skywave-rider
Slumming in Akihabara
Very interesting, Jack. I didn't realize that and didn't obviously try the L-pad at all settings. This is an example of how RTA is very useful because you can see adjustments in real time change in the readout.
Zilch's AK Design Collaborative - Econowave Speaker
- Thread starter Zilch
- Start date
Very interesting, Jack. I didn't realize that and didn't obviously try the L-pad at all settings. This is an example of how RTA is very useful because you can see adjustments in real time change in the readout.
jackgiff
Well-Known Member
I think this Project is finished.
This is my first pass at using Zobels, and everything I read says that they are pretty forgiving. I used my Zobel calculator to come up with values for a Zobel based on the Re and Le of the Dayton DC300 woofer. It said that 42 microfarads and 8 ohms would do the deed. I didn't have any 42 mic's laying about, but did have a pair of 20's, so they were paralleled and an 8 ohm added. Corrected the bump at the woofers upper end way too much. A bit of experimenting yielded a 20 Microfarad and 20 ohms.
The picture shown has the woofer with no Zobel as the upper FR. The middle one is with 20 microfarads and 20 ohms across the woofer. The bottom is the resulting FR of the system.
Not bad at all for smooth, except for the hump at around 100 Hz and less. The Zobel may not be perfect, but is certainly within hailing distance of exemplary.
This is my first pass at using Zobels, and everything I read says that they are pretty forgiving. I used my Zobel calculator to come up with values for a Zobel based on the Re and Le of the Dayton DC300 woofer. It said that 42 microfarads and 8 ohms would do the deed. I didn't have any 42 mic's laying about, but did have a pair of 20's, so they were paralleled and an 8 ohm added. Corrected the bump at the woofers upper end way too much. A bit of experimenting yielded a 20 Microfarad and 20 ohms.
The picture shown has the woofer with no Zobel as the upper FR. The middle one is with 20 microfarads and 20 ohms across the woofer. The bottom is the resulting FR of the system.
Not bad at all for smooth, except for the hump at around 100 Hz and less. The Zobel may not be perfect, but is certainly within hailing distance of exemplary.
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I'm less concerned about what's happening with DC300 at 80 Hz, which can be adjusted with box tuning, once we characterize it accurately and decide what is desired, than with the 5 dB "hump" between 800 Hz and 2 kHz, clearly shown in your curves just above, smack in the middle of the target acoustic crossover region. I don't believe the highpass can be finalized until that is mitigated, and I suspect it can be done just by adjusting the lowpass components, as was done with LE14A.
With respect to the HF comp, we understand it differently. By my view, C3 sets a fundamental 6 dB/octave slope beginning at some frequency above 20 kHz according to the impedance of the driver; a lower value starts that sloping downward at a higher frequency, establishing the overall attenuation in the frequency range of interest. R1 varies the slope, and thus the compensation and attenuation simultaneously. I do not understand the role of R2 entirely, but he explains that in his tutorial, which I will review again.
In any case, here is his attenuation chart and the results I got using those values with Selenium D220Ti on the JBL waveguide and the eWave highpass, as posted earlier in this thread:
http://www.audioroundtable.com/PiSpeakers/messages/1278.html
The discussion begins ~Page 140 in this thread. Notes from Wayne:
1) He chooses R2 in combination with the basic highpass filter such that the rolloff is underdamped. Looks like we may need some of that.
2) He cautions that an L-pad may not be the optimum means for accomplishing attenuation. We want one, and optimize accordingly. For any given C3 value, it's clear that his R1/R2 selections generate slightly different curves. 16/16/0.47 is one of those on his chart, -10 dB. When I do this, it's with the L-pad at mid level or above to establish the desired attenuation, and the curve is always different in detail when it is set to Max, i.e., effectively out of the circuit.
I should repeat that study with the DE250 on QSC waveguide to see where we are by comparison....
With respect to the HF comp, we understand it differently. By my view, C3 sets a fundamental 6 dB/octave slope beginning at some frequency above 20 kHz according to the impedance of the driver; a lower value starts that sloping downward at a higher frequency, establishing the overall attenuation in the frequency range of interest. R1 varies the slope, and thus the compensation and attenuation simultaneously. I do not understand the role of R2 entirely, but he explains that in his tutorial, which I will review again.
