Tips for beginners in loudspeaker development (Version of 13.03.2003)

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Since my homepage in online I've got many requests of people who have never build a loudspeaker system their own. Many of them directly want to design their personal loudspeaker and ask for my support.

For many people the reason for DIY is the perception that they can save money by DIY. This is only partly true because you need to spend a lot of spare time. To come to the point very quickly:

If you are not willing to spend a lot of your spare time then loudspeaker DIY is not the right thing for you.

According to my opinion there a 3 rational main reasons for loudspeaker DIY or 3 different groups of interested persons, respectively:

  1. The do-it-yourselfer/designer:
    Despite a huge offer of assembled loudspeakers he doesn't find the "right" thing. This often concerns the size (e.g. must fit into a gap), the outer shape (he hates "boxes") or the appearance (e.g. colour, type of wood) of the loudspeakers. For the DIY/designer the integration of the speakers into the home is essential, technical aspects are less important.
    This group just needs a good suggestion (loudspeaker + network + drawings) and a bit of background information in order to allow little modifications that don't deteriorate the performance.

  2. The sound maniac:
    He just don't find the loudspeaker that sounds "right" for him or he cannot afford his dream speakers. Often the outer appearance is less important, only the acoustic performance matters.
    These guys need a warning: even DIY loudspeakers can't do magic! In order to be able to design the desired sound you must be intensively engaged in this theme, incl. basic theory, a bit of measuring technique and a lot of try out.

  3. The technique freak:
    He wants to dive deep into subject. He wants to know how loudspeakers work in detail. This group is the most grateful one, because it has the "right" prerequisite for successfully building a DIY loudspeaker::
This is just a rough classification and different combinations are possible. Although each group needs a specific support they all should follow some general advice:
  1. For the first project I urgently recommend to build a proposed project slavishly . This can be a project of: Only slight modifications either on the dimensions of the enclosure (max. 10% per dimension as long as the toal volume is kept constant) or on the used type of wood (chipboard instead of MDF, possibly 3mm thicker) are allowed. If "bigger" deviations from the original concept are desired some theoretical background will be needed (e.g. studying the book of W. J. Tenbusch Grundlagen der Lautsprecher).

  2. The selected concept should be adapted to the desired performance: In all cases I mentioned inexpensive examples which are ideally suited as a base for modifications.

  3. When you have selected a concept that fulfils your needs it needs to be build. Especially when welding the network you need to proceed very carefully. Errors may not only kill your amplifier (short circuit) but also damage tweeters and squakers if they are not protected from low frequencies as planed. Ideally you first measure the DC resistance at the connections of the fully wired box with a multimeter in order to ensure that no short circuit has occurred (you should measure at least the DC resistance of the bass loudspeaker). Then you should apply a noise signal with low level to the box but connect only one loudspeaker chassis at a time to the appropriate outlet of the network. This is to ensure that really a limitation of low and/or high frequencies occurs. Only then everything is assembled and you can acoustically evaluate your own loudspeaker for the first time.

  4. After the first enjoyment that the new loudspeakers work you will ask the question: was it worth all the labour, do they sound better than the old ones? Even if you as a do-it-yourselfer are only too willing to believe that your own work sounds better than anything else the critically DIY will ask himself very soon whether this sounding different is really better? And this is just the beginning because then you will realise your judgement depends on:

  5. At this moment the DIY are separated:

The evaluation criteria

First of all it must be determined, which piece of music is "well" recorded (from a technical point of view) and how it is reproduced on a "recognised good sounding equipment" in a "favourably shaped room".
This alone is a very lengthy process. Of course also the individual musical taste and the tonal preferences play a part in this, because not everybody listens to music in the same way: some prefer a rich, warm sound others like brilliant high frequencies or a clear midrange. For some people the dynamic aspects of music reproduction or the "timing" are more important and so forth. Therefore it is necessary to build up a collection of - technically - "well recorded" tracks which cover the critical concerns of your personal music taste and way of listening. As an example the human ear is very sensitive to differences concerning the reproduction of human voices as we are trained on this for our whole life.
By restricting yourself on this selection you are able to give a valid judgement on a reproduction chain very quickly. However this judgement cannot cover all aspects. A detailed discussion of this subject can be found on the page Limitations of music recordings.

