ok this has sort of been touched on in the past from what i have seen but i was thinking today. if you had 2 subs lets say 2 12" alpine type r's could you put them both in differnt sized inclosures as in one in a .7 cu. ft. and one in a 1 cu. ft. and that way get tight punchy bass from one and mroe low end from the other? or would they cancel each other out. or could you even seperate them like have one do 30-50hz and the other one 50-100hz? so they wouldnt cancel each other out. i'm sure there is a reason you dont see people doing this but i wasw just curious as to why.
Replies (19)
swez on 05/2/2004 13:47:59
Yes, that can be done. The change in enclosure size will make each sub perform a bit different.
The smaller enclosure will net punchy bass near 50-70 Hz naturally. The larger chamber will net better low end response in the lower octave of low bass. (35-70 Hz.)
If you used a 2 channel amp with dual LPF, this would be even easier to get that effect. A small amount of bass boost in the low end sub will help and some careful tweaking... should work well.
Swez
ttocs on 05/2/2004 14:21:08
there will be cancellation when you do this however.
swez on 05/2/2004 19:08:12
Can you explain that a bit ttocks? I'm not sure I get the full picture on cancellations here.
Swez
cplkittle on 05/2/2004 21:31:42
The reason people don't do that in my opinion is becuase there will be too large of a peak in volume where the two overlap. If one performs well from 30-80 Hz, and the other from 60-120Hz, that overlap from 60-80 would be almost twice as loud as the other frequencies. Thus making it sound like a poorly constructed bandpass box. When both subs can perform well from 30-100Hz anyway, why would you want to seperate them?
I have learned from playing around in the shop that deeper bass can be achieved without any trade offs, by using an acoustic coupled box (both subs sharing the same airspace). two 12" subs sharing a 2 cubic ft box both get the back pressure required to prevent over excursion, and at the same time they gain some characteristics of a single sub in a larger box. I tested some eclipse 10's that we had in the shop already in an acoustic coupling box and I built 2 sealed boxes, one for each. I didn't have to break out the meter for this one, the difference was obvious. There were no differences in the higher tones, but a significant difference in the low end frequencies. Maybe this would be a better consideration for you.
saintanddolphin on 05/2/2004 21:55:15
hey kittle? would you suggest using a shared chamber design or sealed for sq applications?
Are there considerations to be made for shared chamber design?
Thanks
Mike
ttocs on 05/2/2004 22:34:57
I just had my answer typed when I read it, thought about it, and knew it was wrong. Let me dig and see if I can find something that explains what I think I might have been thinking.........
uochronos on 05/2/2004 22:44:17
well i dont plan to actualy do this now i was just curious.
and i assumed there would be cancelation or boost like kittle said just wasnt sure exactly how. but like i said couldnt you seperate the frequencies so there would be no bnoost or cancelation like i said 30-60hz for the bigger box and 60-100hz for the smaller enclosure. wouldnt this net each one louder where it sounded best? bhas anyone actualy ever heard a set up like this. like i said i dont plan to do this i just want to knopw why its not done really.
swez on 05/3/2004 00:24:58
Actually, this concept is done to some degree in Pro applications, all the time. They are separate enclosures and different drivers and amped and EQ's to blend. But yes, it does work.
Eample:
18" subs are used in very large ported enclosures (scoop, folded horn and ported designs are common)
12-15" subs are used for midbass punch (folded horns, ported or sealed)
8 -10" drivers are used for low midrange (ported or sealed)
Midrange horns for upper mids & highs
Tweeters for highs
Time alignment and active crossovers, Active EQ or Parametric EQ control the peaks and dips and delay lines control time frame were all sounds meet at the same time in a given target location.
This is especially true in large venuea applications like Stadiums, large Churches and the like.
