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  • Actual technical requirements vs precieved needs

    Please don't think I am being harsh here of have some above thou wisdom. I know far better. I am old enough to know I am not that smart. I am a new member, though have build speakers and amplifiers for 45 years. I have an engineering background, so not afraid of a number or two.

    I have an observation that may help folks that are newer to this hobby. I see too many attempts to achieve an ideal that is not actually the correct ideal, but intuitive if you have not failed at it before.

    I have seen several threads where one is trying, or suggests they have built, systems with bass extensions very very low. I tested a bunch of CD's and found in most POP music, there is almost nothing below 60 HZ. Jazz a little more and a very few classical pieces down to the long organ pipe of 32 Hz. Even special effects on a DVD, THX spec is 20 Hz. So I ask you, why build a system capable of 15 Hz, as anything below 20 is guaranteed to be 100% distortion! THX spec for the sub crossover is 80 Hz, so building mains that go below 60 or so is just not needed for movies. Serious listening of music, I prefer a lower crossover, but you have to be sure your woofers can push enough air in their lower distortion range. FWIW, I do not fully agree with the THX eq profile, but it is a good place to start.

    I see the same thing on the top. Folks want that nice pretty response to 20K. Well, sorry, unless you are tormenting a dog, not needed. Flat response on the top at the listening point will seem very bright. Another problem is tweeter breakup. Turns out breakup up is typically up there where a 1/3 harmonic is down to your critical most sensitive hearing range so a little breakup, often said to be ultrasonic so who cares, causes IM distortion down at 4 to 8K. Shows up as plain old harmonic distortion. Very bad. Much worse is breakup from your mid or mid-bass as it will add right smack in your critical range.

    I have found low Q subs to work with the room well to provide realistic bass as deep as you can feel. I see zero reason to build a ported sub. I have found using a Zobel on the tweeter not only makes the crossover easier, but will drop the top enough to not cause breakup. Sure, my graphs in free air look weak on both ends, but when you listen to music, they are right. Even dinosaur footfalls come from the dino on screen, not from the subs. If you can identify where a sub is, it is wrong.

    Now, there are actually reasons to build a speaker for below 20. Trying to reproduce elephant calls is one. ( They are inaudible to people) . NASA built a heck of a big horn to simulate a Saturn 5 rocket for vibration testing. I don't see the need for either in my house or car. On the other end, where I had unusual hearing for a male, as I get older I found testing a tweeter I can't hear much above 17K any more. When I was about 20, I was tested @ 22K. It used to be painful to walk into a TV store as the 17K sweep just screamed. Ladies hear a bit more on top than us guys. Unfortunately, between bands in clubs and ear buds, we have two generations with severely damaged hearing. Bummer.

    My lesson here is if you think a little more about the realistic requirements, you will be able to build a much better system. Save your money for bundles of Owens Corning 705 as they are how you create fantastic imaging.

    Just my thoughts. Some learned the expensive way. Some by listening to people far smarter than I.

  • #2
    Originally posted by tvrgeek View Post
    Now, there are actually reasons to build a speaker for below 20. Trying to reproduce elephant calls is one.They are inaudible to people .
    ULF frequencies are inaudible to elephants as well. They sense those vibrations through their feet. https://www.sfgate.com/science/artic...et-2593114.php

    Below 20Hz response is fun to look at on a chart, until you run an RTA with nothing going through the system and still see all sorts of content down below 20Hz. I pick up below 20Hz road noise from a highway a mile away. I can't hear it, my mic can. Many have done an RTA in winter and seen noise below 30Hz that's the same level with and without the system on. It's usually their furnace.

    Even dinosaur footfalls come from the dino on screen, not from the subs. If you can identify where a sub is, it is wrong
    True, but it just means the crossover frequency is too high, allowing directionally locatable frequencies to come from the sub. Mine is a foot behind my LP. Crossed at 80Hz I cannot tell it's there, everything seems to be coming form the L/R/C fourteen feet in front of me and from the surrounds.
    I see zero reason to build a ported sub.
    If the room is small enough for cabin gain to fill in the lower octave I agree, but only then. I see zero reason for a ported sub in a car, as cabin gain there will always be enough to fill in the bottom octave, if not two.
    www.billfitzmaurice.com
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    • #3
      I could not hear his footsteps.

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      • #4
        I've found a Zobel useful to flatten the Z-rise in a mid/woofer so you can rolloff w/a smaller coil (generally).
        Tweeters aren't being low-passed, so no need.
        Actually, the main problem w/a tweeter is its Z-spike at Fs (even worse on non-ferrofluid units). Zobels don't help that. What does is an L-pad (as opposed to simple series-resistance) for attenuation.

