Lot's of questions about subwoofers

[SE-Raider]

One of the subs that I need to build will be in clsoe proximity to my PC, and I don't want to risk problems with stray magnetic fields damaging any data on the hard drives. I had originally intended to use the Dayton RF drivers for this room, but overlooked the shielding issue. What drivers are available that are shielded? Sound quality and low distortion are priorities, and the room is about 12x13. Also, listening levels are low to moderate, and I especially would like sensitivity at low volumes.

Also..............

I am building subs for my home and have been comparing amps. The main contenders are the 500 or 1000 watt plate amps from PE, the Bash amps either PE or Oaudio, or prosound rack amps, either Behringer, QSC, or Crown.

Other than the obvious mounting styles to which I am indifferent, what are the advantages of the rack amps over the plate amps, if any. The plate amps seem to have more signal processing capability, while the rack amps seem to have more power for the dollar.

I would like to keep the cost at $200-400 if possible.

Finally, are the digital class amps as good as the class AB amps sonically? I have heard some assert that thee better damping factor of the digital amps better controls the cone movement.

Thanks for any recommendations or suggestions

[ThomasW]

I don't want to risk problems with stray magnetic fields damaging any data on the hard drives.

Do you understand that the read/write heads on your hard drive have high power magnets on them?

There a very few good shielded subwoofers. And unless you plan on setting the HD on top of the sub, the woofer magnet isn't going to be a problem.

Also, listening levels are low to moderate, and I especially would like sensitivity at low volumes

Low to moderate listening level and sensitivity at low volumes are mutually exclusive give how human hearing works. The bass must be boosted at low SPL because human hearing is less sensitive to bass at low SPL. Google Fletcher-Munson curve for more on this.

You have correctly stated the major differences between plate amps and prosound amps. Chose the one that meets your needs.

Finally, are the digital class amps as good as the class AB amps sonically?

Depends on the amps there are good and bad amps using both topologies

I have heard some assert that thee better damping factor of the digital amps better controls the cone movement.

Again depends on the amp. Generalizations like this are meaningless

[SE-Raider]

Do you understand that the read/write heads on your hard drive have high power magnets on them?

There a very few good shielded subwoofers. And unless you plan on setting the HD on top of the sub, the woofer magnet isn't going to be a problem.

Low to moderate listening level and sensitivity at low volumes are mutually exclusive give how human hearing works. The bass must be boosted at low SPL because human hearing is less sensitive to bass at low SPL. Google Fletcher-Munson curve for more on this.

You have correctly stated the major differences between plate amps and prosound amps. Chose the one that meets your needs.

Depends on the amps there are good and bad amps using both topologies

Again depends on the amp. Generalizations like this are meaningless

I understand that those magnetic heads write to a magnetic media on the drive that I would assume could be damaged by an adjacent and strong magnetic field such a that of a large subwoofer, thus my concern

This is what I am trying to detemine; how much at risk is the media, and is shielding necessary or advisable. I have read some accounts that attribute data corruption on a drive to speaker proximity. Any experience is appreciated.

I am well familiar with Fletcher Munson. Some subwoofers, especially the higher power "superwoofers" are sometimes not linear in response, that is a lot of power must be used before the driver begins to really respond and overcome the resistive forces in the suspension. What I was after was a recommendation on a subwoofer who's response doen't go away at lower levels due to this effect, independent of Fletcher Munson curve.

I wanted to get recommendations on models that represent the best executions of their respective topologies. I am not after generalities, but rather specific experience and recommendations of amps that represent a good value and performance.

So does damping factor affect control of the subwoofer cone, or not? If so I would then think that amps that state a high damping factor (if accurately stated of course) would be more suitable for such an application. Plate amps are usually specifically designed for sub use; prosound amps are designed for full range generally,so would those pro sound amps with a better damping factor be more suitable for subwoofer use or not? Since this is usually emphasized by thepurveyors of digital amps, I am trying to determine how much difference it makes, if any.

I also noticed that you combined my two original threads, one on shielded subs, and one on subwoofer amps, into one thread (certainly your prerogative as moderator). I have very much enjoyed the positive, creative, open, responsive, and fun atmophere here at HTGuide Forum. I have made every effort to be as respectful as possible here, and certainly have no desire to violate any forum rules or offend. I created two threads to keep the information as specific as possible to facilitate later searches. Is this a problem?

Thanks for your responses.

[opt-e]

I am building subs for my home and have been comparing amps. The main contenders are the 500 or 1000 watt plate amps from PE, the Bash amps either PE or Oaudio, or prosound rack amps, either Behringer, QSC, or Crown.

I am also interested in the relative quality of the PE BASH amps compared to the class-AB PE amps.

[ThomasW]

would assume could be damaged by an adjacent and strong magnetic field such a that of a large subwoofer, thus my concern

As I said, unless you plan on setting the hard drive itself on top of the subwoofer cabinet it's not going to be a problem. Maximum PC magazine had some interesting tests regarding the effects of magnets a few issues back.

If remains a concern, line the cabinet with multiple layers of sheet metal (16 gauge or thicker)

Some subwoofers, especially the higher power "superwoofers" are sometimes not linear in response, that is a lot of power must be used before the driver begins to really respond and overcome the resistive forces in the suspension. What I was after was a recommendation on a subwoofer who's response doen't go away at lower levels due to this effect, independent of Fletcher Munson curve.

Fixating on any single aspect of driver design and excluding others isn't the best idea. Cone breakup modes, Le, and other variables are certainly as important as linear suspension operation.

FWIW The PE RS315HR is a very good driver

I wanted to get recommendations on models that represent the best executions of their respective topologies. I am not after generalities, but rather specific experience and recommendations of amps that represent a good value and performance.

For a fan cooled pro-sound amp the Behringer EP series are a best buy. I don't follow plate amps since I consider them to be a poor long term investment

So does damping factor affect control of the subwoofer cone, or not?

Yes and no...this paper will provide the answer to your question.

I created two threads to keep the information as specific as possible to facilitate later searches. Is this a problem?

Starting a new thread for every question tends to clog up the forum.

[Brian Bunge]

I've built probably a dozen or so subs using either the PE 250W amp or the bigger 350W version from Rythimik Audio and as far as I know, no one has ever had a single issue with any of the amps. This includes my dad's big 15" sub powered by the 250W version.

In the last month I completed a sub using the 300W BASH amp and the 10" RS HO driver. It gets some decent pounding almost daily and so far I have not had any problems with it. I must say, though, that the little 13" cube does look funny sitting next to one of my big 3-way towers. But it's the only sub I've got right now so it'll have to work!

[ThomasW]

It was quite late when I posted yesterday so here's some follow up....

What Dick Pierce didn't state directly in the article I linked above, is that damping factor is primarily a small signal (testing level) measurement. So the numbers published in mfgr's spec sheet's bear little relation to how the amp will function with real world (large signal) output levels.

[Dennis H]

The other thing is the published damping factor doesn't include the impedance (resistance) of the speaker wire.

Published damping factor = (8 ohms)/(output impedance of the amp)

Real damping factor = (8 ohms)/(output impedance of the amp + impedance of the wire)

So, even if your amp had an infinite published damping factor (zero output impedance), when you hook it up to a pretty fat wire with an impedance of 0.1 ohm, your real damping factor is suddenly dropped to 80. Use a skinny wire and it's worse yet.

Bottom line, don't sweat published damping factor. SL says anything over 50 is fine.

[---k---]

I've had my RL-p15 driver 8" away from a computer. No problem. Commputer sits on the floor, tv stand is made out of 8" CMU block. I never realized that I stored my driver next to the stand and computer for a month.