tuning my box

[dvldogyut 10+ year member]

i am pretty new to all of this. i am building a downfiring box for two incriminator audio 187 series 12's. what should i tune my box to for the lowest hard hitting bass without damaging my subs? and where should i place my port? facing down with the subs? and what is the best way to wire them? in a series or parallel?

this is from their site.

Driver 12 Inch

MSRP $149

FS 34 Hz

Re 6 ohm series

Qms 4.79

Qes .58

Qts .52

Mms 152 g

Cms .148 mm/N

Sd 530

Vas 55 L 105 L

Spl 87.3 db 1w/1m

BL 18 TM

X-max 22 mm p2p

Sub Diameter 12 1/4"

Mounting 11 1/8"

Mounting Depth 6 1/4"

Driver Displacement .10 cubic ft.

Power 300 Wrms / 600 peak

Driver 187 Series 12 Dual 2 ohm

Sealed 1.4 cubes - 2 cubes

Ported 2 cubes - 2.5 cubes, 20 - 30 Inches of Port, 28-35 Hz

Click to read more...

 

[roburt12]

On this sub page, I will prove how important it is for a woofer to be tuned to its speaker cabinet. This is quite a long page with charts and definitions but contains the most important information dealing with speaker design and is well worth your reading. Save it or add a bookmark if you don't have time to read it all. First I will have to clear up some myths and define some terms. I get many calls from the know-it-all types. When they start spouting off about wanting to "improve" their speakers with new woofers and then ramble on about power handling and magnet size, I know I'll have to spend awhile on the phone reeducating them. This page will hopefully save my vocal cords and reduce my phone bill.

Holidays to Egypt

Apex Professionals LLC

 

[betteraudio 10+ year member]

Alright, well let's start with how to wire the subs. That is going to depend on what amp you are using, and to what impedance it is stable, how much power it produces into each load it is capable of driving, and the power handling capabilities of your driver/enclosure combination. I say combination because how you tune your box can dramatically effect the excursion produced by a given level of input power.

What we know so far is that you have 2 woofers, each with dual 2-ohm voice coils. You have 2 options for each sub. Wire the coils in parallel for a 1 ohm load, or in series for a 4 ohm load.

You can then wire the two woofers together in series for either a 2 ohm load or an 8 ohm load, or in parallel for either a 0.5 ohm or a 2 ohm load.

If you are using one amp, you will want to wire the voice coils in series and then wire the subs together in parallel, which will give you a final impedance of 2 ohms.

You could accomplish the same load by wiring the coils in parallel and then wiring the subs in series, but wiring dual voice coils in series doubles the BL of the driver, which is desireable.

If you were to wire all the coils together in parallel, you'd have a 0.5 ohm load, which most amplifiers would not be able to handle.

Now on the other hand, if you are going to use two amplifiers, you can wire each sub's coils in parallel for a 1-ohm load, provided both amps are stable to 1 ohm, which is much more common than 0.5 ohms stability.

As for the box, it looks like the manufacturer gave you a good idea of what ranges you should be looking at. If you are looking for maximum low end hard hitting bass, I would say go with at least 2.5cf per sub, and tune at 28Hz.

I would get yourself a copy of WinISD and plug the driver and enclosure parameters into it and then tell it how much power you're going to be giving it in the signal tab.

Once you've done that, you'll be able to go to the Rear Port Air Velocity plot, and see how fast the air will be moving in whatever port dimensions you enter in the Vents tab of the design window.

Anything over 17 meters/second is likely to result in port noise, so you'll want to use however large a port area is required to keep velocity below 17m/s. It will tell you the length required for a port of those dimensions.

Just remember to calculate the displacement of the port (it will be significant) and add that to the volume you specified in the Box tab, along with whatever the woofers will displace, to know how big to build the enclosure.

 

[dvldogyut 10+ year member]

My biggest thing is that I am trying to fit this under my back seat. so my box is going to be a little less than 2 cubes per sub that is including the port and sub. Is two inches enough room for the sub to be off the floor? And will the rear port be the best?

 

[dvldogyut 10+ year member]

bump

 

[dvldogyut 10+ year member]

bump

 

[azimuth 5,000+ posts]

My biggest thing is that I am trying to fit this under my back seat. so my box is going to be a little less than 2 cubes per sub that is including the port and sub. Is two inches enough room for the sub to be off the floor? And will the rear port be the best?

2 inches is probably enough. kinda pushing it, but you're probably fine. i'd be more concerned with air space. if you have 2 cubes before displacement, you're realistically at about 1.5 cubes per sub, which is a full cube short for those. 10's in that space would probably be louder and sound better. i'd just seal them in 2 cubes per sub. it's better to give it enough space sealed, then to choke it off in a small ported.

 

[dvldogyut 10+ year member]

2 inches is probably enough. kinda pushing it, but you're probably fine. i'd be more concerned with air space. if you have 2 cubes before displacement, you're realistically at about 1.5 cubes per sub, which is a full cube short for those. 10's in that space would probably be louder and sound better. i'd just seal them in 2 cubes per sub. it's better to give it enough space sealed, then to choke it off in a small ported.

they are at a little under 2 cubes after displacement.