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Dunlavy SC IV schematics ?
Dunlavy SC IV schematics ?
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Old 10th June 2021, 01:14 AM   #131
AllenB is offline AllenB  Australia
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Dunlavy SC IV schematics ?
Quote:
Originally Posted by mark100 View Post
Step response to me, seems to be more about marketing and audio techno gibber-gobber,
Perhaps the problem is that the shape one looks for in a step response, and other shapes that look bad, may induce judgements that aren't exactly connected with audibility. Not to mention that it's a great way to show off all the hard work put into phase.
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Old 10th June 2021, 08:34 AM   #132
phase_accurate is offline phase_accurate
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Quote:
Oh, I don't understand your point about mid range garbage going out of a port.
I'd say he means the midrange that can leak out of a reflex port of two-way speakers (or three-way with a high low/mid crossover).

The problem with step-response interpretation is that a perfect or almost perfect step-response is easily recognisable. But the differences between different less-than-perfect step responses are difficult to interpret. Furthermore due to the linear presentation disturbing low-level content like the aforementioned midrange-leaking can be visually hidden in a step-response.

So it is advised to always look at magnitude- and phase- response as well if someone is caring about the step response.

Regards

Charles
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Old 10th June 2021, 12:00 PM   #133
mark100 is offline mark100  United States
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Dunlavy SC IV schematics ?
Thx Charles, Yep, i had the picture right about the mid-range leakage, i just wasn't thinking of smaller 2-way or 3-way speakers, which are less likely to keep drivers in separate box compartments.

Your explanation of the problem with step-response interpretation is well said; and quite better than my rambling reasoning why step has marginal value.

Long live Mag and Phase !!
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Old 10th June 2021, 12:52 PM   #134
mark100 is offline mark100  United States
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Dunlavy SC IV schematics ?
Quote:
Originally Posted by AllenB View Post
Perhaps the problem is that the shape one looks for in a step response, and other shapes that look bad, may induce judgements that aren't exactly connected with audibility. Not to mention that it's a great way to show off all the hard work put into phase.
Yep, great way to show off some hard work! And in the face of less-than-certain audibility.

Especially a great way since first order designs are the only regular xovers that can achieve the classic good looking step response.

If i were Mr Dunlay, i'd want the entire industry to focus on step response, for competitive-measurement reasons alone. Lol

(Not meant to be cynical towards Mr Dunlavy at all, because i do strongly believe in what he was doing with his usage of first order xovers. )
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Old 10th June 2021, 05:05 PM   #135
johnnyk9 is offline johnnyk9  United States
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Quote:
Originally Posted by profiguy View Post
I generally read any Dunlavy thread I come across.

There's a reason why Bob Ludwig used Dunlavy speakers and his mastering work speaks for itself. I've listened to many Dunlavys. For the most part they are accurate sounding speakers in many regards, even if they use low Qms drivers and have very simple, 6dB crossover networks that stress the mid and HF drivers. This scheme obviously requires very well behaved drivers and careful engineering.

I built my own Dunlavy clones back in the late 90s with 2 x M26WR09-08, 2 x P13WH00-08 and D2905-9300 per side. They sounded superb and to this day I still miss how correctly they conveyed every aspect of music, physically, spatially and harmonically. Back when I still lived on the east coast I was lucky enough to listen to Gateway Mastering's big Dunlavys - that had a lasting impression on me. I still have 8 brand new M26WR09-08s sitting in boxes collecting dust. They are amazing drivers.

The step response of a speaker system is very audible toward the lower frequencies (at least to me) and because of that, I prefer large sealed, well damped acoustic suspension bass. Just about every ported speaker I've heard was plagued with some amount of overhang that just didn't gel well, especially when combining it with other LF drivers or subs. The other potentially big issue is midrange garbage coming out of the port. If those vented box phase shifts are in the overlaping filter range of the other driver, getting both to play together properly will be really difficult. The type of box alignment (sealed or vented) obviously makes a big difference too. This is why sealed usually works out better.

Things are less critical in the upper treble area, which is where you can get away with a 2nd order filter. Our ears are however very sensitive in the mids up to the lower treble area in terms of phase response. I think its critical to not have significant phase swings from 300 Hz to 5-6 ish kHz to achieve really accurate imaging, sound stage and balance. I'm not talking about that fake euphonic super tall and wide stuff most people seem to love (that includes speakers with rear/side mounted tweeters... yuck!) I don't see any point in scattering around a bunch of HF in an attempt to get better stereo imaging.

