Ah.
Yea, i am curious about how a 2431h would measure on the older pt waveguide vs the newer more conical pt.
Dualtriode, yea it does look a bit fuzzy.
I think patrick was thinking about the same thing, the phase plug, let alone a mismatch taper rate from in compression driver to horn mouth. Micro resonances, wonder if it is audible.
Yea, i am curious about how a 2431h would measure on the older pt waveguide vs the newer more conical pt.
Dualtriode, yea it does look a bit fuzzy.
I think patrick was thinking about the same thing, the phase plug, let alone a mismatch taper rate from in compression driver to horn mouth. Micro resonances, wonder if it is audible.
I'm not sure what the Z plots mean.
In a direct radiator or speaker in a box, wrinkles show up that are usu ally resonances that ring, also seen on a waterfall plot.
Just reminds me how upset a passive crossover gets dealing with a changing load.
The 2342 is a pretty gooid horn (opinion from djk).
In a direct radiator or speaker in a box, wrinkles show up that are usu ally resonances that ring, also seen on a waterfall plot.
Just reminds me how upset a passive crossover gets dealing with a changing load.
The 2342 is a pretty gooid horn (opinion from djk).
Hello All,
About impedance plots there is still more to know. At the mechanical resonance of the diaphragm / and associated surround you expect to see a resonance peak, a primary resonance, much like a cone driver in air. Attach the compression driver to a horn or waveguide, there will be additional shapes, dimensions or air volumes that also have resonate qualities of their own. These primary, secondary resonances and reflections will color the sound quality of the CD / Waveguide. The impedance plot will also mirror the upper octave(s) breakup of the CD diaphragm. No amount of boost or equalization can correct for the color added by resonance, reflection or CD diaphragm breakup. If you boost excessively in an effort to compensate for the mass breakpoint roll off you are likely only getting louder CD diaphragm breakup.
At this point I like using a 10 or 8 inch mid-range cone to control directivity and using a LR 24dB crossover to the CD / waveguide above the ugly resonance peaks. I also like the lack of CD diaphragm breakup in the JBL 2425 family CD’s.
Thanks DT
About impedance plots there is still more to know. At the mechanical resonance of the diaphragm / and associated surround you expect to see a resonance peak, a primary resonance, much like a cone driver in air. Attach the compression driver to a horn or waveguide, there will be additional shapes, dimensions or air volumes that also have resonate qualities of their own. These primary, secondary resonances and reflections will color the sound quality of the CD / Waveguide. The impedance plot will also mirror the upper octave(s) breakup of the CD diaphragm. No amount of boost or equalization can correct for the color added by resonance, reflection or CD diaphragm breakup. If you boost excessively in an effort to compensate for the mass breakpoint roll off you are likely only getting louder CD diaphragm breakup.
At this point I like using a 10 or 8 inch mid-range cone to control directivity and using a LR 24dB crossover to the CD / waveguide above the ugly resonance peaks. I also like the lack of CD diaphragm breakup in the JBL 2425 family CD’s.
Thanks DT
Hello,
I have a 90% level of confidence. I have an open mind.
If you cut with your equalizer to flatten your frequency response it still rings just not as loud.
If I put my mind to thinking of exceptions I come up with active breaking, something like negative amplifier output impedance. That would be the exception not the rule.
What do you have?
Thanks DT
Sometimes the resulting response is an indicator that the problem is fixed, other times EQ cannot fix the problem.
For example say you build an amp, and the output transformer has a self resonance at the top end. You sort out the response. What does the phase look like?
On the other hand you have a wall reflection, and in combination with the direct sound you have a resonance, but this is unique for this point in space and it cannot be undone by EQ.
For example say you build an amp, and the output transformer has a self resonance at the top end. You sort out the response. What does the phase look like?
On the other hand you have a wall reflection, and in combination with the direct sound you have a resonance, but this is unique for this point in space and it cannot be undone by EQ.
So, the z peak at 1,600hz using the pth1010hf-1 horn, that is probably horn length (mouth to diaphram distance).
I know that horn is 3" deep, or 1/4 wavelength of near 1,100hz.
Seeing that it is basically conical but rounded throat and rounded at mouth to baffle, i think it may not load as well down lower (people say about conicals, drooping at low end), but less horn reflections are most important to me. I was hoping to get flat response on that horn to near 1.2khz for crossing to a 12.
Ideally the horn loads down maybe 1/2 octave below crossover point, but using 24db lr, you are already 6db down at x-over point and rolling fast, so it may not be an issue.
I'm excited for freq response charts.
I've always used boost, 90db is 90db, fractions of a watt is still fractions of a watt.
And yea, resonances can be eq'd flat but still ring in time, and sub harmonics sneak around a notch and the cone rings again.
2342 is a little deeper ?
Actually, that horn is similar to the older pt horn, except the pt doesn't have a diffraction slot. I like it blocks the compression driver less than the 2344, little peak past 4khz though. Resonances in driver make horn freq response look like resonance resonance resonance.
If you want to drop the cash, the 2435hpl is nice, beryllium diaphram.
