What subwoofer should i buy and build? (specific)

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I have three "subwoofers" right now. I have two Genexxa GX1600 stone speakers from which I only have the 15" base drivers left, as the mids and tweeters were crap. The third one is an Alpine SWR 12D4, with a box tuned to maybe about 30hz.

I have a Sony STR-415DE (5x100W8Ohm) that powers these. The Genexxa "subs" claim to handle hundreds of watts, but start to distort and smell burnt with the 100 watts even with both of them wired in parallel in one channel. I have tried the Alpine using two channels to power it, getting maybe 300 watts total at 2x4Ohms, and it takes the power, but i don't get enough volume, nor low enough sound.

This is a home theater setup, but i do listen to a lot of music with it too. The room is just under 5m x 5m and the difference is maybe 10cm between the walls. Yes I know this is horrible, as the room is almost square, but it's my bedroom and i have my bed in one corner and a fireplace in another corner. I have my TV in the middle of the shorter wall (if I remember correctly) and my couch is just behind the middle line of the room (where my B&W dm602s3 sound the best).

As stated earlier, these three subs don't give me enough sound pressure in my smallish-medium sized room, thus I need a subwoofer(s) to get more sound, cleaner sound, and preferably a frequency range under 20hz.

My budget is very limited, maybe a couple of hundred euros, but I would want to get as good of a setup for as cheap as possible. I have place in one corner, under my table in the fourth corner and maybe at some wall or as a coffee table in front of the couch. If the sub(s) goes into the corner, it can be big, I mean the max space in one corner is about 100cm width, 90cm depth, ~250cm height.

What my research has given me was three somewhat good options:

Lilmike's LilWrecker - AVS Forum | Home Theater Discussions And Reviews

The first one was lilWrecker, a huge folded, trapped horn? Designed for as low frequencies and high dBs as possible. I would have space, I could maybe build it myself, but it would be costly and very heavy.

Dayton Audio RSS390HF-4 15" Reference HF Subwoofer 4 Ohm

The second is a dayton audio 15" sub that seems to have gotten a lot of good reviews, and can play low with a somewhat simple box that is maybe 200-300 liters big? It would play clean, but probably not as loud and it would maybe cost about the same, maybe a little lower.

The V.B.S.S. DIY subwoofer design thread - AVS Forum | Home Theater Discussions And Reviews

The third option I have found recommended was the V.B.S.S. 18" PA sub with equalization. It would make me buy an inuke NX3000D, but I think that I do otherwise also need more power than 100W, so this wouldn't be that bad. The pro's are: loud, low with equalization, small, doesn't weigh much, an decently cheap to even get multiple of them. The problem is that I can only find that speaker at parts-express and I live in Scandinavia, so shipping costs are a big consideration also.



I would like to get someone else's opinion on this, and maybe some other "cheap" solutions.
 
The Alpine can take 1000rms. You aren't getting anything like its potential from it.
Your receiver is a 6kg ab amp that is rated at 230 watt power consumption and the manual looks like the 100 watts is 'Peak power' with 40 watts for rears. I would imagine the Alpine (or any of the Dayton subs you have listed) can probably take all the power that receiver can muster on every channel, maybe even two of them.
The frequency response is also only listed at down to 30hz in the manual too which isn't going to help in you 20hz goal.
With 200 euro to play with maybe get an inuke second hand and some mdf to build a ported enclosure tuned to 20hz for the Alpine.
Soundimports are Daytons distributers in Europe. PA 460 for a vbss is about 170 euro and the RSS390HF is 270 Euro but your current amp wont power these drivers.
Look at the first graph on the lilwrecker link you posted and look at the different frequency responses to the watts input from the inuke nu3000 used. Most of the VBSS builds use inuke 3000 too.
Hope that helps a little
 
I'm a little confused about your setup. You say you have the 3 subs currently running off a Sony surround receiver. What are your other speakers (mains, center, surrounds?) and what is powering them? The Sony surround receiver does not seem like a very good solution for powering subs.
 
I'm actually going to second what has already been said in that the Alpine sub is already a bit of a beast and if you're having trouble with it then it's most certainly down to your box design, amplifier power or room placement.

