lowerFE

Sorry for the late response. I thought I would get an email notification if anyone replied to me, but the setting changed for some reason. I tried on v1.41. v1.42 had a lot of problem with master/slave syncing (no sound on the slave speaker occasionally). v1.44 broke the EQ. Originally I said the soft limiter didn't work because I set it at 400W and the amp still power cycled at loud ULF passages. Upon further testing (using 5W limit instead) I see the limiter does work. Nice testing on the behavior of the limiter BTW!

That's some very interesting results. Did you find out whether maxing out one channel is enough to break in all channels? I'm the person that SME mentioned on Hypex amp experiences. It does some things very well, but some things are shockingly rough around the edges that I'm amazed they released a product with flaws like this. For example if the total gain on all filters exceed +24dB, the DSP crashes and sends full scale noise to the amp channels. Luckily, it spared the tweeter channel, and luckily the DSP recognizes the crash and doesn't go crazy after a restart. But this is still really bad. It is also possible to crash the DSP with a strong enough input signal. I suspect it is because I tripped the +24dB gain limitation because I had +20dB of boost due to Linkwitz transform, and I raised the master volume to +6. So when a -2dB or louder ULF signal hits the DSP, it gets boosted to +4, and since I had 20dB of ULF gain, I trip the +24dB gain and the DSP crashes and sends loud noise to the channels. This kind of bug should never happen on a commercial product. I can also get my FA503 to power cycle when exceeding its power limits. I'm disappointed the soft limiter doesn't work. My previous ICEpower amp never power cycled no matter how hard it was driven. The soft limiter actually reduced amp power output with a stronger input signal. I'm sure that saved my speakers from blowing up during some extended loud parties. @klipsch On the FA503's, Hypex actually did a pretty smart thing. It actually seems to turn the amp off when there is no signal to the DSP, and therefore the speakers are dead silent with no hiss. But there is actually a hiss, and if you feed it a silent/very quiet signal, the hiss is apparent. While the Hypex are technically excellent amps, it really sucks on the usability aspect. I haven't even talked about the excessive heat combined with a low maximum temperature, or how the DSP/amp takes 5 seconds to wake from sleep, or there's a very loud click every time it wakes/sleeps that I can hear from another room. For my next speakers I will use Pascal L-Pro modules instead. I hope they have much better usability behavior than the Hypex. I wish I could get my hands on OEM DSP plate amps with Pascal amp modules. If not I'll build my own plate amp.

Yes I did compensate for the mirror image effect with the exact same technique you mentioned. In the end I settled with ground plane measurements for bass + midrange in order to get the resolution needed in the lower frequencies, and then quasi anechoic gated measurements for HF. The quasi anechoic measurements get really tedious as one would have to compensate for the fact that if you rotate the speaker on a turntable, the axis of rotation is different from the baffle. Because of that the angles and distances are different and it's a lot of work to compensate. Without the correction the speaker appears to have a lot more directivity than it actually does. Another trick, wrapping the mic in Roxul or some damping material really smooths out the >10KHz measurements as tiny reflections coming from the mic stand and mic clip causes bumps in the >10KHz response. However, doing that causes the mic to appear to have a much larger body than it really does, and it causes diffraction effects <10KHz. So two measurements, one with no roxul and with roxul, and a splice is needed in order to get accurate measurements across the board.

Oh yeah I want that Klippel near field scanner so bad! Especially for this speaker because it's asymmetrical in both X, Y axis and Z to an extent. That's some interesting note on the distortion from panel vibration. Do you have a link to the AVS thread with the software simulation?

I was reading some old posts and saw this and just chuckled. It wasn't done 9 months later. It wasn't done 3+ years later either! I still have another 1-2 years worth of stuff I could do if I wanted 😲 Also, it was crazy how little I knew back in 2016/2017! A lot of the suggestions made much more sense now because I have a much better understanding. Thanks for the immense help from everyone and for putting up with me (who was way over my head) back in the day!

