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Bossobass Dave

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Posts posted by Bossobass Dave

  1. At the outset, I've never been a fan of the XXX drivers. Way too big, way too big a box requirement, way too much $$$. Looking more at the HST-18/UXL-18 is more my speed.


    There's not much difference as far as what EQ is required to get flat in your room. It's simple enough to project the HST-18, for example from anechoic to same placement of driver/mic you used to generate the in-room graph posted earlier:




    Done quickly, but I'm not gonna be too far off. A typical humped response (part inductance/part small box) is down around -7dB @ 20 Hz, whereas the low Q drivers are down more like -15dB @ 20 Hz. Pull down the hump of the long throw mid q driver or pull down the top end of the mega-motor low Q driver. A wash in the end, IMO.


    You're showing tons of room gain. Since the Fosgate is down -25dB from cross to 10 Hz

  2. It certainly looks cool but...


    As a candidate for HT, it's mounting depth is prohibitive and, as with any sub driver design, the higher the motor strength, the lower the Qts. It's Q is so low, it never achieves a 2nd order roll off.


    The HS-24 trounces it for 1/2 the price and has far less disparity between the bottom frequencies and cross. A quad of HST-18s in dual, dual-opposed boxes is a far better system for the same dough...


    Etc., etc.



    Just watched the whole flick at reference with the subs running a few dB hot. Stupendous low end. Tons of it. There are 2 scenes that taxed my Raptor system 3. I won't say which until there's a pinned thread, but I will say that one of them has strongest effect frequency content centered at 4 Hz but with a spread of simultaneous freqs to cross. BRUTAL!


    This soundtrack is huge with content to 1 Hz, at least, and the musical score is great as well. Awesome mix. Jumping the gun and voting 5 stars, with it's hands tied behind it's back, and a strong buy, which I shall do tomorrow afternoon. I've been waiting for a soundtrack like this for a long time. I was beginning to think the filter monster had bitten every sound man in the movie biz.

  4. We found Pixels to be no sillier a premise than Avengers or Mad Max or Jurassic World and typical of the majority of the Adam Sandler library.


    As a MWB, the caps speak for themselves. More specifically, the low end effects, which you can see are extremely wide bandwidth, are quite unique and easily discernible as such when audibly scrutinized. It's a heavyweight. I don't know about the level because my system is in test flux and not calibrated and my PC for SL and REW is being replaced and not on line, so I inquired above because it might be required pre-info before the bassheads grab this one and let it rip. ;)


    Sound design and re-recording mixer Steve Boeddeker who did sound design for Tron:Legacy, Hellboy and X-Men has been around the block, working his way up. He goes back to the 90s, including Sound Effects Editor credit for Fight Club. Looking forward to more Design/Mix work from this guy.


    Pixels is a contender for MWB of the year, IMO, script/score/acting quality notwithstanding.

    • Like 2
  5. Interesting!


    I really like the SQ (meaning it's no different than any other decent amp I've heard) and the EQ is great. 


    However, the power output I'm getting from it isn't making any sense to me.


    With the 2ohm tests, I was able to get ~10A per channel without bus pumping.  Increasing the levels to ~10.5A a channel, I'd get bus pumping after ~2 seconds into the tone.  That lines up with the 20A figure mentioned in the review you just posted.


    If the power supply is capable of 20A, why are my 5.5ohm tests limited to about 6A per channel?  Shouldn't I be getting about ~550w per channel instead of ~210w?


    In my tests, regardless of the resistance, I was limited to ~210w per channel without bus pumping.


    What am I missing?  Could this be a software/firmware issue?

    I agree that something is not right. Did you try bridging the amp?

  6. Lab Gruppen (1979) ==> TGI Group (2000) ==> TC Group (2002) ==> Music Group (April 2015)


    Random foreign forum post:


    We have recently evaluated Labgruppen IPD2400 for compact/mobile duties however we found "weak" in every means. It has around ~20A output capability http://labgruppen.com/view-model/ipd-series/ipd-2400?page=spec
    which is hardly enough even for 300W/8Ohms speakers (2 in parallel).
    The XD2500 has 45A or so which is lot more stronger, and you feel it in the headroom too..



