The very low budget DIY synergy horn build - Page 2 - AVS Forum
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post #31 of 118 Old 04-21-2012, 07:53 PM - Thread Starter
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Quote:
Originally Posted by FOH View Post

Don't intend to get OT here, because I really dig what you've done here,....just very cool. Jumping in head first and experimenting like this is just fantastic. Thanks for sharing and continued good luck.

Regarding the audible effect, I'm not so sure it's a Doppler related effect. In my opinion, both the physics involved and the sound I heard lead me to believe it's merely a spectral change. I believe it sounds more related to a significant variance resulting the difference off the axial response, spectrally changing as the mic exits the central part of the radiation, and begins coming across the off axis energy.

Just my opinion on what I'm hearing, you guys may be referring to another sound altogether.

Cool stuff.

I'm curious about the harshness you're reporting. Will you elaborate a bit....? Was it level dependent, or did it exist even at modest output levels? Any more ideas on the cause?

Thanks


Thanks FOH, and I don't think your going off topic.
After just after doing some measurements off axis I know your right that moving off axis and a change in the spectral response is the most likely cause for what is heard in the video.

Here are some off axis axis mesurements 0-15-30-40.
The mids look pretty good but the tweeter response is all over the place.
I wonder if somthing like a phase shield would help there.



The harshness is most likely as I said before from running the tweeter and a very cheap one at that, which I didn't think sounded that great in the first place (sounds better in the horn actually) well below its FS and from it "ringing" at the FS. I still haven't given it a thorough listen, I may do that tomorrow and give a better description when I go though all my usual speaker test tracks.


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Originally Posted by AudioJosh View Post

I am curious whether you modeled this or just went willy billy with some math guidance?

Mad respect either way.

#2: No modeling, winISD for port lengths into the rear chamber, a little math to cut the horn, and a few minutes in PCD for the crossover design, I just got lucky with it. It did truly sound like crap at first before the modifications. I have quite a few other enclosures/horns that I made without any modeling that did not turn out well at all. You can see one of them on the floor in the picture of the finished horn after the close up of the tweeter. My bose cube tractrix horn, I found out you can't horn load a 2.5" fullrange and expect good high frequency extension from it, good midrange though.
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post #32 of 118 Old 04-23-2012, 11:25 PM
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This is the first attempt I've seen at using a dome tweeter. I wonder if you might get a better result with a Vifa ring radiator along with an active crossover. What would also be interesting would be running just one mid converted into closed back, vs the same unit as you have now. You can then compare the sim vs measured in REW and see how they compare. You can then see how well Hornresp predicted your result.


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post #33 of 118 Old 04-25-2012, 09:01 PM - Thread Starter
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Quote:
Originally Posted by paulspencer View Post

This is the first attempt I've seen at using a dome tweeter. I wonder if you might get a better result with a Vifa ring radiator along with an active crossover. What would also be interesting would be running just one mid converted into closed back, vs the same unit as you have now. You can then compare the sim vs measured in REW and see how they compare. You can then see how well Hornresp predicted your result.


First let me say that you do some fine work Paul, and your synergy horns put mine to shame, I am looking forward to see how your S3 turns out.

I know an active crossover would help a whole lot vs the passive with I could cobble together from what parts I had laying around. I think one of the ring radiators would do better, but right now I am happy with the performance. I did have one of the sony's coverted to sealed back at one point. Even tried it in the horn but thought it sounded terrible, I never thought to measure it. Looks like I'll need to seal it up again and throw it in the horn.

Right now I did some more listening and I don't think I'll make any changes to it it. The issue with the tweeter being a bit harsh really is not all that bad unless you are right in front of it while it blasts at 115dB+, further away it smooths out and sounds quite nice.



I built a DIY dust separator:


I needed an excuse to try it out and so I started the second synergy horn.


I'll only try and post pics of steps during the first build that I missed, if there are any steps you would like me to cover more thoroughly let me know and I'll make sure to do so.

All four sides cut and ready for holes to be drilled.


