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Old 23rd January 2007, 08:00 PM   #1
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Question How To Build A Home Sub Box

Hi There All

Ive been looking into getting myself some bass boxes for my home system for some extra oomff ( and to block out the miss's moans , he he he ) . They do come at a price though so ive decided to try and build my own . I was hoping that i could get some help from all you professionals out there . The thing is , i have no idea of how big / small to make the box , to use a ported box or not Etc . I wont have a problem with the actual physical building of the unit/units . Its just the technical specs that i will be needing help .

Ive just bought myself a pair of brand new Italian made CIARE (HW203) 180 Watt BASS Speakers . They are 8 Ohms , Diam 200MM 8inch by 3 1/2 deep , sensitivity 92db , but thats about all the info i can make out as it is all in Italian .This link will show the full specs if you can make it out , http://www.ciare.com/pdf/catalogo/HW203.pdf . Will it be best to use them both in one box or make two seperate boxes . Will i be needing to use crossovers ? I will be using a 50 watt Rms per channel amplifer to run them , will this be enough power ?

The room ill be using the boxes in is roughly 13ft by 18ft . Any bits of advice will be much appreciated .

Thank You
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Old 24th January 2007, 05:10 AM   #2
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Hi Clapster,

I'm new here but let me try to address a few of the basics I can pick out and leave the specifics to others.

You can design the box using the program WinISD. Do a google search and download it, it is free. You will need the full set of speaker parameters from your link. It will give you the optimal box sizes for sealed / ported etc and the modeled frequency response.

Hooking these woofers up to your 50W amp will get you little in terms of sound. Low frequency requires high power and ideally they should be powered by their own amp. Take a look at this basic sub project for an example of a basic active subwoofer. http://diyaudioprojects.com/Speakers/MAW-10/MAW-10.htm.

There is tons of information on this website concerning ported vs sealed, power requirements etc. Search and I am sure you can find all the info you need.

Good luck!
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Old 24th January 2007, 11:01 AM   #3
bjorno is offline bjorno  Sweden
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Hi clapster,

Quote:
Will it be best to use them both in one box or make two seperate boxes .
In my opinion to build two of them is easier to place and thus more convenient.

Quote:
Will i be needing to use crossovers ? I will be using a 50 watt Rms per channel amplifer to run them , will this be enough power ?
Yes but not if driven by a separate amplifier and active filter which is the best and easier to implement.

Its also safer to use an amplifier that have a high pass filter built in to protect for high cone excursion rates at frequencies below 20 Hz, especially when the speakers will be equipped with drivers with low x-max as yours.

I believe 50W is quite adequate for each speaker but if enough? Only you can tell, it’s a matter of taste of SPL, which in this case will be about 108 dB SPL from each speaker, 114 dB SPL possible at maximum for both at the lower end.

With 20 dB SPL-headroom you can play at 94 dB SPL average and taken your room into consideration I believe this level is loud enough for most people.

b

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Old 24th January 2007, 11:03 AM   #4
bjorno is offline bjorno  Sweden
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Old 24th January 2007, 11:55 AM   #5
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The fairly low Qts indicates this driver is not suited to a sealed box. Because the excursion is not huge at 3mm a vented design will be needed anyway to provide assistance. The Vas and Qts values indicate the box will be a bit under 50 litres each.

You will probably find 50 watts is enough to power this sub especially if it's just for music, but you will need to make an active subwoofer (one that has its own amp and filter/crossover).
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Old 24th January 2007, 01:35 PM   #6
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Thanks Guys

Some good info there so ill have a good look into it .

Many Thanks
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Old 24th January 2007, 04:49 PM   #7
bjorno is offline bjorno  Sweden
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Hi,

FYI, I calculated the enclosure volume to a net 42.8 Litres but forgot to add the volumes of the driver itself, the port and of course the volume taken by the internal bracing.

The first two adds up to about 2.75 Litres and it's up to you to decide which internal bracing method to use and to determine the bracing volume after choosing the thickness of the ply/board type and so on.

I think a plate thickness of ¾” for the walls is adequate and to add simple cross-bracings that connects all internal sides, not forgetting the necessary volume saving openings cut-outs with aid of a router or saber saw etc.

This will add some proportional centimetres to all sides and change the gross volume of the enclosure.

Making the baffle twice the wall thickness is also recommended and allows an easy way to recess the driver.

I always glue ¼”-1/2” wool felt to all internal surfaces in reflex enclosures and trim the remaining ‘air volume’ with minimum of stuffing.

b
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