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1 sub - VS - 2??

What differences will you see between 1 sub and 2?

The question is loaded..... but from a pure SQ standpoint a single sub is more desirable....

Quote:

Originally Posted by Haunz (Post 306135)

The question is loaded..... but from a pure SQ standpoint a single sub is more desirable....

WHAT HE SAID↑

yeah i was just scared to answer this in anyway..... I have one and its far louder then my friend who has 2 12's but thats because of what we have for gear, the box, the vehicle, the way they are tuned..... okay im just going to stop now....

depends on how much power you have.

depends on the box ,amp/amps ,sub/subs and then you have the car there in
how much timw and work in the install

all other things being equal (which they never are)...2 subs of the same model will be louder than a single one of the same model.

Quote:

Originally Posted by veeman (Post 306334)

all other things being equal (which they never are)...2 subs of the same model will be louder than a single one of the same model.

Exaclty, what he said.
moreover depending on the subs, you will only gain a small # db's over a single sub.

Quote:

Originally Posted by veeman (Post 306334)

all other things being equal (which they never are)...2 subs of the same model will be louder than a single one of the same model.

sometimes thats not the case. its very power dependant.

I have been curious about this as I run stereo subs in my home setup and the improvement is substantial. I worry that a vehicle cabin will be too small to realize the same benefits. I will be experimenting with this in the near future as I have a setup that will allow a relatively quick switch.

Generally speaking, you can get 1 sub to hit as hard if not harder than 2 subs because with 1 sub you can build the proper box that it requires. Generally most people think, hey, i need 2 subs and cram them in an improper box which will hinder their performance, but if you can get each sub in their proper box's to fit in your vehicle then you will be laughing.

I run 2 subs - in stereo - just becuase....

:smilie_da

If you have one sub and add another without adding power the gain will be nill, however if you double the power and add another sub you should have a desirable gain, however you need to have the space to have a proper box for both subs.

Quote:

Originally Posted by johnw (Post 308869)

By adding a sub for a total of 2 you will be benefiting from an increase in acoustic output of 3db ( double ). If you wire them in parallel you will increase the effective efficiency by 3db, if you wire them in series there will be no electrical gain. The total gain for parallel will be 6db and for a series connection it will be 3db.
This happens regardless of the power of your amplifier. The only question for an amplifier here is whether or not it can handle the load created by the pairing. Low impedance stability, damping factor, stuff like that.

Quote:

Originally Posted by rastanearian (Post 308906)

wow this is a loaded question, but here goes.
Doubling electrical power adds 3.01 db of output under perfect curcumstances, halfing it subtracts 3.01 db.
so, given wattage through 2 drivers as apposed to 1 goes up for the given Epd, but is effectively halved by the split in wattage.
In an open field environment doubling cone area should theoretically yield no benifit.

Power compression:
As the mechanical suspension of a driver reaches further towards it's xmax it will impede the electrical force of it's voice coil. This is due to both the fact the surround and spider are being stretched to thier limits as well as the fact the voice coil is leaving the magnetic field of it's motor structure. This means that more energy put into the voice coil will simply result in more heat produced in the voice coil, as apposed to more movement of the cone section of the driver. Power compression can reach levels of 5-6 db in high rms woofers, meaning that they are effectively producing the same spl as a "perfect world" woofer that most design software reprisents at a quarter of the wattage.

Port activity:
I'm not getting into the physics of a vented enclosure, but the size/location/relation of the vent to the drivers can make a big difference. For unexplained reasons I can't figure out I got a 3 db boost by running 2 identical boxes instead of 1 on the same amp. Mathematically I should have yielded a +3 -3 gain of 0, but due to cabin resonance or another anomaly I got a 3 db boost at 46 hz.

adding an identical driver raises efficiency by 3.01 db, but at half the power per driver meaning a -3.01 db of output, cancelling that bonus out. This is the simple physics of converting electricity into pneumatic pressure. The countering effects are that near a driver's power compression 2 drivers will beat one, and at the correct frequency 2 drivers in a properly tuned enclosure will beat 1/2 in any other enclosure.

Quote:

Originally Posted by rastanearian (Post 308906)

wow this is a loaded question, but here goes.

Rasta's comments aren't taking into account the given potential per driver. By his math 24 average 10" woofers with 100 watts overall would reach 160 db.

Doubling electrical power adds 3.01 db of output under perfect curcumstances, halfing it subtracts 3.01 db.
so, given wattage through 2 drivers as apposed to 1 goes up for the given Epd, but is effectively halved by the split in wattage.
In an open field environment doubling cone area at any given power level should theoretically yield no benifit.

Power compression:
As the mechanical suspension of a driver reaches further towards it's xmax it will impede the electrical force of it's voice coil. This is due to both the fact the surround and spider are being stretched to thier limits as well as the fact the voice coil is leaving the magnetic field of it's motor structure. This means that more energy put into the voice coil will simply result in more heat produced in the voice coil, as apposed to more movement of the cone section of the driver. Power compression can reach levels of 5-6 db in high rms woofers, meaning that they are effectively producing the same spl as a "perfect world" woofer that most design software reprisents at a quarter of the wattage.

