A Bookshelf Multi-Way Point-Source Horn

nc535

Member
2011-04-08 5:12 pm
NC
Just came across this waveguide in PE, very affordable. Would it work to be modified into a synergy horn? Would the exponential flare sound honky?

The horn walls seem flat and relatively easy to attach the mid woofer taps.

PRV Audio WG35-25-B 1" 90 x 60 ABS Waveguide 2/3-Bolt

I think you would be much better off with the Denovo seos12 waveguide. Yes, it cost something as opposed to almost nothing but you can be sure it wouldn't be honky and it would minimize beaming at HF. Furthermore, an exponential horn gives almost no response below its cutoff frequency and might give very disappointing results if synergized.

Denovo Audio SEOS-12 Waveguide 2/3 Bolt Gloss with 1-3/8"-18 TPI Adapter

With the 2" Dayton drivers (1.5mm Xmax) you could get point source probably down to 450 Hz or so, which would mean augmenting it with woofers outside the horn. That would be good because you wouldn't be limited to those puny :) 4" woofers you linked. Aura (NSW2-326-8A) makes a 2" driver with much greater Xmax (the one that HulkSS was going to use) if you are willing to spend a little bit of money, again, as opposed to almost nothing.
 
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I finally made a box for the horns. Just a few details left and its ready for testing.
 
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No photos with drivers yet. I have tested with one driver and just a bowl taped to the outside. I thought it was ok as a proof of concept, so i decided to build one full speaker. Without vents this one wont go below 100hz i think. I forgot the woofer model, but its a p-audio 8 inch. I can check this later, and provide some measurements.
 
There are some 1.5in full range cone, would something like this work?

Keeping in the price range I guess.

Now to look for a woofer, how about a pair of the 4in hivi B4N woofers?

Dayton Audio CE Series CE40P-8 1-1/2" Mini Speaker

HiVi B4N 4" Aluminum Midbass Round Frame

I'd assume these would be for a desktop/bookshelf (truly bookshelf) mini speaker? So perfection and max output aren't, but price:performance is the goal? Like, < $30 for drivers and horn per side?

Just remember, if you're pretty careful, you can lap (sandpaper on a hard surface) the 1" opening to 1.5-2" without losing too much depth. 2" gets you up to the TC7, which is awfully nice for its size and cost.

And, yes, you might be able to squeeze quad 5" around. Would probably need the horns in front of you to tell.
 
Yup, not for max output. Something to get the feet wet without spending a ton of money. If they work well, might end up on top of a 12in MBM crossed at about 200hz? Still too chunky for bookshelf or desktop.

Although with the price of shipping to Singapore, I'd likely pay more for shipping than the actual hardware, if I went with the budget stuff above. Maybe I should get slightly better, Mid level components.

I'll check out the TC7, how about the fostex 2in full range? Any 4/5in woofer recommendation?

Thanks!


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The full range driver choice is critical. I have found the SB65WBAC25-4 to work well as it has a stiff but resonant free and lightweight cone. I have not tried a TC7 but motor is weak so not as good as a driver for a FLH.

Woofers - find whatever you can get locally for cheap. Look for larger Xmax, higher efficiency, Qts from 0.35 to 0.55 should work. Make sure Vas is not too big - you don't want a suspension that's too floppy. Budget no name 5.25in woofers worked well for me.
 
The new tympany compression driver measures very well in this exact PRV audio clone horn. Once the distortion measurements come out, we can see how low it can cross, hopefully 1khz or even less. If yes I'd just go with the CD rather than trying to hack a full range into the horn.

That leaves the woofer choice. Problem is hardly any options in Singapore. Anything available is usually the premium stuff or used, and the TS parameters may not be available.

I may just bite the bullet and buy something that works better from PE, especially if that tympany CD turns out good. Assuming it does, what would be a good woofer output wise to complement that CD with 1khz xo? Do I need to go up to 6 in to keep up?

http://techtalk.parts-express.com/showthread.php?t=1282366

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Just came across this waveguide in PE, very affordable. Would it work to be modified into a synergy horn? Would the exponential flare sound honky?

The horn walls seem flat and relatively easy to attach the mid woofer taps.

PRV Audio WG35-25-B 1" 90 x 60 ABS Waveguide 2/3-Bolt


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It's not an exponential horn, actually, it's a (rather good) constant directivity horn. And yes, you can do a synergy horn with it, but as said above you won't get a very large woofer on it.... but put a smallish woofer or mid on its side and you get the drivers withing 1/4 wavelength and you've got the point-source behavior. The walls aren't all that flat, though, so you'd have to add some mounting surfaces (and seal with something like epoxy putty)

I'm doing something similar with a SEOS15, it works out pretty well.

Directivity is only down to around 1kHz or so (and about 3kHz in the vertical), though, so I'm doing an array trick with a set of spaced woofers to extend horizontal directivity down to around 500Hz.
unsmoothed, un-normalized:
Horiz%20Polar%20No%20smoothing%20Not%20Normalized.png


1/6th octave smoothed:
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Changing to the new Tymphany CD tweeter, looks like it will be a lot flatter response. Pix above are with the CDX1-1445, midrange is TF0410MR (just one of them).
 
