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DIY 2-way with complete spinorama / CTA2034A measurements - Purifi and Scan-Speak

Driver and crossover choice

  • Active with aluminium cone

  • Active with fibre cone

  • Passive with aluminium cone

  • Passive with aluminium cone

Results are only viewable after voting.


Addicted to Fun and Learning
Forum Donor
Mar 27, 2019

Project brief-

To design a small speaker with a big sound, with the aid of the Klippel Near Field Scanner for complete measurements in 360 degrees!

Classic 1/2 cubic foot (14L) 2 way with 6.5" midwoofer / 1" tweeter, stand-mount
Driver selection:
Midwoofer: Purifi 6.5" Xtended x-max aluminium cone, https://purifi-audio.com/ptt6-5x04-naa-08/
Tweeter: Scan-Speak 26mm dome tweeter with low Fs: https://www.scan-speak.dk/product/d2604-833000/

Natural in-room bass down to 40Hz, High power handling / low compression design
Optimised for smooth in-room response and class leading harmonic distortion
Easy to build design - no large roundovers, no facets.
Designed the Toyota way- easy to repair and easy to get replacement parts (Purifi and Scan-Speak), not closeouts or drivers that may disappear without notice.
Designed for free standing (>60cm from front wall ideal)
Stretch goals- optional close to wall, or against wall or desktop mounting (no ETA), facets near tweeter for smoother treble response (no ETA)

Verified by Klippel Near Field Scanner: high resolution accuracy (2Hz, +/- 0.3dB) out to 360 degrees horizontal and vertical)
Active crossover completed
Passive crossovers to come (no ETA yet)
paper cone variants to come (no ETA yet)

Pictures to follow: Updates via my FaceBook page.

The measurements and design alone costs US$500-1000.

How to order- Donate to your favourite charity and send me proof of donation via PM.
With a message "Danish Duo" in your PM- a password protected PDF file with the plans will be emailed to you.

PS. Pictures to come this weekend
Pre-orders starting soon.

Full disclosure: I sent the speaker to be measured a month ago. Erin did not ask for any funds, and agreed to measure them “for the benefit of the DIY community”

I decided release it as “donate-ware”; All correspondence and enquires should be sent to me...

No kickbacks were involved in the design of this speaker. ie. I bought and paid for everything. 1 Purifi driver was killed when my prototype cabinet fell from my rotating turntable.

Thanks to cabinet maker who built my cabinet and Purifi and Scan-Speak who built the drivers and Erin Hardison who measured them, but I doubt they will comment on them.

This is my project, for better or worse.

Edit: No idea where to donate? visit www.givewell.org and do a bit of charity shopping…
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Really cool project.

I don't have crapbook. Is there another forum or place that you are posting the info? Is Erin going to talk about this?
Really cool project.

I don't have crapbook. Is there another forum or place that you are posting the info? Is Erin going to talk about this?

You don’t have to follow crapbook. It’s just may be faster to get a response that way.

Edit: updated disclosure-
With no tweeter waveguide and no baffle roundover, won't this project just end up being a slightly worse Directiva R1?
One might think that, huh?

I won’t comment on other people’s designs, there are pros and cons of all loudspeakers.

I’ll tell you what I have to offer:
This one has a preference (tonality) score of 6.9

Here’s my main speaker 3 way, which was the reference comparison for this design.
Yeah, that is distortion is at 100dB.

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Double 12” woofers.

System sensitivity true 92-93dB @2.83V anechoic.

No ports. No sub. No bass boost (excess group delay)

They “only” go down to 40Hz.
Except Like dynamite.
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Double 12” woofers.

System sensitivity true 92-93dB @2.83V anechoic.

No ports. No sub. No bass boost (excess group delay)

They “only” go down to 40Hz.
Except Like dynamite.
Thinking of a double 12" SB34NRXL75 instead of a single 18 to save some space, crossed at 250 ish, what do you think?
No experience with that woofer, sorry.

It models and measures well though, what's holding you back? Sometimes you have to take the next step...
I’ll tell you what I have to offer:
This one has a preference (tonality) score of 6.9
I don't put a huge amount of stock in the preference score, because while useful it doesn't account for time domain performance of speakers. For example, with a revised crossover I can get a $165 Samba MT kit to do a 6.5 preference score without sub, 8.1 with sub. Or the Affordable Accuracy Monitor can do 7.9.

But to my ears, both sound distinctly worse than a KEF R3 which has a similar 8.1 with sub score, and the primary design distinction seems to be cabinet and waveguide quality.

