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Old 10th November 2009, 10:37 PM   #1
walt2 is offline walt2  United States
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Default Sealed 15"....Overkill?

So, I have been toying around with a few sub ideas after building a pair of sealed Tritrixs. I was first looking into going for a cheaper 10" or 12", then was interested in the Dayton Reference 12"HF; and am now figuring that for just a bit more money, I could have a 15"HF (Parts-Express.com:*Dayton RSS390HF-4 15" Reference HF Subwoofer 4 Ohm | subwoofer rss390hf-4 15" subwoofer dayton reference rs sub dayton loudspeaker. I am planning to pair this with a BASH 300. Looking at building a 3-4 cuft sealed box (currently living in an apartment).

I am liking this idea because the 15" will leave me pleanty of room for expansion when I get a larger place in a couple years.

In a small ~12x15 room, would the 15" be overbearing/overpowering; or could I manage it to perform well with movies and music? Would I be better off with a smaller driver?

Opinions, ideas, and anything else you can throw at me!

Thanks!!
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Old 10th November 2009, 11:27 PM   #2
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I'd go with the 15
That particular one, in a 90 litre box (~3.5 square feet) will give good response down to 20Hz (f10) and easily handle in excess of 200 watts.
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Old 11th November 2009, 02:27 PM   #3
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With a Linkwitz circuit, you could make it get to 20Hz f3 (it has enough displacement and power handling...)

And there's no such thing as overkill - you can always turn it down. However, if you under-do it, you can't always turn it up.
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Old 11th November 2009, 02:32 PM   #4
AndrewT is offline AndrewT  Scotland
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go 15inch.
You can add a second 15inch later.
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Old 11th November 2009, 03:20 PM   #5
walt2 is offline walt2  United States
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Quote:
Originally Posted by chris661 View Post

And there's no such thing as overkill - you can always turn it down. However, if you under-do it, you can't always turn it up.
I like your style

I did not have time yeaterday to read much about the Linkwitz circuit info you gave me, but it looks interesting; I will read more into it tonight. Thanks again!!!
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Old 11th November 2009, 03:57 PM   #6
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This will help you out if you're interested.

ESP - The Linkwitz Transform Circuit

Chris
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Old 11th November 2009, 04:11 PM   #7
walt2 is offline walt2  United States
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Originally Posted by chris661 View Post
This will help you out if you're interested.

ESP - The Linkwitz Transform Circuit

Chris
Thank you, Chris.

This does look a little complex for a beginner like me. Is designing one of these easier than it looks? Have you been through the process?

I was also eyeing the Dayton 500w amp with eq. Would I realize a signifigant improvement for the extra $75? ( http://www.parts-express.com/pe/show...number=300-806)

Walt

Last edited by walt2; 11th November 2009 at 04:14 PM.
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Old 11th November 2009, 04:31 PM   #8
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An LT is on the complex side and I think you could do well enough without it. Having an amp with some EQ (as you linked to) would be a good substitute.
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Old 11th November 2009, 04:35 PM   #9
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Yes, I've been through it - it was my first serious project.

The idea is that your woofer will roll off at a frequency, at a rate of 12dB per octave. So, if we set a circuit where it increases amplifier output by 12dB per octave below the roll-off frequency, you can have flat response as low as you like. As it says on the site, the more gain you apply (ie, the lower you eq it to), the lower the maximum volume will be.
The circuit itself is fairly small, but will need a power supply (I just took it from the amplifier power supply), and you can go as low as you want.
If you want, I'll design the box etc for you, and give you the component values for the circuit.
The amp you just showed has eq that you wouldn't need, as you'd use you own.

If there's any specific bits you want me to simplify, let me know.

Chris
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Old 11th November 2009, 04:41 PM   #10
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Looks to me like this woofer is perfect for sealed with eq. on it's own, f3 of 30Hz (very respectable), most would be happy with this. This is in a 152L box, which isn't small.

If you wanted to go to 20Hz, you wouldn't need to put much extra power in (+8dB compared to the +14 I've used).

You could get away with a very small box here. 50L will be fine, just need more power.

What kind of SPLs will you be asking of this sub?

Last edit - try the attached spreadsheet. Put the Qts, Vas and Fs of the driver in, leave the desired Q at 0.7, tell it how low you want to go, in what box size, and it will work out how much gain you'll need, and the component values for the circuit.
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Last edited by chris661; 11th November 2009 at 04:47 PM.
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