vnzbd Posted January 28, 2012 Share Posted January 28, 2012 I am in the process of recapping Quartet x-overs with caps from Bob C. I am thinking about doing the low pass coil also and would like an education on air vs. iron core. I did read the thread that had great input from Bob C, Al K, and Dean G. Very interesting but I felt that there was not a clear winner in the end. Maybe a clear winner would be impossible anyway. All opinions are welcome. The Quartet has a rather large inductor, 4.0 mH. I have looked at offerings from Parts Express - Erse Super Q,iron core, $23 and a Jantzen air core, $40. North Creek is very proud of thier product, pricing starting at $80. Trying to avoid the snake oil while achieving best bang for the buck. Thanks Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 28, 2012 Share Posted January 28, 2012 The larger the gauge the lower the DCR. Air core does not saturate. Iron core saturates. Air core is influenced by adjacent magnetic fields. Iron core is not influenced by adjacent magnetic fields. If you can spring the cash for large guage air core and install it away from magnets, that would be best. If cash is a consideration and / or your limited in where you can install, go with iron core. 18G is small for woofer inductors (radio shack). 16 - 14 would be min (parts expess). wow factor comes in when you get into the 12 to 10 guage aire core inductors (north creek). Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 28, 2012 Share Posted January 28, 2012 I did read the thread that had great input from Bob C, Al K, and Dean G. Very interesting but I felt that there was not a clear winner in the end. Maybe a clear winner would be impossible anyway. You're correct, a clear winner would be impossible. Any engineered product will balance the various factors to come up with an acceptable compromise. Just depends on which particular factors are important to you, and the size of your wallet, which way you should go. I have forte II w/ Bob's complete new crossovers, and he used an iron core for the woofs. Seems to work for me (I think that by the time such things as saturation occur I would have long blown out my own eardrums). Trying to avoid the snake oil while achieving best bang for the buck. Always a good approach. Save your money for more cds, records, and concert tickets! Quote Link to comment Share on other sites More sharing options...
DavidF Posted January 28, 2012 Share Posted January 28, 2012 I am in the process of recapping Quartet x-overs with caps from Bob C. I am thinking about doing the low pass coil also and would like an education on air vs. iron core. I did read the thread that had great input from Bob C, Al K, and Dean G. Very interesting but I felt that there was not a clear winner in the end. Maybe a clear winner would be impossible anyway. All opinions are welcome. The Quartet has a rather large inductor, 4.0 mH. I have looked at offerings from Parts Express - Erse Super Q,iron core, $23 and a Jantzen air core, $40. North Creek is very proud of thier product, pricing starting at $80. Trying to avoid the snake oil while achieving best bang for the buck. Thanks Disclaimer is that I have not read the thread you mention. The answer you seek may be hard to nail down since it becomes how far you want to go in terms of cost and benefit. I use the Erse laminated coils as the best compromise of cost and very low impedance. A North Creek 10 gauge at the cost of $160 each or an Erse at $23, both about 0.2 ohms. I cannot justify the added expense. On the other hand if I operated at very high sound levels I would be forced to reevaluate. Laminates are OK up to a point until saturation becomes a real problem. So if high sound levels are in play and minimum impedance is the goal then the expense for low gauge air coils has to be considered. Then again at this price point the idea of biamping should be considered with the added benefit of no inductor at all to limit amp damping on the woofer. If you are going to invest serious money to mitigate the effect of inductors why not eliminate them altogether? So for me it does not make sense to spend $300 plus on two coils. Quote Link to comment Share on other sites More sharing options...
moray james Posted January 28, 2012 Share Posted January 28, 2012 Large gage air core inductors are expensive but they do sound better. Are they worth the added cost? Well if you have not compared it's kind of hard to make that decission. Ask a forum member who has tried a good number of them (SET 12). You can read his thread over at AK it is a long one but has a wealth of valuable information. Best regards Moray James. http://www.audiokarma.org/forums/showthread.php?t=159340&highlight=forte+crossover+mod Quote Link to comment Share on other sites More sharing options...
