Single Sundown x15 - How to get lots of air movement?

[jcody_parker]

13 hours ago, Triticum Agricolam said:

There is no way around the long port, physics has no short cuts.  

Looking at the box in the video, I can easily believe he has that port wrapped around the inside of the box so that is 80" long or whatever.  I bet that's the case.

As far as which sub, you are going to want lots of Xmax in case you ever want to give the 4th order bandpass a try, I'd stick with the Sundown X-15.  

Honestly I don't even think his box is long enough to fit 80" of port in there, that's what I was confused about. 

[DiBo]

39 minutes ago, jcody_parker said:

The main reason I want to tune so low is that I just love the feeling of the 14hz - 19hz songs that I have. If I tune to 25-28hz, would I even be able to play them? If i'll get more air movement with higher tuning I'll give it a shot, but I figured it would be more slow type flex & windy at 20hz and below.

 

That music that's been rebassed to play 19hz or so I can guarantee you it's for 6th order builds that are tuned to like 24 rear chamber and an octave above for front chamber. If you tune a ported enclosure that low you're going to fall flat around 37hz+/-. I built a ported enclosure one time with the 40 in long port and all it was good for was rebassed music. Seems to me you have plenty of room for 2 15s... I'd run that or 3-12's and tune to say... 27hz and you'll be low and it'll create some follicle turbulence. 

25hz at the lowest. A good 15 moving at 25x a minute with full excursion is going to create some air movement! 

[jcody_parker]

4 minutes ago, DiBo said:

That music that's been rebassed to play 19hz or so I can guarantee you it's for 6th order builds that are tuned to like 24 rear chamber and an octave above for front chamber. If you tune a ported enclosure that low you're going to fall flat around 37hz+/-. I built a ported enclosure one time with the 40 in long port and all it was good for was rebassed music. Seems to me you have plenty of room for 2 15s... I'd run that or 3-12's and tune to say... 27hz and you'll be low and it'll create some follicle turbulence. 

I really want two  x15's, but I can't spend that much on the subwoofers alone right now. I still need amps, highs and mids, head unit, batteries, and 1/0 awg wiring.

[DiBo]

2 minutes ago, jcody_parker said:

I really want two  x15's, but I can't spend that much on the subwoofers alone right now. I still need amps, highs and mids, head unit, batteries, and 1/0 awg wiring.

Builds take time when budget plays a factor. I have 4x 12's in my truck and 2 zv5 18's and 15's just sitting... Gonna get to them soon tho. Lol. 

[jcody_parker]

1 minute ago, DiBo said:

Builds take time when budget plays a factor. I have 4x 12's in my truck and 2 zv5 18's and 15's just sitting... Gonna get to them soon tho. Lol. 

I have a completely empty car right now I just want something for the time being, I don't mind pulling it all apart to build a bigger box for two x15's later in the year.

[DiBo]

Was designed to be musical. All kinds of cancellation but if I really tried I'd hair trick with just 4-12's in a huge cabin. Wife's hair moves haha. Doesn't trick but it definitely moves. 

[jcody_parker]

I suppose I could shoot for a little higher tuning frequency so that I can make the port shorter. So how do you know the absolute max volume you can use without damaging the subwoofer?   Sundown recommends 4.25 cu/ft ported, and everyone is saying to go up to 6 or 7 cu/ft after displacement. So how do you know how big you can go? Just in general on any subwoofer, not just an x15. Is there a rule of thumb or an actual calculation to know the max volume possible?

[DiBo]

18 minutes ago, jcody_parker said:

I suppose I could shoot for a little higher tuning frequency so that I can make the port shorter. So how do you know the absolute max volume you can use without damaging the subwoofer?   Sundown recommends 4.25 cu/ft ported, and everyone is saying to go up to 6 or 7 cu/ft after displacement. So how do you know how big you can go? Just in general on any subwoofer, not just an x15. Is there a rule of thumb or an actual calculation to know the max volume possible?

I usually stick to the recommendations +/-. Never too much above or below. EMF audio has a good video on you tube that shows what happens when we go too large for the subwoofer with excess power. Bad things happen to surrounds and subs in general. You can only squeeze so much juice out of the orange for lack of a better analogy. Remember Hoffman's iron laws also... Bass extension, efficiency, and small enclosure... Pick 2. You ever noticed that Sundown recommends bigger enclosures than most other manufacturers? 2.5 for 12's, 4.25 for 15's, and 7ft³ for 18's. You can reach xmax in recommended enclosure specs with roughly rated RMS. No need to try to reinvent the wheel. That's just My experience with sundown drivers. 

Disclaimer) I'm not anywhere near an expert. I just try to share what I've learned in this past two years of my bass addiction. I do know sundown subs pretty well tho. I also build at least 2 boxes a week so yIve had a decent amount of experience for my short time doing this. Just thought I'd put that out there. 

[Triticum Agricolam]

17 hours ago, DiBo said:

I think maybe he thinks he needs to tuned in the teens to get that extra low end. It's going to sound horrible if he does. Your we correct about the extra long port to tune extremely low but sheesh... That'd be crazy if he did. I would never tune under 25 for any reason!! In my opinion also, 4th orders are to achieve upper frequencies. If it's low lows he wants and still wants to be any kind of musical... Gotta tackle that 6th order beast. Jmo

Tuning that low shouldn't sound horrible, I've built several home theater subwoofers that were tuned to the high teens and they sound great.  It just depends on the specs of the sub and getting the box specs correct.  Not all combinations are going to work well, but many will. 

Here is the frequency response of the X-15 in a 6 cu ft box tuned to 17 Hz:

In my opinion that looks really good!  

[Triticum Agricolam]

8 hours ago, jcody_parker said:

I suppose I could shoot for a little higher tuning frequency so that I can make the port shorter. So how do you know the absolute max volume you can use without damaging the subwoofer?   Sundown recommends 4.25 cu/ft ported, and everyone is saying to go up to 6 or 7 cu/ft after displacement. So how do you know how big you can go? Just in general on any subwoofer, not just an x15. Is there a rule of thumb or an actual calculation to know the max volume possible?

There is no rule of thumb for box size.  Using "rules of thumb" for anything is car audio is kinda asking for trouble anyway since they are all based on assumptions that may or may not be true in your particular situation.  

As you tune lower you want a larger box to try to keep the frequency response looking decent.  You wouldn't want to put a X-15 in a 6 cu ft box if it was tuned to 32 Hz.  Also you have to keep cone excursion reasonable based on the amount of power you are running.  I wouldn't use the same size box for a 3000 watt system as I would for a 2000 watt system.  To see how much cone excursion you will get its best to model the box in simulation software, such as WinISD. 

Here is the cone excursion graph for a X-15 in a 6 cu ft box tuned to 32 Hz on 2000 watts, there is a subsonic filter set to 14 Hz:

The red line is Xmax, generally you don't want to exceed that or bad things can happen.  As you can see, the 6 cu ft box work fine.  The sub sonic filter is very important though, here is what it looks like without it:

As you can see, cone excursion goes through the roof below tuning, it would be very easy to damage your sub.