After I posted this video, I noticed that the RU-vid processing "evened out" the sound level somewhat, so that you couldn't hear the "peaks and valleys" of the sound level at different frequencies. You can still hear it, but it isn't as pronounced as it was when I recorded it live.
The Radio Shack book titled "Building Speaker Enclosures" by David Weems is a very good BASIC explanation of much of the science behind speaker design. Of course it is dated, but the foundation knowledge holds up. I built the 38" sealed box project 3 way, 12 inch woofer straight from the book back in the mid 80s and to this day they have been the best sounding speakers I have heard. All radio shack parts. I wish I still had them today, I have a pair of the same cabinets but with Daton drivers. Good, but not as good as the Realistic originals at least as I can remember.
Good video Tony! Since you mentioned it but didn't go too far into it, while excursion is lower around the tuning frequency, below vent tuning when the driver starts to become unloaded, it becomes a lot more stressful on driver excursion and starts to become easier to bottom (former hits t-yoke) to the point where on any mass loaded design, especially larger vented subwoofers, you really should always high pass them and filter everything below tuning, and steeply! just to keep your woofers safe at high power. The usable frequency response drops off sharply under the tuning frequency anyway. Filtering below tuning is good practice :)
Tale of two ports. Very interesting video demonstration. I first saw it a few months ago. Have been ruminating a speaker enclosure design (may have been spured on by it) that has two different drivers each covering a different section of the band width. In such a scenario with two ports, with each port fashioned around one driver and its Small Theil parameters and the other respectively fashioned around the other driver's Small Theil parameters. Each port adjusted for the volume of the enclosure of course. Have searched such a possibility but the results indicated that the combined ports would be summed as one with a divergence not suitable for the driver. They of course are talking about one driver. That brought me back to this demonstration. Your demonstration shows clearly your two ports have two distinct tuning frequency that do may how ever overlap. Your thoughts would be nice to have. I believe at worst each driver will have two port tuning frequencies one ideal and the other present but muted.
Great Demo. I've always been "baffled" (pun intended) by all the articles floating around about ported vs. sealed sub-woofer cabinets. You demo provided me with some valuable insight.
Tony, here is a fun demonstration you can show your viewers. The air in a port holds the driver still at the port tuning frequency. Turn the speaker, driver face up. Put a styrofoam peanut in the cone. Do a frequency sweep. The peanut will bounce around in the cone until it gets to the frequency of the port at which point it will stop as the cone is held still. Then it will start to bounce again as you sweep past the port tuning frequency. Since each port is tuned to a different frequency, that should happen twice depending on how far apart they are tuned.
This is a fantastic demonstration. The most important take away is this: "We all have different hearing...your ear doesn't hear things very linear either". Also, your hearing changes as you age, so the same speakers that sounded good to you when you were 20 may sound dull and lifeless to you at age 60. It's beneficial to keep that in mind when selecting speakers.
Excellent video! Thank you. A picture is worth a thousand words... When I ran pro audio, in the late 70's/early 80's, we knew that 250Hz was a hyper-efficient spot in all types/brands of speakers and that it muddied up the sound. We routinely removed it with active equalization.
Really enjoying your videos! I have a pair of the RadioShack speakers that I am rebuilding for my son based on your example. Mine say RCA on the front and have cloth covering the tweeters. Looking forward to listening to them once I get the woofers installed ( and broken in)! Thanks - Mike
Good point. The ports aren’t blowing air like a fan, they’re resonating like a pipe organ. And like a pipe organ, they have different lengths for different frequencies.
You do a good job of explaining the basics of a speaker cabinet system. FYI when the speaker and flaps are moving in and out together they are in phase, not resonance. The point to a port is to take sound waves which are 180 out of phase compare to the front and flip the phase to be in phase with the front of the speaker. It is great that you explained that everyone of us heard differently. With test equipment (available at parts express) you can test the frequency response and impedance curve. Two different length ports is a perfectly valid way to tune a speaker cabinet. The impedance curve will tell you what frequencies the ports are tuned to.
I mess with speakers all the time I collect them. I prefer open baffle speakers now that I have lived with a set for 2 months. Would love for Tony to build, test and demonstrstes open baffle speakers. We know you have a wood shop Tony!