Wow it's been a very, very long time since I've updated my thread. Life got really busy in the past few years and I barely could squeeze time to work on the speakers, so writing about them and sharing it got lost in the shuffle. I want to give a conclusion to this speaker saga and give way to a brand new small speaker design that is significantly better than the Reference Mini in every single way. I continued working on this speaker over the years, and really refined it as much as I could. In the process I realized this speaker's design is actually extremely flawed in multiple ways. However, this meant this speaker was also the best learner speaker I could have ever hoped for. It allowed me to learn from experience the importance of every aspect of acoustic performance considerations with speaker design. I'll specifically talk about cabinet resonance, as this is by far the weakest point of this design, and the issue also eluded me for years because it doesn't really show up on any type of microphone measurements. Basically, I didn't care about cabinet resonance in this design, but that turns out to be a huge mistake as it significantly compromised the sound quality of the speaker. An enclosure with 6mm walls with no bracing is a bad idea boys and girls! The cabinet resonance was low Q and high in magnitude around the low midrange region, and radiated in a dipole manner, which made the speaker much more sensitive to room acoustics than typical speakers. This did a lot to muddy up the midrange. I wondered a while why my speakers don't sound right in the midrange, and I spent a lot of time optimizing the crossover and the accuracy and resolution of my measurements to try to find the answer, but in the end it's I was barking up the wrong tree in my method of attack. Other weaknesses are too much dispersion, baffle diffraction issues, poor rear wave absorption, poor rigidity walls causing losses in bass output, and many more. After 4+ years of learning and continual design iterations and refinement, I am finally ready to make the successor of the Reference Mini. I am calling it The Impossible Speaker, because it will do things that should not be possible from a small speaker, such as controlled directivity down to 400Hz with 20Hz bass extension and bass output that'll beat an SVS 12" sealed sub, all in a speaker ~1" bigger than the Reference Mini. Every single performance criteria is not just improved, but significantly improved, from diffraction to headroom across the board, THD, IMD, to electronics, and of course, WAY WAY better cabinet resonance suppression. One thing that isn't improved is cost, which is kinda impressive given the Reference Mini cost over $5000. This will be one hideously expensive speaker! However, I think this speaker will actually live up to be the ultimate small speaker.

I'm sorry guys, I'm doing a terrible job of updating my thread. This year has just been crazy for me. I'll eventually update! I wanna at least put up a measurement of my speaker, even if it is an older measurement, and the current speaker performs better. There is no smoothing at all in this measurement. I want to repeat this again, because accurate measurements should never be smoothed. The measurements are in 20 degree intervals, 0, 20, 40, 60, 80, 100 degrees. I have measurements in 10 degree intervals, but not for outdoor ground plane. I have limited battery power when measuring outdoors, so I did the outdoor measurements in 20 degree intervals. <900Hz it is ground plane measurements. Above 900Hz it is quasi anechoic with 10.5ms of gating. The speaker is even better now, since the minor crossover dip is now moved to ~3100Hz (the most sensitive part of our hearing, and also the region where the ear will be least noticeable to dips), and steered so the deepest dip happens at around 40 degrees instead of 20. The midrange is brought up to be flat with the treble as well. The graph has less wiggles due to further removal of sources of measurement reflection. But I don't have a complete set of measurement yet. Measurements is really hard, much, much harder and more complex than people think. I've literally done thousands of measurements on my speaker and I still don't have measurements that I would consider to be accurate. I do think I have the methodology down now, but just don't have the time. To give an idea of what's required: For each axial measurement, it takes 3 splices - Ground plane measurement for <1000Hz - Quasi anechoic measurement for 1000-10000Hz in a large space like gym or auditorium to achieve ~10ms gating. The typical 4-5ms reflection free time achieved in a typical room just doesn't have enough resolution - Flush mounted microphone for >10000Hz measurements to avoid reflections from the mic clip and mic stand. Then the ground plane measurement has to be compensated because it shows the result of a double height baffle since the ground is a reflector. A compensation factor of the difference between the double height baffle and the normal height baffle needs to be applied. Then for polar measurements, things get real tricky. The standard way of rotating a loudspeaker on a turntable does not give the true angle and distance because the centre of rotation is at the centre of the speaker instead of at the centre of the baffle. Therefore, there needs to be angle and distance compensation applied. The angle compensation needs to be done physically by moving the mic. Distance compensation can be done after measurement. So as you can see, for polar measurements, which I do in 10 degree intervals, requires 36 measurements for horizontal, 36 measurements for vertical, so 72 measurements. Multiply 72 by 3 for 3 different drivers, and you get 216 measurements. Then another 72 measurements for the final response for a total of 288 measurements. But wait, I have 3 measurement conditions, ground plane, quasi anechoic, and flush mounted mic! So that's 864 measurements! Therefore, I have to do 864 measurements to get a complete polar response for this speaker, AND I have to do the baffle, angle, distance, and splicing compensations for all of those measurements! Yes, there are some shortcuts that'll cut the work by half, but that's still a crazy amount of work. One day I'll actually do all that, but not now. And yes, every one of those complications is important to do in order to get a truly accurate measurement, and it makes a HUGE difference.

