omni, you are right;
, or you buy them (just another good idea). All that depends on their internal resistence. Or the type of inductor and manufacturer. All this is maybe unimportant for grant right now. And there is the price, again, let's not forget. 
I was basing my reference on an extremely low distortion air core coil with 1.4 mm wire, 3.90L/mH, 0.67R/Ohm, Pmax/8Ohm 120 W, dimensions(DxH/mm)92 x 39 and a price of EUR 24,90.
grant, I guess you are going for a ferrite core or similar, but lower R? Just fine either.
Do you make the inductors yourself (?)
, or you buy them (just another good idea). All that depends on their internal resistence. Or the type of inductor and manufacturer. All this is maybe unimportant for grant right now. And there is the price, again, let's not forget. I was basing my reference on an extremely low distortion air core coil with 1.4 mm wire, 3.90L/mH, 0.67R/Ohm, Pmax/8Ohm 120 W, dimensions(DxH/mm)92 x 39 and a price of EUR 24,90.
grant, I guess you are going for a ferrite core or similar, but lower R? Just fine either.
Inductors DC should be evaluated in relation to design and used equipment 😉
Just fore the record - just ordered two cheap 12" Mivoc woofers
So now I can make my classic "monitor" with Mivoc 12" ... Focal 5"(kevlar) ... Vifa XT19
Just fore the record - just ordered two cheap 12" Mivoc woofers
So now I can make my classic "monitor" with Mivoc 12" ... Focal 5"(kevlar) ... Vifa XT19
Tinitus, Its' so cool to see you are going to build another speaker system from scratch...........You have an affinity for the Vifa XT-19.............You've mentioned it in some of your earlier posts frequently......You even , I think, recommended it to me, once....At the time it was a bit pricey for me, however I will definately be interested in your progress...................Please keep us posted..........If there is anything I can do to help, let me know..........Inductor.......At one time I priced magnet wire and found an excellent source here in the US, however time constraints and knowhow alluded me, so I opted to purchase the ones on my current crossover { see picture on last post }..........The old debate extolling the virtues of air cores vs. Iron cores will probably go on forever............I believe in air cores for the upper end and was uncertain what to do about the lower region.........So I researched.........While there may be a possibility of Hysteresis or saturation distortion with iron cores, It has been my research that pundits indicate that this occurs only at extremely high power, volume situations { see Zaphs' Website amongst others }.................In the upper midbass and tweeter sections I chose the SOLEN 14 guage air cores.....For lower midbass, and woofer I bought Madisounds "Sledgehammer" iron cores, primarily for the lower DCR values................I probably won't reach ultra high power/volume levels that would cause the problems reportedly inherent in iron cored inductors..........I hope............lol............By the way...........The Solens measured IDENTICAL to each other for their given values at only .02mH above their stated values...........82 measures at .84 and the .47 measured out at .49.........and that's with my small handheld LCR meter..........My meter has a +/- 4% spec, so these Solens were super accurate............Iron cores didn't quite measure to spec, but I have read on this forum that it is difficult to measure iron cores with handheld LCR meters, that you need an inductance bridge for accurate iron core measurements..............Listening tests will have to be the proof for that pudding............Grant, I hope all is going well and look forward to hearing your latest.............Respectfully.......Omni
Hi guys, (I was away...)
Inductor,
thanks for your comments. Unfortunately I haven't had much time to consider the merits of a 1900Hz xo-point (and 400) for my 3way, as you suggest, but I'll look into it soon. Yes, I'll probably use cheapish ferrite cores for the large coils, when I get there!
Omni,
After all the hard work you have done so far, I'm not sure the incorrectly specced coils will yield optimal results. But you never know, you might be pleasantly surprised? Even so, you would probably always wonder what the correct value coils sound like! Its good that you have the swap option. Fingers crossed for Friday!...*I just now read your last message re coils*...very nteresting...thanks! An inductance bridge seems vaguely familiar..., anyway your point about iron cores is noted - I'm sure some engineers in here would know! Yes, I have some news on my project using the same 27TFFC / MCA15 and P25's. I'll email it in a week or two, when you've had a good analysis (and discussion here) of Frankie's performance! Its almost time to celebrate your success!
