D-MAN Posted June 29, 2004 Share Posted June 29, 2004 ---------------- On 6/28/2004 5:44:16 PM John Warren wrote: Ever hear the expression "much ado about nothing?" applies here. ---------------- John, rodger on that... DM Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 29, 2004 Share Posted July 29, 2004 ---------------- On 6/29/2004 9:43:25 AM mdeneen wrote: John, Ray and Gil have created a great thread here, Chock full of superb information. Would that there would be more like this, and many, many less of the other. mdeneen ---------------- Mark- Just for you. I'm embarking on a series of webpages devoted to this sort of thing. Here's the first page, deals with the motor structure, Qes and Qms. John http://home.comcast.net/~wooferboy/Page_6.html Quote Link to comment Share on other sites More sharing options...
maxg Posted July 30, 2004 Author Share Posted July 30, 2004 Crikey John - what a site!! I had a look at the page you linked to - this will need some serious study to see if I can understand the principles. In the meantime I am a bit mystified by: "A specification that is something worth looking for is the frequency range at full rated output with no more than 1/2% distortion permissible." I should say that I am confused merely in how it relates to my situation. Sorry about the following - it is entirely in descriptive terms as I am not familiar enough with the jargon to use it properly. I do not listen to music at anything like the full power of the amp. Almost all of my listening (99%) is done at less than 90 dB at my listening position, which, if my math is correct, is about 96 @ 1 meter or around 4 watts from the amp with 91 dB sensitivity speakers (mine). Here is the thing. With both my original amps, and the 300B unit I tried, the bass was flabby, slow and generally exhibited all the qualities I would ascribe to a lack of control. With the current amp it is a night and day difference. Switching from one to another is more like changing speakers than amps in terms of the effect on the sound. The newer amp is an experienced Sargeant Major in terms of the way it controls the woofer. Drilling the troops with aplomb if you like. My current theory is that this variation in control is down to the amps ability to cope with high speaker impedance. I have the feeling that my speakers are not at all easy to drive and this is the result of some fairly major impedance swings going on - although I think that they are all upward swings from a minimum of around 4-6 ohms. I have nothing scientific to back this up with - it is entirely conjecture on my part, but I do have another observation that is even more baffling. I have said many times on this forum that my system is good, if not great, for classical, but only average for everything else. I dont think I have ever really explained what the problem is with other music so I will do so now. Several listeners have observed that when playing something other than classical music, for example, Elvis, the voice appears in the centre of the soundstage but at a very low height - abnormally low. This is equally true for many other albums, but not all. This strange effect is not limited to voice - sometimes a guitar or 2 will drop to the floor - ocasionally only for part of a song. Now here is where things get realy weird. As soon as I switch to classical music the soundstage lifts - for all classical music I have tried to date (around 300 albums at a guess). Suddenly we have all the height you could want with depth and breadth going to stunning levels for a box speaker. WTF is going on? My theory is that Classical generally lives in different frequency ranges from the other music and that in these ranges the impedance of the speakers is gentle enough to allow the amp to blossom. Put on rock on the other hand - and the impedance climbs hugely - the amp bogs down - and the soundstage collapses virtically, if not horizontally to the same degree. any thoughts? total BS? No-one here has been able to explain it and it is just accepted that I have a "great for classical" system. Quote Link to comment Share on other sites More sharing options...
richinlr Posted July 30, 2004 Share Posted July 30, 2004 What a great thread! I learned more about damping factors in one read than I have in several years. This brings up a couple of questions for John: 1) What effect does the amplifier's current (not voltage) delivery capacity have on woofer control? My SS amp can deliver 60 amps on a transient peak and I have never had flabby bass. 2) My amp has what is referred to by the manuafacturer as 'servo control' for bass that purportedly allows the amp to exert more control over the woofer. Marketing hype? Since most of us judge by what it sounds like, I can only say that my power amp is truly one of the best sounding amps, solod state or tube that I have heard. By the way my amp's grandpappy is Mati Otala (see Otala Distortion chapter in Dope from Hope). It's TIM is VERY low. Quote Link to comment Share on other sites More sharing options...
