different subs, different sounds?

[BC Dave]

Here's a question that might generate some discussion and controversy. I frequently have read about how one forumer replaced a powered sub with another and was "blown away" by the difference. Sure, listening to a movie clip of a building exploding probably will reveal big differences in room-shaking prowess between two subs, especially if you are replacing an eight-inch sub with a big SVS or HSU, but here's my question. If listening to music like jazz with stand-up or electric bass, and both subs were operating without distress (like amp clipping or driver overexcursion), do you believe there would be a world of difference in their "sound quality?" I recall reading some Tom Nousaine shootouts in the past where he said the subs he was comparing sounded virtually identical when reproducing electric bass at moderate volumes. I tend to think one could swap out a sub for a lesser model (not a POS, but a reasonable unit) under those low-demand conditions and a blindfolded owner wouldn't notice any difference. Any thoughts?

[jasmit]

I really don't have a lot of experience with subs, so I can't comment on them particularly. I can say this -- it seems that an inordinate number of audiophiles are given to hyperbole. It is not uncommon on fora such as this to read that this receiver will "blow" that receiver "out of the water," or that these speakers "demolish" those speakers. It's the same thing with amplifiers and receivers. While I'm not a subjectivist, I will concede that it's possible that someone with a lot of audio experience and extremely good hearing might, and I emphasize might, detect an audible difference in two amplifiers. But when I read that they heard "night and day" differences, I roll my eyes.

[Woochifer]

With subwoofers, the lower you go in the frequency range, the more the bass is affected by the room dimensions and the acoustics. The biggest "night and day" differences that you will detect with subwoofers occur when you listen to a subwoofer in a different room or reposition it within the same room. If two subwoofers (under anecholic conditions) measure similarly, then what you hear will be far more influenced by the room than anything having to do with the subwoofer itself.

Anemic or boomy sounding bass is often created by low frequency wave interactions that alternately amplify or cancel out at specific frequency intervals. Switching out the subwoofer with another one at an identical location will not overcome any issues created by the room. This is because the room dimensions are typically much shorter than the bass wavelengths.

With this in mind, the best improvement you can make with a subwoofer is to properly place it within the room so that the location gives you the fullest and most even sounding bass from your listening position. Keep in mind that the bass will sound different at different locations within the room. You can also improve the bass by measuring the in-room frequency response. After identifying the largest room-induced peaks, you use a parametric equalizer to dial down those frequencies. That allows you to more set the subwoofer at a more realistic level and better take advantage of the subwoofer's capabilities without the room hindering the performance.

As far as whether or not to upgrade the subwoofer. If the new subwoofer extends the frequency response by a half octave or more, then it does make a huge difference in what you hear, even with music. With acoustic bass, the fullness of the notes and the harmonics are better captured with a more capable subwoofer. Another aspect to watch out for is how differently ported and sealed subwoofers roll off at the low end. Switching between those types of subs will result in very different sound characteristics.

Ported subs are more difficult to design properly, but they are more efficient. At the low end, they drop off more suddenly, but can maintain a more linear bass until that dropoff point. Ported subs also have more variation in their tonal characteristics because the response curve is dictated by a precise relationship between the box volume, the driver specs, and the diameter of the port opening. Generally, ported subs work best in larger rooms.

Sealed subs are less efficient, but they have quicker transient response and drop off more gradually at the low end. However, the bass dropoff does occur sooner. Sealed subs have somewhat less variation in their tonal characteristics because there's no port opening to match with the driver specs and cabinet volume. In a smaller room, sealed subs can actually have more extended bass because the room will reinforce the bass at roughly the same rate as it drops off.

[kexodusc]

I would add a few points for discussion though.


Ported subs are more difficult to design properly, but they are more efficient. .

This is actually quite debatable, a good sealed sub requires more work in the design stage and less in the building stage in my opinion....Ported subs are more forgiving to woofer selection and cabinet volume, and generally provide easier pathways to reaching goals for frequency response, power handling, price, etc. You have to be quite careful with powerhandling when designing a sealed sub, more so than a more full-range speaker system.

Ported subs do have that extra step in determining port tuning and installing.

As far as differences in sound quality, Wooch already mentioned the benefits to adding more response, and of course, room interactions.

The more experimenting and measurments I take , I'm more and more convinced sealed subs and woofers with lower excursion are the way to go in terms of sound quality. Lower excursion in a ported sub especially, as transient response is already relatively poor.

Note that the start to start-to-stop time of oscillation of a woofer in a sealed enclosure is around 4 times faster than it is in a ported enclosure. This means faster response and far less overhang (continuing to play frequencies after the signal has ended). Basically, ported subs are sloppier in nature.

Better quality woofers in a ported enclosure can also see improvements in this area, though at a much smaller scale. But when combined with increased power handling, and more bass extension, it's easy to see why people can determine one sub "blows away" another.

Finally, I'll argue that when you get below 30 Hz, even 2 or 3 Hz more extension is an aweful lot of bass. Depending on your tastes in movies or music, it can come into play quite a bit.




I have to admit

[Woochifer]

This is actually quite debatable, a good sealed sub requires more work in the design stage and less in the building stage in my opinion....Ported subs are more forgiving to woofer selection and cabinet volume, and generally provide easier pathways to reaching goals for frequency response, power handling, price, etc. You have to be quite careful with powerhandling when designing a sealed sub, more so than a more full-range speaker system.

Ported subs do have that extra step in determining port tuning and installing.

I was referring to the port tuning when I mentioned that ported speakers are more difficult to design properly. It's another parameter to account for, and another measure that has to be matched to the driver characteristics and the interior volume. My understanding is that if the interior dimensions are less than exact, a sealed sub is a lot more forgiving in that respect. (you might be right in that this is at the building stage)

You are right about the woofer selection and power handling, but a ported sub also necessitates some sort of rumble filter given that once you go below the tuned frequency, then the woofer excursion goes way up since the back pressure that dampens the driver movement above the tuned frequency is no longer present.

[poneal]

Why buy a subwoofer when you want music to sound good through it. What you really need is a very nice musical woofer that can play low. Subs are usually made with HT in mind to get the earth shaking t-rex stomp. These subs usually sound horrible with music. A good 8" or 10" music woofer that plays down to mid or high 20hz region will usually stomp a HT sub when it comes to music. This is why many people are disappointed after buying a sub. It didn't help there music any. Regards, Paul