I'm looking at subs and I've found several that I like. I'm looking at a class D amp that is 1250w RMS @ 1-ohm (and is stable there), so I'm looking for two 12" subs that are 4 ohm DVC so I can run a 1-ohm load.
First, is it cool to split a one-channel amp four ways to get the 1-ohm load?
The main question is, in situations where its not listed, how do I tell if it will sound good in a sealed box? Some places like Crutchfield say "this sub sounds best in ported or bandpass enclosures."
I'm looking specifically at Audiobahn High Excursion 12" AW1200X. Zeb has them as 2001 closeouts for $99. Its frustrating because they don't list many T/S parameters, neither does the Audiobahn website. They don't even tell me the actual wattage, it just says 700w. Is that max per coil? max per unit? RMS per unit? I like the numbers I can see.....
Replies (6)
ttocs on 12/16/2003 16:13:34
which amp is it? Just asking as some companies advertise one thing, but put out another.
Best way to find the sub you like is to listen to it. Numbers are numbers are numbers and manufacturers seem to put whatever they feel like for them sometimes... Just because the numbers look good does not make the sub sound good.
curtis73 on 12/16/2003 21:52:55
Its a US Acoustics. I'm also looking at a 2000 RMS Audiobahn, but they're rated at 17v. The USacoustics is rated at 12.9.
I always heard bad things about USacoustics until I came here. So I checked them out and it seems to be a good piece without any frilly crap.
I guess I'm wondering, are there certain characteristics that might make one sub maybe perform better? I do listen to alot of subs, but they are in stereo stores where they're all in pre-fab boxes and the drivers don't seal to the carpet so they leak, and they're all crossed over at the same frequency...yadda yadda. Short of building the box I want and buying 50 subs to try, are there visual or numerical clues? Am I over analyzing? Just do it and shut up right? :)
cplkittle on 12/17/2003 08:40:49
The box is the most important part of your whole sub setup. A good box will make any sub sound good. as far as recommendations concerning whether it sounds better in a sealed or ported box, it gets pretty techincal (T/S parameters).
Basically it depends on what you want.. punch-go sealed; lower bass-go ported.
The easiest way to determine the proper box is to use the Efficiency Bandwidth Product or EPB for short. Here is the equation:
EBP = Fs / Qes
50 or less = best used in a sealed enclosure.
50 - 90 = flexible enclosure options.
90 or greater = best used in ported enclosure.
pros and cons
SEALED BOXES
advantages:
tighter, more accurate response
no need for subsonic filtering due to air suspension prohibiting lower frequencies.
less likely to bottom out.
best for rock, pop, or classical
disadvantages:
cutoff rate is about 12/dB per octave. Higher Q's result in sharper rolloff (up to 16/dB per octave) recommended Q of 0.5-1.5 (0.7 optimal)
F3 is normally high (above 30Hz)
3dB less efficient than ported enclosures
lower SPL
PORTED BOXES:
advantages:
deeper more powerful bass
3dB gain over sealed enclosures
Higher SPL capabilities
disadvantages:
larger enclosure size
bottoming out more likely
less accurate bass
need for subsonic filtering
curtis73 on 12/17/2003 14:20:38
That's exactly what I needed to know. One last question, I'm I correct in assuming that the F3 number is that 3dB-down frequency, right?
cplkittle on 12/17/2003 15:29:45
yes
for a good reference and explination of T/S parameters, go to:
http://www.mtxaudio.com/caraudio/education/glossary.cfm
a good link for formulas and alot of other useful information is at:
http://diyaudiocorner.tripod.com/formula.htm
Swez on 12/22/2003 22:35:57
Very good dialogue here! And yes, the numbers printed by some Mfg's aren't worth the paper they print them on. Knowing who plays square and who plays numvber games is the key. Bahn rates at RMS both coils for subs and RMS numbers on amps but at what voltage input??? Dunno
US Acoustics is a solid, no frills amp. Does a good job, rated at 12.9 volts (where others go 13.5 - 14.4 volts) Same with JBL... 12.9 volts but also a basic, no frills amp, but a very good value and performer too.
