Hi - I built the M1tlm a couple of yeas ago and always thought that they weren't detailed enough and lacking in treble. So I decided to measure the crossover inductances and obtained the following:
Crossover 1
Bass - 2.4mH
Treble parallel inductor 250.5uH
Treble series inductor 256.4uH
Crossover 2
Bass - 2.4mH
Treble parallel inductor 250.5uH
Treble series inductor 275.4uH
I'm not sure why there would be an inductor in series with the Fountek CD1.0 ribbon, maybe for phase or impedance compensation of the ribbon or even as an alternative to a zobel network?
And why the treble series values would be different as there are no pointers as to what components form the left or right channels.
Even so 250uH at say 5K, in addition to the real DC resistance, is effectively putting another 8 ohms in series with the ribbon which obviously increases with frequency. Surely this is choking off the higher frequencies.
So I'm wondering if Ivan made a mistake on my particular kit or got some inductors mixed up with another kit?
Anyway short of removing this inductor, I have reduced the value to 5uH. This has really brought up the detail and clarity at the top end.
I wonder if the experts can tell me what this inductor is doing, as I've never seen an inductor in series with a tweeter before, Should I remove it altogether as 5uH is only a few turns of wire.
Thanks
I've put inductors in series with tweeters in lieu of EQ. Just because a tweeter seems designed to give a flat response doesn't meant that's the best result for the system.
It therefore has a similar effect to the Zobel (RC) but I wouldn't quite put it that way because the purpose is different.
It therefore has a similar effect to the Zobel (RC) but I wouldn't quite put it that way because the purpose is different.
Yes it's probably to tame the rising impedance of the Fountek cd1.0, but I think as in my previous post, the inductance is way too large choking of the detail. Maybe it would be better to use a zobel? I can post a circuit if required.
It's probably to roll off the higher frequencies (tilt the response). I'm not sure if that's what you mean by choking because it can be a good thing but choking makes it seem bad?
I can imagine the schematic, unless you mean something unusual. Would it help if I posted some generic simulations of the response changes?
I can imagine the schematic, unless you mean something unusual. Would it help if I posted some generic simulations of the response changes?
Choking - (as in strangulation) I meant considerably reducing the hf output of the tweeter as the frequency increases.
The crossover is a fairly standard 2nd order circuit but with the addition of inductor L3 in series with the tweeter.
Here is more detailed information
R1 = 4R2
R2 = 3R
L1 = 2.4mH
L2 = 250uH
L3 = 256uH or 275uH in the other crossover
It would be interesting to see what the response curve looks like with the Fountek CD1.0 ribbon tweeter
Thanks
.
The crossover is a fairly standard 2nd order circuit but with the addition of inductor L3 in series with the tweeter.
Here is more detailed information
R1 = 4R2
R2 = 3R
L1 = 2.4mH
L2 = 250uH
L3 = 256uH or 275uH in the other crossover
It would be interesting to see what the response curve looks like with the Fountek CD1.0 ribbon tweeter
Thanks
.
Does this help, it isn't based on a real tweeter but it shows the potential difference adding the inductor?
Yes thankyou, this is what I would expect, and it is what I am experiencing during listening tests - a reduction of HF output and lack of detail, and wondering if Ivan made a mistake on my particular kit. There's also no reason why L3 should be different between the crossovers as the tweeters are supposed to be closely matched.
I'm unable to find an impedance plot of the CD1.0 at the moment to try and estimate an inductance value, therefore I have been relying on my not so young ears !
I'm unable to find an impedance plot of the CD1.0 at the moment to try and estimate an inductance value, therefore I have been relying on my not so young ears !
Hi Pilot Mariner,
Sorry I'm a bit late to this party, only just stumbled across the thread! May I offer my thoughts to you ....
I also built the fabulous M1TLM kit early last year, and checking my notes seems to reveal a difference between the resistors used in our crossovers. Can't be sure about the inductor values of course as no markings and no details provided in Ivan's build guide that came with them, but the 'stock' resistors for mine had:
R1 = 1.5R
R2 = 2.4R
so, in series as per circuit that's 3.9R
Cap values same as yours.
On the very simple hand-drawn sketch for the crossover circuit (page 2 of Ivan's build guide) it looks like these resistor values had been added in separate to the other component values, as an 'after thought' - by that, I mean it looks like a thicker/darker pen was used to indicate these R values which makes it so obvious they were added in after the sketch, including the other component values, was otherwise completed. Maybe this ties in with the suggestion that Ivan did indeed tweak the crossovers to match the chosen speakers, in this case by 'tweaking' the resistor values slightly?
Or could this disparity be the cause of your lack of treble detail - your R values are simply too high? .....
The guide also suggested that, if I found the treble output too 'low' or too 'high', replacing R1 with 1 ohm (to increase treble) or 2.2 ohm (to decrease) instead of the standard 1.5R would help. As it happens, I did indeed find the treble somewhat overpowering for my taste (a bit on the 'sharp' side for me) so took his advice and replaced R1 with 2.2R and, sure enough, that took the edge off it nicely!
Your series resistance R1 + R2 is 7.2R, whereas after changing R1 to my taste mine is now 4.6R. If you like your treble more distinct, 3.9R might be just the ticket for you - so might be worth reducing the resistor value(s) to somewhere near that? Your series resistance of almost double as shown on my build guide must be stifling the treble no end?
Excuse me if you've already though of this as being maybe being the culprit, which may well be quite possible, in which case you can ignore all of the above!
Hope you get it sorted, as they are certainly exceptional speakers and punch well above their weight.
Sorry I'm a bit late to this party, only just stumbled across the thread! May I offer my thoughts to you ....
