I mentioned these (OT) in another thread, and got several questions about my mods, so I figured it would be best to share it in a dedicated thread.
Ref: Vifa C17WH-
I built the (ver 4) some years ago, using QLN spare part C17 drivers. These are not exactly the same as the originals, since they have surrounds from rubber (-foam?). Measurements seemed very similar to what Troels presented, but possibly a little bit lively in the 1-2k area. However, the measurements from Troels seem to differ in this area too. I used the DT300+WG300 from Monacor as prescribed.
I have always been running them sealed by plugging the 'horn loaded BR'. I never liked BR bass. The 'cavity' next to the 'BR horn' is also filled with rockwool, and a layer of normal stuffing on top to keep the dust from the rockwool in place. This improve bass a bit, and was a visible improvement on the impedance trace of the upper woofer.
I was never entirely happy with them though, I ended up running them active for a long time, and even then, I was not too happy with all the EQ available etc. They did sound a better with the XO raised to 2k or above though.
I got tired of the active setup with subs, a lot of amps and cables, and never ending tuning of the system when moving something around. And when I built a JLH amp I relly liked, I figured I would try to 'fix' the sound of these C17's and go back to basic stereo with one amp and two speakers.
I tried several mods on the tweeters, changing the damping in the pole piece, trying with FF (which I removed according to Troels instructions). In the end I liked it a bit more without the rear chamber and no FF.
I have a theory that the relatively high resonance (phase and ringing) of the tweeter is 'magnified' by the big WG enough to disturb the sound. There is also some (subjective) harshness in the treble area that I never got rid of. I was able to improve the dip around 15k significantly while playing around with the stuffing and rear chamber.
I also tried to do some mods to the XO, but wanted to stay 'true to the original' only adjusting tweeter resistor and cap at first. Later I just did my thing based on measurements ans subjective impressions from listening. A little bit higher XO, rising response from bass to mid flattened(maybe because high efficiency was the target of the design), phase tracking improved.
I found this one day Test Peerless DX25TG09-04 (XD-270 F / 4) on the waveguide, and ordered the Peerless DX25tg59-04 tweeters, made the adapters, and adjusted the XO. Now things started to improve in the midrange, and also in the top end. After some time playing with the DX (removing FF among other things), I was still not entirely happy with the treble, so I ordered the xt25bg60-04, and treble improved. I always preferred falling response before, but with these I did not mind flat. The DX might sound a little bit better in the midrange, but overall, I definitely like the XT better.
After some time I wanted to try impedance correction on the woofers. This was a major lift for the bass 'tightness' too, I really liked it.
I attach some pics of the XO's I could easily find, I have to dig more for the rest, if more is requested.
Ref: Vifa C17WH-
I built the (ver 4) some years ago, using QLN spare part C17 drivers. These are not exactly the same as the originals, since they have surrounds from rubber (-foam?). Measurements seemed very similar to what Troels presented, but possibly a little bit lively in the 1-2k area. However, the measurements from Troels seem to differ in this area too. I used the DT300+WG300 from Monacor as prescribed.
I have always been running them sealed by plugging the 'horn loaded BR'. I never liked BR bass. The 'cavity' next to the 'BR horn' is also filled with rockwool, and a layer of normal stuffing on top to keep the dust from the rockwool in place. This improve bass a bit, and was a visible improvement on the impedance trace of the upper woofer.
I was never entirely happy with them though, I ended up running them active for a long time, and even then, I was not too happy with all the EQ available etc. They did sound a better with the XO raised to 2k or above though.
I got tired of the active setup with subs, a lot of amps and cables, and never ending tuning of the system when moving something around. And when I built a JLH amp I relly liked, I figured I would try to 'fix' the sound of these C17's and go back to basic stereo with one amp and two speakers.
I tried several mods on the tweeters, changing the damping in the pole piece, trying with FF (which I removed according to Troels instructions). In the end I liked it a bit more without the rear chamber and no FF.
I have a theory that the relatively high resonance (phase and ringing) of the tweeter is 'magnified' by the big WG enough to disturb the sound. There is also some (subjective) harshness in the treble area that I never got rid of. I was able to improve the dip around 15k significantly while playing around with the stuffing and rear chamber.
