Subwoofer design

 

Anonymous
I have a 15" rear ported,passive subwoofer that I am using from 20-80 Hz. The box is placed directly on the floor. How will the sound change if I put small 3" feet on it?
 

Anonymous
sound will not change weather it is directly on the ground or 3 inches above the ground. The human brain can not tell where low frequencies such as 20-80 Hz are coming from. This is why speaker designers have made subwoofers because they make it so that the satallite speakers can carry out the high frequencies while the subwoofer carries out the low frequencies. In turn this makes for smaller satallites and a subwoofer that can be place anywhere, even behind the couch with the same sound effects as if the bass where coming directly out of the sattalites themselves
 

Ric Smith
Actually adding feet will help with the sound. I've seen from experience that getting the box off the floor will make the base sound cleaner by isolating the surface area contact. This is why you see most high end subs come with floor spikes.
 

Jon
Hmmm... my brain can tell where bass frequencies are coming from. They are not omnidirectional as people claim. Anyone can tell if a subwoofer is slightly left of the center or anywhere else, especially above 20Hz.
 

timn8ter
Well Jon, you're an anomoly because years of psychoacoustic research says otherwise. Are you sure you're hearing the 20 Hz frequency or something else? I believe floor spikes are meant to reduce vibration and movement of the sub on carpeting. Legs for subs are most often seen on downfiring subs for obvious reasons. Downfiring subs are desirable for their asthetics not because it sounds any better. Low frequencies are omni-directional and most affected by room placement more than anything else.
 

G-Man
I have owned both downfiring and front-firing self-powered subwoofers. I agree with the second "anonymous" letter. I can't tell where the low frequencies are coming from and neither have the over 50 people I have had over to my house listening to DVD's and music. As long as the placement of the subwoofer is sonically beneficial--in other words, not in spot that causes booming or thin sound, it is nigh impossible to tell where it is coming from if you are seated in normal listening positions. And self-powered subwoofers are the only way to go if you want good sound at a reasonable price. Otherwise, you need to get a bunch of huge tower or floor standing speakers that have big sub-woofers that are well damped and well made. Even Definitive Technology in their floor speakers generally makes them with self-powered subwoofers in the tower.
 

TAUDIO
I HAVE THE SAME QUESTION ABOUT THE VELODYNE VX-10.WILL PUTTING SPIKES UNDER IT MAKE IT TIGHTER SOUNDING WHEN PLACED ON CARPET?IF SO,WHERE CAN I GET SPIKES?SOUND ADVICE DOESN'T CARRY THEM {I'M IN FLORIDA}.COULD I DRILL AND TAP THE SUB AND JUST SCREW IN SOME STUDS SHARPENED ON THE FLOOR END?THANKS IN ADVANCE
 

G-Man
Spikes are usually important in narrow tower speakers that can be knocked over easily. Most self-powered subwoofers are short and quite heavy. If your subwoofer sounds "mushy" or "loose" on the low-end then it is either being driven too hard for its capabilities and/or you need to place it closer to a corner to let the subwoofer generate sounds more easily.

The location in which your subwoofer is installed can have a dramatic effect on its'performance. In fact, "placement effects" generally dominate the low frequency response shape. Locating the subwoofer near the corner of a wall will increase the subwoofer output and extend the low frequency response. However, be aware that while this can be a "free lunch", it is often at the expense of increasing the magnitude of resonances in the room.

It is always good to have a Radio Shack $40 SPL Meter to balance your speaker system and the subwoofer to where you usually sit. I have gone over to various friends houses and done this for them and every one of them couldn't believe the dramatic difference in sound quality and balance when speakers are properly placed and "dialed" in.
 

TAUDIO
Thanks G-Man!I was considering placement problems.Sub is centered on a long wall of a 12x18 ft. room(side wall).Also, could my cheap sub cable be part of the problem?About 5 ft. of the 25ft. is rolled-up in the corner.Receiver sub level is set at 3 and sub volume is at about 3.5 of 10.We're moving to a house with wall to wall carpet(sub sits on a 1/4" thick area rug now).I think I'll have more placement options there.I'm pretty limited here!System is:Marantz SR5300,Paradigm Atoms,CC-170,ADP-70,and the VX-10.Sounds great except for the SLIGHTLY loose and misplaced bass.I've only had it about 2 months(after 2 years of "research")Thanks again!I'm sure I'll be posting again soon ,but now I have to go to work.
 

G-Man
Good luck on your move. I guess you should see how your set-up performs in your new location before doing anything dramatic. That said, I do recommend getting a Radio Shack SPL Meter for $40 to balance the system.
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