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passive subwoofers for rear channels

post #1 of 10
3/24/08 at 1:02pm
Thread Starter 
right now i have 2 nht classic fours and am contemplating buying another 2 for the rear because of the low cost. i heard that eventually they are going to master dvds with lower frequency in rear channels. is having 4 passive subwoofers a good idea? would buying a x2 crossover help at all? should i just buy the classic 3's? thnaks for all your help
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post #2 of 10
3/25/08 at 8:33am

Re: passive subwoofers for rear channels

You are far better off spending the money on a decent powered sub, than more passive ones. There are multiple benefits, the greatest of which is taking the load of delivering power sapping bass off the main amps.
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post #3 of 10
3/25/08 at 12:32pm
Thread Starter 

Re: passive subwoofers for rear channels

Quote:
Originally Posted by JohnRice
You are far better off spending the money on a decent powered sub, than more passive ones. There are multiple benefits, the greatest of which is taking the load of delivering power sapping bass off the main amps.
does this still apply if i already have a powered sub? right now my fours are bi-amped with a cambridge receiver and a parasound 5125 amp. i havent hooked up a crossover yet either. thanks for all your help.
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post #4 of 10
3/25/08 at 7:51pm

Re: passive subwoofers for rear channels

You can't just bi-amp with any mismatched amps you have sitting around. Meaning, sure you will get sound, but the gain of the amps (not to mention other characteristics) won't match and you will end up with an unbalanced system. So, it sounds like you already have at least one powered sub, two passive subs and now you want to add two more passive subs.

This is what I refer to as a "Frankenstein" system. There is really no constructive advice I can give with such an approach.

Possibly someone else will be willing to guide you in the direction you want to go. I think tossing random equipment together like that is ill advised.
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post #5 of 10
3/26/08 at 6:23am

Re: passive subwoofers for rear channels

John gives good advice, and I'd like to add that the positioning of the subs in the same place as the speakers is not the best idea. Speakers are directional because the wavelengths they produce are small. Subs are non-directional due to the large wavelength of the frequencies they output. Having relatively large wavelength sources like subs in multiple placements in the room is just asking for unnatural nulls and peaks where the sound waves intercept, and is going to wreak havoc with the accoustics in the room. Because of this, most enthusiasts encourage 1 very capable sub or co-location of 2 subs. Going above two subs located in different parts of the room requires some sophisticated calibration in order to get a room to sound right. Add more and more subs and you get to the point where the room is just a mess of overlapping nulls and peaks.

My advice is to save your money and get one or two monster powered sub(s) that will fit your needs. Unless your calibration and accoustics in the room are perfect, there is definitely a point of diminishing returns when buying multiple subs.
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post #6 of 10
3/26/08 at 6:48am

Re: passive subwoofers for rear channels

Quote:
Originally Posted by JohnRice
You can't just bi-amp with any mismatched amps you have sitting around. Meaning, sure you will get sound, but the gain of the amps (not to mention other characteristics) won't match and you will end up with an unbalanced system. So, it sounds like you already have at least one powered sub, two passive subs and now you want to add two more passive subs.

This is what I refer to as a "Frankenstein" system. There is really no constructive advice I can give with such an approach.
.

I think it's a matter of terminology. The NHT Classic 4's are essentially full range speakers. You can drive them full range, or you can use an active crossover to drive the 10" woofer separately.
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post #7 of 10
3/26/08 at 8:23am

Re: passive subwoofers for rear channels

Jeremy may be right, but there are still many problems. The term "Sub" gets tossed around a lot. A bi-amped woofer is NOT a sub. Still, you can't bi-amp with just anything sitting around.
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post #8 of 10
3/26/08 at 8:24am

Re: passive subwoofers for rear channels

Quote:
Originally Posted by XXXtraAnchovies
... i heard that eventually they are going to master dvds with lower frequency in rear channels....
Both Jeff and John give very good advice. Reread Jeff’s comments about low frequencies and directionally.

The whole point about subwoofers is that the listener cannot distinguish the location of very low frequencies (in the sub range). It follows that even if there are already low frequencies being delivered to the surround channels and if you had surround speakers capable of reproducing sounds (with full power) down to 20 hz, you still won’t be able (in practical terms) to tell the location of those sounds.

And as a side note, do you have any source for this information?
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post #9 of 10
3/26/08 at 8:39am

Re: passive subwoofers for rear channels

Each of the satellite channels is full range. The (optional) LFE channel provides bass reinforcement. But in a normal system, the lowest octaves are routed to a subwoofer. Now, if you have a DVD-Audio or SACD player, the bass management may be somewhat crude, or missing all together, in which case low frequency drivers all around might seem tempting. Be sure that your room is acoustically perfect.

A better solution might be a preamp that can handle a DSD/Multichannel PCM signal. That is, if you care much about SCD/DVD-A.
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post #10 of 10
3/26/08 at 9:03am
Thread Starter 

Re: passive subwoofers for rear channels

is it in my best interest to get rid of parasound amp and cambridge receiver and buy a nht controller and amp?
"The term "Sub" gets tossed around a lot. A bi-amped woofer is NOT a sub."-john rice
-so if i dont have a sub does jeffs advise still apply?
"And as a side note, do you have any source for this information?"-lew crippen
-i dont have the documentation but rear it on this forum but im not sure of the posters memeber name.
once again i appreciate everyones time and attention to this matter
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