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Posts posted by Shredhead

  1. Here is something interesting in the way that REW interprets input levels for folks who may not know...


    This is the highest clean level that a class A/B chipamp can produce @ 30Hz without clipping the waveform:



    Now here is the same amplifier pushed into clipping.  Neither REW's or the soundcard's input was clipped, only the signal into them was. 



    The peak voltage into REW's input does not go any higher when the amp was pushed into clipping because the amp had already reached it's output limit but REW still shows a 1.7-1.8dB increase in level because it senses an increase in RMS level. 


    This is another example for why I think it is less confusing for most people to stick to peak values and not focus on RMS.  After all, the amps are rated in peak power values anyway. 




  2. Oscilloscopes and current/ voltage captures are cool but how do these behave when strapped to a bunch of speakers? That was the point of this to begin with. Let's get away from the test bench captures while driving resistors in a water tank and use a real world load with all of the complexity and possible nastiness of multiple, heavy coil, high inductance drivers driven really hard. FR traces at a volt are useful but no guarantee of maintaining their shape when the amp is asked for full output or when loaded with complex reactive loads.  I don't even care about how clean the amp is or at what point it gets dirty with this type of setup.


    I wrote this in the above post: "The only way to get a clear idea of what you're working with is by looking at the current and voltage at highest and lowest impedances of the reactive load with the amps at their maximum clean level."


    I didn't say that you should have used water heater elements.  Your test was interesting because you were beating the utter fuck out of the amps with hardcore drivers as the load and we learned that they will both go into protection mode in certain conditions as opposed to melting.  You are still left guessing when it comes to which amp put out an undistorted signal at a higher level, whether the amp's clip lights are accurate and where the mute limits are, or where their limits are at 10Hz and below.  Voltage and current measurement tools can help to show a clear picture of amplifier limits. 


    My comment about volts and current is there for folks that might not know anything about amp testing, it wasn't aimed at you.  You post plenty of good data about drivers already, I wouldn't expect you to go all out for 1 amp comparison. 

  3. 900 watts? Why would that present more of an issue than 3600 watts at 4 ohms? I don't get it. If that were the case wouldn't you always want to wire for 8 ohms to max current draw (but with the most resistance?)

    I like to shoot for most power but if you wire too low in impedance then you chance destruction of most amps (or protection circuits turning on).  Fortunately these amps have reliable protections in place so that too much current doesn't cause a catastrophic failure.  All amps produce a maximum voltage and current before overheating or exploding.  How much for both of these maximum values depends on the amp design and amplifiers like these are insanely fucking complicated in design. 


    The only way to get a clear idea of what you're working with is by looking at the current and voltage at highest and lowest impedances of the reactive load with the amps at their maximum clean level.  Bus pumping aside, the ultimate test for these and any sub amp is for how they behave driving a reactive load at 20Hz and under.  This is hands down the most demanding scenario for an amp.  When comparing amplifiers and looking at only this, you pretty much have to start by comparing their looped frequency response and then with that as your reference point, compare their maximum unclipped levels (verified by a scope) and see what the deal is from there. 


    Don't take me the wrong way Josh, I appreciate the thread and I know what a pain in the ass it was.  :)  

  4. My 8 and 6 year old had an argument with almost that exact same use of words.  


    "If you're not going to let me play with your toys I won't want to play with them anyway!!"  


    Josh measured the IPAL in the Othorn but didn't publish the results of any of it.  At the time B&C didn't want him to share any information at all about it, not even him sharing he had the drivers period.


    He said the impedance minimums were at the same points.  


    29-30hz is right where the lowest bass line for my favorite dubstep demo track is, and it basically holds that frequency for 2-3 seconds straight.  59-60hz is right in the wheelhouse for drum kicks.


    I'm fine with it that you don't think I'm approaching 1ohm loads,  but it's up to you to prove I'm not if you're really that concerned about it.  


    No need to get petty about this Luke, you've only been asked to verify your claim which is not out of the ordinary for these discussions.  If you haven't measured your system's voltage and current while playing your demo track then all you have is a theory, which is also fine with us. 

  5. But I really don't have as much time as I used to have to do this kind of stuff.  It may be time for me to step down as a mod here and have someone else take over, I'll contribute when I can, mainly to the BEQ thread if there is still interest.



    Things go in cycles for everyone, things will pick up again.  And what, that was like the ONLY time I've seen Mod action needed since I've been here and no one was put in the penalty box over it and it didn't turn into a big deal.  This place is as laid back as it gets and I dig it. 


    Avengers 2 had better bring it for real this time or I give up on Marvel. 

  6. Stereo track?  Does this include the LFE channel?

    No, I didn't have the stereo track on the BR so this is downmixed to 2ch from surround.  This is the LFE of the surround with a bit hotter of a level.  It's a bit different than the stereo downmix I posted above but pretty much the same.  Doesn't even resemble the laser disc mix here http://data-bass.ipbhost.com/index.php?/topic/12-the-low-frequency-content-thread-films-games-music-etc/?p=9102



    I believe I saw Kval put up a Bass EQ page for this for anyone out there who wants to boost the low end on the bluray for this movie.  http://data-bass.ipbhost.com/index.php?/topic/285-the-bass-eq-for-movies-thread/?p=5599


    For folks that don't know, these are BEQ settings for the people with the HDMI nanoavr.  Andy, you might be interested in this piece of gear so you can get the bluray track of the older flix up to par with the laser discs. 