Swez
cplkittle on 05/4/2004 08:11:21
Mike,
I haven't read much into it, but I will, I only know what I have seen and heard. The only drawback is that if one sub goes, the other one will soon follow as it changes the pressure inside the box. The Diamond Denali display that came by here a couple of months ago was hitting in the 170's with three 12's in a shared ported enclosure. I will do some research on the acoustics of this type of enclosure.
cplkittle on 05/4/2004 08:39:39
This is the only thing I can find right now.. look at the bottom of the page....
http://www.danmarx.org/audioinnovation/theories.html
swez on 05/4/2004 13:50:32
Have a look at this commentary:
http://p205.ezboard.com/fcaraudioknowledgefrm7.showMessage?topicID=40.topic
WHAT HAPPENS IF 1 SUB DIES IN A SHARED ENCLOSURE?
OK folks, we have some pretty sharp thinkers here and perhaps a little reality check (POP QUIZ) might be fun and interesting as well. Here's the scenario below. What do YOU think might happen if:
THE SCENARIO:
1. have a 1200 watt (RMS) Sub amp (Class D mono amp, good for 1 & 2 ohm loads)
2. using 3 modest subs, in a sealed enclosure of proper internal dimensions
3. box does not have internal divider boards
4. subs are 300 watts RMS power ratings and 8 ohm SVC type subs
5. subs are wired all parallel for a 2.66 ohms load.
THE PROBLEM:
One sub blows a voice coil. This sub makes a few weird noises, might smell something cooking (burnt wires, plastic etc.) and then, one sub stops working. Now, we only have 2 subs that work... what happend here and what may happen to the other subs and amp in this system next?
Failure modes noted:
1. Fried Voice coil (charred and smells burnt)
2. Voice coil lead, has pulled away from the voice coil connection at woofer cone (tinsel lead separation) No eletrical connection between wire terminations to coice coil
WHY DID THE SUB FAIL?
HOW WILL THIS EVENT EFFECT THE ENTIRE BASS SYSTEM NOW?
WHAT'S IS/ARE THE PROPER FIX(ES) IN THIS SCENARIO?
Let's hear the comments and kick this one around a bit. Is a real-life scenario and can happen to anyone. OK, what do you all think is going on here and why?
OK, that's the problem, what are the issues and solutions to fix this one?
Swez
If it ain't broke, you're not trying hard enough
cplkittle on 05/4/2004 15:13:58
Most subs have at least a one year warranty.
Most subs don't just blow unless you are doing something wrong.
If one blows out of three, more than likely the other two are going to go soon as well whether they are seperated or in the same enclosure due to increased power from the amplifier. If the amp dosen't fry first from too low or too high an Ohm load depending on how the subs were wired.
If one goes you will know it.. check out the problem asap.
From the scenario listed above, if you have three SVC subs wired in parallel, and one goes, the other two should be safe. You do have an airspace gain, but at the same time you have a ohm gain as well.. going from 2.66 to 4 ohms, this is a decrease in power to each sub somewhat equivalent to what would be recommended for the airspace change. (gain of 1.5x airspace, loss of 33% power).
swez on 05/4/2004 18:10:58
Kit,
Very good link on enclosure designs. Not for the novice enclosure builder once past single vented enclosures, but a good advanced primer for those who like to explore and tinker with lesser known designs.
Thanks for the FYI !
Swez
Tinker18 on 05/4/2004 20:14:31
ok the subs are 300 rms, lets just say you are using a jbl-bp1200.1 for the amp, @ a 2.66 ohm load. that means @1200 rms to 3 subs you would have 400 going to each sub right? and if one blew, and changed the load to 4 ohms, you would only have 600 rms x1, so 300 rms to each sub, but you still have an enclosure gain of 33% correct? lets just say the box is 3 cu. feet @ 1 cu. foot per sub max sealed. this means, assuming im correct about the above, that you are now at the recomended rms rating for each sub, but have gained a cu foot in internal air volume. so each sub is operating in a bigger box than recomended. Which in the long run, could damage the other subs. im not sure about how the sub would have failed unless maybe it was overexcursion because of too much power, or maybe too much clipping or distortion in the speakers, but i think it is a combination of both overexcursion and too much power to each sub. the 400 rms to each sub fried to voice coil, and caused it to overexcur.(not sure thats a word). as for the long term effects on the other subs, i don't think the voice coil would fry, because your at the recomended rms, but i think that each sub would overexcur because of the increase in airspace not inteded for it to be used in.-note::::im not real sure about any of this, i just figured i'd take a stab at what i thought might be wrong.
saintanddolphin on 05/4/2004 20:57:40
That is a great link Kittle.You should add it to the CK list.
