LDSG sponsored by

Go to…. Preface The DIY Speakers mailing list Selecting a project Selecting a system and drivers Enclosure types, aesthetics, & gallery

Preface:

After an absence of a couple of decades, I got the urge to design and build some new speakers. Since my technical skills and knowledge of available components were both woefully out-of-date, I set myself a research project to refamiliarize myself with the resources currently available.

This document (hereafter referred to only as "the LDSG") is an attempt to share what I'm learning. As such, it will hopefully grow and increase in value as I progress. This is a living document - comments, additions, corrections, and even flames are welcome. Send them all to:

To be as useful as possible, I've included links to not only specific vendor sites, but also to specific data and pictures for individual drivers where available. In addition to the various vendors whose products are represented here, I've also included links to sites or graphics from a number of third parties. Among those who have provided graphic, measurement, and other data are:

• Audio-X-Stream (Rudi Blondia)


• Brian Steele


• Lambda Acoustics (Nicholas McKinney)


• Soundstage! Equipment Review Archives


• Steve Sedmak


• Nicholas Jensen


• Stryke Audio (John Janowitz)


• Raymond van Weeghel

Basic facts (business perspective):

No manufacturer is going to keep his doors open producing reasonably-priced drivers for the DIY market. Loudspeaker driver manufacturers stay in business by supplying divers for commercial loudspeaker systems manufacturers. Many of them also supply the DIY market - some actively, some only as a sideline.

High-end drivers are a slightly different matter. In many cases, there's insufficient market to keep prices within reason, so supplying DIY'ers not only helps amortize engineering costs, but also serves as an outlet for units which don't quite meet their systems clients' specs. It also serves as an R&D showcase which helps bring in more commercial business.

Basic facts (technical perspective):

Although there's still an aura of black art involved in the manufacture of speaker drivers, it's actually a reasonably mature technology. Almost anyone with the proper training can design and produce decent quality drivers in reasonable volume. As with any engineering discipline, some are better at it than others. Also, there are the usual tradeoffs between cost, performance, and tolerance.

Perhaps a non-obvious corollary of the preceding is obvious when you start looking at the drivers used in various commercial speaker systems. Some might expect to see a short list of vendors dominate their competition by virtue of their clearly superior technology, but this simply isn't the case. Some vendors are quite well represented in many highly-respected systems, but in many cases, the drivers used aren't even their highest-tech units. How is this so? Simply put, a well-designed crossover can correct a multitude of driver sins. It's often much more cost-effective for a speaker systems manufacturer to use a less expensive driver and apply subtle contouring and phase correction in the crossover design. The only critical feature of the drivers is their unit-to-unit consistency, which will allow mass-produced systems to all sound alike.

Why DIY?

Based on the preceding discussions, it's obvious that only DIY'ers (aside from the handful of cost-is-no-object vendors) have the luxury to select truly superior drivers since they needn't be concerned with the economics of mass producing something as costly and labor intensive as speaker enclosures.

Why not DIY?

Building a really good speaker system - one that compares favorably with audiophile commercial systems - is still not a cookbook process, book titles not withstanding. Even with all the parts and virtually identical woodwork, assembly technique and a good ear can be vitally important to the success of a DIY project. Even more important may be a good grounding in the theory of how and why the "cookbook" rules work as they do. Finally, if you're really serious about achieving a truly competitive system, you must be prepared to invest in some minimum level of instrumentation and CAD system. All this implies at least a few months of education time plus a few hundred dollars invested before you even get started.

A shameless plug for the DIY Speakers mailing list:

Many of the driver recommendations in the LDSG came from the DIY Speakers mailing list (nee "the Bass List"). In addition to the usual helpful discussions, DIY Speakers list members get discounts from many vendors. I therefore advise and recommend that if you're serious about DIY speaker design, you subscribe to the DIY Speakers mailing list! Using either web sites or email, there are several ways to subscribe. About the easiest way is to Link to the subscription/unsubscription form at:

Selecting a DIY project:

There's a temptation common to beginning DIY'ers to try to go from novice to dream system designer in one big step. Resist this temptation! Select a project that is a little more challenging (both technically and financially) than your current level of experience. Not all DIY projects turn out well. If your reach exceeds your grasp, you may find yourself with a pile of expensive components that sound terrible. Not only is this a bad investment of your time and money, it will also discourage you from trying again. As with any investment, the secret is to optimize the ratio of risk to potential gain.

A corollary of this principle is that, if you're a complete beginner, it might be a good idea to begin by building a kit or other predesigned system, then work your way up to a "from scratch" DIY design. In Section 15 of the LDSG, I list a number of available kits, what drivers they use, and their prices.

Selecting a system and drivers for DIY projects:

An integral part of any DIY project is selection of the drivers. If you're building a kit or working from a set of plans, in most cases this has already been done for you. Still, even in the case of a kit, many different drivers can fit into the same panel cutout and you may wish to select alternatives. If you're building from scratch, driver selection is a required part of the design process. Despite lots of agonizing by many DIY'ers, driver selection isn't rocket science.

