Crossover Components: How much does it REALLY matter?

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#102
So Wolf, if you are out there,

I think I've settled on your Biumph subs. Just to make sure though..It uses the Tang Band 1138 5.25in "Neo" sub and a Dayton 8" Passive, right?

So my next question is whether or not the passive radiator alters impedance. I'm pretty sure it doesn't because for some reason, I'm pretty sure they don't really have an impedance.

Only $15 for the PR (NICE!), and eliminates the port BS which makes me cry, and I get to steal your design...which I KNOW works, and I don't have to do any guessing!

Frequency wise, how well do they hit like 30Hz?
Thanks!
 
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#104
Wait PRs aren't connected at all? Youre shittin me...Wow....That's pretty cool. And I don't NEED 30Hz, just curious. Wow...9Inches is tiny! Alrighty, time to go order this stuff. Sheesh...I think this project is upwards of $500 now. Ahhh! I should have known this would happen.
 
#106
Yeah I never actually looked into a PR before...ever...

It seems to be the best of both worlds...kinda. But anyway, I'm trying to use up a $150 Visa gift card I've had for 5+ years, but of course Mouser doesn't actually tell you what the shipping cost will be until AFTER it has been shipped, so I'm still waiting on them so I know how much money is left on the card...(Just bought some stuff for the Sophomores crossover, and some stray components I forgot).

I'm hoping there's enough on it for the sub, PR, LM4780 chip, the main transformer, and some fuse holders. Hmm, it's going to be tight.
 
#107
AllenB said:
You should probably look at the passive radiator as a compromise between the closed and vented style of cabinet.
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That's hardly correct. It's still a tuned Helmholtz resonator, simply exchanging the mass/compliance of the air in the port for that of the PR. It will still require HP filtering to prevent over excursion in many cases, just like a ported and will roll off faster than a ported and much faster than a typical sealed.
 
#110
A passive radiator is intended to replicate a port, however unlike a port they have Vas and Qms. They may display a low end 12dB/octave rolloff. This is not like halfway between a sealed and vented enclosure but a compromise nonetheless, considering also that passive radiators are used to negate some of the side effects of ports which are not an issue with closed boxes.
 
#111
AllenB said:
A passive radiator is intended to replicate a port, however unlike a port they have Vas and Qms. They may display a low end 12dB/octave rolloff. This is not like halfway between a sealed and vented enclosure but a compromise nonetheless, considering also that passive radiators are used to negate some of the side effects of ports which are not an issue with closed boxes.
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I know how PRs work. Wanna show me a good alignment where they roll off at 12dB/oct?

They typically add another order to the ported 4th order system so they roll off faster than a ported, and have worse impulse response so they are not anywhere between a ported and sealed.

passive-response.gif
 
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#114
I own a PR sub, it don't roll off at 12 dB per octave 🙁

Is it a compromise? Depends how you look at it and what you want. Since it physically sits in a sealed box, no port noise and no sounds blowing through it like an open pipe does. Since my 18" Exodus Audio PR has a physical weight of 1,020 grams (2.25 pounds) it resists cone motion from the active 15" woofer below it's tuning frequency. Not as much as a sealed box but does not allow the woofer to "free air" like a ported box.

All my speakers are sealed except the PR sub, it is tuned to 21 Hz so group delay is not an issue, it physically shakes the floor which my family enjoys during movies (not an issue with music) I was thinking of adding a second PR to balance the box but my teenage son loves how it shakes the floor--it pounds quite literally.

Sealed is from Venus, ported from Mars, horns are from Jupiter and passive radiators are from Pluto. They are still fighting over if Pluto is a planet so it fits. 😕😉
 
#115
18Hurts said:
Since it physically sits in a sealed box, no port noise and no sounds blowing through it like an open pipe does.
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It's still a Helmholtz resonator so it's not functionally different to a port, as has already been explained.

Also, the only time you get port noise (chuffing) is if it is inadequately sized and/or with insufficient end flare. See Collo's experiments.

PRs are great for when you want a low tune in a small box that would be hard to fit an adequately sized port into. They have their place and I am neither pro or against, it depends upon what you want to accomplish and how.
 
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