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post #91 of 235 Old 09-09-2012, 04:08 PM
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Do you have a minidsp?

That would be the easiest way to engineer a crossover that properly accounts for power response.

I would cross it over between 1 and 1.2k. err towards the side of 1k because i would imagine the directivity collapses near 1.2khz for the woofer.

All that matters is if you have a relatively flat response from 500hz-10khz at 0deg, 15deg, 30deg, 45deg.
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post #92 of 235 Old 09-09-2012, 04:17 PM - Thread Starter
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No, I don't have a MiniDSP, or separate power amps for that matter - I currently power my LCRs with receiver power, and its plenty for the levels I listen at - typically -10 dB - so going with passive crossover.
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post #93 of 235 Old 09-09-2012, 04:18 PM - Thread Starter
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Quote:
Originally Posted by Erich H View Post

I'm giving you the big thumbs up for trying to tackle this design. The speakers look great! Keep those pictures handy because they'll be going up on the new site once it's done.

Thanks Erich, obviously couldn't have gotten this far without all your Herculean efforts, and those of Bill and the other designers and contributors. I'll take some nicer (non-phone) pictures when they're all done. smile.gif
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post #94 of 235 Old 09-09-2012, 08:23 PM
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Looks great Brad! Great color for our theater, should disappear behind the screen. You made it look easy so far.
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post #95 of 235 Old 09-10-2012, 05:46 AM
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Nice work Brad. For a passive crossover you will also need impedance measurements. The simplest way to do that is with a WT3. The impedance measurements along with the REW measurements are the main thing needed.
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post #96 of 235 Old 09-10-2012, 08:21 AM
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Well Brad. I have some good news and some bad news. The good news is I can get the impedance files no problem. I have the waveguide and CD on hand. I also can ask Bill for it. And I'll just find the JBL impedance somehow. More good news is you did everything exactly right. I can't see a single flaw in anything you did looking at your photos and the measurements. I also have already processed the files in REW and have them ready to go in PCD.

Now, the bad news. The results have an issue.... And I don't know why. Let's take a look at what I mean.

Here I applied an 8ms gate window in REW to shut out the reflections from the ground and then screen captured the result.

rawmeasurementswithsawteethhighlighted.png

I've circled some very regular peaks and dips in the response in red using Paint. See the pattern? I don't think this is driver related. I think it's measurement related. But how, I don't know. The microphone does look close to a tree or something? Is there a reflection point somewhere near the mic? The other thing, unlikely in my opinion, is the plastic bins that the speaker is sitting on.

For now, don't sweat it. I'll work on getting the impedance files and I'll work on this assuming those peaks and dips are anomolous and see what happens. Don't drag your gear back out there until we can figure out what it is.
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post #97 of 235 Old 09-10-2012, 08:25 AM
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Coctostan, pm me your email if you want the files too.
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post #98 of 235 Old 09-10-2012, 09:23 AM
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My bet would be a close reflection or a cabinet resonance. Is the cabinet lined yet?

JSS
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post #99 of 235 Old 09-10-2012, 09:45 AM - Thread Starter
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Quote:
Originally Posted by tuxedocivic View Post

Well Brad. I have some good news and some bad news. The good news is I can get the impedance files no problem. I have the waveguide and CD on hand. I also can ask Bill for it. And I'll just find the JBL impedance somehow. More good news is you did everything exactly right. I can't see a single flaw in anything you did looking at your photos and the measurements. I also have already processed the files in REW and have them ready to go in PCD.

I like the good news. smile.gif I also downloaded PCD and loaded up the REW FR measurements, and went looking for impedence measurements to load as well - all I could find for the JBL was the embedded graph in the JBL data sheet, which I could plot and map to a data file, but not sure if that's close enough; for the SEOS/360, I saw this thread on diysoundgroup, but didn't see any ZMA files in the zip file: http://www.diysoundgroup.com/forum/index.php?topic=56.0.
Quote:
Now, the bad news. The results have an issue.... And I don't know why. Let's take a look at what I mean.
Here I applied an 8ms gate window in REW to shut out the reflections from the ground and then screen captured the result.
rawmeasurementswithsawteethhighlighted.png
I've circled some very regular peaks and dips in the response in red using Paint. See the pattern? I don't think this is driver related. I think it's measurement related. But how, I don't know. The microphone does look close to a tree or something? Is there a reflection point somewhere near the mic? The other thing, unlikely in my opinion, is the plastic bins that the speaker is sitting on.
For now, don't sweat it. I'll work on getting the impedance files and I'll work on this assuming those peaks and dips are anomolous and see what happens. Don't drag your gear back out there until we can figure out what it is.

