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AHall

1802 sub port experiment

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Did some experimenting today with the subwoofer. When it is tucked into its hole its size is very manageable. I forgot how massive it is when the behemoth is actually pulled out into the room. It makes the jubes look like bookshelves in person. 75” tv for reference.

 

The measurements were takin from my middle couch seat 14ft from the subwoofer horn mouth. I did the initial peq using Chris’s thread. And did so with all ports open as they came from the factory. 

 

 

 

I’m uncertain what I’ve lost up top at the expense of lower performance at this point. And I’ll try to see if there is any room for optimization in the freq response with the second port closed. To keep things consistent I made sure not to move the mic or change any peq along the way. 

 

Id like to hear everyone’s opinions on this heresy. 

 

ji04uH5.jpg

 

osAxg2p.jpg

 

CD0w1hc.jpg

 

0bEz4Bt.jpg

 

 

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2 ports closed.  Sweet.

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As big as the freaking subwoofer chamber is.....you could smooth out with three ports closed.  Wonder if the driver could handle it.

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I'd use a roll of foam to close the ports, myself.  If you close too many ports you'll make the others chuff. 
.

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Or a roll of socks

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I used a rolled up T-shirt and capped it with duct tape. It’ll be fine for what I’m doing 

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Did anyone ask Roy the ramifications of these changes as I'm sure they are there for a reason...?

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26 minutes ago, seti said:

Did anyone ask Roy the ramifications of these changes as I'm sure they are there for a reason...?

 

I got his reply a day or two ago. 

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8 hours ago, AHall said:

 

I got his reply a day or two ago. 

HELLO AND?????

 

 

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He mentioned he went with the 7 port design due to high spl levels for cinema use. I should be good with the current 5 port configuration and have enough spl to go deaf. Closing another port will get me lower but might be approaching the limit of the amount of spl the 4 ports will generate and create chuffing. I will need to play content to see if I run into this issue. 

 

So my plan is to leave it how it is with 2 ports closed. I’ll play some music and movies at high spl to see if I get any negative results. Then I’ll repeat with the third port closed. I don’t plan to attempt closing a fourth port. And I may try to do a slug test to see when compression occurs with each. After I’m done I’ll decide if 2 ports or 3 is better for my use. 

 

If we are -3db at 15-16hz currently and didn’t lose any usable home performance id say this tuning is a winner. And maybe just a bit better with 3 if it doesn’t chuff. 

 

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3 hours ago, AHall said:

He mentioned he went with the 7 port design due to high spl levels for cinema use. I should be good with the current 5 port configuration and have enough spl to go deaf. Closing another port will get me lower but might be approaching the limit of the amount of spl the 4 ports will generate and create chuffing. I will need to play content to see if I run into this issue. 

 

So my plan is to leave it how it is with 2 ports closed. I’ll play some music and movies at high spl to see if I get any negative results. Then I’ll repeat with the third port closed. I don’t plan to attempt closing a fourth port. And I may try to do a slug test to see when compression occurs with each. After I’m done I’ll decide if 2 ports or 3 is better for my use.  

 

If we are -3db at 15-16hz currently and didn’t lose any usable home performance id say this tuning is a winner. And maybe just a bit better with 3 if it doesn’t chuff. 

 

Ahh... I might have to try that sometime but seriously how much lower do you need to go lol....

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The way those curves were progressing, I'd be tempted to block off all the ports and take a measurement.  Could probably sacrifice a few dB of overall output if it ended up table-flat...

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10 minutes ago, glens said:

The way those curves were progressing, I'd be tempted to block off all the ports and take a measurement.  Could probably sacrifice a few dB of overall output if it ended up table-flat...

 

I think you’d lose a lot of your spl going from horn loaded ported to hornloaded sealed in a big box. The response is already pretty flat and would be borderline inaudible. Most graphs are in a 5-10db scale usually. I like everyone to see what’s going on better. I have the xilica dsp controlling this as well. 

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Oh, I hadn't expanded the image enough to note the vertical scale.  Agree that looks quite good.

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Current update. Redid some eq. This is the current response at the listening position. Added a bit of a house curve into the peq. Still using 2 ports closed. I haven’t noticed any negative results as of yet. 

 

PJJa5yY.jpg

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On 1/13/2019 at 7:55 AM, jwc said:

Or a roll of socks

 

I used to use a roll of socks to plug the ports of my old Marantz

Imperial 7s in college! 

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