I have attached two images that show simulations with the alpine driver. One is sealed, the other is vented.

Sealed the driver needs a very small box, no surprises there. This is ideally how it should be used in a car. A small sealed box plus cabin gain = decent bass extension without any necessary EQ.

In a home environment this is going to need a Linkwitz Transform circuit to equalise the bass to give you decent extension. A high pass, subsonic, filter is needed to protect the driver from excessive excursion at very low frequencies and to protect the amplifier from trying to put out loads of power at frequencies you cannot hear.

As you can see this requires a LOT of amplifier power. This is a dual 4 ohm voice coil driver and I have it configured as being driven by TWO amplifiers, one channel per voice coil. I did this because if you got a Behringer Inuke power amplifier you'd get two channels and that's how I'd recommend you use it so that the amplifier sees a 4 ohm load.

At the peak of the EQ curve and staying within the drivers linear excursion (peak to peak is how LspCAD displays it) the amplifiers are called upon to deliver 55VRMS. This is a lot. In terms of watts.

(55*55)/4 = 750 watts PER VOICE COIL. So 1500 watts in total to get you there. This driver is power hungry. 1500 watts into a 12" driver in a 10 litre box with 100% stuffing = a dead driver as there's no way you'll get the heat out of it.

Still to make this work you'd need a Behringer Inuke 3000 series for that kind of power. Luckily these aren't that expensive. You'll also need EQ. A miniDSP will do this for you, or the Inukes with DSP are supposed to be able to do this too. The filter parameters are shown in the simulation.

You'll get about 98dB at 20Hz. Not a lot, but not bad, with the sub placed in a corner, or at least along a wall it'll be quite nice.

Next is the ported version. This is a much better option in my opinion for many reasons.

The only down side is it needs a 60 litre box, which is quite a bit bigger, but nothing huge considering you have a decent sized room to put it in. 30% stuffing. Port tuned to 20Hz. The issue here is the port diameter vs port length. With an 8cm diameter port we're looking at a port that's 50cm long. Ideally you'd really want two of them but then they'd both be 1 meter long. Design your cabinet to suit. Maybe a slotted port would help here but don't design it incorrectly. Plastic ports/drain pipe will be a lot easier to build and modify to get the tuning frequency correct.

The upside is the bigger box with a port will have a very effective way of getting rid of the heat. I strongly recommend going ported.

This is an EBS alignment, or extended bass shelf. This means that the sub does NOT have a flat output down to 20Hz, or even 30Hz if you tune that low. It is, again, designed for in car use where the cabin will provide the bass boost that's needed for it to sound good.

Look at the amplifier power curves for both the sealed and ported designs. They are actually quite similar in shape. Both need similar amounts of EQ and both need a sub-sonic high pass filter to protect the driver and amplifier against really low stuff, otherwise it'll explode. The similarity in shape shows good driver design from the Alpine team as both the ported and sealed alignments will tune to flat inside a car.

The ported box needs a shelving filter of some sort to EQ the bass up. Again put it in a corner. Again it needs tons of power to reach the drivers limits, 1800 watts total this time. The 3000 inuke is perfectly suited to this. Use one channel per voice coil.

The ported box will give you about 103dB at 20Hz. In room this is a very respectable figure and will make explosions in movies boom like they should.

As you can see, not only is the Sony not up to the job of driving the Alpine, the Alpine (which is a good a very good sub driver if its specs are actually true) doesn't work well, sealed or ported, without EQ. Give it what it needs to work properly and it'll do fine.

So grab yourself an inuke + miniDSP. Or an Inuke with the inbuilt DSP, build a new box and have fun.

You can actually just have fun without building a new box. Plug the port on the box you've got and use it sealed with an inuke + DSP. This will sound good and may even be all you find you need. Then take your time building a new box.

You can theoretically go with a third design which is a sealed box that's a lot bigger. The extra size will reduce the amount of EQ and amplifier power that you need, but it will not go any louder. You'll still only get around 98dB at 20Hz.

