peniku8

Maybe they defined their 'THD' as the sum of only 5th harmonic and up Manufacturers do all kind of crazy stuff to show impressive numbers. Like Klipsch, defining maximum SPL with the conditions "2 subwoofers used in 1/8th space".

RTA→Stepped Sine→select Step level, like this And no, I'm not keen on doing more sustained testing. I'm tired of blowing stuff up. It's annoying and costly. If you really wanna test PA amps you could put em into an incubator at say 40°C/105°F to simulate a hot summer day and give it a beating over an hour. Pretty sure most amps will die like that.

New ADC arrived today, mind the new scale. Fireface in comparison (distortion seen comes mostly from its ADC): From 98db THD+N to 120db THD+N and dropping the noise floor by 20db, that's something I like to see! This is currently limited by the DAC, which will eventually be upgraded too, but I'm pretty happy with this so far. Certainly did not expect having to increase the graph range to -180db because half of the noise floor would drop off the chart even if it was set to -170! At least I can properly measure stuff now without having to worry about optimizing gain structure in my measurement chain (Fireface was distorting more starting from -10dBFS out and/or in). Pmillett measurements following.

I did mean but not actually wrote extension lol, sorry for the confusion. Fixed now For upper/mid bass a long horn will be better than a single bandpass, since it increases efficiency, and thus decreases relative distortion levels. A simple slot 'loaded' bandpass will do the same, but a bit less overall, emphasize upper bass less and maybe yield better results in mid bass if the resulting front 'chamber' volume is larger. Been some time since I designed my last cab in hornresp and played around with this stuff, but design approaches will be pretty good for music. Group delay might become an issue if the front slot is very long, I'm not sure. But that's probably talking extreme lengths you'd typically not reach, which would also kill upper bass.

I'd not say the devs are cabs that are blindly going after extension. I'd rather attribute that to simple vented designs like the Marty line for example. The devs are band pass designs, which increase sensitivity and should decrease distortion in the mid-upper bass region, depending on the slot length (there are like half a dozen dev designs that I am aware of). Additionally they bury the driver, which protects the membrane, which is something I like. Never personally built/heard or dug into the measurements of these, so I can't comment on the design itself, but it theory it can be pretty good. Lately I've been very intrigued and impressed by designs with shaped/heavily flared ports, but these are extremely hard to build sadly, if you want to make everything out of wood (and sturdy).

Sure, I can do that. It's still 2 tests less than my previous set up. My Sanway amp actually mutes when given high amplitude HF information (above 10k), and also muted when trying to run full power into 1R, so at least some protections are working there. Just unfortunate that they don't have thermal protection, which made mine blow up. I mean, it was fan modded and on a 1 minute full output test, which was a bit unfair, but still...

Yea, seeing how the results on the Hypex amp are barely any different at all, I guess we can safely classify and dumb down application types by a single frequency. 60hz for mid-bass, since that's where the kick drum will sit in most non electronic modern music, 10Hz for the HT ULF crowd and 1khz as general full range guideline, but I'm not sure if 16khz is of any value at all. Music is typically mixed to drop off by 3db per octave and then even more when approaching the last octave, so 16khz demands will already be only a fraction of even just 1khz, unless you're talking long-throw line array applications where you need lots of distance loss compensation, in which case you're most likely using specific system amps anyways (or you somehow need maximum power into a super tweeter!??). You can call the segments 'Full range performance', 'Bass performance' and 'Deep bass performance' I guess.

Amp is up and running again, were just the fuses. 45 year old amp takes accidental 2ohm clipping like a champ and only causes 1$ of damage. I love this thing! And it's actually good THD, even by today's standards (0.007% 4V into 8R). I fixed some other things and mondernized the amp while I was at it, fitting it with a C14 socket (replacing the fixed cable) and clamp style speaker connectors. There are LED-sized light bulbs (!) inside the panel that lights up the tuner's signal strength, of which one still works. I put it in the middle socket and it lights up both meters now, it's great.

I record the amp's output as WAV, so I'm logging the db values in the first place, which I then use to derive the powers from. Changing out the values with db values shouldn't be a problem at all, but like you said, if people wanna compare amps at certain frequencies (say you're looking for an amp for your tactile system, so you look at the 8Hz results), you might be better off comparing absolute powers over relative db loss, which you then have to backtrack to compare. For me it's easier to make out the db changes in my head (like when I'm seeing 1000W at 1khz and then I see 800W at 30Hz that's somewhere around 1db loss), than to reverse the process and I like dealing in absolutes, because we're comparing different amps in the big picture. I could maybe also display both, but I already had enough trouble with Excel to make this work as I wanted it to (it's a universal file and the graph needs to adapt to mono blocks, 4 channel amps etc...), and I think even more info would clutter the graphs a bit too much.

What bit will you be using for this? Something like here? https://www.aliexpress.com/item/32947219454.html

Which of the two styles would you guys prefer? Currently it shows values for 1khz for full range reference and 30Hz for deep bass reference, but I'm not even sure if that's needed. The data table clutters the graph a lot imo Evaluations will additionally have these: Which will react like this when they're presented with differing values for bust and peak:

I've build 20 speakers with this dado size now and I see no reason why I'd need them to be deeper. And tbh, I don't think it's worth the hassle to make them when you don't have a CNC. You'll waste all the time you save on assembly with making the joints, possibly more.

If you're talking about the dado joints, I always make them 3mm. That way I can cut them with max feed rates on my machine without worrying about inaccuracies too much. I never felt the need to make them bigger, they're mostly for easier positioning anyways, so 3mm is just fine for that. imo it doesn't matter stability wise, unless you expect to throw the cabs off a balcony often.

