DIY sub for Klipschorn based HT (and music) - Tuba HT - build done (except for finish)!

[DrWho]

I see you don't really have any experience with quarter wave folded horns and are just kind of making things up as you go along. These have been measured and tested and there are no crazy ripples that you speak of.

You might want to do some research before you make uneducated claims like that...

In fact the folds act as 4th order filters, and you get far lower THD from a folded horn like this than you do with a direct radiator.

The system linearity is NOT improved by folds. Don't let the THD confuse you on this...it's merely demonstrating one of the shortcomings to THD measurement. If you want to see the system non-linearity, then bust out the IMD...

You refer to these as 'undersized horns'. Do you think the tapped horns are doing full wavelength? They're not, and it's not necessary to have a fullsize horn.

Anytime the mouth is not large enough to match the impedance of the horn to the air, then the horn is undersized. Tapped horns are not undersized because they are "tapping" the transfer to make it impedance matched. I far prefer the sound of a properly matched (full sized) horn to the sound of a ringing folded undersized horn.

You also mention transients, however what I think you're referring to is the delay incurred by the length of the horn path

Nope. Propogation delay was measured and accounted for. Try again.

Let's make this more interesting....here's BFM's marketing plot on the Tuba24:

And then here's measured over at ProSoundWeb:

See what I mean by marketing hype? All of BFM's horns and plots behave the same way. The fact that you don't see it with an in-room response is rather meaningless. The artifacts from the ringing will still be there.

I'm really not going to comment further on BFM's designs unless he shows up to defend them, so those that are wowed by them, by all means keep on being wowed.

[nyt]

In fact the folds act as 4th order filters, and you get far lower THD from a folded horn like this than you do with a direct radiator.

The system linearity is NOT improved by folds. Don't let the THD confuse you on this...it's merely demonstrating one of the shortcomings to THD measurement. If you want to see the system non-linearity, then bust out the IMD...

I wasn't confusing them, just adding. You get fairly flat response with lower THD than direct radiators is all I was getting at. The response of the THT is in fact fairly linear, and moreso the wider you build one.

I actually see where your confusion is coming from. I will clarify below.

Let's make this more interesting....here's BFM's marketing plot on the Tuba24:

The Tuba 24 is NOT the same as a 24" wide THT, and has not been discussed once in this thread. It is a MUCH smaller sub designed for DJs.

And then here's measured over at ProSoundWeb:

See what I mean by marketing hype? All of BFM's horns and plots behave the same way. The fact that you don't see it with an in-room response is rather meaningless. The artifacts from the ringing will still be there.

I'm really not going to comment further on BFM's designs unless he shows up to defend them, so those that are wowed by them, by all means keep on being wowed.

That is a measurement of a Titan 48, a completely different box than the one you named earlier, and also, not a THT

I don't have any of the waterfalls I took anymore, but I can assure you, there is no extra ringing from a horn compared to the direct radiators I previously measured in the same positions. I'm not going to defend BFM's marketing, which he has recanted some of the ridiculous items such as extension to 2hz in room. However, when you post nonsense and throw up charts from two different subwoofers other than the one we're discussing, I will post corrections and real graphs. You're not helping anyone by posting nonsense.

Here is a 24" THT outdoor ground plane measurement with THD plotted as well. The notch at 85hz is a measurement artifact as per the taker of these measurements, which he was getting with any sub he measured. He did these in his driveway and apparently was getting a reflection off of something. Funny, it looks just like the graph that BFM posts for the THT? (included below). It's trivial to EQ these flat, especially after room gain raises up the bottom end. I believe the in room response measurements I took and posted previously show this.

THT outdoor ground plane and THD.

from BFM's page:

Just incase you're still confused, this is a Tuba 24 (16x24x24):

This is a Titan 48 (48x24x24):

This is a THT (32x36x36):

[psg]

What driver goes into the Tuba HT and what impedance does it have in the enclosure?

I believe the SPUDs are 2 ohms and many people but a very inexpensive Behringer EP2000 (2x 1000W into2 ohms) to drive them.

(Those THT are HUGE. I just took a tape measure in the room and reliased that the extra width makes look much gigger than a La Scala (which I was picturing for size), and then I remebered how big my La Scala is when sitting in the middle of the room.)

[Billy joe]

Here's a tuba HT next to a La Scala. The tuba is 36x36x25

[nyt]

What driver goes into the Tuba HT and what impedance does it have in the enclosure?

I believe the SPUDs are 2 ohms and many people but a very inexpensive Behringer EP2000 (2x 1000W into2 ohms) to drive them.

