Bass from a 3" driver with small box for computer speakers - diyAudio
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Old 19th August 2012, 12:01 AM   #1
deandob is offline deandob  Australia
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Default Bass from a 3" driver with small box for computer speakers

All,

I'm looking at building a pair of computer (near field) speakers which are reasonably compact but also have decent bass. Having built a number of designs previously the ones that work best are the 2.1 design (full range driver crossed over at 80Hz with a sub). This time around I'd like to build a pair without the sub with the aim to maximize the bass response to replace a design using W3-871S speakers that do a reasonable job but the bass is poor.

So the challenge is to get as much bass from a 3" driver without resorting to a subwoofer or a large box (5 to 7L ideally), and prefer to have it run full range if possible. Quite difficult to do but am willing to compromise top end response or distortion specs if needed.

Doing research on this topic has come up with several considerations:
- Sealed box using a Linkwitz transform, but needs a driver with high x-max and high power capability.
- vented box but will require a driver with high x-max and a high pass filter below the resonant frequency to avoid distortion & possible damage with such a small speaker.

Looking at Zaph's small driver test was very helpful and the clear winner for this application is the Aura NS3-193-8A / Dayton ND90, which has decent lower frequency response and huge x-max for such a small driver. Punching the TS parameters into WinISD shows that I can run this driver with a 6 or 7L box with a tuned port and get down to about 40Hz, which would be perfect. Also feedback about this driver and its bass response is very positive, and its high frequency response up to about 15K is decent although the distortion is a little higher than equivalent drivers according to the Zaph tests.

I think the vented option is the preferred approach (a LT sealed design has the potential to blow the driver) but I'm not sure how this driver would work vented as its so small and most designs I have seen for it are sealed. Also I'm not sure if the WinISD results are correct for a small driver in a vented box.

For those with more experience in speaker design I have a couple of questions:
- Is it practical to have such a small driver running vented & get reasonable performance?
- Am I correct that sealed LT won't work and vented is better for extended bass (even though transient response suffers)?
- Can I trust WinISD results with such a design?
- What T&S parameters apart from xmax are important for extended bass from a small driver?
- Are there any other drivers that I could consider for this application (small box, extended bass)?

Anything else I should consider? Thanks for the feedback!
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Old 19th August 2012, 12:16 AM   #2
Bigun is online now Bigun  Canada
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Quote:
Originally Posted by deandob View Post
All,

I'm looking at building a pair of computer (near field) speakers which are reasonably compact but also have decent bass. Having built a number of designs previously the ones that work best are the 2.1 design (full range driver crossed over at 80Hz with a sub). This time around I'd like to build a pair without the sub with the aim to maximize the bass response to replace a design using W3-871S speakers that do a reasonable job but the bass is poor.

So the challenge is to get as much bass from a 3" driver without resorting to a subwoofer or a large box (5 to 7L ideally), and prefer to have it run full range if possible. Quite difficult to do but am willing to compromise top end response or distortion specs if needed.
this has worked well for me

MARTELLO enclosure for FR88EX
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Old 19th August 2012, 12:57 AM   #3
deandob is offline deandob  Australia
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Thanks Bigun. The FR88EX does not seem to go as low as the NS3 and a much smaller xmax (so will be difficult to force extra bass via vent or LT) although a similar model FR89EX shows more promise with a +5mm xmax but still doesn't go as low as the NS3.

BTW - nice job on your enclosures!
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Old 19th August 2012, 01:21 AM   #4
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I used an el70 in 7L, but if stuck on a 3" I'd go NS3 in a 0.5q sealed box with an LT. The eq available in windows 7 was good enough for me.

In this application though, more power is required.
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Old 19th August 2012, 01:49 AM   #5
deandob is offline deandob  Australia
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Yes, LT requires a lot of power (and a driver that can handle the power). Why the LT over vented (vented is a simpler solution for similar bass gains)?
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Old 19th August 2012, 02:09 AM   #6
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You want good bass from a 3"er, which is an oxymoron. However, Psychoacoustics tells us that you only need to get to 80Hz to "hear" the bottom end of all acoustic instruments. The complete harmonic series of, say, the double bass lies above 80 Hz. Our brains recreate the fundamental from for the harmonic series. What you will never get from a 3" driver is slam. Forget it.

Bob
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Old 19th August 2012, 02:17 AM   #7
deandob is offline deandob  Australia
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Bob, I'm aware that I'll never get SPL or fill the room with bass with a 3". The objective of this design is to try to get as much bass as possible (without overloading the driver) for a near-field listening situation, to avoid having to make a sub.
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Old 19th August 2012, 03:09 AM   #8
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NS3 is certainly the bass king as far as 3: drivers go... really low efficiency is the price you pay.

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Old 19th August 2012, 03:27 AM   #9
deandob is offline deandob  Australia
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Any other feedback about LT vs vented for extended bass response for such a small driver?
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Old 19th August 2012, 03:33 AM   #10
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If the Qts of the driver is below about 3, you can maximise the bass by using a 5th order quasi-butterworth alignment. See here: Satellites and Subwoofers
You'll need to apply some equalisation, but the filter required does provide a high-pass function to reduce below-resonance excursion.
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