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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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DIY, compact, high-output tops

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  • DIY, compact, high-output tops

    What I'd like to make is a pair of "attractive" "compact" passive tops capable of 115 to 120dB average, measured whole-space, and a 65hz F3. Maybe 70, but 65hz would be nicer. That's the aspiration, anyway. I'll be honest, I don't even know if that's possible. I know some commercial options claim even better than that. Even if it's literally possible, I don't know if I can make a good system do that. I guess the only thing to do is focus on the low-end frequency response I want, then make sure I don't have xmax problems.

    Tried modeling a few pro woofers here on PE and xmax issues were apparent with the first few I tried. Gave up on 6" woofers. I did find an 8" LaVoce WAF082.00 that seems to get me there, if WinISD is to be believed. With a pair of them in a 1.2cu ft. box tuned to 72hz, I get an F3 close to 65hz, F6 close to 60, F10 around 55hz. No real excursion issues at full or peak power. I hit xmax at 60hz at peak power. At peak power, WinISD calculates 121-122 dB max SPL.

    Just to see how that is compared to commercial options I looked at the specs on the PreSonus 328ai and QSC K8.2

    328ai claims 133dB peak maximum, 54hz F10, 59hz F6
    K8.2 claims 128dB peak maximum, "Frequency Range" 55Hz-20k, and Frequency Response 59Hz-20k

    Those are both powered, and there's some DSP shenanigans. I assume the low-end gets limited at peak levels. But how does "peak maximum" compare to WinISD max SPL?

    So I guess the next steps are make a driver measurement jig, buy the drivers, measure them, then use speakerworkshop or vituixCAD to make a crossover?



  • #2
    With pro audio the term compact is relative so just how small do you need? There are lots of 2 way boxes with 8" drivers but very few people would employ them for actual PA purposes because they just don't have enough output.. most buy 12" or 15" boxes. Also consider that for a speaker system to be reliable it needs to have a healthy level of headroom, if you have to drive it for all it's worth to hit your target it won't last long or sound it's best, so depending upon the quality of drivers in question you should target somewhere around 75-90% of rated power as the maximum usable long term power. Of course using a pair of 8" or 10" drivers is one way of increasing output and power handling capacity but it introduces other problems with off axis response depending upon how the drivers are arranged.
    Paul O

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    • #3
      I would say most people who just go out and buy a set of 12" PA speakers don't end up with anything capable of higher SPL or significantly lower F3 than what we're looking at, here. Even 15" tops aren't hugely different. I see, and own, a set of dual 15s that aren't even as loud, even if I used a single 8" driver in this design. Granted they're not PA speakers, but I do see a lot of large PA speakers that aren't particularly amazing. It's about SPL not driver size.

      I think, for the purpose they'll be used for, that they'll be overkill 99% of the time. They'll be replacing a set of 6" Cerwin Vega home theater/bookshelf speakers that one would think would be woefully inadequate. And maybe they are.. yet they've been performing adequately, with subs, in rooms designed for like 50+ people. There's something coming up with a few hundred people expected, so an upgrade is definitely required. These particular speakers aren't(probably) going to be playing rap or techno at earbleed concert levels. But I think they could. Right now I just wanted to get some pointers on how to make these a reality.

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      • #4
        speakerhardwaredotcom

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        • #5
          I don't need help cutting the wood. If I do opt for one of Bill's designs, I'd just buy the plan from him and make it myself.

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          • #6
            Originally posted by duronboy View Post
            328ai claims 133dB peak maximum, 54hz F10, 59hz F6
            K8.2 claims 128dB peak maximum, "Frequency Range" 55Hz-20k, and Frequency Response 59Hz-20k
            Don't believe it. First, toss anything that says 'peak'. That's a phony spec right off the bat. Next, companies post 'calculated maximum SPL' numbers. That means they take the base sensitivity and add to that the potential additional SPL possible based on the driver thermal power limit, which ignores the driver mechanical limits as well as both thermal and mechanical power compression. The actual real world figure is likely at least 12dB less than what they claim. WinISD Max SPL does take into consideration the mechanical and thermal limits of the driver, but not either mechanical or thermal power compression. WinISD figures are also half space, as are almost all factory made speakers.

