Which TQWT model?

[Niek]

Hello.!


I have a small question about a TQWT cabinet.

There are roughly two types of TQWT cabinets.
Are there important, audible differences between these two examples?
In Hornresp I get (almost) the same outputs.

Thank you!

 

[Scottmoose]

They aren't different types -they're just different ways of folding, potentially with some vatiations for the driver & vent (where relevant) tap locations (offset) along the pipe / horn expansion. And there are plenty more than just that. Ideally, you design the pipe, then decide how to fold it, in such a way that it puts the driver & vent arrangements where you want them. There are or can be some other effects going on, but these are usually secondary to the basic pipe & tend to come in to more complex / advanced designs.

 

[nandappe]

Hornresp can simulate frequency graphs, but it cannot simulate the texture of the actual sound that is produced.
The only way to find out what kind of sound is to actually create it and compare it by listening to it.

 

[planet10]

These are different foldings of the same line.

The last actually is no fold.

dave

 

[Arthur Jackson]

@Niek I think of the two drawings you posted there will be very little difference.

 

[planet10]

The only really noticable change is that Z_d.

dave

 

[Niek]

They aren't different types -they're just different ways of folding.

Yes. I thought maybe there are some (minor) differences because the left one is more close too the original Voigt pipe?

 

[Niek]

The only way to find out what kind of sound is to actually create it and compare it by listening to it.

Yes. I have to make a dummy cabinet and measure what it does

 

[Niek]

These are different foldings of the same line.

The last actually is no fold.

dave

The top example is an interesting one. At the bottom there’s something interesting coming on to make the ‘pipe’ longer.

 

[Niek]

@Niek I think of the two drawings you posted there will be very little difference.

Okay. Hornresp shows that indeed.

 

[Niek]

The only really noticable change is that Zd.

What’s that last part you mention? Zd

 

[Scottmoose]

Driver offset / tap location.

As noted, they are just different methods of folding. Unless you are deliberately trying to use secondary effects & account for them in the design, you design your pipe, then decide how to fold it up in such a way as to put the driver and vent where you want them. Or, if you want a rectilinear cabinet, check first to see whether a simple MLTL will do the job as well or better. 😉

 

[LeifB60]

I think MLTL is very good construction.
Why make it harder than it needs to be?
The result speaks for itself.

 

[Niek]

As noted, they are just different methods of folding. Unless you are deliberately trying to use secondary effects & account for them in the design, you design your pipe, then decide how to fold it up in such a way as to put the driver and vent where you want them.

yes, but that’s a bit unclear too me because I never used Hornresp befor, and build a TQWT 😉

Here i have two examples of folding the pipe like the example (left/right)
At one example (OD1. Driver between section 2-3) you see a better response around 100-200Hz.

You see a response in a 1.0 x Pi configuration. The peak around 50Hz is because I want less energy from 60-100Hz because of roommodes. I have peaks around 63/71/92Hz.

 

[Scottmoose]

Well, my first question would be: is the basic pipe geometry the same? By that, 'we' (well, I, anyway) mean, and ignoring folds etc., which are primarily a construction, not acoustic issue:

• Is length equal?
• Is the throat area (the pointy bit 😉 ) of equal cross section?
• Is the terminus area (the wide bit?) of equal cross section?
• Is any mass-loading vent (the exit area or pipe of resticted size compared to the terminus area) of equal area and length?
• Is the driver offset (distance from the throat) equal?
• If a mass-loading vent is present, is it offset from the terminus, and if so, is the offset equal?
• Is the damping of identical type, and identically positioned?

The easiest way of checking these is simply to assume the pipe is not folded up, but just a tall triangular (more or less) box. That allows you to view the basics of the pipe geometry for what it is -when you're new to designing them, it tends to be easier this way. The above are the dominant acoustic features. When you fold a pipe up, usually, as I say, it's done for convenience, so 'whatever will put the driver and vent in the positions you want them to be in'. That's not to say that different folding schemes don't / can't affect things in themselves -they can. But except in extreme cases, or you introduce some other features in the process, it's usually a secondary effect that doesn't have a great deal of impact on tuning or the first couple of harmonics.

Hope that helps a bit!

 

[Niek]

is the basic pipe geometry the same?

In short: Yes. I changed OD-OD1. L12 is a few cm longer. (And Path length of course)
No major changes I think 🤷🏻‍♂️