try sort that so I can put a full progress build thread up for anyone wanting to follow it.

Initial projections look impressive as Russell says. I'm hoping my larger box will go a bit deeper so a side by side test of the finished products will be extremely educational if russell is up for it. Anyone who knows me also knows I dont mind giving the odd demo too, so there may be a chance it goes up for review, especially if Russell gets involved.

So much for keeping it to myself

I think you're going to get quite a few takers there Moonfly! I've not been up North in a while

Sounds like this going to be an incredible sub...a commercial enterprise in the making!!??

[Moonfly]

Originally Posted by m4rky_m4rk

I take it you have resorted to self build because there is no commercially available sub that can do what you want within a reasonable budget?

Why not an IB using the room upstairs

I am hoping to get a new house built with dedicated HC room. Cellars are very common here and no doubt I will have a cellar. It may be an ideal opportunity to go the IB route. The trouble is I know nothing about self build of subs. So the chat here may help me on my way in the learning curve.

An IB wasnt an option for me. You pretty much hit the nail on the head though, there is nothing under 3k worth even considering going up against the SVS. Most subs even at that price will only be a match and its a lot to pay for added musicality. One reason I didnt keep the MK's is because I would have missed that depth. Only obvious route to me seemed to be DIY.

I knew nothing of self build really before this, but there is a heck of a lot of it going on across the pond and it was my inspiration, especially as a lot of the top subs seem to be from people making them their self then starting selling them. I did a lot of reading up and got some help from the right places, but this is still my first attempt. If it works then great, if not then I'll be going back to the SVS make no mistake. One good thing though, my new sub will actually have a smaller footprint than the SVS and that is guaranteed , of course it will be a bit taller.

[gperkins1973]

dan

this sounds what Ive been looking for. Have you got some drawings of what your making.

How much is the total cost going to be so it gives me an idea.

I was thinking along the lines of a submersive which this sounds similar.

What finish are you looking at.

I look forward to seeing your progress report.

cheers graham

[Moonfly]

Total cost should come in around £700 with a basic finish, but if testing results are favourable I dont intend to go for a budget finish. I have a friend of a friend that does body repair and can mix up anything I want and finish the job nicely, at the minute I'm thinking of gloss black, possibly with a metallic tint thats a dark red, like scarlet or maroon.

Most of my sketches Ive done on paper for myself. I had a look a sketchup but was too lazy to learn the program to produce anything of real value. The box will basically be 500 square and about a meter high. The amp will be kept out board with nothing more than a bi-amp terminal seat at the rear, this makes calculations easier and allows amp experimentation without touching the box. Around 200mm of the box at the base will be the area the back of the bottom driver lives. Bracing will be taken care of with a base plate identical to the MK MX one, then a bottom shelf for the bottom driver to sit in, an internal brace will sit half way up the internal 800mm high void and then the lid. Its a difficult design to get the bracing right for, and its not as easy to get as much in as I would like so Ive had to compromise a bit to get a good balance of size, volume and bracing.

You'll need to do a bit of homework Graham. You need to find a driver that does what you want, a well matched amp, the optimal cabinet size and then figure other things in like if you want foam lining inside you cabinet. There is a lot to take in and I found it a bit of an information overload to begin with. I'm still not convinced I really know what I'm doing , the proof will be in the pudding.

[gperkins1973]

Dan

That's some serious wattage going on there mate. I am going to read up over the next few weeks and learn what I can. I think the first step is for me to get a laptop and download winsd. I am still leaning towards a push/pull dual 18" sealed sub (horizontal like the submersive) as it would probably be easier to work.

I need to read up how the push/pull works as I thought it was when both the driver go out and in at the same time rather than say one goes in and the other goes out. If it is them going out at the same time how would you get them to do that.

When are you starting your project?

One more thing the link you sent me, thanks for that but it's for the old Mac OS system software. cheers anyway though!

cheers

Graahm

[Russell.Williams]

Originally Posted by recruit

This is turning into a DIY Sub Forum and IB is not too far behind now either, surely there should be a Sub Forum for DIY and IB off of the main sub forum...

I would agree if there were enough people doing either to generate the traffic required to make it interesting. As long as the threads are kept tidy (and Iron Giant's sub is DIY after all), I think this remains the best place for it as it will open the world in generals eyes to the benefits (and pitfalls) of rolling your own.

It's either that or you're worried about your sub no longer being the most desirable push/pull on the forum.

Russell

[Moonfly]

Originally Posted by gperkins1973

Dan

That's some serious wattage going on there mate. I am going to read up over the next few weeks and learn what I can. I think the first step is for me to get a laptop and download winsd. I am still leaning towards a push/pull dual 18" sealed sub (horizontal like the submersive) as it would probably be easier to work.

