Sigberg Audio Manta (12" wideband cardioid active speakers) development thread

[sigbergaudio]

It's time for a new build/prototype thread!
Thank you to everyone who followed our previous threads (Inkognito subwoofer, 10D subwoofer & SBS.1 Active speakers), all those products are now commercialized and available for purchase world-wide from our website.

Our next project is the Sigberg Audio MANTA.1 Active loudspeaker. Before diving into the details, let's quickly compare it to our SBS.1 speaker, as there are several similarities. Some may notice the same ".1" at the end of the name. This indicates the same for both speakers: That it is designed to play with a subwoofer. Target -3dB roll-off point will be 90hz just like the SBS.1. It also shares the same 5.5" coax driver. For those interested in more information about the story behind the SBS.1, we recently wrote an article on that topic.

So, what's new and different with the MANTA.1?

• The MANTA.1 is significantly larger. Preliminary dimensions: 35x60x35cm (~14x24x14 inches).
• It will be a "large bookshelf", the size is similar to the JBL L-100 Classic (custom stands will likely be available)
• The bottom end is handled by a powerful 12" woofer, which means more than twice the surface area (729cm^2 vs 308cm^2) dedicated to midbass duty.
• While the SBS.1 is a 2.5-way, the MANTA.1 is a true 3-way design.
• The MANTA.1 has twice the amplifier power compared to the SBS.1
• The chamber for the coax driver has three slots on each side, aimed to control / extend directivity.

Dynamic and effortless reproduction at realistic listening levels
Our current SBS.1 active speaker can play more than loud enough for most purposes and rooms. It's precise, punchy and plays louder than any similar sized speaker without audible compression. But some want not just loud, but L O U D, and some have larger than average rooms. Thus, the MANTA.1 will carry on the legacy of dynamics and effortless reproduction from the SBS.1 and supersize it. The midbass capacity is more than twice the SBS.1. We are talking a dedicated 12" driver for midbass (rolling off at 90hz). Similar to the SBS.1 5.5" midbass driver, this new 12" driver has a stiff suspension optimized for bass/midbass rather than subwoofer duty. And while we use the same coax as in the SBS.1, since it's now a 3-way design, its capacity is significantly increased as well. All these changes of course also translate to even lower distortion at both moderate and high playback levels.

Extended directivity
With the current design (subject to change) this speaker will not be a true cardioid or constant directivity speaker, as the lower (midbass) chamber is a traditional, sealed design. So the goal is controlled directivity lower than a traditional speaker, but it will not extend as low as for instance the DutchDutch.
EDIT 2021-12-16: The speakers are now redesigned to have acoustic ports in both chambers, and the directivity is now controlled to a greater degree than a traditional speaker all the way down to 100hz. Updated description of this here: https://www.audiosciencereview.com/...ers-prototype-build-thread.28255/post-1024762

While we have a working prototype, it's still early days. We expect a lot of experimentation and possibly alternative designs before we know the final effect achieved with this approach. But we can say already that this sounds, well, different. Vocal reproduction is likely to become a particular strength. The precision and articulation of imaging / soundstage and stereo effects are also very promising.

What happens next?
In the same way we've done with our previous products, we will share photos of testing and the prototypes, measurement results, design decisions and more! The first prototypes are already up and running and the sound is very promising, so more information will follow soon! Stay tuned!

 

[hex168]

Very nice, and promising. Thanks for sharing!

 

[AlmaAtaKZ]

Interesting!

 

[Harmonie]

Active speaker with 12" >> catching my interest and I'll watch this thread.
Would you send it to Amir once the proto is ripe ?

 

[sigbergaudio]

Active speaker with 12" >> catching my interest and I'll watch this thread.
Would you send it to Amir once the proto is ripe ?

Thank you for your interest (same goes to the others who have replied)!

With regards to Amir and testing, it's a bit early to consider that just yet. Amir also doesn't automatically review anything any manufacturer sends him, especially not from new brands.

 

[sigbergaudio]

The coax driver is extremely well behaved in this design as well (this is 15 degrees off-axis, 1/12 smoothing). The unevenness below 1khz is due to this being in-room measurements.

 

[q3cpma]

If you manage to make the woofer to midrange transition constant directivity via those slots, congratulations.