1. First, consider the primary purpose of your speakers. Is your application for a home theater (HT) system, or for music? Must people will use theirs for both, so here are the basic guidelines you need to observe:
1. Home theater requires at least 6 speakers - two main (left and right front) speakers, a center (front) channel speakers, two rear channel speakers, and a subwoofer. Digital Dolby can require still more speakers. For HT systems, the recording engineers are in control of the sound field, so all 5 of the main and rear speakers should sound pretty much alike. Also, since there are so many of them, they should be as small and cost effective as possible. If you don't want to make all 5 alike, you should at least try to make the front 3 alike and the back 2 alike, both sets with a common "sound". The front 3 should also be magnetically shielded to avoid interference with the TV screen. All should have response down to around 80 Hz, where the subwoofer takes over. Since one of the things that contributes to the realism of HT is the bass, don't scrimp on the subwoofer!
2. Music systems are still mostly stereo. Although some movie sound tracks and audio discs offer multiple channels similar to HT, most of your attention should be paid to your front two speakers, since other channels are definitely optional. Whether to use full- range systems or a subwoofer is your choice. If you wish to use a subwoofer, you will either need an electronic crossover in the signal path, or one of the many available purpose built basic amplifiers designed to be mounted within the subwoofer enclosure. Some sources of such amplifiers include major distributors (e.g. Madisound, Parts Express, Meniscus) as well as specialty distributors (e.g. ACI, Burnett & Associates).
3. Combination systems have to balance the above requirements. To design such a system, you have to assess what percentage of the time your system will be used for HT, and what percentage of the time for music. As the numbers become very large on either side of 50%, you will need to make fewer and fewer compromises. Systems which will be used about 50% of the time for each application will require the greatest compromises. Such hybrid systems usually use two extremely high quality front speakers with a center channel speaker of the same "sound". The two front main speakers may be located far enough away from the TV screen to not necessarily require shielding, but the center channel speaker will still require shielding. Rear channel speakers in such a system, should share the same sound as the front channel speakers, but are otherwise less important. A subwoofer is recommended for such combination systems, although most HT receivers and amplifiers are configurable to allow you to eschew a separate subwoofer.

Note that in all of the preceding discussion, the term "sound" really refers to timbre matching. No matter how neutral, all speakers will still slightly add their own unique aural stamp to the sound they present. The easiest way to achieve timbre matching is to use either identical drivers, or similar drivers, preferably from the same manufacturers.

2. Choose a basic design. This will determine the number of drivers and their specific parameters. But just remember, the more drivers you use, the easier it is to mess things up. Two-way designs are the simplest and can sound amazingly good, given the use of appropriate drivers. Three-way designs require more care to properly match all the pieces. Four-way or higher-order designs get really complicated. Often, these will have crossovers in the middle of the critical musical range of 300-3,000 Hz, which makes driver matching much more critical.
3. Choose the type of enclosure for your low frequency (LF) driver. Note that the LF driver may be either a mid/bass, woofer, or subwoofer (these are discussed in detail in Section 2 below). In all this, you must remember "Hoffman's Iron Law", which states that bass extension, efficiency, and box size are all mutually exclusive - you can only increase one at the expense of the other two. If you want efficiency in a small box, you have to give up bass extension. Similarly, if you want bass extension and efficiency, you must live with a large box, etc.

   The purpose of the enclosure is to prevent the back wave which emanates from the rear of the driver from canceling out the front wave, since they're 180 degrees out of phase with one another. To that end, a number of types of enclosures have been devised. The most popular types discussed here are:

   Sealed ELFTM Aperiodic Ported/EBS Passive radiator Bandpass	Array Isobaric Transmission line Horn Terminated line Tapered quarter wave tube Dipole
   Enclosure aesthetics	Gallery of interesting designs

4. Select the best drivers you can afford which meet the parameters determined in step one above.
5. Verify that whatever anomalies are left over can be corrected in the design of the crossover - either active or passive, it makes no difference.

   This is the hardest step for DIY'ers. Before you can fix the anomalies, you first have to recognize and understand them. After that, you're still faced with having the tools (and the skill to use them) to realize the required fixes.

The remainder of the LDSG is a guide to vendors and technologies you can use in steps three and four above. Note that there is an inherent pitfall in this whole process - the myth that there is a "best" driver. It should be obvious to anyone paying attention that many fine speaker systems have been built with a variety of drivers from a variety of vendors utilizing a variety of technologies. What's "best" depends on objective factors (the system configuration and alignment plus the exact mix of drivers) as well as subjective factors (everyone's ear is a little different than everyone else's). For this reason, the LDSG only offers guidelines based on the collective experience of a number of different sources.

Following this introduction are twenty-two sections, each with subsections. Click the index button below to go to the master Index.

©1998-2007 by Bob Stout, all rights reserved

Tested with: .

Support: