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Fast tracking my knowledge of compression driver and throat diameters

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  • Fast tracking my knowledge of compression driver and throat diameters

    What is it we are looking for when matching a compression driver to a waveguide?

    Okay, so it's the inches of the driver say if its 1 inch or 1.4 inch or 2 inch compression driver. Is that the throat diameter which matches the hole in the waveguide?

    Also, can we drill holes in the waveguide to match the bolts on the driver? Or is an adapter a must...? And can we make the hole bigger by sanding it(plastic waveguide)

    Some general info in this will really help.

  • #2
    Might I suggest you research Earl Gedde's work. He hinted a lot about throat impedance. I seem to remember several papers in the AES anthology on the subject. All I know is I don't know anything about it. Horns are for PA, my interest is for living rooms.

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    • #3
      The throat has a specific taper, and that taper continues expanding after it enters the waveguide, so the diameter of the CD opening has to match the diameter of the original opening in the waveguide. You can certainly drill attachment mounting holes in the waveguide flange, that's a free move. And horns are certainly used in living rooms. Mine has a couple big old Altec 511s.
      Francis

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      • #4
        Originally posted by fpitas View Post
        The throat has a specific taper, and that taper continues expanding after it enters the waveguide, so the diameter of the CD opening has to match the diameter of the original opening in the waveguide. You can certainly drill attachment mounting holes in the waveguide flange, that's a free move. And horns are certainly used in living rooms. Mine has a couple big old Altec 511s.
        When you say needs to match the original opening do you mean the taper is a calculated part and how the compression driver attaches needs to cleanly meet the CD's opening?

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        • #5
          Originally posted by Trdat View Post

          When you say needs to match the original opening do you mean the taper is a calculated part and how the compression driver attaches needs to cleanly meet the CD's opening?
          I think I better understood your point. The taper from the compression driver needs match and flow from the driver into the CD. So most compression drivers are made for particular horns.

          Apparently the B52 I have is only a slight mismatch to the DE250 but nothing to worry about. So I will need a totally new CD if I go with a new driver.

          That said, even matching any 1 inch driver with a 1 inch horn is not going to guarantee me the correct taper that extends from the driver into the CD.

          Am I close enough? Lol!!

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          • #6
            And screw drivers are used to open paint cans. The right tool still does a better job.

            Anyway you are a big time horn guy, can you point us to better discussions of throat impedance issues? According to the good Dr, very small issues are the cause of a lot of the "horn" response issues. One thing for him to say so, another to show what they are and how to address them. A foam plug was about all he admitted to. I found AES papers with the math that says why impedance issues are important, just not how to deal with them.

            Klipsh was correct in his relationship between efficiency and distortion and published the math to prove it. Papers from the 40's and 50's on flair geometry made some progress. So, that leaves us with solving the response and resonance problems. Many horns have diffraction issues I see no reason for. Some lens systems do their primary job, but cause response and diffraction issues. Where is their progress on what is good about horns and solving what is problematic? I would think JBL among others would have made some advances. I would like to see something about the horn-baffle relationship. With our 3D printing. would something like asymmetric flairs help with resonance issues without distorting the wavefront shape?

            A couple VOTs and a DC300 could fill a stadium, survive getting rained on, and tossed around the back of the band van. Just not my for living room. I can buy the difference in the days of 12W tube amps, but not today.

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            • #7
              Originally posted by Trdat View Post
              What is it we are looking for when matching a compression driver to a waveguide?
              First off, you generally don't use compression drivers with wave guides, you use them with horns. They're not the same thing. All horns are wave guides, but all wave guides are not horns. Unfortunately the distinction between the two has become blurred by marketing departments.
              As for matching a compression driver to a horn based on throat size, it's not at all difficult. If it's a 1" driver with 1 3/8" thread mounting you use a horn with 1 3/8" threads. With bolt on 1", 1.4" or 2" you use a horn made for 1", 1.4" or 2" drivers.

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

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              • #8
                Originally posted by tvrgeek View Post
                And screw drivers are used to open paint cans. The right tool still does a better job.

                Anyway you are a big time horn guy, can you point us to better discussions of throat impedance issues? According to the good Dr, very small issues are the cause of a lot of the "horn" response issues. One thing for him to say so, another to show what they are and how to address them. A foam plug was about all he admitted to. I found AES papers with the math that says why impedance issues are important, just not how to deal with them.

                Klipsh was correct in his relationship between efficiency and distortion and published the math to prove it. Papers from the 40's and 50's on flair geometry made some progress. So, that leaves us with solving the response and resonance problems. Many horns have diffraction issues I see no reason for. Some lens systems do their primary job, but cause response and diffraction issues. Where is their progress on what is good about horns and solving what is problematic? I would think JBL among others would have made some advances. I would like to see something about the horn-baffle relationship. With our 3D printing. would something like asymmetric flairs help with resonance issues without distorting the wavefront shape?

                A couple VOTs and a DC300 could fill a stadium, survive getting rained on, and tossed around the back of the band van. Just not my for living room. I can buy the difference in the days of 12W tube amps, but not today.
                I very much doubt you've heard a good horn, with a good compression driver, with a properly done crossover etc. People tend to throw a cheap, nasty driver on any old horn and hope everything works out. Generally, it doesn't.
                Francis

                Comment


                • #9
                  Originally posted by fpitas View Post

                  I very much doubt you've heard a good horn, with a good compression driver, with a properly done crossover etc. People tend to throw a cheap, nasty driver on any old horn and hope everything works out. Generally, it doesn't.
                  So is the B52 PHRN 1014 with the B&C DE250 considered a cheap compression driver with any old horn?