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post #34 of 118 Old 04-26-2012, 09:02 AM
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VERY cool! I would love to try a build like this.
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post #35 of 118 Old 05-02-2012, 02:52 PM - Thread Starter
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Update, I finished the second horn and listened to music in stereo with them for the first time WOW. They image excellent, and have a very open soundstage, I had them in a small room and on some music they tend to disappear I really could not tell that sound was coming from them. The only downside is the tweeter, it is the bottleneck of the speaker, once you start to get above about 105dB @ 1m they go downhill fast, that 1" dome just can't keep up. Also I measured the horn from too close on post #17 and it gave me a better then expected bass response, it is more like post #31 where before the subs cross in the response is about 5-6dB down.

So budget synergy horn project #2 is in the design phase:

3-way horn covering 80-20,000hz

2 10" woofers 10" PE Buyout Woofers

4 5" mids (same sony buyouts as before but sealed up)

1 1" exit CD (don't know what I am going to use yet but I would like to snag a pair of Erich's DE250 clones when they become available)

Same horn profile and size.

Some hornresp simulations this time, mids input;


mids resp, I am going to seal up one of them to test in the V1 horns and compare the measured response to this:


Woofers input:


woofers resp:
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post #36 of 118 Old 05-06-2012, 05:40 PM
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Very interesting thread, I like that your aiming to 100Hz, makes them usable with subs or towers. I'd love to see them stay passive, but it could become a pain!

Have you investigated what effect different shapes will do to response and directivity?

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post #37 of 118 Old 05-07-2012, 09:31 AM - Thread Starter
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Quote:
Originally Posted by MitchH311 View Post

Very interesting thread, I like that your aiming to 100Hz, makes them usable with subs or towers. I'd love to see them stay passive, but it could become a pain!

Have you investigated what effect different shapes will do to response and directivity?

Subscribed.

My first ones can play down to about 100hz with some boost at the low end, I had them playing without subs and they do alright.
A pair of the new ones should give you a little more then 120dB/1M at 80hz with 50 watts input per horn before reaching the woofers xmax. I would need to build new subs just to keep up with them.

I am planning on keeping them passive because as of right now I don't have an electronic crossover.
I was looking at the miniDSP but the 2x4 can't do a three way active I would need the 2x8 kit and I am not ready to shell out $300 for that.

I have not done any experiments with the shape and it changing the response/directivity but Paul Spencer at his thread linked in the first post or at his site redspade-audio has done some.
His website/blog is great, lots of other good information as well.
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post #38 of 118 Old 05-07-2012, 09:44 AM
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Quote:
Originally Posted by mtg90 View Post

I was looking at the miniDSP but the 2x4 can't do a three way active I would need the 2x8 kit ...

Yeah, it can, use the 2x4 with the "4-way Advanced" crossover plugin. You'll need a 2x4 for each speaker, though.

DIY Synergy horn spreadsheet
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post #39 of 118 Old 05-07-2012, 10:06 AM - Thread Starter
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Quote:
Originally Posted by bwaslo View Post

Yeah, it can, use the 2x4 with the "4-way Advanced" crossover plugin. You'll need a 2x4 for each speaker, though.

I didn't think of that, but I like the challenge designing of passive x-overs plus I already have lots of spare x-over parts.
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post #40 of 118 Old 05-07-2012, 02:35 PM - Thread Starter
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I got around to sealing up one of the sony driver and mounting it in one of my V1 synergy horns for a quick measurement:


I have a feeling that I could flatten out that bump at 850hz and push it up above 1k with some modifications, but I have to see what happens when I
finish one of my v2 horns because it has a different port size and position. Right now I have 6 sides cut, with the mid ports drilled into four of them,
I am trying to figure out where the woofer ports should go. Due to the angle of the horn and the position of the woofer it looks like my woofer ports will
need to be closer to the center of the horn then I would like. I don't see how it could be done another way without using four smaller drivers.

Here are the drivers, the sony sealed up and the 10" buyout woofer.



Trying to mark out driver positions before I cut, I should say that this one will be slightly larger then the V1 in order to fit all the drivers, 22" mouth compaired to 20".



Most of the sides cut:



Mid ports drilled into the first 4 sides:



As you can see I am building these out of 1/2" ply to keep the weight down, they will have more then twice the material as the v1's did and those got heavy when I put the enclosure on the rear.
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post #41 of 118 Old 05-07-2012, 03:23 PM
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Quote:
Originally Posted by mtg90 View Post

I don't see how it could be done another way without using four smaller drivers.