I found an interesting jbl horn, marked for japan as 4400 line, less vulgar than the butt crack horns.
Jbl 4425 Mk2
I know that horn is 3" deep, or 1/4 wavelength of near 1,100hz.
Seeing that it is basically conical but rounded throat and rounded at mouth to baffle, i think it may not load as well down lower (people say about conicals, drooping at low end), but less horn reflections are most important to me. I was hoping to get flat response on that horn to near 1.2khz for crossing to a 12.
Ideally the horn loads down maybe 1/2 octave below crossover point, but using 24db lr, you are already 6db down at x-over point and rolling fast, so it may not be an issue.
I'm excited for freq response charts.
I've always used boost, 90db is 90db, fractions of a watt is still fractions of a watt.
And yea, resonances can be eq'd flat but still ring in time, and sub harmonics sneak around a notch and the cone rings again.
2342 is a little deeper ?
Actually, that horn is similar to the older pt horn, except the pt doesn't have a diffraction slot. I like it blocks the compression driver less than the 2344, little peak past 4khz though. Resonances in driver make horn freq response look like resonance resonance resonance.
If you want to drop the cash, the 2435hpl is nice, beryllium diaphram.
I found an interesting jbl horn, marked for japan as 4400 line, less vulgar than the butt crack horns.
Jbl 4425 Mk2
Attachments
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Hello,
In the history of JBL things there was a move away from 4 and 3 way monitors to 2-way. JBL was dropping market share then came out with smaller 2-way monitors that fit better into the control rooms of the day (early 1980’s). Then and now the passive XO’s and equalization is crafted to work with 2-way monitors with CD / waveguide impedance peaks included in the passband.
In the back of head I suspect that the M2 DSP XO EQ network includes active damping of the included CD / waveguide impedance peaks. The D2 driver has really clean upper octaves. I suspect that even cutting edge DSP corrections cannot fix diaphragm breakup.
My impression is that Diana Krall vocal and piano is much more real with a cone midrange in the speaker stack.
YouTube
I am anxious to do frequency response testing too, need the time.
Thanks DT
Well if you include the passive network that is part of the design that when you put between the amp and the driver just makes them all kinda go away?
http://www.jblproservice.com/pdf/M2_Studio_Monitor/M2_tech_manual.pdf
Rob
Meaning a 3-way ?
I bet you would get a kick out of horn loaded mids, but they get big.
Yea, i've looked close at their stuff, especially waveguides, seeing how horn loaded domes seem to be best now, very reflection free. I wish they'd wrap horn mouth with felt or foam even, but whatever. Genlec, behringer truth, but small 8" 2-way that would get lost in my room, especially cranking a movie.
I've loved double 15s crossing @750hz (f3 near 30hz, shorting rings), but my setup is better except for sheer slam (that I miss).
I'm thinking double 12 (delta pro 12a) crossing 1.2khz to either my pt or the newer pt waveguide. It would get the tweet around ear level and should thump good, having a lower f3 than my current qts .3 and fs 50hz making f9 near fs. Bass knob UP !!!!!
I agree that passive XO’s and EQ can do a lot to compensate for primary resonance. Make it completely go away I doubt that? The impedance peaks will still ring, just not as loud.
I think that the D2 CD was carefully crafted and tuned to largely eliminate diaphragm breakup of the upper audio band. Two smaller diaphragms are much more breakup immune than a single larger one. The D2 CD does not have any diaphragm breakup that needs fixing.
Thanks Rob and Props to you for all your work with passive networks. I know that at a certain point we call a project good, screw the back panel on the cabinet and listen to the music.
Tomorrow I will start over again and do a frequency sweep looking for phase shift. I guess a monkey brain with toys.
Thanks DT
Norman,
You are designing bigger than me.
We are selling / downsizing the house. The HT is going going gone.
My project is a pair of main monitors in the 3 to 4 cubic foot range and a couple of subs for end tables.
Yes 3 ways. I have been trying out 2108's, 2123’s and 2119’s for the mid-range. I think that the 8 inch 2119’s are winning out with the higher XO frequency, controlled directivity and size. I am trying to screw the back panel on this project and call it good.
Thanks DT
Hello All,
I have had a little inertia getting started on the exam of the D2 / M2 CD waveguide. I looked around locally to find a shop that would install the metal thread inserts; they are all too busy making money doing less custom things. So I went to Amazon and ordered #10 Heilcoil metal thread inserts for the M2 waveguide to install the CD attachment flange. The Helicoil thread inserts were an easy install. A drill bit was not required. I just taped the existing holes in the waveguide with the tap that is provided in the Helicoil kit.
Going in I have the impression that the “revolutionary” M2 performance is largely attributable to software and Digital Signal Processing not just the new technology drivers. “The M2 contains no internal crossover network; it must be used with BSS Omnidrive HD Digital Signature processing to provide proper integration of the speaker’s low-frequency and high-frequency transducers.” * The RC network inside the M2 is a high pass filter / attenuator to block low frequencies that would damage the expensive D2 CD’s. The DSP XO’s operate above the single pole high pass protection filter cutoff frequency.
