help with EBS enclosure for SI HT-18D2 - AVS Forum
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post #1 of 12 Old 12-21-2012, 05:30 PM - Thread Starter
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I am trying to model SI 18D2 in relatively large low tuned enclosure. I would prefer to keep the size under 17cu.ft , but can probably go as large as 20cu.ft.

I can get a decent curve at 17cu.ft with 12Hz tune. But I am having difficulties with the port. It appears that at this size/tune I cannot have both low port velocity and first resonance outside the passband.

Is there any way around it?

thank you.





I am going to use Inuke 3000DSP to drive a pair of these. Inuke's filters cannot be set below 20Hz. That's why I am using a combination of HPF and PEQ at 20Hz to simulate 15Hz HPF

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post #2 of 12 Old 12-21-2012, 05:42 PM
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You're not the first I have seen make that comment with these SI's -- seems they would be a perfect candidate for a PR (not many of those being done these days). I haven't modeled it yet as I plan to go sealed with mine.
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post #3 of 12 Old 12-21-2012, 06:02 PM - Thread Starter
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Quote:
Originally Posted by Aaron Smith View Post

You're not the first I have seen make that comment with these SI's -- seems they would be a perfect candidate for a PR (not many of those being done these days). I haven't modeled it yet as I plan to go sealed with mine.

I have very little experience modeling. is not size/res.frequency/length of the port are dictated by the the size and tune of the enclosure? or drivers specs also play a role?

I may also go sealed. it's definitely not as easy to screw up as vented design. i would have to double number of drivers to match the performance though.
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post #4 of 12 Old 12-21-2012, 06:09 PM - Thread Starter
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Quote:
Originally Posted by Aaron Smith View Post

You're not the first I have seen make that comment with these SI's -- seems they would be a perfect candidate for a PR (not many of those being done these days). I haven't modeled it yet as I plan to go sealed with mine.

what does PR stand for?
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post #5 of 12 Old 12-21-2012, 06:28 PM
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Passive radiator. It can take the place of a port and allow for smaller enclosures.
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post #6 of 12 Old 12-21-2012, 06:30 PM - Thread Starter
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thank you
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post #7 of 12 Old 12-21-2012, 06:54 PM
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There's your tradeoff - either tune higher, build larger, or deal with your current conundrum. My advice since you're creating a subsonic filter at 15hz, why tune any lower than 14-15hz? Keep box volume the same but raise your tuning a few Hz. Port air speed won't change much, but your first port Res may get closer to 1.5 octaves above LP filter. (At 1.5 octaves, you're 36db down)

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post #8 of 12 Old 12-21-2012, 07:10 PM - Thread Starter
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Originally Posted by Looneybomber View Post

There's your tradeoff - either tune higher, build larger, or deal with your current conundrum. My advice since you're creating a subsonic filter at 15hz, why tune any lower than 14-15hz? Keep box volume the same but raise your tuning a few Hz. Port air speed won't change much, but your first port Res may get closer to 1.5 octaves above LP filter. (At 1.5 octaves, you're 36db down)

so if forced to chose between the two, your advise is to trade port velocity in favor of the higher first port resonance.
1.5 octave above LPF puts me in mid 200s.
what's the max tolerable port velocity in your opinion?
in general, is WinISD a good tool for modeling ports specifically?

thank you
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post #9 of 12 Old 12-21-2012, 07:17 PM
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Quote:
Originally Posted by zheka View Post

I have very little experience modeling. is not size/res.frequency/length of the port are dictated by the the size and tune of the enclosure? or drivers specs also play a role?
I may also go sealed. it's definitely not as easy to screw up as vented design. i would have to double number of drivers to match the performance though.

I've been playing around with this...I don't think it's worth dicking around with throwing a single driver in a ginormous 17 cu.ft. box and trying to figure out how to port it. I would just run 2 separate sealed enclosures in about 6 cu.ft./each or so and hit them with about 600 watts per and sit back and enjoy the smoothing benefits of distributed bass. smile.gif

Now, my modeling is rusty as it's been a few years since I've played around with it. A question for the experts: What do most of you guys use for T/S parameters when modeling a driver that has been tested by Data-Bass? Do you run with the manufacturer's supplied number or the independent tester?
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post #10 of 12 Old 12-21-2012, 07:23 PM
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Quote:
Originally Posted by zheka View Post

so if forced to chose between the two, your advise is to trade port velocity in favor of the higher first port resonance.
1.5 octave above LPF puts me in mid 200s.
what's the max tolerable port velocity in your opinion?
in general, is WinISD a good tool for modeling ports specifically?
thank you
Here's why I would trade some port noise for a higher port Res. At low volumes, that resonance is there, but not port noise. At high volumes everything is so loud, including the rattling of the walls, that if there's some port noise it somewhat blends in with all the other noises.

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post #11 of 12 Old 12-21-2012, 07:38 PM - Thread Starter
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Quote:
Originally Posted by Looneybomber View Post

Here's why I would trade some port noise for a higher port Res. At low volumes, that resonance is there, but not port noise. At high volumes everything is so loud, including the rattling of the walls, that if there's some port noise it somewhat blends in with all the other noises.

this makes perfect sense.
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post #12 of 12 Old 12-21-2012, 07:51 PM - Thread Starter
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Quote:
Originally Posted by Aaron Smith View Post

I've been playing around with this...I don't think it's worth dicking around with throwing a single driver in a ginormous 17 cu.ft. box and trying to figure out how to port it. I would just run 2 separate sealed enclosures in about 6 cu.ft./each or so and hit them with about 600 watts per and sit back and enjoy the smoothing benefits of distributed bass. smile.gif

You may be right. With little EQ single sealed in 6 cu.ft models very close with the vented version upto 30Hz or so. and below the cabin gain kicks in.In my room the sealed curve may actually work better.



hmm..
Quote:
Originally Posted by Aaron Smith View Post

Now, my modeling is rusty as it's been a few years since I've played around with it. A question for the experts: What do most of you guys use for T/S parameters when modeling a driver that has been tested by Data-Bass? Do you run with the manufacturer's supplied number or the independent tester?
i am obviously no expert. but these models are based on the data-bass.com measurements.
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