Ported vs Sealed Speaker Box

Closed vs ported speaker box
If you are designing a speaker for the ultimate music experience, you are likely to stand at this crossroad. So, this video is about making a choice between the 2 systems.
First let me introduce the two contestants
In the red corner
The closed speaker box aka sealed enclosure. Its descriptive of what it is, a box or cabinet essentially as airtight as possible, where there is holes cut-out for the speaker drivers, and then with those mounted the box is sealed. This provide a very quick response of the speaker driver and a lot of audiophiles really likes this type of system.
In the blue corner
The ported speaker box, aka vented speaker box, is typically using a piece of pipe out of plastic or thick cardboard called a port. The port serves to assist the speaker box to resonate at a lower frequency with less movement of the speaker driver. This helps the speaker driver to lower and more powerful bass. But it comes at the price of a slower response because the pressure must build up in the box, before it can generate the resonance through the port. This is called time smearing because the impulses of the bass will start to overlap more.

But like any drama it’s never that simple and the likely hero might have dirty secrets and can be abusive to certain types of woofers.
And this is certainly the case for woofers. They themselves have personalities because of the way they are build. So, an 8” inch woofer is not just an 8” woofer.
The traits and personalities of speaker drivers are mechanical and electrical, and 2 guys where able to map this out and named a list of data by the name of Thiele-Small parameters. Here is an example:
Impedance (Z) 8 Ω
Resonant frequency (fs) 38 Hz
Max. frequency range f3-5,000 Hz
Music power 80 WMAX
Power rating (P) 50 WRMS
SPL (1 W/m) 90 dB
Suspension compl. (Cms) 1.43 mm/N
Moving mass (Mms) 12.5 g
Mech. Q factor (Qms) 2.38
Electr. Q factor (Qes) 0.55
Total Q factor (Qts) 0.44
Equivalent volume (Vas) 37 l
DC resistance (Re) 6.2 Ω
Force factor (BxL) 5.9 Tm
Voice coil induct. (Le) 0.45 mH
Voice coil diameter 25 mm
Voice coil former aluminium
Linear excursion (XMAX) ±3mm
Eff. cone area (Sd) 137cm2

With these parameters you can calculate a likely good outcome for your woofer.
But let’s not get to far out on the deep end, and go right after getting the essential question answered, sealed or vented?
An excellent way is by calculating the EBP value, with stands for Efficiency bandwidth product.
This number is generated by finding where the woofer is resonating in Hz (hertz) and divide by how much electrically the woofer is resonating.
The point where a woofer is resonating by itself, is called the free air resonance frequency or just resonance frequency. In the Thiele-small parameters it will be called fs, and again measured in Hz.
How much the woofer is resonating electrically is named Qes. The higher this number is the more its resonating, and the electrical resonance is far more dominant than the mechanical.
This gives us a very simple formula EBP = fs / Qes
So, let’s say you already have a speaker driver like the one showed earlier in the description.
We find fs to be 38Hz and Qes to be 0,55.
38 / 0,55 = 69
What does an EBP of 69 mean?
The EBP has a scale in which the ideal boxes are represented.
50 is ideal for a closed speaker box
90 is ideal for a ported speaker box
So 69 is right down the middle so can choose either system and choose what you like the best, closed for best impulse response or ported for extended more powerful bass.

If the EBP was let’s say 58 so likely success with closed speaker box, and here again in uncooperative manner are choosing a ported box are you likely to get a muddy and unclear bass response.
In conclusion
One system is not better than the other, and it’s important to calculate the right box for a given speaker driver or to find the right speaker driver for your box in order to get a nice bass response.
As a heads up for you that wants to replace your woofers in your speakers because you cooked them at the last party with some Hypertraxx music, or other situations that lead to this search for woofers. Think about this aspect and perhaps you can initially use the EBP value to filter the useable from the unusable woofers. But there is more to picking a woofer that will work in an existing speaker, but that’s going to be another video.

A dedicated website to our speaker repair and service with more detailed information is currently in the works - keep an eye on http://audiovega.com/. I specialize in refoaming a diverse range of brands, having a wealth of experience with JBL, Cerwin Vega, Snell, Dali, Bang and Olufsen, and Scan-speak drivers. My proficiency particularly lies in refurbishing and upgrading crossovers, as well as carrying out driver replacements and upgrades that often necessitate precise measurements and calculations. Trust that your audio equipment is in capable hands.

Kind regards
Kent Larsen