    The IPD-2400 is purportedly made in Taiwan. Most user-reviews like it for SQ, size and lower price (vs typical LG pricing), but it's obviously not an output monster.

  7. again, i'm a little foggy this morning, but i think you have to check the current for heating not the watts.


    6148 w into 1.2 r is 86.5 v.  86.5 v divided by 1.2 r is 71 amps.  one channel per driver so 71 amps through each driver.


    5310 w into 4 r is 145.7 v.  145.7 v divided by 4 is 36 amps.  drivers in series so 36 amps through each driver.


    with almost twice the amps, the spl at the listening position was 0.4db louder despite more than twice the watts, indicating almost total power compression past 36 amps.  at least that is what i was thinking.


    Trying to figure out your math here...


    There's "almost twice the amps", but less than 1dB more watts, not "more than twice the watts". Very little compression in dBSPL clocked. Am I missing something?


    The key here is the "more than twice the amps" part. Two things happen as the load increases (impedance is lowered); 1) THD increases and 2) efficiency drops (more heat).


    I think a repeat with SL running would show the difference in THD. Although approximate, the relative difference might be noteworthy, IMO.

  8. Enjoyed this site immensely and thanks to everyone who's given advice along the way. Sold all my gear today so will no longer be able to vote! Pursuing another passion. Really great site here and I've spent many hours following other threads because they hold much interest even though much of it went over my head. Bosso if I can get one of your systems to Australia I might be knocking on your door when I decide to get back into it.


    Having been on many chat rooms and forums over the past 17 or so years, it's always sad to see great contributors to the hobby move on. I understand the desire to follow your passions and laud it, Take care and drop in once in a while, my friend.


    We'll make sure there's a system in the corner stamped "Aj72" waiting for ya. B)

    • Like 1
  9. Your response is disappointing, and you mistake my critical peer review for excessive ego.  You could have tried to explain why my reasoning was wrong or instead admitted that you made a mistake in your calculation.  Instead you ridiculed me.  Engineering is hard, and mistakes are made frequently, even by experts.  Such mistakes can cost a lot of time and money to correct unless they are caught early.  Therefore experienced engineers appreciate and welcome critical peer review that identifies mistakes they made.


    This isn't the only time that I've brought errors to Dave's attention and received insulting responses instead of any kind of acknowledgement that he got it wrong.   As I said, I expect mistakes to be made by all of us from time to time, but I also expect people with integrity to correct those mistakes when they are realized.  Furthermore, you and Dave's ability to support the product you sell (the A-14k) depends on your knowledge of the product and knowledge of the physical principles upon which it functions.  If you cannot distinguish between current flow in the speaker wire and current flow in the mains circuit, how can you possibly understand how the amp works?  And again, I'm not harping on the particular mistake that was made.  We all goof up like this once in a while, but if this were merely a brain fart, then I surely would have seen a response like "oops, I mixed those things up when I did the calculation".  Instead, you/Dave respond like I hurt your feelings or something.  Either you're just screwing around with me, or you guys really don't have any understanding of what you are talking about and are simultaneously unaware of this fact!


    So maybe the $3000 price tag of the SP2 reflects the fact that it's actually engineered by the company that sells it.  Whether that fact justifies the higher price tag over the A-14k is for everyone else to decide for themselves.


    Your argument is stupid.


    Try to misread that as critical peer review. :rolleyes:

  10. If someone else happens to repeat such an issue, we can figure out what was happening as it's a rather rare occurrence vs. the amplifiers out in the field.


    Again, besides the vague comparisons, this is the other point of my posts regarding stupid-heavy loads presented to an amplifier, generally speaking. The scenario is not likely to be repeated because it's not an optimum system configuration. Yes, pro sound is the market for the rackmount amps and no, they never have to reproduce single digit source at max output into <2 ohms from a bridged amp. Why would anyone recommend a system that presents <2 ohms per bridged amp?


    So, maybe you can tell me what I'm missing in the differences between a high voltage, high impedance system vs a high current, low impedance system? Our tests say <3 ohms per bridged amp results in audibly degraded reproduction. Maybe our tests are seriously flawed.