You could possibly move the ports to the far sides of the horn. 1 port per woofer, and 2 woofers, right? If so, consider this: top face, port left, and bottom face, port right. This will give a bit of symmetry.

John


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post #42 of 118 Old 05-07-2012, 06:02 PM
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Quote:
Originally Posted by mtg90 View Post

I have not done any experiments with the shape and it changing the response/directivity but Paul Spencer at his thread linked in the first post or at his site redspade-audio has done some.
His website/blog is great, lots of other good information as well.

Thanks ... I got together with Gainphile and Antripodean (who has a Yorkville Unity) and measured them outdoors for directivity. The results are here:

http://redspade-audio.blogspot.com.a...surements.html

What you see with conical Synergy horns is that they have constant directivity down to a point defined by their coverage angle and mouth size, which is predicted by a formula that I believe Bill put into his spreadsheet. Having a big mouth and a wide angle extend a constant beamwidth down lower, but this must be balanced against size and extension. A narrower coverage horn tends to extend the bottom end down further, or if you want you can add more drivers to have a wide horn that also goes low for a given size. This is why I use 6 mids in a 2 way, it allows me to get down low with an 80 x 60 whilst using small mids that extend up past 1k. It's all about choosing your compromises!

The other thing you notice is that sometimes the pattern narrows at a certain point before pattern control is lost and then broadens at low frequencies. This effect was described by Keele in his paper on the CE horn. This is why you see a second wider flare section on Synergy horns - the idea is to avoid that narrowing. If you download his paper on the CE horn, which is basically an exponential throat joined to a conical horn with the latter 1/3 of the horn at 2x the flare angle, you will see it's a bit more dramatic than the second flare on Synergy horns. This is something to experiment with, although it takes quite some time to keep building multiple versions of this thing!

You may notice the Yorkville doesn't do so well in this regard and they did not bother to pay much attention to this aspect. It has a bit more top end as they used a BMS compression driver but being a fairly small axi symmetric conical horn, the directivity isn't as good as the others, it's about the same size as a 15" driver 0.4m. S1 which is the next one is 0.5m wide (60x60) and S2 is 90 x 40 and 1m wide, so extends beamwidth down to 280 Hz.

When I heard the original Unity kit, it had about $700 worth of passive crossover in it! Some decent quality parts in it, but for that you can buy digital xo and amps!

Looking at that mid response, if doing it active you could just add a couple of notch filters and then xo around 300 / 900. That then leads to a compression driver and again if you are doing it active this is easier. Celestion CDX1 is a good one to consider. At one GTG we measured and compared it to a B&C DE250 and it measured very similar and the sound also appeared quite close. I'd guess it would be fine with a crossover that low for home use.

Regarding your woofers, the holes are placed in corners as you probably realise to avoid interference. Having two holes allows them to be smaller and avoid different path differences from the cone to the port. However, in this case I'd overhang the baffle so the woofer has just one port in the corner, and I would change the shape to a slot if size becomes an issue. If using two woofers only, then you want to mirror the other woofer and have it over the same side of the horn. The idea is to have vibrations from drivers working against each other. If these are cheap buyout woofers and you have enough, perhaps just use 4? You then overhang the baffles and then brace the edges that extend out against each other.


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post #43 of 118 Old 05-07-2012, 07:24 PM - Thread Starter
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Quote:
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Looking at that mid response, if doing it active you could just add a couple of notch filters and then xo around 300 / 900. That then leads to a compression driver and again if you are doing it active this is easier. Celestion CDX1 is a good one to consider. At one GTG we measured and compared it to a B&C DE250 and it measured very similar and the sound also appeared quite close. I'd guess it would be fine with a crossover that low for home use.

Regarding your woofers, the holes are placed in corners as you probably realise to avoid interference. Having two holes allows them to be smaller and avoid different path differences from the cone to the port. However, in this case I'd overhang the baffle so the woofer has just one port in the corner, and I would change the shape to a slot if size becomes an issue. If using two woofers only, then you want to mirror the other woofer and have it over the same side of the horn. The idea is to have vibrations from drivers working against each other. If these are cheap buyout woofers and you have enough, perhaps just use 4? You then overhang the baffles and then brace the edges that extend out against each other.

