building box for l7's

Here's the link to Unibox http://www.pvconsultants.com/audio/boxmodel/unibox.htm  But you have to have Microsoft Excel installed on the computer because this program along with most of the others in the FRD Consortium use the .xls file which shares info between the programs using the Excel spreadsheet.  It's free.

I like the easy way you can enter parameters, and I especially like the graph displays.  My biggest problems with it is that the units of measurement (like cm^2 or liter) are fixed;  you can't just click on them to change them to inches or whatever like you can in WinISD Pro.  Another thing is the fixed graph.  It goes up to 1000 Hz and up to 130 db, and I can't find any way to change that.  A box's response will only affect frequencies below 1k anyway, so that part makes sense...but I'd like to be able to see a peak above 130 db.  WinISD allows you to change the graph to a higher peak to see the response.  I could probably just lower the wattage input and keep the peak on the graph...then just add 3 db per doubling of power, I suppose.  But I don't think that's an accurate way to do it when you're dealing with a port...

This program is pretty easy to use, so it's worth getting it.  I can enter data quicker in this than in WinISD.

I  want to look at your setup again now that I know you're using two amps.  I can't imagine you want to use a common chamber with two amps, but you're the expert.  I would play it safe and use two chambers, two ports.  If one amp or sub glitches at high db's, both subs will go, using one chamber.

Yeah, I was using 6.5 cu ft, one chamber, two subs 4 ohms each wired in parallel to 2 ohms for that with 1500 total watts.  But now I would look at it again using the parameters of each sub in parallel for 1 ohm, and look at each one individually.  But...I'm not sure of them because the parameters listed are for 2 ohm coils in series.  I'd like to know what they really are if you're going to be running these at 1 ohm.

...oh yeah, that's another thing I like better about WinISD...you can change to a rectangle port and the program will figure it for you, but with Unibox it gives you only the diameter of the port you have to get to eliminate noise.  So you have to do the change to a slotted by other means.  They both have their good points.  The last project I worked on I loaded it in both programs and worked it both ways.  Like, WinISD would immediately give me an answer for centimeters when all I had was inches and I could just enter that into Unibox...stuff like that.

But this conversion calculator helps out a lot, too.

I'd just want to know whether you intend on using one common chamber or two separate chambers/ports.  And the other thing I don't know about this sub is its RMS.  The parameters list 750 watts Pmax.  I wouldn't want to figure on a port size for that if the RMS is really 500 watts or something like that, because Unibox calls for "nominal power" when it figures how big the port diameter has to be.

OK, so that's the way I had it figured, then.  Each sub is wired to 4 ohms, the two are paralleled together to get 2 ohms.  The mono amps are strapped, receive the load of 2 ohms, and each amp outputs at its 1 ohm rating.  So there is at a minimum 1050 watts available to each sub (engine off) but you'll be adjusting so that the subs aren't overpowered.  So figuring 750 watts each, or a total 1500 watts, would be right.

Using the 76 sq in port opening with a 3" length, 55 Hz tuning, here is the graph:  vb_response_kicker_l7_12_sngl55.gif .......which appears the same as the other 55Hz graph, the difference being that the port opening is a little smaller.  A slot 5.5 X 14 or whatever fits.

From what I can understand with the info I have, the program says the max SPL at 1500 watts is 121.7 db.  The graph at the upper right says "response peak 011 db", so I'm guessing that's added to the 121.7 for a total of 132.7 db.  That would be my guess as to where the peak tops off in the graph.