vnzbd Posted January 28, 2012 Author Share Posted January 28, 2012 Thanks for the replies. Good food for thought. I have read about SET 12 and his x-overs are something else. The rest of my gear is decent but not extreme so I am not sure if I would hear that big of a difference. The caps being used in the rebuild are of a certain quality and I guess I feel the North Creeks may be in another league altogether. I will do some reading on the AK forum. Thanks Quote Link to comment Share on other sites More sharing options...
moray james Posted January 29, 2012 Share Posted January 29, 2012 I agree with Dan that inductors are going to have a larger sonic impact than capacitors will. I think that if you wanted a general rule to go by then purchase the largest gage solid core air core inductors which you can afford and which will fit. Once you listen to some lagrer inductors I am sure that you will get the itch to try even larger ones at some time later. 14 gage would be an ok place to start as far as size and cost go. Good luck and best regards Moray James. Quote Link to comment Share on other sites More sharing options...
djk Posted January 30, 2012 Share Posted January 30, 2012 If you don't want to have to re-balance your mid and HF with the woofer you had best make sure that the DCR of your new inductor is the same as the stock inductor. Ask Dean G about the inductors in the RF7 and what happened to the bass. Quote Link to comment Share on other sites More sharing options...
Deang Posted January 30, 2012 Share Posted January 30, 2012 lol. I do not like to mess with the OEM inductors in low pass systems. There is a mathematical relationship between the cabinet volume, ports, and drivers -- using an inductor with a lower DCR ruins the model. If you change out an iron core or steel laminate with an air core, you will need to keep the DCR the same, and if you do, you will hear no improvement -- so there is no point in spending the extra money. You will get more improvement using room treatments and experimenting with placement. Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 30, 2012 Share Posted January 30, 2012 I have read about SET 12 and his x-overs are something else Indeed. For that kind of dough I'd be considering a DEQX, and go properly active. Quote Link to comment Share on other sites More sharing options...
moray james Posted January 30, 2012 Share Posted January 30, 2012 Dean: I have to admit I am not the guy to fly a calculator or a computer. I have heard comments like this for decades but on all the crossovers which I have heard which were modifird I have be positively impressed. So how about you take a Forte as an example and run the numbers through the equation and show us stock and modified, use a reduction of DCR of say 1/8 value of the stock inductor so we can see the damage. Lets not forget that air core inductors don't suffer hystersis distortion as all cored inductord do. Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
djk Posted January 30, 2012 Share Posted January 30, 2012 Messing with the DCR changes the effective Qes of the driver, and thus the Qts. Box volume is a function of the square of the Qts, so messing with the DCR of the inductor messes up the bass. It's a bigger problem with low Qts drivers. Quote Link to comment Share on other sites More sharing options...
DavidF Posted January 31, 2012 Share Posted January 31, 2012 ".. Lets not forget that air core inductors don't suffer hystersis distortion as all cored inductord do. Best regards Moray James. The same as with cored autoformers and amp transformers, I wonder? Quote Link to comment Share on other sites More sharing options...
moray james Posted January 31, 2012 Share Posted January 31, 2012 Thanks Dennis: so you have a reference or a link to the formula or better yet an applet? I would like to try and run some numbers and see what is happening. t regards Moray James. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted January 31, 2012 Share Posted January 31, 2012 Changing the DCR of an inductor while keeping the inductance the same affects it's impedance and will shift the crossover frequency. Quote Link to comment Share on other sites More sharing options...
