First HT DIY sub, need help

[bmwking]

Hey everyone,

So I'm going to be building my first sub enclosure for my living room and I need some help with the dimensions and port. I'll be using 4 Infinity 860w 8" subs and powering them with a iNuke1000DSP. I have the TSPs of the subs below to help. I just need your help when it comes to calculating box size and port tuning/size. My goal is to make this as versatile as possible for both movies and music, now I won't be listening to any 8hz organ blasts so don't count that. but from what I gather, I'll need it to be able to extend down low with impact for movies. I hope you can help me out

TSPs from :

Re = 3.4546 ohms
Fs = 31.7902 Hz
Zmax = 39.8661 ohms
Qes = 0.4760
Qms = 5.0175
Qts = 0.4348
Le = 2.9342 mH (at 1 kHz)
Diam = 150.6750 mm ( 5.9321 in )
Sd =17830.8599 mm^2( 27.6379 in^2)
Vas = 9.9025 L ( 0.3497 ft^3)
BL = 12.8727 N/A
Mms = 114.3188 g
Cms = 219.2481 uM/N
Kms = 4561.0439 N/M
Rms = 4.5509 R mechanical
Efficiency = 0.0628 %

Sensitivity= 79.9973 dB @1W/1m (not sure about this one as everywhere else I've found it to be 91dB)

Let me know if you need any more info from me and I'll do whatever I can!

[Triticum Agricolam]

Ok, so here are my thoughts.

1. Build two boxes with two subs each. You will get a lot better performance with two subs placed separately in your room than you will with just one sub in one spot. With just one sub you will get room reflections that give you really uneven bass at different spots in the room, using more than one sub REALLY helps fix this.

2. If you are going to be putting two subs in one box, you might as well configure them so they are dual opposed. The is where you have one sub mounted on opposite sides of the box. It greatly helps eliminate box vibrations, which are annoying, and can cost you output.

3. As far as box specs go, a good compromise between efficiency, low frequency extension, and size is 1 cube per sub ported at 23 Hz. This should get you good output down to about 22 hz or so, which is really about as good as you could possible hope for out of an 8" sub. This is also another good reason to put two subs per box since its a lot easier to implement a 23 Hz port in a 2 cf box vs a 1 cf box.

4. It just so happens I have a home theater sub design that fits your box requirements. I designed it for a single JBL GTO1014 sub driver, but its 2 cf ported at 23 hz and its just wide enough you can mount two dual opposed 860W subs in it. I call it the Tritsub 10-2.0, anyway here it is:

Here is what my completed sub looks like, if you use my design above you subs would be mounted on the sides instead of the front:

[bmwking]

Ok, so here are my thoughts.

1. Build two boxes with two subs each. You will get a lot better performance with two subs placed separately in your room than you will with just one sub in one spot. With just one sub you will get room reflections that give you really uneven bass at different spots in the room, using more than one sub REALLY helps fix this.

2. If you are going to be putting two subs in one box, you might as well configure them so they are dual opposed. The is where you have one sub mounted on opposite sides of the box. It greatly helps eliminate box vibrations, which are annoying, and can cost you output.

3. As far as box specs go, a good compromise between efficiency, low frequency extension, and size is 1 cube per sub ported at 23 Hz. This should get you good output down to about 22 hz or so, which is really about as good as you could possible hope for out of an 8" sub. This is also another good reason to put two subs per box since its a lot easier to implement a 23 Hz port in a 2 cf box vs a 1 cf box.

4. It just so happens I have a home theater sub design that fits your box requirements. I designed it for a single JBL GTO1014 sub driver, but its 2 cf ported at 23 hz and its just wide enough you can mount two dual opposed 860W subs in it. I call it the Tritsub 10-2.0, anyway here it is:

Here is what my completed sub looks like, if you use my design above you subs would be mounted on the sides instead of the front:

thats a HUGE help! now, i may not have the room to do 2 seperate enclosures, could i somehow combine these two into one?

[Triticum Agricolam]

thats a HUGE help! now, i may not have the room to do 2 seperate enclosures, could i somehow combine these two into one?

It would probably be tough to combine the two into one enclosure, it would be better just to design a new one that holds all four. However, I really strongly suggest you find a way to have two separate enclosures. Seriously, it makes a HUGE difference when you have distributed subs. Ideally you have one right next to your listening position/couch/etc for good tactile response, and then the other sub goes somewhere else in the room to even out the bass. Even if you can't put one sub next to your listening position, its still very much worth it to do two seperate subs.

