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3 way tops (100hz and up)

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thepersonunknown View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Topic: 3 way tops (100hz and up)
    Posted: 29 March 2020 at 10:37pm

Hey Speakerplaners.

Long time no post. I’ve been out of the loop for a long time, but a year or so ago I started getting back in to PA stuff with a crew here in Madrid. We kinda winged it last year with a rig made up of bits and pieces we had laying round, but this year I’m going right back into the madness and will be building a new system.

 I’m using this as an excuse to build something I’ve been itching to have a crack at for years. A 3 way horn top from 100hz and up. For the mids ill be using some phase-plugged 10inch mid horns with their oem drivers which I scored of a fellow speakerplanner a long time ago and some beyma cd10fe comps on small horns from 3K and up. This will all run from 300ish hz and up, so I’m faced with the same old design problem that I’ve had turning over in my head for years. How to get a folded horn to sound good as high as possible with off the shelf parts and reasonably simple construction methods whilst still getting down low enough to meet hornloaded sub that will play down to bellow 40hz.

Now I know there will be a bunch of comments about how beefy drivers are these days and that I should just use a simple reflex design on the lows, and these people are probably right, but that’s not the point of what I’m doing here, so if that was going to be your comment, you might as well save your breath Tongue

 Here’s a rough sketch of what’s going to be the prototype (obviously ill only be protyping the low horn part as the rest is tried and tested)

 http://ibb.co/BwYPD75

No points for guessing that the folding scheme is based on the klipsch la scala, right down to the point that the first section of the horn expands in the horizontal plane (which is not shown in the sketch). I played about with many different folding schemes, but I like the one used in the la scala for a few of reaons:

1.    1:   When folding a horn, path length differences become apparent when the cross-section of the horn increases through a bend. I remember Tony ASS pointing this out to me years ago. The La scala folding reduces this effect in two ways:

a.       The expansion through the first section is horizontal, therefore not increasing the cross-section (path length differences) in the vertical plane through the bend.

b.      The horn is split in 2, thus decreasing the total cross-section and any path length differences for a given horn by 50%.

2.    2:  The la scala folding is very easy to build. Over the years I had toyed with the idea of Fk1 style phase plugs or Vdosc style waveguides to get the correct cross-section through the bend, but these methods are just way too much for your average diyer.

3.    3:  The la scala folding really only has one 90 degree bend apart from the offset(ish) driver loading.

4.    4:   This layout is known as one of the best sounding diyable midbass folded horns, designed for PA and loved by hifi freaks. There’s got to be something to it.

The next thing to think about was of course the driver. Most cabs of this type use a 15 inch driver, but I’m going in a slightly different direction. The clarity in the upper band is one of my main design objectives, and therefore I decided to use a 12 inch driver. After much searching I found this brute.

(Note, this specsheet was sent to me by DAS. It shows the specs for the early model 12-B, which are very close to the old B20)Link: https://dam.dasaudio.com/ficheros_sw/documentos/Technical/spec_sheets/COMPONENTS/HT_12B_00.pdf

The DAS B20: No longer in production, having been replaced with the 12-B which over the years has seen its specs downgraded from midbass horn monster to run of the mill 12 inch all-rounder. The B20 is easy to find here in Spain and I picked up 2 for this project with no difficulty for 90 euros each.

http://https://ibb.co/fxC24w2

http:// https://ibb.co/VtmR8Hg

As you may see from the specs, this driver is a brute of a 12; 4 inch voice coil, BL: 23.5, Qts: .188, Fs: 46 and 8mm peak to peak Xmas (with a 20mm Xlim up the sleave for when the brown stuff hits the fan). As a matter of fact, for what I was looking for, I only saw one driver that on paper would be better; the PD 123C001, I didn’t bother checking the price of that unit though. Lol

This driver should be able to control the column of air in the horn quite well, hopefully helping to negate some of the turbulence caused by the horn folding and still be as ‘fast’ as any 15 inch driver seeing as it is basically the motor from a big beefcake driver mated up to a small and lightish 12 inch cone. Also I’m not asking it to play all that low.