That mid plot is far from the finished product, I'll post another when I get this horn built. As for the CD which celestion CDX1 did you test? There are about 10 different CDX1 models.

I only have 4 of those woofers and they sold out right after I ordered them, how much of a difference would mounting the drivers offset and using 1 port per driver have on response and pattern control of the horn? I know they are located in the corners where pressure is at a minimum to keep turbulance and other things like that low, but at that far away from the throat would it really do all that much damage? You can see where I plan to place them in the picture before I cut the panels, the ports would be about 1/2 way from the center to the corners.

$700 in crossover parts was that per speaker of for the pair?
If I hit $50 per speaker in crossover parts then I'll start to think about going active.
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post #44 of 118 Old 05-07-2012, 08:04 PM
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Quote:


As for the CD which celestion CDX1 did you test? There are about 10 different CDX1 models.

CDX1 ... hmmm you got me there! It was a bolt on ferrite magnet version. Looking it up, would have to be this one:

http://www.parts-express.com/pe/show...umber=294-2124

Quote:


I only have 4 of those woofers and they sold out right after I ordered them, how much of a difference would mounting the drivers offset and using 1 port per driver have on response and pattern control of the horn? I know they are located in the corners where pressure is at a minimum to keep turbulance and other things like that low, but at that far away from the throat would it really do all that much damage? You can see where I plan to place them in the picture before I cut the panels, the ports would be about 1/2 way from the center to the corners.

There is another:
http://www.parts-express.com/pe/show...number=299-283

8 of them for $40 + shipping ... you could pick them up with a CD and the shipping might look better.

I haven't tried a 3 way horn, nor have I measured putting ports in the middle, so it's hard to comment beyond a very rough guess. I wouldn't try it unless you want to find out why not to do it the wrong way!

You can see even in some Danley designs where they show a 2 and 3 way version on the same horn, woofer ports have an impact. That becomes even more so when you break the rules!

Pattern control is probably not at stake here, that is a function of the design of the horn itself primarily.

$700 for both.

Quote:


If I hit $50 per speaker in crossover parts then I'll start to think about going active.

Don't overlook the fact that a passive crossover only works for one attempt, while a digital active crossover can be recycled many times over. Judging by your work so far, you'll get your money back and come out ahead. Spend a little on a few amp channels and a digital active xo and you can quickly put together different designs, optimise them better over time and not have to buy parts for each version of the crossover. You can always build a passive xo once you reach a point you are happy to stick with something for a while.

I've been involved in events where we have set up a range of active speakers in a day, swapped out some drivers, mixed and matched, measured a bunch and listened. We rigged up crossovers on the spot in minutes.

One example here:

http://redspade-audio.blogspot.com.a...-shootout.html
and another
http://redspade-audio.blogspot.com.a...ide-gtg-2.html


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post #45 of 118 Old 05-07-2012, 10:07 PM - Thread Starter
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With passive if something did not turn out well you can still salvage all the parts, not just one time use, but I know it's only a matter time before I go active.

Those other woofers may or may not work in these horns, too late for me to do some hornresp on them (I'll see Vrc, Vtc, Apt, Lpt and woofer plots floating around in my dreams). I don't really care if I break rules, the overall enclosure design would need to be redone for offset woofer placement and I can live with a less then optimal axial response. These are just an experiment right now, if this was a speaker that I would be listening to all the time then I would be more worried about getting it right the first time.

I'll finish one before going further on the second if the first turns out terrible then I will try somthing different. That way all who are watching can learn from me what not to do.
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post #46 of 118 Old 05-08-2012, 12:48 AM
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If this is an experiment then consider doing one as you have planned, and another with the ports in the corners.


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post #47 of 118 Old 05-08-2012, 04:28 AM
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I'm working on a 3way too, and am up against a similar conundrum...do I make big round ports for the woofers or use oval holes radially aligned? Which does the least damage?

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post #48 of 118 Old 05-08-2012, 04:55 AM
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Interesting point. The Yorkville has no corners, so they use slots for the mids as well. The response is reasonably smooth. In the case of woofers I would simply use a slot, although it is curious that DSL don't always do this, probably where they have determined they aren't necessary.


