TAD ME1 Port Design Theory

[kostya]

Hello,

I have been looking at speakers with uncommon design characteristics, and came across the port on the TAD Me1. The manufacturer calls it a "Bi-Directional ADS: Bi-Directional Aero-Dynamic Slot", (silly name I know), from the outside it just looks like there are four slot ports, but looking at their website, an opening in either side of the enclosure feeds straight into a thin chamber, open on each end of the speaker. How does this work? I wanted to see if anyone could explain the purpose of the design. How is designing a port like this different than a standard slot port. I have attached a picture from their website below.

Side note, I don't know if there is any other component to this port design that we cannot se in this image, if anyone knows if there are other pictures or documents that display this please let me know!

-Edit: I do not intend to build a speaker with this specific port desing. I simply am interested in why this choice was made, and how it is implemented.

 

[kemmler3D]

How does this work? I wanted to see if anyone could advise me on how one would go about designing a port like this for a DIY speaker project.

I haven't built speakers but I did look into it for a while. My understanding is that port frequency is basically determined by length and cross sectional area, so they don't necessarily need to be round. It gets more complicated when any given dimension is small enough for air viscosity to matter, which in this case it might be?

I think to design ports with unusual shapes you can use the normal equations as long as the areas / lengths add up, but to do something like this with very small dimensions and predictable outcome, you probably need to do a whole fluid simulation.

Totally not an expert on this and if someone comes along and says this is nonsense you should probably listen to them.

 

[kostya]

As far as the port tuning goes yes, this is what I assumed. Hopefully this is possible to design without a fluid sim haha. I am more interested in the idea of having two port openings front and back. Will it interfere badly? Perhaps it will expand the soundstage depth, as it reflects off of the back wall? How does one design with these things in mind.

 

[kemmler3D]

I am more interested in the idea of having two port openings front and back. Will it interfere badly?

I think it will interfere if the ports aren't on the same face of the cabinet, you will get cancellation that corresponds to the distance between them. In the case of this speaker they might be using it as a sort of cardioid effect? Hard to say.

Perhaps it will expand the soundstage depth, as it reflects off of the back wall?

Probably not, ports deal with low frequencies only (ideally) and soundstage is primarily caused by higher frequencies.

How does one design with these things in mind.

My advice is don't try for an exotic port unless you have a specific reason. They basically work by resonating like when you blow on a bottle. Messing with dimensions and positioning in unusual ways will make it harder to get a predictable resonance without other unwanted effects.

 

[kostya]

I think it will interfere if the ports aren't on the same face of the cabinet, you will get cancellation that corresponds to the distance between them. In the case of this speaker they might be using it as a sort of cardioid effect? Hard to say.

Hmm, I had not thought of that.

Probably not, ports deal with low frequencies only (ideally) and soundstage is primarily caused by higher frequencies.

This is true, but I have found (in my designs at least) that a rear firing port/woofer gives the effect of a fuller room. Perhaps soundstage would not be the proper term for me to use.

My advice is don't try for an exotic port unless you have a specific reason. They basically work by resonating like when you blow on a bottle. Messing with dimensions and positioning in unusual ways will make it harder to get a predictable resonance without other unwanted effects.

I will most defiantly not be trying this anytime soon haha.

 

[kemmler3D]

a rear firing port/woofer gives the effect of a fuller room.

Close to the wall you'll probably get a little more beneficial reinforcement so that makes sense. However, you can do this and more using EQ. Again, I'm far from an expert on this but I think you'll reduce this effect somewhat with front-and-back ports.

If you look around on DIYAudio.com you'll probably see a variety of interesting port designs. If you are interested in improving on the standard flared tube I might browse some of those threads, often there are measurements that can show you the actual effects of different experiments.

 

[kostya]

If you look around on DIYAudio.com you'll probably see a variety of interesting port designs. If you are interested in improving on the standard flared tube I might browse some of those threads, often there are measurements that can show you the actual effects of different experiments.

