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post #12721 of 12740 Old 07-15-2017, 05:19 AM
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Parham & Directivity

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Originally Posted by Eternal Velocity View Post
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[huge snip]
It's easy to even make a 6.5" + cheap 1" dome 2-way sound smooth and inoffensive IE aformentioned BBC dip or to voice for a decent power response, but that's all flawed from the get go. I hope what parham's doing isn't along those lines. I think I'm on exactly the same page as LTD02... directivity matching and driver selection are important...but i'm not willing to place power response before all else including direct response.
Oh, believe me: Wayne Parham takes directivity very seriously, including matching it between drivers (among a lot of other things). Though (obviously) I can't speak for him, I believe that is the reason he uses CD's in his design to start with.
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post #12722 of 12740 Old 07-15-2017, 01:14 PM
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On axis response

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Originally Posted by Eternal Velocity View Post
[snip]
You should start by understanding each abberation in the "on-axis" measurements. What exactly is it that doesn't look good, and why is there? Is it a resonance? If so can it be corrected electrically or does it need to be corrected mechanically or acoustically? Either way it needs to be corrected if it's in the listening window.
[snip]
Like a null 7 degrees off axis?
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post #12723 of 12740 Old 07-23-2017, 08:27 AM
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Blast from the past xover design

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Originally Posted by bwaslo View Post
Hi Erich,

It's those Inductor-Capacitor-Resistor (LCR) strings that go across the CD driver. Can't just take them out, other stuff would need to be adjusted to compensate or it would sound awful. I did run some designs without those LCR, but really think they should be left in. One of the bumps they deal with is at 2kHz, which is a terrible frequency to have a bump at (near where ears are most sensitive). Why go to all the trouble of waveguides and CDs and then cheap out on a few components?

Besides, I'm too lazy to do it all over again![broken link] Did my mass speaker designing this past week, got to get back to some other things now.

I don't really think there is a difference between HT and HiFi design goals. HT might need to play louder (and maybe not), but flat response is still good -- overall response shaping can be added at the receiver or equalizer, better than hardwired into the speaker.

The components inside the dashed-line box (in the schematics) are fixed resistors. The "L-Pad" notation is just to say they could be replaced with an L-Pad if someone wanted to for whatever reason. I wouldn't, myself, L-Pads are just another mechanical part to go bad, fixed resistors are lots more reliable.

Crossovers shouldn't have to change if you just are moving the woofer closer to the WG.
[@]bwaslo[/@] Are all these graphics (plus those from post 21853196) posted elsewhere (or at least the schematic)? Yeah, I know this is five years later, and I'm getting quite an education from reading the whole thread. This design looks to be foundational, not to mention executed using a relatively inexpensive woofer, so I'm hoping there is some way I could see the schematic (I come from the electronics end of the hobby, so I can read the schematic and build the crossover from it)
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post #12724 of 12740 Old 07-24-2017, 01:58 PM
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BWaslo's SEOS12 with Designer12 woofer

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Originally Posted by lloydrmc View Post
[@]bwaslo[/@] Are all these graphics (plus those from post 21853196) posted elsewhere (or at least the schematic)? Yeah, I know this is five years later, and I'm getting quite an education from reading the whole thread. This design looks to be foundational, not to mention executed using a relatively inexpensive woofer, so I'm hoping there is some way I could see the schematic (I come from the electronics end of the hobby, so I can read the schematic and build the crossover from it)
To answer my own question: Yes the schematic is posted of this early reference design -using "Dayton Audio DS315-8 12 inch Designer Series Woofer Speaker Part # 295-434" (IIRC) for the SEOS when it first became available from Erich's DIY Audio Group.

The problem was the graphics that [@]bwaslo[/@] had posted on this thread of the crossover schematic, polar response graphs, etc. were broken. I found a later reference to the forum where the design was posted, but that was broken too, b/c apparently Erich had redesigned his web site in the meanwhile.

Not to worry. I found the forum http://www.hificircuit.com/community...r12-woofer.11/

and the (revised) crossover schematic https://www.circuitlab.com/circuit/w...12-delta12lfa/

This would be a good "entry-level" DIY project to get started using the most excellent (by all accounts) SEOS waveguide, as the woofer is relatively inexpensive, yet it's still a very capable speaker. Note that you can utilize Erich's own DNA-360 Compression Driver to save some money while not sacrificing performance.
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post #12725 of 12740 Old 07-24-2017, 03:14 PM
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Quote:
Originally Posted by lloydrmc View Post
To answer my own question: Yes the schematic is posted of this early reference design -using "Dayton Audio DS315-8 12 inch Designer Series Woofer Speaker Part # 295-434" (IIRC) for the SEOS when it first became available from Erich's DIY Audio Group.

