Consider the following statement, from the archives of an audiophile magazine.
"...A designer might opt for multiple smaller woofers instead of one single large one. Perhaps he wants to keep the front baffle narrower or to take advantage of the added control of three individual magnets. Still, the combined surface area of the smaller woofers will duplicate that of a single large woofer..."
How does this happen?
Does this mean one can use three or four small woofers, may be 5" ones, and get the same deep bass extension as an 18" subwoofer?
What are the advantages and disadvantages in this kind of a design?
"...A designer might opt for multiple smaller woofers instead of one single large one. Perhaps he wants to keep the front baffle narrower or to take advantage of the added control of three individual magnets. Still, the combined surface area of the smaller woofers will duplicate that of a single large woofer..."
How does this happen?
Does this mean one can use three or four small woofers, may be 5" ones, and get the same deep bass extension as an 18" subwoofer?
What are the advantages and disadvantages in this kind of a design?
No, for several reasons.
it would be more like 16 or more 5" drivers to match the area of an 18" woofer.
what really matters is displacement, so 5" drivers with 6mm xmax and 18" with say 12mm, you'd need half again as many to get the same displacement.
However, you aren't going to get the deep bass extension without some serious EQ, since most 5" drivers have much higher resonant frequencies than typical 18" drivers.
go for something big with lots of xmax, you'll be happier than trying to force teeny mid-woofers to act as subs.
it would be more like 16 or more 5" drivers to match the area of an 18" woofer.
what really matters is displacement, so 5" drivers with 6mm xmax and 18" with say 12mm, you'd need half again as many to get the same displacement.
However, you aren't going to get the deep bass extension without some serious EQ, since most 5" drivers have much higher resonant frequencies than typical 18" drivers.
go for something big with lots of xmax, you'll be happier than trying to force teeny mid-woofers to act as subs.
kspv said:
You are missing the point. Four 5" drivers = one 10" driver as
area is the square of the dimension, but as said the 10" is a
lot easier to make with longer excursion.
The quote makes sense in terms of bass mid units in speakers
but not subwoofers, in subs multiple units have no advantage.
🙂 sreten.
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I agree with Bob, though you would have about the same displacement as a larger woofer, this would only increase your theoretical SPL at all frequencies. Also, your woofers will need to be wired in phase. Though, I've always thought that this would not work without EQ because you can't have the natural resonance that a larger woofer comprises without such circuitry; and, the previous comments confirm the latter.
Anyway, I'm still interested in building a line array some time, preferably an OB line array.
BTW, Polk Audio used to use some 3-4" drivers x4 in their older TL models. Not sure if they still sell them or not, but I remember seeing them and their power ports in the bottom.
Anyway, I'm still interested in building a line array some time, preferably an OB line array.
BTW, Polk Audio used to use some 3-4" drivers x4 in their older TL models. Not sure if they still sell them or not, but I remember seeing them and their power ports in the bottom.
BobEllis said:
Math wise why would you need half again as many and not twice as many to reach the same displacement?
IMHO multiple drivers are only of use if you regularly exceed Xmag on a single driver. Lower mass drivers also have some theoretical benefits as regards decay rates, so 2 lower mass drivers of equivalent volume displacement (within Xmag) would be better than 1 heavier single unit. If you never went out of the range of normal operation, then I'd suggest that the biggest single driver you can find is probably the one to go for in a subwoofer.
Re: Re: Small Woofers For A Subwoofer?
Form factor may be the only advantage to having multiple subwoofers in one box. I had a case where I was constrained in how much vertical space I had to implement a moderate output, moderate depth subwoofer. I was able to build a 8.5" high x 20 inch wide box using two 6.5" woofers and a vent in between. Without the form factor constraint I would have used a bigger driver.
It should be notes that there is no array effect from multiple subwoofer drivers because the frequencies are too low for this to happen.
Not to restart a discussion we covered a few months back, but multiple subwoofer boxes in different areas of the room can be used to make the bass response more consistent throughout the room. So two sub boxes can be used rather than one in order to get a more even response.
Advantages:
- possibility of more consistent "even" response across the room.
- Smaller diameter sub drives tend to have lower Vas so it is easier to use smaller cabinets. Multiple smaller subs may be more appealing than a single larger sub.