I am mostly interested in understanding why TAD decided on a design like this. The speaker has received outstanding reviews, so I was interested in the design theory of a dual slot port like they use here. That being said I will absolutely be browsing through DIYaudio before designing my next build. I have definitely reached the point where an improved port design is a good next step. I have read quite a bit from DIYaudio, but never saw a thread about the TAD port specifically. Maybe I missed one.

 

[DVDdoug]

I don't know but it's probably not that important. And copying the exact design won't work unless you're using the exact-same woofer and the same cabinet volume.

The cabinet looks "smallish" so it might be a way to fit the port into it. There are lots of trade-offs & design decisions that go-onto speaker design and manufacturers tend to tout those decisions as some kind of feature or advantage and they often make up cool sounding names.

Typically, speaker design software* will help you optimize the port by recommending a port diameter and length, assuming a cylindrical port (a pipe). You can change the shape and if you maintain the opening area and volume and it should work (about) the same. Sometimes a flared port is used to minimize turbulence noise and I don't know how that affects the "calculations'. When I built my subwoofer I used two smaller-diameter pipes instead of one larger one. It was awhile ago, but I think that's because I couldn't find a standard pipe with the "correct" inside diameter.



*If you are going to build a speaker, get some speaker design software. (WinISD is FREE.) You'll need the Theile-Small parameters for the woofer.

 

[kostya]

I don't know but it's probably not that important. And copying the exact design won't work unless you're using the exact-same woofer and the same cabinet volume.

The cabinet looks "smallish" so it might be a way to fit the port into it. There are lots of trade-offs & design decisions that go-onto speaker design and manufacturers tend to tout those decisions as some kind of feature or advantage and they often make up cool sounding names.

The name is very much a marketing strategy haha.

Typically, speaker design software* will help you optimize the port by recommending a port diameter and length, assuming a cylindrical port (a pipe). You can change the shape and if you maintain the opening area and volume and it should work (about) the same. Sometimes a flared port is used to minimize turbulence noise and I don't know how that affects the "calculations'. When I built my subwoofer I used two smaller-diameter pipes instead of one larger one. It was awhile ago, but I think that's because I couldn't find a standard pipe with the "correct" inside diameter.

I just assumed that it would be difficult to use a simple box software like WinISD, mostly because there are two ends of the port, connected at one spot to the inside of the enclosure. Surely that would effect the tuning of the port? I could be mistaken, but if each section was separated (the front slot having a barrier in the middle of the panel to separate if from the back port) the tuning would change quite drastically? The location of the opening to the inside of the box, relative to the actual slot ports on the side, should determine the length of the port, and therefore the tuning. Does one simply use the distance from the opening to the edge of the box?

*If you are going to build a speaker, get some speaker design software. (WinISD is FREE.) You'll need the Theile-Small parameters for the woofer.

I use the VituixCAD box designer. To be clear, I am not intending to use this specific port design, but I do want to understand the design theory.

 

[tmuikku]

Hi, main function for a port is the Helmholz resonance to extend system bandwidth by providing a low frequency boost. Trade-offs are the port has to fit somewhere and it can make unwanted noise on midrange. A pipe has resonances, and sound from inside the box can leak out through it. In addition the port could make sounds due to turbulence, and it would also compress with high output. So now the port output is not just low frequency boost but all kinds of unwanted noise on the midrange as well.

These trade-offs can be minimized by shaping and positioning the port suitably. From realestate perspective a slot port is nice idea, saves space and is easy to implement, but it has issues on the noise. In addition to these commercial speakers must look good, be be able to position against a wall, fit into a budget and all kinds of things dictating what the possible solution space is for any issue, like issues with a port. Look the port from perspective of the trade-offs and you'll see they solved some, while some remain, so it's mostly a marketing differentation.

In the end it's just a port, it should boosts lows without ruining mid frequency sound quality. When it works as it should it is very good for them, very good for clients, a problem solved. Rest is just marketing/business related necessity how to make it happen. On a diy build you'll face same issues because physics is the same, but have more freedom to solve them without business related constrains and having a well defined application so your port(s) might endup being something else, case by case.

Important thing is to pay attention to trade-offs and deal with them so that trade-offs aren't worse than the main function, and ideally trade-offs pushed as far out as possible so that they reveal themselves only when the system is pushed to it's very limits.