Nice job!!! As always, even when you say you only scratched the surface of the science, your video is a perfect demonstration how science works, trying to understand and explain how these ports function. And how these apparent insignifiant things are scientifically designed and tuned to match a certain material configuration to meet some physics laws. But it's also clear to everyone with a little knowledge about speakers design, it's a gigantic and complex and very personal domain. Even with perfect maths and physics, applying known recipes from a 200 pages cookbook of any sort, a RU-vid guide or else, like following the precise explanation from some makers kit, the result is always a compromise, wich has to fit many other parameters including the electronic used, the room and it's dimensions and own resonances, and finally your own personal appreciation about the music you listen, to a global budget. I'm what some call a HiFi geek, building and designing things on my own but also selling material for over 35 years +. And I've also been working with some of the best loudspeakers designers, comparing their production and what the general public or customer feel and ask for, and the results are someway surprising. Some of the no compromise level designing systems with perfect extensive tests in special measuring sound chambers were definitively not the most appreciated. These same speakers were also demonstrated in HiFi conventions in direct comparison between real instruments and voice, only to show how difficult it was to compare from each other. But finally, most people were preferring with the same budget a simpler or sometimes some weirdest designs with a coloured sound (flashing lights!), with a non linear response and clear phase distortion. Most don't care about absolute precision and good labs measurements, some buy a brand or a product they've read good critics in the press, others buy something expensive to show how wealthy (or not) they are, and I must admit it's near impossible to find a shop where you can compare different speakers in good conditions, as far as these are not in a monstrous audiophile budget. I also know some engineers scientifically design their production to meet a larger audience appreciation (I won't give any names), and at the opposite some rare (fools) others conceiving theirs with a statistical try and error approach of direct listening each tiny "improvement". You can guess most have for only goal to keep a budget and margin design: when you ask for a accountant to design something for a certain target with a specific price... And it's a market where everything sells, as far as you pay people to advertise it, others to write good critics in specialized press and now to post videos in social medias. I won't say this market is corrupt and distasteful, as you have some product like this low budget good compromise speaker pair with distinct proof a nice and extended design. But I perfectly understand those who say it's a no no!
Thank you sir for this simple and excellent explanation and demonstration of this subject that confuses many. Another manifestation of air not entering or leaving through the port is the passive radiator on some design (which is basically a ported speaker with a free moving cap or cover over the port). If I'm not mistaken, the chuffing is not caused by air 'escaping' below the port's resonance frequency (the woofer can produce little movement there anyway and ported speakers roll off steeply below the port's resonance). I think the chuffing is rather caused by friction of the vibrating air within the duct, especially at its ends; that's why you see speaker manufacturers mitigating this with various bevellings at the end.
Okay Tony, nice demo! I got into speaker building back in the 90's, bought books, tried out many designs, driver's, materials. I found small enclosures a disappointment. I won't mess with any ported speaker under 1.5 cubic ft. Like you said, preferences. You mentioned those drivers were designed for that enclosure. Marketing? Maybe. Their idea of that could be bolt pattern and wattage handling. I can see just by observation the new cones have more throw than the old. If you have a spec sheet, you could run the numbers through an enclosure calculator to see if it jives. Great job on the slow motion shots, I'm enjoying this series!!
Hi! I would appreciate a similar video on ported vs sealed speaker cabinets. Also I just restored a pair of Dynaco A25 speakers from the 70s, they are said to use an "aperiodic" enclosure, which seems to be halfway between a tuned port and an acoustic suspension, it uses a sort of damped vent that reduces the resonance and impedance variations. If you could elaborate somehow on this I think it would be very interesting!
My B&W DM305 are a two way 6.5" which have a wide slot port just under the bass driver in the top quarter of the enclosure which is separated from the bottom three quarters by a sponge or foam filter and the bottom end has a cylindrical port on the back.... Blocking one or the other or both makes a huge difference! I listened to a lot of speakers in this price range and these seemed to produce more and deeper bass which is what I was after back in the 90's.... Although my first choice would have been a set of Tannoy dual concentric speakers which had this amazing ability to place sounds where I knew that there were no speakers and yet I can hear instruments there.... I have not heard anything like it since! But at $2kAU, it just wasn't going to happen so I settled on the B&W which were just over $1kAU.... If you ever come across a set of B&W DM305 speakers, I see them show up from time to time for sale and they are not expensive, I recommend getting them, they have an amazing sound! Highly recommended...
Some speakers actually benefit from plugging the port. Some woofers in ported enclosures of cheaper speakers from the 80s onwards, already have a free air Q greater than 1, which makes those quite unsound (no pun intended) designs, and that's only done because it is/was fashionable to have a large obnoxious port making "boom boom" sounds. Such woofers need a sealed box to sound alright.
16:05 Good demo especially the slo mo at the end You seem to have spent some time getting a firm grasp on the mechanics, so I'm a little surprised you haven't done any actual measurements (listening on youtube is not the best way to go )
Very interesting. Though, as tou said yourself, the driver was too big fkr the box anyway. I'd try to make a new faceplate using the old smaller driver. Or just make an adapter panel for the current gole to accept the old smaller driver, and ug the holes as it was used in a sealed design.
Thanks. Does the 'DB' or sensitivity etc improve worsen by plugging up the ports. I can remember a myth buster show where they were trying to get the brown note and they plug the ports in the base drivers to increase the decibel rating or something all the best
When I worked in the audio store while in college, they salesmen used to refer to the low cost "big speakers" as boom and sizzle, because that's what they sounded like. The bass was very boomy and loose and the tweeters sounded like eggs sizzling in a frying pan. They were, however big and loud ;) They made my ears hurt, and not in a good way!
