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How to choose the right DIY project - for your ears
Copyright 2012-20 Troels Gravesen

SIZE     COST        BASS EXTENSION     EFFICIENCY


Summary:
Please do not ask what speakers to build.
Please do not ask the difference in sound from two speakers.
Please do not ask what amplifiers will suit a given speaker.

I often have the quest for describing the difference in sound from two speakers. The thing is that describing sound just doesn't make sense. I might write a book on both speakers and still you wouldn't have a clue to how they actually sound. Potent bass is no bass to some people, smooth midrange may be harsh to others and some may find balanced treble is no treble. Adding percentages to sound is ludicrous. Is this speaker 90% of that speaker? It doesn't make sense.
I know that magazines are filled with sound descriptions and still, you won't know what they sound like before you have heard it yourself. It's no different than describing the taste of wines: Subtle, Delicate, Elegant, Crisp, Thin, Finesse, Bright, Floral, notes of this, notes of that, etc. Rubbish! You won't know until you've tasted it yourself.
 
Your room is half the system! What kind of sound you get from a pair of speakers is highly dependent on the room, the size, where in that room you place the speakers, the amount of acoustic absorbent, etc. There's an infinite number of variables that have an impact on the sound you hear from your favorite seat. Even from a thorough description of your room I can't tell you how a given pair of speakers will perform in that room. Sorry, not possible.

I wish all speakers had front grills. Immediately when we see something our brain starts preparing our perception of what we hear. Many people hear with their eyes rather their ears. If something looks gorgeous it must sound good as well, and we may even start making excuses for that speaker if there is something may may not please our ears. I invite people to hear new speakers and one time I made a speaker with a grill, it caused confusion, because all of a sudden they had to listen without knowing what they were listening to. Some people may even find this uncomfortably because you have to rely on one sense alone, hearing.

Being a newbie in diy-loudspeakers, the #1 question obviously is this: What am I going to build? What will suit my needs, my system, my room, my wife, etc. HiFi magazines are full of mails posing the same problem, because we can't hear them all and in particular when we're dealing with DIY, it takes a lot of practice to "read" a project and get some ideas on how it will perform. Actually it may take many, many sheets of MDF and experience with a huge number of drivers. I could have bought a pair of extremely expensive speakers for the money I've invested in speaker drivers - but it wouldn't have been the same fun!
Those of us having made a large number of speakers will know the excitement of setting up our finished speakers and thinking this is the best thing since sliced bread. After a couple of months, post honeymoon, we may start thinking this really wasn't the stroke of genius we thought it was - and start planning for the next project.

If I had to help you picking the right speaker for you and your room, I would have to know you personally, your spouse, your room, your equipment, your musical taste, how loud you play, etc. And even then you might think my suggestion wasn't exactly what you had in mind. 
And please remember: What
I hear is not what you will hear - and describing sound just doesn't make sense. So -

Please do not ask what to build!

And please do not ask if any speaker driver is value for money or how they compare. A low-cost, well implemented driver may do just as well as any high-end driver costing ten times as much. Producing a 6" speaker driver can be done for less than 10 USD and in many ways do as well as a driver costing ten times as much. The suggested increase in performance of high-priced drivers may be well justified from dynamic head-room, distortion, etc., but to some ears it doesn't matter. As in any hardware trade we're into the area of diminishing return of our investment. We may pay dearly for small increments in performance and whether it is value for money is a futile discussion like the value of a Rolex watch or Gucci handbag. Beauty and value is in the eye - or rather brain - of the beholder.

I have quite a few questions regarding the amplifiers, turntables + cartridges, CD-players, DAC, etc., I use, and only thing I can say is that what I have suit my needs. Whether this will be good for you, I can't tell. Generally tube amps are more fuzzy compared to solid state with regard to hum and noise, and I take no responsibility whatsoever for your purchase or build. I have to add that with the EAR Yoshino gear I have never had any trouble with noise or hum. Tim knew what he was doing.

Thousands of commercial speakers have been made over the last few decades and they may vary from tiny 2-litre shoe boxes to humongous monsters of 150-300 litres, and the sound coming from these speakers can be like night and day and we may favour one particular brand of speakers or speakers with polyprop cones and softdomes - or hard cones and tizzy tweeters, or we just love 15" bass drivers with huge midrange horns delivering PA transient response.
We may have read a lot on speaker design and some writers are better than others and we may think this guy's got it right and when we know what we're listening to, we may also like this particular speaker better because we have learned it is right. I'd say knowledge is a serious hindrance for objective evaluation. If we had to pick our speaker from behind a black curtain we might pick something we seriously never would have done if we knew what it was. That said, a lot speakers are bought based on looks rather than sound and because it looks good, we may also seriously argue the sound is good. It just must be when it's so damn good looking. We know that magazine reviews are not objective in any way, because reviewers rely on adds and sometimes items are actually given to the reviewer as a payment for the review. Pure business and backslappers. The best you can do is attending hifi shows and hear a lot of different brands and make up your mind on size, cost, etc.