 

[sigbergaudio]

If you manage to make the woofer to midrange constant directivity via those slots, congratulations.

As mentioned the lower chamber is sealed, so the effect will drop off at the crossover frequency to the woofer.

It's an option to experiment with slots across the chambers as well, but we've not built a prototype for that so far.

 

[q3cpma]

As mentioned the lower chamber is sealed, so the effect will drop off at the crossover frequency to the woofer.

It's an option to experiment with slots across the chambers as well, but we've not built a prototype for that so far.

View attachment 166785

Don't need more than the midrange chamber to match the natural narrowing of the woofer, no? The "goal" I was talking about is getting the effect of a near perfect waveguide for the coaxial driver.

 

[Absolute]

Nice! Acoustic vents like Dutch and @Kvalsvoll should extend the directivity control further down indeed. I suspect the aim is to control dispersion down to around 300-400 hz or so based on the sealed chamber for that woofer?

In my eyes this makes sense since directivity control below that doesn't really matter all that much in my experience.

One question I have about acoustic vents, will it create less interference with the driver if they're placed further back towards the rear? Based on the distortion measurements we saw with Hardisj' measurement of Dutch I expect some elevated distortion in the lower mids due to interference, so it'll be interesting to see whether that's an avoidable concern or not.

I wish you the very best on this project and I'm happy you're willing to share with us @sigbergaudio

 

[q3cpma]

One question I have about acoustic vents, will it create less interference with the driver if they're placed further back towards the rear?

Hmmm? Interference (controlled interference, that is) is the goal.

Based on the distortion measurements we saw with Hardisj' measurement of Dutch I expect some elevated distortion in the lower mids due to interference

The distortion is probably due to two reasons: being a 2-way with a bolt-on subwoofer instead of a true 3-way design and the controlled cancellation robbing some headroom (like in dipole bass). GGNTKT and Kii use additional woofers instead of the delayed back radiation from a single woofer to mitigate this.

 

[Absolute]

Hmmm? Interference (controlled interference, that is) is the goal.

The distortion is probably due to two reasons: being a 2-way with a bolt-on subwoofer instead of a true 3-way design and the controlled cancellation robbing some headroom (like in dipole bass). GGNTKT and Kii use additional woofers instead of the delayed back radiation from a single woofer to mitigate this.

Kii have the exact same problems. Controlled interference is of course the goal, but you'll have negative interference forward also, not just to the back, hence reduced output and a need for driving the mid harder to keep the spl level correct.

At least that's what I'm assuming. I'm clearly no physicist

 

[sigbergaudio]

There are a number of trade-offs here. With the current design where the woofer is a traditional sealed design, we're not loosing any capacity/output in the most power intensive area. And the sub-100hz frequencies are already offloaded to a subwoofer, so I'm not worried about loss of output at all. There's plenty to go around. On the other hand, we have no directivity control below the crossover to the woofer.

In the current very early prototype the off-axis is pretty even except a narrowing of the gap between 1-2khz. Next step is to experiment with the stuffing / dampening of this chamber to see what happens.

On-axis (red) and 80 degrees off-axis.

 

[sigbergaudio]

Updated measurement with more dampening in the upper chamber and more precise measurement (1m versus 60cm). Now we at least have a pretty even roll-off in the entire spectrum, which is a good start. As these are indoor measurements we naturally have reflections from walls etc which means I'm not sure how accurate the sound power at 80deg is here. I guess it's reasonable to assume that it will be lower in an anechoic environment.

(0deg and 80deg)

 

[sigbergaudio]

A few photos of what's obviously an early and crude prototype.

--

 

[Chrise36]

A few photos of what's obviously an early and crude prototype.

--

Can i ask how do you find the ultragraph regarding noise etc?

 

[sigbergaudio]

Can i ask how do you find the ultragraph regarding noise etc?

Well, I wouldn't use it in a home setup for listening to music, to put it that way. But it's fine for my purpose, which is to use it when tuning and testing with sine sweeps etc.

 

[sigbergaudio]

Tuning of the day (15deg)

 

[sigbergaudio]

And today.. moved the crossover points and got the top end up. Also adjusted the tonality ever so slightly.

This is roughly listening axis / ~15degrees (indoors so some noise)

 

[Ra1zel]

Looks like tweeter is giving up above 15khz?