Well, not necessarily. The electrical response involves the driver impedance and the two are inseperable (using resistors doesn't show anything meaningful but could be used for comparison.
Right, a rising impedance on the low end of the midrange would cause the acoustic rolloff to be more, also there could be phase shift issues between the woofers causing (a problem) and more of an acoustic rolloff then what the electrical curve suggests.
I agree that the drivers impedance is critical for an accurate electrical response. but I figured a resistor would be better than no load at all. and while not a 100% accurate graph, I figured it would be interesting to look at and would offer me at least some way of comparing the new board/parts to the old board.
Zc
well, that's just silly. of course it shows something "meaningful", it just doesn't show what the xover does with the reactive real-world load, it does show the basic filter response.
_-_-bear
It's a good thing to have a repeatable way of comparing the old and new crossover, even if this is it.
A reactive load can give a result quite different and even opposite to what was expected. Go no further than the example of using a capacitor to roll off a woofer. The response can increase beyond the original around the woofer's resonance. Even if you pre-converted the woofer's impedance to a frequency dependent resistance by zeroing ZW< you wouldn't see this.
Since the most relevant parts of a rolloff in a crossover usually involve filter 'knees' and sometimes bumpy responses, the damping and other subtle effects make up the effective rolloff.
A reactive load can give a result quite different and even opposite to what was expected. Go no further than the example of using a capacitor to roll off a woofer. The response can increase beyond the original around the woofer's resonance. Even if you pre-converted the woofer's impedance to a frequency dependent resistance by zeroing ZW< you wouldn't see this.
Since the most relevant parts of a rolloff in a crossover usually involve filter 'knees' and sometimes bumpy responses, the damping and other subtle effects make up the effective rolloff.
I have the stock crossovers back together and I could connect the analyzer to the crossover and take a look at the real world electrical response with the drivers connected. it might be interesting to see what effect the impedance of the drivers plays on the electrical response of the filter network!
Great Dunlavy interview..Loudspeaker designer John Dunlavy: By the Numbers... | Stereophile.com
Dunlavy SC-1 measurements.. Dunlavy Audio Labs SC-I loudspeaker Measurements | Stereophile.com
Notice the inexpensive vifa tweeter's response at 1.2 khz. Ouch! I owned these, and both tweeters blew..
Dunlavy SC-1 measurements.. Dunlavy Audio Labs SC-I loudspeaker Measurements | Stereophile.com
Notice the inexpensive vifa tweeter's response at 1.2 khz. Ouch! I owned these, and both tweeters blew..
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I suggest the following in your crossover upgrade:
1) I'd leave all coil "as it is", but maybe leave the place on new board if you decide in future to use foil coils.
2) L2 and L5 coils are used in networks for correction of freq.response, so their exact values is important (both - inductance and resistance)
3) C15 and C3 exact value is required as in (2) - but both of them making 1.504uF, so you can replace it with one 1.5uF capacitor
4) C7 and C10 also makes 1.504uF, so you can replace it with one 1.5uF capacitor
5) C6, C8, C9: replace them to 8.2+6.8+1uF
6) C4: 50uF - this should be exact value as stated in (2). For example 47+1.5+1.5
7) C1,C13,C14: 24.5uF -> 22+22+0.47 (or 20+20+2.2+2.2)
8) C2, C11, C12: I'd leave it as it is 20+10+10
9) C5, C16, C17, C18: 70uF -> 33+27+10
10) all resistors -> MOX 10W
What kind of parts to use:
If price no object, I'd use best possible caps for (5), (6) and (7) - I suggest you to try there Auricap XO.
for C3, C4, C15 quality is not so important, you can use something like Mundorf MCap250.
For (4): you can use Auricap XO, or also try inexpensive Electrolytics like Mundorf BG ("plain" - new name ECAP70)- you need to listen what is better. Not always expensive cap is better.
For Bass section I suggest MCap400, but MCap250 also will be fine and You can try here also Electrolytics - as what I've noticed that in some constructions replasing electrolytics to plypropilene in bass can make it more exact, but a bit "dry". Here you need to try and listen.
well things are on hold. I have all new inductors and MOX resistors and got hung up on capacitors.
I was extended and offer from someone in the high end cap industry for some special caps and thats what started this whole project in motion and well you know...sometimes people say things just to make themselves look better and when you call them up to collect...they turn around and say "oh, i guess you were serious about that??" and the deal vaporizes!
So things are on hold until I can get an alternate affordable solution worked out...
