Ole Witthøft

Basbøvl. The fate of the speaker builder

There's no beating about the bush when the world's loudspeaker builders make the almost irrevocable decision about how a loudspeaker's bass response should be. This of course also applies to the Q113 loudspeaker.

The image is not shaky, it's the woofer working (a lot). The diaphragm diameter is only 15 cm, but its long stroke length means that the little speaker can still move quite a lot of air. The "price" is the speaker's efficiency, which remains relatively low.
The first serious decision in Speaker Q113 must be made soon. It is about what technical and sound characteristics the bass system should have. After all, you can't have everything you want. The problem is that the loudspeaker builder has to prioritise between three characteristics that any music lover would love to revel in unrestrictedly and unhindered, but we have to make a choice on the music lover's behalf. I repeat: all loudspeakers based on dynamic loudspeaker devices have met this crossroads at some point during their genesis. In the Q113, I think we have to meet the crossroads first.


Technology cause of congestion

It is the basic construction of the dynamic loudspeaker, i.e. membrane, magnet, voice coil, that is the cause of the challenges for the loudspeaker builder. Add to this the fact that there is a forest of acoustic principles to which the cabinet can be built. This almost infinite variety of possibilities explains the incredible difference between all loudspeakers and their sound. It is a source of great fascination. There are so many things you can adjust, so many jaws you can tap, that the speaker becomes more than just a piece of engineering. You can't help liking speakers once you get to know them. Just listen to how many balls are in the air when a speaker plays the bass tones of music.


How the speaker makes bass

For the speaker to reproduce bass, there must be a membrane that can move the air. The diaphragm has an area, a weight and a compliance. It is driven by a voice coil that has some electromagnetic properties and it sits in a magnetic field that has a certain strength. The diaphragm of the bass loudspeaker is housed in an enclosure with an air mass that has a compliance that depends on the volume of the air mass and the damping material inside the enclosure. If the speaker is a bass reflex design, there will be a tube in the cabinet with a very specific air mass. Much of the bass response comes out of that tube, but the entire bass response occurs as an interaction of all the things I've just mentioned. In fact, the position of the speakers and the acoustics in your room have just as much - or even more - influence on the bass you hear, but that's another story. In case you're confused, it's simplified now.



There is no way around it. The loudspeaker builder must choose which features to pay most attention to. And which ones must live more in the shadows.


A priority between three properties

In any design, a loudspeaker builder has made a priority between the loudspeaker's efficiency, its bass characteristics and its step response. The three things are interrelated, like a layer cake that needs to be divided into three pieces. If you make a big effort towards one of the characteristics, you lose the opportunity to do the same for the other two, and so on. The properties should be understood as follows: Deep base properties. The ability to reproduce as deep notes as possible. Efficiency. The ability to convert the amplifier signal into sound. Step response. The ability to remain silent when the signal has stopped. All three characteristics are good. Deep bass helps give the speaker soundstage size and power. We want plenty of that. Efficiency is related to the speaker's requirements for the amplifier's output power. The very idea that a speaker converts most of the amplifier's power into heat, not sound, can make anyone vote for better efficiency. A good step response helps make the sound accurate so it doesn't sound like the bass player is stumbling behind the rest of the orchestra, so a good step response is important for the whole flow of the music. But as a speaker builder, you have to prioritize.


Examples from the edge of the real world

A small speaker can play deeper bass than a large speaker. It can if you trade efficiency for deep bass characteristics, for example by using a heavy diaphragm. I'm not saying this happens every day. I'm just saying: it can be done. A great speaker can be capable of playing loud without being particularly good at playing bass. It can if it has damn good efficiency and a good step response. Then you can make a big speaker that can play really loud and with very accurate sound, but the bass response is similar to that of a small speaker. Typically, it's the big speaker that both plays the deepest bass and is the most efficient. The small speaker has, more often than not, the best step response. But a loudspeaker can be designed with some extreme features that change these relationships. I think that should be included.


How I want to prioritise for Speaker Q113

Comments are welcome, but as a starting point I think it makes sense to think as follows. Efficiency we can do without, if only the Q113 can be made to withstand enough power. Good amp-watts don't cost that much, don't really take up any space and it must be OK in the good cause to expect that the Q113 will be used with a relatively powerful and good amp. We also turn down the bass characteristics a little, or put another way: The Q113 doesn't need to go down to 30 Hz, although we could make it do so. On the other hand, the bass response of the SA2K was judged to be the speaker's weakest point by the 37 test participants at the Open House event, so the Q113 should do the job better than the SA2K. That's clear. The speaker's step response I'll try to keep a special eye on, because once you chill the sound's precision away, there's nowhere to find it again. More elaboration later.


I hope you're thinking that right now.

If you're reading this because you think it's funny, I hope the post shows that a speaker is not just a speaker, and that there are attitudes behind every design. Should you be a seasoned speaker builder, you might ask: "Wasn't there something about two Australians accomplishing something important for speaker builders back in the 70s?".
More about the two Australian pioneers next time.
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Ole Witthøft
Ole is the founder of System Audio. His 3 greatest passions are music, design and technology. Every day, Ole is working on some kind of projects, and you find him in the workshop, in the production, behind a computer or on one of his many presentations around the world.
Basbøvl. The fate of the speaker builder | SA

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