Please don't take this as attacking your design, I am just curious what you benchmarked these against so that I can better understand the strengths+drawbacks of the design.
Good that you are aware of the limitations of the preference score. I agree.

But If it aint got shorting rings in it I don't bother.

I wouldn't bother with Affordable Accuracy Monitor- too constrained in dynamic range. Of course it might be suitable for smaller rooms or BGM.
And the Samba MT- Goodness what happened?!

KEF R3? let me tell you I wouldn't bother. It’s a design built to a price.
KEF R5 meh…
KEF R7 that’s a bare minimum.
KEF R11 that’s better
Reference 5 META now we're talking
Blade 1 META, I'd like to listen first.

Because KEF Blade 2, no thanks. (Auditioned-pic below)
Dutch and Dutch 8c, no thanks (auditioned- pic below)
Genelec 8351B, no thanks (auditioned, not pictured)
Genelec 1238DF, now we’re talking


Revel F328 BE? YES.
This is something I might consider buying.

Listening Perth.jpeg

what it really did do was inspire me to finish off these DIY speakers that I started a decade ago, but life (marriage, kids) got in the way:

Music & Design's NaO II monopole/dipole hybrid (NLA)
Because even the 1 mono speaker that I had, built a decade ago, beats a stereo pair of Revel F328 BE in a carefully set up showroom.

So I should really finish off that 2nd speaker...
NaO II RS.jpeg

DIYers like Sigfried Linkwitz and John Kreskovsky built things because nothing in the commercial market was good enough for them. All the hi-fi industry did was go around in circles putting drivers with fancy cones in fancy cabinets with increasingly stratospheric prices. I’m looking at you Kharma.

I'd bother with the Philharmonic Audio BMR Tower. But no to the Monitor. Just ask @Dennis Murphy

That's my reference.

When Amir started testing amplifiers, I offered him the Hypex NC400 dual mono, Hypex NC400 stereo, and Hypex UCD400 mono to test. He was a bit surprised- what is this thing?and why so many variants?

Because I have a fully active tri-amped system driven by DSP. Like a decade ago. We were building speakers and amps not because we wanted to, but because we had to build them; the manufacturers hadn’t, or wouldn’t.

Just ask @mac. He’s been doing active and signal processing (digital and analog) for decades…

I drive a Toyota hybrid, living room on wheels. It takes me to/from work, picks up the kids but gets me groceries. It’s about as meh as cars go. Many people balk at spending $1000 on speakers,

But I don’t have a problem spending $20K on a music system.
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Like all your relations, you didn't ask them, but they're all coming for Christmas: :eek:

eXtra Small rooms 26 x 13 x 17cm (LxWxD) featuring 4.0" Purifi PTT4.0X-04: -3dB extension: 55Hz

...Cabinets in progress

Small rooms 30cm x 20cm x 20cm; featuring 5.25" Purifi PTT5.25X-04 : -3dB extension 45Hz
Cabinets done
Drivers mounted
... Design to come

393180C4-3FFE-48B9-93BB-68E0D22C9A12.jpeg 7B4925DB-C8BD-45BB-84FC-2C452BCDA60D.jpeg

Medium rooms: 40cm x 20cm x 30cm featuring Purifi 6.5X04-NAA-08; -3dB extension 40Hz

Cabinets done (first post- speakers on far left and right)
Driver's mounted and measured
Design completed- optimised for smooth in-room measurements.

CTA2034A Measurements:


No smoothing applied*

Large rooms: 8” Purifi Alu- TBA

Drivers in house:


eXtra Large rooms: Twin 8" midwoofers, midrange TBA, tweeter TBA

*Verified by Klippel Near Field Scanner: high resolution accuracy (<2Hz interval accuracy, +/- 0.3dB vertical accuracy) out to 360 degrees in horizontal and vertical planes)
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Very interesting. Looks to be about the same in cost to the ascend sierra lx, a little more narrow in directivity throughout the treble, a little more bass, and a very premium woofer.

What's the best way to find our way to your fb?
I've had a few comments about fb. And I totally get it, having closed my personal fb account in 2012 before their IPO.

I'll probably set up a Discord group. Stay tuned as designs get closer to completion.

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This guy's on a roll. Nice work
Yes. Beautiful. They look like they were made for each other!

Thanks for the tip-off.
For the original M sized (post #1), active crossover completed.


Phase response:

Reverse null:

Polar response to +/- 45degrees horizontally and vertically:
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