I am obsessed with car audio these days and and enjoy being educated here daily.Sometimes I dont even log in just because I like the anonymity(internal personality issues I guess..LOL).
I havent been this interested in one field(including my career) since highschool.
Reading these posts has reminded me of how fortunate we all are to live in a society that not only accepts but demands personal diversity for the continued evolution of the human spirit.
The Golds that are sharing insight on this topic share two impotant qaulities.They are perfectionists and they are instructors.
I know some will say this is off topic and some will say cheesy but it is what I was thinking this moment and therfore to me it is relavent.
Thanks chronus for stirring the pot.
Mike COFFEE
Tinker18 on 05/4/2004 21:29:49
someone tell me if i was even close to swez question?
uochronos on 05/4/2004 22:44:32
your post seemed pretty accurate tinker other then the subs where not each getting 400watts rms since it was a 2.66 ohm load each sub was getting just over 300watts soemthing like 325-350watts each... i would personaly cant think of a reason one sub would go out other then a manufactueres error on the sub or some other variable i'am missing.
swez on 05/5/2004 07:57:42
Very good analysis guys... the THINK ing caps are on and working well. :~)
In this case, the subs were getting a tad over 300 RMS each, but the guy used too much bass boost and over excursion caused the tinsel lead to break and constant clipping, caused the VC to char as well.
The 2 remaining subs are now a net 4 ohms and getting ~300 RMS per sub. However, the shared enclosure is now netting a 1.5 cf airspace to each sub. If he turned down the bass boost and gain, the subs should be OK as they can handle the new power output thermally, but the risk of over-excursion is still possible.
Finally, the failure mode of the one sub was due to clipping and over-excursion. He used too much bass boost and had the amp gain set wrong. This caused the amp to clip (a lot) at high SPL levels which fried the sub. He eventually got the gain and bass boost set properly and the two remaining subs were fine. The blown sub was covered by warranty and replaced. Now, all systems are going fine as the amp setup was corrected. He learned his lessons well.
Swez
PS Thanks for all the participation... this club is advancing! SMILE
Tinker18 on 05/5/2004 15:20:17
well, i was pretty close....
Replies (19)
swez on 05/2/2004 13:47:59
Yes, that can be done. The change in enclosure size will make each sub perform a bit different.
The smaller enclosure will net punchy bass near 50-70 Hz naturally. The larger chamber will net better low end response in the lower octave of low bass. (35-70 Hz.)
If you used a 2 channel amp with dual LPF, this would be even easier to get that effect. A small amount of bass boost in the low end sub will help and some careful tweaking... should work well.
Swez
ttocs on 05/2/2004 14:21:08
there will be cancellation when you do this however.
swez on 05/2/2004 19:08:12
Can you explain that a bit ttocks? I'm not sure I get the full picture on cancellations here.
Swez
cplkittle on 05/2/2004 21:31:42
The reason people don't do that in my opinion is becuase there will be too large of a peak in volume where the two overlap. If one performs well from 30-80 Hz, and the other from 60-120Hz, that overlap from 60-80 would be almost twice as loud as the other frequencies. Thus making it sound like a poorly constructed bandpass box. When both subs can perform well from 30-100Hz anyway, why would you want to seperate them?
I have learned from playing around in the shop that deeper bass can be achieved without any trade offs, by using an acoustic coupled box (both subs sharing the same airspace). two 12" subs sharing a 2 cubic ft box both get the back pressure required to prevent over excursion, and at the same time they gain some characteristics of a single sub in a larger box. I tested some eclipse 10's that we had in the shop already in an acoustic coupling box and I built 2 sealed boxes, one for each. I didn't have to break out the meter for this one, the difference was obvious. There were no differences in the higher tones, but a significant difference in the low end frequencies. Maybe this would be a better consideration for you.
saintanddolphin on 05/2/2004 21:55:15
hey kittle? would you suggest using a shared chamber design or sealed for sq applications?