Also not shown in my sketch is my intention to mess about with ports in the protype. The horn starts to roll off at about 110hz, with a 3db down at about 100hz. hornresp says that an 80ish hz port tuning would work, but like I said, this is a question better answered with sawdust and not a great concern for me as my subs will reach 100hz.

I must add here that this design is oriented towards subs which have a wide bandwith and can meet tops at 100-110 hz whilst still playing low, namely, tapered horns. I plan on building Keystones personally. A fantastic design by Art, I recommend you check it out if you don’t know what I’m talking about. That said, these tops would also work very well with some good old reflex. Most scoops and BP6 type boxes however are going to have trouble reaching xover point required.

I’ll be building the prototype as soon as we get out of covid19 lockdown here in Madrid. I’ll take the measurements that I can (a smart for the delay settings etc), but I think the best comparison that could be made would be to compare it to some other cabs which do something similar (Martin H3, Turbosound TMS, etc) If anyone’s local to me and would like to get on board for an AB test, please give me a shout.

As you may have guessed, Ill y findings will be open source.

Cheers guys, Id love to hear your input, and its great to be back. Thumbs Up

Dave.

They keep telling me life is short, but its the longest thing ive ever done!!!
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thepersonunknown View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2020 at 10:39pm
P.S

Looks like the links for the pics of the drivers and horns havnt worked. Any suggestions for a good photo hosting site?  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2020 at 10:53pm
Wrong thread.

Edited by Conanski - 29 March 2020 at 10:55pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2020 at 10:55pm
Imgbb is a good way of posting images, once uploaded copy/paste the bb codes to your post
“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2020 at 11:06pm
https://ibb.co/fxC24w2


https://ibb.co/VtmR8Hg

Lets see if this works

@earplug. If you can see these pics, you might recognise the 10inch hornsWink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2020 at 12:50pm
So, and forgive my crassness, an Xtro mid and HF, but a W bin kick? Why not an Xtro Kick section? Or a martin H3T type kick?

Why not have the 10" Plugged horn and HF in a box, and a separate kick section? Almost stack the 10"+HF on top of a HD15?

I think it all depends at which frequencies you have set as target X-over points?

I am not seeing the advantage of a 12" over a 15" for the pass band you are aiming for.

Please feel free to flame me back with your reasoning, as they have gone over my simple head, and I can't see the advantages for a 12" W bin Vs 15" HD15 ish solution.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2020 at 3:41pm
Originally posted by MattStolton MattStolton wrote:

So, and forgive my crassness, an Xtro mid and HF, but a W bin kick? Why not an Xtro Kick section? Or a martin H3T type kick?

Why not have the 10" Plugged horn and HF in a box, and a separate kick section? Almost stack the 10"+HF on top of a HD15?

I think it all depends at which frequencies you have set as target X-over points?

I am not seeing the advantage of a 12" over a 15" for the pass band you are aiming for.

Please feel free to flame me back with your reasoning, as they have gone over my simple head, and I can't see the advantages for a 12" W bin Vs 15" HD15 ish solution.

Hey. 

First point, its not a w bin. Like I said, its based more on a la scala horn, but flipped on its side. W bins typicaly have more than one fold and normally of more than 90 degrees. I think your thinking of this in the wrong way Matt. 

This is more of a low mid horn than a 'kick bin', hence the 12inch driver which if you look at the specs, is basicly a midrange driver but with a massive coil and resonable xmas. think really big MT12 because this is more the band im aiming to cover. The bandwith from 100hz and up is what I need, anything below I can get with porting is nice, but only an afterthought. I would have in fact made it straight if I could as this would get me the best clarity throught the mid, but im not up for boxes 1.2 meters deep.

