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Old 26th April 2016, 05:25 AM   #1
bcodemz is offline bcodemz  Canada
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Default Nucleus: my attempt at building the best sounding small speaker I can

I'd like to share with you guys something I've been working on and off for a while now. I call it, the Nucleus, and it is my attempt at making the best possible sounding small speaker I can possibly make without too much regards to budget. I thought it would be much more interesting to try to build something that far outperforms anything commercially available, and something that hasn't really been tried before: making a small speaker sound truly good.

Goal: To make an extremely high fidelity small sounding speaker with strong bass down to 45Hz in an enclosure no bigger than 0.1 cu ft.

Click the image to open in full size.

I wanted something that's visually obtrusive, so after much modelling, I ended up settling for a speaker that is 13'' wide, 5'' high, and 5'' deep. This is built on 1/4'' plywood of the highest grade to maximum internal volume. The midrange chamber inside acts as bracing for the speaker to provide additional strength. A nice rosewood stain was used to finish the enclosure.

The drivers consist of the Scanspeak Illuminator D3004/6020 for the tweeter crossing to the the Scanspeak Discovery 10F/8424G midrange at 3000Hz and crossing to the Tangband W4-1720 for the woofer at 300Hz. 2 custom Peerless 4'' passive radiators were used to tune the speaker to 46Hz. A miniDSP 2x4 is used as an active crossover as well as 2 SMSL SA-50 amps powering the drivers individually. The miniDSP was absolutely critical in bringing out the magic from these amazing drivers. Not only this is used to do 4th order crossovers, but it was necessary to correct box resonance from the high Q, diffraction effects of the baffle, and most importantly, the bass boost for woofer to bring out the bass, as well as the high pass filter and the limiter to keep the woofer in check.

If I'm going this far for this project, I might as well pull out all the stops. Extensive testing was done to tune the speakers. And the results? A speaker.that measures 1dB from 100Hz to 16KHz with a -3dB roll off at 20KHz and a rise in bass response starting from 100Hz to +3dB at 50Hz. Here's a measurement done in anechoic chamber. There is no smoothing applied to the graph. Any smoothing to the graph will result in essentially a straight line. All the little bumps are actual response of the speaker as the microphone is very very high resolution. The chamber was only good down to about 100Hz, so that's where it stops. The second picture is an outdoor ground plane measurement for the bass. Again, that's with no smoothing.

Click the image to open in full size.

Click the image to open in full size.

So how does it sound? Just utterly fantastic. It is surreal hearing such high fidelity coming out of something so small. The Scanspeak drivers are truly excellent that just oozes detail and resolution. The clarity and detail is just outstanding that rivals some of the best speakers I've ever heard. The bass coming out of this speaker is truly astounding. The Tangband woofer is outstanding. It just pumps smooth and strong deep bass that is rather unbelievable from a speaker so small. At normal to above average listening volume, it absolutely sounds like a subwoofer is playing as the distortion is very low even at very high excursion levels. I've bought this to the office where I was pounding the speakers with rap and it just blew me away how much deep bass this speaker can produce. One caveat though, some music that really uses the stereo effect sound a little weird a mono, but that's just because there's only one speaker. But still, I am beyond happy how this turns out. It was an absolute blast designing and building this speaker, and it is truly satisfying when things come together beautifully. Small speakers can't sound good? You can't get bass from a small speaker? Oh yes, you absolutely can.

Last edited by bcodemz; 17th June 2016 at 04:12 PM.
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Old 17th June 2016, 01:18 PM   #2
BYRTT is offline BYRTT  Denmark
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Looks great thanks sharing hard work.
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Old 17th June 2016, 01:33 PM   #3
Zvu is offline Zvu  Serbia
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There's that small hill visible that starts at about 950Hz up to 1600Hz. It is in the very sensitive part of listening spectre. You could treat it with low Q mild notch. Other than that it looks great.
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Last edited by Zvu; 17th June 2016 at 01:39 PM.
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Old 17th June 2016, 04:51 PM   #4
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Very nice! I may be a heretic, but I would love to see your in-room measurements. What is it like at your chair? Those mini-Scanspeak tweeters are the bomb.

Best,


Erik
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Old 17th June 2016, 05:24 PM   #5
xrk971 is online now xrk971  United States
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Superb choice of drivers and excellent execution. Great work!