To summarise:  Please  do not ask what to build, which speaker sounds the best and what is the difference in sound between two speakers. Thanks! Much appreciated!

Always consider size, cost, complexity and your current skills in loudspeaker building before engaging.


Size (matters)
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This may seem an odd place to start, but nevertheless: You must have an idea about what size speaker you're aiming at. What is the size of your room and do you have a wife who thinks loudspeakers are ugly and should be stuck away on shelves in upper corners of your living room? You need to address these issues first. No point in dreaming about a 100 liter floor-standers if it means divorce.
What I have experienced from mails coming in is that people may have chosen a (small) low-efficiency speaker and "compensated" by buying a powerful amp, and they find out the speaker really can't play that loud all the same...It doesn't work that way. We must look at the size of the main driver, and if we're dealing with 55-75 square centimeters of membrane area (4" drivers) it simply cannot move a lot of air. You may have heard a speaker with a 10-12" bass driver and we're talking 300-500 cm^2 membrane area. Up to ten times more radiating area compared to a small mini-mini!
Even a 6" driver, typically making some 130-155 cm^2, won't move a lot of air in a vented or closed enclosure. A high-efficiency 6" in a huge rear-loaded horn may be another story, but few people build these things.
Generally people have too high expectations from their diy projects and buying high-quality small drivers won't compensate for the lack of radiating area. So, size matters!


Whenever you fall in love with a design, make a mock-up from cardboard and tape to see how it fits into your room. Here from someone making the Ellam FLEX 3W in cardboard next to a 6+1 stand-mount. Very good idea!


Cost
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Next: Take a deep look into your pockets and decide what amount of money you want to spend on your speaker adventure. Be prepared it will cost more than you think when you scan driver specs and think: Well, a pair of drivers - can't be that serious. You need at lot of components before the project is completed and you may even have to buy additional tools to finish your cabs.
So, is it going to be 500, 1,000, 2,000 or 4,000 EUR?? For 2000 EUR you can build a pair of speakers that will compete with some serious high-end commercial speakers at 5-10 times the building cost - that is - if you choose the right combination of drivers and have someone design a proper crossover. Sometimes commercial speakers are priced deliberately high, because we may think that a cheaper product may not be as good as an expensive one. Bear in mind also that diy speakers will never have the re-sale value of some well-known commercial speakers. I've seen used ProAc Response 2.5 speakers sold for horrific prices, alone due to the ProAc badge.
Speakers are also a show-off thing, something people may want to own to impress friends - like cars or whatever paraphernalia we buy to create attention. B&O score high here in Denmark for show-off. People may think you're filthy rich (and well, you have to be well off to buy serious B&O stuff!) if you own a whole bunch of B&O gear, where "hardcore" hifi gear like huge horn, fancy turntables and glowing valves may only produce sympathy for the poor spouse having to live with these ugly monsters.

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Bass extension
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People have very different expectations when it comes to overall bass performance. We may all be acquainted with earthquake subs at hifi shows and would like our home speakers to shake our guts as well, but we won't experience anything alike from a modest 22 liter/6" woofer floorstander. I can't be done.
To clarify your requirements on bass extension, visit a hifi store and listen to a range of speakers based on 4", 5", 6", 2 x 6" and bigger bass drivers if available and try to imagine how this will perform in your own listening environment.
You may think that in order to produce decent bass, you need speakers with a linear response down to 30 Hz. Now, 30 Hz would be nice - if the room allows - but I wish it was possible to demonstrate to all first-time diy'ers what it sounds like when we compare a 6" bass driver with -3dB @ 30 Hz to a 12" bass driver with -3 dB @ "only" 50 Hz. Most people would probably agree that bass can mean a lot of things.
Some useful into here: http://www.troelsgravesen.dk/HES.htm#size

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Efficiency
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Efficiency as such is more of academic interest. Efficiency is inversely proportional to the moving mass - and proportional to the square of the product of cone area and BL. Please read here. Efficiency is usually expressed as dB/1 meter/1 watt.
Loudspeaker manufacturers usually claim a given sensitivity for 2.8V input measured at 1 meter distance. And be prepared, many manufacturers claim some 3 dB more than what it really is. Read John Atkinson's measurements in Stereophile.
Some people think a 4 Ohm speaker is better than an 8 Ohm speaker because it will play louder for the same volume setting on your amplifier. Well, it only plays louder because it draws more current from your amplifier. If we look at the watts going to your speaker it may not look that favourable.
Read some background info here on speaker sensitivity:  https://www.audioreputation.com/speaker-sensitivity-explained/


Efficiency: My favourite subject, but I won't get into details here, but refer to my pages on high-efficiency speakers listed here:
High Efficiency Speakers intro, discussion.