Banana speakers 2022

The speaker cabinet design is not mine. A running buddy of mine had the cabinets without speakers in his garage for 20 years. He had seen this design once and had it copied by a carpenter. It takes real craftsmanship to make this shape! Because the walls of the cabinet are never parallel, it will be difficult for resonance to occur in the cabinet. That's a big advantage. He asked me to install speakers in it.

Coincidentally, the broadband Tymphany ring radiator tweeter turned out to fit exactly in the existing tweeter hole. For the woofer I found the very nice Dayton RS225-4 8" Reference Woofer, also fitting exactly. First of all, the inner walls were reinforced with partitions.

The design of the electronics, including PCB, is mine. An active amplifier is built in. That is to say, a balanced input amplifier, an electronic 18 db/oct crossover at 800 Hz, two separate power amplifiers, an active bass correction filter (the cabinet does not have a bass reflex port) so that the woofer goes straight down to 20 Hz and a circuit (“audio switch”) that automatically takes the amplifier out of standby when music is presented. The power indication LED (green/red, power/standby) shines on the floor by chance and that gives an unexpected nice effect.

The result is a uniquely shaped loudspeaker with high-end sound characteristics.

Mini loudspeaker 2020.
A small (30x12x12cm) but high quality loudspeaker with built-in amplifiers. So it can be connected to a media streamer directly without the need of a preamplifier.
It is completely constructed from laser-cut acrylate. It contains the Monacor SPH-100C 4" woofer in a completely closed cabinet and the Tymphany XT25TG30-04 wideband ring radiator tweeter. Electronic crossover is at 750 Hz. The low frequencies are boosted with 12 db/oct resulting in a very deep but bass, down to 30 Hz. 

Of course, they can not match the large array speakers. But the challenge here was to built a very small, good looking but still good loudspeaker.

Frequency response measured at 3m in a living room:

 Documentation coming soo.

Model 2018. A line array speaker with built-in amplifiers.
The challenge here was to make a system as good model 2017 but a little bit smaller
and much easier to build.
And very important, I wanted to use acrylate in order to make a modern design.
But the fabric cover of model 2017 is still a good option too.

The listening room is an important factor for listening to music.
The music reaches your ears via reflections of the ceiling, floor and walls
to a large extend. An acoustic ceiling and carpets would help a lot but are often
difficult to realize. By using array loudspeakers, which bundle sound in a vertical way, the effect of reflections from ceiling and floor is reduced.

Dimensions: 120 x 26 x 11 cm

Documentation can be found here.

 DFX drawings acrylic panels:

• AmplifierPanels.dxf
• BlackAcrylicPanels.dxf
• RedAcrylicPanels.dxf

What design choices are behind model 2018?

The design of the standard loudspeaker sold in stores differs in at least four respects. The standard speaker is usually a two-way or three-way system with a bass reflex port and no amplifiers are built in. This model is a two-way system in which the mid and high frequencies are reproduced by nine broadband speakers in an open box and a bass speaker in a completely closed box. Amplifiers with filters are built into the cabinet. The cabinet has been kept as flat and narrow as possible to be placed in the living room.

Each of the following four features contribute to quality enhancement:

Open baffle for broadband speakers

When a speaker is enclosed in a cabinet, resonances of the air in the cabinet will occur. Those resonances gradually disappear through the speaker and cabinet panels. This seriously 'colors' the sound image. The cabinet continuously stores sound energy that is released in a delayed manner. However, a closed box is not necessary for mid and high tones. That is why the broadband speakers are mounted in an open cabinet. This results in an uncolored sound. Voices sound more natural. For this reason, electrostatic speakers also sound so good because they are never mounted in a closed cabinet.

Line array

A line array system consists of a column of identical loudspeakers. This system is used in large spaces (e.g. concert halls, churches) due to its high efficiency. The efficiency is due to the vertical bundling of the sound. For a living room, efficiency is not important, but vertical bundling is. This ensures that less sound reaches the listener through reflection from the floor and ceiling. To the listener, it seems as if he is closer to the speaker. Almost as if he is listening through headphones.

Completely closed bass cabinet

An open cabinet for the bass is impractical because it would require a very large panel. With standard loudspeaker systems, a bass reflex port is needed to get more lower frequencies. However, the bass reflex port is based on resonance. And at resonance, sound energy is released in a delayed manner. For this reason, a closed cabinet was chosen. The cabinet is so small that standing waves (resonance) cannot arise. To compensate for the lack of bass, which a small box entails, correction amplifiers are built in. In this way, the bass sounds quieter than a bass reflex system.

Built-in amplifiers

There are a number of reasons why amps are built in. As mentioned before, correction amplifiers are needed for the low end. The treble is also slightly corrected. In addition, there is an electronic crossover filter. This is more accurate than a passive filter as used in standard loudspeaker systems. Separate power amplifiers (LM3886T) are built in for the low and high frequencies. This means that the speaker is directly connected to the amplifier, without the intervention of cables, coils, capacitors and resistors. In that way, the speaker is better controlled by the amplifier.

There is a circuit  ("audio switch") that automatically turns on the power of the amplifiers when the music starts. When the music has stopped, the power will be turned off after a few minutes.

The "active" speaker can be directly connected to a preamplifier or media player. The loudspeaker can be connected to an existing power amplifier via a resistance attenuator (1:20).

Model 2017. A speaker with built-in amplifiers.
In order to match an electrostatic loudspeaker, it is essential to use an open baffle. 
For a high quality bass a fully closed design (no bass reflex port) should be used.

I still remember hearing this system for the first time. What a surprise!
The overall performance is slightly better than the electrostatic model 2009.
Although the high frequencies of electrostatic speakers seem unbeatable.
I am also very glad with the loudspeaker fabric cover. That makes the speaker
more acceptable in a living room.
The construction was very time consuming. I will not built this one a second time.

Dimensions: 128 x 30. Depths: 8 and 20 cm

Documentation can be found here.

Measured in living room at 3 m distance:

Model 2007. A three-way active speaker.
The goal was to make a good sounding system in a very small cabinet.
The last goal failed! The idea was to make the cabinet for the woofer
and mid-speaker very small in order to prevent cabinet resonances.
A good alternative for open baffle systems to get a colorless sound.
It has two electronic crossovers, bass compensation for the small
cabinet and three power amplifiers.

 Dimensions: 60 x 22.5. Depth: 26.5 cm

Measured in living room at 3 m distance:

Model 2009. A speaker with built-in amplifiers.
A co-project with Alfred Homsma.
This is a fully open system. Is has an electrostatic
panel for frequencies from 400 Hz.
Two large woofers in an open baffle, electronically
compensated for acoustic short circuit, give a very relaxed bass.

I have a set of empty cabinets in the garage I want to get rid off.
If you are interested please let me know. 
Instead of the ESL, you could use an array of FR-58 speakers. 

When I was about 17 years old, I heard the Quad ESL 57 for the first time and from that time on I was fascinated by electrostatic speakers.

I can recommend a visit to:

• https://www.solostatic.com/
• https://elektrostatenservice.nl/

Model 1990. A passive three-way speaker.
The mid speakers are mounted in an open baffle.
The woofer is in a fully closed cabinet, so it doesn't
go very low. Due to the four mid speakers in a line
array and open baffle, voices sound very natural.

I probably build another 8 speakers before this model.
Unfortunately I don't have pictures of them.