camplo, the response in the top octave is extended, but a bit ragged, which can be smoothed out with eq. I get to -3 dB at 20 kHz. Thankfully it is a low distortion device, so sounds detailed and smooth. You can hear the comparo to the Kef's in the link.
I am sure I linked this before, but member notnyt measured and compared a bunch of JBL CD's, including one with Be dia loaded: Just purchased a pair of JBL 4722n speakers. - Page 129 - AVS Forum | Home Theater Discussions And Reviews
I am happy with the response with the 2453H-SL. Now if I can only find a better waveguide
Based on my experience with Kinoshita (Beryllium) and JBL (Aquaplas), I would say the strength of the 4” Aquaplas is not the top octave.
Aquaplas diaphragm has a distinctive tight sound due to its damped metal structure, and its top is less bright and less airly than the other metal diaphragm drivers, including uncoated titanium and Beryllium. The good thing about it is, it has less metal signature, slightly a bit more paper like, so the transition to the paper cone woofer is more natural than the other metal diaphragms to my ears. I feel that TAD Beryllium is cleaner and airlier, and has almost no signature by itself, but it's midrange is less meaty than Aquaplas. I think some would say Beryllium horn driver has the same signature as Beryllium / Diamond dome tweeters.
Ribbon is also clean ands airly. I have seen many people add ribbon super tweeter to Aquaplas, and I think its pretty reasonable. Softdome is always great, nothing wrong, a little boring nice guy.
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Plasnu, that's a nice description.
Never did a direct comparison, but yours makes perfect sense.
Jzagaja experimented with Aquaplas on cheap 3" Titanium diaphragms in the past .
Sometimes, the 'body' and paper like signature of Aquaplas may even be preferable to the transparancy of Beryllium.
For example if you listen to less then stellar recordings at higher SPLs.
Never did a direct comparison, but yours makes perfect sense.
Jzagaja experimented with Aquaplas on cheap 3" Titanium diaphragms in the past .
Sometimes, the 'body' and paper like signature of Aquaplas may even be preferable to the transparancy of Beryllium.
For example if you listen to less then stellar recordings at higher SPLs.
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In 2011 Al Klappenberger (ALK engineering) tested some drivers to be used with the Eliptrac 400 horn, including the FaitalPRO HF200.
I suspect his findings have contributed to the popularity of Faital drivers in the US.
"The mic was setup 2 feet from the mouth, level up to 105 dB SPL with a 400 Hz tone. The analyzer computed the harmonic distortion at -38dB. That's only 1.26% harmonic distortion!
Next I reduced the level need to make 105 dB at 2 feet by 10 dB and lowered the tone to 200 Hz. That is roughly what the level would be through a 12 dB / octave filter with the woofer generating the tone at 105 dB. The level out of the driver dropped to 63 dB SPL with the second harmonic down about 15 dB lower. That's 17.8 % distortion but the level is so low it would not be noticed!"
Quite impressive I would think.
I suspect his findings have contributed to the popularity of Faital drivers in the US.
"The mic was setup 2 feet from the mouth, level up to 105 dB SPL with a 400 Hz tone. The analyzer computed the harmonic distortion at -38dB. That's only 1.26% harmonic distortion!
Next I reduced the level need to make 105 dB at 2 feet by 10 dB and lowered the tone to 200 Hz. That is roughly what the level would be through a 12 dB / octave filter with the woofer generating the tone at 105 dB. The level out of the driver dropped to 63 dB SPL with the second harmonic down about 15 dB lower. That's 17.8 % distortion but the level is so low it would not be noticed!"
Quite impressive I would think.
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Thank you so much, Mitchba and Plasnu. I still believe I will be satisfied with my choices so far. I am just so curious about beryllium...the lack of a signature, per say, is an attractive trait for any driver driver. I can afford $700/pc .... I just don't see the value, especially when aquaplas has advantages like dampening and match-ability to paper woofer.
Speaking of tweeters, the krk's I have, are using this kevlar dome tweeter and I reeeaaallly like it! It sounds in between a ribbon and a silk dome.
What is this.....3 months now? The TD15m is honestly my choice woofer, I hope he is able to get everything proper.
Here's a question....In light of being able to get the woofers in 16ohm....I was big on running the amps in 16ohms...with the idea of being to lower distortion, but I recall someone suggesting running the woofers in parallel, to 8 ohms, which would increase the drivers sensitivity? Is that true? What do you guys think you would do?