I need to read up how the push/pull works as I thought it was when both the driver go out and in at the same time rather than say one goes in and the other goes out. If it is them going out at the same time how would you get them to do that.

When are you starting your project?

One more thing the link you sent me, thanks for that but it's for the old Mac OS system software. cheers anyway though!

cheers

Graahm

Is there any particular reason you want to try push pull? Most people dont go with this but rather opt for a more traditional design. There is no issue with using multiple drivers though.

As for my project, its already under way. I'm going picking up my amp either tonight or tomorrow. The drivers will be ordered v.soon and I'mm going to order in the MDF in a couple weeks of so. I reckon I should have it up and running within 6 to 8 weeks.

[gperkins1973]

Dan,

Only because the submersive has had such good reviews that I want one but can't justify the expense of getting it fully built by Mark Seaton so diy is the only option. From the very brief bits I have read the push and pull gives you tonnes of headroom and spl with little distortion. Tell me if am wrong. Also on the submersive there is little resonance through the cabinet. I would like to do a 18" dual version. (Horizontal version)

I have read (and this is by Mark himself) the submersive is better below 15hz and above 24hz with alot more spl above 30-40hz.

The terraform he is now working on (bigger brother to the submersive) apparantly smashes that.

The trouble with me is I get bored very quick and the other problem is that I have been spoilt with having the SVS subs and reading more and more about USA subs.

I also think I was spoilt when I had the Sunfire HRS-12 as that was better up the mid to high bass than both the PC13 and the PB13 so I am still missing out on music and I am finding I am listening to music as much as watching films.

I am open to any suggestions with regards to different ideas that can also give me the same results.

cheers

Graham

[micb3rd]

ED did have a UK Distro a while ago (they have had couple over the last 5-6 odd years).

The single driver prices from the last Distro were fair value but the subwoofer, plate amp box combos were not that good value for money.

[Ash_May]

Importing components from the US is just about bearable but I can imagine the size and weight of the finished box being a lot more costly.

[gperkins1973]

Defo agree to that. ED subs have a great name on the avsforums along with Epik but they don't ship to the UK.

I wish I could just affors a submersive and be done with it but the diy route sounds interesting. Just got to read up now.

cheers

Graham

[Russell.Williams]

Some points to note:

The Seaton Submersive is not a push/pull, it's simply an opposed twin driver sub. The difference?

To be a push/pull one driver has to point out of the box (in the traditional fashion) the other has to point into the box with the basket and magnet on the outside. Why? Whilst both cones are pushing in and pulling out of the box at the same time, one is effectively doing it in reverse compared to the other. This has the effect of cancelling even (2nd, 4th, 6th, etc) order harmonic distortion, plus the usual dual driver benefit of either halving the cone excursion (which also reduces distortion) for a given volume level, or doubling the maximum output depending on what you are trying to achieve.

By comparison, simply putting a driver on opposite sides/ends of the enclosure a la Submersive achieves the same doubling of output/ halving of excursion, but simply adds force cancellation to the equation to put less mechanical energy through the cabinet into the environment. It does not address the cancellation of even order harmonic distortion.

Indeed, there is no reason why you can't combine the best of both worlds and mount the drivers in push/pull at opposite ends of the same box except that the back of drivers aren't typically the most attractive thing to look at. This is why the reversed driver sits under the box in MK subs.

Either approach results in exactly the same output and low frequency extension as two separate subs of exactly half the size when co-located. A 150L twin driver of whatever configuration will therefore give exactly the same output as a pair of stacked 75L subs using the same drivers.

This is why it's interesting in so far as Moonfly and I have chosen the two different configurations - his 150L push/pull, mine separate 75L sealed jobs. He wants to minimise distortion at all costs and has a position in his room which offers up a nice resposne for one sub; I think that I don't need the extra output co-location affords and that distortion will be low enough and am more interested in achieving a smoother in room response over a larger area with widely spaced subs.

Whether both of us end up satisfied with the end result is completely unknown, but the exciting bit is that if we don't, then it'll be a case of DIYing something different.

Here, for the sake of it is the modeled maximum output from just one driver in a 75L cabinet at 1000w:

[IronGiant]

Dumb question No 1. What if you mount two drivers both facing out and swap the polarity of one of them over?

Dave

[Graham N]

Originally Posted by IronGiant

Dumb question No 1. What if you mount two drivers both facing out and swap the polarity of one of them over?