Tinitus,
Congratulations on deciding to build your new classic monitors! I'm sure they will sound awesome. Re the XT19, you have probably seen this?---> http://www.markk.claub.net/Testing/Tweeter4/tweeter4index.htm ,grant
Inductor,
thanks for your comments. Unfortunately I haven't had much time to consider the merits of a 1900Hz xo-point (and 400) for my 3way, as you suggest, but I'll look into it soon. Yes, I'll probably use cheapish ferrite cores for the large coils, when I get there!
Omni,
After all the hard work you have done so far, I'm not sure the incorrectly specced coils will yield optimal results. But you never know, you might be pleasantly surprised? Even so, you would probably always wonder what the correct value coils sound like! Its good that you have the swap option. Fingers crossed for Friday!...*I just now read your last message re coils*...very nteresting...thanks! An inductance bridge seems vaguely familiar..., anyway your point about iron cores is noted - I'm sure some engineers in here would know! Yes, I have some news on my project using the same 27TFFC / MCA15 and P25's. I'll email it in a week or two, when you've had a good analysis (and discussion here) of Frankie's performance! Its almost time to celebrate your success!
Tinitus,
Congratulations on deciding to build your new classic monitors! I'm sure they will sound awesome. Re the XT19, you have probably seen this?---> http://www.markk.claub.net/Testing/Tweeter4/tweeter4index.htm ,grant
Hi Sreten,
I really appreciated your and Dave's comments in this thread:
http://www.diyaudio.com/forums/showthread.php?threadid=98571
...the light just switched on for me! haha. So with respect to Troels PMS Seas CA22 in particular (attached), I need to compensate my woofers rolloff for room-gain....Wow! Great stuff! I guess cross-linking to other threads makes sense. thanks, grant
I really appreciated your and Dave's comments in this thread:
http://www.diyaudio.com/forums/showthread.php?threadid=98571
...the light just switched on for me! haha. So with respect to Troels PMS Seas CA22 in particular (attached), I need to compensate my woofers rolloff for room-gain....Wow! Great stuff! I guess cross-linking to other threads makes sense. thanks, grant
Attachments
Hi Omni,
I've just had a look at your xo parts layout. The board seems trapezium shaped to match your boxes! Neat! So I'm assuming the distance between adjacent coils is fairly large then as I suppose
the xo will be placed on the lower back edge of the cabinet? I guess they're 'wired' by now. Anticipation is building!......hehe, best wishes for sonic superlatives! grant
I've just had a look at your xo parts layout. The board seems trapezium shaped to match your boxes! Neat! So I'm assuming the distance between adjacent coils is fairly large then as I suppose
the xo will be placed on the lower back edge of the cabinet? I guess they're 'wired' by now. Anticipation is building!......hehe, best wishes for sonic superlatives! grant
Hi Inductor,
I just had another quick look at your xo and I inverted the tweeter also. As I mentioned earlier, I'm still not sure how the 'files' were (kindly) derived for me. Given this then, I had a look at your xo points which are currently at 410 and 1750Hz. Would the 'octave separation' between drivers be sufficient here, please? By this I mean there is only 2 octaves separation between 400 and 1600Hz, which would cause
interference between the drivers?
Respectfully, but, contrary to what you said about making 'it sing', ...wouldn't 1750 be a little low to take best advantage of
the MCA15? I thought (possibly incorrectly) that it might be a little low even for a 2way with a ~ 6.5inch woofer? Troels, in his PMS version 5 xo says that 3800Hz didn't sound right, but at 3000 it was good.
Please tell me if I'm wrong. I had thought that about 2800 M/T xo ( and 280 W/M if possible ) was best for the MCA15 to make best use of its
off-axis response? I'm still learning! thank you for your kind help. grant
I just had another quick look at your xo and I inverted the tweeter also. As I mentioned earlier, I'm still not sure how the 'files' were (kindly) derived for me. Given this then, I had a look at your xo points which are currently at 410 and 1750Hz. Would the 'octave separation' between drivers be sufficient here, please? By this I mean there is only 2 octaves separation between 400 and 1600Hz, which would cause
interference between the drivers?
Respectfully, but, contrary to what you said about making 'it sing', ...wouldn't 1750 be a little low to take best advantage of
the MCA15? I thought (possibly incorrectly) that it might be a little low even for a 2way with a ~ 6.5inch woofer? Troels, in his PMS version 5 xo says that 3800Hz didn't sound right, but at 3000 it was good.