Speaking of tweeters, the krk's I have, are using this kevlar dome tweeter and I reeeaaallly like it! It sounds in between a ribbon and a silk dome.
What is this.....3 months now? The TD15m is honestly my choice woofer, I hope he is able to get everything proper.
Here's a question....In light of being able to get the woofers in 16ohm....I was big on running the amps in 16ohms...with the idea of being to lower distortion, but I recall someone suggesting running the woofers in parallel, to 8 ohms, which would increase the drivers sensitivity? Is that true? What do you guys think you would do?
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Short answer.. if you have a pre-made Voltage source amp, have it run out of Voltage before it runs out of current. You'll either need experienced ears or test equipment to work this out.. Otherwise, an amp can be made to suit any load.
I forget and don't have Excel loaded, but you can do it here: Efficiency and sensitivity conversion - loudspeaker percent and dB per watt and meter loudspeaker efficiency versus sensitivity vs speaker sensitivity 1 watt = 2,83 volt box chart - sengpielaudio Sengpiel Berlin
16 ohms since the less current the VC draws, the lower its potential thermal power distortion assuming you're not driving them WFO all the time in which case you should design the cab alignment for it.
GM
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Camplo, my impression is that you will be using two TD15m's per speaker...is that correct?
If so, I would not get special ones made at 16ohms. Yes, you could parallel them for an 8ohm load, but if you ever wanted to use them singly in a different speaker design, a 16ohm 500w woofer would require an unusual amp to make that kind of power at 16ohms.
Woofers are mainly 8 or 4 ohms because most amps capable of driving higher wattage loads are optimized for 8 to 4 ohm loads. (proaudio amps lean towards 4ohms)
As far as reducing distortion, or thermal voice coil heating, is doesn't matter whether the woofer is 16, 8, or 4 ohms. Power at any given SPL, which makes the voice coil heat, ends up being the same.
I'd probably get two 8 ohms to use parallel. It's pretty easy to find a good amp that makes 1000w into 4ohms, or 500w into 8ohms (if you wanted to run singly)
Agree with Mark100. The JBL 4739 cabs I use with dual 15" are 8 ohm drivers wired for 4 ohms. I use a Crown XLS 1502 which is rated 525w a side at 4 ohms. Given the high sensitivity of the system, and listening at concert level for a short time, I can barely get the -20 dB light to blink on the amp with heavy kick drum and bass. One could go crazy and bridge mono two of these guys for 1550 watts a side into 4 ohms, but even a single amp is overkill for home. Certainly don't run out of headroom.
camplo, not sure if you were going to divide up the frequency range a bit between the two 15" woofers or you were looking at two different 15" TD drivers, one for mids (TD15M), one for sub duty (TD15H), can't remember, and its a long thread
camplo, not sure if you were going to divide up the frequency range a bit between the two 15" woofers or you were looking at two different 15" TD drivers, one for mids (TD15M), one for sub duty (TD15H), can't remember, and its a long thread
It would be best to make the system modular....I am hard headed lol! So if I will follow that completely sound and logical advice, is yet to be seen.
I think experimentation would be the best route, but I did settle on a total of 4 td15m's. I couldn't foresee any benefit of using a 15H for the sub (if that were the final set up) other than slightly tighter group delay. Better group delay 2-4ms at best for the 15H but then I couldn't experiment with the other configurations. I like the idea of the high output low xmax with the 15m.
I have my own personal theories, you could say, and I feel that coupling the woofers will create a larger wavefront, no different than using a large woofer or horn. I believe the initial wave-front size to be the main cause of the trait known to horn-loaded drivers, that is, the unmeasured quality known as dynamic contrast, which would be the opposite of dynamic compression. "The air space inside the horn couples with the diaphragm of the driver and allows the small element to move a larger volume of air than normal. "....My theory is that the wave-front becomes as big as the horns diameter (freq dependent) before exiting into the room and being subjected to its "atmosphere". The bigger the wavefront, the longer it can hold its integrity before it reaches its destination. Makes sense to me. So by placing the woofers right next to each other, the coupling affect, in that instance, should also increase the wavefront size and bring about those same benefits. Those are my theories, at least.
