In episode 7, I cover some cost effective methods I use to help control cabinet vibrations and midrange coloration. For cabinet vibrations, there are several methods you can use to help reduce them. Bracing strengthens the cabinet walls to keep the from flexing and vibrating. What you should focus on is making sure you break up large panel walls with a brace. Corner battens are not effective in doing this. You need to make sure the brace connects from the middle area of one wall to an opposite wall.
Constrained layer damping, or CLD, two functions in reducing vibrations. First, it adds mass to the cabinet walls, requiring more energy to be applied to the cabinet to make it vibrate. Second, it has a flexible layer that is applied to the stiff cabinet side, and a stiff layer, usually some type of aluminum, on the outside. The combinations of the three layers creates an environment that resists sheer forces that are created when the cabinet wall tries to flex from vibrations.
Acoustic absorption material comes in many forms. I tend to prefer the denim insulation type (I'm using Duck brand UltraTouch) because it has a high absorption coefficient over a wide range, is fairly cheap, and doesn't cause itching or irritation like fiberglass insulation can. A driver radiates sound from both sides of its cone. Absorption material is used in the cabinet to absorb the back wave of a driver so it doesn't interfer with the output in the forward direction. Without it, the rear wave can reflect off the wall behind the driver and come back through the cone with a delay, causing coloration of the output. In a ported cabinet, you don't want to use too much or you will actually reduce the output of the port, which uses the rear wave of the driver. I typically line most of the walls in my ported cabinet, making sure there is an unobstructed path to the port. In a sealed cabinet or midrange enclosure in a 3-way, I would heavily stuff the cabinet to reduce the rear wave as much as possible.
In this video, I cover two very important concepts in building speakers, baffle step and diffraction. This video is more on why it occurs and what you can do about it. In my next video, I'll cover how to model it using factory curves provided by the manufacturer.
FPGraphTracer is a free program that is designed to copy the frequency and impedance graphs published by manufacturers in their data sheets. In this episode, I show you how to use FPGraphTracer to turn manufacturers' published frequency and impedance files into a useable file type for crossover design. It is important to know that you should only use infinite baffle measurements when you are tracing. If a measurement has been conducted on a standard baffle from a speaker cabinet, the measurement can only be used for simulating speakers of the exact same baffle dimensions. The tweeter being used is the Dayton RS28A-4. It is a high value for the money aluminum dome tweeter with low distortion and the ability to be crossed over at very low frequencies. I'll be using this tweeter again when I demonstrate how to simulate baffle diffraction for your drivers, and the when I demo how to design a crossover. I will be doing this with the Vifa NE180W-08, so that you can follow along and work through the model. You can then compare your results to my modeled and measured results of a speaker using these drivers to see how accurate this method can be.
The last video in this series covers how to design a passive radiator enclosure. Passive radiators have some upsides and some downsides that you should be aware of should you decide to build a project with one. If you have tried playing around with many subwoofers and enclosure designs, you might have come across a few that had ridiculously long ports for a given box size, especially if you needed a large port area to keep from exceeding port velocity limits. A passive radiator will allow you to tune an enclosure lower without having to worry about port lengths that won't fit inside your box. They also don't suffer from vent velocity problems, i.e. port chuffing. In some instances, they can also prevent a compliant woofer from unloading below tuning and therefore can be used to control woofer excursion better than a port. On the downsides, actually less efficient than a properly sized port since there are mechanical losses through the suspension. They also are significantly more expensive. As with everything in audio, it becomes a series of trade-offs.
Once again, the software being used is the Jeff Bagby's Woofer Box and Circuit Designer Excel spreadsheet and the subwoofer being modeled is the same subwoofer used in my first three videos, the Dayton Audio RSS256HF-4.
Yes! You do need to model sealed enclosures, too! Sealed enclosures are much more forgiving, but it's still a good idea to model a sealed enclosure so you know how much power your driver can handle. Drivers with a high Qts or in an abnormally small box can also lead to peaking in the bass, which can make your design sound boomy.
The other important thing this lesson covers is how to model a sealed design with amplifier boost to extend the low end response of your subwoofer or woofer. Some plate amps, such as the Dayton Audio SPA500, have the ability to add boost in certain frequency ranges, and some have a built in preset boost, such as the Yung SD300-6. Using these correctly can result in a sealed design with bass extending down to 20 Hz flat, or if used incorrectly, could result in a big 6 dB peak above the nominal response.
Again, the software being used is the Jeff Bagby's Woofer Box and Circuit Designer Excel spreadsheet and the subwoofer being modeled is the same subwoofer used in my first two videos, the Dayton Audio RSS256HF-4.
Modeling is extremely important to make sure you get the response you want so that you have good bass instead of terrible bloated bass or anemic bass. This video demonstrates what kind of response you can end up with if you don't model your box. Ever hear a ported "one note wonder" subwoofer? This video will explain why and how to avoid ending up with one.
The program being used is Jeff Bagby's Woofer Box and Circuit Designer Excel spreadsheet and can be found here: The subwoofer being modeled is the same subwoofer used in my first video, the Dayton Audio RSS256HF-4. Again, it is a great subwoofer with low distortion and a very clean sound. I've used it in the bottom of a 3-way speaker and the 12" version as a subwoofer before and I love it! They are very hard to beat for the price.
In this video, I explain how to model a ported subwoofer enclosure using Jeff Bagby's Woofer Box and Circuit Designer, a free software and manufacturer's published T/S parameters. The whole process is much simpler than you might expect. My recommendation is to follow along with the video to learn how the software works and then play around with a bunch of of different woofers and box tunings to see how different parameters affect your response. The more you practice, the better a feel you'll get for the things you can do to alter the response.
The subwoofer I'm modeling is the Dayton Audio RSS265HF-4. I love this subwoofer! I've built a 3-way with it and a traditional subwoofer with the 12" version. It is very low distortion and clean sound and you definitely won't beat it for the price. Anything from the Dayton Audio Reference line is very good quality and definitely something to consider if you are building a DIY project.
Getting started in speaker design can be a daunting task. There is a lot of information out there on the subject, but not all of it is good information. You can find all kinds of various opinions about it across various forums and it's hard to know what info you should trust, and what you should ignore. I've created this website to try and help you distill solid and proven design principles from the loads of opinion and BS on the internet. With some patience and effort, you will probably find that it's not as scary as it seems to get started. In fact, once you learn a few basics, you can start designing basic and listenable speakers with essentially no financial investment outside of the drivers and crossover parts. If you want to take your designs to the next level, you'll need to get some measurement equipment to help you along the way, but it is much cheaper than most people expect. A basic setup can be had for less than $100, which will provide most of what you would ever need in terms of measurement ability. If this appeals to you, then stick around. This page will have both video and written tutorials to help get you started.