Introduction of Vera Audio Coherence 12 speaker

[Bjorn]

Introducing the Vera Audio Coherence 12 speaker. A speaker that now can be pre-ordered for a discount.

The prototype (one of many) without feet attached looked like the picture below (disregard the wooden plate it's standing on).



Since than we have made some smaller changes to the cabinet and base now looks different. Will get back with updated pictures.

In this thread I'l both share design thoughts and measurements along the way. Vera Audio is a company that wants to be be transparent about what we do and share proper measurements.

This is an active design with the choice of either built in Hypex FA252 plate amplifier or sold with an external crossover as miniDSP Flex (various options), Danville dspNexus. DEQX is also possible. 4-channel amplification is needed when choosing an external crossover and this can be chosen freely by the customer.

Unfortunately prices have gone up lately, but prices below for a pair is still possible with pre-orders.

1. A pair with a balanced 4-channel miniDSP Flex: $5300 excl. VAT and excl. shipping

2. A pair with built in Hypex FA252 amp: $6200 excl. VAT and excl. shipping

These prices are for glossy painted cabinet. Veneered cabinet will cost more and may vary with type. We can do custom finishes with pre-orders. Please contact us.

Lead time is approximately 5 months from pre-order. It could go faster, but that's uncertain.

Will get into the design in the coming posts.

 

[Bjorn]

General goals of the design

- From the very start of the design, a coherent sound stage was a requirement. Based on experience and testing, getting the crossover far away from the sensitive area is important for a speaker to sound more like real instrument and voices. For a speaker of this type, this meant either using one driver that could cover a large frequency area or a coax. A large amount of drivers have been tested, which I will get into later.

- Coherency, among other features, required an active design. So a passive speaker was never considered. Going active means drivers can be perfectly time aligned, so they arrive at listener’s ear simultaneously. Active also opens the door for other benefits.

- Having directivity control was another primary goal. A uniform directivity is important for a correct tonality, especially when room treatment is sparse. With a uniform directivity, the reflected energy from the room will to a much greater degree resemble the direct signal.

- However, a uniform directivity doesn’t alone mean that a speaker will yield an even response when actually placed in a living room. What good is it if the speakers only measures well anechoic. So another important design goal was to have a speaker that actually measured very even when placed in living rooms.

- The speaker needed to be engaging to listen to. Large speakers with bigger drivers can simply do things smaller cannot. The combination of a low baffle step where more sound is being send forward towards the listener with a good size woofer lay the ground for this.

 

[Bjorn]

Sensitivity and SPL

The sensitivity of the speaker is around 95 dB.

As I'm sure many of you know SPL will vary with frequency. So rating the speaker with a certain SPL can be misleading.
But the speaker can play loud, and especially at the important midbass area where often the highest SPL is needed. One single speaker can reach above 120 dB at 1 m at peaks.

Every speaker will drop SPL at the lowest frequencies. However it reaches high SPL in the subwoofer frequencies too. About 113 dB without room gain from walls at 30 Hz from one speaker. With the second speaker and possible room gain, level can easily exceed 120 dB. Will need a serious subwoofer or several to keep up with it! So adding something like one 15" subwoofer in a large bass reflex would actually minimize the total SPL in the subwoofer range.

 

[Bjorn]

2 way design and bass reflex

The speaker is a 2-design and active as mentioned before with the choice of either built-in plate amplifiers or external electronics.

The top driver is a planar transducer that covers the tweeter and most of the midrange. Bottom driver is a 12” woofer.

During the development, a large amount of drivers were tested. These two drivers were picked because of the best sound alone and not due to price. I can tell you that the most expensive drivers are not always the best, neither in regards to measurements or how they sound.

The planar driver has super low distortion combined with high sensitivity and good power handling. This driver did something we didn’t achieve we neither smaller broadband drivers or coaxial drivers. More about this later.

And the 12” woofer is the best we tested and offers very low distortion, high sensitivity and high capacity.

It’s a bass reflex design. It would not be possible to reach the high SPL in the lows with a sealed enclosure. While bass reflex has gotten a negative rumor among some audiophiles this has very much to do with either too small enclosure or/and too short/small ports/vent. But that’s not the case here, and bass is both powerful and tight. Besides considerably higher SPL than a sealed box, we also achieve lower excursion and distortion. This is one of the benefits of a larger enclosure.

 

[Bjorn]

Directivity

Let’s talk some about directivity, which is a huge topic in itself. The goal was a uniform horizontal and vertical dispersion over a wide area. A general weakness with many speakers today is that they only have a constant directivity in the higher frequencies. For example above 1 KHz and below this the directivity control is lost and we then have what was called a collapsing polar in acoustical circles. This leads to a difference in the reflective energy, and IMO such speakers don’t sound tonality correct, especially with little or no acoustic treatment.

With Coherence 12 we therefore wanted a speaker that could maintain the directivity much lower in frequency. The horizontal dispersion is 180°, meaning 90° to each side. According to Harman/Toole wide dispersion like 180° is a benefit. But I think this depends very much on the room and how one listens. I believe both wide and narrow horizontal dispersion has its place and what’s better will depend.