I have currently 3 crown CTS 2000 and a 1200. All of them do 16ohms. The 2000's are rated 625 continuous at 16ohm. I only need 34 watts for 116db at 1 meter according to winISD (dual 15ms).
I'll be listening at lower volumes for sure. I didn't know it would end up this way but the DSP in the input modules of these amps are definitely needed. It has all the eq I should need for voicing/room correction. When I use FIR filtering, it will in the ITB.
Right now I'm thinking, one amp per stereo set of drivers. That would allow for more articulation of the eq for room eq. If I am going to eq one of 15's, on one of the stereo channels, differently than the other in the set....I think I have to make sure they are in separate chambers. If I reffer back to the idea of coupling, it would probably be best to eq the set of 15's identically but I am not sure. I would think that it would change the polar/phase, but whether or not it would be detrimental....I dunno.
I think experimentation would be the best route, but I did settle on a total of 4 td15m's. I couldn't foresee any benefit of using a 15H for the sub (if that were the final set up) other than slightly tighter group delay. Better group delay 2-4ms at best for the 15H but then I couldn't experiment with the other configurations. I like the idea of the high output low xmax with the 15m.
I have my own personal theories, you could say, and I feel that coupling the woofers will create a larger wavefront, no different than using a large woofer or horn. I believe the initial wave-front size to be the main cause of the trait known to horn-loaded drivers, that is, the unmeasured quality known as dynamic contrast, which would be the opposite of dynamic compression. "The air space inside the horn couples with the diaphragm of the driver and allows the small element to move a larger volume of air than normal. "....My theory is that the wave-front becomes as big as the horns diameter (freq dependent) before exiting into the room and being subjected to its "atmosphere". The bigger the wavefront, the longer it can hold its integrity before it reaches its destination. Makes sense to me. So by placing the woofers right next to each other, the coupling affect, in that instance, should also increase the wavefront size and bring about those same benefits. Those are my theories, at least.
I have currently 3 crown CTS 2000 and a 1200. All of them do 16ohms. The 2000's are rated 625 continuous at 16ohm. I only need 34 watts for 116db at 1 meter according to winISD (dual 15ms).
I'll be listening at lower volumes for sure. I didn't know it would end up this way but the DSP in the input modules of these amps are definitely needed. It has all the eq I should need for voicing/room correction. When I use FIR filtering, it will in the ITB.
Right now I'm thinking, one amp per stereo set of drivers. That would allow for more articulation of the eq for room eq. If I am going to eq one of 15's, on one of the stereo channels, differently than the other in the set....I think I have to make sure they are in separate chambers. If I reffer back to the idea of coupling, it would probably be best to eq the set of 15's identically but I am not sure. I would think that it would change the polar/phase, but whether or not it would be detrimental....I dunno.
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Oh good, and yeah, amps made to do both low z and constant 70/100V duty are almost always optimized for the upper end of the 4-16 ohm low z spectrum.
But I'd still get the 8 ohmers
Interesting thoughts...all valid and going into the ol thinker....I had my own ideas, starting out, that the higher the ohms, the tighter the signal due to the electro-mechanical relationship. Higher electrical resistance, results in higher electrical dampening, which should result in a quicker stop of electrical energy after source signal is cut. if inductance is a thing...then this is a thing too...I present, evidence A
Now these comparisons have much grosser differences in resistance but, I can attest that I've always felt that subwoofers using 8ohms vs 4ohms, always seemed to have much more "authority" or should I say, tighter bass. Slightly limited experience...but still.
Now these comparisons have much grosser differences in resistance but, I can attest that I've always felt that subwoofers using 8ohms vs 4ohms, always seemed to have much more "authority" or should I say, tighter bass. Slightly limited experience...but still.
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The misconception here is that the damping of a loudspeaker goes up as the resistance goes up. This is false.
By far the greatest damping in a loudspeaker comes from the EM damping of the voice coil. Because this is a back EMF relation, the damping goes down as the resistance of the voice coil goes up. The damping (and efficiency) go as BL^2 / Re. Now if I lower Re with a given BL the damping will go up. But if I simply change the wire in the voice coil then as the resistance goes down, the L will go down as well and generally the two changes cancel out. This means that the damping, which is reflected in the Qe, will stay about the same IF the magnetic circuit stays the same.
