My first speaker project

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db!

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Joined 2009
#1
Hi guys,

As I mentioned in the intro section, I am new to the audio scene. Throughout the process of collecting parts and planning my tube amp project, I've been hit with another dilemma; a good pair of speakers.

I am looking to build a simple pair of "desktop" speakers utilizing either the HiVi M4N or the HiVi B3N. The recommended box volume for the two drivers are 4L and 2L respectively. Would a straightforward MDF rectangular box(of the appropriate volume) work properly? I know that square boxes should be avoided but it's the only design I can build without screwing up(My woodworking is atrocious). Are there any other "tweaks" that can be done/added to a square box to improve the performance? Also, since the M4N is classified as an "extended range woofer", would it require a set of tweeters to handle the highs?

I apologize if these questions seem stupid or trivial to you guys. I'm still trying to "finding my way around" so to speak.

Cheers,
db!
 
#5
When you say "square" do mean that all the corners/joints are square, or that all the outside panels will be the same dimensions? The latter would be a cube, and should probably be avoided, except perhaps for small sealed sub-woofers.

If you mean the former, remember that it's just as hard to cut parts to exactly the right dimensions and squareness, regardless of the relationship of dimensions (aspect ratio) of the 6 sides that create a "standard" box. There are certainly some aspect ratios to avoid, and some that have sonic and aesthetic advantages.

I'm a big fan of the "golden ratio" approach. It's not all that hard; once you've settled on the net internal volume of the enclosure (ported or sealed), use a cube root calculator to determine a central value, then divide and multiply that dimension by 1.618. Unless you're building a Swiss watch, rounding to the nearest 1/8" or so is perfectly acceptable.

Then add allowances for material panel thickness and that's it. Cutting them perfectly and assembling will be a bit trickier.

For example a 1 cu ft box (internal) would result in

12" x 12" x 12" = 1728"^3

12/1.618 = 7.416 ~7.375"
12x1.618 = 19.415 ~ 19.375"

7.375" x 12" x 19.375" = 1714.6875"^3 - a difference of less than 1%

If you have CNC cutting machines available with accuracy to tenth of a mm (sorry to switch units of measure), you could probably reduce that difference to even less - but considering the manufacturing tolerance of drivers that you'd be installing, rather a waste of time.


Of course, you need to predetermine if your diver of choice will actually fit in a Golden Ratio box, with appropriate "breathing room", clearance from rear panel for voice coil vents, etc., and how the resultant width might affect calculation of BSC if any.
 
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#7
Chris ,sorry for this mean question. You said "Golden ratio" and the relative allowance of small errors in the box measures ;then , referring to a particular model by Fostex , you said that it was behaving differently depending on which amplifier. Do these statements contradict themselves ,in the way that each driver can be put in different cabinet ratios ,following each its own way depending by its unique parameters ?
Bye
 
#8
2 Litre = 2000 cm^3
cube root = 12.6 cm
12.6 x 1.618 = 20.4 cm
12.6 / 1.618 = 7.8 cm

204 x 126 x 78 mm internal

4 Litre = 4000 cm^3
cube root = 15.9 cm
15.9 x 1.618 = 25.7 cm
15.9 / 1.618 = 9.8 cm

257 x 159 x 98 mm internal

Sealed is very tolerent of variation of the volume... stuffing makes them seem bigger.

12mm ply would be fine for the little box, 15mm for the 4 litre, at least a size thicker if you use MDF.

dave
 
#9
Hey guys, I appreciate all the info.

By square, I meant to say rectangular; I apologize if this caused any confusion. Most of the rectangular designs are relatively large and utilize complicated waveguides and such; this is beyond my size limitations and building abilities.

I have reviewed the "overnight sensations" design and I feel that it's well within my compatibilities. My only gripe is the size; it's a tad bit longer than I'd like it to be. Would it be possible to build it smaller as a sealed design, then use stuffing to artificially increase the size?

Just for curiosity's sake, is there anything particularly disadvantageous of a perfectly square box?

Thanks in advance!
 