Are there considerations to be made for shared chamber design?
Thanks
Mike
ttocs on 05/2/2004 22:34:57
I just had my answer typed when I read it, thought about it, and knew it was wrong. Let me dig and see if I can find something that explains what I think I might have been thinking.........
uochronos on 05/2/2004 22:44:17
well i dont plan to actualy do this now i was just curious.
and i assumed there would be cancelation or boost like kittle said just wasnt sure exactly how. but like i said couldnt you seperate the frequencies so there would be no bnoost or cancelation like i said 30-60hz for the bigger box and 60-100hz for the smaller enclosure. wouldnt this net each one louder where it sounded best? bhas anyone actualy ever heard a set up like this. like i said i dont plan to do this i just want to knopw why its not done really.
swez on 05/3/2004 00:24:58
Actually, this concept is done to some degree in Pro applications, all the time. They are separate enclosures and different drivers and amped and EQ's to blend. But yes, it does work.
Eample:
18" subs are used in very large ported enclosures (scoop, folded horn and ported designs are common)
12-15" subs are used for midbass punch (folded horns, ported or sealed)
8 -10" drivers are used for low midrange (ported or sealed)
Midrange horns for upper mids & highs
Tweeters for highs
Time alignment and active crossovers, Active EQ or Parametric EQ control the peaks and dips and delay lines control time frame were all sounds meet at the same time in a given target location.
This is especially true in large venuea applications like Stadiums, large Churches and the like.
Swez
cplkittle on 05/4/2004 08:11:21
Mike,
I haven't read much into it, but I will, I only know what I have seen and heard. The only drawback is that if one sub goes, the other one will soon follow as it changes the pressure inside the box. The Diamond Denali display that came by here a couple of months ago was hitting in the 170's with three 12's in a shared ported enclosure. I will do some research on the acoustics of this type of enclosure.
cplkittle on 05/4/2004 08:39:39
This is the only thing I can find right now.. look at the bottom of the page....
http://www.danmarx.org/audioinnovation/theories.html
swez on 05/4/2004 13:50:32
Have a look at this commentary:
http://p205.ezboard.com/fcaraudioknowledgefrm7.showMessage?topicID=40.topic
WHAT HAPPENS IF 1 SUB DIES IN A SHARED ENCLOSURE?
OK folks, we have some pretty sharp thinkers here and perhaps a little reality check (POP QUIZ) might be fun and interesting as well. Here's the scenario below. What do YOU think might happen if:
THE SCENARIO:
1. have a 1200 watt (RMS) Sub amp (Class D mono amp, good for 1 & 2 ohm loads)
2. using 3 modest subs, in a sealed enclosure of proper internal dimensions
3. box does not have internal divider boards
4. subs are 300 watts RMS power ratings and 8 ohm SVC type subs
5. subs are wired all parallel for a 2.66 ohms load.
THE PROBLEM:
One sub blows a voice coil. This sub makes a few weird noises, might smell something cooking (burnt wires, plastic etc.) and then, one sub stops working. Now, we only have 2 subs that work... what happend here and what may happen to the other subs and amp in this system next?
Failure modes noted:
1. Fried Voice coil (charred and smells burnt)
2. Voice coil lead, has pulled away from the voice coil connection at woofer cone (tinsel lead separation) No eletrical connection between wire terminations to coice coil
WHY DID THE SUB FAIL?
HOW WILL THIS EVENT EFFECT THE ENTIRE BASS SYSTEM NOW?
WHAT'S IS/ARE THE PROPER FIX(ES) IN THIS SCENARIO?
Let's hear the comments and kick this one around a bit. Is a real-life scenario and can happen to anyone. OK, what do you all think is going on here and why?
OK, that's the problem, what are the issues and solutions to fix this one?
Swez
If it ain't broke, you're not trying hard enough
cplkittle on 05/4/2004 15:13:58
Most subs have at least a one year warranty.
Most subs don't just blow unless you are doing something wrong.
If one blows out of three, more than likely the other two are going to go soon as well whether they are seperated or in the same enclosure due to increased power from the amplifier. If the amp dosen't fry first from too low or too high an Ohm load depending on how the subs were wired.