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        • #5
          I like the way you are thinking, in general. I think if you have a speaker that can reproduce the 100 to 10k hertz range very well, it can sound very good with most music.

          I have a sealed Dayton PM220 system that has full and natural sounding bass down to 100 hertz or so. I miss those deep rumbles sometimes, but most bass instruments manage to sound very natural. The PM220 also rolls off the highs above 9.5k. They don't have that transparent top end that most people like, but it still works. Cymbals and triangles sound very nice to me.
          Last edited by Billet; 08-02-2020, 03:56 PM.

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          • #6
            My sub does dual duty for music, and home theater. For HT, I want mid teens reproduced, just because it's quite enjoyable with some content. If the music doesn't go below 60hz as you suggested, the sub doesn't suddenly create bass that's not there, so no harm done to the music. It is true that I could be happy with a more modest sub, but an additional advantage is having a sub that is tuned low enough that it doesn't unload below tuning. I have used a sealed ten inch sub, and it performs well. It's clean, and deep in my living room. A movie trailer for a hard core action movie came on one night, and it sounded very good. While I was watching, I remembered that it was a ten, and turned it down before it bottomed out. It was getting close I think.

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            • #7
              Originally posted by Chris Roemer View Post
              I've found a Zobel useful to flatten the Z-rise in a mid/woofer so you can rolloff w/a smaller coil (generally).
              Tweeters aren't being low-passed, so no need.
              Actually, the main problem w/a tweeter is its Z-spike at Fs (even worse on non-ferrofluid units). Zobels don't help that. What does is an L-pad (as opposed to simple series-resistance) for attenuation.
              But you should always use the tweet at least 3X Fs to avoid that problem unless you are still using first order crossovers, which I learned not to do decades ago. I like f-f too. I'll have to think about the L-pad idea. Not sure I see it. I would love to hear your explanation. ( Ill fire up the sim in the morning. Just watching the Dragon return. )

              I can see a single 10 may run out of displacement though some uber price jobs have Xmax in inches. I suggest two at lease in order to make room integration easier. ( a pair make very good monitor stands. We actually these full range speakers. One is just darn hard to get even throughout the room. In my last house with a very large living room/dining etc, I used 2 Peerless 12's. The were coasting with the worst I could send to them, Q of .5 of course.

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              • #8
                You can avoid it and cross very close to Fs with a high enough filter order. Neville Thiele's preference was for fifth order. He felt the additional component count was more than made up for by the wider dispersion that a tweeter provides than a midbass or woofer at the same frequency, and the the higher order also provides better protection and lowered THD via better excursion limiting below the pass band.
                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

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                • #9
                  Originally posted by djg View Post
                  I could not hear his footsteps.

                  Click image for larger version  Name:	IMG_0002.JPG Views:	0 Size:	512.3 KB ID:	1447317
                  Dino needs to get with the program.

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                  • djg
                    djg commented
                    Editing a comment
                    You win this one.

                • #10
                  I've not found that a smaller coil is allowed just because a zobel is used, but it's basically a damped second order. I have found a CR across a tweeter to tame a rising response.
                  Wolf
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                  • #11
                    My two cents worth.....
                    1. A lot of movies have sub 20Hz content
                    2. Low C on an 88 key piano is 32ish Hz. Low C on a large pipe organ is around 16Hz
                    3. 3 times the Fs for a tweeters crossover frequency is what a lot of manufacturers, during the 70s and 80s, used with first and second order crossovers. This was a guideline given to the engineers to reduce warranty claims.
                    4. Take THX specs with a grain of salt. Have you ever actually been able to read the spec? No, because it's not published, it's a proprietary testing and specification document that you get to read after you sign a NDA and write a big check. A lot of it has to do with audio manufacturers marketing department wanting that logo. A lot of equipment doesn't have the THX logo but certainly performs at or above the THX specs.
                    5. I have my vented subs high passed at 20Hz just to keep the excursion under control. Sealed subs just weren't cutting it. Not enough low end extension. My sealed subs now sit behind the TV and just run from 70 to 150 Hz. Speaker to line level adapters from the front and center channel are combined in DSP. This allowed me to go sealed for the front and center speakers and get the enclosure sizes down without worrying about localization issues. It did add another layer of complexity to the electronics.
                    6. See a rocket launch if you can, the closer the better. It's kind of indescribable. It overloads your senses. I saw a few launches in late 60s and early 70s. Thanks Dad!