John Warren Posted July 30, 2004 Share Posted July 30, 2004 ---------------- On 7/29/2004 8:35:16 PM mdeneen wrote: John--Good Golly Miss Molly! - that's fantastic! What a great site you have there. Did you just bring this site up? Or have I missed this from previous mention? The JBL 2123 project is fantastic - did you do all that woodworking too? Are you finished? How does it sound? That's some really fine information and presentation John. Serious stuff. I'll be checking in there regularly. Mark ---------------- Ha! glad you like it (i.e. find it "amusing"). I put the site up a few months ago. The wood working is mine. I worked in a piano rebuilders shop thru my high school years and even into my first year in college. I only did it becasue I had access to the woodwright's shop so I could build enclosures. The 2123Js sound very good. The section on loudspeaker damping was something I decided to do after reading a paper by Allison on loudspeaker damping. His treatment of damping is very "obtuse" since he leaves the analysis in terms of "acoustic mass" but I liked the approach. I decided to take the same approach but lead it to the expressions that Small uses for Qes and Qms. Quote Link to comment Share on other sites More sharing options...
WMcD Posted July 30, 2004 Share Posted July 30, 2004 I think Dr. John and I are saying the same thing. The damping of the speaker system depends mostly on the magnet strength and length of wire in the field. The amplifier's output resistance and the resistance of the wire is part of the overall performance. None the less, you have to look at the numbers. The voice coil resistance is at about 8 ohms. The wire resistance might be 0.1 or even 0.8 with a long run of thin wire. And the output resistance of an amp might go up to 0.8 Ohms. These are just too little to make a difference in damping. What controls the woofer, or anything else? Certainly it is the amp. I'm not going to say that all amps sound the same. It may well be that a given amp does not perform well with a low impedance woofer. And low impedance is sometimes related to the Bl factor, which is the major player in damping. Overall, the problem may be that the amp does not like the speaker load and performance gets out of whack. I'd like to see some performance curves before signing on to it though. I really wonder about reports that bad bass performance leads to bad "sound stageing". Maybe they occur in the same circumstances of an unhappy amp or a bad recording. That is not the same as attributing bass effects (damping or otherwise) to overall acoustic response. Gil Quote Link to comment Share on other sites More sharing options...
BEC Posted October 21, 2006 Share Posted October 21, 2006 Bump Quote Link to comment Share on other sites More sharing options...
capo72 Posted October 21, 2006 Share Posted October 21, 2006 Thanx Bob. I was not on here the 1st time around. There is some great info in there. Jeremy Quote Link to comment Share on other sites More sharing options...
Guest " " Posted October 21, 2006 Share Posted October 21, 2006 In reference to dampening factor, impedance's, use of resistors and output tap setting changes. There is a lot of info at the below link reguarding the use of autoformers to increase the load an amps see's by increasing the apparent impedance of a speaker. http://www.zeroimpedance.com/ Since speaker impedance is one of the variables in the math formula to calculate dampening factor, increasing the speakers apparent impedance thru the use of autoformers, increases the dampending factor. While the folks at Zero have marketed their autoformer to address this issue, the fact of the matter is Mcintosh has been using autoformers for years even on their SS equipment. Atlas sell's an autoformer call the AF140 and crown sells one as well called the CT170. Both can be found in the 50 dollar per unit price range. I'm currently using a pair of mcintosh 044-244 autoformer's (21lbs each) with my LaScala's and my SS amp. The tap settings I'm using results in 30 ohms of apparent impedance. My laScala's with the ALK extreme slope network are 6 ohms. The SS amp I use in my office has a dampening factor of 60 at 8 ohms. The Amps output impedance is .1325 ohms. Rasing the speakers apparent impedance to 30 ohms thru the use of an autoformer results in a dampening factor of 226. You can use an autoformer to rasie or lower a speakers apparent impedeance. Quote Link to comment Share on other sites More sharing options...
Mike Lindsey Posted October 21, 2006 Share Posted October 21, 2006 Has anyone heard the Khorn with John Warren's JBL mods (two JBL 2123J's/JBL 2404H Bi-Radial Horn tweeter)? I'm curious how it would stack up to the Altec 511B/902 combo. Mike Quote Link to comment Share on other sites More sharing options...
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