Sealed, Ported, or Passive Radiators?

A passive radiator is the same as a port, but it can just be tuned by the mass of the radiator verses a HUGE column of air or a port so small it would chuff. BOTH systems will show the maximum port velocity or passive radiator excursion when the active driver moves the least. This is the theory of the critical damping frequency system. The active driver hands off more and more of the work to the port or passive radiator the lower you go. That's good as it minimizes cone excursions at the very low-end improving disortion numbers. It's bad in that the port / radiator can take control of the active driver as it has a lot of acoustic leverage on the active driver the lower you go. New driver integration and suspension allow much better control than past systems (ever hear a JBL L36?).

Ports are tough to do well, because they have two resonance design frequencies, though. One is high enough to give the classic mid bass "hump" many ported speakers are noted for. Air suspension has one resonance hump to manage but needs LOTS of cone excursion to go deep, or BIG woofer area, or both. CAD has allowed a HUGE improvement in ported speakers such that sealed enclosures are almost a lost art. Amazing what a few decades do to design.

Still, each has pluses and minuses. I don't really have room for HUGE ported subs or do home theater so that I need infinitely loud explosions. How loud is too loud on a movie sound track? If the blast didn't turn your guts into paste, it wasn't realistic enough. Music doesn't need to do that, it's enjoyable. Dying standing beside a bomb isn't.

There is a lot of good info on the web on speaker design and when you read about the complexity of ported speaker design, you think, "no way!" Well, amazingly, there is a way today. But, ported or passive radiator cabinet volume is bigger all things being the same (low-end frequency reach). Physics can't be denied just used to perfection in modern ported or passive radiator speakers.

01-06-13: Rower30, I agree with your take on how passives sound and work, we just have a difference in opinion about how much bandwidth should be available from a system. To be taken to the literal edge would mean constructing an I.E.D. series of Loudspeakers. While that sounds tempting and profitable, from a military standpoint, I don't think that is what I'm after...... Well only if I get a controlling stake in the company.(LOL!!!)

I imagine we don't listen to the same music either, you see, I listen to some music that was designed to be turned up. I don't mean to judge or any thing, but, I don't know many people that enjoy 28Hz bass-lines playing away at 120db. I also believe that constantly (and by choice) listening to music from inferior setups can be an injustice to it's composer/creators.

One of my favorite little "prototypes" I built used Two massively overbuilt 5" drivers/woofers (I forget the actual size of the magnet, but it is the same diameter as the cut-out hole for the woofer!) mated to a 15" passive radiator in a 2 cubic foot enclosure. That became my "little" sub-woofer of choice for listening to Pink Floyd's album "Wish you Were Here".

Also - What do you think of the idea about using different woofers in the same system? Split up to cover specific frequencies. Just like mid-bass, mids, & mid-tweeters.

Andrew
Synesthesia Studios

At 120dB you may not get to support your artist too long, or hear them anyway!

Multiple drivers are simply super hard to integrate as every driver is a slave to what it sounds like and is made from, and the overlap to the drivers above and below is critical to sonic integration. The electronics are probably the easier part.

Playing 120 dB, just about any driver will be seeing near maximum cone excursions, and lots of doppler or intermodulation distortion, too. That is a sound that gets hard to hide, so more driver that are driven less for 120dB, may actually be better, even if they aren't as "like" sounding as the mains on up.

So the answer isn't obvious to me at 120 dB!

I'd be more interested in using multiple distributed subs covering the whole bass spectrum than in using different subs for different portions of the spectrum. The reason is, if you spread multiple low frequency sources around the room, each one will interact with the room's modes differently, and the net result will be a significant smoothing of the bass response throughout the room (of course this is only true down to the lowest room mode, below which we are in the "pressure zone"). Smooth bass = fast bass, tight bass, good pitch definition bass.

As for what type of sub is best, imo the ideal would be a sub whose native response is roughly the inverse of room gain. This can be achieved with ported or passive radiators tuned properly, and approximated with a low-Q sealed box, or achieved with an equalized sealed box.

Duke
dealer/manufacturer

01-10-13: Rower30, I agree that some of my sustained SPL levels are certainly high enough. I am quite aware that my tastes are off pace with the normal:-) And definitely agree that it is very difficult to get everybody to cooperate, all the different subs I mean. I've spent most of my time tuning and keeping the frequency spectrum from having any huge lumps in it. It has worked out a bit, although I've only had a few trusted heads listen to it. Keeping in mind the number of subs, on a single plane, and the timing issues, phasing, and so on. I'd say it's definitely not for the easily discouraged types. Although, since I have so many subs playing together I do benefit from a shared workload. It's probably just as well, my job doesn't go well for people that flinch at loud noises anyway.

01-12-13: Audiokinesis, I have to say if some one wanted to pay me to make this for them..... I wouldn't. I've built and seen sound rooms with multiple distributed subs, and the results are outstanding. Say using four 12" drivers one in each pocket but, not quite in the corners, right? And as far as the right sub/setup, I just don't know. Maybe I just feel like a single source can't operate efficiently at 30hz and 100hz simultaneously.... So perhaps I achieved one goal with my idea there.

Andrew
Synesthesia Studios