The Q113 Revolution is designed to be a fresh new take on the compact Hi-Fi speaker. That's why it pushes the envelope and embraces some challenging solutions. There's no doubt that this is the restless boy of the class, making experienced engineers admit that their knowledge doesn't quite reach the finish line.
Passive devices. They have no magnet, no motor system and they are not powered because they are driven by the pressure changes that the active woofer creates in the air mass inside the cabinet. The aim is deeper bass.
It's fun to look back at the reasons why the Q113 Revolution has landed where it has. In the beginning, it was conceived as a speaker that would dare to go different ways than the usual ones. Not necessarily because there's anything wrong with good, tried and tested solutions. Not at all. After all, they prove their survival and relevance simply by existing. It is also exciting to seek new knowledge, but what can be the source of new resources? Speaker Q113 itself is an example of this.
Part of the revolution is right here!
A large part of the reason why the Q113 Revolution has reached its current level of development is right in front of you. The Internet and, in particular, the readers and engineers of ing.dk. It is, in all modesty, a form of revolution that the conversation taking place here can help shape a product, and at the same time send us all forward with new experiences and ideas in our wake. Listen to how we got here.
It started as a regular compact speaker
So a compact speaker, for which I had found a quite unusual 15 cm woofer from Scan Speak. It was a constructive talk, with many nuggets. The expectation was that the unusual woofer would sit in an 8-10 litre cabinet, because that was the intention of the project, but already after a blog post competent readers pointed out that this was probably not possible.
Calculations drove the project into the ditch .... the first time
The project therefore took a round about the calculation of base reflector cabinets, where engaged readers could make their own calculations and report on their observations. It then became clear that the Q113 Revolution could not be realised as a small bass reflex speaker, because the internal port itself would be far too long for the system to work. So long, in fact, that there would be no room for it in an 8-10 litre cabinet! So the project was officially in the ditch.
Sample cabinets. Finish and design are not important at this stage, when the lifetime of sample cabinets may be short.
Back on the horse with passive devices
Now, fortunately, a loudspeaker does not have to be designed according to the bass reflex principle, just because most other loudspeakers are. I explained that with some relief in this post. In fact, it's become more common to use passive devices when you want deep bass out of a small speaker. It is in active subwoofers that you see this development, but at the time I didn't see it as much of a challenge. I was more concerned about the project as a whole.
Functionality in the woods
A small speaker with three woofers - two of them passive - gave me a few sleepless nights, because it honestly seemed a bit crazy to imagine what the speaker would look like in the real world. It has already amazed me that some people would buy small speakers and put them in the bookcase where they sound bad. It fuelled the idea of going in a different direction. The compact HiFi speaker sounds best placed on a stand, but why not buy a floorstanding speaker? Or how about hanging the speaker on the wall at ear height? In addition, a speaker called "Revolution" is almost bound to represent an alternative to the ordinary, one way or another. And a solution was even needed with the placement of the passive units. A helpful engineer helped with some illustrations and we voted whether the Q113 Revolution should be a wall speaker or a floor speaker.
The headache continued unfortunately
Quite surprisingly, the wall speaker won the vote and the Q113 Revolution has since been further developed as a wall speaker, albeit with a parallel Plan B. The surprising thing about the voting is that there are no real high-end wall speakers on the market. Why did readers vote the way they did? Is it because the audio industry forgot to ask consumers which speakers they would like? Or is it not possible to create really good sound from a wall speaker? No one has been able to answer that question, which is why I've decided to develop a Q113 Revolution floorstander in parallel with the wall speaker, just in case it ends up in the ditch for good.
Test cabinets built. A helpful and enthusiastic reader has built test cabinets for the Q113, so that some real measurements can be made soon.
Here the engineers' knowledge is released
The passive principle is chosen because we have to and want to challenge the conventions. Relatively deep bass response from a small cabinet is related to the use of passive diaphragms, because there is no room for a bass reflex tube. That's how it is, but that's also where the engineers' knowledge gets lost. On the computer we can simulate the bass speaker's response in the cabinet. We can simulate its diaphragm excursion at low frequencies and then insert a virtual passive diaphragm, but a given weight, area, compliance and mechanical Q, all of which extend the speaker's capability into the deep bass, and we can get some accurate specifications out of it. We can give those specs to Scan Speak and ask them to build some passive speaker units for us. The challenge is to build a passive unit with the mechanical Q that we demand. You can't do that, off the top of your head! Weight, area and compliance can be described, but the all-important mechanical Q, which describes the passive diaphragm's willingness to stop at the end of a swing, is something Scan Speak can't just pull off a shelf. We simply have to try.
Engineers have integrated woofer and cabinet principle
The engineers have tailored the woofer to take as much load as possible off the two passive units. The deeper the frequencies the speaker has to reproduce, the more work is done by the two passive units. In fact, you could say that the woofer, the cabinet air mass and the two passive units form a symbiotic relationship, each designed for the other. We have chosen to use two passive units to ensure that the diaphragms move within their most loss-free range, which is obviously an advantage, but it opens up another challenge. Namely, we don't know how efficiently the woofer will drive the two passive units.
Placement of passive devices. The two passive units should be located at the top and near the bottom of the enclosure respectively. See arrows.
Where are the passive units best placed?
Frankly, we're not sure. It's almost clear that the two passive units need to be in close proximity to the woofer that will drive them. So far, so good. From there, you could argue that a passive unit could sit on either side of the cabinet. That might be a good idea, but it introduces unfortunate extra depth on a wall speaker that has to try to be flat, so I'd pass on that option for now. Also, you might risk midrange radiating from the back of the bass cone and out through the passive cones, but that's not known. The passive units would undoubtedly sit well on the back of the cabinet, with no disadvantages other than that this is where the wall should be. That leaves the front of the speaker as the most reasonable place to put the passive units.
Here, however, there are at least three challenges:
1. The bass speaker should not sit right in the middle of the cabinet on the high end, because that risks causing unsolvable problems with standing waves inside the cabinet.
2. The two passive units should (probably) sit at the same distance from the woofer, to be driven in the same way by the pressure changes of the air inside the cabinet. No one knows for sure.
3. The tweeter must sit close to the woofer for the sake of coherence in the sound image, so a passive unit cannot sit here as well.
These kinds of uncertainties probably keep most people far away from building such a speaker and I must admit that I have rarely heard experienced engineers admit that they don't feel at home in the stuff. We've simulated all sorts of complicated conditions using the industry's best software, but here the equipment simply gives up. That's all we can learn.
Knowledge from all directions
Speaker Q113 Revolution is so far the story of an ambition that has been pushed and prodded in a crazy jumble of personalities, skills, opinions, hard facts, unpredictability and helpfulness. That's why it's here. Out on an edge where there's nothing really to count on anymore. Some measurements need to be taken on a real speaker before we can reorient ourselves. It's really exciting.
