Dipole subwoofer only for music???

[jerusalem]

Hello, it seems that i will need soon subwoofer for my new setup, as im goin to move finally at my own student apartment (30m2 concrete block, yeah i know...).but anyway, the idea is to have 2 bookshelf speakers on stands + subwoofer trough feedback destroyer, so as the room acoustic will be "not so good" even after some acoustic treatment, what type of subwoofer to make?

The room will be small (15m2 propably) and it will be purely for music, i think i dont need bass extension lover than around 35-30hz, (room gain will propably add up some after that) and no extremely volumes.

What do you think about making an dipole subwoofer? Does it work better in my room compared to closed subwoofer? I would like to make this "high end" project where quality of sound is most important, so it can use expensive parts if needed.

Suqqestions anyone? What drivers to use, links, other options? Help the confused noobie, thank you!

[ThomasW]

Having used a dipole sub I can tell you they sound fantastic. I can also tell you you'll need a ton of drivers and EQ to get adequate output even in a small room. Room gain doesn't fill-in for the losses involved with a dipole sub.

My suggestion is you build a low "Q" sealed box. It won't have the ultimate sound quality, but it will be a lot cheape, smaller and much more portable.

[Mazeroth]

It depends on what kind of volume you're looking to get out of the sub and how large you're able to build it. Give us some dimensions of how big the box can be and how many dB you're looking to obtain from it, from x meters away.

I did tests with a single 12" in a U-frame, and at 85dB in level at 3 meters it was doable, down to about 35hz. Granted, this was a very large U-frame for that 12", but I was only crossing it at 80hz to my mains so it was ok.

If you're looking for a decent amount of output then I'd highly recommend what Thomas suggests. Build a sealed sub in as large of an enclosure as you can tolerate. The closer you can get to an IB alignment the better. The box can NEVER be too big! :B

[jerusalem]

I think i can live with 35hz, 3 meters are just right for distance, 85-90db will be allright too. "Box" (or frame?) size could be 18" x 18" x 20", or 2 boxes with: 15" x 15" x 17"

I don't know has one to cross dipole differently, but speakers would do around 50 hz so i quess you can calculate it from there

Something like that, propably used as standmouts for speakers, or 1 big box at corner of the room.

[jerusalem]

Oh yes, some kind of different frames, H, W, ripole (i barely know what these mean) would be allright too, if used as speakermounts they can be high to the point of 30"

[ThomasW]

35Hz is a woofer not a subwoofer, what main speakers are you using?

Ripol is 1/2 a "W" frame design.

http://www.lautsprechershop.de/hifi/index_en.htm?/hifi/ripol_en.htm

Linkwitz uses "W" frame woofer in his Phoenix design, (note that he uses a sealed box sub with them

http://www.linkwitzlab.com/woofer.htm

Linkwitz also has "H" frame designs

http://www.linkwitzlab.com/woofer.htm

[jerusalem]

Actually not anything yet (in this system),i'm looking here for a subwoofer to pair next speaker, i'm building it right now:

http://www.troelsgravesen.dk/W15.htm

So as i undrestood, it should be around 45-50 hz

As troels says it in second version with fountec neo3 ribbon:

http://www.troelsgravesen.dk/W15_Neo3.htm

"
The easiest way to try out the Neos was to set up a small monitor and the SEAS W15CY001 midbass was an obvious choice. You don't find a much better upper midrange and from a 7.5 litres cabinet you get a surprisingly deep bass. I also tried adding a subwoofer from two push-push Dynaudio 21W54s with a crossover around 60-70 Hz/12 dB and it worked fine. The W15s were run fulrange and this obviously sets a limit to loudness but it all performed well up to relatively high levels."

So i think trying similar approach, a pair of subs but with dipole bass. Now if it doesn't work at the end, i can allways throw away or burn those dipole frames and just remake drivers + amplifier, to be a sealed box subs, right?

I thought about using peerless xls line woofer, other brands very easily acquired are at least vifa and seas, but i quess any importing tc2+, dayton reference series or something from adire/ascent audio would do (altought it would cost $$$ to ship them)

But if it is costeffective to use peerless, i should just go for it? Or use 15" x 2 instead of 12" x 2?

