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  • Amplifiers....what do you use?

    I was watching a review on the little British monitors which run an class AB amp, which made me think most of my builds I've gone a D or class T chip (In lieu of using a dedicated amplifier unit).

    so in saying that, next monitor build I make and assuming I got active is there any noticable difference to the novice between the boards??

    Also the LBM's look like a cool transmission line of sorts build, just don't like the price tag lol...I could be wrong also but they look like they are running Dayton audio ND series woofers

  • #2
    Well, class D is getting better so I have been told, but I have not cared for any I have heard at any price for mains. Subs, fine. There are a lot of DIY "POPGE" suggestions for the older chip amps, ( Search the DIY chip amp forum) but again, I find them lacking compared to a decent discrete class AB amp. For small monitors, low levels, have you considered class A? Hard to built into a cabinet though. Novice or not, it is your hearing and your sensitivity to distortion that matters.


    Sure TLs are cool, but with the understanding Theil and Small gave us, not really any advantage. They served well back in the 70's when we did not understand how to tune a ported enclosure. Some will never give them up, just as some won't give up their horns.

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    • #3
      I'm very happy with my Wyred4Sound ST500 mk II. I also liked my previous power amp, Quad 909, a lot, and I auditioned and liked a Parasound A23+ not long ago that sounded quite nice. All of these have different design topologies yet performed very well. As to TLs, those that were designed in the 70's never benefited from accurate design/modeling software and were designed with a "by guess or by gosh" method. A properly designed and executed TL can and will perform better than a ported box, provided the woofer is appropriate for a TL, and the design is also based on T/S parameters like a ported box but includes the cabinet's actual dimensions as well as the locations of woofer and terminus (or port if mass loaded), not just the cabinet's volume.
      Paul

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      • #4
        Originally posted by tvrgeek View Post
        back in the 70's when we did not understand how to tune a ported enclosure..
        We understood quite well how to tune a ported enclosure in the '70s. Harry Olson described it in 'Acoustical Engineering', 1940, when bass reflex enclosures were still referred to as Phase Inverter speakers. What T/S gave us was the ability to accurately predict how a given driver would perform in a given enclosure. The math that Neville Thiele used to come up with his parameters was mainly based on the 1959 writings of J.F.Novak, whose work expanded on Olson's calculations. It was very much a chicken versus egg scenario. The vented box, a product of empirical design, came first. The math that defined how it worked came later.

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

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        • #5
          Originally posted by Paul K. View Post
          I'm very happy with my Wyred4Sound ST500 mk II. I also liked my previous power amp, Quad 909, a lot, and I auditioned and liked a Parasound A23+ not long ago that sounded quite nice. All of these have different design topologies yet performed very well. As to TLs, those that were designed in the 70's never benefited from accurate design/modeling software and were designed with a "by guess or by gosh" method. A properly designed and executed TL can and will perform better than a ported box, provided the woofer is appropriate for a TL, and the design is also based on T/S parameters like a ported box but includes the cabinet's actual dimensions as well as the locations of woofer and terminus (or port if mass loaded), not just the cabinet's volume.
          Paul
          Please explain " will perform better"

          Much agree with the A23. I had a stack of 1200 mk II's. Same basic amp, just the Halo is tweeked a bit further.
          Last edited by tvrgeek; 09-22-2020, 10:31 AM. Reason: typo

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          • #6
            Originally posted by billfitzmaurice View Post
            We understood quite well how to tune a ported enclosure in the '70s. Harry Olson described it in 'Acoustical Engineering', 1940, when bass reflex enclosures were still referred to as Phase Inverter speakers. What T/S gave us was the ability to accurately predict how a given driver would perform in a given enclosure. The math that Neville Thiele used to come up with his parameters was mainly based on the 1959 writings of J.F.Novak, whose work expanded on Olson's calculations. It was very much a chicken versus egg scenario. The vented box, a product of empirical design, came first. The math that defined how it worked came later.
            Seems we have reviewed the history before. For practical market understanding , the Ohm C2, circa 1977, I believe was the first mass market design based on T/S parameters. ADL was about the same time. (Small company in Boulder Colorado) Understanding a tuned cavity goes back to the 1880's. Just Theil discovered the root equation's followed the same electrical filter equations and Small figured out the loss factors. Over simplified of course. Bullock and White gave us pre-derived tables DIY could work with. The special case of the port with no mass was figured out earlier and was the basis for the AR speakers circa 1954. Every advance stands on the shoulders of the previous art.

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            • #7
              <https://www.nxp.com/docs/en/data-sheet/TDA1517.pdf

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              • #8
                Amps.

                In use now.
                Sonance buyout amp and Dayton DSP250 sub plate amp for the PC 2.1 Thanks to Wolf.
                Yamaha AVR and Outlaw Audio 2200 for the 5.1 HT.
                Adcom 4 channel and Dayton DSP250 sub plate amp for the Linkwitz LXminis.
                Nobsound 2.1 chip amp for bedside 2.1.
                Nobsound 2.1 BT chip amp for the gift 2.1 system underway (pink).

                I have others.
                Last edited by djg; 09-22-2020, 02:42 PM.

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                • #9
                  QSC RMX850 for the bass, Parasound A21 for the mids, and First Watt J2 for the horn section. Been that way for years, never wanted anything different.
                  Francis

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                  • #10
                    For one, with a TL you aren't always stuck with a 4th-order roll-off below the knee in the response curve, which improves both f6 and f10, even though both ported boxes and TLs are inherently 4th-order systems. Using typical ported box design software, you cannot take into account relative locations of woofer and port to find the optimum location of each (this doesn't matter, of course, in small ported boxes usually) and the optimum tuning frequency; this is especially important for ported floor-standers where the internal height's 1/4-wavelength resonant frequency contributes to the overall tuning.

