Some days I feel like Bullwinkle J. Moose.
You know, "This time for sure!"
I've been breaking in the second set of my 8" two way project; these using the Eton 8-800 and Accuton C23 tweeter instead of the Focal woofer and MB tweeter of the first set. You do have to bed a speaker in for a while to get to it's final tonality, and fine tuning the relative level of the tweeter (other than basic measurments cofirming the design) would be pretty frustrating.
I don't really know why this is the case; Chas Hansen used to talk about this issue with the Avalon Eclipse and Ascent; they would change their tonal character as they broke in, sometimes getting bright, sometimes getting dull, then just eventually "gelling". Maybe it's the Eton woofers, maybe it the polypropylene caps. I don't know.
Mk II version of M8 with Eton and Accuton components
The one shown above without grille is finished in black; the first set, and the next ones will be "honey" oak.
The Mk II has been fairly successful- I've learned a bit, too- but it's not quite where I want it to be. The Accuton tweeters were a little bit of a disappointment, not measuring as well as their published specs, and requiring more crossover work than expected, as a result. They sound very detailed, and aren't edgy- with the right electronics. However, the matchup between the two, even using the elliptic/cauer network I dreamed up for this project, could be still a little better. It's odd to describe, some things sound really fabulous, where I'm surprised at what I hear on old CD's I'm quite familiar with, but a few times things don't quite sound right, especially if you're standing in front of them. To some extent, this is an unavoidable byproduct of the stands they're on, and issues with being off the vertical axis.
With pecussion, piano, and standup bass, as well as complex synth lines, they're very pleasing. Occasionally on a few female vocals I detect a roughness which I'm likely to attribute to the transistion between the two drivers. The 8-800 has a first cone resonance about 1.6 kHz, so the crossover is quite steep at about 1.25 kHz, and it's a little much for the Accuton tweeter- even with what is effectively an 8th order Linkwitz-Riley network, the blend isn't as good as I would like. Yet, I'm listening to Acoustic Alchemy, just having finished a Jacque Loussier album, and both sound very good.
The Eton woofer has a voicing that works well in the classic "Cardas" positioning, but it will never be mistaken for a "techno" style music woofer on the bottom end- in this alignment, it has a smooth, gradual roll off starting about 75- by gradual, I'm talking about being 4-6 dB down in the low 40's, with output to the mid thirties. Low bass is still there, it's just "polite". On the otherhand, close miked recordings of standup bass, such as Holly Cole, Patricia Barber, and Jacque Loussier, sound totally musical and coherent. No bloat at all; not a "ported" sound; instead, the port reduces the "congestion: compared with a sealed alignment playing near the driver's limits. This is the correct way to use a reflex; not flat anechoically, but overdamped.
So where does the Mk III come in? Well, it's already in "test box" mode. It's got a little something "back to my roots" (the Focal Td120dx2 tweeter)
and something brand new for me, a metal cone woofer. Everyone else is working with them, so I though, perhaps lets take a stab at it. But that brings up a point; in general, most metal cone woofers have an absolutely horrendous upper breakup mode- stab is what they do to the ears, unless you take some specific crossover measures. The most widely used series of this type are probably the SEAS magnesium/aluminum drivers, both the standard and Excel versions. However, the upper break up mode is about 15 dB over the nominal midrange level, requiring considerable care. The construction is first class, including a copper coated phase plugs, and copper rings to reduce inductance modulation and resulting distortion. Cost is also first class.
Revel and some other manufacturers, instead of using cones with modified curvilinear profiles, like SEAS does, have adopted a concave contruction. The Hi-Vi M8a driver follows this path, and seems to have more managable breakup modes than many other types.
The performance I've measured on the first samples I recieved is quite reasonable; the first breakup mode is at about 2.5 kHz, and the level is modest, by metal cone standards.
With a version of the EF-LR8 crossover at 1.5 kHz, in room response (no special positioning, lot's of reflecting stuff near by, unfortunately) shows very good supression of the upper resonance- by over 35 dB.
The predicted bottom end extension is a bit better, looking at a Unibox analysis with the measured T/S parameters, with a predicted F3 of 30 Hz.
Of course, the final matter is how will it sound- give me a week or two, and I'll report back. Computer predictions are only good for so much.
"This time for sure!"
Regards,
Jon
Earth First!