* https://www.jblpro.com/ProductAttachments/M2_OwnersManual_RevA.pdf top of page number 4
I have the D2 CD’s attached to the M2 waveguides and sitting on top of the speaker stacks in place of the JBL 4342 80’s vintage waveguides. These D2 / M2 waveguides play a little bigger, 120 degrees H X 100 degrees V, than the older waveguides. These speakers are equalized with a Rane Real Time Analyzer and 30 band equalizer. The speakers are tri-amped with active line level XO’s. This is old school, no DSP yet. No capacitors, inductors or resistors are installed between the amplifier outputs and the driver inputs.
The 30 band equalizer was set flat, 40 to 20KHz, recorded the position of the band sliders then set up a spread sheet and calculated new band slider positions to set the balance tilting down 1 dB per octave. The bass sliders went up a little the high frequencies went down a little and the sliders in the center did not move much.
Rob and All,
If there are resonate peaks in the M2 waveguide output they disappear, I do not hear them In a week or so I will put in ear plugs and do some plots.
The 100 degree ish controlled dispersion in my listening space sounds really good to my ears and brain.
Thanks DT
I have had a little inertia getting started on the exam of the D2 / M2 CD waveguide. I looked around locally to find a shop that would install the metal thread inserts; they are all too busy making money doing less custom things. So I went to Amazon and ordered #10 Heilcoil metal thread inserts for the M2 waveguide to install the CD attachment flange. The Helicoil thread inserts were an easy install. A drill bit was not required. I just taped the existing holes in the waveguide with the tap that is provided in the Helicoil kit.
Going in I have the impression that the “revolutionary” M2 performance is largely attributable to software and Digital Signal Processing not just the new technology drivers. “The M2 contains no internal crossover network; it must be used with BSS Omnidrive HD Digital Signature processing to provide proper integration of the speaker’s low-frequency and high-frequency transducers.” * The RC network inside the M2 is a high pass filter / attenuator to block low frequencies that would damage the expensive D2 CD’s. The DSP XO’s operate above the single pole high pass protection filter cutoff frequency.
* https://www.jblpro.com/ProductAttachments/M2_OwnersManual_RevA.pdf top of page number 4
I have the D2 CD’s attached to the M2 waveguides and sitting on top of the speaker stacks in place of the JBL 4342 80’s vintage waveguides. These D2 / M2 waveguides play a little bigger, 120 degrees H X 100 degrees V, than the older waveguides. These speakers are equalized with a Rane Real Time Analyzer and 30 band equalizer. The speakers are tri-amped with active line level XO’s. This is old school, no DSP yet. No capacitors, inductors or resistors are installed between the amplifier outputs and the driver inputs.
The 30 band equalizer was set flat, 40 to 20KHz, recorded the position of the band sliders then set up a spread sheet and calculated new band slider positions to set the balance tilting down 1 dB per octave. The bass sliders went up a little the high frequencies went down a little and the sliders in the center did not move much.
Rob and All,
If there are resonate peaks in the M2 waveguide output they disappear, I do not hear them In a week or so I will put in ear plugs and do some plots.
The 100 degree ish controlled dispersion in my listening space sounds really good to my ears and brain.
Thanks DT
Sub < 60Hz M&K double 12inch
Woofer 40Hz to 400Hz Jbl2204H
Mid 400Hz to 2000Hz JBL 2119H
Tweeter 2000Hz to 20KHz JBL D2 CD / M2 waveguide
Active crossover Rane AC23S 24dB LR slopes
D2 CD and M2 waveguide are the real deal.
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m&k, nice.Not so different a setup to what I'm after. Are you using the 2119H as midrange because you had it or you purchased it for this project? I'm looking into 8" with the same xo points as you.
Hi DT looking forward to your D2/M2 measurements. For the JBL M2, the XO to the D2 is just under 800 Hz. The BSS device provides the XO and a bunch of eq that you can see user pos has reversed engineered and can be applied using different tech than the BSS: JBL M2 crossover - Google Docs
Some folks have used Audiolense software DSP with the M2 using digital XO with good results: JBL M2 Audiolense Digital Crossovers w/Subs | Audio Science Review (ASR) Forum
That D2 is a very nice CD. I had a BMS 4540nd ring radiator on a QSC waveguide and remembering it as the nicest CD top end I have heard. The D2 should even be better with the capability to go lower...
I also run a triamp setup and would recommend using protection capacitor on your D2, just in case... http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=49454&d=1295365145
Some folks have used Audiolense software DSP with the M2 using digital XO with good results: JBL M2 Audiolense Digital Crossovers w/Subs | Audio Science Review (ASR) Forum
That D2 is a very nice CD. I had a BMS 4540nd ring radiator on a QSC waveguide and remembering it as the nicest CD top end I have heard. The D2 should even be better with the capability to go lower...
I also run a triamp setup and would recommend using protection capacitor on your D2, just in case... http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=49454&d=1295365145