@@xraytonyb That's funny! Makes sense. It's funny to think that now so much consumer stereo equipment no longer attempts to meet hi-fi requirements. My kids go for stereos that have exactly that: big booming bass. Rather than sizzle treble, though, they go for muffled treble... it's like they are in a rush to feel as of they have hearing loss... :-) Cheers Mark
Switching drivers of a speaker is a tricky thing, a speaker from factory is 'tuned' for a certain driver (either dynamically or by crossover circuit), finding the right sounding replacement can be tough. Dayton DC130AS-8 5.2" woofer may be a better fit for the Optimus LX-5 enclosure
5:08 So, if I understand your explanation correctly, effectively the ports act as resonators with a unique Q (per port) and in combination produce a third resonance which will be due to the superposed resonance of each port and which will have a third Q, which will be mathematically linked to the other two port Q values? Interesting.
It is another misconception that ports allow for a smaller enclosure. The opposite is usually true. A ported enclosure should usually be larger than a non-ported enclosure.
But the sealed enclosure will be missing a full octave of bass extension compared to ported using the same driver. If you take say a 6.5" woofer in an optimally sized ported enclosure, and then work out what you will need to achieve the same amount of bass in a sealed enclosure you're probably looking at a 12 or 15" woofer and a much bigger enclosure. Physical size, bass extension, sensitivity, pick two. If you give yourself a given physical volume to work with and freedom of all other components and parameters, ported will have poor sensitivity and sealed will have poor bass extension. To improve either you have to make everything bigger.
@UClXrY49V1fcRQ_3d8aSLS3w iI am certain you know much more than me on this subject, but you are arguing apples and oranges here. My simple statement was that for the same driver an optimally designed ported box will usually have more volume than an optimally designed sealed box. It is a misconception that adding a port will allow for a smaller enclosure. Yes, it will usually allow for a smaller driver to achieve the same bass response.
@@seanobrien7169 allowing for a smaller driver is how you achieve a smaller enclosure with ported, since smaller drivers allow for smaller enclosures. If you blindly pick a driver and then are tasked with designing the smallest possible enclosure that doesn't sound terrible, then yes you will likely end up with a sealed enclosure. Also some drivers are very ill suited to one type of enclosure type or the other. The optimal sealed enclosure for a driver suited to ported enclosures will be tiny and with non-existent bass response. The optimal ported enclosure for a driver suited to sealed enclosures will be so massive that it will be impractical to build it.
@@tmmtmm lol, you are WAY overthinking this. You are not wrong, but you just don't seem to get what I am saying. At the end of the day there are MANY variables, we haven't even touched on labyrinth, horns, folded horns...Driver characteristics...Crossover design...Yeah...I am simply saying that many people believe that by drilling a hole in a speaker they can have a smaller box with the same drivers. This is not necessarily the case.
BTW, I have listened to many great speakers of many designs. I like ported speakers, but I am old school in that I do prefer huge sealed box speakers. I love 12-15 inch woofers in 38 inch + cabinets. I like boomy bass. I am not an engineer or audiophile, just a casual enthusiast. 🙂
If you could do the same type of video with a drone cone ( passive radiator) loudspeaker, with different drone mass loadings, affecting it's resonance/ tuning, with the slow frame per seconds cam, that would be great!.
A port and a passive radiator are pretty much the same in principle. The air column in the port is like a cone and the air cushion in the cabinet is it's suspension.
Interesting video. I have a question which you may or may not be able to answer. I have seen some speakers that are ported that the company provides port plugs for. Can the speaker actually be designed to sound good with plugs in even though it was designed to have the ports? Or is it all subjective?
@@westelaudio943 thanks for the reply. Ive have a pair of ported speakers (in the front) and have tried putting plugs in them but to my ears it effectively negates most of the bass response. My speakers I dont think were designed with port plugs being considered. Still a very interesting subject.
Typically a speaker designed for optimum response in a ported speaker ends up being around a Q of +/- .6 as a sealed cabinet. A sealed cabinet with a system Q if .707 is optimally flat. A sealed cabinet with a system Q of. 5 is optimally damped (meaning it follows the input signal more closely) but the bass response droops down compared to a Q of. 707. However, if you put the speaker near a wall, that wall will reinforce the bass bringing that droop up and actually get you back closer to a ported cabinet response. The trade off is that you don't know (without test equipment or at least some math) what frequencies will be boosted creating more of the hot spots Tony talked about. If you take a ported speaker and put it near a wall, it will boost what is already flat response probably messing up the speakers sound balance. So the reason for the port plugs is to help compensate for room acoustics and speaker placement, as well as personal preference. As tony said, we all hear differently. Finally, a port inverts the out of phase sound inside the cabinet to be in phase outside of the cabinet. Therefore there is a range where the sound from the speaker is not in perfect phase with the sound from the port. Also ports cause what is called group delay. Some people can hear those issues, some can't. Those that can, like sealed cabinets better.
Any idea what these Optomus 2-way speakers are worth without doing the re-foams? I have 4 of them of the second series model. I would also like to know if the DI-pole tweeters could be removed and used on a much nicer 3-way speakers with 15" woofers?
@@PerthSoftware, Sounds encouraging. I have a pair of the Optimus Di-pole tweeters on my bass reflex speakers. Two 3-way speakers on each side. I prefer the sound quality of larger speakers.
