Tapped Horn for Dummies

[Patrick Bateman]

Before I post my design I gotta warn ya'.

You guys have seen some of the crazy outrageous I've done - I'm a big fan of crazy waveguide projects that take ages to finish.

But this sub project is S-I-M-P-L-E.

Yes, I could have made it flatter. Yes, I could have made it play lower. But to do that, I would have made it a LOT more difficult to build. And I need at least three of these, and I really don't want to spend my entire Summer building subwoofers.

So...

It's not perfect.

But IMHO, you're not going to find a tapped horn that's easier to build, and you sure as hell aren't going to find a subwoofer that can be built for $50 that can outperform this monster.

Yes, FIFTY BUCKS kids. The driver is $25, the sonotube will set you back about ten bucks, throw in another $15 for wire, wood, carpet and terminals.

FIFTY BUCKS.

IF you want to make it better, go right ahead. Increasing the taper will flatten the response, but will also raise the F3 and make it MUCH harder to build. You can double the power handling by adding a second woofer, but then you'll have to tweak the resistor to lower the QTS of the system.

Without further ado, I present The Tapped Horn for Dummies

[PeteMcK]

Patrick, I tried this a few years ago with 6" plastic pipe & 4" drivers, I put a 'Karlson slot' at the 'output' end. I made the pipes 1.2m high in the hope of getting down to 40Hz.
Now I have a bit more knowledge & a 2m length of 12"pipe, I was thinking of trying again with better drivers.
I'm interested to understand why you see this as a 'tapped horn' rather than a transmission line?

Cheers,
Pete McK

[GM]

Originally posted by Patrick Bateman

There isn't even a taper! Because it's efficiency is lower than most tapped horns (about 96db) you don't get a lot of ripple.

This is a tapped PIPE (or TL if you prefer) as I've suggested and shown a few designs of on the tapped horn thread (see links for one of them) and I assume since you put two drivers in one hole that it's an isobaric TP.

As for the ripple, the ones I did sure simmed a lot of HF 'hash', though never having built one I don't know how bad it is in reality.

Note too that Al (pinkmouse) built one I did for him and it performed/measured very poorly, though there seemed to be some question as to how airtight it was, so he was going to get back to us, but that was months ago and he's been MIA on the thread ever since.............

http://www.diyaudio.com/forums/showt...97#post1391597
http://www.diyaudio.com/forums/showt...98#post1391598

GM

[Patrick Bateman]

There's a glitch in my post. I went back and forth between using one woofer and two. I'm using ONE woofer for the project.

The MCM woofer is designed for such a tiny box - when you use a single woofer there's a lot of ripple in the response due to this.

The resistor flattens out the response quite a bit by raising the QTS of the woofer. (A higher QTS requires a bigger box or horn.)

[Patrick Bateman]

Originally posted by GM


This is a tapped PIPE (or TL if you prefer) as I've suggested and shown a few designs of on the tapped horn thread (see links for one of them) and I assume since you put two drivers in one hole that it's an isobaric TP.

As for the ripple, the ones I did sure simmed a lot of HF 'hash', though never having built one I don't know how bad it is in reality.

Note too that Al (pinkmouse) built one I did for him and it performed/measured very poorly, though there seemed to be some question as to how airtight it was, so he was going to get back to us, but that was months ago and he's been MIA on the thread ever since.............

http://www.diyaudio.com/forums/showt...97#post1391597
http://www.diyaudio.com/forums/showt...98#post1391598

GM

Thanks for the heads up. I was going to build three right off the bat; maybe I'll build one and measure it before I commit to a set.

[Patrick Bateman]

Originally posted by GM


This is a tapped PIPE (or TL if you prefer) as I've suggested and shown a few designs of on the tapped horn thread (see links for one of them) and I assume since you put two drivers in one hole that it's an isobaric TP.

As for the ripple, the ones I did sure simmed a lot of HF 'hash', though never having built one I don't know how bad it is in reality.

Note too that Al (pinkmouse) built one I did for him and it performed/measured very poorly, though there seemed to be some question as to how airtight it was, so he was going to get back to us, but that was months ago and he's been MIA on the thread ever since.............

http://www.diyaudio.com/forums/showt...97#post1391597
http://www.diyaudio.com/forums/showt...98#post1391598

GM

Well I don't want to build junk, so I did a bit of redesigning. I still want to keep it simple, but integrated a taper by putting the center panel a bit off center. This basically creates two sides of the pipe, one that's double the size of the other.

Voila! Two to one taper.

I also found that Home Depot and Lowes have Sonotubes that are 9.5" in diameter. That's what I'm using instead of ten inch. The reduction in diameter flattens out the response further, since these MCM woofers really want a small box.

Parameters attached.

[Patrick Bateman]

frequency response

[GM]

Originally posted by Patrick Bateman

The resistor flattens out the response quite a bit by raising the QTS of the woofer. (A higher QTS requires a bigger box or horn.)

Yeah, there's 'no replacement for displacement' down low and it takes a minimum box size for a given ~flat gain BW, so either Vas or Qts must go up to 'fill' it if you want it ~flat, with increasing the latter being the easiest for the DIYer.

GM

[GM]

Originally posted by Patrick Bateman

Thanks for the heads up.

Well I don't want to build junk, so I did a bit of redesigning. I still want to keep it simple, but integrated a taper by putting the center panel a bit off center. This basically creates two sides of the pipe, one that's double the size of the other.

Voila! Two to one taper.

You're welcome!

I didn't mean to scare you off as I don't see anything fundamentally wrong with the TP concept and apparently the math doesn't either according to Hornresp, just that Al's build highlights how sensitive to variables any tapped pipe/horn build can be and unfortunately he hasn't let us know where his might have gone awry.

I'm still probably up to at least a year away before I'll be set up to build/measure again, so was hoping someone in the meantime would give these a shot since they are so cheap/simple to build.

If I'm understanding you, the baffle is just made narrower and offset to create a stepped pipe rather than the tapered one simmed, so it will be interesting to see how it measures Vs the sim.

Anyway, thanks for sharing as so far outside the few on the TH thread that have taken the 'plunge', folks I've suggested THs to have proven way too intimidated by such simple box builds once one or more internal angled boards are added.

Maybe if we call them shelf braces instead..............

GM

[gedlee]

Originally posted by Patrick Bateman
frequency response

John

That just looks like a badly tuned bandpass. Why not just build a bandpass? They have worked well for me.