This need for the straightest posible hornpath with the bend as minimal and as early as possible is what drives the somewhat inefficient use of space in the design. 

You could if you wish put the mids and highs in another box, but the total size would be bigger as you wouldnt be able fit the comp and its horn into the hormouth of the 10 as the phase plug is in the way.

The frequency im aiming for is 100-300 (or as close as I can get) on the lows, 300-3k in the mids and 3k+ on the highs. I was looking at doing something more like a cubo kick inicialy, but after messing with the design, i thought i would have a better chance of getting more clarity by going full FLH. I had the same problems when I checked out BPH alignments. there was no way they were going to play with such a big front chamber, at least not with the drivers i can get. 

Im sure at this point someone will say that i could use a 15 on a port assisted straight horn, and that is probably true, but I really just wanted to see if I could pull this off and hornload the driver right down to the xover frequency. Folding a horn and getting good responce up to 300hz is something ive not seen much at all, and seeing as im going to protype anyway, i would prefer to aim high. if its a complete flop i can still fall back on the straight horn.

The FLH way of doing this seems to be a way forward, as seen on the martin linearays and other cabs. Im not sure whats going on inside the H3. Have you seen inside one? 

Cheers,

P.S. Matt, one of the things that im banking on most is reducing pathlength differences and the problems this will cause in the higher frequencies. when i was playing about with hd style folding, to get the pathlengths anywhere near even, you needed to fill the front chamber with some crazy shaped phase plug (FK1 style) which i cant realisticly make. And at the end of the day, when you fill the front chamber whilst keeping a constant expansion rate, all you have done is create a more complex FLH.


Edited by thepersonunknown - 30 March 2020 at 3:51pm
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Peter Jan View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Peter Jan Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2020 at 6:33pm
Given you can find those DAS 12" speakers fairly easy and thinking size and simplicity of construction, I would look into dual 12" BR as another option.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2020 at 7:39pm
yea as a fallback i could do some kinda v baffel reflex with the 12s. Im keen to try the folded horn though. If the layout works then it will be an interesting direction to keep working on. its a challenge thats been bugging me for years

PS. I just want to point this out, twin relfex is clearly an easier option. I have tones of spare amp power (the lows will be running of a crown ma2400) the drivers are cheap and easy to get, the design is piss easy.....

The thing is, i think its kinda boring as a project. I built my first relex box for a car sub when i was like 14, and ive done it i dont know how many times since. I want to have a crack at something that hasnt been done much.


Edited by thepersonunknown - 30 March 2020 at 7:47pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2020 at 9:08pm
Originally posted by thepersonunknown thepersonunknown wrote:


The thing is, i think its kinda boring as a project. I built my first relex box for a car sub when i was like 14, and ive done it i dont know how many times since. I want to have a crack at something that hasnt been done much.

Fair enough, in which case carry on!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote thepersonunknown Quote  Post ReplyReply Direct Link To This Post Posted: 30 March 2020 at 10:05pm
@Matt: whats the folding scheme on the H3? 

like I said, ive never seen inside one, but im trying to emulate that sound, although if I remember correctly, the H3 crosses over at like 260hz right.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2020 at 2:09pm
If you haven't already, it might be worth a look at Peter Morris's https://soundforums.net/community/threads/new-diy-mid-high-90deg-aka-pm90.11601/ PM90 (& PM 60 on the same site). He too was looking for an efficient low mid horn and came up with something that has certain similarities to your proposed folding, just in a dual 12 version. He certainly uses the single fold and narrow cross section characteristics that you've already identified as useful in getting better HF extension than a typical kick bin/BPH style layout.

Re the H3, I think the XO was 280 so you're about right with your recollection.
These are not my images but from a forum member who had theirs fire damaged a while ago - I can't find the original post but had saved the image out of curiosity.
Looks like the 15 is mounted almost horizontally.




Edited by DMorison - 31 March 2020 at 2:11pm
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