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Old 13th December 2005, 04:44 PM   #1
Jacobus is offline Jacobus  Netherlands
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Default subwoofer questions

Hi All,

I'm planning to build a subwoofer in the near future, and as I'm not very technical I would like to buy a kit or build a diy project which already had good feedback.

I'm going to use the sub only for music in a room of about 32m2 (about 25feet long and 15feet wide if I calculated correctly). As I'm living in the Netherlands it can be a hassle to get drivers from the US (If there is somebody here from europe that knows where I can order drivers e.g. like dayton, adire please let me know). Anyway I first need to make the choice of a ported box or sealed box. some people say a ported box is not as good as a sealed box for music, some people say a ported box can be as good for music as a sealed on.

* The Alcone sub 12, is a kit what is readily available in europe and had very good reviews, but it is a ported box

* the directservo sub from rhythmik also has great reviews but I have to import it, which will be a hassle prob.

* Also peerless drivers are regarded very highly and are available in europe, does anybody knows a good design with e.g. the new xxls drivers in a sealed box?

so, does somebody can answer me the question about ported or sealed. Does anyone have expierence with the Alcone sub 12? does anyone knows good peerless sealed box designs? or any other designs which are obtainable in europe. And last but not least, is the directdervo sub so good that it is worth to import it? :-)

cheers,

Jacob
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Old 13th December 2005, 07:28 PM   #2
e-side is offline e-side  Netherlands
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I don't have any experience with the systems you mentioned, but I could tell you something about the choice for a ported or a sealed system.

A sealed or closed system will produce accurate and clean, tight bas. This type of enclosure can handle very low frequencies, without a massive excursion. Disadvantages are the low efficiency and the higher frequency resonance of the driver (there won't be very much bas below resonance).

A ported system will produce deeper bas, and it's more efficient (about 3 dB more SPL) than a sealed box. However, it's less accurate and below the tuning frequency the driver will have a high excursion, so you have to use a subsonic filter to prevent the driver exceeding his maximum excursion. Incorrect tuning will result in boomy bas.

Which type of enclosure you choose is a matter of taste, and the purposes of the system. In your case, when you only listen to music (don't know what genre, however), I would prefer a sealed system (but that's my opinion...).

regards

Erwin
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Old 13th December 2005, 09:41 PM   #3
simon5 is offline simon5  Canada
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I disagree, a well built ported box is usually more accurate, less distortion, less excursion (except under tuning).

That's a big debate anyway hehe!

Since you're in Europe, the XLS or XXLS line is a good choice. It seems you want to go sealed, so it's even easier. Build a nice well braced box , size don't matter much, put the driver in with a plate amplifier and you're done.
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Old 14th December 2005, 12:13 AM   #4
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To build an "accurate" ported subwoofer, you'll generally have to build it larger than the equivalent sealed box.

Then what e-side says is correct, the ported box will be more efficient, and the frequency response will be 'flatter' down to Fb (tuning frequency), while the sealed box will generally be rolling off gently. The sealed box will have increasing cone excursion down to this point, while the ported box will have decreasing excursion down to Fb.

Below this point, the frequency response of the ported box drops like a stone, and the cone excursion increases expotentially. If this isn't controlled by electronics, then this causes increased distortion over the whole range, if it is controlled, then the electronics may cause distortion by the steepness of their cut-off. The sealed box still is gently rolling off at this point with increasing excursion - noting that in most rooms, this is 'boosted' by increasing inroom response.

If you build a small sealed box, then you'll get a peaked response and faster roll-off.

Edit: That's not to say that e-side was incorrect, by the way.
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Old 14th December 2005, 09:23 AM   #5
Jacobus is offline Jacobus  Netherlands
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Hi,

Thanks for the answers so far.

my music choise is very very broad, jazz, singer songwriter, dance, rock..you name it. I do not have a pref. for closed or ported as for me it is not clear which is better, and the answers on my question so far also indicates that there is a debate about this. I only now that a ported design has a flat respons and a sealed gently goes down in SPL level. So I guess I has to be flattened ? Will it be that easy, just throw in a peerless driver in a closed box? tune it to about 30hz or so, what about flattening the SPL?.

I just want a sub that gives the best sound when it comes to music, I guess that would be a sub with the least distortion, most flat SPL. but maybe I'm wrong. I'm willing to spend 500$ max for driver + plate amp.(size 100liters or smaller) It will be used for mono. I hope I will get some more answers, in the mean time I will take a look at the suggested SEAS driver and Peerless drivers, and I will try to get more info on the ALCONE SUB 12, ported design (which is protected from over excursion, in what way will this influence the sound this elec. protection? I guess that if it is noticable it will only be there where the correction kicks in)

Thanks guys,

Jacob
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Old 14th December 2005, 10:41 AM   #6
Jacobus is offline Jacobus  Netherlands
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By the way,

What about room gain, a sealed sub shows a gradual drop in SPL, will this be corrected by room gain so that you end up with a flat response. if this is the case than a flat SPL of a vented box will have a rise in SPL? this is not wanted, or am I wrong? aaaargggghhh...so much questions, so little technical knowedge in my head

Jacob
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Old 14th December 2005, 07:22 PM   #7
simon5 is offline simon5  Canada
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The gradual drop in SPL is not totally corrected by room gain usually unless your room is really well sealed, build with very rigid walls, with no doors nor windows.

Sealed drop at 6 dB per octave, room gain will remove about 3 dB so you're left with a 3 dB drop. With a ported enclosure, you design it to drop by 3 dB per octave, so room gain bring it back to flat. You can also design it flat, so yes it will rise if you do that.

But there's problems with ported too, if you want a small box, it's hard to tune low without port noise. If it's tuned too high, you might hear the group delay too.
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Old 14th December 2005, 07:45 PM   #8
dscline is offline dscline  United States
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Keep in mind too that if you do some type of electronic compensation, such as a Linkwitz transform circuit or servo feedback, you aren't limited to the "standard" 6db rolloff of a sealed system. The Rythmik servo, for example, is only 3db down @ 14hz.
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Old 14th December 2005, 11:56 PM   #9
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Whichever way you go, think about making 2. Not for stereo, as such (although you can do this), but because there's no substitute for square inches (in cone area). Really, there's no substitute for cubic inches (in box volume) either - building the box as large as you can aesthitically can afford will generally give a better result.
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Old 15th December 2005, 12:05 PM   #10
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There really is no definitive answer to the question "which is better - sealed or vented?"

Its a subject of much debate with experts who prefer vented and experts who prefer sealed.

You really have to look into it and make your own choice.

You can design a vented sub for music only but if you have a brick room with lots of gain then you need to take that into account to avoid boomy exaggerated bottom end. The advantage you get from a vented box is gained mostly below 40 Hz, hence most music won't gain that much.

If you go with a sealed Peerless XLS for music with a decent plate amp you should be on the right track.

For my own use I prefer vented since for home theatre use below 40 Hz one vented sub equals two sealed subs, but for music this is not the case and a sealed sub is easier to build and get it sounding "tight."
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