#11
picowallspeaker said:
Chris ,sorry for this mean question. You said "Golden ratio" and the relative allowance of small errors in the box measures ;then , referring to a particular model by Fostex , you said that it was behaving differently depending on which amplifier. Do these statements contradict themselves ,in the way that each driver can be put in different cabinet ratios ,following each its own way depending by its unique parameters ?
Bye
Click to expand...


Well, my reference was to a specific enclosure design for a particular model of Fostex driver, the microFonken for FF85K:

An externally hosted image should be here but it was not working when we last tested it.


While shown in above photo at a computer store being driven by a Kingrex class-T digital amp, they sound much more musical to my taste on tubed amps.

While of course some of the differences one would hear on these speakers on various amps could be attributed to interplay of output damping factors and the speaker's net tuned impedance characteristics, there are often other issues at play. In addition, few of us get the opportunity to audition as wide a range of gear of different design topologies as professional reviewers, so by default our pronounced opinions are best formed on our actual experiences.


Let's just say that regardless of enclosure type, the FF85K is not a driver that ameliorates or camouflages the sonic signature of associated equipment to the same degree as other drivers I've heard.

Driven by the Kingrex, I found the FF85K to quickly become rather irritating - mostly in terms of upper midrange "glassiness" and "coarsely grained", if those descriptions make sense. By comparison a 3W or so class A EL84 PP triode, or 7 W 300B SET were for me quite simply so much more musical.

What I said was:
For my own taste the FF85K is far less tolerant of digital and chip amps than other Fostex or Mark Audio drivers.
Click to expand...
What I should have said is "With the FF85K, I found (the) digital and chip amps (can't remember which specific chip-type) less tolerable than with other Fostex or Mark Audio drivers" (specifically something like the FE167E or CHR70, Alpair6)

In other words, the relative degree of tolerance was my own, and as any DIYer with more than a few laps around the dance floor understands, YMMV, etc. 🙄

I can certainly see how the composition of that post might be misread, hence the long winded "clarification", but pardon my density - I'm not sure how other comments made in difference contexts might be in contradiction.

cheers
 
#12
db! said:
Hey guys, I appreciate all the info.

By square, I meant to say rectangular; I apologize if this caused any confusion. Most of the rectangular designs are relatively large and utilize complicated waveguides and such; this is beyond my size limitations and building abilities.

I have reviewed the "overnight sensations" design and I feel that it's well within my compatibilities. My only gripe is the size; it's a tad bit longer than I'd like it to be. Would it be possible to build it smaller as a sealed design, then use stuffing to artificially increase the size?

Just for curiosity's sake, is there anything particularly disadvantageous of a perfectly square box?

Thanks in advance!
Click to expand...


Well, first of all, try to remember a 3D "perfect square" would be a cube.

Dave fairly well summarized the reasons not to build this shape in his reply #10

As per one of my own earlier posts, as long as you maintain the internal volume, there's no reason you can't alter the enclosure's dimensions (within reasonable constraints) to better suit your aesthetic or space requirements. This is particularly true with sealed enclosures - just be sure that your driver of choice will actually fit 😱, and that any special allowances (terminals, vented voice coils, etc.) aren't occluded.

And at the risk of stating the obvious (but nothing can really "go without saying", cannit?) unless you're overlapping butt joints in one particular way, or using simple miter or glue lock joints on all 24 edges, (both of which I'd highly recommend against, particularly for an inexperienced builder), even a perfect cube would have panels of at least 2 different sizes. So by the time you've calculated for panel thickness, it's really just as easy to fabricate a non-cubic rectangular box.
 
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#14
I can certainly see how the composition of that post might be misread, hence the long winded "clarification", but pardon my density - I'm not sure how other comments made in difference contexts might be in contradiction.
Click to expand...
I did understand what you intended to say , but ,pardon , I enjoy reading a spread out speech such as your reply 🙄

Well,a little bit I was concerned for the fact that those "little critters" would play well only with ( relatively ) lot of air in the back .Now I got it.
Talking about power amps , I never heard class D or T amps , and I believe that particular "spikes" or roughness could be well be analyzed by such motorized-membranes !
Thanks.
 
