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Old 15th January 2005, 01:00 PM   #1
klud is offline klud  Denmark
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Default my first sub.

hi i need help. im 17 years old from denmark i want to build my first subwoofer, but i need advice. first of all i have 2 peerless xls 10" woofers that i got cheep from a friend for about 180 english pounds. they are all new and in boxes.
but how should i build it? sealed? vented? i dont know.
and how big a cabbinet? what is the best option?
i thought about using a thommesen Proteus 2.5 amp. is that a good idea?

thanks. henrik from denmark.
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Old 15th January 2005, 04:31 PM   #2
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Well you have yo ask yourself what you want. First you have to find a place you are willing to give up to your subwoofer. Placement is a big issue. Though (for the most part) bass frequincies can not be oriented as to where they came from inside an enclosed room Corner placement will give large boomy bass, center of a bountry will genrally give the flattest curve in the center of the room and as close to the center of the room as possible will generally give the flattest overall responce.

3/4" (around 2cm) MDF (Mid-Density-Fiberbooard) is generally the cheapest and easyest to construct with. it works great because of its high density compared to most other sheet woods. Above that Marien Grade Plywood would be the choice. but it is expensive, a pain to work with, and lb to lb doesnt offer that great of an improvement over MDF. Also Hardwood can be used since i am asumeing this is going to be used as a home audio subwoofer, and since in most houses (most) tempature and humidity stay relatively flat so warping shoudlnt be a problem; and hard wood is the most dense that i know of personally (if you dont know what hard wood is it is sheets of solid wood such as oak or cypress. Plywood is made up of thin sheets glued togather, they are not the same. on top of that most plywood here in america is White slash pine, not the most dense of woods. Marine grade is good because it will not warp and is fairly dense compared to regular plywood).

Generally Ported is the best way to go. It can give the flattest low end extension (with low tuning) or the largest SPL peaks (with high tuning). It will always be louder than sealed all other things being the same above the enclosures tuning. Some say ported is too boomy or they can hear the port making noise. if it is properly constructed the SQ is compareable to that of a sealed enclosure. Proper port area is the key to keeping that "windy" noise away and rounding off all sharp edges inside the enclosure and especailly around the port (where airflow is most prevelant) will keep away any whistles.

There are dozens of how to's on the net, search around. JLaudio.com has the formula for port tuning, or if you are to lazy Audiobahn.com has a suprisingly accurate port calulator. all you have to do is enter in what type of port you are using, what the net displacement of the enclsorue is, what tuning you want and what the port area is and it tells you how long to make the port.
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Old 17th January 2005, 01:01 AM   #3
simon5 is offline simon5  Canada
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For the cabinet, bigger is usually better, but then you must know how big you can go.
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Old 17th January 2005, 10:05 AM   #4
keyser is offline keyser  Netherlands
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for a first project, imo building a closed sub would be the best way to go. closed subwoofers are easiest to build, and not as critical in calculations as a ported sub.
although ported subs do usually go louder and a bit deeper, ported designs will give you a more linear inroom output (the low-order roll-off is equalized by the effect the room has on deep bass).

simon suggests building your sub as big as possible. if your main target is to build a musical sounding sub, he is right. Building a smaller sub will give your sub a more boomy sound, with more ouput over a smaller bandwidth. some find this nice for movies.

good luck with those 2 nice drivers!

(also check diysubwoofers.com)
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Old 17th January 2005, 10:55 AM   #5
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Do a search on this forum. You will find a few designs using those drivers.

With these drivers larger the better is most definitely NOT true as they have low Qts. Unless you go for the dedicated passive radiator for these, a sealed box is best. I posted a rough design on here a while ago.
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Old 17th January 2005, 04:52 PM   #6
simon5 is offline simon5  Canada
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Why it's not true? The rolloff is much better with a bigger box.

We also need to know if it's the Peerless XLS 10 car version or home version... the Qts is not the same.
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Old 17th January 2005, 06:22 PM   #7
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In a nutshell, the low Qts of the XLS10 (home version) combined with fairly small Vas means that if you use a sealed box you are getting into very low Qtc but also F3 is relatively high. If you go for an assisted design then you will not be able to accomodate the vent because the box is too small. As you increase box size to try and accomodate the vent or just for fun, the response becomes very droopy, power handling and step response is worsened. They need a passive radiator.
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Old 17th January 2005, 09:43 PM   #8
simon5 is offline simon5  Canada
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I liked the FR curve of the XLS10 in a 150L box, but if you say that the step response is not good ?

It's like if it was an infinite baffle, no?
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Old 17th January 2005, 10:16 PM   #9
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If it's a closed then the step response will be fantastic. Vented will be not so good.

In both cases, excursion-limited power handling will be vastly down on what it's capable of.
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Old 17th January 2005, 10:28 PM   #10
simon5 is offline simon5  Canada
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Yes, I was talking about big closed boxes. I know that if you build a big vented box, you need to tune it way lower.

Power handling is down, so price comes down for the same SPL level...
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