Disadvantages:
- If you drop down in driver size you do have to EQ to get back to the same frequency response for the reasons given in this thread. This may push you back to using the original driver size or going with more sub boxes in order to get the desired level of output and power handling.
- You may need more amplifiers.
- More boxes to build
I am currently implementing 4 8" subs dispersed around the room and LT EQed to -4dB @ 20Hz. Plan is to go to 8 over the next few months.
sreten said:
Form factor may be the only advantage to having multiple subwoofers in one box. I had a case where I was constrained in how much vertical space I had to implement a moderate output, moderate depth subwoofer. I was able to build a 8.5" high x 20 inch wide box using two 6.5" woofers and a vent in between. Without the form factor constraint I would have used a bigger driver.
It should be notes that there is no array effect from multiple subwoofer drivers because the frequencies are too low for this to happen.
Not to restart a discussion we covered a few months back, but multiple subwoofer boxes in different areas of the room can be used to make the bass response more consistent throughout the room. So two sub boxes can be used rather than one in order to get a more even response.
Advantages:
- possibility of more consistent "even" response across the room.
- Smaller diameter sub drives tend to have lower Vas so it is easier to use smaller cabinets. Multiple smaller subs may be more appealing than a single larger sub.
Disadvantages:
- If you drop down in driver size you do have to EQ to get back to the same frequency response for the reasons given in this thread. This may push you back to using the original driver size or going with more sub boxes in order to get the desired level of output and power handling.
- You may need more amplifiers.
- More boxes to build
I am currently implementing 4 8" subs dispersed around the room and LT EQed to -4dB @ 20Hz. Plan is to go to 8 over the next few months.
moving_electron said:
Oops - mental math while changing terms. I originally was thinking of the JBL 2245 with a 9 mm xmax. My bad.
What about a giant driver >20", say the Precision Devices 21" or 24" or the Beyma 21" driver?
It may have a much heavier moving mass than a 10", it may not behave as piston-like when it is shifting a lot of air, but at most listening levels, it's excursion is tiny.
For instance, to produce 95dB@20Hz@1M, four Scan Speak 22Ws would need 110W shared between them, and each of them would be travelling about 12mm peak to peak. The 24" would need 60W and its excursion is a mere 5mm peak to peak. Those are in sealed boxes of equivalent Q=.707 alignment.
It may have a much heavier moving mass than a 10", it may not behave as piston-like when it is shifting a lot of air, but at most listening levels, it's excursion is tiny.
For instance, to produce 95dB@20Hz@1M, four Scan Speak 22Ws would need 110W shared between them, and each of them would be travelling about 12mm peak to peak. The 24" would need 60W and its excursion is a mere 5mm peak to peak. Those are in sealed boxes of equivalent Q=.707 alignment.
I have seen such a setup. Two 20" units sharing box. I dont have any decent facts about that system, only that I was very impressed by the sound of it.
It is based on regular looking tower speakers sporting 2*10" units each. I only had a short encounter with this system, but I remember the sub was in such a great design that it fell in with the furniture, so I didnt notice it. After picking up my jaw from the floor I made a comment about the fantastic soundstage and the incredibly low frequencies the system did at relatively high pressure levels.....asking how in the world he got that out of 4 * 10"???? he just pointed in direction of the cupboard sized sub 🙂
Magura🙂
It is based on regular looking tower speakers sporting 2*10" units each. I only had a short encounter with this system, but I remember the sub was in such a great design that it fell in with the furniture, so I didnt notice it. After picking up my jaw from the floor I made a comment about the fantastic soundstage and the incredibly low frequencies the system did at relatively high pressure levels.....asking how in the world he got that out of 4 * 10"???? he just pointed in direction of the cupboard sized sub 🙂
Magura🙂
The PD 2150 models quite nicely as a Linkwitz transform sub, with a box only marginally bigger than the driver😉
It's thermally limited to 750W, which theoretically produces 100dB@20Hz@1m, with a peak to peak displacement of 14mm, all in a 50L box. 80L get's you a big increase in deep bass (3.5dB), with only 4 mm more travel.
I'm building one for the sheer hell of it😀
It's thermally limited to 750W, which theoretically produces 100dB@20Hz@1m, with a peak to peak displacement of 14mm, all in a 50L box. 80L get's you a big increase in deep bass (3.5dB), with only 4 mm more travel.
I'm building one for the sheer hell of it😀
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