My only suggestion that could improve this to the next level (and you have it at your fingertips) is to make it transient perfect, or quasi transient perfect. Percussion, pianos, plucked bass rimshots, will sound entirely convincingly real.

To do that, you have to get away from LR4 symmetric XO's as they are phase wrapped and you won't be able to reproduce a square wave. I know, music ain't square waves - but, if you can do them it means your transients will be snappy and time accurate.

Try the Harsch XO for the woofer to mid, and maybe 1st order symmetric from mid to tweeter.

So woofer LPF is 4th order BW at say 700Hz, mid HPF is 2nd Bessel at 700Hz (with delay added to mid and tweet equal to half period cycle at 700Hz), and mid 1st order LPF at 5kHz, and tweeter 1st order HPF 5kHz. All drivers +ve polarity and tweeter may require a little delay adjustment. I assume you have FRD's for all already so, just pull up Xsim, PCD, or Boxsim, whatver you use to simulate. Put the textbook targets from above and start tweaking the XO curves and EQ. EQ flat first then apply XO.

Once you hear transient perfect - you won't go back.

S. Harsch XO
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Old 17th June 2016, 05:47 PM   #6
bwaslo is offline bwaslo  United States
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Or switch to a MiniDSP 2x4HD and use its FIR EQ and Rephase software to alter the phase to transient perfect. It could only be so horizontally at one height, though, since the non-coincident driver arrangement would prevent that vertically. (Not saying that it necessarily matters....)
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Old 17th June 2016, 06:41 PM   #7
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Hi Bill,

Do you have any thoughts on miniDSP and Rephase vs. Dirac Live? I've thought about Rephase, but my head spins when I look through the "easy" documentation.

Erik
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Old 17th June 2016, 08:06 PM   #8
bcodemz is offline bcodemz  Canada
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Quote:
Originally Posted by eriksquires View Post
Very nice! I may be a heretic, but I would love to see your in-room measurements. What is it like at your chair? Those mini-Scanspeak tweeters are the bomb.

Best,


Erik
Here it is. This is from ~12 feet away, with a ~8dB bass boost and 1/24 smoothing. The room acoustics is not great...

Click the image to open in full size.

Quote:
Originally Posted by xrk971 View Post
Superb choice of drivers and excellent execution. Great work!

My only suggestion that could improve this to the next level (and you have it at your fingertips) is to make it transient perfect, or quasi transient perfect. Percussion, pianos, plucked bass rimshots, will sound entirely convincingly real.

To do that, you have to get away from LR4 symmetric XO's as they are phase wrapped and you won't be able to reproduce a square wave. I know, music ain't square waves - but, if you can do them it means your transients will be snappy and time accurate.

Try the Harsch XO for the woofer to mid, and maybe 1st order symmetric from mid to tweeter.

So woofer LPF is 4th order BW at say 700Hz, mid HPF is 2nd Bessel at 700Hz (with delay added to mid and tweet equal to half period cycle at 700Hz), and mid 1st order LPF at 5kHz, and tweeter 1st order HPF 5kHz. All drivers +ve polarity and tweeter may require a little delay adjustment. I assume you have FRD's for all already so, just pull up Xsim, PCD, or Boxsim, whatver you use to simulate. Put the textbook targets from above and start tweaking the XO curves and EQ. EQ flat first then apply XO.

Once you hear transient perfect - you won't go back.

S. Harsch XO
The next speaker will be a much better design than this one that'll correct all that. It'll be a 3 way speaker that sounds and measures like a point source. It will be near phase perfect with FIR filters on the upgraded miniDSP 2x4 HD and a crossover that'll result in no horizontal or vertical lobing error.

I learned a lot from designing and building this speaker. I wish I can change the title, because it is not the best sounding small speaker ever. The next one though will be very, very close.

Last edited by bcodemz; 17th June 2016 at 08:15 PM.
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Old 17th June 2016, 08:18 PM   #9
xrk971 is online now xrk971  United States
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Can you show us the harmonic distortion plots vs frequency at a reference level of say 85dB or 90dB at 1m?
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Old 17th June 2016, 08:44 PM   #10
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Hi bcodemz and all, as bwaslo meant, midrange and tweeter are not acoustically coupled; thou could have at least slipped the rim of the latter under the one of the former. And as X meant, impulse respone needs further work (the advantage of Harsch X is that it is digital time only, say a CMOS bucket chain, but not digital time and amplitude, say a clocked binary computer).
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