I recently dug out my long forgotten sub I put up together sometime ago, so I decided to pair it up with my DIY bookshelf speakers based on w12cy001 + XT25 to see how this setup would work. Amazingly, it got me exactly where I wanted - very close, if not over the KEF Reference 3 overall. It's a 28l closed box with JBL CS1210 car woofer that I found on sale for 40eur. Now that I got my appetite for low end in the open, I'd like to see if I could upgrade it to something even better. I can't see what the Fs is for this woofer, but probably not too stellar. I do run it with FreeDSP into Sure Electronics 200W class D mono block so I can adjust and flat it out pretty well, but there are probably still limits on how low it could go. Would a switch to GRS 12SW-HE with Fs of 22Hz make any sense? I wouldn't mind going even for something substantially more expensive if that would make audible improvement, considering I am listening mostly at lower levels.
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are you willing to buy another driver or stick to what you have, amp and dsp you have already right ?
is just matter of building a box that hit low ? around 22 right ?
i think you have 3 options, a BR design... a TQWP....or a TH...
if you stick with your current 12, and going low you will be limited by xmax
here is a quick TQWP i quick simmed 4you
115L box with the GRS you posted
hitting xmax at 250watts gives you this in a corner
i did not add any polyfill/acoustic damping inside the box but you can to tame stuff above 100HZ or just use your DSP
is just matter of building a box that hit low ? around 22 right ?
i think you have 3 options, a BR design... a TQWP....or a TH...
if you stick with your current 12, and going low you will be limited by xmax
here is a quick TQWP i quick simmed 4you
115L box with the GRS you posted
hitting xmax at 250watts gives you this in a corner
i did not add any polyfill/acoustic damping inside the box but you can to tame stuff above 100HZ or just use your DSP
28 liters is not large enough to provide much useful port output with an Fb (box tuning) ~22Hz, even if you were to mount the port outside the box.
With enough EQ, either the speaker you have or the GRS 12SW-4HE can reach 22Hz at -3dB in your sealed box.
Assuming the same Vas, in a small box more EQ is required for a higher Fs driver to flatten it's response.
A 12" with 12mm Xmax (one -way linear excursion) can do ~98dB at 22Hz at one meter, around an equal loudness level to 40dB at 1kHz, a quiet conversational level.
With such a small sealed box, quite a bit of power is required to drive the speaker to it's full Xmax.
The question to ask is whether your amp and driver/box can deliver enough clean power to produce the sound pressure at 22Hz you desire.
With a 34 volt power supply, the Sure has 200W at 10% distortion into a 3 ohm load.
10% amp distortion usually sounds pretty nasty.
It may have around 125 watts at 1% distortion into 4 ohms.
125 watts (~22volts @4ohms) won't come close to pushing the driver to Xmax in a one liter sealed box.
That said, without any TS parameters for the JBL CS1210, can't say whether the GRS 12SW-4HE would provide any more SPL (or sound any better) given only ~125watts to work with.
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The 135L volume I calculated will be around 20 inches per side , although TQWP is kind like a one fold horn ,so expect to have a rectangle cabinet type instead of a cube like the regular BR HT subs, 24L seems pretty hard to reach with the JBL and your modest power source , if you want small and loud you will need $$$ , as you will need power and a capable driver to take the power and that ain't come for peanuts. That's the Hoffman law , it is what it is.
I have built my own amp in class D, with around 600W mono at 2ohm, so I can use that. I guess I am trying to achieve something like Beolab 5 which does not take much space but goes pretty low. That's a bigger driver though.
https://specs4audio.wordpress.com/2013/10/25/beolab-5/
https://specs4audio.wordpress.com/2013/10/25/beolab-5/
I tried closed 34L with Eminence Lab12 12 inch 6 ohm. There was bass, but probably needed more xmax or box volume to be a good subwoofer. I needed a lot of EQ to make it behave okay. A shame because the box was really well built with 40-50mm thick MDF.
WinISD is pretty spot on, for such a simple program.
I will follow this thread and see what you find. I don’t want to throw away my over-engineered subwoofer box.
If Beolab 5 can go down to 14Hz with sealed 29L and 15”, I would expect that we can pull off 22Hz here with 12” in similarly sized box. I don’t need an excessive amount of power or spl, I just need to hear all the octaves. I think I’m already pretty close, so wondering if simple Fs upgrade could already make an audible difference.
I already have a box that is just about right, cube 35x35x35cm. The bass extension already runs circles around KEF Reference 3.
Zdr,
The Beolab 5, like any other woofer in a small sealed box simply uses a lot of "Adaptive EQ" (as they call it) to adjust the LF level to that of the upper bass range.
In Booger's example above, 15dB (+/- 7.5dB) of EQ is required to flatten response down to 20Hz.
Using the 22Hz FS Eminence LAB12 in a 28.3 liter (one cubic foot box) about 18dB (+/-9dB, +5/-15, etc.) is required to flatten response down to 20Hz, and ~400 watts (40 volts) are required to push the driver to Xmax.
Rewind's box would need nearly the same, more or less depending on room and location.
The LAB12 can handle 40volt peaks and just reach Xmax in a small box with no problems and relatively low distortion.
That said, the air spring, Xmax and thermal limits make ~98dB at 20Hz close to a hard limit- doubling or quadrupling power won't increase the level much at all beyond that.
At any rate, until you apply the EQ (and power) required to flatten the response of your JBL CS1210 (~ +/-10dB) or any other driver in a small sealed box, you are not going to know what it sounds like.
The DSP used determines how you can achieve the desired response- some require a combination of LP, PEQ boost and cut and HP to achieve the inverse of the frequency response required to flatten response without wasting power below the F3 desired.
Art
Yes, though not very loud (closed box):
28 L/~1.0 ft^3 = ~0.05% eff = 0.05/100 = 0.0005
112-(10*log(0.0005)) = ~79 dB
T/S Explained
T/S Equations and how each one affects the others
Loudspeaker efficiency versus sensitivity