OK. Maybe I should finally start updating this thread after so long. Sorry guys, I was just really busy, and still am. Writing takes a long time, and I've always just put that on the back seat since more time writing = less time improving speakers. Here's a sneak peak of what's coming up. Since this is data-bass, here's a preliminary 1m ground plane output compression measurement of a single speaker without a limiter on. Once a proper limiter is done, I will be extending the sweep all the way to 115dB.

I respect Harman's research as well. Very thorough and well executed. However, there is a weakness. The research, and all of its data is based on existing speakers back in the day. Essentially, it is just simply finding out the most preferred speaker that has already been made. It makes no attempt in finding the theoretical optimal sound signature. Therefore, if there is a sound signature that is preferred over anything else existing on the market, but does not currently exist in a speaker due to technological limitations, then it would not be found. A subjectively flat response is exactly curves (since it changes) that a passive speaker cannot do. I argue that having equal loudness compensation is half of the equation in the ideal most preferred curve. The other half is full range constant directivity down to the schroeder frequency. Regarding whether the curve should be statically applied based on a volume level versus the instantaneous RMS level of the signal, I think both have merits. Currently I am on the former, but I'm thinking of moving to the latter. The reason is because I think a static equal loudness compensation based on a volume level is most optimal when the reference volume is known, such as in surround sound formats. This is the closest to real life since the frequency response of individual sound sources do not change depending on the volume. However, when we don't know the reference volume, I'm inclined to use a dynamically applied compensation. This is because for most music, we simply don't know what the reference volume is. The average level of songs can vary quite widely depending on content. Also, for most music, especially for any music that contains electronic instruments, there is no "reference volume" anyways. We have no idea what "real" really sounds like. Therefore, there is little purpose in trying to achieve "realism", and the goal should be "good sounding". When the reference volume can differ rather dramatically between song to song and genre to genre, a dynamically applied compensation will have a better chance of sounding correct since it is based on the actual SPL heard at the listening position. The obvious exceptions are classical music, or any music with large dynamic swings since they should be left as it is instead of being modified, but I hardly listen to music with real instruments.

I am not saying old people don't like extended treble response. I'm saying people with hearing damage don't like extended treble, and that is generally old people. That's like saying good speakers sound good, and they're generally expensive. Doesn't mean expensive speakers are good, just happens that expensive speakers generally sound good. There are lots of older people that love the sound of my speakers. Had a retired man who cranked metal music on my speakers, and cranked it LOUD, and he told me it had the best cymbal crashes he's ever heard! There is a WORLD of difference between accurate reproduction on a headphone vs on a loudspeaker. There is zero crosstalk on headphones, which dramatically changes how imaging is perceived. There is no concept of direct vs reflected sound on headphones since it is all direct sound. There is no concept of directivity on headphones either. The amount of bass is dependent on the seal and fit of the headphone. Correlations between headphones do not necessarily apply to speakers. I was lazy and posted the same thing that I posted on other forums to this forum as well. The above is "dumbed down" so it is easier to digest for the average DIY'er. For this forum I should write something a lot more technical. But basically yes, it is just Audyssey Dynamic EQ, but a better version of it. Audyssey nailed the lower range, but not so much on the upper range. I still haven't gotten it as right as I could make it, but so far it has been a lot better with this than without it. You're right that the amount of boost that needs to be applied will be dependent on the source. My intention is not to get it right for everything because that's not possible. If you optimize for one song, it might introduce problems for other songs. Therefore, the goal is to apply a general broad stroke correction so it provides a positive benefit for ALL sources.

