Works for this guy. My LF slot is no less performing, actually its better performing. My LF drivers have no large restrictions unnecessarily decreasing volume while increasing velocity.
This guy can't even make it to 200hz let alone 400hz
I am only humorously jabbing at these products as we all know they need no introduction but... For my application I desired to cover 20hz-400hz while staying under 2mm. Stereo gets me here
The baffle design gets me here
All from a Single Acoustical Axis within a Single channel of woofers.
This guy can't even make it to 200hz let alone 400hz
I am only humorously jabbing at these products as we all know they need no introduction but... For my application I desired to cover 20hz-400hz while staying under 2mm. Stereo gets me here
The baffle design gets me here
All from a Single Acoustical Axis within a Single channel of woofers.
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You have taken a driver with near flat response from 100 to 1kHz, then by design (?), made it's response approximately +/- 10dB in that range, then plan to "fix" it with eq and damping.
You call +/- 10dB (two orders of magnitude) "little things"...
Reminds me of when the Beach Boys replaced key members before a tour, their live vocal harmonies sucked, so the "fix" was to drown them in reverb.
It didn't work, but reviews blamed the bad sound rather than the vocals...
When you are comparing crap response, not hard to get better 😉
If you ever complete the "redesigned Slot" cabinets and measure them you will see if your simulations do what you think they might.
You have won that argument with yourself, listening at one meter.
However "intimate", measurement without the horn you chose is virtually useless.
Considering you crippled the response of the woofers with slot loading, at a 1meter listening distance the horn probably (arguably..) does sound better.
Your old LF slot performed terribly regarding frequency response, your new slot performance has not been tested.Works for this guy. My LF slot is no less performing, actually its better performing. My LF drivers have no large restrictions unnecessarily decreasing volume while increasing velocity.
I've heard no velocity related complaints regarding the cone drivers in DSL's multiple entrant horn designs.
The SH 96 uses six four inch cone drivers for midrange, around 12 times the displacement of your AXI2050 diaphragm.
The active low/mid crossover SH96HO (high output) raw response allows an acoustic crossover as low as ~300Hz, although with around a -6dB dip in that range in the passive crossover 3way SH96:
That said, the SH-96 doesn't require as much EQ as your slot, and it's mid/high section won't suffer the IM distortion of a single HF driver required to cover 200-20,000Hz as in your proposed system.
Cheers,
Art
Thank you for the critique! Respectfully, My rebuttal;
There's no alot going on.
The SH96HO is a beast, I did not bring this thing into the conversation lol....I also have done a fair amount of research and know that my design is already pushing limits. I did not want velocities to reach over 15-20m/s. "The loudspeaker shall have an operating rage of +/- 3 dB 45 Hz – 13.5 kHz."... 4 15"s that are only anticipated to reach 45hz could be a tell of the consequences of restricting air flow. No reason why this thing shouldn't make it to 20hz.
This is the first iteration of the PPSL with no filtering and floor carpet damping. There is no flaw in using EQ to flatten this response. The rising
There's no alot going on.
Here is a similar sized closed box superimposed over the slot sim. OK there's a resonant peak.. There's one Filter. Wow.... In comparison to the SH96, too which I am only considering the LF driver performance... I would be very surprised to hear that there is no filtering to remove the Resonance that is created by every offset horn I have ever seen. Even if the peak was nulled by a low pass filter, it still has a response similar to mine and any other offset horn of similar fashion. In other words, Tom Danely "fixed it" with EQ, Just like I will and there is no Harm in doing so. My slot proposedly will make it can be crossed high but with one channel of woofers, instead of 2. "That said, the SH-96 doesn't require as much EQ as your slot" How much eq do I need? I judge EQ amounts by filter count, not by how much the boost or cut. How many filters are used in the SH96???? The distance from the LF source to the beginning of the line is pretty large... and I'm too familiar.... that means there is a Peak in the FR of the sh96[HO] and it must be Eq'd out.
The SH96HO is a beast, I did not bring this thing into the conversation lol....I also have done a fair amount of research and know that my design is already pushing limits. I did not want velocities to reach over 15-20m/s. "The loudspeaker shall have an operating rage of +/- 3 dB 45 Hz – 13.5 kHz."... 4 15"s that are only anticipated to reach 45hz could be a tell of the consequences of restricting air flow. No reason why this thing shouldn't make it to 20hz.
I don't agree. The closer the mic to the source, the truer the measurements. The horn doesn't allow one to use compression driver at high volume without moving the microphone very far from the driver. The horn also skews THD results below the resonance. With the horn removed you can crank the voltage and get measurements much closer to the driver. If there are excursion issues to be captured, you will capture them this way. The horn can give high THD readings that have nothing to do with over excursion so I guess it depends on what you trying to see.
Because it is rated at 133db continuous, 139db spl max. Having a avg. sens of ca 103db. Using 4x Faitfal FHxxx.
Meaning it must sustain those levels reliably and continiously, over many years in any 'normal' condition.
If it is used in 50 celsisus summer conditions, compared to your 25 c living room it needs that much extra thermal capacity. Also at any altitude from 0 -4000m.
The LF drivers excursion capabilities needs to keep up the 36db of headroom at 45hz, without over-excursion or thermal issues over a long time.
A commercial product like that needs a slight safety margin, else the road is short to warranty, replacement parts, lack of robustness and systems breaking down in use.
A different reality then our home systems.
The quoted range is 45-16khz -3db.
With the recommended 40hz, 24db/oct HP filter.
With no frequency indication, can's tell what pass band this is, but appears ~20dB deviation in the range you chose to post above the green line.
20 dB is a power range of 1/100, which is "a lot".