            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              Originally posted by duronboy View Post
              I would say most people who just go out and buy a set of 12" PA speakers don't end up with anything capable of higher SPL or significantly lower F3 than what we're looking at, here. Even 15" tops aren't hugely different. I see, and own, a set of dual 15s that aren't even as loud, even if I used a single 8" driver in this design. Granted they're not PA speakers,
              It comes down to the driver used, PA drivers are more efficient and high quality PA drivers.. the more expensive ones also produce more and better quality output, you do get what you pay for.

              Originally posted by duronboy View Post
              I do see a lot of large PA speakers that aren't particularly amazing.
              Most DJs buy the cheapest speakers they can find.. which aren't amazing. Spending more does buy a better package.

              Originally posted by duronboy View Post
              It's about SPL not driver size.
              Except that it is. Air isn't a very dense medium, a larger diaphram is more efficient at transferring electrical energy into acoustic energy so there is only so much you can get from a single driver of any particular size... all else being equal.

              Originally posted by duronboy View Post
              I think, for the purpose they'll be used for, that they'll be overkill 99% of the time. They'll be replacing a set of 6" Cerwin Vega home theater/bookshelf speakers that one would think would be woefully inadequate. And maybe they are.. yet they've been performing adequately, with subs, in rooms designed for like 50+ people
              Vega makes speakers that blur the lines between home and pro audio so this isn't surprising, but there is a big difference between a room that holds 50 and one that can handle 200. You are talking to the right people here, I provide sound and lighting systems for DJs almost every weekend, I own and use a range of modern powered and passive speakers and have done events ranging form 50-500 both indoors and outside.

              Originally posted by duronboy View Post
              There's something coming up with a few hundred people expected, so an upgrade is definitely required. These particular speakers aren't(probably) going to be playing rap or techno at earbleed concert levels. But I think they could. Right now I just wanted to get some pointers on how to make these a reality.
              OK so a proper 8+1 PA speaker would be an upgrade from what you have now, just know that it will be an incremental upgrade. What exactly do you need help with, driver selection? As mentioned above it does pay dividends to spend more on the drivers and you should also think of this as a 3 way sound system, for an event this size subs are not optional. So those 8's will be the mids and as such they don't need to go particularly low, if the driver and box hit a 70hz F3 that will do it. So the driver you want will be classified as a low/mid and have relatively smooth response up into the khz range where it will get crossed to a compression driver. Will you build a passive crossover or are you thinking active with DSP processing?
              Paul O

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              • #8
                Originally posted by billfitzmaurice View Post
                Don't believe it. First, toss anything that says 'peak'. That's a phony spec right off the bat. Next, companies post 'calculated maximum SPL' numbers. That means they take the base sensitivity and add to that the potential additional SPL possible based on the driver thermal power limit, which ignores the driver mechanical limits as well as both thermal and mechanical power compression. The actual real world figure is likely at least 12dB less than what they claim. WinISD Max SPL does take into consideration the mechanical and thermal limits of the driver, but not either mechanical or thermal power compression. WinISD figures are also half space, as are almost all factory made speakers.
                It's crazy they don't even have to say peak power. I was laboring under misapprehension that peak had to be labeled as such. The QSC K8.2 claims it has a 2000 watt class D amp. Not even an asterisk. There's perhaps a bit more honesty on their spare parts site where they list the replacement driver as being 23.5V, 2 OHM That's 278 watts, right?

                On your DR300s, you mention they can be used with a passive crossover. Does the plan include the schematic for that? Were the advertised SPL graphs made with one in place?

                Originally posted by Paul O View Post
                ...Vega makes speakers that blur the lines between home and pro audio so this isn't surprising
                Don't get me wrong, I love Cerwin Vega and everything,



                ...but these 6" bookshelves aren't blurring any lines between home and pro. My point wasn't that they're awesome, it's that even they meet the current needs. I do believe going from them to even a single 8" pro speaker with 6-12dB+ more sensitivity and five times the power handling is much more than an incremental improvement. I feel that goes beyond my opinion and well into just facts territory. But you're right though, they may not be enough for the upcoming event.

