Steever Posted February 2, 2020 Share Posted February 2, 2020 I have a pair of NHT Classic Four towers which I’m finding pretty hard to best unless I spend significant $ on new speakers. Rather than dropping $5k+ on new speakers, I’m looking at spending about $800 more on these to improve them. I’ve put better wire through them (Kimber 4TC) and have recapped the mid & tweeter crossover with Mundorf Evo oil caps. Inductors are air-cored so I left them alone. I’m now pricing up what I would need for a rebuild of the midbass and woofer board. I’ll be running with Mundorf again for the caps. I’m also thinking about swapping out the ferrite or iron cored inductors for air cores. Values range from about 2.9mH to 10.1 at the bottom. $ is not the issue but space could be. Is it worth the headache/effort to change out? Link to comment Share on other sites More sharing options...
muon* Posted February 2, 2020 Share Posted February 2, 2020 (edited) I have found positive results from moving from iron core to air core, but it also meant moving from what I'd call too thin winding wire to considerably larger gauge wire used in them when I did it. Benefits where more low frequency presence/energy while more layered in texture also....I used Mundorf solid 2mm or 2.5mm air core conductors L200 or L250 series. DCR might be lower so you might end up with a slight hump in the frequency range but that was of no consequence in my view for the benefits that came otherwise. Purists that want the identical measurements in outcome would not do as I do I guess, but then you don't get the benefits I was looking to gain. Edit: the gains where a much more expressive sound from that wire gauge increase. In one case I had the new inductors hanging well outside the edge of the XO board, and in the other case I rebuilt using new boards and connecting all point to point.......to accommodate the larger inductors. Edited February 2, 2020 by muon* Link to comment Share on other sites More sharing options...
muon* Posted February 2, 2020 Share Posted February 2, 2020 Mind you, the ones I was working with were .82mH, that 2.9mH and especially the 10.1mH ones would be big and heavy. Link to comment Share on other sites More sharing options...
Ittaku Posted February 2, 2020 Share Posted February 2, 2020 I use air core 10awg 5.2mH inductors and they are enormous - 25cm across. Space will be an issue. However, these c-coils will be a massive upgrade from regular ferrite cores without the space issues, nor saturation issues, nor DC resistance, with those big values you're looking at: https://www.hificollective.co.uk/inductors/jantzen/c-coil.html 1 Link to comment Share on other sites More sharing options...
muon* Posted February 2, 2020 Share Posted February 2, 2020 17 minutes ago, Ittaku said: I use air core 10awg 5.2mH inductors and they are enormous - 25cm across. Space will be an issue. However, these c-coils will be a massive upgrade from regular ferrite cores without the space issues, nor saturation issues, nor DC resistance, with those big values you're looking at: https://www.hificollective.co.uk/inductors/jantzen/c-coil.html I bet those speakers have a lovely expressive low end 1 Link to comment Share on other sites More sharing options...
rockeater Posted February 2, 2020 Share Posted February 2, 2020 I would improve soldering on the pictured board. It is very dull and possible prone to failure with time. Joints should be shiny and have a lot less solder on them (have no blobs). Link to comment Share on other sites More sharing options...
Full Range Posted February 2, 2020 Share Posted February 2, 2020 This video will help in explaining the difference t 1 Link to comment Share on other sites More sharing options...
mwhouston Posted February 2, 2020 Share Posted February 2, 2020 Definitely pros and cons for each. I started with air core but now I’m winding my own it’s all on ferrite rod. Why ferrite I hear you ask? Well because I can use fewer turns of thicker wire for the same inductance. Lower DC resistance and therefore less signal loss. Also I use long ferrite rods. This means less layers of wire. I wind neat which may also go against the grain for some. If I have less wire and fewer (on some winds no) layers I have less inter-winding and inter-layer capacitance. We are talking inductors here so the less parasitic capacitance the better. There is little to no chance of core saturation because on a single rod there is no closed magnet circuit. It’s an open magnetic cct. A transformer - EI - core, if sufficiently small, can be saturated. Also with trannies they are not ferrite but some iron or iron nickel material. 1 Link to comment Share on other sites More sharing options...
muon* Posted February 2, 2020 Share Posted February 2, 2020 2 hours ago, Full Range said: This video will help in explaining the difference t Bottom line in that vid is that the only compromises with air core using large gauge winding wire is cost and size, iron core compromises are SQ related. 1 Link to comment Share on other sites More sharing options...
Decky Posted February 2, 2020 Share Posted February 2, 2020 Consider foil inductors. https://www.madisoundspeakerstore.com/inductors/ It is all about the space. You will never be able to do just a drop-in replacement parts when upgrading standard commercial speaker xovers for anything that is less than $10K. Above that xovers usually do not need any upgrades. Go with PP film caps, that will make most of the difference. Link to comment Share on other sites More sharing options...
Full Range Posted February 3, 2020 Share Posted February 3, 2020 I went copper foil for more tonal and voice accuracy Get all your crossover needs or have them built by Nigel at speakerbug https://speakerbug.com.au 2 Link to comment Share on other sites More sharing options...
Full Range Posted February 3, 2020 Share Posted February 3, 2020 Ohh If you are wondering how big those inductors are They weigh about 5.5 kg each 8 AWG 2.7 mH And that is a coffee cup saucer as a visual guide 2 1 Link to comment Share on other sites More sharing options...
mwhouston Posted February 3, 2020 Share Posted February 3, 2020 1 hour ago, Full Range said: Ohh If you are wondering how big those inductors are They weigh about 5.5 kg each 8 AWG 2.7 mH And that is a coffee cup saucer as a visual guide One the problems I see with the flat copper is parasitic capacitance, Link to comment Share on other sites More sharing options...
Steever Posted February 3, 2020 Author Share Posted February 3, 2020 (edited) Gee, I’ve learnt lost reading your responses guys. Thanks. I’ve looked into the physical sizes of the 1 and 2mm air cores and even at 4.7mH, they’re about 100x100x80mm. The 1mm are about $30 each and the 2mm, about $130 each. either way, size is prohibitive unless I go external cross overs again. I’d rather avoid this as I already have monoblocks at the base of each speaker and don’t like clutter. most of my serious listening is done at average listening levels and when I do turn up my EDM/IDM playlist, I’m not listening seriously to notice any compression anyway. I know caps make a significant improvement And even though they will be a bit larger than existing, will still do those. Inductors my need to stay as where they would go is currently occupied by reflex ports and 10” woofers. thanks again for the comments everyone. so, now I’m wondering if I can improve on the resistors... edit: Nigel’s Jantzen inductors are smaller, heavier gauge, and less pricey than the Mundorfs. A change out for all but the 10.1 might just be the go after all. Edited February 3, 2020 by Winno 1 Link to comment Share on other sites More sharing options...
Full Range Posted February 3, 2020 Share Posted February 3, 2020 (edited) 7 hours ago, mwhouston said: One the problems I see with the flat copper is parasitic capacitance, Don’t think it’s a problem with the wax inductors that I have chosen And the distance between the parts is greater than the minimum required Edited February 3, 2020 by Full Range Link to comment Share on other sites More sharing options...
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