In the meantime. the refoamed woofers work great. and I have been enjoying them as is with various amps, my Zen Lights mainly, various soundcraftsmens, my Atma Prototype, Audio Research VS60, my old HK 330C, even a little Dayton sonic t-amp!
I was extended and offer from someone in the high end cap industry for some special caps and thats what started this whole project in motion and well you know...sometimes people say things just to make themselves look better and when you call them up to collect...they turn around and say "oh, i guess you were serious about that??" and the deal vaporizes!
So things are on hold until I can get an alternate affordable solution worked out...
In the meantime. the refoamed woofers work great. and I have been enjoying them as is with various amps, my Zen Lights mainly, various soundcraftsmens, my Atma Prototype, Audio Research VS60, my old HK 330C, even a little Dayton sonic t-amp!
I own 7 SC-V(along with two of his TSW-V tower subs), and compressed and soft are not words I would use to describe the sound of this speaker. I have the Bryston 28B SST2 monoblocks in front of each speaker, and dynamics I assure you are not an issue here.
All of the dunlavy speakers are basically an SC-1 with progressively larger woofers in each model. They all used the same inexpensive Vifa mids and tweets crossed over at the same point. That's why I showed the SC-1 measurements. So you can see how they all operate at that particular crossover point. An inexpensive tweeter ($28) http://www.parts-express.com/pdf/264-1022s.pdf that is only down 6db at 1.2 khz is going to distort and compress no matter how big the woofers are. Also, as Zaph stated, the Vifa 5.25" mineral filled polypropylene mids http://www.parts-express.com/pdf/297-302.pdf (Used in almost all Dunlavy models) "Are not low distortion drivers". They were used because of the very smooth, predictable rolloff characteristic..
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You are incorrect here. The SC-1 has two mid/bass drivers, and a single tweeter. The SC-V has 2 12" bass drivers, 2 6.5" mid-bass drivers, 2 3" mids, and a single 1" tweeter. So it is not just progressively larger woofers that define the difference in his line of speakers, it was the additional of more(larger) drivers that cover smaller frequency ranges. This is important detail.
Unfortunately for your case, the SC-1 and the SC-V do not measure the exactly the same. As a matter of fact, the SC-1 and the SC-IV don't measure the same either. Secondly, my SC-V are the last ones he made, and he came back to my studio three times(at my expense) to change the crossovers and tweak the sound of the speakers. After these trips, the speaker sounded a lot better than they did when they first got to my studio.
Before purchasing my SC-V, I took a trip to DAL to give all of his SC line a listen. I watched as John measured quite a few drivers, and it was clear by the measurements why he picked the drivers he did. Based on that experience I learned that it is not how much the driver costs, but how they perform once they are loaded into the box. It is also noted that he updated the mids and tweeter later on, I can attest to that with my own set of speakers. He did that with the crossover as well, I can also attest to that.
I read the reviews of both the SC-1 and SC-IV. Neither review or its accompany measurements points to any distortion or compression from these drivers at their operating frequencies. As a matter of fact, at least on the SC-IV, its huge dynamics were mentioned in the review.
Just an excerpt from the SC-IVA review:
The SC-IV/A hasn't completely avoided sounding like a speaker, but, compared to the SC-IV—itself already low in speaker colorations—it sounds more like musical instruments and voices and less like an electromechanical contrivance.
The SC-IV/A's sound had tremendous coherence: despite being a complex multiple-driver system, it speaks with one voice. There is exceptional top-to-bottom integration, with no audible cues as to where in the range the different drivers take over. One visiting audiophile friend who was unfamiliar with the speakers said that if I hadn't taken off the grille to show him the drivers, he would have thought he was listening to a speaker with a single driver.
If there was any distortion like you mentioned, this would not be possible.
Becareful with foil inductors , completly different sonics due to there stable bandwidth linerarity. It's not as simple as swapping out value for value or matching Dcr , the voicing will be very different .....
I don't know what tweeter he finally settled on(never opened up the speaker), but I know it was different from the one first installed. So was the crossover once he finished tweaking.
One thing I love about John(and probably one of his biggest weaknesses as a businessman) was his almost compulsive nature at small detail in engineering, and in voicing his speakers. When he found an improvement to something, he would always come back to my studio and install and tweak it. As I said earlier, he came back to my studio four times before walking away from my SC-V - and then eventually getting too sick to return for good. When he told be that each SC-V spent 30hrs in the anechoic chamber, and being listened to and tweak, I was blow away. Makes it worth my investment to know this.
I only went with foil for the woofers. that is subject to change however. for now they are on hold.
Dave
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