The problem was the graphics that [@]bwaslo[/@] had posted on this thread of the crossover schematic, polar response graphs, etc. were broken. I found a later reference to the forum where the design was posted, but that was broken too, b/c apparently Erich had redesigned his web site in the meanwhile.

Not to worry. I found the forum http://www.hificircuit.com/community...r12-woofer.11/

and the (revised) crossover schematic https://www.circuitlab.com/circuit/w...12-delta12lfa/

This would be a good "entry-level" DIY project to get started using the most excellent (by all accounts) SEOS waveguide, as the woofer is relatively inexpensive, yet it's still a very capable speaker. Note that you can utilize Erich's own DNA-360 Compression Driver to save some money while not sacrificing performance.
lloydrmc,

Glad you found what you were looking for. Truth to tell, I don't even remember that design (getting old). Probably have it on an old laptop computer somewhere, but you've saved me the trouble of looking.

The DNA360 driver can not only save some money, but at least with the ones I've measured, is singificiantly smoother than the DE250, too. Much smoother than the Dayton rendition, too.
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___________________________________________
DIY Synergy horn spreadsheet Synergy horn spreadsheet and pdf
XSim -free crossover designer and simulator XSim install file
Easy and cheap sound diffusers (the "Depot Diffusers") making easy DIY depot sound diffuser-panels-step by step.html
SmallSyns - point source controlled directivity in a manageable size SmallSyns
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post #12726 of 12740 Old 07-24-2017, 03:52 PM
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Originally Posted by bwaslo View Post
lloydrmc,

Glad you found what you were looking for. Truth to tell, I don't even remember that design (getting old). Probably have it on an old laptop computer somewhere, but you've saved me the trouble of looking.

The DNA360 driver can not only save some money, but at least with the ones I've measured, is singificiantly smoother than the DE250, too. Much smoother than the Dayton rendition, too.
While we're complimenting the DNA-360, I'll mention that I'm using the DNA360 in an active design with aggressive DSP. I have boosted the output to be flat all the way out to 20 kHz without any ill effects at all. It would seem that real world content contains very little energy in the last half octave. The only signals that ever push the output levels up high enough to be of concern are the sine sweeps that I use for measurement. FWIW, I am able to confirm these facts by observing the peak indicators on my Motu 16A audio interface.

The only complaint I have with the CD is the narrowing of directivity around the 17 kHz break-up frequency, yet this the audibility of this feature (albeit in my room with lots of diffusion) is so subtle that I'm probably the only one who will ever notice. Maybe some day I'll feel adventurous and try out a Beryllium CD, but I don't know if I could find with comparable low frequency extension. The sound I get is incredibly smooth, as good or better than any dome speaker I've heard, and with all the wonderful dynamics that a CD brings to the table.

Edit: In case anyone is wondering whether extension to 20 kHz makes an audible difference, the answer for me is a strong YES! That's despite the fact that my ears tap out at around 17 kHz using sine waves. Apparently sine waves are of limited use for assessing the upper frequency limit of hearing.
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post #12727 of 12740 Old 07-24-2017, 03:57 PM
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DNA 360 Compression Driver

I see that the DNA360 compression driver shows as out of stock? Anybody have an idea when they will be available again? I like to snag a pair.
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post #12728 of 12740 Old 07-24-2017, 04:30 PM
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Anyone try the BA CD? Only found one review online and he loved it.

Be phrams do more than just extended FR. I'd love to hear a pair someday.
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post #12729 of 12740 Old 07-26-2017, 02:00 AM
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Originally Posted by Carl_Huff View Post
I see that the DNA360 compression driver shows as out of stock? Anybody have an idea when they will be available again? I like to snag a pair.
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Bummer! I hope it's temporary. I'd like to pick up a couple more for the surrounds that I'll get around to building some day. (I already have the horns.) If not, I guess I'll look at the B&C DE-250 or maybe BMS 4550.
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post #12730 of 12740 Old 08-13-2017, 07:27 PM
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Anyone remove the bug screen on their DE250's in order to use some putty or clay to smooth the transition between the throat and the entrance to the SEOS? I know the SEOS was originally designed to match the DE250's but I'm wondering if there are any gains in diffraction reduction to be had by doing this. I know Geddes does something like this with his speakers. Is there an easy way to remove the bug screen or does it have to be cut out?
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post #12731 of 12740 Old 08-13-2017, 08:49 PM
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As far as I can tell it has to be cut out. But I havent had to disassemble one yet. Ive thought about it many times but just feel its not worth the effort and loss of protection against my kids. If I didnt have kids I'd probably try it.