Dave

That is what I was thinking too

Graham

[Russell.Williams]

Originally Posted by IronGiant

Dumb question No 1. What if you mount two drivers both facing out and swap the polarity of one of them over?

Dave

They'll cancel each other out up to about the frequency who's half (or is it 1/8th?) wavelength equals the distance between the drivers and the cabinet will vibrate itself across the room. I stand to be corrected on the point at which they'll cease cancelling though. I seem to have woken up with a ZX Spectrum for a brain today. I can do colour or movement, but not both.

Russell

[IronGiant]

So they won't work as a push/pull arrangement then? I asked the question because I thought they might, with one going in as the other goes out, because of the polarity switch.

Dave

[jensK]

Originally Posted by m4rky_m4rk

I take it you have resorted to self build because there is no commercially available sub that can do what you want within a reasonable budget?

Why not an IB using the room upstairs

I am hoping to get a new house built with dedicated HC room. Cellars are very common here and no doubt I will have a cellar. It may be an ideal opportunity to go the IB route. The trouble is I know nothing about self build of subs. So the chat here may help me on my way in the learning curve.

Hi m4rky m4rk,

if you want to learn about self build speakers have a look at this forum. Visaton Diskussionsforum - Powered by vBulletin

Very educational if you are not from the trade (Holzwurm).

[gregmcquaid]

Russell,

At what point does the AV-15X hit it's excursion limit in this design?

[Moonfly]

Originally Posted by gregmcquaid

Russell,

At what point does the AV-15X hit it's excursion limit in this design?

IIRC, in this design, it keeps just within xmax at 10 hz

[Russell.Williams]

Xmax, that is the linear excursion limit is 23mm one way, or 46mm peak to peak. Xmech, mechanical excursion is, I believe about 4mm beyond in either direction and shouldn't be reached until well below 10Hz. In theory anyway.

Russell

[Russell.Williams]

Originally Posted by IronGiant

So they won't work as a push/pull arrangement then? I asked the question because I thought they might, with one going in as the other goes out, because of the polarity switch.

Dave

No, in a push-pull or a push-push they both travel out of the cabinet together and both travel in together ie, in phase. Its just that in the case of a push-pull as the polarity of one driver is physically inverted by mounting the driver the 'wrong' way round, it is restored to being acoustically in phase by wiring it out of phase.

Russell

[Moonfly]

Originally Posted by IronGiant

So they won't work as a push/pull arrangement then? I asked the question because I thought they might, with one going in as the other goes out, because of the polarity switch.

Dave

That doesnt work. With both drivers facing out both are doing the same thing so there is no cancellation effect, where one creates any even ordered harmonics (or odd if you read about, take your pic) the other simply does the same. With both facing out and one in opposite phase they are electrically and mechanically out of phase so cancel each other just as you front speakers would if they were out of phase. As one driver moves out the other moves in and for lack of a better word the 2 drivers will just bounce of each other.

In a push/pull the inward facing driver is electrically our of phase but mechanically in phase with the other (forward facing and on show) driver. As the main driver moves forward the bottom one pulls back on it using the sealed environment inside the cabinet, and because its actually moving backwards instead of forwards it restrains the top driver helping keep it away from its xmax, and in turn less movement means less distortion, especially as you try to drive the sub harder and lower. Any lost output due to the restraining action is made up for by having a second driver and applying plenty of power, and because both drivers are actually moving away from and towards the box together the 2 drivers dont cancel each other out. Again, while they are electrically out of phase, mechanically they are not, and thats whats important.

I'm taking a slightly different angle than Russ. I'm hoping to go deeper with a larger cabinet to make sure I dont loose what I love about the PBU. I'm going for an uber movies and music sub while I think Russell is chasing music even more than I am. My thinking is that the push pull arrangement will make up for any deficit against Russells direction musically. Its speculation though at this stage based on my experiences, theory, and the simulations Russell and I have run.

Hopefully Russell will be up for a comparison shootout with our finished products, which should give us plenty to talk about and some conclusions. I havent managed to find anyone anywhere that has built their own push/pull sub (not including kit builders) so its new territory to a degree and I'm looking forward to whatever is born

[IronGiant]

Originally Posted by Russell.Williams

No, in a push-pull or a push-push they both travel out of the cabinet together and both travel in together ie, in phase. Its just that in the case of a push-pull as the polarity of one driver is physically inverted by mounting the driver the 'wrong' way round, it is restored to being acoustically in phase by wiring it out of phase.

Russell

I think you need to hand me that Spectrum, Russell, once I've understood that I might have a chance of keeping up I'll bow to your superior knowledge on this one

Dave