                    The bottom line is everybody is different. If a couple of sealed subs works for you, great. I've finally stopped striving for that last little bit of perfection. I don't need the last few HP out of the car. The rifle is accurate enough for my skill level. The media center sounds pretty damn good, I'll let Audyssey handle the last final tweeks. It took a while to shed a lot of the anal retentive engineer in me but I have more time to actually enjoy the fruits of my labor.

                    Comment


                    • #12
                      Originally posted by tvrgeek View Post
                      Please don't think I am being harsh here of have some above thou wisdom. I know far better. I am old enough to know I am not that smart. I am a new member, though have build speakers and amplifiers for 45 years. I have an engineering background, so not afraid of a number or two.

                      I have an observation that may help folks that are newer to this hobby. I see too many attempts to achieve an ideal that is not actually the correct ideal, but intuitive if you have not failed at it before.

                      I have seen several threads where one is trying, or suggests they have built, systems with bass extensions very very low. I tested a bunch of CD's and found in most POP music, there is almost nothing below 60 HZ. Jazz a little more and a very few classical pieces down to the long organ pipe of 32 Hz. Even special effects on a DVD, THX spec is 20 Hz. So I ask you, why build a system capable of 15 Hz, as anything below 20 is guaranteed to be 100% distortion! THX spec for the sub crossover is 80 Hz, so building mains that go below 60 or so is just not needed for movies. Serious listening of music, I prefer a lower crossover, but you have to be sure your woofers can push enough air in their lower distortion range. FWIW, I do not fully agree with the THX eq profile, but it is a good place to start.

                      I see the same thing on the top. Folks want that nice pretty response to 20K. Well, sorry, unless you are tormenting a dog, not needed. Flat response on the top at the listening point will seem very bright. Another problem is tweeter breakup. Turns out breakup up is typically up there where a 1/3 harmonic is down to your critical most sensitive hearing range so a little breakup, often said to be ultrasonic so who cares, causes IM distortion down at 4 to 8K. Shows up as plain old harmonic distortion. Very bad. Much worse is breakup from your mid or mid-bass as it will add right smack in your critical range.

                      I have found low Q subs to work with the room well to provide realistic bass as deep as you can feel. I see zero reason to build a ported sub. I have found using a Zobel on the tweeter not only makes the crossover easier, but will drop the top enough to not cause breakup. Sure, my graphs in free air look weak on both ends, but when you listen to music, they are right. Even dinosaur footfalls come from the dino on screen, not from the subs. If you can identify where a sub is, it is wrong.

                      Now, there are actually reasons to build a speaker for below 20. Trying to reproduce elephant calls is one. ( They are inaudible to people) . NASA built a heck of a big horn to simulate a Saturn 5 rocket for vibration testing. I don't see the need for either in my house or car. On the other end, where I had unusual hearing for a male, as I get older I found testing a tweeter I can't hear much above 17K any more. When I was about 20, I was tested @ 22K. It used to be painful to walk into a TV store as the 17K sweep just screamed. Ladies hear a bit more on top than us guys. Unfortunately, between bands in clubs and ear buds, we have two generations with severely damaged hearing. Bummer.

                      My lesson here is if you think a little more about the realistic requirements, you will be able to build a much better system. Save your money for bundles of Owens Corning 705 as they are how you create fantastic imaging.

                      Just my thoughts. Some learned the expensive way. Some by listening to people far smarter than I.
                      Still butt-hurt that I called you out on some of your opinions. Pretty thin skinned and now you're going to rally the troops.
                      Some people are perfectly happy with their home-theater-in-a-box they just purchased from WalMart. And you apparently are perfectly happy with a bookshelf sized Seas monitors and single Peerless sub. Maybe it is a great system, maybe not. As long as you are happy is all that counts and I'm happy that you are happy with your system. Enjoy it and the realistic requirements it produces.
                      http://techtalk.parts-express.com/fo...khanspires-but
                      http://techtalk.parts-express.com/fo...pico-neo-build
                      http://techtalk.parts-express.com/fo...ensation-build