Please tell me if I'm wrong. I had thought that about 2800 M/T xo ( and 280 W/M if possible ) was best for the MCA15 to make best use of its
off-axis response? I'm still learning! thank you for your kind help. grant
Sreten, Hi
Thanks for your speedy reply, which opens up a whole lot of questions ....which I will ask tomorrow, if ok? (its very late here now).
One quick question though please, if you don't mind....(a yes/no would be great!), can LCR DMM's 'accurately' measure *iron-cored* coils?
I don't see how the core could affect the meter? But I could be wrong!
(Assuming DMM +_4% accuracy) I will be buying a DMM soon....
so this would really help me...cheers, and of course, thanks!, grant
Thanks for your speedy reply, which opens up a whole lot of questions ....which I will ask tomorrow, if ok? (its very late here now).
One quick question though please, if you don't mind....(a yes/no would be great!), can LCR DMM's 'accurately' measure *iron-cored* coils?
I don't see how the core could affect the meter? But I could be wrong!
(Assuming DMM +_4% accuracy) I will be buying a DMM soon....
so this would really help me...cheers, and of course, thanks!, grant
Sreten, Thank you for your reply to Grants question about measuring iron cored inductors............As you may be aware, at least on this forum...........the debate is alive and well..............When I measure mine with my handheld LCR meter, I get a value, of say, 7.75 mH and on another particular day, I get a value of 7.6mH............weird stuff.........My air cores measure "dead nuts" accurate...........Grant, yeah, the crossover is trapezoidal in shape, however it will be fitted up at the top of the cabinet, behind the midbass/tweeter chamber...........When I get closer, I will post some pictures of it mounted, along with other views of Frankies profile............this weekend shoud yield more steps closer to his audition.............Grant, Like you I am curious about the LCR meters capacity for accurate measurements, and I have done a search on this forum, and the discussion is there, however no one backs up their statements with conclusive evidence.......So to me, it's still a mystery, at this time...............Tinitus, when you get a moment, could you describe for me, your "likes" of the XT19 tweeter........................Maybe in the future I will build a wife for Frankie........................Respectfully..........Omni
grantnsw said:
First question first. That's not the xover points. You can not look on a table. The xover was made for your drivers and for their internal impedance and inductance (also their sensibility as you must guess). They are here accounted for, as is the electric interference between lower and higher filter parts (inductors and caps) for the mid section, that were published previously. Tables are just good as a starting point. When you go to the Re and Le of a speaker and add caps and inductors all that start changing, including xover points that in this case are 350/1900Hz second order for those same speakers. That's why I wanted to know which where your speakers in the first place. To change speakers with this xover (as for all xovers, you can not just buy one from the shelf) only if they are of the same specs.
Hi Sreten,
Firstly about DMM's and iron-cores - thanks!, its good to know that they will suffice - I'll buy one!
Re: Room gain, 'guff', etc.....
I imagine room gain depends on many factors: size of room, austere or heavily furnished (carpets etc),
speaker/port placement etc....I don't know how important the woofer size is, but for Troels 8" scenario....
its very interesting to me that room gain can be measured and its effect on vented and closed boxes can also be measured. This is why I find your comment "Notice Troels uses room gain to make a
smaller box, rather than more bass" so interesting. In an ideally measured setup, the woofer response is determined to compensate for the room gain. So as you say maybe Troels fudges a little bit for reasons of practicality(?), and your red curve with no 'knee' would offer the smoothest extension in conjunction with room gain. I hope I'm right?
I'm wondering then, if an 'average sized' room with carpet/curtains and the 'usual' furniture would approximate Troels room gain response? And, could I just assume, maybe, that his 'vented box and room gain' response (also in red) of up to 2dB from about 40 to 140Hz is generally usable? Should I (wonder), just factor this in,
in xo simulations? I hope this makes sense. many thanks, grant
Firstly about DMM's and iron-cores - thanks!, its good to know that they will suffice - I'll buy one!
Re: Room gain, 'guff', etc.....