In any case, here is his attenuation chart and the results I got using those values with Selenium D220Ti on the JBL waveguide and the eWave highpass, as posted earlier in this thread:
http://www.audioroundtable.com/PiSpeakers/messages/1278.html
The discussion begins ~Page 140 in this thread. Notes from Wayne:
1) He chooses R2 in combination with the basic highpass filter such that the rolloff is underdamped. Looks like we may need some of that.
2) He cautions that an L-pad may not be the optimum means for accomplishing attenuation. We want one, and optimize accordingly. For any given C3 value, it's clear that his R1/R2 selections generate slightly different curves. 16/16/0.47 is one of those on his chart, -10 dB. When I do this, it's with the L-pad at mid level or above to establish the desired attenuation, and the curve is always different in detail when it is set to Max, i.e., effectively out of the circuit.
I should repeat that study with the DE250 on QSC waveguide to see where we are by comparison....
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That's looking much improved and mighty good, Jack, and I suspect sounding so, as well.... :thmbsp:
Is that with R1 = 30 Ohms or 16?
Where is the acoustic crossover frequency now?
What happens as you vary the L-pad?
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jackgiff
Well-Known Member
That is with the standard <95 db crossover which has 30 ohm R1, and 16 ohm R2, with .47 microfarad C3. The acoustic crossover is still around 1.6 KHz. The Zobel didn't greatly affect the crossover frequency, just the amplitude of the woofer. As the L-Pad is varied, the HF signal is pretty constant, just changing levels.
Why don't you get your QSC/B&C combo on a baffle and see if it matters.
I haven't read all of Wayne's papers, but remember that he doesn't use L-Pads, so he doesn't have to worry about L-Pad setting changes, since it isn't there. He may have reason to change the values of R2, but if it is used with an L-Pad, that changes things. And if the attenuation resistor and compensation capacitor are installed in front of the hi pass filter as was done in the 18 Sound paper, R2 is not necessary since the attenuation/compensation is working at the very low impedance of the amplifier output.
Oh, and it does sound very nice. The B&C may not go all the way to 20 KHz, but I can't hear anything up there. It does sound a bit more pleasant than a Selenium D220Ti, but at three times the price, it really should.
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Russellc
Addicted Member
As I recall it sets the dampening, which somehow determines the "shelf" (for lack of a better word) the response just before the compensation begins. I guess I'll re read too......
Russellc
DENNYDOG
Addicted Member
I just got a call from QSC today and they said the waveguides will be on back order for 6-8 weeks. That sucks as I've been waiting about two weeks already.
Sounds like I need to order the rest of the parts from Parts Expres and the crossover board from Zilch so I have everything ready to go when they get here.
Sounds like I need to order the rest of the parts from Parts Expres and the crossover board from Zilch so I have everything ready to go when they get here.
It's déjà vu.
Like JBL, QSC Parts management needs to adapt to "unanticipated demand" for these waveguides, and it'll take them a while to get up to speed. Hopefully, someone is paying attention there.... :yes:
Floral Rings
Member RoyC suggested a convenient means for adapting the woofer cutout in the PE KD Trap cabinets to use 10" woofers:
http://www.audiokarma.org/forums/showpost.php?p=3010602&postcount=7001
My local Michael's had no clue what I was talking about, so I ordered direct, 12 rings to my door for $27.85, here shown mounting DC250, a perfect fit:
They may be stacked in 1/4" increments to any depth once glued to the rear of the baffle allowing roundover of the opening. There are eight #8 clearance holes which must be filled or used for that purpose....
Member RoyC suggested a convenient means for adapting the woofer cutout in the PE KD Trap cabinets to use 10" woofers:
http://www.audiokarma.org/forums/showpost.php?p=3010602&postcount=7001
My local Michael's had no clue what I was talking about, so I ordered direct, 12 rings to my door for $27.85, here shown mounting DC250, a perfect fit:
They may be stacked in 1/4" increments to any depth once glued to the rear of the baffle allowing roundover of the opening. There are eight #8 clearance holes which must be filled or used for that purpose....
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Russellc
Addicted Member
Member RoyC suggested a convenient means for adapting the woofer cutout in the PE KD Trap cabinets to use 10" woofers:
http://www.audiokarma.org/forums/showpost.php?p=3010602&postcount=7001
My local Michael's had no clue what I was talking about, so I ordered direct, 12 rings to my door for $27.85, here shown mounting DC250, a perfect fit:
They may be stacked in 1/4" increments to any depth once glued to the rear of the baffle allowing roundover of the opening. There are eight #8 clearance holes which must be filled or used for that purpose....