(Those THT are HUGE. I just took a tape measure in the room and reliased that the extra width makes look much gigger than a La Scala (which I was picturing for size), and then I remebered how big my La Scala is when sitting in the middle of the room.)

Yes, they're large.

The dayton 15" DVC was the recommended driver, but they stopped being produced. I believe the Dayton 15 reference HF models almost identically in the enclosure and is now the recommended driver.

An impedance graph comes with the plans, but my plans are older and for the DVC driver. Average impedance is 5 ohms for that.

If you end up building a THT, don't use the cut sheets that come with the plans. They're designed to let you build a 24" THT with two sheets of ply, but you end up having to join pieces of wood for the folds inside.

[psg]

So... I figure out how to optimize cuts myself but the plans are complete?

5 ohms is easier to drive than 2 ohms, I suppose...

Thanks for all the help! It''s very much appreciated!

[psg]

Here's a tuba HT next to a La Scala. The tuba is 36x36x25

Yeah, a La Scala is really only 2x2x3 rather than 2x3x3 for a 24 inch Tuba; already much bigger than a La Scala and that's not the 30-inch yet.

[nyt]

Yep. The cuts are pretty easy to setup. The cuts from the cut sheet are also sized larger that necessary, designed for cutting to fit. As you go through the plans, it tells you how to set each piece. Due to difference in wood thickness, you have to basically cut things to size. I had a lot of scrap wood since I made wide ones, and screwed up some cuts. It took 3-4 pieces of ply each. It's a fairly easy build, just requires lots of clamps, some squares, circular saw, and either a router or jigsaw. A nailer will also speed things up considerably, though it may be easier to set/glue pieces that are pre-drilled. Clamping a piece in place while it slides around in the glue can be a pain. I suggest picking up some nitrile or latex gloves. It sucks getting PL on your hands. Also, wear clothes you don't care about, since they will get ruined. If you escape without getting any PL on you, I'll be impressed.

As for the instructions, they're pretty easy to follow, and clear. He'll send you a sketch-up of it too that you can examine if you have any questions.

So... I figure out how to optimize cuts myself but the plans are complete?

5 ohms is easier to drive than 2 ohms, I suppose...

Thanks for all the help! It''s very much appreciated!

[CECAA850]

Why do you suppose they want you to use PL instead of wood glue?

[psg]

Thanks! So this would be the driver to order?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-468

(What's PL?)

[CECAA850]

(What's PL?)

Polyurethane construction adhesive ,such as PL Premium. It's recomended in the plans.

[nyt]

Thanks! So this would be the driver to order?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-468

I believe so. Get the plans, it's like $5 and confirm.

It's recommended because it expands as it dries filling the gaps better. This is what holds the sub together. The screws and the nails are just to keep things together while the glue dries.

You can get it at lowes or home depot.

http://www.amazon.com/Henkel-828472-Polyurethane-Construction-Adhesive/dp/B0002YV81Y/ref=sr_1_2?s=hi&ie=UTF8&qid=1284867340&sr=1-2

[jason str]

PL is a great product for construction projects, dries fairly quick and very strong.

Lots of good driver options out there, Bill says anything within 10% of the specs can be used but its probably best to ask if theres any question.

These are some of the options i know of.

Dayton RSS390HF-4

Dayton DCS380-4 & if i recall somebody had good results with a 385 model but don't quote me on this.

12" version = Eminence LAB 12

More options are available on the forum if needed.

[psg]

Thanks guys... You rock!

[psg]

So...

One Tuba HT for now. I can always build SPUD risers later. It's not like they would cost a fortune to build. If I finish the build before the class is over, I'll either build a second smaller one, and start building the in-wall equipment rack or on-wall CD storage unit.

Should I document the build progress with pictures in this thread?

[nyt]

of course, pics are great =]

if you need any help along the way feel free to post

[CECAA850]

Should I document the build progress with pictures in this thread?

Uhh chaaaaaa

[laager]

Should I document the build progress with pictures in this thread?

Is the Pope Catholic?

[tragusa3]

You may want to reconsider mixing different horn subs. I wonder if the difference in time delay would present an issue? There are processors that could compensate for this ($).

[psg]

You may want to reconsider mixing different horn subs. I wonder if the difference in time delay would present an issue? There are processors that could compensate for this ($).

I don't think I'd mix 'em. I just meant that I could switch to SPUDs at a later date if the THT don't work out (due to placement issues for example). Chances are slim that that will happen.

Thanks all! I'll post here along the build process; it's nice to know that there are people here who I can ask questions to. A nice family here indeed!