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  • Scientific and real-world design

    As I continue to read and learn as much as I can about speakers I seem to have questions that don't jive with what I'm learning. In a 2-way (TW) design for example, it seems that woofers no larger than 8" are used. From what I can tell, it seems even a 8" woofer is pushing the limits of a 2-way design. Most 8" woofers (with the exception of very few) tend to break up before 2khz. That makes sense to me. However, what confuses me is a pair of speakers I grew up listening to in the early 80's, a pair of Advents. They were a medium sized floor standing 2-way design with a big 10" woofer. I don't have golden audiophile ears or claim they sounded amazing; however, I thought they sounded pretty darn good. I'm trying to wrap my head around how Advent (and other companies) pulled it off. Or was speaker design still in its "black magic" state back then without scientific knowledge? That or there is a big gap missing between the massive 10" woofer and the tweeter and Advent didn't koow (or even care). This is not a discussin or bash about Advent, just an example

    This kind of falls into my next question(s). In terms of all the graphs and scientific calculations used to create a speaker design. If we go against what the graphs and calculations tell us (weather slightly or in a big way) the design is not worthy of good sound? Does every little dip or peak need to be corrected and flat as a pancake? I guess what I'm saying is should we build a speaker/crossover EXACTLY to the calculations generated from graphs and design programs? Or is it just a way to get us "close"

  • #2
    Most modern (non-"pro") designs today will use a (maybe "soft") dome tweeter - about 1" in dia.
    Your ADVE\TS used the "fried egg" tweeter, which was kinda like a "hybrid" between a small dome (was it about 5/8" ?) and an old-fashioned "cone" tweeter - due to its large half-roll (paper?) surround - giving it the area of maybe a 3" cone?
    That tweeter was crossed much lower than almost any dome can be crossed today (I think they claimed 1500Hz, maybe even as low as 1000?).

    Today, most 8" woofers (which are not even very common for a 2-way) find it hard to reach up to 2k cleanly, where many 1" domes can cross.
    Also, smaller domes (like today's - compared to an old-fashioned 3" cone tweeter, say) can have wider dispersion, which match up off-axis better with smaller woofers (which "beam" more severely as their dia. increases).

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    • #3
      The off-axis response issues of large drivers are just that, off-axis, so for the most part they won't be noticed. That said, one of the reasons for use of the MTM is that a pair of smaller woofers will have better off-axis response than a single larger woofer of equivalent displacement.
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      • #4
        Originally posted by NickA1976 View Post
        ... I grew up listening to in the early 80's, a pair of Advents. They were a medium sized floor standing 2-way design with a big 10" woofer. I don't have golden audiophile ears or claim they sounded amazing; however, I thought they sounded pretty darn good. I'm trying to wrap my head around how Advent (and other companies) pulled it off. Or was speaker design still in its "black magic" state back then without scientific knowledge? ...
        No - The ubiquitous EM loudspeaker has been around since 1927. A lot of fundamental research and implementation happened in the decades after, including the Physics behind the EM "piston".
        Material Science, Manufacturing Advancement and Analysis/Diagnostic tools improved of course along the way, especially since the 60s and later.
        I'd opine that your "bar of expectation" raises through experience; what dazzled you then is an early experience.
        Compare against today's offering and implementation options.
        "Not a Speaker Designer - Not even on the Internet"
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        • #5

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          • #6
            12" frame w/a 10" cone and a masonite 1" wide "ring" to make up the diff. Henry used the larger frame to get more Xmax.

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            • #7
              They were very good for listening to LPs and FM radio. I had a pair.

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              • #8
                Originally posted by Chris Roemer View Post
                12" frame w/a 10" cone and a masonite 1" wide "ring" to make up the diff. Henry used the larger frame to get more Xmax.
                https://www.midwestspeakerrepair.com...am-kit-f10-15/

                Is the measurement from the peak of the surround to the peak of the surround?

                What constitutes an 8", 10", or 12" driver?

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                • #9
                  Originally posted by billfitzmaurice View Post
                  The off-axis response issues of large drivers are just that, off-axis, so for the most part they won't be noticed. That said, one of the reasons for use of the MTM is that a pair of smaller woofers will have better off-axis response than a single larger woofer of equivalent displacement.
                  I have to disagree with this, although you seem to contradict yourself a bit. Were this true, tweeter off-axis "flare" would be a non-issue. Off-axis relates to in-room power response and is certainly a significant consideration as well as better response for anyone not in the "sweet spot".

                  dlr
                  WinPCD - Windows .NET Passive Crossover Designer

                  Dave's Speaker Pages

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                  • #10
                    Originally posted by dlr View Post
                    ... as well as better response for anyone not in the "sweet spot".

                    Never get anything done if I was always stuck in a "sweet spot"

                    "Not a Speaker Designer - Not even on the Internet"
                    “Pride is your greatest enemy, humility is your greatest friend.”
                    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                    • #11
                      Originally posted by dlr View Post
                      I have to disagree with this
                      That's your right. But where the beaming of a too large woofer for the pass band is concerned it will only be obvious if you're far enough off-axis. The average living room isn't going to have a large enough audience sitting far enough off axis for it to matter that much, within reason of course. How tweeter flare figures into the OP's question regarding the use of larger woofers I can't imagine.
                      www.billfitzmaurice.com
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                      • #12
                        Originally posted by billfitzmaurice View Post
                        That's your right. But where the beaming of a too large woofer for the pass band is concerned it will only be obvious if you're far enough off-axis. The average living room isn't going to have a large enough audience sitting far enough off axis for it to matter that much, within reason of course. How tweeter flare figures into the OP's question regarding the use of larger woofers I can't imagine.
                        Bill, the off axis response does matter if you're in a room. The dip from the beaming of the woofer to the crossover with the tweeter will "color" the reflected sound and change the perceived balance of the presentation.
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                        • #13
                          Originally posted by billfitzmaurice View Post
                          That's your right. But where the beaming of a too large woofer for the pass band is concerned it will only be obvious if you're far enough off-axis. The average living room isn't going to have a large enough audience sitting far enough off axis for it to matter that much, within reason of course. How tweeter flare figures into the OP's question regarding the use of larger woofers I can't imagine.
                          Tweeter flare is almost always an issue with largish midwoofers. The off-axis droop of the midwoofer coupled with the strong off-axis at the low end of a tweeter has to be considered. There are too many variables with rooms to ignore the off-axis, listening position and room response. I'm actually a bit surprised with your position on this.

                          dlr
                          WinPCD - Windows .NET Passive Crossover Designer

                          Dave's Speaker Pages

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                          • #14

                            Bill, the off axis response does matter if you're in a room. The dip from the beaming of the woofer to the crossover with the tweeter will "color" the reflected sound and change the perceived balance of the presentation.
                            +1. Look at the work of Toole and Olive on this importance.
                            "Everything is nothing without a high sound quality." (Sure Electronics)

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                            • #15
                              There's importance, and there's importance. I deal with this all the time in pro-sound, and if you think that crossing over from an eight to an one inch dome at 3kHz or so is bad consider going from a fifteen to a horn loaded tweeter at 4kHz, which isn't at all uncommon. Not that I'd ever put my name on a speaker of that sort, but I've designed more than a few for companies because that's what they wanted, and the one who signs the check has the final say. As I already said I'd rather a pair of 6.5s in an MTM to one eight, but one eight will still sound pretty good, and the off-axis dip at the upper end of the eight's range will look far worse on a chart than it will sound.
                              www.billfitzmaurice.com
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