Midbass horn

[tinitus]

something very cheap plastic with poorly alligned screw mount
bought some a few years ago

I'm thinking it might be a mid/tweet for a 3way with 12" in vented BR
crossed around 500hz
but not sure about it
though it seems like it might fit nicely into a monitor box
and look like a cheating 2way 😛
one problem, a woofer cost money 😀

 

[tinitus]

Very cool! Which horn is that?

hey, I'm reminded, you probably don't know this, but the shown 'tweeter' is actually a very small TB fullrange, and the all time famous and favourite mid driver for Synergy horn 🙄

I'm just teasing showing as a tweeter instead 😀

 

[tomlang]

That horn above is a Pyle PH714, amazon recently had them on sale for $9 each. I bought two to play with.

 

[unaHm]

something very cheap plastic with poorly alligned screw mount
bought some a few years ago

I'm thinking it might be a mid/tweet for a 3way with 12" in vented BR
crossed around 500hz
but not sure about it
though it seems like it might fit nicely into a monitor box
and look like a cheating 2way 😛
one problem, a woofer cost money 😀

It reminds me a little of Patrick Bateman's Le Cleac'h horn that he made with hemp rope and gorilla glue 🙂

 

[tinitus]

Iwata style

actually I'm thinking about turning it 90degr, and use it 'upright'

 

[unaHm]

That sounds good! 🙂

The wide/flat sides look like they would work well for mounting the mids, with a little bit of hacking with a Dremel or something!

So is it really that easy?

 

[weltersys]

The wide/flat sides look like they would work well for mounting the mids, with a little bit of hacking with a Dremel or something!

So is it really that easy?

Yes, it is quite easy to slap together devices and get a frequency response +/- 12 dB (a 24 dB variation) in a narrow range with response that varies by 20 dB over the width of a couch at average listening distances.

If you want smooth, wide band frequency response and uniform dispersion, more attention to detail is required 🙂.

 

[tinitus]

So is it really that easy?

ehh, noo ... it is never easy 🙂
but I have all the parts
and haven't cost much either anyway

I'm only considering if I want to waste time and effort ... and I guess not 😉

might do a small midhorn instead 😀

midbass ? ... I guess not quite enough for that

imo ... I think you should just put the Alpha-8 in a conical horn, like maybe a small Altec A7 style
tweeter horn goes on top of it, and ought to be perfectly fine

 

[unaHm]

The Altec A7 route is certainly a good one, and I think I'll try them out at some point!

I'm going to stick with the Synergy design for now. I'll start drawing out the pieces on the bits of MDF that I need to 'butcher', and re-do the ports so that they look more like Bill Waslo's CoSyne ports (the 'rounded rectangle' shape). I had to look at it a number of times before the penny dropped about really tucking the ports into the corners.

I suppose my worry has been about impeding the flow of air too much, but if others have done it, I have no idea why I should be worrying about it!

Maybe it's because sleeping is difficult at the moment 😉

 

[unaHm]

The most recent 'project' I'd set myself was to deal with the rectangular ports.

I noticed that the shape is a rounded rectangle, rather than with 90 degree corners.

So, I started to consider the difference in area between a circle and square of the same 'diameter' (e.g. a square of 2cmx2cm = a circle with a diameter of 2cm). Because a circle has a smaller area than a square in this case, we have to make the rectangle longer.

Here's how I thought of doing this in a spreadsheet:

1. Enter length of rectangle
2. Enter width of rectangle
3. Spreadsheet calculates an area of a square, based on width
4. Spreadsheet calculates circle radius based on the 'short side' of the rectangle (in my case, the width)
5. Spreadsheet calculates area of the circle
6. Spreadsheet works out a multiplier
7. Spreadsheet multiplies the length of the original square rectangle to get the length of the rounded rectangle.

Here's an example:

10	Rectangle length
1	Rectangle width
10	Rectangle area	1	Square of width
0.5	Circle radius
0.78539816339745	Circle area
0.21460183660255	Area difference between circle and square
1.00214601836603	Multiplier of square to circle
10.0214601836603	Length of rounded rectangle

I've not actually drawn out anything based on this, but it seems to be OK. I suppose this is purely mathematical, and working out the length based on a router bit's size and shape would be different.

 

[unaHm]

Sorry for the lack of updates recently!

I've finally found the enclosure Tony Seaford had made for Bill's Synergy horn:

DIY Synergy/Unity spreadsheet

Given that the horn I'm making is slightly shorter (in terms of front to back depth), yet all of the other dimensions are the same, I could use this.

I'm not sure how I can really make a 32 litre box for the Synergy horn, as the closest I've had that makes sense is 61!

I suppose I'll have to taper the top panel (at least) to reduce the volume.

 

[unaHm]

So after a random couple of days, yesterday I tried something out...I compared the output of the compression driver to that of the one in the Synergy horn.

There was a noticeable difference in that the compression driver didn't load well in it. So, I think I'll just focus on the midbass horn for now as a single entity.

I've started a mockup of the simplest horn we'd discussed a long time ago(!), and it's definitely shorter than the original I did. It's one of those things where I had to see it to believe it again 🙂

 

[unaHm]

Sorry, I mean the original horn I had the compression drivers loaded in, compared to the Synergy.

 

[unaHm]

Ok, here's the mock-up, lumped together on top of the T18, and the Pyle tweeter.

In terms of arrangement, I suppose it would make the most sense to have the tweeter at ear-level, and then the midbass horn above it, angled down slightly to the listening position.

 

[tomlang]

Una, how much power is that plate amp on the T18 and how much do you recommend?

 

[unaHm]

I'm not sure, but on Bill Fitzmaurice's website, the builders tend to use the BASH plate amps, and from one thread I've found:

Bash 300S 300W Digital Subwoofer Amplifier | 300-750

I actually have two of these T18s wired into a receiver (so I'm not using plate amps), and the DSP in that has been configured for the pass bands for each horn. I was using a computer, but it made noise 🙂

 

[unaHm]

I'm hopefully going to start cutting the pieces of the horns this week, but before I do, I had a thought about possibly simplifying the design further.

I'm trying to understand how to use HornResp to export a 'rectangular' horn, where the top and bottom panels are a single, flat piece. This would mean that only the sides have the two-stage flare.

After reading, I'm still confused as to how the program actually processes this. It's probably simpler than I think, but couldn't find anything definitive.

So in short, how do I do it? 🙂

 

[weltersys]

I'm trying to understand how to use HornResp to export a 'rectangular' horn, where the top and bottom panels are a single, flat piece. This would mean that only the sides have the two-stage flare.

The "Par" (rather than "Con") is equivalent to the expansion of straight side horn sections with parallel top and bottom pieces.

If the top and bottom are angled, but single piece, the horn is somewhere in between, close enough to "Con" for rock and roll.

Measure the cross sectional area of the horn at various distance from the throat and mess with the horn section lengths and area in Hornresp until they agree with what you built, or what you can build.

Or just copy a known working design...

 

[unaHm]

Thanks for your response Art! I'll give that a try 🙂

Thanks for your patience too...sorry that this thread is dragging along at the moment. There certainly are more intellectual conversations in progress!

 

[unaHm]

I've glued up my first attempt in MDF this weekend, and I've done a terrible job of it! The flare section of the horn was impossible to do alone (I had to apply glue, and then with the help of my Dad tack the pieces together).

It's certainly easier to use cardboard!

Still, is duct taping the pieces together while the glue sets the only sane option?

After this I'm somewhat tempted to make a mold, and use Patrick Bateman's 'hemp rope and Gorilla Glue' method, or Inlow's lazy susan clay mold procedure.