                    I'm not one that normally likes to "toot my own horn" but I've designed and built for personal use 14 TLs using Martin King's software, some tapered and some mass-loaded, and obtained universally good performance from each that bore out the modeling, not to mention having designed many, many TLs for people literally around the world as well as a couple of handfuls for commercial offerings. If a specific driver doesn't model well in a TL, I have no problem acknowledging that a ported box would be a better choice. To simply dismiss TLs as not worthwhile based on how they were (mis-) designed in the 70's to how well they can be designed today before making one speck of sawdust or one performance measurement is neither true nor fair.
                    Paul

                    Originally posted by tvrgeek View Post

                    Please explain " will perform better"

                    Much agree with the A23. I had a stack of 1200 mk II's. Same basic amp, just the Halo is tweeked a bit further.

                    Comment


                    • #11
                      3Rutu5, Do notice HD goes up as impedance goes down. Actually as current increases. So overkill ( more outputs than one might normally use) is an advantage. I have no idea how a class D works in this matter.

                      Paul, How about data? I hear what you are saying, but still don't buy it. How much is really useable 2 octaves below cutoff? Nada. Totally agree, driver parameters need to match the loading technology. A good ported driver usually is not happy sealed and vice-versa. We calculate EBP for a reason, or at least we should. It does make it hard to direct compare the three enclosures even if you fake the same baffle. I can buy the more distributed cabinet resonances in a tapered TL, but they are not hard to deal with in a box either. I see it as a wash with the back wall tending to be so close to the woofer on most designs.

                      I actually prefer low to critically damped sealed for my woofers as they integrate with the room gain much better. Boxes can get big if not careful driver selection. To boot, I don't need any HP filter for it. ( though easily implemented in the input or VAS stage.) Low Q boxes have an advantage of being very driver tolerance forgiving. A move from .5 to .55 is not going to be noticeable.

                      For mid-bass, I am using a crossover anyway. Think, how may times have you seen a 40 Hz speaker crossed over at 60 or 80? TLs work, and some very fine speakers have been made, no argument. I am not in any way picking on your speakers. For the obvious reason, I have not heard them! But I still see them as obsolete. Give me the volume you used on a TL and I can find a different driver to give even lower cutoff. Ysyally when people rave about a TL is for upper bass or mid clarity. Well, that actually has nothing to do with the loading method. Could be better driver selection, better cabinet reflection controls, etc. Not the low end where the loadings different. TL or sealed, 300Hz is going to be whatever the driver itself is doing! Switch argument to the OB fans on that one.

                      FWIW, have not had difficulty finding optimum tuning freq for years. I use an adjustable port on my prototype. Set as calculated, measure, adjust, repeat as necessary. Calc is usually darn close. I guess one could design a variable length TL or if a fan of stuffing, then a removeable side would work to the same effect.


                      Francis, First Watt on the horns. About as clean an amp as I know of. ( I have thought about one myself) Well, that is what Paul Klipsch asked for years. I heard a different really good Class A on a set of K-horns. Still sounded raggedy and harsh. I'll still grab a horn first for a PA, last for my living room.

                      Comment


                      • #12
                        Originally posted by tvrgeek View Post
                        Ysyally when people rave about a TL is for upper bass or mid clarity. Well, that actually has nothing to do with the loading method. Could be better driver selection, better cabinet reflection controls, etc.
                        Not quite true. With a properly-built TL, you can control both the magnitude and location of in-band peaks and dips caused by vent resonances and their interaction with the driver, in particular the first harmonic resonance, which is the most difficult to kill without also significantly reducing the total output from the vent. Taming these in-band resonances should result in a smoother/cleaner midbass / midrange response. You can't do this with a simple vented box, unless you settle for using a small vent and/or lots of stuffing which brings another set of problems to the mix.
                        Brian Steele
                        www.diysubwoofers.org

                        Comment


                        • #13
                          Originally posted by tvrgeek View Post

                          Seems we have reviewed the history before. For practical market understanding , the Ohm C2, circa 1977, I believe was the first mass market design based on T/S parameters. ADL was about the same time. (Small company in Boulder Colorado) Understanding a tuned cavity goes back to the 1880's. Just Theil discovered the root equation's followed the same electrical filter equations and Small figured out the loss factors. Over simplified of course. Bullock and White gave us pre-derived tables DIY could work with. The special case of the port with no mass was figured out earlier and was the basis for the AR speakers circa 1954. Every advance stands on the shoulders of the previous art.
                          I went to ADL a few times while visiting friends at CU. I had read the JAES articles in my school's library (a bit south of Boulder in Golden) and so talked with the owner. Interesting guy, nice speakers.
                          It is estimated that one percent of the general population are psychopaths - New Criminologist: Understanding Psychopaths

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                          • #14
                            Ahhh, the old what amp do you use question. This seems to pop up every now and then. I have no idea which cheap boards are best, maybe Tom Z will chime in. I use an Aragon 8008, and a first watt f5.

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                            • #15
                              Well if we're talking relatively cheap boards, the Hypex UCD amp boards are very nice sounding. A friend uses them in his active system. They will drive as little as 1 ohm loads.
                              Last edited by fpitas; 09-23-2020, 07:27 AM.
                              Francis

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