Michael R Price
Screenwriter
- Joined
- Jul 22, 2001
- Messages
- 1,591
A friend of mine is looking to extend the frequency response of his old Advent Loudspeakers well into the subsonic region. He has a very small room, about 7x14x8 feet, and is looking to do this without adding a crossover to the Advents, which extend to around 40Hz before rolling off. Extremely high output (over 105dB or so) is not a concern. He also has a very limited budget. To do this we have envisioned a very unusual design, which uses a single Adire Shiva driver in a very large, 265-liter, box, tuned to an extremely low (11 Hz) frequency. After some tinkering with the LspCAD demo, we have been able to get an extremely flat (predicted) response from around 10 to 35 Hz, which is exactly what he needs. (The reason I believe that this works is that his small room has very high low-freqency gain which compensates for the rolloff of the driver between its peak and the tuning point.) What I am asking is if this design really can work and how it would perform. I find it hard to believe that a value driver like the Shiva can be applied in such an unusual way and still perform as well as other, more conventional (Adire, EBS, etc) Shiva applications.
Here is a description of the planned design.
Adire Shiva driver
Parts Express 110W plate amp
2 lb. polyfill
20x20x54in. MDF box, with two main braces extending vertically through the box, along with smaller braces on the horizontal plane to support the main braces. 4" diameter, non-flared, 24" long port tube for a tuning of around 11Hz. The box volume, with driver, amp, port, and bracing taken into account, is about 265 liters.
I have entered the parameters into LspCAD (QI=10, Qa=30, fill=25%, 24" with 4" ID port) and this is the result. The graph assumes a 2nd-order low pass filter at 40Hz, which is the lowest setting on the cheap Parts Express sub amp (and should provide for the best blend with the Advents, which already have good bass extension in such a small room).
[Large summary graphic link]
[LspCAD demo boxfile link]
Are there any opinions on what can be done to improve the performance of this planned subwoofer, or on whether the design is feasible at all? Again, this is a very unusual design, at least from what I have read so far. Thanks for your input.
[This is my first post at the Home Theater Forum, though I have been reading the forums once in a while for a few months now]
Here is a description of the planned design.
Adire Shiva driver
Parts Express 110W plate amp
2 lb. polyfill
20x20x54in. MDF box, with two main braces extending vertically through the box, along with smaller braces on the horizontal plane to support the main braces. 4" diameter, non-flared, 24" long port tube for a tuning of around 11Hz. The box volume, with driver, amp, port, and bracing taken into account, is about 265 liters.
I have entered the parameters into LspCAD (QI=10, Qa=30, fill=25%, 24" with 4" ID port) and this is the result. The graph assumes a 2nd-order low pass filter at 40Hz, which is the lowest setting on the cheap Parts Express sub amp (and should provide for the best blend with the Advents, which already have good bass extension in such a small room).
[Large summary graphic link]
[LspCAD demo boxfile link]
Are there any opinions on what can be done to improve the performance of this planned subwoofer, or on whether the design is feasible at all? Again, this is a very unusual design, at least from what I have read so far. Thanks for your input.
[This is my first post at the Home Theater Forum, though I have been reading the forums once in a while for a few months now]