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How much SPL do you really need?

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  • #61
    Re: How much SPL do you really need?

    1. More SPL is required in low-bass frequencies than any other.

    3. Big speakers with bonkers efficiency (such as the Abbeys) do not have this problem. There's no excursion, and the woofers don't get anywhere near their power handling capabilities, and the high F3 doesn't hurt either.
    My (2) 15's are higher sensitivity than average: under typical listening the cone excursion is very low. To get a lower F3 as well I had to use large cabs.
    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
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    • #62
      Re: How much SPL do you really need?

      Originally posted by generic View Post
      I hope I don't open up a bad can of worms, but... How do you guys who want to watch a movie at 75db, find 75db? All my source material sounds different and levels are all over the place.

      I can use pink noise to match the main speakers to a sub from a listening position and set the sound to 75db, but if I stick in a movie or CD, at the same volume level, it may or may not be loud enough to play at the same level.

      Do people really try and find the reference level when they watch a movie, or do they just stick it in, and play back at the level they want? Like me, and everyone else I know would do.
      It sounds like you may have a receiver that overrides/ignores the master volume setting when you do your channel calibration. Some units lock the MV at 0dB for test tone calibration and some use the current MV setting when you activate the test tones. Without knowing your unit's operation method and signal level, you can't really assume 75dB on your SPL meter is Reference.

      Strictly speaking, Reference level is the master volume setting where each channel produces 75dB from a -30dBFS signal or 85dB from a -20dBFS signal...IOW, a 0dBFS signal should produce 105dB at the seats if the system is capable. I prefer to use a 3rd party signal source to verify since some units internal test tones have been found to vary wildly from the -20/-30 de facto standards. Naturally, movies will be mixed with different average levels, but all mixing stages should be using the same -20/-30 produces 85/75 for Reference level.

      In my home theater room, movies are always watched at -15dB below Reference (occasionally a few dB louder when I'm alone), which produces peak dBs in the low-mid 90s on bombastic scenes. Even on something like LOTR, with extreme dynamic range and lots of whispered dialog, I don't recall needing to adjust the volume to understand the dialog. Broadcast TV, with its (typically) much narrower dynamic range, calls for a much lower MV setting in the same room...probably -27dB to -30dB.

      Music recording doesn't use a standard for mixing and a lot of current commercial material has an average level in the -3dBFS to -6dBFS range (see "loudness wars); IOW, on my system, the average playback of a CD at -15dB below Reference would still produce an average SPL around 90dB. I'd personally find that way too loud for an extended listening session. For comparison, the 15hp Kohler on my zero turn measures about 93dB at 1' and its annoyingly loud even with hearing protection.

      As always, YMMV and season to taste. ;)



      • #63
        Re: How much SPL do you really need?

        Originally posted by spasticteapot View Post
        I'm going to make a few assertions and see what people make of them. ***
        4. Big speakers with low efficiencies (like the Khanspires) deal with this problem by having far more SPL capability from the bass section than the mids and tweeters. By segregating the low frequencies, it's possible to get sufficient SPL from an ~85dB efficient midrange.
        My experience differs on this point.

        I don't know what the Khanspires are, but I recently had a chance to hear a design called the Statements, which use two 8" Dayton woofers, two 4" (I think) TangBand midranges, and a ribbon tweeter. I was very surprised that, despite the large cone area and volume displacement - both in excess of what my "reference" mains offer - the Statements indeed "sounded loud" as levels increased.

        That there was plenty of power on tap (enough to get them, on paper, to ~111dB, assuming ~88dB/W/m sensitivity, which is well in excess of listening levels used) and we're not talking about huge differences in listening space volume or listening distance.

        Originally posted by spasticteapot View Post
        Of course, I'm just gonna go ahead right now and wonder why the heck we can't get more efficient 5" midranges. ScanSpeak makes one - where's the rest?
        Audax's old HM130Z0 is a really good one, and they sometimes come up on eBay. And there's always, for a price, the Century 500 neo-magnet mid JBL uses on their LSR32/LSR6332, which seems to be a development of their old 500GTi car midwoofer. (There has always been a lot of overlap between JBL's flagship car stuff, and their smaller high-end Pro stuff.) You can order it direct from JBL Pro parts. NOT cheap, though. But it's a fair bet that it's better than the ScanSpeak Disco. Still, the 15M/4624G is an interesting driver on paper, one that looks pretty easy to work with and makes smarter compromises than other currently-available 5" drivers. It might be worth a gamble at its current price. I don't know what tweeter one would match with it, though. Perhaps one of the 6" JBL waveguides Zilch used in his smaller speakers? It is better, IMO, to pad down a tweeter than waste midband efficiency. And always better to match the directivity at the top of the midrange with the directivity at the bottom of the tweeter.
        "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)