If I have a 10" woofer capable of 94dB at 25Hz (within Xmax), then adding a 2nd woofer (the other channel) will allow 100dB. If I then estimate 10dB boost due to boundary reinforcement, then I can expect roughly 110dB levels at 25Hz. My point is that 2 x 10" woofers (a stereo pair) should produce ample volume for a typical listening room.
Rather than going to subwoofers which are always a compromise with location and integration to satellites, I think a 3 way system with a 10" woofer is the best solution. Any thoughts?
Rather than going to subwoofers which are always a compromise with location and integration to satellites, I think a 3 way system with a 10" woofer is the best solution. Any thoughts?
David Gatti said:
You get a 6db increase in sensitivity, yes- but only a 3 db increase in efficiency. Two woofers in parallel halves the impedance, and since most amplifiers act like voltage sources, they lower impedance draws more current. You get 3db from doubling power, and 3db from doubling cone area. At least- that's how I understand it- a 6db total increase.
One thing to consider is- what is ample volume? Home theater (and occasional house parties) were the reason my 10's weren't quite enough.
Ok, I think this is starting to make some sense.
Lets say the left 10" woofer produces 90dB.
Add the right 10" woofer with the same signal at the same 90dB and together they will produce a total level of 93dB.
However, if both woofers a placed right next to each other, through some means I don't fully understand, the combined output is 96dB.
Anyone care to explain this "coupling" phenomenon.
Lets say the left 10" woofer produces 90dB.
Add the right 10" woofer with the same signal at the same 90dB and together they will produce a total level of 93dB.
However, if both woofers a placed right next to each other, through some means I don't fully understand, the combined output is 96dB.
Anyone care to explain this "coupling" phenomenon.
Mos Fetish said:
The woofers were made for a company named Edge. They were part of an initial run for a project that was changed and they became surplus, so to speak. Through a contact I was able to pick up a dozen of them for $25 each. They are nice woofers but certainly not state of the art. They are 5 ohm ea. and run in parallel. Fortunately I have a GAS amp that can handle 2 ohm loads.
There are 4 boxes, 3 cu.ft. each - 2 stacked pairs.
Seventh heaven is when you use woofers at a small percent of their potential in terms of excursion (you could say that they have a lot of headroom) in sealed boxes with a low Q (.5 something). The cones barely move and I have all the quality bass I could possibly want. The system goes deep thanks to room gain and they integrate very well thanks to the proper cross at 90Hz to the mids so, not only is there lots of good clean bass but the systems response to percussion is exceptional. For HT or Megadeth, the system delivers in spades. All this for $200 and some time in the workshop. That's seventh heaven in the woofer department as far as I can see.
I'll admit that I'm pushing the poor 5 1/2" mids to their limit but the fix for that is coming soon via an MTM system of greater efficiency.
David Gatti: i dont have a clue as to their xmax potential. i do know, however, that they can drive even me out of the room before they audibly bottom or sound harsh. according to Bill Fitzpatrick i must be near 7th heaven. the cones dont move all that much, and the boxes are sealed. except for my in-room sub all the speakers in the house are sealed designs. i have always preferred the bass that way.
sm.
sm.
Hi there...something doesn't quite fit......those speakers in a 3 cu ft box at 25Hz are going to have a tough and a rough excursion time....At the moment I don't have the LS software working in my system, but it seems more than a 10dB response drop at that frequenc; the closed box resonant would be pushed up to 45Hz or more......certainly wouldn't give prominent bass.
Do you have any data for the drivers ?
rich
We're talking 25 Hz here, where the wavelength is 345/25=13.8 metres. Assuming that the speakers are 3.45 metres apart, that is 1/4 wavelength. So in the direction straight to the side, the gain will be only + 3 dB, since adding two sinusoids 90 degrees out of phase gives just that. In the front direction, the sinusoids will add up in phase which yields + 6 dB. To determine the in-room gain from adding another driver , one would have to make an average over all directions, and my guess would be a 4-5 dB gain.
At higher frequencies the gain will only be + 3 dB, though.
At higher frequencies the gain will only be + 3 dB, though.
Thanks Svante, that's the best explanation I've had so far.
So back to the original point re LF capabilities of a stereo pair of 10" woofers:
Scanspeak 25W8565 with 6.5mm Xmax
Using Unibox,
1 woofer linear (within Xmax) SPL :
20Hz 87dB
30Hz 94dB
40Hz 99dB
Stereo pair - add 5dB gain
20Hz 92dB
30Hz 99dB
40Hz 104dB
Now add say 8dB typical room gain:
20Hz 100dB
30Hz 107dB
40Hz 112dB
This is the maximum SPL that can be achieved with a stereo pair of 10" drivers operating within Xmax. You could also add maybe another 3dB due to further driver excursion and you have 110dB at 30Hz and I think apart from real hard-core movie bass freaks, this is adequate.
So back to the original point re LF capabilities of a stereo pair of 10" woofers:
Scanspeak 25W8565 with 6.5mm Xmax
Using Unibox,
1 woofer linear (within Xmax) SPL :
20Hz 87dB
30Hz 94dB
40Hz 99dB
Stereo pair - add 5dB gain
20Hz 92dB
30Hz 99dB
40Hz 104dB
Now add say 8dB typical room gain:
20Hz 100dB
30Hz 107dB
40Hz 112dB
This is the maximum SPL that can be achieved with a stereo pair of 10" drivers operating within Xmax. You could also add maybe another 3dB due to further driver excursion and you have 110dB at 30Hz and I think apart from real hard-core movie bass freaks, this is adequate.
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