Originally, we wanted to maintain the wide dispersion in high in frequency as possible. Doing that with a wide band driver is challenging though, because such drivers are larger. Something we experimented quite a bit with was using an acoustical lens to keep wide directivity high in frequency. This wasn’t completely successful as it lead to other issues.

By using a coxial driver it’s easier to maintain directivity in the higher frequency. We tested a good number of coaxial drivers and did AB tests besides obviously measuring. The problem with most coxial drivers are frequency deviation as the two drivers effect it each other. They neither sounded or measured as well as other options. Below is a crude indoor measurement of a coaxial driver used in a prototype. No gating is used.



After testing many drivers we had initially landed on a wide band driver. This driver could cover a large frequency area, maintained the 180° dispersion quite high in frequency, and sounded like a good piston tweeter in the highs. However, we made a decision to try out several other types of drivers, and among these were several planar/ribbon transducers. Two of these sounded incredible good, and one slightly better than the other. Despite that the planar driver narrowed horizontal earlier in frequency, it had a clarity, detail and insight into the music material the piston driver couldn’t match. So it was an easy choice.

The directivity of the planar driver changed the dispersion of the speaker. The speaker narrowed now earlier in frequency horizontally. The narrowing from 180° starts around 5 KHz. One can discuss if this is negative compared to maintaining a wide dispersion in the highs. I think there are valid points for both sides.

Vertically by changing from the piston driver to the planar we went to a wide dispersion high in frequency till a very narrow vertical directivity in parts of the frequency. This is something I believe is very beneficial as vertical reflections from ceiling and floor are only detrimental.

But the narrowing vertically means that you basically have to sit to get a good treble and higher mid response. If you stand up, the higher frequencies will be partially lost because it’s outside the listening window. This gets better further away from the speaker.

So the horizontal directivity is constant from about 200 Hz area till 5 KHz and narrows above. Vertically, we’re going to need to do 100% anechoic measurements to be certain. But the trait is that the dispersion narrows some above 400-500 Hz area, remains much the same till 1.5 KHz and narrows again above this frequency.

 

[Bjorn]

What’s important in directivity?

Let’s look at the directivity some more. The directivity of the Coherence 12 is somewhat unusual. We have seen speakers with a uniform horizontal directivity above about 1 KHz has scored high on spinorama tests. In my opinion, it’s more important to remain the directivity down to the Schroeder frequency vs remaining it very high in frequency. Especially when the directivity is initially wide (180°). The room contributes less to the highest frequencies anyway and we are general less sensitive to as well. The most important frequency range for speech and also many instruments has tradionally been between 500 Hz and 5-6 KHz. And that’s covered with a constant horizontal dispersion with the Coherence 12 and it also goes lower.

Another important matter is how the speaker interacts vertically. In a Danish study, they found the “floor bounce” the most important factor and the ceiling reflection the second most audible. The first floor bounce is right in the fundamental area, lower midrange and upper bass. If the level is low here, the speaker will sound lean and the frequency area above will dominate the tonality with sounding brighter. This is actually how most speakers measure when placed in a room, unless one is lucky and get peaks in the same range. This again leads to listening fatigue kicking in much earlier, especially with poor recordings.

The Coherence 12 completely avoids the first floor bounce and also greatly minimized both reflections from ceiling and floor above Schroeder. Combined with a horizontal dispersion that is kept constant to approximately 200 Hz, it will end up measuring more even when placed in the rooms compared to most other speakers. Also those speakers that score very high on a spinorama.

So as a mentioned in an early post: What good does it do if a speaker measures well anechoic but doesn’t measure that well when placed in an actual living room? This is also why we don’t put much emphasize on spinorama. We could have designed a speaker that would score higher, but that wouldn’t measure that well in an actual room.

 

[Bjorn]

Diffraction

Cabinet diffraction is often overlooked in speaker designs. It’s common to see very expensive speakers with no or little focus to minimize it. Diffraction happens when sound travels the surface of the cabinet and meet edges. Any edge will cause a comb filtering and a peak/cancellation in the response. It’s well documented.

In acoustics, the most detrimental reflections are those that arrive the earliest after the direct signal. Cabinet diffraction happens even earlier and is therefore something that’s important to avoid.

The cabinet of the Coherence 12 is super elliptical. Acoustically this is very close to a sphere, which is the best type of cabinet to avoid diffraction. The result, and as we will see later a response that is extremely free of ripples in the response. This leads to a sound that is more open and subjectivily more “airy” or “free” and the sound is also smoother.

 

[Bjorn]

Cabinet

When you have a large cabinet like here, bracing is crucial to avoid audible resonances. The cabinet has been very well braced. Cabinet material is thick MDF.

Dampening material has also been emphasized a lot. Many materials and different thicknesses have been tested. We’re not simply using common cotton stuffing here.

The base is made out of plywood with aluminum underneath for strengthening. And custom Sorbothane rubber feet are tailored to the weight of the speaker.