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Question about subwoofer design.

post #1 of 8
Thread Starter 
It seems to me that one way that subwoofers are different is that they either use a simple speaker in the box with the box sealed or they do something like the DTS-10s or SVS PB Ultra 13s where they use a path of tubing or panels to extend the distance of the ports or speakers.

Do these different approaches also affect sound quality?
post #2 of 8
Are you about ported vs sealed? The DTS-10 is a tapped horn design that is different from both sealed and ported. I could give a basic description (very basic for the tapped horn), but I don't have much time right now. If no one more experienced than me chimes in, I'll fill you in in a bit. I'm still a baby in understanding all there is, but I'm learning.
post #3 of 8
Thread Starter 
Thanks for responding.

I was just curious if each of these designs had a somewhat unique sound to them such that someone might prefer one over the other. I'm not really thinking sealed vs ported.
post #4 of 8
"I was just curious if each of these designs had a somewhat unique sound to them.."

they do, but once your put them in room, most everything goes out the window.

work back from room and locations to enclosure to driver...

all things equal, there are some things about drivers and enclosures that correlate with subjective performance, but i'm not getting into that debate again.
post #5 of 8
Summations without subjective...here goes

Horn subs, variations are the most efficient at producing bass. How far they extend depends on size mostly.

Ported enclosures are next in line for efficiency, all things being as equal as possible. Can get really low if you've got the space.

Sealed.....least efficient of the big three. Needs lots of power and eQ with long excursion drivers to get real low with authority. Smaller boxes mean more room for multiples.

There's no free lunch with any of these designs....they all have trade offs. You'll need to look elsewhere for subjective sound quality rants as I don't think anyone here wants to do the whole roundabout again. Been there....
post #6 of 8
Thread Starter 
No problem....thanks for posting.
post #7 of 8
A bit on the relationships in efficiency.

Some nuts a bolts.

1.) Every three decibels up or down means a doubling or halving of the electrical power in. As in 3 db louder means it requires twice the power. Three db less requires half the power.

Our hearing is not very acute or able to discern small changes in the low end. So three db increment are about right for what you say is definitely louder.

Another very common misconception.

1000 watts is way louder than 500 watts. Remember the paragraph above? It's three db louder.

More fun with math. One woofer plus one amp = loud.

Two of the same woofers with half the power = the same loudness

Tradeoff? Twice the box size usually.

Myth two. Vented boxes are louder than sealed boxes.

Remember the first paragraph? The difference is three db.

Myth three. Sealed sound cleaner than vented. Boloney! Designed correctly they can sound equally good. It is more a question of the suitability of the woofer to the type of box and the size of the port.

Horns.

Most of the tapped horns on this site have not much greater output than an equivalently sized vented enclosure. Not worth the amount of effort.

There are some exceptions. Those designs are worth the effort.

Front loaded Horns.

They are around on this site and others. Some are very well designed. Most will provide a boost in efficiency around 8 to 10 db. That is very significant because every 10 db sound twice as loud as the level before. A 200watt amp is very loud. In fact it is the loudest enclosure you will get any driver to fit into.

Tradeoff? You want to go low? You gotta go large. Lots of cuts and fooling around.

They also have a very clean sound that a great many people do not like.

They sound like real music. Live acoustic music. If that is your thing then consider it.

If this is your first box and you are looking to get your feet wet. Then a sealed or vented enclosure is an easy path. Choose the right driver and some of the more exotic boxes can be project number two.

Mark
post #8 of 8
Quote:
Originally Posted by mwmkravchenko View Post

Front loaded Horns.***
Tradeoff? You want to go low? You gotta go large. Lots of cuts and fooling around.

Also, limited bandwidth. Don't forget about that. A 4th order bandpass ("front loaded horn") that has significant output at 20Hz isn't going to be worth anything at 100Hz...

The best way to look at different enclosure types is as an efficiency vs. bandwidth tradeoff.

There's no "better," really. Just the set of tradeoffs that matter to an individual.

Monopole Bass
Sealed:
generally smallest, more tolerant of driver production variance, air spring protects driver to some degree, can pressurize a room below cutoff (stays a monopole), attenuates mechanical noise from driver best (important for extremely long-throw drivers; the only ones I've played with that are dead quiet at long throws are Aurasound's, and they're expensive when they're available) 2d order low-end rolloff makes them easier to integrate with subs (for mains)
BUT
less efficient than anything else listed except for OB, and requires the most excursion for a given output within its passband.

I-B:
same as sealed generally, except invisible in the room and no airspring, BUT sound leakage is a serious (to me disqualifying) issue. Also, one should generally own the structure; renters need not apply.

4th order BP/"front-loaded horn":
more efficient than sealed in the passband, airspring protects driver to some extent, lower distortion because the coupling chamber filters distortion products acoustically, like a closed box stay monopole below cutoff so can pressurize a room down low
BUT
bigger than sealed, larger, upper bandwidth limitations may be an issue with many drivers in many systems (they're generally only good over about 2 octaves), often severe port resonance issues if one uses vents instead of a passive radiator, and they're a lot more sensitive to unit-unit variance in driver parameters.

Hybrid Monopole/Dipole Bass
Vented/"transmission line":
generally larger than sealed (given same woofer), considerably higher efficiency at the bottom of their passband (nearly equivalent to quadrupling amp power), requires lower excursion for a given LF level.
BUT
typical dipole problems down low (don't pressurize a room below cutoff, excursion goes way up below cutoff, leading to overall higher distortion if one doesn't employ a suitable highpass filter), more sensitive to parameter variations than sealed, excursion rises quite a bit just above tuning, pipe resonances from the vents are audible and deleterious (especially with very low tunings)

PR:
vented without the port resonance issues BUT add cost and if they the PR's don't have enough displacement can result in nasty sounds and/or parts destruction

6th order bandpass/"tapped horn"
more efficient than vented systems
BUT
typical dipole issues and larger, severely reduced bandwidth, often massive out-of-band resonances

Dipole bass
often reach similar levels of smoothness in the upper bass with fewer units required than systems that are monopole in that region
BUT
least efficient, placement requirements make them impracticable in many rooms, LF cutoff often quite high.

All that said, the best bass is any one of the above (assuming sufficient bandwidth on the bottom and on the top), with enough of them used (and properly set up, with control each unit's individual level, delay/phase, and arguably though less important than the above, EQ.) Any single bass unit is going to lead to (to me) unacceptable variance in the room's modal region, unless the room is arena-sized.

For me, in a given system the choice will be between multiple sealed, 4th order BP, or PR subs, with the choice between sealed/PR and BP down to size constraints and the choice between sealed/PR based on available driver displacement and amplifier power.
I strongly prefer sealed mains speakers, because they are easiest to integrate with subwoofers.
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