By far the greatest damping in a loudspeaker comes from the EM damping of the voice coil. Because this is a back EMF relation, the damping goes down as the resistance of the voice coil goes up. The damping (and efficiency) go as BL^2 / Re. Now if I lower Re with a given BL the damping will go up. But if I simply change the wire in the voice coil then as the resistance goes down, the L will go down as well and generally the two changes cancel out. This means that the damping, which is reflected in the Qe, will stay about the same IF the magnetic circuit stays the same.
Gedlee....thank you for your clarification on the topic. This thread is very rich and you only add to it, to that I appreciate.
Can you help us iron out this deal about the two 15's vs the Horn and the resulting polar? I use Xdir to the best of my ability but it will only let you see a snippet of the whole picture.
The theme of running a 2.5 way has been brought up so many times but I am not confident that a 2 way won't work. I just can't picture the polar at xover (630hz)....I'm pretty sure the 2.5 or the MTM is the solution, I just want to understand why I wouldn't be able to like a 2 way.
We have the jbl 4722 crossed at 630hz, the PBN Audio M2!5 Loudspeakers crossed at 900hz....two ways with dual 15's...The Auspergers 215h have dual 15's horizontally, crossed to a horn at 600hz (they might actually overlap between 600hz and 2khz)...Of course people break the rules all the time....I am doing my best to be obedient. The only rule I intend to break is the desire to listening at 1m. A single 15" crosses over perfectly to a 350hz JMLC/Tractrix, as the effective OD is about 15" on both...so the polar is almost identical, down ~1.8-2db at 630hz. So that part is solved. If all 3 drivers are playing 630hz, -6db from the horn, -6db from the summed woofers...this puts the middle of the polar at the middle of all 3 drivers....correct? Using 48db LR xover the phase sums correctly. I'm racking my brains over this.
Can you help us iron out this deal about the two 15's vs the Horn and the resulting polar? I use Xdir to the best of my ability but it will only let you see a snippet of the whole picture.
The theme of running a 2.5 way has been brought up so many times but I am not confident that a 2 way won't work. I just can't picture the polar at xover (630hz)....I'm pretty sure the 2.5 or the MTM is the solution, I just want to understand why I wouldn't be able to like a 2 way.
We have the jbl 4722 crossed at 630hz, the PBN Audio M2!5 Loudspeakers crossed at 900hz....two ways with dual 15's...The Auspergers 215h have dual 15's horizontally, crossed to a horn at 600hz (they might actually overlap between 600hz and 2khz)...Of course people break the rules all the time....I am doing my best to be obedient. The only rule I intend to break is the desire to listening at 1m. A single 15" crosses over perfectly to a 350hz JMLC/Tractrix, as the effective OD is about 15" on both...so the polar is almost identical, down ~1.8-2db at 630hz. So that part is solved. If all 3 drivers are playing 630hz, -6db from the horn, -6db from the summed woofers...this puts the middle of the polar at the middle of all 3 drivers....correct? Using 48db LR xover the phase sums correctly. I'm racking my brains over this.
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I have never done what you are suggesting, so I don't have any experience.
But ... two woofers separated by a horn will have a strong vertical lobe if vertical, i.e. it will be very narrow vertically but wide horizontally. The acoustic center will be at the horn mouth so, in theory there will be no additional lobing at the crossover.
But ... things never go as expected, so you would have to measure the systems and design from there. It is conceivable that the horn and woofers directivity match - both horizontal and vertical - but I doubt that your horn is large enough to be controlled down as low as you are going. Hence, what it is doing is a big guess, but if it does match the woofers, that would be a coincidence.
I would expect the verticals to go very narrow, then very wide at the crossover, then narrower again. A big power peak as opposed to the big power dip when only one woofer is used.
But ... two woofers separated by a horn will have a strong vertical lobe if vertical, i.e. it will be very narrow vertically but wide horizontally. The acoustic center will be at the horn mouth so, in theory there will be no additional lobing at the crossover.
But ... things never go as expected, so you would have to measure the systems and design from there. It is conceivable that the horn and woofers directivity match - both horizontal and vertical - but I doubt that your horn is large enough to be controlled down as low as you are going. Hence, what it is doing is a big guess, but if it does match the woofers, that would be a coincidence.
I would expect the verticals to go very narrow, then very wide at the crossover, then narrower again. A big power peak as opposed to the big power dip when only one woofer is used.