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Wow Bill, looks amazing. So you have mids injecting into the seos15, and a pair of side by side woofers to control the directivity even lower using their lobing dips? Woofers are below / outside the seos15 making it a 3 way?
.
Got some pics of it? Measurements look so very good.

How long do you think the tympany CD can cross?

How is the prv waveguide constant directivity compared to the seos15?

Last question, promise. In the tech talk tympany CD thread, someone measured it in a Eminence h290b bi-radial waveguide. The on axis FR looked almost good enough to use without Eq. Is the h290b really that good?

Thanks!

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nc535

Member
2011-04-08 5:12 pm
NC
I'm doing something similar with a SEOS15, it works out pretty well.

Hi Bill:
I like what I see because I've got a pair of SEOS18s to try after I finish my synergy corner horn project. I was going to answer the question as to which gave a better result: the large size possible with a wooden conical horn or the smoothness you can get adapting a SEOS.

I imagine your woofer array will be more elegant than the one on "Big Mal", perhaps more on the lines of that recent offering from B&O?
Jack
 
Small Syns

Well, don't get too impressed yet. The speaker (and my measurement situation) is still "under development". The curves as measured (and designed for) are nice, but distortion isn't great (one of the reasons for trying the different tweeter driver) -
distortion.jpg

The tweeter is being pushed lower than it is comfortable with (without a steep slope, it likes crossing over about an octave above where I have it).

Also, the box is too small for bass. They sound quite good when used downstairs with well-placed subs, but without subs (wife doesn't want more boxes in the living room where they were designed for) they don't sound so hot, no bass at all. And without bass, the baffle step, floor bounce, and a rise around 500Hz or so makes them sound kind of odd when used upstairs (black curve).
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They are also getting placed up against the wall, which lifts some of the low end, but not enough and not very complimentarily with the other room/baffle effects (red curve). Now it's a pronounced hump at 300Hz and still no bass other than a peak around 100Hz, sounds kind of nasal that way.

So, I'm still working on it. I want to incorporate some BSC (for the close-to-wall situation, since a WAF Synergy was the original intent). For our own use, an equalizer will squeak some bass out of the boxes (lots of boost at LF!) and help fill-in some of the floor bounce, but I wanted to also have a design that others MIGHT want to build or work from (engineer ego and all that :p). Which is why I also wanted it to be a design without requiring angle cuts or bevels, and want to keep the crossover reasonably simple.

First shot crossover sims with the Tymphany CD aren't coming out as flat as I hoped (at least not without a complicated crossover).

This is what the woofer arrangement is -- there are two FaitalPro 6inch woofers mounted below and partially behind the waveguide, and firing through ports below the SEOS (rather than through the walls). The ports are short slots that keep the centers near the waveguide center to avoid vertical anomalies (that works pretty well, it turns out). They are spaced so they start to cancel off-axis horizontally at the frequency range where where the SEOS directivity on the midrange starts to give up, a bit of a blending process gettng that happy in the crossover. Actually, less complicated than the 'Malcolm' speakers of a few years ago, other than the baffle having to be cut in layers and be laminated.
SmallSyn.png


Here they are with two choices of foam grille (grilles are important for WAF!)
Grilles.png

Carol chose the black (which is a lot easier to do, too).

I started writing an article/thread about it, but put that on hold till I get the midrange distortion under control and get it doing bass on its own. After I catch up with other home projects, I'll probably do a reflex variation of it, about twice the box volume and a shelf port for actual bass.
 
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Hi xrk971,

The mid (singular!) is a Celestion TF0410MR, firing through two ports near the tweeter. The mid injection is needed because to do the blending trick with the woofers, the output from the SEOS has to go lower than a tweeter CD will do. But it might be doable without a mid using a fullrange tweeter like in your horn? -- I wonder if you could push your woofers out to the edges and blend to extend the directivity even further on your arrangement?

On the single mid, it occurred to me that I don't need the insane output that four or even two horn loaded cone midrances can do, and having fewer holes inside the horn is a better situation for the tweeters that have to fire past them. (It also makes it all cheaper and easier to make, which appeals).
 

nc535

Member
2011-04-08 5:12 pm
NC
But I am impressed - at the elegant simplicity of your solution. And a little surprised - I expected 4 woofers in a vertically as well as horizontally symmetrical pattern.

Hi xrk971,

On the single mid, it occurred to me that I don't need the insane output that four or even two horn loaded cone midranges can do, and having fewer holes inside the horn is a better situation for the tweeters that have to fire past them. (It also makes it all cheaper and easier to make, which appeals).

yeah, but you also note that you are not satisfied with the distortion performance - which would get 6 db better with double the number of drivers. Is it the distortion peak around 1.5 Khz that concerns you? I know you know several CDs would be more comfortable with circa 1 Khz crossover. (e.g. DNA-360)

On the other 2nd mid issue - the additional holes. Add a 2nd driver and switch to half-size holes. You already said you aren't playing that loud. HR will provide a justification. Simulate half area ports through half the material thickness and you will bet the same throat ported chamber response. Then "frustrumize" as agressively as you can.

Jack