"modular"

"modular" - DSP based 3-printed DIY speaker system

This page is about DIY-speaker system I build and keep experimenting. I try to build the system so that I can exchange different parts of system easily, hence the name "modular".

I live in apartment building, and prefer to do critical music listening "close-field". So I don't need to play music loud and this naturally affects some of my design choices. For example I know I can make 3 way system working with 4.5 inch midwoofer in my use - that would be impossible in large well damped wood frame house with habits of playing loud.

Basic princibles of "modular"

DSP used as crossover, time alignment and equalization

I prefer active crossovers and directly connecting amplifiers to drivers. Naturally this requires 8 amplifier channels for 4-way stereo system, which will cause some extra cost. For me flexibility of being able to try different settings realtime without first buying crossover components and soldering is the most important reason for active crossover. In my opinion subwoofer and midbass sound much better when there is no 1ohm resistor in series with the bass driver, specially with good amplifiers with large damping factor.

System must work for nearfield and in general use

I prefer to listen music nearfield, but watch television/movies from sofa which is about 2x distance compared to critical music listening spot. Sofa is also in back wall, and near field listening position more ideally 1/3 room length away. Mostly this can be easily achieved by setting delays and levels in DSP. Some combinations of tweeters and midranges in their enclosures will not produce room power response suitable for such different snenarios.

3-way or 4-way configuration

I want to experiment with different combinations, e.g. large midbass with very large waveguide on tweeter vs. small midrange and small waveguide on narrow enclosure or maybe go really wild and use bare tweeter without waveguide :) and naturally 4-way with more optimally sized drivers.

3D-printed midrange and tweeter enclosures with standard front panel

I expect most innovation and prototyping to happen with midrange and tweeter enclosures. I'm specially interested on designing different waveguides for tweeters to optimize directivity and power response in room.

In order to try different midranges with different tweeters, or different enclosures for either one I have chosen few common dimensions to be used, let's call this "v1" specification:
- front panel width 160mm with 18mm rounding in corners...
- ...at bottom of tweeter enclosure and top of midrange enclosure (otherwise free shape)
- Two M5 bolts sticking out from midrange enclosure: 55mm from centerline, 40mm from front panel

Most likely at some point I will also try B&W 802 kind of round midrange enclosure without actual front panel. That will not be "modular", but naturally I'll use the same subwoofer and midbass system.

Midbass cabinet/speaker stand

I'll use 800mm heigth and 200mm width midbass enclosures made from wood. They will either server as midbass or just as an speaker stand. When used as midbass they will either be midbass in 4-way system or midrange in 3-way system combined to large (max 200mm) waveguide for tweeter.

Separate 3D-printed panel is used for the driver, allowing multiple different drivers to be used. Enclosure volume can be adjusted to suit the driver. Midbass always in sealed enclosure, which if full of damping material.

Subwoofers integrated part of system

The "modular" system is never intended to work without subwoofer. I see no point designing 2-way speaker, which would need to work without subwoofers and any of my main speakers never would be good or even usable by themselves.

Subwoofers are in small sealed wood cabinets, there is many of them and they are distributed in room to minimize standing waves. Small sealed enclosures are easy to place to good locations, but don't go very low: in order to compensate Linkwithz-transformer is used and each driver has ~400w power available. Subwoofers are driven with 2 amplifier channels and delays can be set to compensate different distances.

Journey or destination?

Over the years I have had many speakers, but in the end I have always returned back to my DIY speakers I built on 1990s. I know I would be happy with pair of Genelec 1237A or Amphion Krypton 3, but I would never "invest" that much money for home audio.

Commercially sold 4-way system including Scanspeak Illuminator 7"+4"+tweeter (or similar Seas Excel parts) would cost >10000€. Drivers itself cost less than 2000€. Commercial speaker needs to be designed as a compromise to suit all usage scenarios and rooms. So there is also good change to reach very good "destination" with basic understanding of speaker design, physics relevant to speakers and willingness to learn and improve by building prototypes.

Goal of this project is naturally to get good speakers for music listening, but for me it's as important to study, learn, innovate, design and build different solutions. This project has failed if it becomes ready :)

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