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Should I Mod A Sealed Subwoofer Box With A Passive Radiator?

Cody AOC said:
So any of you willing to answer if I used a smaller box that is vented but a 6 cu ft vented box sizing is recommended by the manufacturer and I use a 4 cu ft box would that still be ok that is the biggest in sizing I could go after that 21" deep I have no more room for a box
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All the driver parameters are listed there under product details. Find one of the many free speaker box design programs, enter the driver parameters into it, and you can then easily see what happens when you change box size, port length or diameter, etc.

The 3.1 cf sealed box that they call out gets you down to 35 hz.

bs
 
I've used the Ultimax 15, and modeled it a lot during that process.

If you're not willing to give it at least 5 cubic feet, there's no benefit to venting or using a passive radiator with it, in terms of response. The Q is just too high in those enclosures, to get anything near flat response.

5 cubic feet with a vent frequency of 16 Hz, gives an effective f3 of about 23Hz, with only about a .7dB of ripple (about the same amount of ripple of the woofer in a 3.1 cubic foot sealed box- Qtc of about .89). That could be done with a passive radiator (it would be very difficult with a port vent, since said vent would need to be a minimum of two 3" vents, about 3 FEET long each), with a lot of mass on the PR. I didn't model that, but there's programs that can convert a vented enclosure tuning to the weight and surface area or diameter needed for a PR...

Regards,
Gordon.
 
I'm going to respond, tho I really hope this isn't a waste of time.
And PLEASE, try to use punctuation. It's not hard and makes it a LOT easier to understand what you are writing.

My comments:
I think you are reading 11 cu ft from the Parts Express web site. The engineering team at PE are very good at what they do. That said, they typically "optimize" to the lowest possible frequency for the web site and marketing without much regard for real world scenarios. A ported 11 cu ft box is MASSIVE.

If you were to place that woofer in an 11 cu ft box, with a PR instead of a port, you'd likely see the same low end frequency response from the system. But that's not the whole story. A PR needs to be tuned to a specific weight and frequency so that the bass waves from the woofer and the PR do not cancel each other out. This takes tuning equipment, a good ear, and a lot of patience. When done right, the results are very good. If done poorly, the whole system will sound like ****. You may get a bass bump at 18 Hz, but you may also get strange dips and resonance issues at 30 Hz, 50 Hz, or whatever harmonic is being affected by poor tuning.

As has been mentioned NUMEROUS TIMES already. Take the T/S parameters of the Dayton driver, plug them into any of the free speaker box calculators available online and see the effects of box size on system performance. If you make the box too small, and the system Q starts to creep too high above .7, you're going to get very peaky bass, very boomy. Maybe that's what you want. I don't know. if you want "Audiophile" bass you're going to want to keep the system Q just under .7. In order to accomplish this in a ported box, you'll need a very large box. 6 cu ft is not enough.

Now, I ran this driver very quickly in BassBox6 Pro and the optimal setup (with the voice coils wired in parallel) which didn't seem too outrageous is a sealed enclosure at 2.8 cu ft and stuffed about 80% with fiberfill. This will get you an F-3 of 34 Hz and an F-6 of 26 Hz. and an SPL level of about 105 which is plenty loud. This doesn't include room correction or placement options, etc. Just assume 2 planes in the simulation. The driver with the voice coils wired in parallel has a Qts of about .47, which is typically sealed territory, not ported.

Good luck!
 
Interestingly, the UM10-22 will get you deeper bass and a much more even frequency plot, in a 1.3 cu ft ported enclosure, but you'd need to finagle a 72" long 4" wide port to get it done. This might be accomplished by using a type of flex tubing, making the box slightly larger than the 1.3 cu ft to accomodate the tubing, and winding it around inside the box like a snake.

http://www.homedepot.com/p/WEN-4-in...SbYUXpCTUDoX04YCnoKAkBoCXp7w_wcB&gclsrc=aw.ds
 
The ported size requirements you have are really pointing to different driver. Pick a driver with a lower qts and vas. Then of course model it in software.
It's very easy to make a ported sub sound bad, boomy, and be loud at 1 frequency. Designing a ported sub with a flat response requires a bit of work.
 
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To the OP: I'm the type that gets some info, and then may... or may not... follow that info, and instead go with my intuition. Sometimes it has worked out, and sometimes, you know what... they were right. Hey man, if you want to try something, **** even if it fails, and toasts your equipment, you will learn a lot from your experiment. I always have. Just know, obviously, that whatever you try might end up costing you some bucks when you smoke a piece. If you've got the dough to fund this experiment, enjoy buying the stuff and putting it in and turning it on!!!
 
equalized sealed box subs are sooo much easier.

and you get smooth bass with minimum overhang.

but i have also heard spectacular ported subs, though they had very good engineering behind them....

i would investigate sealed box. i have built PR woofer systems and often you can tune them by ear with modeling clay to add weight until they sound (or measure well) and then weigh the clay and fashion a permanent weight.

just my two pennies.:)
 
My own 2 cents:

Cody mentioned in his original post that he wanted to mount the passive radiator on the top of the enclosure, which is a huge no-go.

Passive radiators have a lot of extra mass as part of their loading (to mimic the air mass in a long port) which would cause the diaphragm to sag - possibly to the end of its excursion - if mounted horizontally. Passives must be mounted to a vertical baffle!

RB
 
the skipper said:
Go ahead. I'm sure you know more than the team of engineers who designed the system to begin with.
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Product decisions are based on cost too. There are some sealed box subwoofers with major performance improvements when a PR is added.

They were even sold that way, with & without. The ones without were cheaper.
 
bhunter said:
Adding a passive sub to a sealed sub has similar constraints to a vent. Think of the air column in the port acting as a passive radiator. You gain some flexibility and no so-called "chuffing" sound with a passive, but using a passive radiator does not make up for lack of volume. I prefer sealed subs or transmission lines and multiples for music. What are you trying to achieve? Louder or lower? HT or music? There are numerous well designed subwoofer plans on the internet. Check out the Martysub and Parts Express projects.
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If the sub was optimized for a small sealed box in general it continues to behave that way until the PR resonance is reached.
 
the easiest thing to do is run it sealed, and add some equalization to bring the bottom end up.....looks like you need to add 6db of boost at 26hz to get flat to there....
 
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