Right, as I mentioned the back yard is not ideal for doing outdoor measurements, its not very big to begin with (lot is like 55' wide, with that planter box right smack in the middle. About 10' behind the mic is a dog ear fence, so about 16' from the speaker; maybe 20' to the right is the house; 15' or so to the left is the garaage, door was open, but still some obstructions; a couple feet back from the mic were a couple more of those storage bins where I had the test gear set up (laptop, etc.); MDF under the top box right under the enclosure was sticking out a couple inches as well; there's the table top ~2.5-3' below the speaker; and of course me pushing the button and then hiding off to the side. tongue.gif

Re: maxmercy's comment, the box is not lined yet, and my bracing is fairly minimal (one side to side and one front to back brace between woofer and waveguide).
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post #100 of 235 Old 09-10-2012, 09:58 AM
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Hopefully you weren't standing behind the microphone with that laptop......  ;)

 

If they were reflections you should see sharp group delay swings at the dips right?  How does group delay look?

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post #101 of 235 Old 09-10-2012, 10:06 AM - Thread Starter
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Quote:
Originally Posted by NicksHitachi View Post

Hopefully you weren't standing behind the microphone with that laptop......  wink.gif

If they were reflections you should see sharp group delay swings at the dips right?  How does group delay look?

Haha, no, I would push the button, and then wander off to the side somewhere - but the boxes were there - would have left the laptop and stuff on the ground, but my mic cable wasn't long enough for that to work with the boom fully extended.

I'll check on group delay when I'm back home - not that I'd know what to look for, but I'll check it rolleyes.gif
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post #102 of 235 Old 09-10-2012, 10:40 AM
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I thought it might be the enclosure when I first looked at the woofer, but the tweeter has it as well. Your back yard is fine. It's not that at all. What we're seeing would be something nearby, within a couple ms. So like a couple feet. If there wasn't anything, then the other issue may have been electrical. Coctostan mentioned this in his PM to me. I thought that this morning but the pattern doesn't align with any multiple of 60hz. But I still think that might be it. Was your laptop plugged in, or using battery? Anybody with more electrical knowledge than me know about this stuff?

Looking at the files in PCD, I think we'll manage for a first run sim. Depending how that goes, you just might want to measure the first run sim and the raw drivers again. It'll be fine for now smile.gif
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post #103 of 235 Old 09-10-2012, 10:59 AM - Thread Starter
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Quote:
Originally Posted by tuxedocivic View Post

I thought it might be the enclosure when I first looked at the woofer, but the tweeter has it as well. Your back yard is fine. It's not that at all. What we're seeing would be something nearby, within a couple ms. So like a couple feet. If there wasn't anything, then the other issue may have been electrical. Coctostan mentioned this in his PM to me. I thought that this morning but the pattern doesn't align with any multiple of 60hz. But I still think that might be it. Was your laptop plugged in, or using battery? Anybody with more electrical knowledge than me know about this stuff?

As far as something nearby, on top of the stack of storage containers, and just below the speaker, I placed a scrap of MDF with a towel over it, for the speaker to sit on, for stability - it protruded a couple inches from the baffle, so that's a possibility. With that pushed back, I was worried the tower would tip over, as it was a little windy.

The laptop and the other gear was plugged into a cheapo power strip, so that could be a weak link I suppose.
Quote:
Originally Posted by tuxedocivic View Post

Looking at the files in PCD, I think we'll manage for a first run sim. Depending how that goes, you just might want to measure the first run sim and the raw drivers again. It'll be fine for now smile.gif

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post #104 of 235 Old 09-10-2012, 04:02 PM
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Any answers if the ETC or impulse response is posted for each? May give a clue as to the reflection's presence......

JSS
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post #105 of 235 Old 09-10-2012, 07:16 PM
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post #106 of 235 Old 09-10-2012, 08:10 PM - Thread Starter
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Just looked at an ETC myself, I saw three prominent spikes at roughly:

8.2 ms - 2.82 meters - 9.252 ft- 1/2 wavelength = 4.6 ft
22.1 ms - 7.6 meters - 24.9344 ft= 12.5 ft
24.7 ms - 8.5 meters - 27.8871 ft= 13.95 ft

the last two roughly correspond to the distance from the mic to the fence and back.

Those spikes show up prominently on measurements of the tweeter alone, but not for the woofer - I guess because HF travels more like a ray? and because I swept 20-5000 for woofers, 500-20000 for tweeters, and then 20-20000 for both in parallel - kind of stupid really, but I started that way, thinking I didn't want to risk damaging the CDs, realized halfway through that it was stupid because I did full range when combined anyway, but wanted to be consistent throughout the measurements, so kept it that way.
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post #107 of 235 Old 09-10-2012, 08:27 PM
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I still think this may be a cabinet issue. What are the final internal dims of the cabs? If two of those dims is near ~15", there may be some lining of the cabs that fixes it. There are no really deep suckouts save for around 440Hz in the non-gated graph...but everything should be double-checked. That is also a pretty reflective environment per the pics....hard to say.

