Box help again

[bbeljefe]

137SQ of port for a single AQ 15" sub??? that´s dumb!

Do you have an argument to make? If it's dumb, by all means please tell us why.

Just knowing something is "dumb" doesn't help anyone correct their problem.

[robby512]

first off thanks for your patients and helping nd I'm trying to.understand this I have total port length of 27.5 makeing an L port so the top part of the l is 15.5 long second part of the L so the ( _ ) or the extension is 12 so wouldn't that make 27.5 total length nd that by the width and you get 137.5 total port

[fecupe2001]

137SQ for a single AQ 15", it´s gonna be a very peaky box with a shitty bandwith, and not only that, it´s simply a way too big ass port for that sub wich is gonna bottom out like crazy when you try to play a frequency out of that small bandwith , isn´t that dumb?

3 4" aeros, single 7" aero, single aero 8" or maybe about 58-70SQ of port is more than enough for a daily application like he wants, Don´t want to hurt anyone feelings or generate some kind of soap opera on this topic, just telling the truth, that would be one piece of crap box for a daily application...

[bbeljefe]

first off thanks for your patients and helping nd I'm trying to.understand this I have total port length of 27.5 makeing an L port so the top part of the l is 15.5 long second part of the L so the ( _ ) or the extension is 12 so wouldn't that make 27.5 total length nd that by the width and you get 137.5 total port

If you're measuring the port length at the center of the port, then yes, that's correct. So in other words, if your port is 9" wide, you would take your measurements 4.5" in from the perimeter walls of the box that will be common to the port.

[bbeljefe]

137SQ for a single AQ 15", it´s gonna be a very peaky box with a shitty bandwith, and not only that, it´s simply a way too big ass port for that sub wich is gonna bottom out like crazy when you try to play a frequency out of that small bandwith , isn´t that dumb?

3 4" aeros, single 7" aero, single aero 8" or maybe about 58-70SQ of port is more than enough for a daily application like he wants, Don´t want to hurt anyone feelings or generate some kind of soap opera on this topic, just telling the truth, that would be one piece of crap box for a daily application...

You've still not explained why you make these assertions. I'm fine with what you think is going to happen but that doesn't tell me why it's going to happen.

And as an example, my advice on port area is based on the xmax and the desired tuning frequency. If you have a formula or at least some sort of cogent explanation for why this speaker only needs half that port area, please share it. I don't want to dispense bad advice to anyone but I'm certainly not going to change what I've been doing for years over the words dumb and peaky being tossed around.

[robby512]

I don't know why I'm having so much trouble with this so what your telling me is I need a 9 inch wide opening for my port not a 5 inch with my same exact measurments of 15.5 down then 12 over for the port on the inside

[CleanSierra]

137SQ for a single AQ 15", it´s gonna be a very peaky box with a shitty bandwith, and not only that, it´s simply a way too big ass port for that sub wich is gonna bottom out like crazy when you try to play a frequency out of that small bandwith , isn´t that dumb?

3 4" aeros, single 7" aero, single aero 8" or maybe about 58-70SQ of port is more than enough for a daily application like he wants, Don´t want to hurt anyone feelings or generate some kind of soap opera on this topic, just telling the truth, that would be one piece of crap box for a daily application...

You've still not explained why you make these assertions. I'm fine with what you think is going to happen but that doesn't tell me why it's going to happen.

And as an example, my advice on port area is based on the xmax and the desired tuning frequency. If you have a formula or at least some sort of cogent explanation for why this speaker only needs half that port area, please share it. I don't want to dispense bad advice to anyone but I'm certainly not going to change what I've been doing for years over the words dumb and peaky being tossed around.

He has hours upon hours of building, testing, rebuilding, and testing more.

[bbeljefe]

I don't know why I'm having so much trouble with this so what your telling me is I need a 9 inch wide opening for my port not a 5 inch with my same exact measurments of 15.5 down then 12 over for the port on the inside

134" divided by your 15.5" height leaves 8.64". I would make it 8" wide and call it a day. And in doing so, you would measure your port length down the center of the port, which in this case, will be 4" from the perimeter wall(s) of the box that are common with the port.

But with all that said, let's back up a few steps and find out exactly what tuning and box volume you're after. Forgive me if that's already been stated but I couldn't find it.

[robby512]

OK I finally see why I wasn't understanding this I think I was taking the total internal height of the box and dividing it by 134 it tuned to 38-40 well I want it tinned to hit

so 134/20.5

You are taking what I'm using as my port length not the total internal height.I would like it to be the hardest hitting loudest bass possible so tunning I'm up in the air whatever is best. So when calculating port I take what the first part of the port wall length will be not the internal height

[bbeljefe]

He has hours upon hours of building, testing, rebuilding, and testing more.

That's lovely for him and whoever sells him wood. I had hours and hours of golfing under my belt when I sold my clubs and I still couldn't score under 100... on the front 9. ;-)

I don't care what someone says they've done and I don't care what sort of paperwork they have hanging on their walls. I care what their arguments are and what they do. Since I don't know fecupe, I can't assess his advice by why what I've seen, so that only leaves assessing it by his arguments... which he has still not made. And now you're in here not making arguments for him.

He may very well be a genius but I can assure you that when someone asked Einstein why his theories of physics were more accurate than Newton's, his answer wasn't "because Newton's theories were dumb".

In any event, at least there is one thing productive about this discussion... I've decided to model three boxes with this driver in them. All three models are 4 cubic feet, tuned to 37 Hz. The difference being that the port area is different on them all. The green model has 137in² of port, the yellow has 85.25in² of port (because 5.5" width was mentioned above) and the pink has OPs original 3.5" width for a total of 52.5in²:

You'll notice that the only model you can see on the screen is the pink one. That's because the response curves for all three are identical. Likewise, phase SPL and group delay are all identical.

The most interesting thing I've noticed here and something I intend to research further, is that even with the small port vent mach is still well below the .16 threshold for a noisy port.

So either WinISD is incorrect, which I doubt because I've used it for about a decade with much success, or the port area calculator I've recently been using is incorrect. Or... there is some other parameter that WinISD and I am not considering, that this port calculator is.

So in the end, I owe OP an apology for advising him to build a port that he doesn't need and I have learned that in all likelihood, I'll not be using that port area calculator in the future. At least, not until I find out why its recommendations are what they are.

And with all that said, I still don't know why fecupe claimed that the port area I recommended would make the box "peaky". And likely never will... because it wouldn't.