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I went from sealed to ported and have less output?


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I had a 15" fi Q in a sealed 2.5 cu.ft. box and then replaced it with a Sundown XV2 12" in a 2.5 cu.ft ported box tuned to 30Hz and I had a decrease in overall output and I don't understand why. I specifically tuned it to 30 Hz to get better low bass and it turned out to be less. I am running a DSP and for the sealed box I had the HPF set to 20Hz and the LPF set to 60Hz, for the ported I set the HPF to 22Hz and kept the LPF at 60Hz. I have my mids crossed at 80Hz. Young Jeezy- Put On, which I read the bass frequencies are 55, 44, 37, and 28 hertz respectively plays the first 55Hz note the loudest and has a big drop in output for the next three. The last two are almost nothing.

 

The only thing I can think of is that there is more impedance rise in the ported box or I tuned it wrong.

 

The box is 3.47 cu.ft. gross with .4 cu.ft. of displacement for the sub and bracing and a 6" PVC port with a 90 degree elbow in the box with an effective port length of 24.75", the displacement also accounts for the increased size of the elbow. There is also 6.875" of external port and I have a .75" round over at both port ends. For the round overs I only counted half and added that to the effective length. The torres calculator gave me a tune of 30Hz. Could it be because of the 90 or the port entry being too close to a wall or the sub? Or the Pole vent too close to the wall? Distance is about 3-4" for all of those. Is there any way to verify my box tune? I don't have an SMD IMSG.

 

My amp even draws less current now.

 

Both subs were wired to 1 ohm which I verified with a DMM when in took out the 15" and put in the 12". Same amp and no changes were made to the gain setting. Gain was set with a flat signal from the DSP.

Edited by THEMERQ
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that’s the effective length of the port. The precision port calculator already factors in the flares when finding a port length. Half an inch per flare is the formula on flared ports and they factor t

Thanks never knew that about aero vs slot port bends.

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It’s because of that 90 degree elbow on that pvc port. The only way to do a round port and not lose output it to do it straight. It’s kind of like things in life, the best flow is to be straight and don’t cut corners.

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49 minutes ago, 1point21gigawatts said:

It’s because of that 90 degree elbow on that pvc port. The only way to do a round port and not lose output it to do it straight. It’s kind of like things in life, the best flow is to be straight and don’t cut corners.

WOW... was not expecting that. Is it the same with 45s also?

 

I don't even think its possible for me to get the required length unless I build a new box with the port firing sideways, but then the port exit would be <4" from the vehicle body. Or go to a smaller size PVC but then I might not have enough area.

 

What's the minimum distance I can get away with having the port openings from the sides of the enclosure, sub, and vehicle? I think I could probably make the external port a little bit longer.

Edited by THEMERQ
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12 hours ago, THEMERQ said:

WOW... was not expecting that. Is it the same with 45s also?

 

I don't even think its possible for me to get the required length unless I build a new box with the port firing sideways, but then the port exit would be <4" from the vehicle body. Or go to a smaller size PVC but then I might not have enough area.

 

What's the minimum distance I can get away with having the port openings from the sides of the enclosure, sub, and vehicle? I think I could probably make the external port a little bit longer.

I’d have to see pictures of the port to see how it’s configured so I have an idea of how you make ports so I can tell you what you need to know for you next port build or next enclosure build, whichever you decide on doing. 

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9 hours ago, THEMERQ said:

Also how does the reduced output correlate to the less current draw? Was it just impedance rise? 

A different impedance rise because of the change in subwoofer and enclosure. 

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This is the current box before I cut to the port to length. The final port length only sticks out ~7" and has a donut on the end.

 

IMG_20200820_172927.thumb.jpg.cd4e620056c29eaf584f2d351eb1dd56.jpg

 

IMG_20200820_172943.thumb.jpg.85823bb40c2284dcb39b4f90273e2a0d.jpg

 

The new box can be like the current one but with no bend and If I bump up the volume to 2.7 cu.ft net I can get away with an effective port length of 22". The port will have to stick out about 12"  for the entry of the port to be 6" the rear interior wall of the enclosure. I am not sure how close the port exit will be to the trunk lid.

 

Or like this, I think I can manage to slide the port under the motor, or use multiple smaller PVC pipes to get the required port area but like I said the port exit will be <4" away from the quarter panel.699397550_sideport.thumb.PNG.859882d11b1252521b1c8d6584a28d0f.PNG

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If you were to have a more shallow angle on that 45 I would assume it would perform better. Looks to be a tight 45 with a near 90 degree bend at the "armpit" or inner curve. You could try to adapt it with two smaller fittings, say 20-30 degrees instead?

 

I think the other issue is the port location. They should be furthest from the subwoofer, yours is right up on the basket it seems. I would assume this causes the sub to act as if it is in a smaller box. If you were to straight pipe it you might achieve better results but that also means a Mario tube outside the box... 

 

As much as I wanted to use aero ports they seem quite the beast to fit into a builds without deep boxes. Best of luck man

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23 minutes ago, Joshdashef said:

If you were to have a more shallow angle on that 45 I would assume it would perform better. Looks to be a tight 45 with a near 90 degree bend at the "armpit" or inner curve. You could try to adapt it with two smaller fittings, say 20-30 degrees instead?

 

I think the other issue is the port location. They should be furthest from the subwoofer, yours is right up on the basket it seems. I would assume this causes the sub to act as if it is in a smaller box. If you were to straight pipe it you might achieve better results but that also means a Mario tube outside the box... 

 

As much as I wanted to use aero ports they seem quite the beast to fit into a builds without deep boxes. Best of luck man

Yeah its definitely a sharp turn, I have decides that next box I'm just gonna go with a straight port with no bends, bumping up the size will let me get away with a slightly shorter port length. 

 

I never new having the port too close would do that.

 

1 hour ago, 1point21gigawatts said:

That’s not gonna work out. Let me design you an aero port enclosure you can make with a 6” pvc pipe and some wood that would be ideal for that vehicle and that subwoofer.

How about something like this?

a) addas.PNG.59b88f7a4eaade8d5dd0a0ac55d404b0.PNG

 

b) afdfsaf.PNG.6616ebe7ecf115df7c7052b50537f76f.PNG

Edited by THEMERQ
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