Vera Audio midrange horn - polar measurements

[Bjorn]

Vera Audio is developing a horn speaker system. It consist of a midrange horn, a midbass horn and requires a bass/subwoofer solution. It will be active and offered with a separate high quality DSP.

The 2-horn system look like the following:

I'll show some measurements of the midrange/top horn. With the driver we're using, it's able to cover the range from approximately 500/600 Hz and all the up to the highest frequencies.

The measurements of a prototype horn were conducted in a small gym with the ground plane method.

Due to size of the facility, the measuremen isn't anoechoic and we couldn't measure far enough away in order to get the beamwidth 100% correct. The horn has a likely a narrower directivity then what's seen in these measurements. New measurements under better conditions will be made later.

The horizontal directivity without any gating looked like this:

A gating with 24ms isn't sufficient to rule out all reflections as there were reflections arriving as early at 15ms at certain angles, but is shown below:

The horn was also measured vertically.

Vertical directivity with no gating:

Vertical directivity with 24ms gating:

Conclusion
The midrange horn measured with an extremely uniform directivity. Horizontally the directivity is text book apart from a small widening at 800-900 Hz. Vertically the polar is also very constant with some minor abberations. The horn is able to maintain direcitivity both high in frequency and very low in frequency which is unusual for speakers. How low exactly will require measurements in a more anechoic environment.

https://www.vera-audio.com/

 

[thewas]

Looking good, would be interesting to see in the future the directivities combined with the midbass horn.

 

[Bjorn]

Looking good, would be interesting to see in the future the directivities combined with the midbass horn.

I'll start a new thread when the time is right, but I can show some vertical measurements of both horns indoor. The room is about 40 m2 but it's L-shaped and there's cathedral ceiling. The sloping ceiling comes down behind the mic here, and ceiling height above the speaker is quite low. So this will effect the measurements some.
So here's the Vera Audio Sagarmatha 2-way horn.

This measurement was performed with our Vera Audio dual 18" subwoofer. Cross over at 120 Hz in this case. This subwoofer has some serious output capability, and obviously something that's needed to keep with our 2-way horn. And while it's not directly small, it's not huge either. Sorry for the cable and amp mess.

Not many will show measurements above a reflective floor. But this is IMO important because it's how the speaker will behave in a listening environment. Nice anechoic vertical polars doesn't necessarily lead to an even frequency response placed in the room. We designed this horn with this mind and it's possible we'll only present final vertical measurements this way but in a large space with heigh ceiling height.

The distance here is 2.8m, a typical listening distance for many. We're using a Hypex DLCP and at the moment with no FIR filter. For the final production model, a FIR filter will be used to achieve a linear phase and possible some other improvements.

Let's start with seeing how the horn measures when placing the mic at the floor. 1/6 octave smoothing (all indoor measurement with no gating).

Mic placed 25 cm above floor. 1/6 oct smoothing:

Mic 55 cm above floor. 1/6 oct smoothing:

Mic 85 cm above floor. 1/6 oct smoothing:

Mic 100 cm above floor. Now we're at typical ear height. 1/6 oct smoothing:

Mic 130 cm above floor. 1/6 oct smoothing:

And finally mic placed 160 cm above floor. 1/6 oct smoothing.

Notice that we don't really have any serious vertical lobing here in practise, despite the distance between the two horns and we're using a IIR filter at crossover.

Let's loook at some overlays. I'm showing these with 1/3 oct smoothing which is the normal standard.

Obviously the low frequency changes with height and that's excepted in an acoustical space of this size. We can therefore also look at a graph above 100 Hz:

So this is a measurement above the reflected floor from floor to 160 cm above at 2.8 m distance. And with room influence, though we have some treatment. There's only one absorber at one side wall and three in the ceiling behind the mic where the ceiling is sloping downwards (wouldn't bee needed with a flat ceiling). There are four diffusers and two BAD Arcs (hybrid diffusion/absorption) on the rear wall and some bass traps in the room. I would say this quite unusual for a speaker to measure this even at various height above a reflective floor and with a ceiliing that's also mostly reflective.

 

[thewas]

What is the crossover frequency between those two horns, guess quite low so there is no lobing observed in the LP measurements?

 

[Purité Audio]

Purely aesthetically would it be possible to make both horns with the same width dimensions without spoiling the measurements which look super. What is the front to back ( mouth of horn to rear of driver) measurement?
Thanks,
Keith

 

[Bjorn]

What is the crossover frequency between those two horns, guess quite low so there is no lobing observed in the LP measurements?

600 Hz in this measurement. But it might be eventually lowered some. Need to do more testing but likely to end up in 500-600 Hz area.

 

[Bjorn]

Purely aesthetically would it be possible to make both horns with the same width dimensions without spoiling the measurements which look super.

I was hoping people wouldn't ask for that! Personally I like that the fact that form follows function and where the midbass is wider because it's needs to be in regards to directivity control. I guess it's possible but not sure I want to do it unless the demand is high.

What is the front to back ( mouth of horn to rear of driver) measurement?
Thanks,
Keith

You mean length/depth of the horns I assume. Length of top horn including compression driver is about 66 cm. With the present rear chamber, the lenght of the midbass horn is approximately 113 cm. But I plan to increase this to about 119 cm. The rear chamber can be in various lengths though, if someone can't go with the full length. A shorter rear chamber doesn't make a big difference.

