Project Bacchus

Introduction

Have you ever been in wonder of what music is? The fact that we as a species can convey story and emotion through a combination of simple tones and rhythms. For when you get down to it, that is exactly what music is, emotion. Sadly though, this is the one main thing missing in most speaker systems, the ability to convey emotion. A speaker that has a flat frequency response or a short impulse is fine and dandy, but when they can’t convey the emotion of the music you are listening to, they are down right useless.

That is why I designed “Project Bacchus”, I have always had an extreme connection with the music around me, and to not only own but to create with my hands a speaker system that enables me to connect with music on an emotional level, that is one of life’s necessities, because what is the point of being in a world full of music when you can’t connect with it?

Design Basics

For the design of “Project Bacchus” I took a lot of inspiration from speaker designers such as Richard Vandersteen and Jim Thiel who preach the gospel of time and phase coherence. Which is when you arrange the acoustical centers of your drivers in the vertical space so that they align in not only time but also phase, which is very difficult to do but when done correctly can be very rewarding.

Design Choices

One of the best ways to give speakers life, is to make sure that they produce a large sound stage. I went about trying to open the stage by doing three things:

1.) 3-Way

I chose to produce a three way system so that all of the frequencies in the spectrum are recreated without struggle. Too many times I see two way systems with large woofers. In order to use a tweeter effectively, it has to cross over around a minimum of 1kHz, so that means the woofer is also producing up to 1kHz, and depending on the crossover order sometimes even three to four octaves above that, which means up to 8kHz! and a woofer any bigger than 2″ can not accurately produce that high of a frequency.

To alleviate this I used three drivers, each of which only producing frequencies which it is comfortable and effective at. This means a 10″ subwoofer which gets crossed over at 200Hz, a 5.5″ woofer which gets crossed over at 2kHz, and a tweeter which is also crossed over at 2kHz.

2.) Stereo Subwoofers

Another design choice I made to try and help widen the sound stage a bit was to have a dedicated subwoofer on both the left and right channel. Because even though low frequencies are mostly omni-directional, the human ears can still distinguish between sources, and having both sources there really helps widen and smooth out the stereo field.

3.) Minimal Baffles

With project Bacchus, I really wanted to open up the sound stage to maximize the listening experience. To do this I committed to having the smallest baffle sizes possible, this will eliminate one of the main reasons why some speakers tend to sound constrained from left to right. To minimize the baffle size, I mounted the tweeter without a box, and I mounted the midrange in a tube which is only a total of half an inch larger in diameter than the driver it houses.

Subwoofer Design

The things which I really enjoy in a subwoofer are tightness and accuracy. Every time I have been really impressed with a subwoofer it has had those two characteristics, the support of the lowest octave isn’t that high on my priority list. To achieve this, I ended up putting my subwoofer in a sealed box, this gave the benefits of transient accuracy, and tightness which I really appreciate in a low end driver.

Woofer Design Choices

Boxes are boring, there are too many boxes out there in the world, and there are too many boxes in my design portfolio. So I decided to go with something I have never even wrapped my head around until this year, and that is a transmission line. For this concept I’ve taken a lot of inspiration from B&W speakers, where their enclousure behind their drivers gradually tappers down to nothing. The thought process behind this is to take all of the energy radiating of the rear of the driver and take it as far away as you can, the hope being that it never returns to the driver to cause distortion and cancelation.

Since I don’t have plastic injection molding machines and my ready (hopefully someday right next to my CNC routing table), I had to improvise. After many hours at the hardware store looking over my options, I picked one, a furnace vent. This vent allows me to get an approximately two foot long tube filled with sound absorption material behind my woofer, which very effectively takes the sound and has it never return.

As a side note: I don’t know if it is me trying to hear it or if it is actually there, but I think that I can hear the tube, but it isn’t on all songs which is weird.

Tweeter Design

I knew from the beginning that I wanted to use a ribbon tweeter, I have never heard a system which utilized them which I haven’t enjoyed. I also knew that to maximize the horizontal dispersion and high-end sparkle which ribbon tweeters are known for, I wanted to minimize the size of the baffle.

End Notes

I REALLY like my speakers, but they are not for everyone. In fact, I think I might have tailored them too much to my specific wants. I very much like mellow sound, even when I mix I try to get a super mellow sounding mix. So I wanted to make listening speakers that suited my tastes, and I really succeeded. When I put on a well recorded jazz ballad, these things sing, and I can feel myself being sucked into the music. But when I put on a pop/punk song on (I don’t know when I would, but we will speak in hypotheticals),  my speakers really tend to suck the energy out of the song, which could be very bad for a lot of people.

One of the aspects of my speakers which I like the best, is how far they sit back in the room. They sound like they are coming from almost ten feet behind where they are standing, which really helps them to blend in to the room, which is one of the key aspects of good listening speakers.

They are also very smooth, it is not the stereotypical “accurate” sound (like dead studio mixing speakers), but instead they just sound like everything flows together, I feel like my speakers really blend voices well within the mix.

Files

Design Statement

Design Proposal_Tim DeYoung

Enclousure Drafting

Drafting Plans_Tim DeYoung

Crossover Schematic

Crossover Schematic_Tim DeYoung

Final Testing Report

Testing Report_Tim DeYoung

Testing Results

Frequency Response

Reverse Polarity

Horizontal off Axis

Left/Right Difference

Step Response

Impulse Response

Waterfall

Minimum Phase

Harmonic Distortion @ 96dB SPL

Crossover Response

Tweeter Measurements

Frequency Response

Horizontal Response

Vertical Response

Step Response

Impulse Response

Phase

Midrange Measuremets

Frequency Response

Horizontal Response

Vertical Response

Step Response

Impulse Response

Phase

Subwoofer Measurements

Frequency Response

Horizontal Response

Vertical Response

Step Response

Impulse Response

Phase

If you have any questions, feel free to e-mail me: tsdeyoun@mtu.edu



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