# How to design a folded Voigt Pipe???

#### djn

I have a pair of full range drivers and want to test them in vented cabs and folded Voight Pipes but don't know how to size the pipes.

#### Scottmoose

Depends on the drive units. Some are suitable, some are not. It's 'Voigt' BTW.

Theory here, with alignment tables (assuming an Fb = Fs tuning) and Excel based calculator to go with it: Transmission Line Theory

Hornrsp is the most popular easily available modelling software at present for QW designs. By and large, a folded pipe is no different to an unfolded in design terms. It just happens to be folded. There can be some subtle differences but for your purposes unlikely to affect matters.

#### GM

Not really, it's better than nothing, but not by much, whereas MJK's Classic TL design routine is the 'real deal'. IIRC it use to be online at your linked site, but for whatever reason it was left out of the all new site.

GM

edit: That said, this will calculate a real Voigt pipe, i.e. a [tapered] TL with no separate vent, though of course one can be added to tune it lower if desired [ML-TQWT] whereas your link is a horn tapered ML-TQWT [aka ML-horn], so either make a Voigt pipe tuned to Fs or one tuned up around 1.4-1.56x Fs and vent to whatever works best overall in room.

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#### djn

I read through a lot of that material on the Transmission Line Theory link but quickly got lost in the sauce. I also searched for MJKs calculator to no avail.

There there a difference as to the amount of bass boost a Voigt Pipe gives and a Transmission Line gives?

#### GM

The links are at the bottom of the web page Scott linked to.

There is no MJK calculator per se, it's a WORD? doc with tables to manually work through it a step at a time to get a design and later on a member created an Excel WS to fill in the
blanks. It's been so long since it came out I can't remember if you actually need the Tables to use it and don't have Office loaded to check.

Traditionally; a TL speaker [damped 1/4 WL pipe] is basically a ~ IB response in a smaller bulk whereas the ML-horn is usually a short parabolic flared BLH to 'pump up' [3-6 dB] the mid bass to somewhat offset baffle step loss and vented to 'stretch' it a bit to a rolled off to whatever tuning bends best overall in room.

How much dB boost will depend on the driver's specs, how big the cab, vent.

GM

1 user

#### Scottmoose

No, you don't need the tables; you just put in the driver details & desired taper ratio & it calculates the physical & acoustical lengths, throat & terminus areas using the formulas in Martin's alignment tables (assumes an Fp = Fs tuning & a uniform of 0.5lbs ft^3 stuffing density of dacron).

#### djn

OK Scott, I input all the required data but don't know what to do with it. I don't know how turn this into a cabinet. Any Help.

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#### cogitech

Paid Member
Is there a similar simplified spreadsheet for designing a mass loaded Voigt? I understand that the method is to tune the tapered Voigt tube/pipe up to about 1.1-1.2 times Fs and then use the port (line restriction) for final tuning, but what tool can I use to tune the port? Will a simple bass reflex port tuning tool such as WinISD work?

#### cogitech

Paid Member
OK Scott, I input all the required data but don't know what to do with it. I don't know how turn this into a cabinet. Any Help.

I've been playing with it, too. To get a true Voigt, you are going to need to change that taper to something much greater. I have used the spreadsheet to reverse engineer a known ML Voigt design and the taper factor is 6.75, for example.

Once you get your taper factor in there, it'll tell you the surface area of the closed and open ends of the pipe, and the length. The actual dimensions you choose will be up to you, but you need to get as close to the open area and closed area as possible.

Good luck folding it, though!!!

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#### djn

Ok, after reading all I can find on the subject and realizing that I have sheets of MDF and a real good brad Nailer I'll build 1 folded voigt pipe from the link in the 3rd post, 1 transmission line, and 1 vented cabinet and start testing. More to follow.

#### grindstone

Cool, way to go D. Did you decide on a field voltage/Q or is part of the fun turning that knob, too?

#### djn

I'm running them on open baffles to break them I'm and I have the power on 1 which gives a Qts of .8. For the transmission line I'll set it at 2 or 3 and for vented box I'll set it at 4. Yes, that's the fun part.

#### djn

So bumbed out. My Craftsman jigsaw I bought in 1981 finally died. The motor brushes are shot and no one makes replacements for them.

#### drewan

38yrs? not bad, not bad at all, my electric planer which really has done some serious work is a mere 32 years old

#### planet10

Paid Member
Not really, it's better than nothing, but not by much

Just don’t use it. You willbuild a big box & likely have mediocre performance.

It should also be noted tht to get smooth bass you are best to mass load the Voigt..

What drivers? Maybe we can oint you at existing examples for those drivers.

dave

#### djn

I don't know what Mass Loaded means. I appreciate any help you can help with. I'm using full range field coil 10" drivers. The below chart shows how the T/S changes with different voltages.

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#### GM

No, you don't need the tables; you just put in the driver details & desired taper ratio & it calculates the physical & acoustical lengths, throat & terminus areas using the formulas in Martin's alignment tables (assumes an Fp = Fs tuning & a uniform of 0.5lbs ft^3 stuffing density of dacron).

Thanks! Input the basics into HR and use its Wizard to add damping, pass band filters and modify to 'taste' if desired using its real time sliders.

GM

#### GM

I don't know what Mass Loaded means. I appreciate any help you can help with. I'm using full range field coil 10" drivers. The below chart shows how the T/S changes with different voltages.

It's MJK's [correct] way to define a reflex [pipe] vent, so in theory use FC-4/vented box setting.

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#### djn

Ok, GM. my daughter and I built a pair of Bob Brines folded voigt pipe with 40-1354 drivers for her dorm room. Those had a vent tube instead of just am open mouth.....so those where mass loaded?