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Old 22nd December 2012, 04:37 PM   #1
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Default Featherweight Title Fight

Can anyone figure out what's going on in the Danley CS-30? I can't figure out how they're getting a bandpass-ish response curve along with an impedance curve that almost looks like a sealed box.

Based on some comments from Ivan Beaver, it looks like the CS-30 complements the TH-Mini well, so I thought I'd pit them head-to-head.

(According to Beaver, the CS-30 digs deeper at the cost of low frequency efficiency, but the Mini has higher efficiency *and* higher power handling than the TH-Mini in the octave from 40 to 80hz.)

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zmarchive.com psw-srf: 35103 Mini Subs
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Old 22nd December 2012, 04:51 PM   #2
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Here's the specs.
  • Name : TH-Mini / CS-30
  • Weight : 76lbs / 83lbs
  • Driver : 12" / 12"
  • Dimensions (in) : 24 x 15 x 22.5 / same
  • External Volume (cubic feet) : 4.69 / same
  • Internal Volume (cubic feet, estimated) : 3.5cf / same
  • power handling (watts) : 700 continuous, 1400 program / 400 continuous, 800 program
  • Sensitivity : 101dB / 95dB
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Old 22nd December 2012, 06:32 PM   #3
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Having worked with the TH-mini, I can say that it really doesn't put out below 50. That being said, it hits 128dBspl solid for hours on end. I had one running in-doors for 5 hours, I had to leave for most of it. When I came back there was about 150 people in the room enjoying the music, the amp was clipping and the DJ mixer clipping(digital...sigh) and the smell of hot voice coil was immediately apparent. That was some seriously low crest factor content and the TH-mini kept playing. For my uses the TH-mini doesn't go low enough but for many small live shows, you'd be hard pressed to find and easier to use more reliable speaker.
Patrick...I know what you are thinking...no you can't fit 4 of them in your car...lol =D

The CS-30 seems to fit the same driver physical limitations as the TH-mini. If you double the power to a cs-30 it's spl would match the mini. The difference in response on the higher end I think is due to the port acting like a short circuit. In the low end the port radiation is less than 90deg out of phase from the woofer so you get coupling. This type of response is usually from a slightly over sized enclosure but the internal volume matches an idealized sim of the lab 12. I think they use a version with a 3" vc though.

Perhaps it's possible that that cone has mass added to it, but probably not.
I do know that danley is unique in their rating method as their program power rating is based on the point where THD exceeds a specific level. That may account for the difference in power ratings. I think this is a case of a very similar driver optimized for two very different sub applications.
As for the impedance curve... it looks like the result of port compression but how could that be?

Danley has run both of them crossedover as a dual band sub system and it was pretty flat from just under 30 to above 200 and a VERY nice phase plot with less than 180deg unwrapped shift across that band.

In conclusion...I'm tired and that probably didn't make much sense.

Happy day after the end of the world =)

-Matt
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Old 22nd December 2012, 09:21 PM   #4
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What do u mean? There's a wireframe drawing of the internals. You know the external dimms, and can take a guess on a suitable driver for it. The port wall seems to taper, then flare back up towards the front of the cabinet.
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Old 22nd December 2012, 11:56 PM   #5
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Quote:
Originally Posted by m R g S r View Post
What do u mean? There's a wireframe drawing of the internals. You know the external dimms, and can take a guess on a suitable driver for it. The port wall seems to taper, then flare back up towards the front of the cabinet.
Look at the impedance curve and phase curve. It looks likes a sealed box.

If I had to guess, I'd venture that there are two tunings, causing the expected dip in the impedance curve that's spread out by the multiple tunings.

But that's just an educated guess.
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Old 23rd December 2012, 03:31 PM   #6
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Default vent of the cs 30

It is vented speaker.The vent of the cs 30 has not the same cross section over it's entire lenght. At both ends its aprox the double of in the middle. I think it is something like the vented sub of the hla series of jbl HLA Series
Even Bose used something similar for the vents of their 502b sub.
I think the falling response above 70 Hz is the nature of the used speaker ( a modified lab12 with added mass??).
I have owned 2 TH-mini's and they are tapped horns with a b&c 12" speaker
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Old 23rd December 2012, 04:04 PM   #7
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Quote:
Originally Posted by Patrick Bateman View Post
Look at the impedance curve and phase curve. It looks likes a sealed box.

