What would be a good tune for a 7ft3 SI18 - AVS Forum
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Old 06-18-2014, 02:43 PM - Thread Starter
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What would be a good tune for a 7ft3 SI18

Looking for suggestions for a good tuning freq for a SI18 in a 7ft3 net box. I did some modeling in winisd and found 18hz with two 3 inch ports about 14 inches long looked pretty good. I could build a minimarty but I need a different shape. I also would prefer to stick with round ports unless the slot ports would allow me to achieve something the round ports couldn't.

I could go up to 8 ft3 but that didn't appear to offer a lot of gain over 7.
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Old 06-18-2014, 05:41 PM
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I think you nailed it, 18hz. Would be usuable to 15hz.
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Old 06-18-2014, 05:54 PM
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You're going to have some serious port noise if you approach anything near xmax. Which is about 1kwatt. You could underpower it, but that seems pointless. Consider 4x3" ports that are 60cm long for a 20hz tune, or some a way to get that port working. That's still not really ideal either. I'd be thinking 4" ports. That's where slot ports are nice, you can extend them along the side of the box and get lots of mouth area. You might need elbows in your PVC.
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Old 06-18-2014, 06:02 PM
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+1


two 3" ports run air velocity up too high for that driver with full power.


three 4" ports is about what I would suggest as a minimum in your case.


that is one reason the slot works so well -- it is a cheap way to build a large port.

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Old 06-18-2014, 06:03 PM - Thread Starter
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Thanks. How do you calculate first port resonance? I don't see any mention of it in winisd. If the port velocity is real low is that wasting something? If i can get the same tuning with two different port diameters and they are both under the acceptable limit for velocity is one better than the other?
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Old 06-18-2014, 06:06 PM - Thread Starter
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I must have entered a ts spec wrong in winisd because the velocity I got with the three inch ports was 14ms.
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Old 06-18-2014, 06:10 PM
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17hz. SLot port.

-

"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."
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Old 06-18-2014, 06:28 PM
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"I must have entered a ts spec wrong in winisd because the velocity I got with the three inch ports was 14ms. "


did you have your power adjusted to 500-1000 watts or so?

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Old 06-18-2014, 06:36 PM - Thread Starter
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I set 600 watts in the driver spec and 500 watts in the plot spec. I guess I wasn't pushing it hard enough to raise port velocity. What specs should I use?
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Old 06-18-2014, 06:40 PM
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two 3" diameter ports in that configuration with 500 watts gives about 44 m/s air speed.


something is amiss.

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Old 06-18-2014, 06:46 PM - Thread Starter
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I will have to double check my numbers. I must have made a typo somewhere. Are the data-bass numbers more accurate than the SI specs?
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Old 06-18-2014, 07:28 PM
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Quote:
Originally Posted by Samps View Post
I will have to double check my numbers. I must have made a typo somewhere. Are the data-bass numbers more accurate than the SI specs?
I would go by the Databass numbers.

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Old 06-18-2014, 08:02 PM
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this is a test


[IMG]

[/IMG]

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Last edited by LTD02; 06-18-2014 at 08:05 PM.
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Old 06-18-2014, 08:15 PM - Thread Starter
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I re entered the specs from data bass and got the same results. I'm not sure what I'm doing wrong. Here is a screen shot of the ts specs I'm using and the port results I get for 7ft3 with a 18hz tune.
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Old 06-18-2014, 08:24 PM
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mach 0.11 is 11% of the speed of sound at sea level, which is around 340 m/s, so mach 0.11 is about 37.4 m/s.
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Old 06-18-2014, 08:32 PM - Thread Starter
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I thought when the number was green it was in the good range and when it turned red it was a bad number.

So what vent mach do I want to aim for? I can figure out the rest based on the math you posted. Thanks!
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Old 06-18-2014, 08:48 PM - Thread Starter
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How about three 3 inch ports at 22.5 inches. That gets me .05mach which should equal 17ms. That is alot of port though. The slot port is looking better now! How hard would it be to convert the minimarty design into a box that has a 22inch max width or depth for the bottom panel? I need it to fit between a wall and a floor register.
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Old 06-18-2014, 09:17 PM
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how much power are you inputting?

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Old 06-18-2014, 09:31 PM - Thread Starter
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I put 600 watts in the driver specs. But if you're asking about how much I will actually be using, I'm not sure yet. An inuke probably or another pro amp with about 1000 watts. I need as much output out of this as I can get since I wont be able to add another. Large room. Already have a ported 12 to back it up. But it needs to fit around an air vent. I can't move the wall or the air vent. Otherwise I would just build the minimarty, or even the martycube. I probably listen to more music than movies,
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Old 06-19-2014, 01:56 AM
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i simply meant in winisd for the purposes of calculating the mach number.

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