Good show, I wondered how that idea would work. It seems, at least based on rates of collapsing directivity with increasing frequency, that 10 inch should be the premier size for E'wave......are there any good HE 10 inchers that can produce 40 hz @ 3db down? By good, I mean JBL quality. Assuming what the answer will be, it seems like I may have to drift to E'waves that need subs, a setup of 3 smaller subs like Wayne suggests?
Russellc
skywave-rider
Slumming in Akihabara
The 8" Daytons I have go down a lot lower in a .9 cu ft box than my JBL 123A1s in the PE Trapbox. Not JBL quality though. 
Maybe it's just me, Russell, but I think you are looking at AE 10" woofers. That's the rumor, people are talking.
Maybe it's just me, Russell, but I think you are looking at AE 10" woofers. That's the rumor, people are talking.
Bauhausler
Rational Subjectivist
I'm presently doing a 2-box 3-way setup. I used a small midwoofer (Kef B110) and the JBL 6" X 6" waveguide in 7L cabinets for the satellites. The goal was to achieve the waveguide's dispersion with as little center-to-center distance as possible (5.5" in this case) and easier positioning than a big floorstanding cabinet. I cross to the sub cabs at 150 hz. This requires biamping and at the moment, a line level crossover to the sub cabs. I get great low bass and easy positioning of the mid/high units for optimum height/angle to the listener. There are advantages to a 2-way single cabinet system, but positioning usually isn't one of them. Cabinets big enough to get the treble unit up to seated ear height are really bulky and heavy. My room is full of furniture and tweeters at the knees really doesn't work here.
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jackgiff
Well-Known Member
That is what the L-Pad is for. Some people like to have just the attenuation/compensation and no L-Pad. If that were to be the case. the attenuation resistor would have to be chosen to drop the excess (19 dB) and the other values calculated to suit.
I like to be able to vary the HF response of a speaker, both for setting it to suit it's environment, and just because sometimes I want to raise or lower it. Can't do that easily with fixed values.
The EconoWave only has two basic attenuation/compensation networks, and the values are selected to keep the HF flat as the L-Pad is varied. Therefore one of them will suit almost any woofer. The DC300 based speaker in my project utilizes an L-Pad because it will probably be built with many other woofers.
Russellc
Addicted Member
The 8" Daytons I have go down a lot lower in a .9 cu ft box than my JBL 123A1s in the PE Trapbox. Not JBL quality though.
Maybe it's just me, Russell, but I think you are looking at AE 10" woofers. That's the rumor, people are talking.
I hadnt thought of that one! I've been leering at the 12 and 15 inch, didnt occur to me they may have a 10 incher as well!:sigh:
russellc
skywave-rider
Slumming in Akihabara
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HatchetJack
Chillin' The Most
You guys are great with all the tech and curves but I will throw in my 2 cents
on the ones I have listened to. The first pair I built with the hpm 100's are my
mains and sound terrific but still have the trait of wanting to be pushed to
louder volumes before the woofer really comes into its own like the originals and
would be more suited to an XL room or basement. A friend built with the
12" Dayton classics and I dont know if you could tell them apart in a blind
test. Both are great but my second pair built with the 10" Dayton classics are
just so sweet in my brothers living room hooked to a 20 watt Marantz 2220b
receiver it should be against the law. Great at low volumes and will blow you
away if needed with just the right warmness to keep you interested for
extended listening sessions. When I build a third pair it will be the 10 classic
for sure. Better woofers are out there I'm sure and could be swapped in
later but for about 26 bucks each, that little 10" classic is a bargain.
on the ones I have listened to. The first pair I built with the hpm 100's are my
mains and sound terrific but still have the trait of wanting to be pushed to
louder volumes before the woofer really comes into its own like the originals and
would be more suited to an XL room or basement. A friend built with the
12" Dayton classics and I dont know if you could tell them apart in a blind
test. Both are great but my second pair built with the 10" Dayton classics are
just so sweet in my brothers living room hooked to a 20 watt Marantz 2220b
receiver it should be against the law. Great at low volumes and will blow you
away if needed with just the right warmness to keep you interested for
extended listening sessions. When I build a third pair it will be the 10 classic
for sure. Better woofers are out there I'm sure and could be swapped in
later but for about 26 bucks each, that little 10" classic is a bargain.