    EDIT: I just caught Luke's post. Congrats, Luke! Great exercise and results. I'm sure Paul will follow up looking for the rest of the details like what mains, distances, one channel driven, etc., but thanks for the great effort. B)


      That sort of burn in and robust protection is part of what makes for the premium cost of the amplifier vs. the cheaper amps produced in China.



    This is the sort of post that prompts a reaction from me. :)


    Where are the parts for this robust protection circuit sourced from, what makes an over-current circuit any more robust or more expensive, what cheaper amps produced in China are you referring to and what makes their protection circuitry my less robust?


    In the context of the discussion, specifically regarding over-current protection, making such a circuit more "robust" simply means raising the peak current value of the circuit before it trips. Nothing superior about it. Nothing so much more costly about it.


    Is it a good thing?


    The output impedance of the A-14K is approximately 0.020 ohms. Say I have 15 feet of 10AWG wire from the amp terminals to the Raptor terminals. That raises the output impedance to 0.35 ohms. Into a nominal 7.4 ohms (Raptor System II), the damping factor is approximately 220. Into a nominal 0.70 ohms, the damping factor drops to 21 and the signal loss increases by at least 5%


    Is that sort of difference in damping factor audible? Is there a quicker rise in THD with the lower impedance load? Does the spike in heat affect the longevity of an amplifier whose cooling scheme may not be considered optimum for higher heat? Is there a change in efficiency as load impedance drops? These are the more pertinent points to address rather than how some protection circuit results in a price that exceeds any amplifier made in China (which translates to virtually every other amp), IMO.


    I'm happy to know that somewhere on the net the FR of the SP amps is posted. Maybe you'll actually follow up and post it here.  We have a thread for that if you're so inclined to add the data there. I fail to see where it is a negative thing in any way to provide the info. B)


    To address the insanely insulting post that any mention of the GTG experience is SP-bashing; the amplifier used at the GTG belonged to a SP OEM manufacturer (or soon-to-be at the time if he wasn't already). No one else there knew much of anything about the amp, especially not a flashing prot light on the back panel. Apparently, David chose not to pursue the cause for personal reasons. So, if anything, I guess it was on you to follow up since you were the only person with tech comments after the situation was mentioned and are also a SP dealer and end-user.


    I've been interested in the SP amps since their launch in their current iterations. The situation at the GTG is being referred to in this thread as one that supposedly should not have occurred or sent shock waves throughout the interwebs. Well, hopefully we have enough on the ball to know that that is nonsense. No one designs protection circuitry for a situation that will never occur, right? We all thought what happened at the GTG was noteworthy. If I were considering purchasing any $3,000.00 amplifier, it's certainly information I would like to be made aware of.


    I think a lot of Brian and have followed his SP career for much longer than probably anyone here and I believe the SP line, as it has evolved to the present time, is an outstanding achievement. I'm just put off by the cheesy comparisons to alternative choices or their countries of origin to justify the price.

  12. I regret my snippy comment.  I shouldn't have said it and I apologize.


    I allowed your posting style, which I would describe as frequently sarcastic and passive aggressive, to put me in a grumpy mood when I posted that.  Won't happen again.  


    Josh had direct experience with an IPAL in an Othorn, so if he tells me the load drops to ~1.1ohm between 25-30hz, why should I doubt him?  Before purchasing the SP amp I was also chatting with Brian, who I found out also had experience with this specific driver, so naturally I had some questions for him.  I also PM'd you about the A14k during this time as that amp was on my list of potentials for this specific project.  


    Do you have some issue with me talking about some of the details of my casual conversations with Josh and Brian?  


    I also don't see the problem with the 90A requirement that delivering 8kw into 1ohm would necessitate.  My limited understanding is that the 8kw figure is a burst/peak wattage number like the rest of the Powersoft output specifications, and I also assume they recommend at least 240v/30A mains for that module.  A 90A draw for a few fractions of a second shouldn't give a breaker that size any trouble, should it?


    If everything about low frequency reproduction could be assumed, this forum would obviously not exist.