I have purchased 4 Vifa M26wr09-08 over the past couple of year trying to find a match to my
SC-IV’s as one was a re-cone and the specs are so varied it is crazy!
Have you measured any of them?
Just curious as the other 3 in my Dunlavy’s measure almost identically.
Also, all of the P13’s I’ve come across the Fs has risen above 100Hz , even with surround replaced it doesn’t change, so it must be the spider….
Thanks,
Johnny

Last edited by johnnyk9; 10th June 2021 at 05:07 PM.
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Old 10th June 2021, 08:42 PM   #136
profiguy is offline profiguy  United States
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Quote:
Originally Posted by johnnyk9 View Post
I have purchased 4 Vifa M26wr09-08 over the past couple of year trying to find a match to my
SC-IVís as one was a re-cone and the specs are so varied it is crazy!
Have you measured any of them?
Just curious as the other 3 in my Dunlavyís measure almost identically.
Also, all of the P13ís Iíve come across the Fs has risen above 100Hz , even with surround replaced it doesnít change, so it must be the spiderÖ.
Thanks,
Johnny
Hmm, thats interesting about the P13s. I put new surrounds on my last pair I have since they became rock hard, and they're reasonably close to spec.

I'll try to get some measurement data for you on the new M26s I have. I used 2 of them in separate 1.5 cu ft boxes behind the bench seat of my old F250. They sound amazing in that small space and are super efficient. One thing I did notice is they are very sensitive to uneven screw torque on the mounting flange. The VC starts to rub if i don't have those screws tightened very evenly, so i suspect they run a very tight VC gap clearance.
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Old 10th June 2021, 09:03 PM   #137
profiguy is offline profiguy  United States
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Quote:
Originally Posted by mark100 View Post

Oh, I don't understand your point about mid range garbage going out of a port.
Do you mean a sub port?
Yeah, that would be a super bad box design.
Every driver deserves it's own cavity/enclosure...unless like a CD/horn centered in a bigger mid/low horn etc... like what Fulcrum Acoustics does.

Ime, a vented mid in it's own box, can work very well with a vented sub in its own box.
Like said, not sure what you were saying...
I'm referring to woofers crossed over into the mids in ported enclosures, when I talk about midrange wash coming out of the port. Dedicated subs crossed low dont have that issue. Maybe thats why many designers put the port in the rear of the cab? That usually makes speaker placement super critical when it comes to wall distance.

When I talk about phase shifts and crossover issues, I am referring to a ported full range cab being crossed over with a sub. The full range cab will have larger phase fluctuations around its LF rolloff frequency range and that won't combine smoothly with the smoother LP slope of the sub. If the full range cab uses a sealed box, it doesn't have those phase shifts, so it combines and sums more smoothly with the sub. Hope that explains it.
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Old 11th June 2021, 02:26 AM   #138
pwayland is offline pwayland  United States
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Thinking of a remodel of my house. How to incorporate my SC-IVA's in the architectural and sonic space. Allow me to think aloud here and perhaps most of all, I would like to illicit some creative thinking. One idea is to encase the cabinets in reinforced concrete within a wall and the SC-S2's in a similar structure with the cabinets flipped forward facing. The immediate concern that comes to mind is the concrete cabinet interface. next is the accurate engineering of the angles and distances from the listening area, but If I'm going to this length, then investing in testing apparatus would be part of the bill. What about, well serviceability. How does one engineer access panels..... I Also thought of sawing my SC-S2's in half to create stereo subs.
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Old 11th June 2021, 03:26 PM   #139
mark100 is offline mark100  United States
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Dunlavy SC IV schematics ?
Quote:
Originally Posted by profiguy View Post
I'm referring to woofers crossed over into the mids in ported enclosures, when I talk about midrange wash coming out of the port. Dedicated subs crossed low dont have that issue. Maybe thats why many designers put the port in the rear of the cab? That usually makes speaker placement super critical when it comes to wall distance.

When I talk about phase shifts and crossover issues, I am referring to a ported full range cab being crossed over with a sub. The full range cab will have larger phase fluctuations around its LF rolloff frequency range and that won't combine smoothly with the smoother LP slope of the sub. If the full range cab uses a sealed box, it doesn't have those phase shifts, so it combines and sums more smoothly with the sub. Hope that explains it.
Gotcha on both points, thanks for the continued explanations

Whenever i work with IIR xovers, it's for live sound.
Which has a high probability of entailing a vented main speaker on a vented sub. (odds i'm sure you're aware of)

Doing outdoor sub-to-main alignments, per the industry standard tuning technique of getting phase traces to overlay as closely as possible through the xover region.......it's often easy the relative-order problem you describe, from the slopes of the phase traces not quite being able to match.
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Old 12th June 2021, 08:26 PM   #140
profiguy is offline profiguy  United States
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Quote:
Originally Posted by mark100 View Post
Gotcha on both points, thanks for the continued explanations

Whenever i work with IIR xovers, it's for live sound.
Which has a high probability of entailing a vented main speaker on a vented sub. (odds i'm sure you're aware of)

Doing outdoor sub-to-main alignments, per the industry standard tuning technique of getting phase traces to overlay as closely as possible through the xover region.......it's often easy the relative-order problem you describe, from the slopes of the phase traces not quite being able to match.
Yes, pro sound is a completely different situation and most if not all DSP xover is capable of variable and steeper filter slopes to avoid interaction issues. You just time align with very steep filters, so the overlap doesn't really matter so much. Latency is more of a problem and having the least amount of it is critical.
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