#15
db! said:
So, I'm pretty much set on the overnight sensations design; now, is it possible to build it as a sealed design by simply eliminating the vent?
Click to expand...

Nope. Sealed and ported are 2 different 'technologies'. If you simply eliminate the vent, you will end up with a pretty low Q, ie weak bass, and won't like it. But there are good news for you down the road:

A sealed design always yields to a smaller box. Why don't you simply put your parameters into WinISD and let it design the box for you. You will end up with a good implementation that you'll be proud of.

Good luck
 
#16
Suricat said:
Nope. Sealed and ported are 2 different 'technologies'. If you simply eliminate the vent, you will end up with a pretty low Q, ie weak bass, and won't like it. But there are good news for you down the road:

A sealed design always yields to a smaller box. Why don't you simply put your parameters into WinISD and let it design the box for you. You will end up with a good implementation that you'll be proud of.

Good luck
Click to expand...

I think that as noted in his first post of this thread, db! is quite new to this DIY game, or at least the speaker design & build part - if knew how to use WinISD to solve this question, I'd respectfully suggest he probably would have already done so.

db!:

Modifying a tested enclosure design is always risky, and either reducing volume of a ported design or converting to sealed to shrink the size are recipes for disappointment.

Installing a port in a small box like this isn't rocket science - provided the math is right on the port's tuning to box volume, all you need to do is cut the tubing material to the correct length and drill the right sized hole.

In fact I've seen some designs engineered to allow the use of ports a standard spade bit or hole saw diameter, and either a single or small number of layers of panel material thickness.

However, if it's not an issue of build difficulty, but of finished dimensions, you might be best to look at something using different driver(s). Have you determined what would be an appropriate sized box for this application?
 
#17
Hey guys, I appreciate the suggestions and info.

chrisb - I am looking for a box that is approximately 6W x 9H x 6.5L outside. These dimensions aren't too far off from the overnight sensations design. I'm actually planning to use the same combination of drivers, tweeters and crossovers.

Changing the driver would probably require me to design a new crossover network; something I would prefer to do at this stage.
 
#18
DB! I think you've got the info you need.

Use http://undefinition.googlepages.com/...ightsensations as your guide line.

Do you need a tweeter when using the M4B ? yes.

Can you do 5.5x6x9 ? yes. with .5 MDF, that's about 3.6L.

Will this shape affect the sound in a bad way ? no. Sleep tight on this.

Will you gain anything by adding a port? yes, but you'll have to increase the size of your enclosure. Hey, maybe this should be a second project. You will then be able to compare sealed vs ported. (hint: both are good !)

I think that you will gain significant knowledge at simply trying it. I propose that you bring your dimensions at home depot and get the wood cut for you. It's darn cheap and you will end up with 90 degrees square pieces. Just tell the guy that all 6 inches must be 6, not 5.9 or 6.1. No variation. He do it. You can even get someone to pierce your circles, or do them with a jigsaw. Take your time.

Glue with white glue and you will be fine. You can complicate things but it will not give you more.

Feel free to email me directly.


Good luck
 
#19
I meant 6W x 9H x 6.5L !

I just plugged these quickly in WinISD while sipping my coffee. First thing, this is a very capable driver.

Sealed: The optimum box volume would be 0.208 cu ft. There are good news, sealed designs are forgiving so your size values, with .5 thich panel will be fine. However, no one can tell you if it will sound right, you have to test it. But I am very confident. Even with the volume that speaker will take in the enclosure. --- If you can have 7.5L, it would be better but you should be OK with 6.5.

Ported: The optimum box would be .4 cu ft with a port tuned at 43 Hz. I like simulation programs, this little driver that could now gives me a graph similar to dual 15'' ! As expected, the whole enclosure will go deeper in bass but it is also bigger. But then again, do not expect earth shaking bass.

Hope this helps
 
#20
>Changing the driver would probably require me to design a new crossover network; something I would prefer to do at this stage.<

dB! , this is the sanest thing I´ve read in a long long time. A first project is headache enough - trying to do a crossover for it without measuring tools and a crateful of Xover parts for trial and horror - your first project would be your last.
 
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