I also tried to do some mods to the XO, but wanted to stay 'true to the original' only adjusting tweeter resistor and cap at first. Later I just did my thing based on measurements ans subjective impressions from listening. A little bit higher XO, rising response from bass to mid flattened(maybe because high efficiency was the target of the design), phase tracking improved.
I found this one day Test Peerless DX25TG09-04 (XD-270 F / 4) on the waveguide, and ordered the Peerless DX25tg59-04 tweeters, made the adapters, and adjusted the XO. Now things started to improve in the midrange, and also in the top end. After some time playing with the DX (removing FF among other things), I was still not entirely happy with the treble, so I ordered the xt25bg60-04, and treble improved. I always preferred falling response before, but with these I did not mind flat. The DX might sound a little bit better in the midrange, but overall, I definitely like the XT better.
After some time I wanted to try impedance correction on the woofers. This was a major lift for the bass 'tightness' too, I really liked it.
I attach some pics of the XO's I could easily find, I have to dig more for the rest, if more is requested.
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Soem info aout the XO:
L1 increased for flat response without RC parallel to the woofer
R1+C2 Mild notch to straighten the LP slope
This approach improved phase tracking to the tweeter and woofers FR is almost the same as Troels version
R5+L4+C3 impedance correction for woofers in closed box. Recommended for more transient correct bass, drums sound better.
R2+C1 can be adjusted to taste. This gives flat response with XT and slightly falling with DX without FF.
R3+L2. Simplified impedance correction for tweeter. Tweeter 'sees' a low impedance at resonance. I tried a notch too, but subjectively this sounded better.
The DT300 version is just simple a modification of the filter to adapt it for the DT300. It also includes an impedance correction for the peak at XO frequency L3+C5+R4. It measures good and sounds ok.
L1 increased for flat response without RC parallel to the woofer
R1+C2 Mild notch to straighten the LP slope
This approach improved phase tracking to the tweeter and woofers FR is almost the same as Troels version
R5+L4+C3 impedance correction for woofers in closed box. Recommended for more transient correct bass, drums sound better.
R2+C1 can be adjusted to taste. This gives flat response with XT and slightly falling with DX without FF.
R3+L2. Simplified impedance correction for tweeter. Tweeter 'sees' a low impedance at resonance. I tried a notch too, but subjectively this sounded better.
The DT300 version is just simple a modification of the filter to adapt it for the DT300. It also includes an impedance correction for the peak at XO frequency L3+C5+R4. It measures good and sounds ok.
I had a look, and I have the simulation for the DX without FF, but I think I never simulated the XT. I only dropped it in instead of the DX and measured the speaker to confirm everything was good. No measurement saved though.
I see now that L2 could probably be a little bit larger with the XT tweeters lower resonance (large back chamber).
No cored coils and electrolyte caps only in woofers impedance correction.
I see now that L2 could probably be a little bit larger with the XT tweeters lower resonance (large back chamber).
No cored coils and electrolyte caps only in woofers impedance correction.
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Nice, thanks a lot.
I made a pair of these for my daughter, but "curiosity killed the cat" (read: children pushed the tweeters to death). I have a pair of xt25tg30-04 that may join WG300.
As the sensitivity is lower for tg30 I will adjust for that.
I made a pair of these for my daughter, but "curiosity killed the cat" (read: children pushed the tweeters to death). I have a pair of xt25tg30-04 that may join WG300.
As the sensitivity is lower for tg30 I will adjust for that.
I just love Vifa C17's so this was great reading. Thank you!
A couple of questions if I may?
Do you use the same dimensions on cabinet as Troels Gravesen mk4? And is the series resistance in L4 accounted for in R5?
A couple of questions if I may?
Do you use the same dimensions on cabinet as Troels Gravesen mk4? And is the series resistance in L4 accounted for in R5?
Yes, the V4 cabinet, I do have round-overs on the baffle sides and some extra bracing though.Other than that, they're according to drawings.
R5 is the total resistance, so if you have a higher resistance coil, reduce R5. High tolerances are not needed, drivers will vary too, and so will the stuffing in the box etc. To make it optimal, the impedance of your woofers should be measured in box, and values corrected accordingly. Please note that this compensation only applies for a sealed box. BR will move the upper peak higher in frequency, and create another one at a lower frequency. Totally different compensation values needed in that case.