JSS
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post #108 of 235 Old 09-10-2012, 08:31 PM - Thread Starter
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Thanks max - interior dimensions are 26 h x 16 w x 14.5 d
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post #109 of 235 Old 09-10-2012, 09:28 PM
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I think you should do a close mic of woofer and while at it do the HF as well. It can be done indoors so you don't need to drag everything outside again.

You only need to get the speaker off the ground (on a table) and put the mic about 4-6" or so directly in front of the driver. That should be able to rule out internal cabinet reflections.
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post #110 of 235 Old 09-10-2012, 09:40 PM
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quite windy you say? might be a factor. ill also say I have a pretty mean ground loop hum when I have my laptop plugged in, anywhere, it doesnt have to be on the same line. I cant even do measurements with it plugged in, have to go all battery. just my .02

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post #111 of 235 Old 09-11-2012, 05:49 AM
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Are you using Chirp (sweep) or MLS? If you have a choice go with a log sweep. MLS has problems with wind, distortion, and timing variations.

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post #112 of 235 Old 09-11-2012, 07:17 AM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post

I think you should do a close mic of woofer and while at it do the HF as well. It can be done indoors so you don't need to drag everything outside again.
You only need to get the speaker off the ground (on a table) and put the mic about 4-6" or so directly in front of the driver. That should be able to rule out internal cabinet reflections.

Thanks, I'll do that this evening and post the results.
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quite windy you say? might be a factor. ill also say I have a pretty mean ground loop hum when I have my laptop plugged in, anywhere, it doesnt have to be on the same line. I cant even do measurements with it plugged in, have to go all battery. just my .02

It was more a confluence of ambient noise that I had to deal with - fire trucks, lawnmowers and leaf blowers, small plane flyovers, wind - intermittent though, I think I managed to dodge most of it all when I measured. I'll try comparing AC and battery on a measurement and see what shows up.

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Originally Posted by bwaslo View Post

Are you using Chirp (sweep) or MLS? If you have a choice go with a log sweep. MLS has problems with wind, distortion, and timing variations.

Checked REW, but couldn't find any setting for Chirp or MLS, just doing a standard sweep.
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post #113 of 235 Old 09-11-2012, 08:42 AM
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Quote:
Originally Posted by maxmercy View Post

I still think this may be a cabinet issue. What are the final internal dims of the cabs? If two of those dims is near ~15", there may be some lining of the cabs that fixes it. There are no really deep suckouts save for around 440Hz in the non-gated graph...but everything should be double-checked. That is also a pretty reflective environment per the pics....hard to say.
JSS

I measured my DNA-350 yesterday and it had similar wrinkles. So maybe this is it.
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post #114 of 235 Old 09-11-2012, 08:47 AM
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Brad,

The almost finished products look terrific
For the next question; please understand I am a newbie and have only been skimming along.

For those outdoor measurements:
Do I assume you made those "characterization graphs without a crossover in use?

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post #115 of 235 Old 09-11-2012, 09:25 AM - Thread Starter
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Thanks Craig - yes, per instructions from tuxedocivic (who has graciously offered to help me with crossover design), I measured the drivers mounted in the cabinet, with no crossover: woofer alone, tweeter alone, and both in parallel.
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post #116 of 235 Old 09-11-2012, 04:58 PM
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I'll pm you some details tomorrow. This is just to make you salivate a little. tongue.gif
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post #117 of 235 Old 09-11-2012, 05:03 PM - Thread Starter
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post #118 of 235 Old 09-11-2012, 08:29 PM - Thread Starter
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close mic'd:

w-close.png

t-close.png

Dip at 2.7K is strange - maybe one of the electronic devices in the chain (amp?) is sucky?

Edit: doesn't seem like, since I used the same equipment for measuring my TLAHs, and don't see that 2.7K dip.
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post #119 of 235 Old 09-11-2012, 09:27 PM
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Some of the dips look to appear in both sweeps, I think it is time to line the cabs with some dampening material.

The dip at 2.7k is weird, close proximity causing some sort of extra cancellation?
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post #120 of 235 Old 09-12-2012, 10:12 AM
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Quote:
Originally Posted by mtg90 View Post

Some of the dips look to appear in both sweeps, I think it is time to line the cabs with some dampening material.

Yes, the cone is partially transparent to internal reflections.

Noah
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