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post #49 of 118 Old 05-08-2012, 06:02 AM
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Quote:
Originally Posted by mtg90 View Post

With passive if something did not turn out well you can still salvage all the parts, not just one time use, but I know it's only a matter time before I go active.

The biggest benefit you'll appreciate from a minidsp is delay. You can quickly time align your drivers and get a flat phase over a wide range of coverage, instead of having to design a ladder delay network.

The other thing you'll find out is that you can add eq boost, not just cuts that notch filters yield. This will allow you to "prop up" the frequencies around your cuts to keep things nice and flat. Plus, room eq wizard has an "easy" button- just choose your target and let it do the heavy lifting.

I know $100 bucks a pop isn't chump change, but I don't think you'll regret it once you've used it.

FWIW,
John


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post #50 of 118 Old 05-16-2012, 02:08 PM - Thread Starter
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I have done a bit more on the V2 build, I am going to keep the round woofer ports where they are on this one and see how well it turn out. I am still deciding on which CD to get it going to be the Celestion 1745, Selenium D220ti's or the DE250 clone. Right now I have some Selenium D200E-E's (pulled from one of my other speakers) which I am going to play around with an see how they do.

Also I was thinking about this (only thinking not planning on trying it), don't know if anyone else has thought / tried it yet, some of these Selenium D250-X for the mids playing down to 350-400 hz. You don't get the filtering of HF that you would with a cone driver and front chamber though. Placement could be very close to the HF driver and a higher crossover point could be achived. Anyway just a thought.



So here are the sides with woofer ports in them, as I said before I am trying this one with the round woofer ports where I can get them to fit with the centered woofer.



Dry fit.



Backside dryfit.



Here is the glue I use for anything when the parts will be at an angle while the glue is drying. It works just as well as normal titebond but does not drip or run off of where you apply it, and it works great for these.



I had a little more trouble putting this one together with plywood vs the MDF on the other. The plywood had a little bit of a warp to it and that is much harder to straighten when you cannot easily clamp it out while gluing like you can with a rectangle enclosure.



Woofer mounting ring in place.



Time to make mid mounting rings with the trusty old DIY circle jig. the woofer/mid mounting rings are made out of some cheap plywood that I had laying around so I could save the better stuff for pieces that are not going to be hidden inside.





Gluing those on was a bit of a challenge.



Time for some measurements, first with one mid.





Then with all four:


I had use a chamfer bit on the mid ports to shorten them some but it did not remove as much as I hoped, so I used a wood rasp to remove even more. It took a lot longer but did much better.



Measurements, 1 mid, 4 mids after chamfer bit, 4 mids after wood rasp. It flattens out quite a bit with 4 mids vs 1, and after I shortened the port length with the wood rasp it pushed the frequency up a little but not as much as I hoped. Should be able to get a crossover point around or a little above 1K.
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post #51 of 118 Old 05-16-2012, 02:35 PM
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Lookin' good. How are you going to get a crossover point over 1k? With the measurements posted, it looks like your upper F3 is around 850hz or so. I'm sure I'm missing something here.

I'll add this other observation, and anyone can chime in here with their thoughts: smoothing the throat of the horn is KEY! This is what I've gathered from reading lots of diyaudio posts by Earl Geddes and Tom Danley. From what I can tell, any sharp transition points (like right angle corners) in the first inch or two are major diffraction generators, which can generate high order modes which contribute to "horn honk" and "bite." Here's a recent relevant thread:

http://www.diyaudio.com/forums/multi...mpressive.html

Turning a square hole into a round one that then transitions into a square horn is the job at hand here. I really liked using drywall mud for my horn, as its non toxic, easily sandable (you can do it with your finger), easily fixable if you goof, dries/layers quickly (especially if you use a heat gun), and can be reinforced with drywall sealer. I can't speak to the longevity of this method, however, as I only just built my horn.

Please note that I'm not a speaker designer or in any way an expert on horns. The above just represents what I've boiled down from the experts over the past several months of reading.

John


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The 1K crossover point is going to be achived with some passive x-over trickery .

It's funny you talk about smoothing the throat I was working on that last night and today, I stopped posting once I got to the mid measurements. Right now I am working out how I am going to build the rear enclosure for the horn.