[bmwking]

thats a HUGE help! now, i may not have the room to do 2 seperate enclosures, could i somehow combine these two into one?

It would probably be tough to combine the two into one enclosure, it would be better just to design a new one that holds all four. However, I really strongly suggest you find a way to have two separate enclosures. Seriously, it makes a HUGE difference when you have distributed subs. Ideally you have one right next to your listening position/couch/etc for good tactile response, and then the other sub goes somewhere else in the room to even out the bass. Even if you can't put one sub next to your listening position, its still very much worth it to do two seperate subs.

I totally understand the reasoning behind the 2 enclosures, I'll try to do my best

[bmwking]

So here's what im working with in terms of space (this is pretty concrete due to the fact that I have a girlfriend who doesnt let me decorate or move things around).

given this, and the equipment selected, are there any more ideas on enclosure?

[Triticum Agricolam]

Well my recommendation pretty much remains the same. I think your proposed location for you sub looks good. If you could place the other sub somewhere near your TV that would be ideal.

I saw your post in the other thread asking about adapting the Decware Housewrecker design to work with your 8"s. I would recommend against that. To get all four in the enclosure, you have to isobaric load them, which uses twice as many subs, and cuts your efficiency in half, so your four 8"s would only be as efficient as one 8". The other issue is scaling down bandpass enclosures can be a lot more difficult than scaling them up.

[bmwking]

Well my recommendation pretty much remains the same. I think your proposed location for you sub looks good. If you could place the other sub somewhere near your TV that would be ideal.

I saw your post in the other thread asking about adapting the Decware Housewrecker design to work with your 8"s. I would recommend against that. To get all four in the enclosure, you have to isobaric load them, which uses twice as many subs, and cuts your efficiency in half, so your four 8"s would only be as efficient as one 8". The other issue is scaling down bandpass enclosures can be a lot more difficult than scaling them up.

Thanks again for the input. The primary reason i brought up the housewrecker was that it was designed to be most efficient with 4 subs in it and that seemed right up my alley. I'm going to email Decware and see if they have a scaled down blueprint i can buy, if not then it will be your setup. nothing personal here by any means, but if i can keep it in the single corner, that's ideal. If i cant, well ill just have to deal with the wrath of the gf lol

[Triticum Agricolam]

Thanks again for the input. The primary reason i brought up the housewrecker was that it was designed to be most efficient with 4 subs in it and that seemed right up my alley. I'm going to email Decware and see if they have a scaled down blueprint i can buy, if not then it will be your setup. nothing personal here by any means, but if i can keep it in the single corner, that's ideal. If i cant, well ill just have to deal with the wrath of the gf lol

That's fine man, if you do use my design, that's cool, and if you don't that's fine too, I just put it out there for ya cuz I think it could work well for your requirements.

Just a heads up, but before you decide to go with the Housewrecker design, make very sure you understand what happens when you put subs in an isobaric configuration. Its easy to assume if you have one sub in a box and then add another, it should get louder. However, with isobaric loaded subs, that is not what happens, it actually gets quieter overall. With a regular (non-isobaric) box, when you add a sub, you are adding cone area. With an isobaric design, when you add a sub, you aren't adding cone area, it stays the same. What does change though is you have twice as much moving mass (which decreases efficiency) and you have twice the suspension stiffness (since you now have two suspensions instead of one). The extra suspension lets you shrink the box size and keep the same frequency response (though at half the efficiency).

For more info on what isobaric boxes do, you can take a look at a couple articles JL Audio put out on them: http://www.jlaudio.com/header/Support/Tutorials/Isobaric+Enclosure+Characteristics/Tutorial%3A+Isobaric+Enclosure+Characteristics/287539

http://www.jlaudio.com/header/Support/Tutorials/Isobaric+Enclosure+Types/Tutuorial%3A+Isobaric+Enclosure+Types/498110

[Triticum Agricolam]

If you REALLY want to ring every bit of performance out of those Infinity's, build four of these:

http://www.diyaudio.com/forums/subwoofers/192539-tapped-horn-lazy-impatient.html#post4530601

Frequency response is a little peaky, but you can fix that with DSP easily enough.