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                      • #13
                        Originally posted by devnull View Post
                        My two cents worth.....
                        1. A lot of movies have sub 20Hz content
                        2. Low C on an 88 key piano is 32ish Hz. Low C on a large pipe organ is around 16Hz
                        3. 3 times the Fs for a tweeters crossover frequency is what a lot of manufacturers, during the 70s and 80s, used with first and second order crossovers. This was a guideline given to the engineers to reduce warranty claims.
                        4. Take THX specs with a grain of salt. Have you ever actually been able to read the spec? No, because it's not published, it's a proprietary testing and specification document that you get to read after you sign a NDA and write a big check. A lot of it has to do with audio manufacturers marketing department wanting that logo. A lot of equipment doesn't have the THX logo but certainly performs at or above the THX specs.
                        5. I have my vented subs high passed at 20Hz just to keep the excursion under control. Sealed subs just weren't cutting it. Not enough low end extension. My sealed subs now sit behind the TV and just run from 70 to 150 Hz. Speaker to line level adapters from the front and center channel are combined in DSP. This allowed me to go sealed for the front and center speakers and get the enclosure sizes down without worrying about localization issues. It did add another layer of complexity to the electronics.
                        6. See a rocket launch if you can, the closer the better. It's kind of indescribable. It overloads your senses. I saw a few launches in late 60s and early 70s. Thanks Dad!

                        The bottom line is everybody is different. If a couple of sealed subs works for you, great. I've finally stopped striving for that last little bit of perfection. I don't need the last few HP out of the car. The rifle is accurate enough for my skill level. The media center sounds pretty damn good, I'll let Audyssey handle the last final tweeks. It took a while to shed a lot of the anal retentive engineer in me but I have more time to actually enjoy the fruits of my labor.
                        I suggest, if your sealed were not cutting it and your ported with HP @ 20 are, it is more to do with the specific systems you built. Only you know for sure.

                        Higher crossover to tweeters is not only getting away from Fs, but has more to do with power handling and distortion. Some need to be even higher. HDS and XT25 as examples. Both superb if used well, both really bad if not. Some SB and Seas you can get away with a bit lower. Horn loading helps but a tweeter with enough excursion to push enough air low is subject to teeter-totter. The higher SPL you want, the higher the crossover you had better do. So it depends on your use. The old rules of thumb are still a good place to start. Drivers doing no more than a decade for instance.

                        I avoid very high sound levels. I like my hearing. Old age takes enough toll, so no need to push it.

                        PS: I need that last HP, but I drive a 65 MG, so every one is important.

                        Comment


                        • #14
                          Originally posted by Kornbread View Post

                          Still butt-hurt that I called you out on some of your opinions. Pretty thin skinned and now you're going to rally the troops.
                          Some people are perfectly happy with their home-theater-in-a-box they just purchased from WalMart. And you apparently are perfectly happy with a bookshelf sized Seas monitors and single Peerless sub. Maybe it is a great system, maybe not. As long as you are happy is all that counts and I'm happy that you are happy with your system. Enjoy it and the realistic requirements it produces.
                          Chill out. This is more about new builders targeting unrealistic goals on this and other forums I have visited. Helpful hint from 45 years of building speakers, not an attack.

                          Comment


                          • #15
                            I do not really want to add fuel to a fire, but the 2 or 3x crossover recommendation for tweeters is outdated advice. Many modern tweeters have extremely high thermal and mechanical power handling, well-tuned rear chambers, etc. It is not uncommon for some robust tweeters to cross less than 2x the Fs. Measurements help quite a bit there, targeting the impedance peak at Fs with a notch (if needed) and understanding how to take and interpret distortion measurements really render the old RoT advice moot.

                            As far as bass extension needs go, modern movies definitely have content in the infrasonic range. Most of us cannot afford the space, money, or both to get the swept volume in-room to adequately reproduce 10Hz at reference levels so we compromise and shoot for 20-30Hz in-room extension. Sealed subs can work well for that if the size of the room coincides with the rolloff of the sealed sub to get some gain there. Probably better to build to go low and EQ it from there. Bass is a complex topic that really doesn't lend itself well to one line rules. Just too many variables to consider.

                            HF extension is something that even people with reduced hearing can recognize in a tactile fashion, again - fairly complex subject. I cannot "hear" 18K, but my ears do pressurize when playing a 18K tone at moderate to high volumes so something is happening that enhances my listening/hearing. A simple analysis of a waveform shows there is content up to and beyond 20K in quite a bit of music.

                            At the end of the day, we all decide on our compromises. Whether we acknowledge them as compromises or attempt to describe them as "correct design theory" is entirely up to us, but realistically - speaker design and install is a series of deviations from a mathematical ideal. Lucky for us, many of those compromises impact our enjoyment minimally.
                            Don't listen to me - I have not sold any $150,000 speakers.

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