_______________________________
We'll screw up the other planets later....
You know, "This time for sure!"
I've been breaking in the second set of my 8" two way project; these using the Eton 8-800 and Accuton C23 tweeter instead of the Focal woofer and MB tweeter of the first set. You do have to bed a speaker in for a while to get to it's final tonality, and fine tuning the relative level of the tweeter (other than basic measurments cofirming the design) would be pretty frustrating.
I don't really know why this is the case; Chas Hansen used to talk about this issue with the Avalon Eclipse and Ascent; they would change their tonal character as they broke in, sometimes getting bright, sometimes getting dull, then just eventually "gelling". Maybe it's the Eton woofers, maybe it the polypropylene caps. I don't know.
Mk II version of M8 with Eton and Accuton components
The one shown above without grille is finished in black; the first set, and the next ones will be "honey" oak.
The Mk II has been fairly successful- I've learned a bit, too- but it's not quite where I want it to be. The Accuton tweeters were a little bit of a disappointment, not measuring as well as their published specs, and requiring more crossover work than expected, as a result. They sound very detailed, and aren't edgy- with the right electronics. However, the matchup between the two, even using the elliptic/cauer network I dreamed up for this project, could be still a little better. It's odd to describe, some things sound really fabulous, where I'm surprised at what I hear on old CD's I'm quite familiar with, but a few times things don't quite sound right, especially if you're standing in front of them. To some extent, this is an unavoidable byproduct of the stands they're on, and issues with being off the vertical axis.
With pecussion, piano, and standup bass, as well as complex synth lines, they're very pleasing. Occasionally on a few female vocals I detect a roughness which I'm likely to attribute to the transistion between the two drivers. The 8-800 has a first cone resonance about 1.6 kHz, so the crossover is quite steep at about 1.25 kHz, and it's a little much for the Accuton tweeter- even with what is effectively an 8th order Linkwitz-Riley network, the blend isn't as good as I would like. Yet, I'm listening to Acoustic Alchemy, just having finished a Jacque Loussier album, and both sound very good.
The Eton woofer has a voicing that works well in the classic "Cardas" positioning, but it will never be mistaken for a "techno" style music woofer on the bottom end- in this alignment, it has a smooth, gradual roll off starting about 75- by gradual, I'm talking about being 4-6 dB down in the low 40's, with output to the mid thirties. Low bass is still there, it's just "polite". On the otherhand, close miked recordings of standup bass, such as Holly Cole, Patricia Barber, and Jacque Loussier, sound totally musical and coherent. No bloat at all; not a "ported" sound; instead, the port reduces the "congestion: compared with a sealed alignment playing near the driver's limits. This is the correct way to use a reflex; not flat anechoically, but overdamped.
So where does the Mk III come in? Well, it's already in "test box" mode. It's got a little something "back to my roots" (the Focal Td120dx2 tweeter)
and something brand new for me, a metal cone woofer. Everyone else is working with them, so I though, perhaps lets take a stab at it. But that brings up a point; in general, most metal cone woofers have an absolutely horrendous upper breakup mode- stab is what they do to the ears, unless you take some specific crossover measures. The most widely used series of this type are probably the SEAS magnesium/aluminum drivers, both the standard and Excel versions. However, the upper break up mode is about 15 dB over the nominal midrange level, requiring considerable care. The construction is first class, including a copper coated phase plugs, and copper rings to reduce inductance modulation and resulting distortion. Cost is also first class.
Revel and some other manufacturers, instead of using cones with modified curvilinear profiles, like SEAS does, have adopted a concave contruction. The Hi-Vi M8a driver follows this path, and seems to have more managable breakup modes than many other types.
The performance I've measured on the first samples I recieved is quite reasonable; the first breakup mode is at about 2.5 kHz, and the level is modest, by metal cone standards.
With a version of the EF-LR8 crossover at 1.5 kHz, in room response (no special positioning, lot's of reflecting stuff near by, unfortunately) shows very good supression of the upper resonance- by over 35 dB.
The predicted bottom end extension is a bit better, looking at a Unibox analysis with the measured T/S parameters, with a predicted F3 of 30 Hz.
Of course, the final matter is how will it sound- give me a week or two, and I'll report back. Computer predictions are only good for so much.
"This time for sure!"
Regards,
Jon
Earth First!
_______________________________
We'll screw up the other planets later....
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