I imagine room gain depends on many factors: size of room, austere or heavily furnished (carpets etc),
speaker/port placement etc....I don't know how important the woofer size is, but for Troels 8" scenario....
its very interesting to me that room gain can be measured and its effect on vented and closed boxes can also be measured. This is why I find your comment "Notice Troels uses room gain to make a
smaller box, rather than more bass" so interesting. In an ideally measured setup, the woofer response is determined to compensate for the room gain. So as you say maybe Troels fudges a little bit for reasons of practicality(?), and your red curve with no 'knee' would offer the smoothest extension in conjunction with room gain. I hope I'm right?
I'm wondering then, if an 'average sized' room with carpet/curtains and the 'usual' furniture would approximate Troels room gain response? And, could I just assume, maybe, that his 'vented box and room gain' response (also in red) of up to 2dB from about 40 to 140Hz is generally usable? Should I (wonder), just factor this in,
in xo simulations? I hope this makes sense. many thanks, grant
Tinitus,
LOL!, I had a good chuckle, hehe
Omni, G'Day!
Strange that the iron cored coils measure differently on different days....really weird! I haven't read any thread's discussion on this, but personally I'd go 100% with Sreten. DMM's probe lead length is reasonable so I can't see how the 'core' could affect the meter. I know you have de-enamelled and tinned the wires....
Omni, I was wondering about the distance between centres of the two top coils please?
Inductor,
Hi, I have always simulated my project with only the Seas MCA15RCY and 27TFFC and Vifa P25WO-00-08's.
I hope I haven't misunderstood you? But I did not consult any tables. What I did was to simulate again, in Speaker Workshop ('SW'), the xo that you very kindly provided with the same data-files I used before, but this time with both the T and M polarity reversed (ie *-*, and woofer *+*). 'SW' shows in realtime the frequency and amplitude etc. Where the woofer and mid curves 'crossed' was at 410Hz and the mid/tweeter lines 'crossed' at 1750Hz. I thought these were the xo points, so this is why I thought it was valid. If I have missed your point , I'm so sorry!
best wishes to all! grant
LOL!, I had a good chuckle, hehe
Omni, G'Day!
Strange that the iron cored coils measure differently on different days....really weird! I haven't read any thread's discussion on this, but personally I'd go 100% with Sreten. DMM's probe lead length is reasonable so I can't see how the 'core' could affect the meter. I know you have de-enamelled and tinned the wires....
Omni, I was wondering about the distance between centres of the two top coils please?
Inductor,
Hi, I have always simulated my project with only the Seas MCA15RCY and 27TFFC and Vifa P25WO-00-08's.
I hope I haven't misunderstood you? But I did not consult any tables. What I did was to simulate again, in Speaker Workshop ('SW'), the xo that you very kindly provided with the same data-files I used before, but this time with both the T and M polarity reversed (ie *-*, and woofer *+*). 'SW' shows in realtime the frequency and amplitude etc. Where the woofer and mid curves 'crossed' was at 410Hz and the mid/tweeter lines 'crossed' at 1750Hz. I thought these were the xo points, so this is why I thought it was valid. If I have missed your point , I'm so sorry!
best wishes to all! grant
Hi,
One should always beware of simulation tools you do not understand.
In this case Troels is using boundary gain, the effect of the speaker
being in the corner of 3 infinite planes, room modes are not included.
There is no ideal general alignment for room gain, there is one for each
sensible possible cabinet volume and in the above case 40L is used.
This does not mean you should use 40L, its a design choice.
🙂/sreten.
One should always beware of simulation tools you do not understand.
In this case Troels is using boundary gain, the effect of the speaker
being in the corner of 3 infinite planes, room modes are not included.
There is no ideal general alignment for room gain, there is one for each
sensible possible cabinet volume and in the above case 40L is used.
This does not mean you should use 40L, its a design choice.
🙂/sreten.
There are many software simulators (and engineers). One can allways choose between Rolls-Royce and Fiat.
Also, if placing coils side by side, turn them 90º because of magnetic field, or they will interfere when in operation.
Also, if placing coils side by side, turn them 90º because of magnetic field, or they will interfere when in operation.
About Troels using a smaller box....
Actually he doesnt - if you look closer you will see that optimum size would have been 40 liter ..... and to get bass response a bit down he actually uses a bigger box, 50 liter .... quite elementary
Actually he doesnt - if you look closer you will see that optimum size would have been 40 liter ..... and to get bass response a bit down he actually uses a bigger box, 50 liter .... quite elementary
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