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Old 21st May 2014, 01:23 AM   #1
zobsky is offline zobsky  India
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Default Midrange K-tube ?

I have a pair of midrange paging drivers that will allegedly do 100 Hz on the low end (yeah, right).
1 3/8 X 18 Thread 40W Rms Midrange Driver Threaded | 54-050 (54050) | Distributed By MCM

Pondering if there's any potential used as a midrange K-tube with some PVC tube stuck on the end.
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Old 21st May 2014, 05:42 AM   #2
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you may get a surprise and find they can play that low the question will be how loud? they can't push a lot of air given the diaphragm size. I have found that a 1/4 wave line is all you need. Pick either the given Fs or look at the peak on the impedance graph if one is available. I like to use the double cutaway K-Tube which looks rather like a bishop's hat see the one on the left side. Best regards Moray James.
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Old 21st May 2014, 08:15 AM   #3
CLS is offline CLS  Taiwan
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Hi,

Is there any audible difference between single cut tube and the bishop's hat?

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Old 21st May 2014, 10:06 AM   #4
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by zobsky View Post
I have a pair of midrange paging drivers that will allegedly do 100 Hz on the low end (yeah, right).
1 3/8 X 18 Thread 40W Rms Midrange Driver Threaded | 54-050 (54050) | Distributed By MCM

Pondering if there's any potential used as a midrange K-tube with some PVC tube stuck on the end.
That is a really interesting driver - how does it sound and does it really reach 100 Hz? You can so a quick and dirty test with just stiff card stock.
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Old 21st May 2014, 12:30 PM   #5
IG81 is offline IG81  Canada
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Is that a copy of the Atlas Sound driver purported to be "just like" a WE555?

Assuming a fairly standard profile, that is, a single half-elliptical cut in the tube, the effective length is roughly 90% that of the slotted length. An initial un-slotted section changes things, but I have not studied that much myself. I base this upon my measurement of BMS 4550 on a Transylvania Power Company "The Tube". It is 5.3" long and slotted on its full length. Versus the "naked" driver, i.e. no horn/wg, there is a reduction of distortion starting at 700Hz. This suggests the need for a 37" or so tube to work down to 100Hz. The proportions will then be much different from my tube that my assumptions might not hold up though.

The Faerber Equilibrium speaker uses a super-long unslotted section, I'd sure like to see raw SPL and impedance measurements for that one. Freddi experimented with something similar.
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Old 21st May 2014, 12:44 PM   #6
zobsky is offline zobsky  India
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Most MCM drivers are clones of something else
I can't comment on the sound since I just listened to test tones when I bought them a while back and forgot about them till I had the k-tube idea.
I guess I'll try and run some tests and report back by this weekend .
Thanks
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Old 21st May 2014, 12:55 PM   #7
IG81 is offline IG81  Canada
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Lucky for you a K-Tube is pretty much the cheapest, easiest and fastest type of DIY horn/WG to prototype. Though schedule 40 pipe would be best, a thin-walled tube will be easier to experiment on initially. Let us know how that works out.
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Old 21st May 2014, 02:21 PM   #8
GM is offline GM  United States
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Quote:
Originally Posted by IG81 View Post
Is that a copy of the Atlas Sound driver purported to be "just like" a WE555?
Seems more like a WE 722 PA driver used from 500-6500 Hz.

GM
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Old 21st May 2014, 02:31 PM   #9
IG81 is offline IG81  Canada
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Quote:
Originally Posted by GM View Post
Seems more like a WE 722 PA driver used from 500-6500 Hz.

GM
Quite possible - I'm not all that versed in WE stuff, but remember reading something to that effect some time back. I think the diaphragm and/or phase plug design was supposed to be almost unchanged.

GM, how would you analyze the following K-Tube measurement? This is the Transylvania 1" tube, 5.3" long, fully-slotted, on a BMS 4550 1" driver. Mic was "nearfield", which probably means a few inches away IIRC.

Blue Trace - "naked" driver and its distortion
Red Trace - loaded with The tube and its distortion

Click the image to open in full size.

We can see distortion is reduced above 700Hz, up to ~1600Hz. Output is stronger below 1600Hz down to driver cutoff. The 2kHz dip and distortion peak may be throat mismatch/reflection? Response is often smoothed-out by the K-Tube in the upper registers.

Here is Emilar EC-175:

Blue Trace - "naked"
Red Trace - loaded with The Tube

Click the image to open in full size.

For some reason, the 2kHz dip is worse on the Emilar. I suspect its exit angle to be greater the that of the BMS, which is 14. The BMS does not exhibit as strong a dip in the far-field, but the Emilar still does.

Last edited by IG81; 21st May 2014 at 02:45 PM.
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Old 21st May 2014, 02:34 PM   #10
GM is offline GM  United States
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Originally Posted by moray james View Post
........the question will be how loud?
This is the crux of the matter and since a 1" tube is 'done' at around 4316 Hz, it realistically will be 'done' ~3 octaves away or ~540 Hz, so figure only usable from ~1080 Hz, just as its response indicates. Increasing the tube's diameter to 2" will help down low at the expense of the HF output, but now power handling has been severely compromised without increasing the driver's Fs.

No actual experience with loading any kind of tubes with compression drivers though, so curious how this pans out.

GM
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