Well to be fair, I didn't double check and thought I was testing it into 2x8R, but instead the load bank was set to 4+2 Ohm...

And the loadbank causes another casualty.. this time it's a Yamaha CR-600. Fuses are done for, but I hope everything else is still good. Measurements of my Hypex FA123 coming soon. Also ordered dedicated measurement equipment, since I already had trouble measuring the true performance of the Hypex amps... Fireface not clean enough. Getting the Cosmos ADC to use with a Topping D10b. Probably also going to get the Cosmos APU once it releases, which includes a 1khz notch and a preamp capable to delivering phantom power with lots of gain.

The QSC sub is larger and probably has more vent area compared to the Skram (when you block Skram ports to reach the same ~25Hz(?) tuning), meaning the QSC will be louder in the sub bass. Skram is front loaded, which means it's more efficient (louder) in the mid/upper-bass region. Skram is basically a band pass, which means it also masks some distortion. That would be the 3 main differences I guess. Skram has a rising native voltage sensitivity, while the QSC is probably pretty flat, going by my gut feeling here.

The ds and sw are very similar in maximum output at their respective program powers. Bennett from B&C said you should only really use the sw if you need the higher power handling, otherwise it doesn't really matter which you pick so you should go for the cheaper one. Here is a hornresp of different drivers I've compared in the SKhorn

And I just moved and only have headphones at the moment 😖 I'm just gonna say that I believe that most, if not all difference in tonality between different drivers or these subs vs 'normal' subs in a home setting is due to a lack of EQ/calibration. I've been using the SKHorn in my HT for over a year and calibrated to the same response I could hardly hear any difference to the 12" Klipsch sub I had at lower volumes. The SKHorn integrated into my HT just like any other sub. Electrically. Not physically... These type of cabs often have a significant bump somewhere between 100 and 200Hz, which means your acoustic crossover will be higher than expected (unless they're on a dsp), which probably is what you're describing as 'Brute-ish' or 'dark'. Thanks to rona I have 4 unused 21ds115's in my basement right now. It makes me sad not letting them loose from time to time. Maybe I can fit a DO 15TBX100 sub into my new room, but maybe I won't even need it with 4x8" woofers from the mains I will be setting up soon. Okay, who am I kidding, of course I will need more woofage. @jay michaelI had to mount 4 braked wheels to my cabs. If I don't engage the brakes after they're set up, the wheels will rattle, but it's a downfiring design. How are yours behaving?

Do you have casters on the back of the cabs? My DIY 21" cabs have slots, which serve as handles inside the horn mouth and wheels on the back (on the hatch, which is almost as big as the entire rear of the cab), which makes them really easy to move around. I imagine the horn mouth of the SKRams would also server as a good handle to throw them onto their backs. I'm sure stacking 3 ain't fun. My back hurts from looking at that stack, the SKRam looks like it's at least 150lbs!

What do you mean by low level? The last measurement was taken at 0dbFS, which produced 6,6V at the Fireface's output. Here is a direct measurement of the FF without the pmillett in the loop (max output 6,6V as before): Best THD is achieved at 0.5V output, best noise floor at maximum. Here is the THD/Noise vs output plot:

Pmillett Sound Card Interface loopback measurements: Measurement chain is Fireface UC → SCI (Generator input) → Internal loopback → Fireface UC The SCI converts the balanced signal of the Fireface internally and outputs either balanaced or unbalanced, which can be switched. It doubles the output voltage, so if I input 2V balanced, it outputs 4V balanced or 4V unbalanced. Voltages seen are after conversion (means the Fireface outputs half the voltage displayed). Measurements are sorted by voltage ascending. The 1V measurement looks similar to the Fireface loopback, so I guess the pmillett isn't adding too much distortion. The pmillett started distorting at about 8.6V output (unbalanced). When I switched it to balanced, the distortion increased a bit, but there was more headroom (presumably twice the voltage). Here is a measurement of the Fireface at 0dbFS, which produced 13,25V at the Pmillett's generator output, which is about 24,6dbU:

I figured out the mains hum, which was a rack power strip mounted above my patchbay in my outboard rack. The following measurement was taken with the power strip switched off: THD looks good, but THD+N still pretty bad, I'm not sure why that is, as I can't really see anything that dirty in the rta there...

The Fireface had been RMA'd once and ever since it seems to reset the connection to the PC occasionally when a ceiling light (LED or Tungsten) is switched on or off, which is very annoying. I suppose there might be something wrong still, which might also cause the mains hum (50hz here in Germany) plus its 3rd harmonic, which is the reason the THD+N gets tanked. I think I should contact RME customer support to confirm whether these results are expected or not. I ran this through my patch bay in the outboard rack, which meant 50ft of cable, but it was balanced so it should not matter much?

I took some new distortion measurements of the interface and the Pmillet Sound Card Interface I'm using. I decided to use REW's RTA to take these, as it gave it more flexibility with window sizes and averaging etc. 0dbV is not correct, but I had to 'calibrate' it to zero, since I couldn't find a way to take the fundamental as reference. Thoughts?

Been doing some tests with my Hypex amps and just out of curiosity I ran them without water in the tank, because I wanted to see how warm the elements got when testing lower power levels. I put the bank on 8R (two elements in parallel) and gave it 50W for a minute. I could still touch the elements after the test was over. They were probably around 50°C (110°F?) at that point. Good news for me, as that means I can test everything below a few hundred watts without having to fill up the tank. I will give it a bit more power tomorrow to see how much the resistance changes, but it shouldn't be much. It's 8.2-8.3R cold and 8R under full load (3KW per element, which would mean an amp with 6KW into 8R would be required to saturate one channel).