[ThomasW]

Linkwitz is the resource for this kind of project. He as a spreadsheet to calculate Max spl when a driver is mounted in a monopole or dipole configuration.

http://www.linkwitzlab.com/spl_max1.xls

I run true IB subs (driver's rearwave vents into a space behind a wall or other barrier in the house). With IB subs I've found that one needs no less than 4 times more displacement compared to that needed for a standard box. When I experimented with a dipole sub instead of the IB, I found that 6-8 times more displacement was needed when compared to a standard box design. So the dipole needed almost double the displacement of the IB to maintain the same output.

To keep things in perspective understand that my idea of a sub is something that has respectable output to 20Hz or lower.

Yes if you choose the correct drivers they can be put in any 'portable' box. Just don't make the mistake of using a driver with a Qts of 0.69 (sort of a standard "Q" for open baffle operation) and plan on it working well in a regular 'box' should it prove ineffective in a dipole.

My recommedation would be to get drivers with a "Q" close to 0.5. Those will work fine in either a dipole or a standard 'box'.

Also it's important to understand that in a standard box sub the output of driver is limited by the thermal heating of the voice coil. In a dipole the output is limited by the excursion limits of the suspension. So the power handling of a dipole is less than 1/2 that of the same driver if it's in a box.

[jerusalem]

Thanks Thomas, i think Peerles SLS12 might work as ripole pair nicely, they said SLS series 8" 10" 12" might be one of the best drivers at least here in europe for this kind of setup. Besides i heard that a sub made out of SLS10 was better at music in a close box, when compared to xls-12 in a closed box, althought offcourse didn't play as deep but what played was integrated to mains very nicely.

SLS10, QTS 0.51 and for SLS12, QTS 0.47

http://www.tymphany.com/datasheet/printview.php?id=38

http://www.tymphany.com/datasheet/printview.php?id=37

4-Drivers, 2 at each box in a ripole confiquration, like they do at audioelevation http://www.audioelevation.de/attac_400.htm

Any critique of this choise before i pull the trigger and start building?

[ThomasW]

Personally I wouldn't use a driver that has 8mm of Xmax in this application. The suspension travel is all one has in a dipole, so the longer the travel the better.

My suggestion is use something that has no less than +/-14mm Xmax, and double that is better yet.

Look around at some car audio drivers to see if you can't find something that might work.

[jerusalem]

Car audio drivers 8O Is there something i have missed, or does dipole subwoofer work somehow fundamentally differently that usual ported or box subwoofer?

i just mean that putting an car-audio subwoofer at home doesn't sound too good idea, or do you just mean that if in my area only subwoofers easily attained with high xmax are car-audio subwoofers, i should consider then those?

They really do say that SLS10 is very good for dipole, but your explonation is believable and i know that you know your business, so why would they actually then tell you that SLS is one of the best? Might it have something to do with, that SLS is cheap 80e, where peerless XLS is 160e, so you can use double amount of drivers for the same money with SLS?

So as space is limiting factor like with my situation, then 4 high xmax 12" drivers are sensible way in this situation?

[ThomasW]

I'm sure the SLS are good drivers. And 8mm is probably fine if you're making a ported box. But IMO it's pretty much a joke for a dipole subwoofer. Unless you use a highpass filter the voice coil former will slam into the backplate with the first loud bass passage. Then you have a new collection of paperweights.

Understand that a good driver is a good driver. It's target audience, car or home, doesn't matter. Now I'm not saying that all car woofers are good. The vast majority of them are terrible for home use. But there are some that can work fine in your application. So yes it depends on what brands and models you have available.

What I'm saying is don't limit your options. Look around and see what higher excursion 12" drivers are available. Car or home, it doesn't matter as long as the drivers are 'good'.

[Dennis H]

From what I've heard, the SLS is a good candidate for a dipole midwoofer on a flat baffle, say from 50-60 Hz up to 200-300 Hz. It has better HF extension than most sub drivers. But, as Thomas says, there's not enough Xmax for sub duties. As well, the "ripole" config is going to limit you to 80-100 Hz on the high end because of the severe cavity resonance of the narrow slot so the SLS's HF extension will be wasted. It's simply a case of not matching the driver to the task at hand. The XLS or XXLS will work much better to fill in the bottom octaves. Hey, the XLS is good enough for Mr. Linkwitz so it can't be all bad.