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                  • #10
                    Originally posted by billfitzmaurice View Post
                    First off, you generally don't use compression drivers with wave guides, you use them with horns. They're not the same thing. All horns are wave guides, but all wave guides are not horns. Unfortunately the distinction between the two has become blurred by marketing departments.
                    As for matching a compression driver to a horn based on throat size, it's not at all difficult. If it's a 1" driver with 1 3/8" thread mounting you use a horn with 1 3/8" threads. With bolt on 1", 1.4" or 2" you use a horn made for 1", 1.4" or 2" drivers.
                    So follow basic size guides and ill be fine. But essentially, the horn should be made for the size of the compression driver for a good fit.

                    The B52 PHRN 1014 is considered a horn if I am right? But I will look further into the distinction thanks for info.

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                    • #11
                      Originally posted by Trdat View Post

                      So is the B52 PHRN 1014 with the B&C DE250 considered a cheap compression driver with any old horn?
                      No, that's not so bad. The DE250 is about the beginning of listenable compression drivers for hi-fi. I personally hate the sound of titanium diaphragms, but the DE250 is polymer. That waveguide is fine for a waveguide, but like all waveguides doesn't offer horn loading at lower frequencies. That means the intermod is never as good as a decent horn, but for moderate listening levels that might not be audible. Of course, a good crossover is still a big deal. Modern practice (by JBL, for example) uses higher order to stop low frequency stuff from getting to the horn. They often use LR6 (acoustic), but for home use LR4 is probably fine.
                      Francis

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                      • #12
                        Originally posted by fpitas View Post

                        No, that's not so bad. The DE250 is about the beginning of listenable compression drivers for hi-fi. I personally hate the sound of titanium diaphragms, but the DE250 is polymer. That waveguide is fine for a waveguide, but like all waveguides doesn't offer horn loading at lower frequencies. That means the intermod is never as good as a decent horn, but for moderate listening levels that might not be audible. Of course, a good crossover is still a big deal. Modern practice (by JBL, for example) uses higher order to stop low frequency stuff from getting to the horn. They often use LR6 (acoustic), but for home use LR4 is probably fine.
                        Ill be going active crossover DBX 234 balanced version and using software DSP. I know DSP is not magic and there is a lot of experimentation to it but I hope i'll manage to tie it in well. My only concern is the compression drivers ability to play down to about 1200hz so my 15 inch deltalite 2015 won't beam as i think the deltalite is really only good till 1000hz. Hence why I am asking about matching driver with horn as I might go with a better driver or a better horn as well.

                        And of course the quality of the DBX active crossover, hopefully no noise or hiss not sure if it is transparent enough. If you have any experience with the quality of the crossover let me know? Its LR4 so its should be okay.

                        Can you recommend the next horn and driver up that can easily play down to around 900hz?

                        I think for a first PA style project it should be okay.

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                        • #13
                          Originally posted by Trdat View Post

                          Ill be going active crossover DBX 234 balanced version and using software DSP. I know DSP is not magic and there is a lot of experimentation to it but I hope i'll manage to tie it in well. My only concern is the compression drivers ability to play down to about 1200hz so my 15 inch deltalite 2015 won't beam as i think the deltalite is really only good till 1000hz. Hence why I am asking about matching driver with horn as I might go with a better driver or a better horn as well.

                          And of course the quality of the DBX active crossover, hopefully no noise or hiss not sure if it is transparent enough. If you have any experience with the quality of the crossover let me know? Its LR4 so its should be okay.

                          Can you recommend the next horn and driver up that can easily play down to around 900hz?

                          I think for a first PA style project it should be okay.
                          Well, I cross at about 770Hz, but I'm using Altec 511s. Unfortunately, if you want to cross lower, the horn (or waveguide) has to be proportionately bigger, if you expect to have pattern control. The laws of physics won't be denied. Your driver and horn should be fine at 1200Hz crossover. I wouldn't go much lower.
                          Francis

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                          • #14
                            Originally posted by fpitas View Post

                            I very much doubt you've heard a good horn, with a good compression driver, with a properly done crossover etc. People tend to throw a cheap, nasty driver on any old horn and hope everything works out. Generally, it doesn't.
                            You're right again. I have never heard a good sounding horn in a living space. For a PA, if a large space, can't beat them because efficiency is paramount. Small space, give me a line array. Living space, direct radiators. The days of K-horns ( one of the cheap horn and bad crossover of what you speak) Altec and several supposedly high end have all sounded ratty, irregular and edgy. Compare the sound of Buddy Rich band horns with Harry James horn section. Nope, I'll keep my small dome 2-way with sub in my living room. For one thing, it leaves me room to live in the room.

                            "The laws of physics won't be denied." should be a tag line!

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                            • #15
                              I don't know what Altecs you heard. In any event, thousands of recording engineers had (and some still have) Altec 9846s, with 511 horns. I guess they could all have defective hearing. Seems unlikely.
                              Francis

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