 

[dasdoing]

I want

 

[Purité Audio]

Thanks Bjorn, just thinking about installing in domestic rooms, what would you suggest is the minimum listening distance ?
In the finished product will there be a way of attaching both horns to each other or will the top just rest on the bottom?
will both horns be finished in the same veneer on your site their is a black horn?
Best wishes,
Keith

 

[Bjorn]

Thanks Bjorn, just thinking about installing in domestic rooms, what would you suggest is the minimum listening distance ?
In the finished product will there be a way of attaching both horns to each other or will the top just rest on the bottom?
will both horns be finished in the same veneer on your site their is a black horn?
Best wishes,
Keith

Minimum listening distance about 1.8 m.

The top horn is attached to poles on the midbass horn. And it can be tilted up and down by unscrewing two knops.

Plus it rest on a slit with foam in the alu list.

I know the rear poles aren't pretty. But it was challenging to come with something that both would look good and make the top horn adjustable in an easy matter. This would have been a lot easier if the rear chamber was square instead of circular. I guess we could add some larger circular tubes to cover the "duck feet" and make it look beefier. But not sure if it's needed when it's in the rear of the speaker. Might have to do if we sell to the Middle East!

 

[Duke]

600 Hz in this measurement. But it might be eventually lowered some. Need to do more testing but likely to end up in 500-600 Hz area.

My understanding is that the ear's vertical discrimination falls off rapidly below 1 kHz, so I would expect the image height to be solidly at the center of the upper horn.

What a beautiful loudspeaker, even aside from its outstanding measured performance!

 

[Bjorn]

I want

Would be great to have a pair in Brazil. Shipment is likely very though.

 

[fredoamigo]

Being optimistic, when do you plan to start marketing? I don't remember ever seeing such measures.

 

[Andrej]

Beautiful horns! Given their size, and the apparent thickness of the horns, are you concerned with resonant vibrations? Also, given that the approximate x-over frequency is around 600Hz, why do you need such a large horn for the high frequency driver?

 

[Bjorn]

Being optimistic, when do you plan to start marketing? I don't remember ever seeing such measures.

It's not entirely in our hands. Since we have betted on using an external DSP and not developing our own, we've been waiting for this for quite some time. And these units have been delayed for perhaps as much as a few years now. They are still in beta versions or being upgraded with new hardware.
My guess is March at the earliest.

 

[Bjorn]

Beautiful horns! Given their size, and the apparent thickness of the horns, are you concerned with resonant vibrations? Also, given that the approximate x-over frequency is around 600Hz, why do you need such a large horn for the high frequency driver?

We've measured with an accelerometer in the development.

The first midbass horn was built with 21 mm plywood and rear chamber had two layers of quite thick plywood with viscoelestatic glue in between. It can be challenging to relate measurements of cabinet resonances to what's audible and it's likely very dependent on how good control there is of room resonances, but we found out that 21 mm thick plywood was perhaps lacking a bit.

The second prototype we experimented with a combination of light weight and stiff materials in order to avoid high weight. Basically quite similar to what is used in airplanes. This was both expensive and not as successful as we hoped for.

So we went with 25 mm plywood in the third prototype. Combined with bentness, that gives very high stiffness. However, we will add to some bracing additionally to the final model. That may be overkill and unecessary, but it's better to be on the the certain side plus cost doesn't increase much.

As for the top horn, this is built with very stiff and light weight material and resonances here have never been an issue. We used a well known and big horn to compare with. Almost everyone said this particular horn didn't have audible resonances, but it was evident it did when we compared it to our stiffer (and lighter) horn. Sometimes we don't hear certain issues before you have a better reference to compare with.

If you cross over at 500-600 Hz, you ideally want directivity control lower than the crossover. How much lower, depends on the steepness of filter. Plus, if a new driver is developed in the future that is equally as good in the highs and be crossed even lower, we have a horn that fits that too. And the customer can easily upgrade.

We've found the ability to also have a constant vertical directivity low in frequency a clear advantage and this is often a breaking point with many other horns. Even quite large horns out there, start to loose the directivity around 1000 Hz.

You can see that our top horn is very uniform to about 500 Hz and than is gradually becomes wider. This means less coloration from the room's surfaces.

 

[hvbias]

Are there any rough estimates on prices? Thanks.

 

[sigbergaudio]

Would it be possible to post the polar patterns with the 30dB range that is "normal" from for instance spinorama.org? With -6dB being a light blue shade and the scale "bottoming out" at -10dB (or -13dB in the horizontal graph), it's a bit difficult to compare, and it looks more narrow than it really is.

 

[Bjorn]

Are there any rough estimates on prices? Thanks.

I'll try to get back with a rough estimate with one DSP.

 

[Bjorn]

Would it be possible to post the polar patterns with the 30dB range that is "normal" from for instance spinorama.org? With -6dB being a light blue shade and the scale "bottoming out" at -10dB (or -13dB in the horizontal graph), it's a bit difficult to compare, and it looks more narrow than it really is.

I used 15 dB range in the meaurements above. It's important to understand though these polar are not anechoic and measuring distance for such a large horn needs to be further away in order to get the beam width in angles correct. The beam width is narrower than what these polars show. The widening is an effect of measureing too close up. Getting 100% anechoic measurement of such a large horn is challenging and I may have to ship one to NWAA labs to get that.

Here they are with 30 dB range. Horizontal first and vertical second. No gating used.