Groomlakearea51 Posted February 2, 2012 Share Posted February 2, 2012 I'd stick with Dean's recommendations as a base line for selection of an air core, if in fact it will make a difference at all. the greatest single improvement to an otherwise quality system will always be to look at the room. Biggest bang for the buck, IMHO Quote Link to comment Share on other sites More sharing options...
moray james Posted February 2, 2012 Share Posted February 2, 2012 Plus 0ne on the room suggestion. Bob C just ran a bunch of numbers over at AK and if you were to drop in a same value inductor which had zero resistance the difference works out to just shy of one db. So it would not seem to be a problem inserting large gage low DCR value air core inductors into your network. Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted February 2, 2012 Share Posted February 2, 2012 Bob C just ran a bunch of numbers over at AK and if you were to drop in a same value inductor which had zero resistance the difference works out to just shy of one db. So it would not seem to be a problem inserting large gage low DCR value air core inductors into your network. Best regards Moray James. Any link to the tests he ran? If he just looked at the voltage drops for different inductors without having them hooked up in a crossover, that might show a slight difference. But in a crossover a coil with a different DCR will have a different Q and will cause a mismatch with the other filter elements. The crossover will work differently with such a change, affecting tonal balance, transient response, and polar response. It would not be possible to predict to what degree these parameters would change as that would depend on which drivers are used in the loudspeaker and the specifics of the crossover design. A fully integrated approach is required for best results. Randomly changing components may result in an audible change, but is that change better? Or just different? Quote Link to comment Share on other sites More sharing options...
moray james Posted February 2, 2012 Share Posted February 2, 2012 Quote: Originally Posted by moray james Hey Bob: can you give an actual calculated example of this? I would be interested to know what the shift would be if one were to switch out the stock Forte bass inductor with a North Creek 8 gage air core inductor. I hear the warnings but I can't find the math or just don't know where to look. The examples that I have heard sounded better to me not worse. What are the changes which take place when inductor DCR is dropped down to the level found in the 8 gage inductors from the typical factory 20 - 18 gage cored units? Thanks for your help. Best regards Moray James. Actually, I was just clearing up a position that Dean holds now. I am of the opinion that the difference is slight and probably inaudible when changing woofer inductors to lower DCR models. When there is a large audible difference, I think that is probably due to improper installation of the large air core inductor. Anyway, here is how I look at the possibility of a large change in bass response when changing out the inductor.Let's take the example of a typical iron core inductor in (for instance) a Klipsch Forte II. We know from the Klipsch schematic that the builder of the crossover is instructed to keep the DCR of the Woofer inductor at 0.4 ohms or less. Let's say that the crossover builder put in an inductor of 0.4 ohms then. OK, we can see that the DCR of the inductor and the impedance of the woofer (4 ohms) then form a voltage divider. Let's assume an input of 1 volt for convenience. So, the ratio is 0.4 to 4 or 0.1. So, we have 0.1 volt across the inductor and 0.9 volts across the woofer voice coil. Now, let's assume we get an impossibly good (on DCR) inductor and replace the factory one with this monster. Let's say it is so good that the DCR is 0. We could then assume no loss at all in the inductor so we get the full 1 volt to the woofer voice coil. Formula for the db change is 20 log (voltage 2/voltage 1)In this case voltage 2 is 1 volt and voltage 1 is 0.9 volt. We then have 20 log (1.1111111) or 0.91514db.The average guy can hear (barely) a change of 1db. In some direct A/B comparisons, some can hear perhaps as small as 0.5db. So, seems to me when we work with changes resulting from lowering or raising woofer inductors DCR, we are working with the possibility of inaudible or barely audible changes. Some will immediately want to bring up things like saturation of the iron core or hysteresis effects. I submit that those are concerns at high power and of minimal effect at normal power levels. In fact, at power levels where these would be a concern, the effects are effectively swamped by other distortion introducing effects like high cone movement of the woofer cone and high temperature effects on the voice coil. Bob Crites Quote Link to comment Share on other sites More sharing options...
Don Richard Posted February 2, 2012 Share Posted February 2, 2012 Just as I suspected, he is considering the change in attenuation only and not the change in the Q of the coil. Q affects the shape of the crossover corner, whether it will be a sharp corner or more rounded. This LPF shape must match properly with the curve shape of the HPF in accordance with the acoustic response of the drivers being crossed in order to work properly. Irregular frequency response in the crossover region will result if done improperly. Quote Link to comment Share on other sites More sharing options...
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