sealed vs vented subwoofers

You cannot ruin the lower midrange with a sub if you cross it over properly and run it at the proper level. Many people expect the sub to take the place of the woofer in their main system. I use them as a SUB woofer, to add bass below the level of the woofer in the main speaker. I do not run the signal from the preamp through the sub back to the main amp. I have 4 pairs of subs , 3 are ported and they all work well. My RELs are ported and I do not know of a sealed box woofer near their price that I would consider their equal. To issue broad decelerations that one type of design is better than another is almost always wrong. Over the last 30 years I have had a number of excellent speakers and most, maybe all, were ported.

Full flared ports reduce the noise problems with ported designs. I would say both can be made into fine subwoofers. Still for the ultimate in bass for music or HT a bass horn, massive OB design or bass tower sounds best. But they are large costly why most folks purchase affordable subwoofer designs. To me the total design of a subwoofer is flawed from the start designed more for WAF and profits. Less for ultimate perfromance. I would say most loudspeaker designs also fall into this.

To issue broad decelerations that one type of design
is better than another is almost always wrong.

It is simple physics. Sealed enclosures tend to produce tight, accurate bass
with a flatter frequency response curve. They are also generally the enclosure
of choice when looking for sound quality. Ported designs are more efficient
and give you more SPL output - they are generally the choice for higher
output when sound quality is less important. I explained why above but I'll try
further. More technically speaking it has to do with system Q....a ported
design tends to have much higher Q (underdamped) than compared to a
sealed design, again this is physics - the sealed box acts like a shock
absorber and dampens the movement of the cone - this makes the woofer
stop quickly when the power is removed whilst a ported design will just
waffle around even when power is removed. (Of course you have very sloppy
ported subwoofers with port tuned at 40 Hz and much better sounding ones
like the one I showed in the link above which can be tuned at 10, 15 or 20
Hz. Nevertheless, in a sub, the ported designs are always sloppier (higher Q)
than sealed - although a 10 HZ tune will have much better sound quality than
a 20 Hz tune)

You cannot ruin the lower midrange with a sub if you
cross it over properly and run it at the proper level

I guess it depends on your perspective. Most subwoofers typically add 20%
harmonic distortion anyway. There are some measurements on REL
subwoofers on the HT Shack website - so you can compare their
performance to other subwoofers.

Thanks gents for all of your replies. That helps a great deal. Makes sense. Appreciate it!!

A sealed box will have more group delay than a vented box because it has a 4th order rolloff below system resonance, rather than the approximately 2nd order rolloff of a venteed box. However, the audibility of group delay at low frequencies has not been not firmly established, and recent studies indicate that it is marginal at best with music rather than test tones.

On the other hand, frequency response has been well established to be audible. That's why I focus on the frequency response rather than the group delay or system damping.

The reason for the above two observations lies in the human hearing mechanism. Briefly, at low frequencies the ear is very poor at resolving timing, and much better at resolving intensity.

On another subject, note that the woofer is powered throughout its stroke; it doesn't rely upon the airspring in the cabinet to restore it to rest position.

A relevant comment by Earl Geddes: "Remember that the damping and the frequency response are one and the same thing. If I correct the frequency response then I am simultaneously correcting the damping."

http://www.diyaudio.com/forums/showthread.php?postid=1638754#post1638754

The implication of Earl's statement is that we can focus on the in-room frequency response curve, and when we get it right we have also gotten the system damping right. Focusing on the system damping isn't wrong, as it will theoretically lead to the same result, but in my opinion it's easier to correct the frequency response.

Once while in an exerimental mode I built roughly comparable sealed and vented subwoofer enclosures. The enclosures were the same size and almost the same efficiency. The sealed box used a 10" woofer with a Qtc = .50, and the vented box used a 6.5" woofer and was tuned to give a roughly room-gain-complementary response.

Subjectively, the vented box went deeper and would play louder before audible distortion set in (the latter surprised me). The sealed box had better impact in kickdrum, while the vented box sounded more natural on other bass instruments.

Suspecting that the difference on kickdrum might be related to the larger, more powerful woofer in the sealed box, I switched to an 8" woofer (with a magnet system comparable to the 10" unit) for the vented box. This substantially narrowed the gap on kickdrum but did not eliminate it entirely. By now the two boxes were also approximately the same cost, as the 8" woofer plus vent was close to the same cost as the 10" woofer.

I'm not saying this was a definitive series of tests, and my blind listening panel was pretty small (one person, whose assessments I agreed with). I came away with the conclusion that the cost-no-object approach would be an equalized sealed box with very large-displacement woofers, but that the more cost-effective approach was the low-tuned vented box (which in both cases souned better on everything other than kickdrum).

Duke