  7. LFE.1 waterfall of Nostromo, landing on the ALIEN planet. WOW the LFE.1 is deep and high.


    This is the stereo track of the bluray for the same scene.




    I've always thought that laser discs had better mixes of the old flix!  I remember there was a part in the original ghost busters where Sigourny opens up the fridge and that dog thing said Zuel and it had powerful bass on the laser.  The DVD has zip squat. 

    • Like 1
  8. Yo, I forgot to tell you that depending on your settings, that newer version of SL you just got may act buggy.  If it is buggy it will show double what the frequency you input to it, or it will repeatedly show loud transients with no input.  If it doesn't work right, download this version and load the settings into it: http://www.qsl.net/dl4yhf/spectra1.html#download

    -It's the top link zip file.


    Regarding the new color scheme -the spectrum basically has more colors.  Like having more colors on your monitor screen increases the resolution, so does this.  When you get used to the scale you will be able to see more detail in the sound design. 


    Let's look at the ship crash at the end of Prometheus:




    Here is the warp jumps in Star Trek:





    Digging it.

    • Like 1
  9. Hello new here.


    Cool Spectrum Lab thread and useful and indispensable tool for checking how accurate the frequency response is.   


    This one of later GRAVITY with Dolby SR being used on the LFE.1. The few seconds of the opening music to GRAVITY. 




    Dolby SR OFF so straight pass though on my cinema reference home cinema.






    Hi Andy, welcome to databass!  If you turn up the input level to speclab, you will see more resolution of the mix instead of just viewing the peaks of the content you feed it.  Shoot for a strong looking waveform like this and you will get more colors to show up:



    Bossobass came up with a new color scheme for speclab with more resolution that I am really liking.  If you want to download the settings file to load into SL, it is located here: http://data-bass.ipbhost.com/index.php?/topic/435-bossobass-mini-gtg-thread/?p=8831


    This is the first I'm learning of the Dolby SR (spectral recording).  It says on wiki that it boosts dynamic range by 25dB.  That would be quite useful for analog recordings.  Do you know any specifics on how it works? 

    • Like 1
  10.  It was always the same smug dismissiveness anytime mention was made of something that wasn't Jazz in the Pawn Shop, Diana Krall, forty year old yacht rock remasters or whatever the critics' darlings of the month were that seemed to always be immaculately recorded, exceptionally bland albums that managed to be less desirable than listening to a geriatric talk about bowel movements.

    LOL!  I do wish that there were more bands that got to record at the high levels of bands like Steely Dan.  I remember a few years ago I picked up an album from the band Train that was mixed in surround.  I was interested in hearing more of a modern band in the format and it was one of the harshest recordings my ears have ever had to deal with.  It seems silly that we're in the two thousand and ten's and there are still bad sounding recordings being sold.  I guess producing digital audio to sound pleasant isn't as easy as analog was.  I know I've struggled at it.  

  11. These Audacity spectra do seem to have some correlation to what I'm hearing, but how reliable are they?


    Hey man, sorry to hear about the medical stuff.  A string of my family members have logged some ER time lately too and few things are less fun. 


    As far as speclab goes, there is a bug that I know about for the latest version where if your system runs 24bit audio, you have to select 16bit in the settings on SL or it will give you all kinds of crazy noise and stuff.  Maybe it's that? 


    I don't know about audacity but you can loop your soundcard's out to in, use REW to generate different sine tones and see if they register at the same levels on the graph in Audacity. 

    • Like 1
  12. I watched X-Men Last Stand last night and there is scene towards the end of the movie where they goto Jean's house and the whole room is moving from her powers. Seemed like a pretty good run of bass to me, but did not seem that deep. I had the volume a little lower as it was around 10:30pm. Wondering if this scene would fit in here?

    This was the DVD with a DTS ES soundtrack.  The scroll speed was set to 2 minutes. 


    • Like 1
  13. Hey guys, I need some help understanding how the levels rating relates to sub out voltage.  I compared 2 of the hottest scenes in Avatar http://data-bass.ipbhost.com/index.php?/topic/12-the-low-frequency-content-thread-films-games-music-etc/?p=2768 and Earth to Echo http://data-bass.ipbhost.com/index.php?/topic/12-the-low-frequency-content-thread-films-games-music-etc/?p=4883 and this is what the waveform looks like related to voltage levels on the grid which is 500mV per division:




    There should be a difference in levels of around 4dB going by the rating but I think the voltage out shows a bigger difference.  I went to a voltage to voltage level calculator like this: http://www.sengpielaudio.com/calculator-db-volt.htm and when typing in the 2 peak voltages it shows a difference of almost 10dBV. 


    I guess I have no idea what the composite levels in dB are related to.  Will someone please help me understand this? 

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