I can see why you love C17, these make really nice sound in small/medium size rooms. A little bit missing in the low octave, but other than that I really like them. Like a magnifying glass to the music, a lot of details and depth. I hear stuff on these that I don't hear on other speakers, and still they are not tiring to listen too (after mod). They are sensitive on sitting on the sweet spot and how they are placed though.
R5 is the total resistance, so if you have a higher resistance coil, reduce R5. High tolerances are not needed, drivers will vary too, and so will the stuffing in the box etc. To make it optimal, the impedance of your woofers should be measured in box, and values corrected accordingly. Please note that this compensation only applies for a sealed box. BR will move the upper peak higher in frequency, and create another one at a lower frequency. Totally different compensation values needed in that case.
I can see why you love C17, these make really nice sound in small/medium size rooms. A little bit missing in the low octave, but other than that I really like them. Like a magnifying glass to the music, a lot of details and depth. I hear stuff on these that I don't hear on other speakers, and still they are not tiring to listen too (after mod). They are sensitive on sitting on the sweet spot and how they are placed though.
Those are actually M17's. I fitted the midwoofer in the 2.5 arrangement with foam surrounds. I did that on the M21WO-28-08 that I pulled out of an old set of Dali 700 as well. Midrange quality goes up a few notches, so I am a big fan and beliver of foam surround. ��
I've been trying to find new foam surrounds for some C17WG's I have too, but one Dutch company failed to supply ones that fit (they need to be pretty narrow). Suggestions on good surrounds? I might even replace the rubber surrounds on the ones I have in these speakers.
I have been using Speaker Repairshop. They didnt have the exact part for my Vifa M21WO-28-08 , but I used for one of the other M21's. Worked like a charm.
They don't have surrounds that fit the later C17 baskets. I got two different sets, but none of them fit. I would have to cut down the cone to a smaller size to use them. At least they really tried to help, great support!
Yeah, great support from these guys. Bad luck with those C17WG's though.
I see that Troels Gravesen C17 has a sensetivity of around 95db at approx 1000hz, but he is using 1mH coil. Have you measured or simulated sensetivity with your crossover using that bigger coil?
I see that Troels Gravesen C17 has a sensetivity of around 95db at approx 1000hz, but he is using 1mH coil. Have you measured or simulated sensetivity with your crossover using that bigger coil?
No, my measurement gear is not calibrated in any way. It will be a couple of dB lower than the original, since they had a rising response from bass to mid before, and now it's pretty flat.
I checked the simulation now, and using Troels XO with 1mH & 6,8uF+5,6ohm gives abt +2dB at 1kHz compared to this.
Now my wife is going to kill me, but I just picked up another pair speakers he he.
These are Dali 104 with Vifa C17WG 66 08 woofers in MTM configuration. The cabinets were in pretty bad shape but the drivers look very good.
So I think I'm going to build a nice set of cabinets, buy new tweeters and waveguides and use your crossover.
The response on C17WG and WH is almost identical but WG has one or two db less sensetivity.
These are Dali 104 with Vifa C17WG 66 08 woofers in MTM configuration. The cabinets were in pretty bad shape but the drivers look very good.
So I think I'm going to build a nice set of cabinets, buy new tweeters and waveguides and use your crossover.
The response on C17WG and WH is almost identical but WG has one or two db less sensetivity.
I think the bass tuning could be a problem with the WG. Maybe some extra magnets would improve it. I had a pair of 104's too, but the bass tuning was not to my liking, too sloppy even with a stuffed port. It took me some time to realize the drivers had small magnets compared to the WH.
I still have the drivers, but they need new surrounds, and I have not found good replacements.
I still have the drivers, but they need new surrounds, and I have not found good replacements.
Yeah, they are pretty room and amplifier sensetive. You can play a little with box filling and different damping factor amplifiers. It is the WG version Living Voice uses in their new Auditorium R25A. You can read from the review some comments about bass and amplifier matching.
Living Voice Auditorium R25A | The Ear
Living Voice Auditorium R25A | The Ear