Let us know if you do it!

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post #12732 of 12740 Old 08-13-2017, 09:09 PM
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As far as I can tell it has to be cut out. But I havent had to disassemble one yet. Ive thought about it many times but just feel its not worth the effort and loss of protection against my kids. If I didnt have kids I'd probably try it.

Let us know if you do it!
Yeah. And to be really helpful, post before/after polar measurements. Yeah, that's a big pain. But I have trouble believing it makes that much of a difference. If it does, it should be possible to measure it.
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post #12733 of 12740 Old 08-14-2017, 06:06 AM
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Yeah. And to be really helpful, post before/after polar measurements. Yeah, that's a big pain. But I have trouble believing it makes that much of a difference. If it does, it should be possible to measure it.
If I end up doing this I'll definitely post some before and after measurements. I already had a few measurements with the screens in place. I noticed some ripple in the impulse response that seemed like it could correspond to a reflection in the throat. It might also just be the bump at 17 kHz in the DE250's response. We'll see if hte DE500's are any different.

I've got a pair of each of the DE250's and DE500's from Parts Express. I'm going to choose between the two and send the others back. If removing the bug screens is permanent or requires lots of disassembly, then it'll have to wait until I send one of the pairs back.

edit: Earl Geddes responded to me that he cuts the screens out with a sharp knife, so unfortunately that would be a permanent solution. If I do that, it will definitely wait until I choose DE250's or DE500's. I'm not sure how easy it will be to get a smoother edge after the screen is cut out. I'm also not sure whether I'm going to fab up some foam plugs ala Geddes so it might be better to leave the screen in place...


Dan

Last edited by dane10; 08-14-2017 at 07:28 AM.
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post #12734 of 12740 Old 08-14-2017, 09:59 AM
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Originally Posted by dane10 View Post
If I end up doing this I'll definitely post some before and after measurements. I already had a few measurements with the screens in place. I noticed some ripple in the impulse response that seemed like it could correspond to a reflection in the throat. It might also just be the bump at 17 kHz in the DE250's response. We'll see if hte DE500's are any different.
Ripples in IR essentially *always* correlate with bumps in FR, and the bump in 17 kHz is almost certainly from diaphragm break-up. The only real treatment for that I know of is a Beryllium diaphragm.
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post #12735 of 12740 Old 08-14-2017, 10:14 AM
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Ripples in IR essentially *always* correlate with bumps in FR, and the bump in 17 kHz is almost certainly from diaphragm break-up. The only real treatment for that I know of is a Beryllium diaphragm.
Yes, the diaphragm break-up as you suggest is my suspicion now. My first thought was that the ringing and the bump might be due to a reflection or diffraction at the throat as the wavelength was about right. I was hopeful that removing the bug screen and smoothing the transition between the throat and the entrance to the wave guide would help, but even Geddes's models which use the DE250 have a similar bump at that frequency. I also see similar ringing due to that 17 kHz bump in the impulse response of his ESP15's. He removes the bug screen and smoothes the transition between the CD and the waveguide with clay or putty. So it does imply to me it's happening within the driver, maybe at the phrase plug or the diaphram breakup as you suggest. The SEOS12's with the DE250's sound so good right now that I'm starting to think it's not worth tampering.
Dan
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post #12736 of 12740 Old 08-14-2017, 10:44 AM
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Yes, the diaphragm break-up as you suggest is my suspicion now. My first thought was that the ringing and the bump might be due to a reflection or diffraction at the throat as the wavelength was about right. I was hopeful that removing the bug screen and smoothing the transition between the throat and the entrance to the wave guide would help, but even Geddes's models which use the DE250 have a similar bump at that frequency. I also see similar ringing due to that 17 kHz bump in the impulse response of his ESP15's. He removes the bug screen and smoothes the transition between the CD and the waveguide with clay or putty. So it does imply to me it's happening within the driver, maybe at the phrase plug or the diaphram breakup as you suggest. The SEOS12's with the DE250's sound so good right now that I'm starting to think it's not worth tampering.
Dan
If you measure at different horizontal/vertical angles, you will see that the bump varies across space, which is also a symptom of break-up. In this region, the diaphragm is no longer moving like a piston.