I've added a 60 litre sealed design for the alpine. As you can see you still hit the drivers xmax limit at around 98dB, but this time it takes only 30VRMS to get there. This is 225 watts into each coil, or 450 in total. If you want to go sealed and have the space then this is what I would do. The driver will be able to cope with this amount of power and heat a lot more easily, the amplifier will also be happier and you'll get much less power compression.

Of course you can build whatever it is that GM linked, I'm not sure what program you're supposed to open that file with but it'll be a more complex design and probably need some delay? Although it does promise to go very loud!
 

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Weird Sony

The Alpine can take 1000rms. You aren't getting anything like its potential from it.
Your receiver is a 6kg ab amp that is rated at 230 watt power consumption and the manual looks like the 100 watts is 'Peak power' with 40 watts for rears. I would imagine the Alpine (or any of the Dayton subs you have listed) can probably take all the power that receiver can muster on every channel, maybe even two of them.
The frequency response is also only listed at down to 30hz in the manual too which isn't going to help in you 20hz goal.
With 200 euro to play with maybe get an inuke second hand and some mdf to build a ported enclosure tuned to 20hz for the Alpine.


http://sportsbil.com/sony/STR/STR-D/STR-D360Z_DE315_DE415.pdf

Weird that you found such specs. In this pdf it says 2x145w at 8ohm (20-20khz) peak and 2x190w at 40hm peak, which would mean maybe 300w rms total at 4ohm to the Alpines two voice coils. It is a very weird amp from my testing.

My main receiver is a Yamaha rx-v659 (7x100w or 2x120w at 8ohm). The Yamaha should be a more powerful amp from just looking at the power delivery, weight and specs. And the Yamaha can drive my speakers (90dB/W/M) pretty much as far that the tweeters start hurting my ears (somewhere at -3dB), and from what I have understood, you shouldn't go higher than 0dB on the amp. Well if I put my Genexxa subs, that are marketed to be 95dB/W/M, and input only bass frequencies, I can go to 0dB pretty effortlessly.

When i have the Genexxa's on the Sony amp, it seems to give much more power, I don't know how far I can or should screw the volume knob. I have tested this with other speakers also and I compared it against my fathers HK 990, a much more powerful amp, and the Sony "seemed" to give more power. I don't know if it's just something weird with the volume knob raising the volume too fast or what.

But yes, I should buy a bigger amp. The inuke NX300DSP is about 240€, which isn't bad. I just wonder, should i buy a miniDSP because it is 100€ and it would be cheaper to just get the DSP version of the inuke?
 
My setup:

- source: ASUS Xonar D2X soundcard through toslink 24bit 192khz
- main receiver for speakers: Yamaha RX-V659 (7x100w @8Ohm, 20-20khz, 0,06%THD)
- Yamaha sub out split into stereo for current sub amp: Sony STR415DE (2x100w @8ohm 20-20khz, 0,09 THD)
- Front speakers: B&W DM602 s3 with sturdy stands
- Center: KEF Q9c,(reason: it fit best under my TV, big enough, coaxial, cheap)
- Surround: Magnat vintage 110, (cheap, good sensitivity, they are in the corners)
- Surround back: 1 x KEF Q6c, my old center channel
- 2xGenexxa GX1600 stone with only woofers left, shut the mid and tweeter holes. (claimed 95dB/W/M, were free for me, got down to about 30hz, 20 hz claimed) They are in a corner 90 degrees from each other firing into the cornes, max air pressure in my room this way.
- Alpine SWR-12D4. I actually have it in my room, but I have planned to one day put it in a car, thus I would really not like to plan my setup for this. I can maybe build a new box or tune the old one better as it might be tuned to as high as 40hz, as long as it can still fit in a car.

I have tested many different configs with the subs so don't call me out for wiring them wrong.
 
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I have attached two images that show simulations with the alpine driver. One is sealed, the other is vented.

The response of the Alpine-based subwoofer isn't going to look much like that as the model you used does not include the impact of the semi-inductance parameters.

Attached is what the response (in red) of the Alpine 12D2 driver (the 2 ohms per coil version of the 12D4) in a sealed 35 liter box would look like, when the semi-inductance parameters are taken into consideration.
 

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