Port activity:
I'm not getting into the physics of a vented enclosure, but the size/location/relation of the vent to the drivers can make a big difference. For unexplained reasons I can't figure out I got a 3 db boost by running 2 identical boxes instead of 1 on the same amp. Mathematically I should have yielded a +3 -3 gain of 0, but due to cabin resonance or another anomaly I got a 3 db boost at 46 hz.

adding an identical driver raises efficiency by 3.01 db, but at half the power per driver meaning a -3.01 db of output, cancelling that bonus out. This is the simple physics of converting electricity into pneumatic pressure. The countering effects are that near a driver's power compression 2 drivers will beat one, and at the correct frequency 2 drivers in a properly tuned enclosure will beat 1/2 in any other enclosure.

yay double post instead of edit:stroke:

Quote:

Originally Posted by rorybreaker (Post 309607)

wow this is a loaded question, but here goes.

Rasta's comments aren't taking into account the given potential per driver. By his math 24 average 10" woofers with 100 watts overall would reach 160 db.

Actually my math says that 32 drivers each having a sensitivity of 86db (random pick) all wired in parallel (practically a short circuit that no amp in the world can drive) being driven by 128 Watts will result in only 137db of SPL. Of course a driver array of this magnitude would create its own boundary effect causing a rise in output relative to the area of the array. Probably about 6db/oct for the drivers in the middle and falling off as you neared the edge

Doubling electrical power adds 3.01 db of output under perfect curcumstances, halfing it subtracts 3.01 db.
so, given wattage through 2 drivers as apposed to 1 goes up for the given Epd, but is effectively halved by the split in wattage.
In an open field environment doubling cone area at any given power level should theoretically yield no benifit.

Doubling the cone area at any power level will result in twice as much air moving (double = 3db)
Halving the impedance of a speaker by adding another driver in parallel will effectively raise the sensitivity of the speaker by 3db.
Yes this is theoretical and there are real world considerations to be made. For example the above does not take into account boundary effects and assumes an anechoic environment.

Power compression:
As the mechanical suspension of a driver reaches further towards it's xmax it will impede the electrical force of it's voice coil. This is due to both the fact the surround and spider are being stretched to thier limits as well as the fact the voice coil is leaving the magnetic field of it's motor structure. This means that more energy put into the voice coil will simply result in more heat produced in the voice coil, as apposed to more movement of the cone section of the driver. Power compression can reach levels of 5-6 db in high rms woofers, meaning that they are effectively producing the same spl as a "perfect world" woofer that most design software reprisents at a quarter of the wattage.

There is a much simpler way of describing what happens when a voice coil leaves the magnetic field of it's motor structure. Expensive!

Port activity:
I'm not getting into the physics of a vented enclosure, but the size/location/relation of the vent to the drivers can make a big difference. For unexplained reasons I can't figure out I got a 3 db boost by running 2 identical boxes instead of 1 on the same amp. Mathematically I should have yielded a +3 -3 gain of 0, but due to cabin resonance or another anomaly I got a 3 db boost at 46 hz.

adding an identical driver raises efficiency by 3.01 db, but at half the power per driver meaning a -3.01 db of output, cancelling that bonus out. This is the simple physics of converting electricity into pneumatic pressure. The countering effects are that near a driver's power compression 2 drivers will beat one, and at the correct frequency 2 drivers in a properly tuned enclosure will beat 1/2 in any other enclosure.

Adding an identical driver raises the sensitivity by 3db and doubles your power handling.

Sorry to pick apart your post, but it blurred the issue a little.

halving the impedence doubles the output only because the amplifier can handle producing double the wattage. In any case you could add a second amp, the system hasn't become more efficient, just more potential. Stillwater's amplifiers don't produce anywhere near double because thier output stages are extremely well controlled. There are many models of amplifier who's wattages don't simply double every time you halve the impedance.

I followed your line of thinking for many years until I started trying to get more efficiency out of small wattage systems and actually measured the outputs I was achieving. The key to efficincy is how much any given wattage of power is being converted current to sound pressure, not how a curcuit turns a 100 watt amp into a 200 watt amp. At any specific wattage the only bonuses I have been able to achieve by doubling cone area are from a large group vented enclosure's port activity and by staying below the power compression of my drivers.

I'm not trying to start any arguements (although I think I really might have), like I said I followed the same line of thinking for many years. I'm not suggesting you're spouting "half the ohms means twice the watts!"

I should maybe note where I got lost on this line of thinking:
When I started box building I got most of my information from a couple of books. One was the loudspeaker design cookbook, the other was a really informative paperback from radioshack that's out of print. I've been trying to find it for years because it really does explain the equations used to determine the values a given box will produce, as well as how to do a crude near-field test on a woofer.

both of these books explained the "electrical" efficiency gained when impedence is halved. This is an absolutely true fact, nobody can argue a 4 ohm curcuit is more "electrically" efficient than a 2 ohm curcuit. The problem is that we're talking apples and oranges. The only thing incorrect here is:
"Halving the impedance of a speaker by adding another driver in parallel will effectively raise the sensitivity of the speaker by 3db."
adding another speaker alters the curcuit, not the other speakers on that curcuit. A 4 ohm speaker is still a 4 ohm speaker when you wire it's twin in parellel with it, it's just the implied curcuit that changes.

apples and oranges: the question at the start of this post was simple "1 or 2?" I think we can assume any option in spl would run your amplifier at it's highest output wattage, so we have to try to stick to a given impedence. let's assume 2 ohms. 2 4ohm subs in parellel, 1 2ohm sub, ect. I've specifically built and tested 2 vs 4 and 1 vs 2 in a few cars years ago, with varying results. The only given was with a sealed encloser the number of drivers didn't matter as long as the impedence stayed the same on the amp, and the power was fairly well below the driver's power compression area.

In vented enclosures I yielded a bit better output around the fb area, but it was very sloped and could have been the result of anything from an out-of-spec woofer to the exact location of the mic, ect.