Surprise, the horn load bass reflex SH96(HO) raw response shows approximately +/-4dB over it's potential 50-500Hz pass band.
The SH96 uses a LP above it's pass band, EQ is optional.
Looks like ~20dB.
You decide the count, the amount of boost or cut decides the usable bandwidth.
No electrical filters the raw response.
You posted it in 14,202, the post I responded too.
It's a bass reflex enclosure with an Fb ~45Hz as can be seen by the phase change at the low corner, the four bass reflex ports, and steep decline in frequency response below Fb.
No designer or user should expect useful output below Fb from a bass reflex.
The closer the mic is to the source, the further it is from the far field, where the measurements don't change with distance.
That statement makes no sense.
Yes, one takes measurements to analyze different aspects of performance .
Or listens for them, as in the anechoic room photos in post 14,207.
Art
These sims are rough drafts of a Axi on a lesser efficient horn than what I have..... The Axi has linear excursion suposedly up to 1mm... when exactly does the IMD/THD problems kick in????
THe best thing I did for myself was to design for PSL goals using a single channel....
My horn has some flaws in the LF roll off than can be avoided by crossing at about 250hz.... WIth a better horn, one with a proper roll off... I see no excursion problems in simulation.
I think this is at 3volts... which is enough headroom for about 113db/1meter in stereo, with the 200hz XO. No signs of over excursion.
Can someone show me a simulation suggesting otherwise?
You can test and listen for IMD with multiple tones to find out for yourself.
Running a woofer from 20-200Hz (one decade) you will notice it's IMD sounds much worse than it's HD when the low frequency is run to Xmax (10% THD) and modulates the higher tones.
200-20,000 is two decades (!) of operation, and I'd expect most would hear IMD in the upper range as more objectionable than at lower frequencies, especially with a horn with a slowly expanding long throat.
Of course, you might not find the "gargling vocals" sound of IMD objectionable at all.
Dr Jack Oclee-Brown mentioned at about 55:38 in the video describing the Axi2050:
“We’ve got a 1mm gap between the front of the diaphragm and the phase plug at it’s widest point which comes down to almost nothing where it’s clamped”.
That means 1mm is Xmech/Xlim (not Xmax), and it's average displacement might be as little as half that when the diaphragm reaches the phase plug, if the suspension allows that much excursion.
He also mentions the displacement of the annular ring AXi2050 is about the equivalent to that of a 4” dome.
JBL engineering data specifies their large format compression drivers Xmax as 0.5mm, with a diaphragm to phase plug distance of 1mm.
You "think" the graph was at 3volts, (around ~1 watt) and it shows 10% distortion, so the diaphragm has likely reached Xmax.
I recall you posting other measurements of your horn/driver combination reaching 100% distortion, obviously exceeding Xmax by a large margin.
I can't, but speculative simulations suggesting something other that what you have already measured with your unusual horn/driver combination does not seem useful.
Art
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This is my point about taking measurements of Thd without the horn. Looking at the measurements with no horn its obvious that those measurements showing crazy thd numbers were not accurate. Those 100% thd readings were very low level measurements buried far below cutoff. Taking off the horn isn't going to lower thd, but it allows the microphone to get close enough to bring the signal well above the noise floor.
This is a listening position measurement [old design] with only a low pass. Corner loading brings up Bass evening things out quite well. The green line was a trace I did with the Rta
In the Axi video the presenter says the Axi has 1mm of linear motion in either direction at 50:55
I will go through the motions again when I finish these dang boxes... the way I test is to play the highest frequency I can hear and then sweep the with another frequency through cut off. I don't recall every detail of my test but don't you think thats a good test?
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Not knowing what your test is trying to measure, or what you are trying to hear, can't tell whether it is a good test.
What makes IMD objectionable is the inharmonic sum and difference frequencies are basically noise.
As an example, play a 250Hz (near or above Xmax) and an 1100Hz signal, and 850Hz, 1350, 1600, 1850, 2100Hz are all generated in addition to the second harmonics of 500 and 2200.
IMD is kind of like a distant weed blower revving up along to your music.
Almost any voice or instrument has second harmonics, so a little bit added by the speaker is hardly noticeable, but using too much of the HF driver's low frequency excursion capability just fills it's high frequency range with garbage.
I figured that sweeping the LF while simultaneously playing the highest frequency I could hear would be a stress test for IMD. I listened for Amplitude modulation of the highest note.
Too much, as in exceeding the drivers linear excursion.
As an example, if 15kHz was the highest frequency you could hear, the lowest IMD frequency of 250Hz and 15000Hz would be 14750, and all the upper IMD garbage would be above your hearing range.
I certainly wouldn't detect IMD under that test.
The amplitude level of an audio signal is measured in dB SPL. In the above example, the 15kHz "note" (about 3.5 octaves above the highest note on a piano..) sound level would vary 250 times in a second.
I don't think it would be possible for anyone to hear a volume change (tremolo effect) at a speed much faster than 25Hz (25 amplitude modulations per second) much less 250Hz or higher.
"Linear excursion" is exceedingly hard to define for a HF driver 😉.
The center portion of the AXI 2050HF driver's flexing annular diaphragm can make contact with the phase plug (1mm peak displacement at Xmech or Xlim, the mechanical limit of excursion) while moving "in a linear way", as Dr Jack Oclee-Brown says.
It's Xmax could be said to exceed Xmech.
The AES 2-1984 standard for Xmax is defined by the voice-coil peak displacement at which the "linearity" of the motor deviates by 10%.
That standard (when applied properly..) is still helpful when comparing low frequency drivers output potential, but useless for determining what a compression driver/horn's IMD will be.
Art
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