Driver question

DCMikeO

Member
2016-05-24 12:23 pm
Hi,

I am fairly new to speaker building, made a few single driver cabinets as a kid, and I want to build a great set of speakers. I am looking to build a 3-way system, 1 woofer, 1 mid and 1 twitter, however when looking at drivers the selection is endless! My budget for the drivers is $1,000. (This may be ambitious but that's me). Side note: I would like to make them spherical. I am able to make any size wooden enclosures, CNC lathe, however it is the speaker side I am a bit weak on.

Any suggestions or advice are welcome.
 
Hi Mike,
You may be asking too broad of a question. Perhaps have a look at speaker kits whereby the hard work is done and your job is to build the cabinets. Google 'speaker kits' and then come back with your questions. Also, spherical cabinets are not the best idea. Sound waves inside can bounce around and interfere with the sound. Parallel walls are something to avoid as well but it's still the most popular way simply because of the ease of construction.
 
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@DCMikeO I recommend getting your feet wet and building a good 2-way kit to start with, you'll learn a lot and can eventually work your way up to what works best.

In my opinion, the biggest challenge and speaker building is getting the crossover right and that's where the kits are going to take out all the guesswork and experimentation for you.

This won't be your last set of speakers, if you're anything like me and constructing the cabinets is your strength, the possibilities are virtually endless for building more and more speakers moving forward.

Definitely spend some time reading through a lot of threads here on DIY audio, there's a lot of very esoteric and technical debates (that whether they have any real world practicality and maybe questionable), they are very informative and will help educate you on a lot of the theory behind what works in speaker building and what doesn't.

Also do a little research on diffraction, diffraction is one of the biggest enemies to good sound quality and it's especially problematic in round baffles. You'll find a rectangle baffle with drivers that are not centered, with large round overs will offer the best diffraction control possible, along with flush mounting drivers etc.

Audio is also very subjective so don't be afraid to try new things and experiment, the worst thing that can happen is you learn a little something and can apply it towards future projects.
 
Re diffraction and non-monkey coffin shaped enclosures- I think one could do worse than to carefully study the B&W N800 series, Magico, Sonus Fabre. Many of those brands have been inspiration for the more elaborate work of a lot of builders here - myself included.

I'd second Cal and JShadzi's suggestion to get your feet wet with an established kit -2-way to start? - there are certainly more than enough to give one a short term case of analysis paralysis . J is right in that unless your first attempt fails so miserably as to be discouraging, this will not be your only build ever. :D

It might help if you have performance benchmark of something you've heard / liked enough to want to emulate, then ultimately surpass - in some cases that's much easier than you'd think.
 

DCMikeO

Member
2016-05-24 12:23 pm
Thank you all for your input.

Cal - I read somewhere that spherical enclosures is actually the best for diffraction along with minimizing internal resonances. Is this not correct?
eriksquires - Yes, I meant a spherical enclosure.
JShadzi - Thanks for the tip.
chrisb - thanks for the encouragement.

Another question, do you think it possible to buy a 3-way kit and re-calculate the baffle and other variables but keep the enclosure volume the same? To be honest I would like to throw all my budget into the first build. I am a quick study and logically sound.
 
Spherical enclosure is the best for diffraction, but the worst for internal resonance - there will be only one, but huge internal resonance.
Keep the width of the box and inter-driver distances the same (and distance of the tweeter to the top of the box) and vary the box height and depth to get the same volume.
 

andy19191

Member
2005-04-17 11:42 am
-
Another question, do you think it possible to buy a 3-way kit and re-calculate the baffle and other variables but keep the enclosure volume the same? To be honest I would like to throw all my budget into the first build. I am a quick study and logically sound.
The major task would seem to be designing a crossover that works for 3 drivers and a non-standard enclosure. If you opt for DSP and a 3 channel active crossover and obtain some measurement equipment then there is a good chance of a successful outcome because the active DSP can be tailored to fit what you find when you measure. A passive crossover is less flexible, requires more knowledge to design and once you have bought the expensive components and measured only to find they don't work quite as expected and things need to be tweaked a bit that involves more design and buying more expensive components.

Active is more expensive but there is a better chance that a novice with their first attempt at an ambitious non-standard 3 way speaker will create something with a good performance. An alternative others are suggesting is to first learn what you are doing with a simpler standard 2 way passive speaker before having a go at a more complex non-standard 3 way passive speaker.

Another alternative if cabinet building is relatively easy for you might be to build a good existing 3 way design such as this one that fits the budget and then transfer the parts to a cabinet of your own design. There are other designs if that one is a bit big. In the new enclosure the performance won't be as good but it will give you measurements and something to listen to as you tweak the crossover to improve the performance.
 
I read somewhere that spherical enclosures is actually the best for diffraction along with minimizing internal resonances.

A sphere was the best shape Olson tested for diffraction on the outside of the enclosure. The inside is real bad for resonances as they will all be at the same frequency.

Probably the best shap is the B&W nautilus mid-enclosure shape, a half sphere with a tapered shape on the back that gives you a long tear-drop shape.]

dave
 
Not necessarily:
Diffraction from baffle edges



Sent from my iPhone using Tapatalk


Indeed - to snip the summary conclusion from SL's typically thorough work;
While I try to minimize visible diffraction ripples in the frequency response for good measure, I have no evidence that even strong diffraction effects have significant audible consequences, except for the transition region, the "baffle step", where radiation goes from omni-directional to forward firing. Note that there is no baffle step at 90 degrees off-axis, and boosting low frequencies for a flat on-axis response will add to the downward sloping trend of the frequency response off-axis. This causes a spectral imbalance of the reverberant sound field in the room and is a major reason why I prefer dipole radiators. Diffraction effects are always spatially localized and a slight shift in listening position will change their magnitude. While the "baffle step" cannot be avoided, the additional higher frequency ripples can be easily reduced to a magnitude that is much smaller than the first arriving direct sound, by simply optimizing the proportions of a rectangular baffle. The absolute width of a cabinet is not the critical parameter that many people think it is. Much is hypothesized, little is proven and much is overrated when it comes to diffraction.
 
Hi,

Problem with spherical enclosures of any reasonable size is they
are ugly. Diffraction control can be addressed in a number of ways.

Boat shaped floorstanding speakers are the in thing nowadays.

You could do a lot worse than building these 3.5 ways :
Zaph|Audio - ZDT3.5 into a high quality cabinets
inspired by the design approach Usher takes :

[IMGDEAD]http://www.usheraudio.com.tw/wp-content/uploads/2015/01/CP-8871-diamond-W-1-300x300.jpg[/IMGDEAD]

Note for the ZDT3.5 keep the upper bass unit close to the midrange.

You won't find another hifi DIY design anywhere near as good for the money.

rgds, sreten.

http://www.parts-express.com/project-gallery-speaker-project-zdt-35

The project parts list is very wrong. Enquire if they do a special
price for the whole kit. They did in a flyer when it was introduced.
 
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I failed to see where it says that the spherical enclosure is not the best for diffraction. But, as I wrote, spherical enclosure is the worst for internal resonance - so should be avoided.
Non-symmetrical position of the driver on a simple flat baffle is more than enough for good results regarding diffraction problems. Simulations with The Edge software are very close to the actual measurements.
 
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Just for information.

The commercial version of TABAQ has the shape you see in the picture. We found this had an advantage over the original design with straight walls.

Hi
Bjørn
 

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