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Discussion Starter · #1 ·
I am looking to build a smallish subwoofer for a HT application. Right now, I'm thinking about using a Shiva-X as the driver. Sub-20Hz extension is nice, but not necessary, and I'm going to try really hard not to exceed $500 for the total budget.


Right now I have a pair of Swan Diva 6.1s as mains, and some old Technics towers in the back hooked up to an AVR-247 (crossovers at 40, 60, 80, 100, 120, or 150). I am planning on using a 60Hz crossover, but that's not a given. I may swap out the 6.1s (due to size) for something smaller. I am planning on building a down-firing subwoofer.


Primary WAF factor in this project is size/footprint of the sub.


Here's where I have a few possibilities:

1) Sealed subwoofer with some equalization, plausibly using the O-Audio BASH 500W amp. I'm a little unsure how to read the power graph in the owners manual regarding the boost/subsonic filter and apply the results to the frequency response graph generated by WinISD.


2) Ported subwoofer. Obviously these are going to be larger. I've gathered that large (and unfortunately long) ports are a good idea, and I've strongly considered a Easy-button style design (though smaller). Are there any issues with pointing the driver and the port downward? I would probably use a lower-rated/cheaper amp if I went this route.


I've seen a number of pictures of interior baffles in ported subs -- a circle the size of the driver cut out of a piece that spans the interior. Obviously this is how a lot of people do their bracing, but does this serve another purpose?


Are there other drivers I should consider for a smallish sub? Losing total output would be an acceptable trade-off, but I'm less inclined to lose bass extension.


My woodworking skills and tools are moderate. I am planning on using 3/4" plywood, and covering in veneer and glossy finish.
 

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I too, am dealing with maximizing bass/ footprint.


I am giving a passive radiator design the next shot. If that fails to please ny internal bass gods, a sealed maelstrom.


Hopefully the passive idea will work out for me....
 

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What exactly do you consider small? Would 18 x 18 x36 work? The dayton 385 in a 6.75 cube ported box is very popular here. Its only $128 for the driver and last I checked the 240w PE plate amp was only $115. Its a pretty decent combo. With the right port it pulls hard down to 20hz.
 

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Discussion Starter · #4 ·
After consulting with the wife, 18x18x36 is indeed acceptable.


After having done some power modeling in WinISD, I'm thinking that 250W is plenty of juice, but I'm still leaning toward the Shiva. Given the lack of equalization, I'm leaning toward a ported sub. In particular in interior volume of around 5 to 5.5 ft^3 and a port tune of around 20Hz. Does the Dayton 240W sub amp have a subsonic filter of an appropriate frequency (WinISD predicts cone excursion problems at around 15Hz without a subsonic filter)?


It rather looks like I'll be building something in between the two ported sub designs in the application notes on the Shiva driver. Will a 4" port still be sufficient, or should I attempt to increase to a 5" (by 21.5" first port resonance at 315Hz) or something else?




I'm still curious about the purpose of the interior baffles.


When measuring the length of a port with a flare, what is considered the end?



Edit: The Rhythmik DS1200 for essentially the same price as the Shiva-X seems to model more or less the same as each other in WinISD. Are there any features to recommend one over the other?
 

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If you are considerring the Rythmik, you want the servo kit. This will give you decent output down to 14 Hz from an 18" cube. They have two versions, one with a larger amp (370 watts) is $569, the 300 watt version requires a slightly larger cabinet but is $80 less. This is a very good subwoofer.


Regards,


Dennis
 

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The ShivaX sealed in 120L and the Oaudio 500w amp are a great match. Setting the subsonic filter to 17hz controls excursion nicely and the PeQ will give you some boost in the 20-30hz area if you need it.Combined with Room gain may be enough to bring this sub close to flat to 25Hz. Here's some modeled graphs from unibox. Both show the Oaudio at 80hz low pass and 17hz subsonic setting.

Attachment 130137

Attachment 130138

 

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Discussion Starter · #7 ·
I've decided on a sealed shiva-x build using a EP1500. I am strongly considering using 3/4" bamboo plywood for the shell, which is available to me for around $150 per sheet, and it seems like less work than learning how to veneer. I'm planning on bracing every 12" or so and making a 15"x15"x45" (or shorter) down-firing subwoofer.


Are there any concerns with using bamboo as opposed to more conventional (high-quality) plywoods or MDF in a subwoofer? In a bookshelf?


What I've read recommends a higher Q for HT use than for critical listening, but all I can see is that a lower Q extends the FR at the cost of power handling (and increased size). Is there something else that I'm missing?
 

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Discussion Starter · #8 ·
I've been done for a while, but I've neglected to post pictures due to laziness. Finishing my recession buster speakers has motivated me to post these pictures as well.


I ended up buying a gorgeous 1947 RCA Victrola cabinet to put the subwoofer and HT electronics in, so space was small. We ended up with around 1.8 cu. ft. (plus a couple pounds of stuffing). It sounds great, and fits in the space -- effectively looking great. Since we were putting it in a cabinet, I decided to go cheap and make it with MDF.


Here's a few photos:





It's hiding behind the green velvet in that last photo.
 

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Discussion Starter · #10 ·
I like it. Not that I have much to compare to. It seems clear and clean. Due to its small size and the fact that it's sealed, it doesn't go tremendously low, but what I've heard sounds pretty good.
 
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