If you have EQ capability or are able to create a passive circuit, you can suppress the break-up to some degree, but you will only be able to improve the response in a spatially-averaged sense being that the bump will vary with angle.

If done properly, I believe it can improve sound quality, depending on its severity, but keep in mind that by suppressing the break-up, you will also suppress the overall output at the top. Without compensation via a broad boost, this modification may diminish overall presence up there. That might not be a good thing.

I have practically unlimited EQ capability and am content to do a lot of measurements at different angles, so I can and do fix these things. In a passive design, I'm not sure it's worth the trouble. It's your call.
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post #12737 of 12740 Old 08-14-2017, 11:43 AM
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Originally Posted by awediophile View Post
If you measure at different horizontal/vertical angles, you will see that the bump varies across space, which is also a symptom of break-up. In this region, the diaphragm is no longer moving like a piston.

If you have EQ capability or are able to create a passive circuit, you can suppress the break-up to some degree, but you will only be able to improve the response in a spatially-averaged sense being that the bump will vary with angle.

If done properly, I believe it can improve sound quality, depending on its severity, but keep in mind that by suppressing the break-up, you will also suppress the overall output at the top. Without compensation via a broad boost, this modification may diminish overall presence up there. That might not be a good thing.

I have practically unlimited EQ capability and am content to do a lot of measurements at different angles, so I can and do fix these things. In a passive design, I'm not sure it's worth the trouble. It's your call.
Hi awediophile,
I am currently running active via Frequency Allocator so I do have a good amount of eq available to kill any peaks like this. However my end goal is passive so I'd rather remove anomalies acoustically, such as through reducing diffraction where possible. Hopefully this will lead to a simpler circuit and improve response across a wider spatial range of angles. My current setup has lots of room for improvement, The SEOS12's are sitting baffleless atop another set of speakers. There's definitely a lot of room for diffraction reduction still. I haven't had much time to take polar measurements yet, but the attached measurement is about 5-10 degree off axis and without eq for CD. However response still looks pretty good all things considered.
Dan

edit: links replaced with attachments.
Attached Images
File Type: jpg DE250_Silverflute_nobaffle.JPG (306.3 KB, 22 views)
File Type: jpg DE250_HOLM.JPG (133.5 KB, 20 views)

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post #12738 of 12740 Old 08-14-2017, 12:50 PM
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Err, I don't see your attachment. But anyway, the problem of the break-up peak can only be reduced using EQ or a passive circuit. And it can only be eliminated (in terms of its directional consequences) by using Be diaphragms. Good luck with your project.
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post #12739 of 12740 Old 08-15-2017, 07:31 AM
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Originally Posted by awediophile View Post
Err, I don't see your attachment. But anyway, the problem of the break-up peak can only be reduced using EQ or a passive circuit. And it can only be eliminated (in terms of its directional consequences) by using Be diaphragms. Good luck with your project.
Thanks awediophile.

I see the attachments in Chrome but not IE. They are hosted at diyaudio, I thought you might need to be logged in at diyaudio to be able to seem them but that doesn't seem to be necessary. I edited the previous post to replace the links to diyaudio with attachments.

I'm in agreement about the break-up. What I meant was, if it had been due to an acoustic reflection in the throat I was hopeful that some smoothing of any discontinuities there would help the reduce the peak. That looks not to be the case.

However, removing the bug screen on the DE250 and DE500 does look easier than I thought. I thought they were a metal mesh similar to those on the D220ti's. However, they are just a think plastic mesh that would be very easy to cutout. According to Geddes, he uses a little clay to fill in the gap on the DE250 and the DE500 doesn't have a gap.

I got a chance to take some measurements to compare the DE250 to the DE500 last night. Green is DE500, red is DE250. The mic distance was about 1.5 m and about 5-10 deg. off axis. Hopefully I can get some good polars soon.
Dan
Attached Images
File Type: jpg DE250_DE500.JPG (229.7 KB, 50 views)
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post #12740 of 12740 Old 08-15-2017, 02:19 PM
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Nice. While the DE500 extends higher without compensation, it's Ti diaphragm has more severe break-up and much earlier, appearing at 11-13 kHz in your measurements.
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