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Discussion Starter #1
Hi All,

I'm a new member and most interested in tapping what is evidently a great deal of expertise in all things audio. I am planning on building a downward firing, sealed sonotube subwoofer of approximately 1.8 cu.ft. with stuffing and using the Dayton RSS315-4 12in. driver and either the Dayton 240 or 500 watt plate amp. This will augment my Monitor RSI Sliver bookshelves and is for a music only system. Will the 500 watt be that much better than the 240 given that it has EQ but is $140 more? I'm not looking to rattle any windows but would like to get down to at least 32 Hz for an organ pedal note. WinISD generates an F3 of approximately 36 Hz and down 5db at 30Hz. Do I need a 3 in. gap for the speaker to endplate or could I go 2 in? My dimensions are all space constrained. The speaker will be placed in a corner of a 14X14X10 ft. room so don't know how much bass enhancement this will provide. This is my first diy subwoofer so would be pleased to hear any comments pro or con or any advice about my plan.
 

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Yellow is with a 240 watt amp maxed out to the point of clipping. Pink is with a O-Audio 500 watt amp with the Hi-Pass filter set at 20 hz and with the 4 db of boost at 20 hz that comes with it. The O-Audio amp would have 3 db of head room and would be a much better match for your needs.

The O-Audio amp is $229 with free shipping.

http://www.oaudio.com/500W_SUBAMP.html


amps.JPG
 

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Hi Mike,

Thanks for the input. I will reconsider the amp. I do like the 4db boost. I was considering the Dayton 240 watt amp with the 6db boost at 30 Hz but was concerned about introducing a bit of a boom or peak in the bass with no way to modify it. I presume you think this Bash amp is better than the Dayton 500 watt unit. What program did you use to chart the output? I am gung ho to get this going and will report on the building progress if you like.
 

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I mentioned the O-Audio amp due to its slightly lower cost, the Dayton 500 watt amp would perform just as well.

What program did you use to chart the output?
As stated above, the program is WinISD Pro. There is a tutorial on it here:

http://www.hometheatershack.com/forums/diy-subwoofers/6330-winisd-pro-tutorial-download-detailed-guide-how-use-winisd-pro.html

I am gung ho to get this going and will report on the building progress if you like.
Yes, please document your build with pics. It will be added to the "Subwoofer Database". :T
 

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Discussion Starter #8
Unfortunately had to delay starting my subwoofer incorporating the appreciated advice from this forum, but back in the saddle again. I am going with a 14 in. or 16 in. downward firing sealed sonotube, the 12 in. Dayton RSS HF315-4 and the Bash 500 watt amp. I have a 24 in. overall height limitation so looking at an approximate enclosure volume of between 25 and 40 liters subracting the caps and stand. In modelling with Win ISD I found virtually no difference in the frequency response between these two volumes. At 25 liters it is -3db at 37.5 Hz and -3db at 37.7. The same close results are the same at -2db and -4db. The shape of the curve does not change much. What am I doing wrong? There also does not seem to be any difference if the tube is flat and short or skinny and tall. Would sure appreciate some guidance.
 

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Discussion Starter #10
Hi Mike,

A Qtc of .7 in WinISD calls for a volume of 181 cu in. With a 12 in. sub driver how do you make an enclosure this small? I have read that a lower Qtc than .7 reduces low frequency output but putting in volume values higher than 181 at least up to 1500 cu in. flattens the curve and gives a higher output at lowest frequences. What am I doing wrong?
 

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Discussion Starter #13
Hi Mike and Steve,

Thanks for the replies. I am embarassed to say that my WinISD calculations were wrong. I had inputted Vas at 3.0 (for cu.ft.) not noticing that the box was labelled liters. So much for what was wrong. Understand now that to get a Qtc of .7 I would need an 80 to 85 liter volume but unfortunately I am constrained to a bit over 60 liters which should give me a Qtc of about .75. Thanks again for your help. I will be ordering the raw materials this week and hope to get the project back on track.
 
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