    The question is why would anyone design a subwoofer system to operate at 1 ohm nominal. I see no advantages, only disadvantages. How much transient burst current a breaker can allow before tripping is not predictable and not relevant.


    The SP-2-8000 muted when operating on a dedicated 120V-30A line at Brandon's GTG, both channels driving a 1.7 resting Re reactive load. Since Paul and I weren't there to test a SP amplifier (didn't even know one was there until Dave Gage pulled it out of his car and brought it in half way through the GTG), there was little more time and equipment available to do more than measure resting Re and speclab cap the scenes being played.


    I know this; the A14-K amp bridged, driving the series-wired VCs at a resting Re of 3.4 ohms with the same 120V-30A line would have been easily able to damage the HST-24 driver without going into protect.


    There was speculation by Seaton after the fact that it was "line sag", but there was no indication that line sag or brown out was apparent during the rest of the GTG. Still, no measurements were taken. I still don't know if there is overcurrent protection in the SP line of amps or how one would know what is going on with the amplifier since there are no indicator LEDs on the front panel besides a power on LED and the rear panel only has single signal LED and a clip and a protect LED. Protect can mean several things.


    I don't see the difference between the songs being played at the GTG and the song you mention playing, but, there's no data here beyond your description. A speclab cap would be nice. Actually, the mic'd version (that clocked 135dB) and a loop through version for comparison. And, the measurements Paul asked for as well as a FR at the mic that clocked 135dB. That data would be helpful vs the 'so and so says so' kinda answers.


    No one has posted a FR of the amplifiers as well. I really don't get that. It's pretty much the whole shootin' match when making claims about subwoofer reproduction. I know that you filter the low stuff out, but the rest of us don't so it's pertinent to know if the amplifier is doing that for you.


    Since this thread is about the SP amps, I thought it would be nice to get to the bottom of these issues. I mentioned in my first post in this thread that I don't lend any credence to the SP comparison tests and that sort of info is a marketing ploy to justify the relatively high cost of the SP line, IMO. I'm much more interested in the sort of comparison Josh did in this thread, except that there is still a lot of missing data, IMO, YMMV.

  13. 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!!"  



    It seemed obvious to Josh and Brian that the use of this particular driver would cause problems for a lot of amps, and Powersoft eve made an amplifier module just for this driver rated at 8000w into...you guessed it...1ohm.


    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.  



    I missed this gem ^^


    My kids are grown men but when they were young if someone asked them a question they didn't have the answer to they just said "I don't know" or went and got the actual answer. :)


    8,000 watts into 1 ohm requires 90 amps of current. So, you might see why someone reading your name-dropping, spec-citing posts might ask for actual measurements, or might be curious about your 220V/30A circuit and SP 1-6000 driving the iPAL/DIY Horn?


    I appreciate what you've posted as a start.

  14. No amplifier is the perfect solution, as they all still need to pull the power from the wall and the cost can creep up quickly searching for ever more output, but when you consider the ability to run predominantly without a fan, and be nearly bulletproof into any low impedance, the SpeakerPower torpedo family of amplifiers deliver quite a bit for the money spent.




    I agree with this, except for the <1 ohm stuff. Really all that needs to be said.



    I needed the most amp I could get on one set of terminals and the SP can only use one side so that kind of clenched it.


    That's what I'm sayin'. The best you get with SP is a 6KW bridged amp. Adding multiples... can be done with any bridgeable or full bridge monoblock amp, and <1 ohm operation... not much relevance to HT or any audio scenario, actually.

  15. Your argument is stupid.  In so far as mains capability limits performance, supply voltage and amp efficiency will be major concerns.  The SP2 runs on 240V and is 90% efficient.  Put it on a 30 A circuit, and it can supply something like 5000W continuously without tripping the breaker.  Try doing that with a class AB design with ~60% efficiency (generous estimate) that runs on a 120V/30A supply where you'll run out of gas at a measly 1700 W.


    How much does this really matter?  I imagine a lot of amps would overheat before too long with that kind of load.  The class D is dissipating something like 600W, which ain't bad, but still requires some serious fan action in a 1 or 2U chassis.  The class AB is dissipating more like 1150W.  Whew!  That's hot!