If one goes you will know it.. check out the problem asap.
From the scenario listed above, if you have three SVC subs wired in parallel, and one goes, the other two should be safe. You do have an airspace gain, but at the same time you have a ohm gain as well.. going from 2.66 to 4 ohms, this is a decrease in power to each sub somewhat equivalent to what would be recommended for the airspace change. (gain of 1.5x airspace, loss of 33% power).
swez on 05/4/2004 18:10:58
Kit,
Very good link on enclosure designs. Not for the novice enclosure builder once past single vented enclosures, but a good advanced primer for those who like to explore and tinker with lesser known designs.
Thanks for the FYI !
Swez
Tinker18 on 05/4/2004 20:14:31
ok the subs are 300 rms, lets just say you are using a jbl-bp1200.1 for the amp, @ a 2.66 ohm load. that means @1200 rms to 3 subs you would have 400 going to each sub right? and if one blew, and changed the load to 4 ohms, you would only have 600 rms x1, so 300 rms to each sub, but you still have an enclosure gain of 33% correct? lets just say the box is 3 cu. feet @ 1 cu. foot per sub max sealed. this means, assuming im correct about the above, that you are now at the recomended rms rating for each sub, but have gained a cu foot in internal air volume. so each sub is operating in a bigger box than recomended. Which in the long run, could damage the other subs. im not sure about how the sub would have failed unless maybe it was overexcursion because of too much power, or maybe too much clipping or distortion in the speakers, but i think it is a combination of both overexcursion and too much power to each sub. the 400 rms to each sub fried to voice coil, and caused it to overexcur.(not sure thats a word). as for the long term effects on the other subs, i don't think the voice coil would fry, because your at the recomended rms, but i think that each sub would overexcur because of the increase in airspace not inteded for it to be used in.-note::::im not real sure about any of this, i just figured i'd take a stab at what i thought might be wrong.
saintanddolphin on 05/4/2004 20:57:40
That is a great link Kittle.You should add it to the CK list.
I am obsessed with car audio these days and and enjoy being educated here daily.Sometimes I dont even log in just because I like the anonymity(internal personality issues I guess..LOL).
I havent been this interested in one field(including my career) since highschool.
Reading these posts has reminded me of how fortunate we all are to live in a society that not only accepts but demands personal diversity for the continued evolution of the human spirit.
The Golds that are sharing insight on this topic share two impotant qaulities.They are perfectionists and they are instructors.
I know some will say this is off topic and some will say cheesy but it is what I was thinking this moment and therfore to me it is relavent.
Thanks chronus for stirring the pot.
Mike COFFEE
Tinker18 on 05/4/2004 21:29:49
someone tell me if i was even close to swez question?
uochronos on 05/4/2004 22:44:32
your post seemed pretty accurate tinker other then the subs where not each getting 400watts rms since it was a 2.66 ohm load each sub was getting just over 300watts soemthing like 325-350watts each... i would personaly cant think of a reason one sub would go out other then a manufactueres error on the sub or some other variable i'am missing.
swez on 05/5/2004 07:57:42
Very good analysis guys... the THINK ing caps are on and working well. :~)
In this case, the subs were getting a tad over 300 RMS each, but the guy used too much bass boost and over excursion caused the tinsel lead to break and constant clipping, caused the VC to char as well.
The 2 remaining subs are now a net 4 ohms and getting ~300 RMS per sub. However, the shared enclosure is now netting a 1.5 cf airspace to each sub. If he turned down the bass boost and gain, the subs should be OK as they can handle the new power output thermally, but the risk of over-excursion is still possible.
Finally, the failure mode of the one sub was due to clipping and over-excursion. He used too much bass boost and had the amp gain set wrong. This caused the amp to clip (a lot) at high SPL levels which fried the sub. He eventually got the gain and bass boost set properly and the two remaining subs were fine. The blown sub was covered by warranty and replaced. Now, all systems are going fine as the amp setup was corrected. He learned his lessons well.
Swez
PS Thanks for all the participation... this club is advancing! SMILE
Tinker18 on 05/5/2004 15:20:17
well, i was pretty close....
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