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Discussion Starter · #1 ·
Here is where I am currently with my design and I feel fairly comfortable with the numbers. This was calculated with WinISD.


SPEC:

Dual ACI SV10s

Passive Vented Design, with front/back opposed drivers, port also on back.

Enclosure of 2.85 cubic feet.

I will likely be using polyfill to get an effective 25% size increase.

Port will be 4" Diameter at 41.5" long.

Drivers, bracing and port are roughly .45 cubic feet.

This should result in a 3.0 cubic foot enclosure tuned between 16-18Hz.

I will have two of these.

This will ultimately be EQ'd.


At MAX POWER for the drivers (500 Watts for two), I get...


SPL:

94 dB at 10 Hz

106.6 at 20 Hz

111 at 30 Hz

112.6 at 40 Hz

113 at 50 Hz (with 1 dB up from there)


GROUP DELAY:

15.2 ms at 20 Hz

9.8 ms at 30 Hz

6 ms at 40 Hz

4 ms @ 50 Hz (drop from there)


PORT AIR SPEED: (I will have large flares on the ports)

19.6 m/s at 20 Hz

9.7 m/s at 30 Hz (continues to drop)


DRIVER EXCURSION:

XMax + 10%


Any thoughts/improvements on the design are welcome, but I think this should give a great result in not much space. Hopefully when combined with room gain and the equalizer, it will give quite the quality bang for the buck.


Agree? Disagree?


Thanks!
 

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Thoughts? Increase box size so you can decrease port length. And for ported enclosures, you usually don't get more than a 20% increase with fill. Also, fill tends to negate the effect of the port.
 

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As Looney said, port length is too long which will result in a nasty resonance in the passband. With the rear faceing woofer/port you'll have to place it far enough off the wall to avoid port compression. I'd side fire them with a front mounted port. I've built designs who's port speed reached 35 m/sec with absolutely no audible effects so if you need to drop the diameter to 3" to reduce the length i wouldn't worry. A front mounted slot port would work nicely as well.
 

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A single 3 inch port sounds a bit small. Of course its tuned low so the effects, if any, will be heard only during low hitting scenes. I had a single piece of junk rca 10" subwoofer driven by 120 watts and I got chuffing from it. Got a lot of other things too, but chuffing I had. I figured it was tuned in the mid 30's though so I am sure that had something to do with it. It had a 3 inch flared port.
 

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Are you dead set on those drivers? You may get better results with a single larger driver.
 

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Discussion Starter · #6 ·
Port resonance is at 163Hz. Is that too low if I plan on crossing at 100Hz?

I may be going a little larger with my enclosure, or I may go with a smaller sealed. Am I locked into these drivers? No, but those are the ones I got a great deal on. I am open to other drivers, but I feel I have modeled almost anything out there and these are certainly a good bang for the buck.
 

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Quote:
Originally Posted by theater_lover /forum/post/17030881


Port resonance is at 163Hz. Is that too low if I plan on crossing at 100Hz?

I may be going a little larger with my enclosure, or I may go with a smaller sealed. Am I locked into these drivers? No, but those are the ones I got a great deal on. I am open to other drivers, but I feel I have modeled almost anything out there and these are certainly a good bang for the buck.

163hz and XO at 100hz? That's not even one octave. If it was me, I'd keep my 1st port res a minimum of 1octave away, so >200hz. That would likely mean a bit bigger enclosure and/or a higher tuning point. Or, beefy enough mains to handle a lower XO point of say 70-80hz.
 

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You will hear chuffing with a 3 inch port, particularly with the low tuning you are looking at. If you are using a BFD to tame your room, you can add a notch at the problem frequency for the port.


You want a clear path from the driver to the port, so lining the box to catch resonances, rather than using stuffing is the way to go.
 

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Discussion Starter · #9 ·
I am currently trying to decide if I should just do a dual sealed design, or use a passive radiator instead of port. I get a fairly good response with CSS's 15" passive. I also like the fact that you can tune it after the box is built. It is more $, but saves a lot of the trouble of port design.
 
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