    This is a stupid line of argument because the SP2 kicks butt in this category.  A more sensible argument is that long term output capabilities aren't that important because the biggest ULF demands typically occur in transients or very short passages.  Average thermal dissipation rates are much lower in these cases.  Better yet, circuit breakers allow far more current to pass than they are rated for as long as the draw doesn't last too long.  IIRC, a couple seconds at 2-3X rated load is not likely to cause a flip.


    Lastly, to the extent that line sag matters, some amps cope with it better than others, and it is never the "final determinant" so long as the operator is capable of replacing the line with a shorter or fatter cable.


    "Your argument is stupid..."


    What the fuck? Is this Luke using SME's account? :ph34r::lol:


    Into a 0.7 ohm load, no amp delivers 5KW long term or any term on a 30A line, 120V or 240V. At 1 ohm, volts equal amps and 30A is the limit, long term. There may be a 10% safety factor long term in the breaker, not 500%. That was the point of my post. It's not an argument, it's math. The SP-2-8000 was not 240V, it is 120V. On a 30A dedicated line it repeatedly shut down into a nominal 2 ohm load per side using ULF-centric source.


    Brian's test results claim 100% efficiency since the rated output equals the tested output, although no mention of the input signal are cited. Be that as it may, my beef with the test is that he has a 14KW amp (rated, in bridged mode into 4 ohms) and tests only a single channel whereas his SP amps are full bridge amps. The proper comparison is to bridge the amp being compared to, as Josh did.


    Your post is bullshit. (Hey, that was fun. Now I know why you guys like to do it regularly.) If you have the amp, can you post the measurements and the measured frequency response, or is bullshit gonna be all we get here?

  16. Yea I bet that wasn't a ton of fun, but very education nonetheless. I Think the real winner here is Brian who is offering up a world-class amp at a pretty darn respectable price-point.  Bottom line, you aren't going to get close to this performance which much else... I think K-20/sp12000/a-14K are basically the pinnacle for around here....  You are going to get a TON more out of these than you'll see out of a plastic behringer or even my little peavey and crest 7.5....I would love to see a single comparison of either against one of the big dogs though....


    At least you know your house can withstand it though Josh! 


    In reality, the mains is the final determinant for performance. Amplifiers aren't magic boxes. They can only work to the voltage and current limits provided. The long term output is definitely limited by volts * amps = watts. In a perfect world, if your mains can feed 120 volts into 4 ohms, the current draw is 30 amps and the watts is 3600.


    Now, if you present a 1 ohm load, the volts drops to 30V with 30 amps current draw and 900 watts. Push for more and shut down occurs. We saw that at your GTG with the SP amp while playing ULF-centric source.


    Any amp that can handle 30 amps is a great amp, but reality has to be a part of the conversation.

  17. Dedicated 240v 30A.


    So the B&C specs of the driver combined with Josh's impedance measurements of the same driver in the same cabinet just don't do it for you huh?


    If you're gonna cite an impedance minimum at 2 specific frequencies (that aren't from a measurement of the same driver in the same cabinet), and claim there is no problem from the amplifier at that impedance minimum, then you need to show that the amp has no problems at maximum output at those frequencies with measurements that verify the current draw and impedance.


    When you play a soundtrack the impedance is the average of all the frequencies being played, it's not that the lowest impedance is dominant. Even if the amplifier somehow has unlimited current capability (which, of course, it doesn't), your mains limit the current draw.


    So, no, the data presented so far doesn't do it for me. Hope that's OK.


    Josh wrote:


    The driver also presents a very low minimum impedance to the amplifier being a 1 ohm nominal driver with a dcr of 0.7ohm, but again the excessively strong motor increases the severity of the impedance peaks and the net result is a broader, more elevated "base" of the impedance peaks which increases the actual impedance seen by the amplifier system to be higher than would be seen with a driver of lesser efficiency.



    And honestly Luke, if you're gonna continue to answer my Qs with irrelevant one-liners, I'm really not that interested in the data. :rolleyes:

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