I'm long overdue for an update. I've actually lately been too busy simply enjoying these speakers or giving people demos of these! But there were actually a number of big improvements that made night and day differences to the sound quality of these. I will talk about them over a number of posts. This post will be about my discoveries in sound signature preferences.The Universal Sound Signature PreferenceI'll start with a story. I brought this to an audio enthusiasts get together a few weeks ago as a bunch of people want to hear this speaker I've built. I set the speakers up in my friend's room, but I was having strange setup problems that I've never encountered before that took some time to fix. Since there was about a dozen people waiting and eager to hear this, for the sake of time I only did a rough setup that resulted in poor placements (speakers placed right against the side wall and above ear level) and did only a rough room correction to compensate. However, once it was set up, nobody wanted to leave. This is a room where at least half the people owned 5 figure sound systems at home, many had traditional speakers, some had tubes, some had huge horn speakers, and they all sat there, continuously adding songs to the queue, and listened to the speakers for over 4 hours besides a little break here and there to talk and discuss. The fact that they listened for over 4 hours tells me that everyone truly loved the speaker. Otherwise they would have simply left after a few songs and went to talk to other people outside.Unlike the traditional thought that people have different preferences in how a speaker sounds, where some people like their speakers sounding bright, dark, warm, etc. I believe there is a universal preference (with one exception), and now I have strong anecdotal evidence that supports this. This is going to be difficult to believe, but once you hear this, I think most of you will agree. I believe the universally preferred sound signature is one that is subjectively flat. I've tried this with over 50 people at this point, and it is clear that this is an appealing sound signature regardless what their original preference is. I've had people actually tell me this is very different from what he's used to hearing, and it changed his view on what is "good sounding".What is a "subjectively flat" sound?Now this is tricky. This is not flat, like a speaker with a flat frequency response, but subjectively flat. Our ears hear differently at different volumes. At normal volumes, our ears are less sensitive to bass, and to treble, but to a lesser extent. As the volume goes up, our ear becomes increasingly sensitive to bass and treble. This means that a speaker that measures flat will sound thin at normal volumes since the subjective frequency response that our ear hears will be a "semi-circle" shape where the bass and treble is rolled off due to the lower sensitivity of bass and treble. This is why many speakers sound better at louder volumes. This is because as the volume goes up, our ear's sensitivity to bass and treble gradually increases. This means that the speaker is sounding more and more subjectively flat as the volume goes up. We like a flat sound, which is why we like the speaker played louder because it is closer to flat. The same reasoning can be applied to why bright speakers sound nice at normal volumes, but becomes annoying at high volumes. At normal volumes, the bright sound compensates for our lack of sensitivity to treble, so the top end sounds subjectively flatter than a neutral speaker. But when you turn the volume up, the ear's sensitivity to treble increases, and now the ear hears a sound with too much treble, and we don't like it because we like a flat sound.What does this mean? What we perceive as sounding "flat" varies dramatically depending on the volume. In order to achieve the universal preference of subjectively flat, we need a speaker that changes its frequency response depending on the volume it is played at. This is not possible to achieve this with any passive speaker.So for a speaker to sound subjectively flat, there must be a bass boost and treble boost. It is not a straight boost either, but a continuous slow rising response starting from low midrange (around 400Hz) and into the very deepest of bass. A similar, but a much smaller rising response is needed for treble starting around 5000Hz. Isn't that just a V shaped frequency response? You must be shaking your head in disgust! V shaped??? Blasphemy!!! However, the response I describe here is almost impossible to do on a passive speaker since the boost required on the bass would require the speaker to lose over 10dB of sensitivity, and the inductor needed to start cutting at 30Hz is just impractical. This is why most "V" shaped speakers don't sound great. They are not getting the right target curve needed to sound correct. Even if they are through the use of an external equalizer, the amount of bass boost and treble boost needs to be different depending on the volume so it always results in a flat subjective response to our ears. The equalizer provides a static change in frequency response and it doesn't changing with volume, so it'll sound bad at higher volumes and create fatigue (too much treble) and boominess (too much bass). With my speakers, after a calibration it knows exactly what the SPL is at the listening position, so it can automatically adjust the bass and treble depending on the listening volume. This is the key to get the speaker to sound subjectively flat to our ears, and if done right, it sounds downright amazing, and just sounds right. The Exception(*) What is the exception? I've found that this is not true for people with substantial hearing loss, i.e. a lot of old people. This is the group that heavily favours a very rolled off treble sound. For some reason I don't yet know, these people seem to think treble is the devil. I would think with hearing loss, you would want MORE treble to compensate for their reduced high frequency hearing. However, it seems like people with hearing loss genuinely hate treble because for some reason it greatly irritates them. I brought these to the Burning Amp, where most of the attendees are well over 50. I ran a long 20 second frequency response sweep, which meant there were 10 seconds or so where the sweep is in the treble region. I noticed several people covering their ears during the sweep, and some looked like they're in pain. I got much less positive reception there, which is understandable because most of the speakers that were presented had, in my opinion, essentially no treble. And of course, these "treble-less" speakers got huge positive receptions, which is not surprising at all if hearing high frequency causes these people to contort their facial expressions.

