It's the size of the box which is the main factor in LF response. Using bigger/more drivers allows you to go louder but the response will get worse at LF if you use the same size box.
eg If you have 1x12" in a 50ltr box box. adding another 50ltr box & 12" will give you 3dB more efficiency but the LF response remains the same. This is equivalent to a 100ltr box with 2x12".
If you use the 100ltr box with 1x12", you'll find your LF response goes lower than with 2x12". It's how much box each driver sees that determines LF response.
All this supposes the TS parameters of each unit is 'matched' to the size of the box .. but you'll still see this general trend if not. Why don't you play with one of the speaker box design programmes to get an idea of what is going on.
But if you have EQ, you can compensate for the poorer LF response of a 'small' box by boosting LF. More units mean you can use greater power for this boost.
eg If you have 1x12" in a 50ltr box box. adding another 50ltr box & 12" will give you 3dB more efficiency but the LF response remains the same. This is equivalent to a 100ltr box with 2x12".
If you use the 100ltr box with 1x12", you'll find your LF response goes lower than with 2x12". It's how much box each driver sees that determines LF response.
All this supposes the TS parameters of each unit is 'matched' to the size of the box .. but you'll still see this general trend if not. Why don't you play with one of the speaker box design programmes to get an idea of what is going on.
But if you have EQ, you can compensate for the poorer LF response of a 'small' box by boosting LF. More units mean you can use greater power for this boost.
I would suggest you look at an array of sealed subwoofers. Sealed subwoofers allow for smaller enclosures but at the cost of low sensitivity. An array increases sensitivity so the differences balance out.
Also, "One of the additional benefits of the array’s sensitivity increase is that for the same SPL
the individual drivers in the array are operated at much lower drive level which reduces
distortion levels."
Regards,
Dan
Also, "One of the additional benefits of the array’s sensitivity increase is that for the same SPL
the individual drivers in the array are operated at much lower drive level which reduces
distortion levels."
Regards,
Dan
The more drivers you have the higher the resulting maximum level at a certain frequency is, also in the bass.
so if a singe driver can do 60dB SPL at 20Hz, 16 can do 24dB more at lower frequencies.
You will need EQ to get that in balance with rest of the spectrum..
This has all been very helpful. Thanks to all.
Let's take another hypothetical situation: Assuming I don't have 10' ceilings (I don't) nor do I have 8 or 10 drivers per side-- but Ido have a 3' tall speaker enclosure.
All things being equal (if they ever were): if I had 6 matched drivers of 6.5" in diameter, can I put them together in twos in an isobaric configuration (series) and then put those pairs in a line of 3?
Let's take another hypothetical situation: Assuming I don't have 10' ceilings (I don't) nor do I have 8 or 10 drivers per side-- but Ido have a 3' tall speaker enclosure.
All things being equal (if they ever were): if I had 6 matched drivers of 6.5" in diameter, can I put them together in twos in an isobaric configuration (series) and then put those pairs in a line of 3?
You can do that, but each isobaric pair has no more displacement than a single driver, so you will have reduced potential output by -6dB. That sounds less than half as loud below ~40 Hz.
Going floor to ceiling won't increase the low frequency output compared to 2 wide by 3 tall in a 3' tall speaker enclosure.
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So really it sounds like size is everything: a large enclosure with multiple speakers in some configuration is the best and only way to get lower frequencies without going into a subwoofer.
Isobarik was developed for using 2 drivers to operate in a much smaller enclosure for car audio. The cost is "wasting" power for the invisible driver.
My current system is 4 x 5.25" midwoofs in a truncated line array and one ribbon tweeter.
Will the full height line array not give a cyclical wavefront also for the lowest frequencies? Thus 3dB down per doubling distance vs 6?
All wavelengths are cyclical, one cycle is equal to one wavelength.
A "cylindrical wavefront" does not happen for the lowest frequencies, as they are much longer than the floor to ceiling height in most domestic rooms.
In reality, a "cylindrical wavefront" is just an overly simplified version of the complex interference patterns generated by a line array.
The 3dB reduction per doubling of distance vs -6db only happens in the near field due to destructive interference.
The near field in a line array exists for any frequency and distance where moving farther away will result in more drivers summing coherently (close to “in phase”), instead of incoherently. Once all the drivers sum coherently, the far field is attained.
From:
https://www.prosoundtraining.com/2010/03/17/line-array-limitations/
The near field distance can be defined by the following relationship:
D=1.57 L squared/λ
where
D is the distance to the far field transition
L is the physical length of the line source
λ = the wavelength of the frequency in question (all lengths in identical units).
Beyond this distance the listener is in the far field and there is 6 dB drop in level per doubling of distance. The transition distance can be quite long at short wavelengths, that is, high frequencies, but it is shorter at low frequencies. For each octave lower in frequency, the transition distance is cut in half.
The transition from near to far field with a floor to ceiling array in an 8 foot (2.46 meter) high room would be at ~43 inches (a bit over one meter) at 40 Hz.
Art
100 hz. I am listening to it without a sub at the moment. I have a sub to add later.