                I'm hoping to come up with a passive crossover. My first custom crossover wasn't that great, but I think it meets budget PA standards. I came up with it on some car stereo website where all you enter is the Le for the drivers, then it spits out a schematic. I hope with all the free crossover design programs with much more sophisticated design processes, I could make something a bit better than my first attempt. I'd still rather not have to, and I'm not even sure I can. I know there are youtube tutorials on some of them, so maybe I can make something good happen.

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                • #9
                  Originally posted by duronboy View Post
                  I'm hoping to come up with a passive crossover. My first custom crossover wasn't that great, but I think it meets budget PA standards. I came up with it on some car stereo website where all you enter is the Le for the drivers, then it spits out a schematic. I hope with all the free crossover design programs with much more sophisticated design processes, I could make something a bit better than my first attempt. I'd still rather not have to, and I'm not even sure I can. I know there are youtube tutorials on some of them, so maybe I can make something good happen.
                  Passive crossovers take some practice and experimentation, you probably have to build a dozen before you start to get an idea of what needs to happen to satisfy your own personal preferences. A speaker will work and not blow up with a very basic textbook crossover but not sound great, then you learn about zobel networks and L-pads, impedance compensation and CD horn correction and the results are much better. Then you hear about baffle step correction after which things really start to sound good, and then you discover measurements and dig into making off axis response as flat as possible. Somewhere along there you might decide to give bi-amping and active processing(DSP) a try and if you have a test mic available you find you can get the results you're looking for in a couple hours instead of a couple weeks, only problem then is finding a way to implement it in a portable manner. You might wonder why you didn't start out this way but when you don't know what you don't know you couldn't have guessed it would be a quicker solution, but then it's only a quicker solution now because you have learned so much and understand what needs to happen to get the results necessary. Almost sounds like a paradox doesn't it. Also makes you wonder how the big manufacturers can offer powered speakers at the prices they do.

                  Paul O

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                  • #10
                    Originally posted by duronboy View Post
                    On your DR300s, you mention they can be used with a passive crossover. Does the plan include the schematic for that? Were the advertised SPL graphs made with one in place?
                    Yes and yes, although I doubt your room has the minimum 800 seats that would make the DR300 an appropriate choice.



                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

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                    • #11
                      Just kicking around ideas. However, I asked my dad(the guy who'll be using whatever speakers I build) what the name of the venue was and found some pictures.



                      He was told the area was well under 10,000 sq ft, but this is... a bit larger. There's a possibility of dividers being employed, smaller buildings on the same property, and a possibility being able to tie into their existing PA. Probably by the time they figure everything out it'll be too late for me to complete even one of those behemoths. Not sure it would be worth it for a one-time thing, either. But it's good to have options. My labor aside, it's only going to cost him a little more than twice as much as the dual 8 idea we were toying with.

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                      • #12
                        A venue like that just screams "LINE ARRAY!" A few smaller line arrayable cabs makes a lot more sense than a couple of large format cabs. Using a pair of dual 8 direct radiators in that room would be like hunting elephant with spitballs.
                        www.billfitzmaurice.com
                        www.billfitzmaurice.info/forum

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                        • #13
                          So a bunch of DR250s, then. I notice most of the SPL graphs are not of the 80hz version. What's the disadvantage of tuning to 80hz? Lower power handling? I'm just trying to figure out the maximum SPL for comparison purposes. If we do it, we'd use the 80hz tuning because we're locked into a 100hz crossover, right now. We're using amps that have a built-in crossovers at that frequency. The possibility of using the speakers without hauling subs for gigs where it's purely a speaking engagement with a little "cheesy church music" is nice, too.

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                          • #14
                            That depends on the content. So does the idea of going without subs. You haven't really made any mention of it. At any rate if you're seriously considering any of my cabs you should be asking advice of those who own them on my forum.
                            www.billfitzmaurice.com
                            www.billfitzmaurice.info/forum

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                            • #15
                              Signed up over there. Says waiting on admin for activation. Parts Express could learn a thing or two...

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