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Old 24th May 2011, 04:56 AM   #1
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Default Driver parameters for detailed bass at quiet levels.

Friends,

I need your help selecting subwoofer drivers for a pair of 5 cu ft. sealed subs I am building for a friend. Each sub will be powered by a GR Research plate amp that has 5 db of gain at 25Hz built in:
SA-1

The goal is clear: natural, punchy, detailed bass at very low listening levels for music only.

General guideline:
5 cu ft, sealed boxes
Push Pull, 2x12" drivers per box
100-120Hz, 12db/oct lowpass crossover

I am trying to get an idea of what driver parameters contribute to the ability of a driver to meet the above sound requirements.

Given that I will select between various 12" woofers for this project, I am looking for a combination of:
high Qms
high BL
low Moving mass
high Sensitivity
high Vas

I am correct? Do some parameters need special attention or priority?

If I am correct than the Dayton 12" Series II seems to fit the bill, even though it's not a fancy driver.
http://www.parts-express.com/pdf/295-120s.pdf
however, it has a high inductance value (is that important for the 100 Hz crossover point?)

Thank you in advance,
Herman
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Old 24th May 2011, 10:48 PM   #2
Ron E is offline Ron E  United States
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Quote:
Originally Posted by noviygera View Post
I need your help selecting subwoofer drivers for a pair of 5 cu ft. sealed subs I am building for a friend. The goal is clear: natural, punchy, detailed bass at very low listening levels for music only.

Given that I will select between various 12" woofers for this project, I am looking for a combination of:
high Qms
high BL
low Moving mass
high Sensitivity
high Vas

I am correct? Do some parameters need special attention or priority?
Bass and low SPL doesn't go together - introduce yourself to Fletcher and Munson - probably the best bet for punch at low listening levels is a speaker that is peaky at 60-80Hz and distorts a lot. You could do that with 6"ers in a 0.5 cubic foot box like BOSE does.
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Old 24th May 2011, 11:20 PM   #3
tinitus is offline tinitus  Europe
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gosh Ron, how can you say that

but then, I prefer bass that I can hear, rather than feel
I like detailed bass
different approach I guess

but it is possible to have very nice clean bass at very low SPL
but the whole speaker have to stay balanced
and I would suggest a relatively big woofer
and leave out the sub
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Old 24th May 2011, 11:34 PM   #4
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by noviygera View Post
Friends,

I need your help selecting subwoofer drivers for a pair of 5 cu ft. sealed subs I am building for a friend. Each sub will be powered by a GR Research plate amp that has 5 db of gain at 25Hz built in:
SA-1

The goal is clear: natural, punchy, detailed bass at very low listening levels for music only.

General guideline:
5 cu ft, sealed boxes
Push Pull, 2x12" drivers per box
100-120Hz, 12db/oct lowpass crossover

I am trying to get an idea of what driver parameters contribute to the ability of a driver to meet the above sound requirements.

Given that I will select between various 12" woofers for this project, I am looking for a combination of:
high Qms
high BL
low Moving mass
high Sensitivity
high Vas

I am correct? Do some parameters need special attention or priority?

If I am correct than the Dayton 12" Series II seems to fit the bill, even though it's not a fancy driver.
http://www.parts-express.com/pdf/295-120s.pdf
however, it has a high inductance value (is that important for the 100 Hz crossover point?)

Thank you in advance,
Herman
Hi,

All your wanted parameters except Qms will increase max SPL at the cost
of bass extension for a driver suited to a sealed 5 cuft box. As you state
low listening levels are required that means you could use lower efficiency
drivers in a far smaller box, and smaller drivers, noting maximum SPL is
determined by total cone area x excursion, match this to the amp power.

Doing some modelling in WinISDpro should help a lot.

rgds, sreten.
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Old 24th May 2011, 11:48 PM   #5
tinitus is offline tinitus  Europe
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at low SPL you won't need subwoofer

but if need be, instead EQ the main woofer
should be perfectly fine at lower SPL
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Old 25th May 2011, 12:11 AM   #6
tb46 is offline tb46  United States
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Location: Texas
Hi noviygera,

Take a look at the Parts-Express woofer selection guide:

Woofer Selection Guide at Parts Express

In the Sealed F3 Hz column, e.g.: for a 12" woofer you'll find the Peerless 835017 with an F3 of 49 Hz.

Regards,
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Old 25th May 2011, 12:55 AM   #7
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What kind of music? Qts is more important overall than Qms. (unless you are using tube amps and like distortion...)

for rock n roll i'd use the push/pull 12's
for classical i'd use stereo single 15's (DCS385-4 15 in a 5ft^3 box half filled with polyfill and enough bracing to hold up a truck)
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Old 25th May 2011, 01:27 AM   #8
Ron E is offline Ron E  United States
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OK, threshold of hearing bass in a room is after Robinson-Dadson or ISO 226:2003. Equal-loudness contour - Wikipedia, the free encyclopedia A person can hear 20Hz (threshold) at ~75dB, and 100Hz at ~20dB, I would guess a typical "low" level to be <60dB, which means that frequencies below 30Hz would be essentially inaudible, and in most rooms, where the noise floor might be 40dBC, you are looking at sounds into the 60 Hz range that may be pretty difficult to detect.

My response was somewhat tongue in cheek, but it is one way to skin a cat. Multiple coffin sized boxes with dual 12" woofers will make bass, but even one in 1 cubic foot will probably make enough for the application. There are no magic parameters and perhaps a discussion of the true goals and implicit assumptions of the project would be pertinent.
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Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. Aldous Huxley
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Old 25th May 2011, 02:02 AM   #9
tinitus is offline tinitus  Europe
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yes, I think -6db/35hz with smooth roll off in closed box would do very nicely
I would choose a not too heavy coned woofer, but still relatively low Fs, and moderate Qts
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Old 25th May 2011, 02:26 AM   #10
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Push-pull dosen't help with distortion until the drivers are driven hard, no real benefits at low levels.

just thought you should know.
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