CPL covered the enclosure aspects well about sub systems. The box is indeed the main factor in performance of any sub made. Generic boxes may do OK for the average noise maker, but if you want accurate, deep bass.... there is no substitute for a sub/enclosure that are well matched to the application. (power handling, frequency response and SPL/SQ)
Swez
First, is it cool to split a one-channel amp four ways to get the 1-ohm load?
The main question is, in situations where its not listed, how do I tell if it will sound good in a sealed box? Some places like Crutchfield say "this sub sounds best in ported or bandpass enclosures."
I'm looking specifically at Audiobahn High Excursion 12" AW1200X. Zeb has them as 2001 closeouts for $99. Its frustrating because they don't list many T/S parameters, neither does the Audiobahn website. They don't even tell me the actual wattage, it just says 700w. Is that max per coil? max per unit? RMS per unit? I like the numbers I can see.....
Replies (6)
ttocs on 12/16/2003 16:13:34
which amp is it? Just asking as some companies advertise one thing, but put out another.
Best way to find the sub you like is to listen to it. Numbers are numbers are numbers and manufacturers seem to put whatever they feel like for them sometimes... Just because the numbers look good does not make the sub sound good.
curtis73 on 12/16/2003 21:52:55
Its a US Acoustics. I'm also looking at a 2000 RMS Audiobahn, but they're rated at 17v. The USacoustics is rated at 12.9.
I always heard bad things about USacoustics until I came here. So I checked them out and it seems to be a good piece without any frilly crap.
I guess I'm wondering, are there certain characteristics that might make one sub maybe perform better? I do listen to alot of subs, but they are in stereo stores where they're all in pre-fab boxes and the drivers don't seal to the carpet so they leak, and they're all crossed over at the same frequency...yadda yadda. Short of building the box I want and buying 50 subs to try, are there visual or numerical clues? Am I over analyzing? Just do it and shut up right? :)
cplkittle on 12/17/2003 08:40:49
The box is the most important part of your whole sub setup. A good box will make any sub sound good. as far as recommendations concerning whether it sounds better in a sealed or ported box, it gets pretty techincal (T/S parameters).
Basically it depends on what you want.. punch-go sealed; lower bass-go ported.
The easiest way to determine the proper box is to use the Efficiency Bandwidth Product or EPB for short. Here is the equation:
EBP = Fs / Qes
50 or less = best used in a sealed enclosure.
50 - 90 = flexible enclosure options.
90 or greater = best used in ported enclosure.
pros and cons
SEALED BOXES
advantages:
tighter, more accurate response
no need for subsonic filtering due to air suspension prohibiting lower frequencies.
less likely to bottom out.
best for rock, pop, or classical
disadvantages:
cutoff rate is about 12/dB per octave. Higher Q's result in sharper rolloff (up to 16/dB per octave) recommended Q of 0.5-1.5 (0.7 optimal)
F3 is normally high (above 30Hz)
3dB less efficient than ported enclosures
lower SPL
PORTED BOXES:
advantages:
deeper more powerful bass
3dB gain over sealed enclosures
Higher SPL capabilities
disadvantages:
larger enclosure size
bottoming out more likely
less accurate bass
need for subsonic filtering
curtis73 on 12/17/2003 14:20:38
That's exactly what I needed to know. One last question, I'm I correct in assuming that the F3 number is that 3dB-down frequency, right?
cplkittle on 12/17/2003 15:29:45
yes
for a good reference and explination of T/S parameters, go to:
http://www.mtxaudio.com/caraudio/education/glossary.cfm
a good link for formulas and alot of other useful information is at:
http://diyaudiocorner.tripod.com/formula.htm
Swez on 12/22/2003 22:35:57
Very good dialogue here! And yes, the numbers printed by some Mfg's aren't worth the paper they print them on. Knowing who plays square and who plays numvber games is the key. Bahn rates at RMS both coils for subs and RMS numbers on amps but at what voltage input??? Dunno
US Acoustics is a solid, no frills amp. Does a good job, rated at 12.9 volts (where others go 13.5 - 14.4 volts) Same with JBL... 12.9 volts but also a basic, no frills amp, but a very good value and performer too.
CPL covered the enclosure aspects well about sub systems. The box is indeed the main factor in performance of any sub made. Generic boxes may do OK for the average noise maker, but if you want accurate, deep bass.... there is no substitute for a sub/enclosure that are well matched to the application. (power handling, frequency response and SPL/SQ)
Swez
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