Want to Build A Speaker? Sure You are Ready?

Some often missed measurements

Building your own speakers can be rewarding.

It can also be a real pain to build a speaker…

The typical DIY speaker cabinet is usually a basic box slapped together or just mail ordered as a speaker kit, all with an optimistic hope that things will turn out positive.

Without some careful planning this is probably a tad optimistic. I don’t want to make it sound like building speakers is overly tough because I don’t think it is, if you take your time to learn first.

There’s more to building a great speaker than throwing some good drivers into a box and carefully tuning the speaker crossover. It’s best if you take an approach that takes as much of the guessing out of the equation as possible.

It’s true that there is room for artistic license in speaker building.

 

Wavelength driver placement and internal bracing

Avoiding wavelength ‘comb filtering’ and wavelength induced resonance is your first order of business.

Actually, it’s more like the last, but I want you to understand it first so we don’t have to move backward at the end.

Braces should be placed no closer than ½ wavelength apart that the driver will play in the cavity. In other words we first need to know the drivers passband frequencies.

To find the maximum crossover point we need to establish which driver we plan to use, how far it can be mounted from the tweeter and choose the crossover point.

Want to build a speaker? Calculate your wavelength and spacing here: Use wavelength calculator.

 

Lets build a speaker example using this method:

• ScanSpeak Revelator 18W/4531G 7″ Mid-Woofer 4 ohm

• Scanspeak Discovery 10F/4424G, 4″ Midrange 4 ohm
instrument 7 loudspeaker sealed cabinet concrete baffle stereo speakers
• ScanSpeak Illuminator R3004/6020-10, 1″ Tweeter Soft Ring Dome

I plan to make the crossover point about 3500Hz from the midrange to the tweeter. The wavelength of 3500 hz is 3.858” inches.

So I need to place the tweeter and midrange Scan Speak 10f driver no more than 3.858” apart from one another center to center.

Half of a wavelength at this frequency would be 1750Hz which is well within our pass band. So I want to make sure I have a brace closer than 3.858” apart.

In fact I really need to have the brace closer than this to avoid waves above my crossover point.

Remember, the midrange driver doesn’t just play up to 3500hz. It also will play out beyond that according to my crossover slope. If I choose a brace distance of 1.5 inches the ½ wavelength would be around 4500Hz.

Full wavelength is about 9000Hz. This is much better. But let’s stretch it a bit more to 1.75” apart. This gives us a ½ wavelength of 3858Hz and a full wavelength of 7716hz, this is pretty good. It’s above our pass-band for ½ wavelengths and totalcylinder cavity home sub woofer chamberly out of range for full wavelength.

 

I should point out now that almost no loudspeaker companies are doing this. I mean, placing a brace closer than the wavelength of the crossover point between the midrange and tweeter. Why is this important?

At the crossover point the speaker is still playing at full SPL capacity.

In our example this is 3500hz, which means that the inside of the cabinet is also getting the signal at 3500hz.

build a speaker and home subwoofer

Inside the cabinet, wavelength is an issue because resonance will build up and if not damped it will hit the back of the driver cone and enter the room. Or worse, it will excite the cabinet walls and cause them to vibrate at that frequency.

And here is yet another reason that the well braced cabinet is so important, so the vibration is extremely low in level in the first place.

A brace place every 1.75” will be a good distance if your mid-range and tweeter are crossed over at 3500hz. If your crossover point is lower, then you would not need them to be quite so close.

What else is going to happen? This box is going to be majorly braced. We will have a brace at minimum every 1.75” apart in the midrange chamber. Or we use a cylinder or unparalleled braces to achieve a near zero resonance cabinet.

Another example:

• Center to center midrange and tweeter driver placement is 5.5” inches
• Maximum crossover point is 2455Hz
• Full wavelength 5.5 inches
• ½ wavelength 2.75 inches

Another way to get rid of resonance:

So in this example we would need a brace no more than 2.75 inches apart when you build a speaker.

But more likely we need to be slightly higher in frequency, so we would choose around 2.5 inches apart for our braces.

Summary to build a speaker easier and better

Use unparalleled walls and lots of braces. Calculate your frequency based on your crossover point and place braces close enough to eliminate resonances.

You can do a lot to get rid of the resonance nasty’s by just keeping the walls from being parallel.

If using cylinder walls like we do on many of our speakers you can chamfer the edges of each layer like we do on the Mini Cube speakers to take it even further.

But unparalleled walls are a great way to keep resonaSony VIP 100nce at bay. If it cannot build up, it will die out in the acoustic damping that is inside the cavity.

 
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build-a-speaker box that’s worlds better!
crossover frequency using wavelength
subwoofer box plans
sub woofer installation
subwoofer plans
custom speaker boxes
subwoofer design
crossover point selection
custom Speaker Boxes – we build them for you
Part #1 – Important facts about Speaker Boxes
Part 2: Important facts about speaker boxes – DIY home theater speakers
Part 3 the DIY subwoofer
Part 4: Active Crossover