HF driver plate, I should be able to mount 1" / 1-1/8" domes, and screw on/bolt on CD's to this one.


Looking down the throat no smoothing done yet.


Home made screw on adaptor mounted to plate with a Selenium DH200E-E.



Looking down throat with CD mounted.


Horn with HF/mid drivers mounted.



Here is the throat after I hit it with the wood rasp, I may do some filling with wood filler but it is very smooth already.



Here are HF measurements with the DH200E-E, before and after smoothing the throat. The largest improvement is between 10 and 15K, you may think that the response looks bad but take a look at the DH200E PDF and you can se that it looks alot like their measured graph. It is not a very flat driver at all, the other speaker I use it in has a much lower sensitivity so I could flatten out the dip after 8K quite a bit. I am not quite sure what the 900 and 300hz dips are from as they show up with the dome tweeters I tried as well. The woofer ports where taped up when I measured (no woofers mounted) but mid ports were open.
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Really nice work on the throat, and it shows in the graphs. What kind of wood rasp did you use? I used ovoid and rat tail files. Can you post a pic of the rasp?

John


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Quote:
Originally Posted by johnbomb View Post

Really nice work on the throat, and it shows in the graphs. What kind of wood rasp did you use? I used ovoid and rat tail files. Can you post a pic of the rasp?

John



Thanks,

The rasp I used is one from a cheap set from harbor freight, 12-piece-file-and-rasp-set-97070
In the picture its the 4th one in from the left with the large teeth, works well but the metal is soft and you can easily bend it if not carful.
A little sanding was done in the throat after using the rasp, but not on the mid ports and you can clearly see the difference.
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If you make the square of the throat smaller, so the edges overlap the circle, then you will make things easier, with less filling and a little more filing.

What are your port offsets?

You can import a hornresp sim into REW and see how your accuracy compares. You export, delete two colums in Excel (2nd and 3rd from memory), save it then import into REW.

Looks like you will struggle to get the crossover higher than about 850 Hz, unless you can get the mids to extend higher before working on the crossover.


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This is the kind of transition you might want to aim for:



You can see the 18mm mounting plate where there is a radius transition that takes into account the compression driver exit angle. The idea is to make it smooth and not increase the area too rapidly. The fact that you are going from a circle to a square tends to make the increase in area more rapid. I don't think I have any photos or images that show how I actually did it, but you can imagine the walls set in a bit more.


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post #57 of 118 Old 05-17-2012, 04:04 PM - Thread Starter
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Quote:
Originally Posted by paulspencer View Post

If you make the square of the throat smaller, so the edges overlap the circle, then you will make things easier, with less filling and a little more filing.

What are your port offsets?

You can import a hornresp sim into REW and see how your accuracy compares. You export, delete two colums in Excel (2nd and 3rd from memory), save it then import into REW.

Looks like you will struggle to get the crossover higher than about 850 Hz, unless you can get the mids to extend higher before working on the crossover.



The picture makes the transition look sharper then it actually is. A thicker mounting ring would also do the same as a smaller throat, giving more material that can be removed to smooth the transition, but no matter how it is done I now know that the slow smooth transition from compression driver exit angle to horn throat angle is key.


Here is the current hornresp input for the mid drivers, 8.5mm mid port offset.




You learn somthing everyday, thanks for the hornresp export tip Paul, I just went into notepad and deleted the whole first row.

Sim vs measurements, get the usual highs dropping off earlier then predicted, a bit smoother then predicted, the sim shows a peak at 2K that is not there in the measured response but otherwise very close.
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post #58 of 118 Old 05-17-2012, 04:46 PM
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I'd say that is really close.

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post #59 of 118 Old 05-17-2012, 04:50 PM
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That's a pretty good correlation. You can export into Akabak and then also import that into REW as well. I found Akabak did better with the same details above the upper rolloff point.

My conclusion so far with the upper end of the mid is that you just have to allow for a bit more than you think you need.


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post #60 of 118 Old 05-17-2012, 06:23 PM
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Quote:
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I'd say that is really close.

Me, too. Looks like you can drop in a notch filter at around 3.6k or so w/ a Q of maybe 1.5-2 and kill that hump, taking the low pass of your crossover from good to great.

John


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