I also built the fabulous M1TLM kit early last year, and checking my notes seems to reveal a difference between the resistors used in our crossovers. Can't be sure about the inductor values of course as no markings and no details provided in Ivan's build guide that came with them, but the 'stock' resistors for mine had:
R1 = 1.5R
R2 = 2.4R
so, in series as per circuit that's 3.9R
Cap values same as yours.
On the very simple hand-drawn sketch for the crossover circuit (page 2 of Ivan's build guide) it looks like these resistor values had been added in separate to the other component values, as an 'after thought' - by that, I mean it looks like a thicker/darker pen was used to indicate these R values which makes it so obvious they were added in after the sketch, including the other component values, was otherwise completed. Maybe this ties in with the suggestion that Ivan did indeed tweak the crossovers to match the chosen speakers, in this case by 'tweaking' the resistor values slightly?
Or could this disparity be the cause of your lack of treble detail - your R values are simply too high? .....
The guide also suggested that, if I found the treble output too 'low' or too 'high', replacing R1 with 1 ohm (to increase treble) or 2.2 ohm (to decrease) instead of the standard 1.5R would help. As it happens, I did indeed find the treble somewhat overpowering for my taste (a bit on the 'sharp' side for me) so took his advice and replaced R1 with 2.2R and, sure enough, that took the edge off it nicely!
Your series resistance R1 + R2 is 7.2R, whereas after changing R1 to my taste mine is now 4.6R. If you like your treble more distinct, 3.9R might be just the ticket for you - so might be worth reducing the resistor value(s) to somewhere near that? Your series resistance of almost double as shown on my build guide must be stifling the treble no end?
Excuse me if you've already though of this as being maybe being the culprit, which may well be quite possible, in which case you can ignore all of the above!
Hope you get it sorted, as they are certainly exceptional speakers and punch well above their weight.
I believe you are correct, in my notes Ivan stated that the design was specific to the speakers and that they should be kept for reference. I know he used to specify the tolerance and measurement for the HiVi speakers for matching pairs so the crossovers would be identical.
Your components / values are in this link, as that's the values he sold, and matches with the rest of them.
Inductor gauge is also likely as listed etc.
https://web.archive.org/web/2006022...lacoustics.co.uk/ipl_crossover_components.htm
https://web.archive.org/web/2005082...cs.co.uk/ipl_acoustics_____transmission_l.htm
🙂
Inductor gauge is also likely as listed etc.
https://web.archive.org/web/2006022...lacoustics.co.uk/ipl_crossover_components.htm
https://web.archive.org/web/2005082...cs.co.uk/ipl_acoustics_____transmission_l.htm
🙂
Hi
No matter how much I fiddled with the resistors I just couldn't get them to sound right. which looking at the graph supplied by AllenB all you're doing is moving the hump up or down making them sound very harsh with very low resistance (probably at the hump frequency) and lacking in detail (probably due to attenuation of higher frequencies) to very little HF with the specified resistors in circuit.
In the end I reduced L3 right down to 5uH and left the resistors as they are. The speakers now sound how they should do with those high quality components - nicely balanced with plenty of detail. In future it might be worth removing the inductor and trying a zobel instead, but I assumed Ivan used an inductor for phase compensation as well as the increase in impedance of the CD1.0 with frequency, so I left a bit in there for good measure.
It would be very interesting if you could measure your inductance values.
Hi Will I Aint - I also spoke to Ivan regarding the resistors and he confirmed that they were specifically matched to the drivers. However this does not explain why L3 should be different between the crossovers?
Another unconnected issue with these speakers was that I found the cone excursion of the mid/bass unit fouls the grill cover material even at lowish volumes affecting the sound. You could of course listen with the grill covers removed, but I chose to rebate the hole allowing the driver to sit a bit lower in the cabinet avoiding the problem..
Hi Richbandit thankyou very much for your suggestions
No matter how much I fiddled with the resistors I just couldn't get them to sound right. which looking at the graph supplied by AllenB all you're doing is moving the hump up or down making them sound very harsh with very low resistance (probably at the hump frequency) and lacking in detail (probably due to attenuation of higher frequencies) to very little HF with the specified resistors in circuit.
In the end I reduced L3 right down to 5uH and left the resistors as they are. The speakers now sound how they should do with those high quality components - nicely balanced with plenty of detail. In future it might be worth removing the inductor and trying a zobel instead, but I assumed Ivan used an inductor for phase compensation as well as the increase in impedance of the CD1.0 with frequency, so I left a bit in there for good measure.
It would be very interesting if you could measure your inductance values.
Hi Will I Aint - I also spoke to Ivan regarding the resistors and he confirmed that they were specifically matched to the drivers. However this does not explain why L3 should be different between the crossovers?
Another unconnected issue with these speakers was that I found the cone excursion of the mid/bass unit fouls the grill cover material even at lowish volumes affecting the sound. You could of course listen with the grill covers removed, but I chose to rebate the hole allowing the driver to sit a bit lower in the cabinet avoiding the problem..
It's such as shame that he's not trading anymore as his prices were really competitive.
Hi, I plan to build a pair of these speakers. I wonder if you still have plans for cabinet dimensions,etc.Kind regards.
I was following this thread as I was also trying to gain some info on Ivan’s speaker kits as a noticed last year he had ceased trading. I looked o his website a couple days ago and he is back and trading from 11th June although he will no longer be supplying cabinets. Just thought you ought to know. This news has made me a happy man
Thanks for advising us about that Gavin - great news for the DIY audio fraternity I feel!
As it happens, I'm still enjoying my superb M1tlm's so I can't see me needing to replace them for the foreseeable future (if at all?), but it's comforting to know that Ivan's kits will be available again, just in case ...
As it happens, I'm still enjoying my superb M1tlm's so I can't see me needing to replace them for the foreseeable future (if at all?), but it's comforting to know that Ivan's kits will be available again, just in case ...