# Adding sub-bass



## theredraven (Feb 25, 2010)

Hello!

I am a civil engineer at Michigan State University and currently my setup consists of these components:

-BIC RtR-EV15 15" Biampable Floor Speaker x2
-Denon AVR-3803
-Some smaller bookshelf speakers I will be using for surround.

I am looking to add some dedicated sub-bass to my setup. I already have a Hifonics BRZ15D4 that I took out of my car and want to incorporate into my living room.

The current plan is to build a 12ft^3 box (new coffee table) tuned to 27Hz, and power it with one of these amps.

What do you guys think? Will the huge box size be a problem (I did make it in WinISD)? I think the 300W RMS should be enough on the sub in a box this big, and according to the decibel ratings from WinISD I should be hitting about 118dB right in the perfect range for me (27hz-34Hz).

Update: Talked to a tech guy at Hifonics, and he said it could either be a hit or miss really. I think I'll go for it! Any opinions?


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## qwertydude (Dec 22, 2008)

Since space isn't an issue and you can go ported you'll be better served with a more efficient driver. You'll reap far more rewards with less power and have a more musical and accurate sub. Considering it looks like with the selection of those giant towers you're listening to music rather than home theater you'll be better served with a more efficient subwoofer. Car subwoofers generally sacrifice efficiency to be able to run in small boxes and thus need higher Xmax, I doubt the Hifonics is a real 96 db efficiency like the specs say, maybe if taking into account cabin gain in a car. Plus that Hifonics sub is dual 4 ohm which is incompatible with that plate amp you listed unless you wanna cut your power in half by running 8 ohm. The amp produces max power at 4 ohms.

Remember 3 db's of efficiency gain is equivalent to doubling your input power. So you need a better woofer.

With that said, nice thing is, Parts Express has both things you'll need.

Bash 300W Digital Subwoofer Amplifier 300-750
Dayton Audio DCS450-4 18" Classic Subwoofer 4 Ohm 295-475

An 18" woofer will be plenty of air moving capability even with less Xmax and generally woofers like this are more efficient and in the right box won't even need to use all their Xmax.

As for box, well you've got the software should be pretty simple to plug and chug.


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## theredraven (Feb 25, 2010)

qwertydude said:


> Since space isn't an issue and you can go ported you'll be better served with a more efficient driver. You'll reap far more rewards with less power and have a more musical and accurate sub. Considering it looks like with the selection of those giant towers you're listening to music rather than home theater you'll be better served with a more efficient subwoofer. Car subwoofers generally sacrifice efficiency to be able to run in small boxes and thus need higher Xmax, I doubt the Hifonics is a real 96 db efficiency like the specs say, maybe if taking into account cabin gain in a car. Plus that Hifonics sub is dual 4 ohm which is incompatible with that plate amp you listed unless you wanna cut your power in half by running 8 ohm. The amp produces max power at 4 ohms.
> 
> Remember 3 db's of efficiency gain is equivalent to doubling your input power. So you need a better woofer.
> 
> ...


I feel stupid, I don't know how I didn't notice that I wouldn't be able to hook that sub up to the 300W bash. I might buy a Crown XLS 1000 for $300 instead of a new sub/amp for $300, just so I can open up my system and have some headroom for later on down the line. With the Crown I could power my current sub in a new box just temporarily and power my tower speakers, and then decide later if I want to run two subs from the amp or not.


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## MarkZ (Dec 5, 2005)

Just power one of the Hifonics coils and short the other terminal. Then grab that Bash amp. It will save you a few dollars in comparison to the Crown, and will allow you to build it into the box.


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## theredraven (Feb 25, 2010)

MarkZ said:


> Just power one of the Hifonics coils and short the other terminal. Then grab that Bash amp. It will save you a few dollars in comparison to the Crown, and will allow you to build it into the box.


How would I go about shorting the other terminal? And doesn't that affect the subwoofer's performance? I'm not too familiar with doing work on the actual speaker itself.

I really do like this idea a lot though, it enables me to pick up a more efficient driver later on down the line when I have $


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## MarkZ (Dec 5, 2005)

By "short", I mean that you simply connect the + and - of the unused coil's terminals together. You hook the amplifier up to the other coil in the usual way.

Driving one coil doesn't affect the subwoofer's performance in any appreciable way (some argue that it reduces power handling, but I don't really buy that...). If you left it open instead of shorting it, it would alter the speaker's parameters -- not necessarily in a bad way. Just different. You could try it both ways and go with whichever sounds better in your application.


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## theredraven (Feb 25, 2010)

MarkZ said:


> By "short", I mean that you simply connect the + and - of the unused coil's terminals together. You hook the amplifier up to the other coil in the usual way.
> 
> Driving one coil doesn't affect the subwoofer's performance in any appreciable way (some argue that it reduces power handling, but I don't really buy that...). If you left it open instead of shorting it, it would alter the speaker's parameters -- not necessarily in a bad way. Just different. You could try it both ways and go with whichever sounds better in your application.


Ohh okay, so arguably the point of having multiple voice coils is to enable the sub to be hooked up to the amp with different ohm loads. I'll let everyone know how the sub sounds when I get the amp and build the new box.

The box I have it in currently is a sealed box that's about 3ft^3, its running on 100W RMS (20% of max power), and it still makes everything vibrate in the apartment complex 3 floors up. This is obviously not enough SPL though. 

300W RMS (Bash amp), with a 12ft^3 box (new coffee table) tuned to 27Hz is the plan. According to winISD this gives me 118dB from about 27Hz-35Hz, perfect for my electronic/dance/hip-hop/trap tastes lol.


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## cubdenno (Nov 10, 2007)

Give a look at using a Fitzmaurice design like a tuba HT. I am not sure if your woofer will work but I wouldn't hesitate to try it. The tuba HT is amazing. Low end extension <20 hertz falls off but can easily do ~120db at the LP in my family room. 

Tuba HT


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## theredraven (Feb 25, 2010)

cubdenno said:


> Give a look at using a Fitzmaurice design like a tuba HT. I am not sure if your woofer will work but I wouldn't hesitate to try it. The tuba HT is amazing. Low end extension <20 hertz falls off but can easily do ~120db at the LP in my family room.
> 
> Tuba HT


That looks like an amazing design, I just currently don't have that many tools available to me at my apartment at school. And I must admit, I'm not sure I even have the woodworking skills right now to do that. But that is definitely something that I will have to attempt in the future.


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