If I had to guess, I'd venture that there are two tunings, causing the expected dip in the impedance curve that's spread out by the multiple tunings.

But that's just an educated guess.
Looking at the cabinet design, it is obviously a single ported cabinet. The port design has been described in JBL white papers, it reduces turbulence at high port velocity.

As far as the impedance response, it does look odd for a cabinet that is ported.

As you can see in the comparison of a Lab 12 in an oversized (underdamped) box and the CS-30 below, the Lab 12 Fb is higher, but they both have very similar phase and magnitude response above Fb.

Art
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File Type: png WS Lab12, DSL CS-30.png (248.6 KB, 497 views)
File Type: png CS30WireFrame.png (306.2 KB, 495 views)
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Old 23rd December 2012, 06:35 PM   #8
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Quote:
Originally Posted by sonomanie View Post
It is vented speaker.The vent of the cs 30 has not the same cross section over it's entire lenght. At both ends its aprox the double of in the middle. I think it is something like the vented sub of the hla series of jbl HLA Series
Even Bose used something similar for the vents of their 502b sub.
I think the falling response above 70 Hz is the nature of the used speaker ( a modified lab12 with added mass??).
I have owned 2 TH-mini's and they are tapped horns with a b&c 12" speaker
I think I figured it out

Keep in mind, I was completely wrong about how the tapped horn worked when it first came out half a decade ago, so bear with me...

But here's what I think is going on in the CS-30:
  • The CS-30 *is* something like a vented box, but with a twist
  • In a 'typical' vented box, the port is tuned to a frequency that's equal to or below the FS of the driver. For instance, a QB3 box for the LAB12 is 4.1 cubic feet, with an FB and an F3 of 22hz.
  • If you reduce the box size, the vented peak becomes both louder and higher in frequency. You get 'one note bass.'
  • The unusual twist in the CS-30 is that the vent has a reverse taper. My hypothesis is that the reverse taper of the vent makes it a bit resistive, and perhaps reduces the level of the helmholtz peak


As I see it, the coolest thing about the 'invisible bandpass' is that it allows you to use a woofer that's too big for the box. For the last few years I've been building a lot of tapped horns with small woofers, but I've slowly started to realize that there are a lot of advantages to big woofers in small boxes, since maximum output is generally dictated by displacement at low frequencies. (IE, in a horn or tapped horn, the gain is achieved *above* the tuning frequency; so the horn does nothing to improve output below tuning. Therefore, displacement is very important at low frequency.)


I'll post some sims shortly, which will explain my hypothesis better.
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Old 23rd December 2012, 07:14 PM   #9
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Click the image to open in full size.

I took the images available online and 'reverse engineered' the box. This is what I came up with.

The image is a bit small, but the important dimensions are in the port. Here are the details:
  • The end of the port terminates in a slot vent that's 7.62cm tall by 34.29cm wide.
  • The vent narrows to a dimensions that's 3.8cm tall. That segment of the vent is 25.9cm long.
  • The vent then begins to widen as we go towards the lower right corner of the sub. That segment of the vent is 17.27cm long. At the lower right corner of the sub box the vent height is 10.2cm.
  • The final segment of the vent is 10.2cm long. The vent height at the final segment is 12.7cm. Note that the vent turns 90 degrees.
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Old 23rd December 2012, 07:50 PM   #10
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Quote:
Originally Posted by Patrick Bateman View Post
I think I figured it out
[*]In a 'typical' vented box, the port is tuned to a frequency that's equal to or below the FS of the driver. For instance, a QB3 box for the LAB12 is 4.1 cubic feet, with an FB and an F3 of 22hz.[*]If you reduce the box size, the vented peak becomes both louder and higher in frequency. You get 'one note bass.'

I'll post some sims shortly, which will explain my hypothesis better.
I'll be looking forward to your sims:^).

When box size is reduced, and Fb is kept the same, the vented peak reduces.

The Smaart comparison I posted was a single Lab 12 in this dual design:
FREE SUB PLAN: Dual Lab12 (Front Loaded) by Welter Systems
The "too big" box results in nearly the same LF port output, with a falling upper response, very similar to the DSL CS-30.

The single Lab 12 is 5 dB more "sensitive" than the dual in the 40-50 Hz range.

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