Currently I use the following pieces of music to judge the quality of a reproduction system (I mainly look for sound balance and prefer a rich, warm sound):

No Artist Title CD Year What to take care of
1 Bobby McFerrin Blackbird The Voice 1984 Plausible voice and noises (e.g. breathing, claps)
2 Jefferey Smith Eleanor Rigby A Little Sweeter 1997 Very rich voice, muffled piano in background
3 The King's Singers Back In The U.S.S.R. The Beatles Collection 1986 Vocal bass not too dominant, discrete contributions easy to localise
4 Vocaleros Superstition Vocaleros 1997 Really funky, it must be easy to localise each contribution
5 Brent Lewis Mumbo Jumbo Pulse . . . Where The Rhythm Begins 1995 Very wide spatial reproduction, easy to localise
6 Talking Horns Johann, der Tango kommt Fisch im Wasser * Recorded with 2 micros only
7 The Oscar Peterson Trio You Look Good To Me We Get Requests 1965 Rich walking bass
8 Oscar Peterson Dream Of You Reunion Blues 1972 Bass left and behind speaker base, sober percussions, VERY wide vibraphone (single tones must be followed easily, even across centere), muffled piano may not sound muddy
9 Melissa Walker I'm A Fool To Want You May I Feel 1997 Very spatial without much "pseudo" reverberation
10 Jennifer Warnes Somewhere, Somebody The Hunter 1992 Very wide virtual stage, both singers in centre (follow their spatial interaction)
11 Keb' Mo' Just Like You Just Like You 1996 Very earthy, is must be able to separate the (co-)singers
12 Holly Cole Jersey Girl Temptation 1995 Very fat bass, all instruments very proper, warm voice, slightly purred/grumbled
13 Mighty Sam McClain Too Proud Give It Up For Love 1993 Very crisp cymbals, even at loud sections not annoying (singer should not be mixed up)
14 Marla Glen Personal This Is Marla Glen 1993 Throaty, dark voice, shiny trumpets, sounds addictive
15 Hugh Massekela Stimela Hope * Loud sequences must have punch, realistic voice
16 Yello Tied Up Flag 1988 The masterpiece of the Swiss sound puzzlers. Must blow your brains!


Only when you have worked out these evaluation criteria it makes sense to think about modifications. Examples are:

Essential with these modifications is to manipulate only one loudspeaker and to keep the other as a reference (ensure in advance, that both "base conditions" are really identical). This allows to make before/after comparisons to judge the effectiveness of the modification. This is necessary as the acoustical memory of humans is pretty bad an lasts only for a few minutes.
However, these modifications require some basic theoretical knowledge of the respective field (e.g. FDN or enclosure design). This can be obtained by studying special literature or internet pages.
All in all this is a quite time consuming task. But this stage is necessary to design your own loudspeaker system successfully. That's why my slogan is:

Measurement technique

In general there as several development stages:

  1. Rough layout (which chassis are promising, how big is the enclosure etc.)
  2. Detail design (how to position the chassis on the enclosure, basic layout of FDN)
  3. Fine tuning (how the final FDN looks like)
While the first 2 steps can be done on a desk for the 3rd step the continuous listening, modifying, listening again, modifying and so on is required. This 3rd step in effect is a loop that is followed as long as the result is satisfying.

For this it is essential not to loose the "right" direction. Only if you have a reliable starting point the following optimisation can be successful. According to my opinion measuring technique can help to find this reliable starting point quickly thus speeding up the whole development process.

At least until today measuring technique cannot yet describe the hearing sensation in all details. This is why at the end the subjective impression is always more important than objective measurement results.

The answer to the question "measurement technique - yes or no" essentially depends on the costs. Who is really willing to spend 500 EUR on measurement equipment when a loudspeaker system for 300 EUR should be developed? Therefore the amateur wants inexpensive systems. Most available systems are based on a PC with (built-in) sound card. Although the sound cards and the cheap microphones are not ideal they are still good enough to find a reliable starting point for the further subjective optimisation as non ideal frequency responses (at least for the sound card) can often be compensated. More difficult are non linear frequency responses of microphones because individual calibration spectra are not feasible in the amateur price range below 100 EUR and errors are typically within +/- 3 dB.

Overview of very inexpensive measuring systems (arranged alphabetically):

Name Remark
AudioTester V2.0 Win 9X, 25 EUR, very powerful but not easy to use (stereo input required)
HobbyBox V3.0 Win 9X, old version 48 EUR, not easy to use
Praxis Win 9X, free limited version, also good for car HiFi
SB_OCT DOS, 20 EUR, good for room acoustics, proposal for measuring microphone
SpeakerWorkshop Win 9X, freeware, not easy to use
WaveTools Win 3X, freeware, not for room acoustics, data export via clipboard to EXCEL