So after reading this thread over the past year and amazed and the technical depth and extreme attention to detail paid to the tuning of this system and going "man I really want to hear this!", I flew and went to check out this system. And boy what an amazing system to listen to! My mind was blown as I was amazed by one thing after the other. All the work put into getting the tonal balance of this speaker correct really paid off big time. The whole system just sounds really "correct", and the more I listen to it the more I'm amazed by it. I brought my Reference Mini's with me as a comparison, and there was a very obvious difference in sound quality. I thought my speakers sounded really great, but it sound noticeably "off" when compared to this system. The speakers had a fantastic amount of detail, and the transients are awesome! It felt like I'm listening to a pair of really good headphones (and few people realize how hard and impressive it is to achieve this), but I also get the enveloping sound that makes speaker listening so pleasurable. It's the best of both worlds. What's even more impressive is the bass. I don't think I've heard bass so tight and full sounding in a room, which is clearly due to the complex integration efforts of multiple subs and individual EQ's to get such flat bass over a large number of seats. The clarity and tightness is seriously impressive. Again, just like a headphone, and that is actually something I've never heard before from a subwoofer. It is straight up the best sounding bass I've heard in a room. Now when you also get the whole body physical sensation from bass, addictive is an understatement. One thing that is unforgettable and blew my mind is how great the speakers sound in the kitchen! I don't think SME has ever mentioned this, but it was indeed one of his goals. It was remarkable hearing a correct tonal balance with almost no treble roll off in a different room! I still can't believe this is achievable. It must be the combination of controlled directivity speakers and properly placed diffusers pulled this amazing magic trick of a feat. I've heard a lot of amazing home theaters, but this is the first time I heard imaging from surrounds. It was trippy to be able to pinpoint the location of the sound going across the rear stage. I really wish we watched an action movie and be able to so accurately track the position of the sound effects. This is even more impressive as I seem to clearly have less ability to hear imaging compared to other people. Speaking about imaging, the speakers reproduced phase manipulated music tracks far more accurately than anything I've heard so far. It must be the room treatments that are preserving the phase accuracy of the speakers. It was like "oh this is where it is supposed to sound!" I was also exposed to the dark secrets of the time domain in room correction. That was a revelation to me to be exposed to so much more information and tools to analyze room acoustics. Now it makes sense why and how the room is mucking up the sound. It's all in the time domain! Now I am able to correlate measurements and subjective judgment of how good (or bad) the room sounds. I have so much to dig and play around with now. Measurements really can tell you about how good something sounds if you look at the right things and how to interpret it properly. Thank you SME and his wife for being such amazingly gracious hosts. That was one hell of a weekend! Oh, and did I make it clear enough that your system sounds good?

Little update. I just moved last week for a new job, so I didn't get a chance to really work on the speakers much to deal with moving. But for something fun, I improved the limiter design a bit to get a bit more maximum clean bass output from the speaker before the limiter clamps the output. I've wrote a lot about my speakers so far, but this time here's a video of the Reference Mini's doing ~107dB of bass and 109dB peaks. The listening position is about 8 feet from the speakers. For reference the TV is 40". I promised there will be bass!

Oh I've been enjoying this, but not as much as I would like to because I've had way too many things to do in the past couple of months. At certain times it feels like working on the speaker is a chore that needs to be done. Granted it was a lot of technicalities like measurements and stuff, but now the real fun begins with all the DSP, features, especially since soon I will have a lot more free time to play and enjoy. I'm going to get Dirac soon for this speaker and it should be fun as that should be a big step forward in sound quality in a room. There's going to be endless amounts of tweaking and optimization that I will be able to do with this. I think that's the best part, being able to incrementally and continuously improve the speaker and have features or combination of features that exist on no other commercial speakers. When I get a breather I got to catch up on what you have done!