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Design of 2x18 Front Loaded Horn

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levyte357 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2007 at 6:45pm
After chatting to couple of members by PM, might be going for 2x15's instead Ouch.

However finding 15's with lowish Fs, largish Xmax  and right EBP is proving difficult.

Looking at 15TBX100 at the moment.

LARGE 10.0MM XMAX &  A MASSIVE 2,000 WATTS POWER HANDLING!

15 TBX100

 

Item Price: $265.99

SPEAKER MODEL

15 TBX100

SPECIFICATIONS

Nominal Basket Diameter

15" / 320mm

Impedance

8 ohms

RMS Power Rating

1,000 Watts

Program Power Handling 2,000 Watts

Frequency Response

35Hz - 1.5kHz

Sensitivity (1W/1m)

96dB

Voice Coil Diameter

4" / 100mm

Winding Material Copper
Former Material Fiber Glass
Winding Depth 1.0" / 25mm
Magnetic Gap Depth .47" / 12mm
Flux Density 1.1T

Resonant Frequency (fs)

35 Hz
Impedance (Re) 5.1 ohms
Electrical Factor(Qes) .30
Mechanical Q (Qms) 5.2
Total Q (Qts) .28
Compliance Equiv. Vol. (Vas) 113 Liters/3.9cu. ft.
Surface Area of Cone (Sd)m2 0.0855m2
Voice Coil Overhang (Xmax) 10.0mm
Reference Efficiency 1.95%
BL Factor 25.5 T-M
Coil Inductance (Le) 1.6mH




Edited by levyte357 - 02 November 2007 at 7:22pm
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levyte357 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2007 at 7:47pm
Figures for 2x B&C 15TBX100

Drivers arranged side by side, making cab approx 30" wide.Shocked



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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 03 November 2007 at 2:38am
What are the actual design aims of this Lev?

Here's a hint: Try simulating an 18LW1400 in a WSX. Stack of 3. Now for me that has it all.  Flat to close to 40Hz, smooth response,good efficiency,sensible sized cab.

What more do you want?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 03 November 2007 at 2:55am
Originally posted by ceharden ceharden wrote:

What are the actual design aims of this Lev?

Here's a hint: Try simulating an 18LW1400 in a WSX. Stack of 3. Now for me that has it all.  Flat to close to 40Hz, smooth response,good efficiency,sensible sized cab.

What more do you want?



Simulated loads of Drivers in WSX earlier this year.

From sims I have run, V18-1000 is baddest guy in WSX. 18sound is flatter,  but BL lower than V18-1000 and Vas higher, so runs out of Xmax at lower SPL. But thats old news.

I want cab that reaches just below 40hz in singles,  that also approaches scoop/lab sensitivity. Which means 2x drivers on long horn with big mouth. 4x Cabs must be flat to 35hz.Wink



Edited by levyte357 - 04 November 2007 at 11:25am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Disco Stu Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2007 at 9:37pm

http://www.billfitzmaurice.com/T36.html

Tuba 36 wide enough to fit an 18"?
 
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Sensitivity + Power Handling - Power Compression = Max Output

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2007 at 10:15pm
Howcome your looking for such a low Fs? The horn adds mass to the cone anyway.

It looks to me that the only way to achieve your aims is to have a wobbley response like the BF tuba.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2007 at 10:20pm
Originally posted by mobiele eenheid mobiele eenheid wrote:

As the drivers are relatively small compared to the frequencies the reproduces would they not act as a single driver?
 
Wkr Johan

Very good point.
Id explain it more as frequency and wavelength proportions.

JSG mashed did you calculate the delay in output from the 'late' driver and if its audible before reccomending  delaying it?What looks bad on paper needs to be verified.

I think people need to inspect some basics on wavelength,and group delay audibility.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 04 November 2007 at 10:23pm
Originally posted by biotec biotec wrote:

one driver has a longer horn path than the other?
 
That design will be inneficient and peaky as the drivers will be out of phase over some of the response. It's like using two different types of cab.

Nope.The horn is being excited at two different points.I dont think it will be audible below 80hz.But I havent bothered calculating it,Im meant to be studying right nowLOLThere will be two different reflections from the start of the horn that will appear at the mouth at some high frequency probably out of passband.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote jsg mashed Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2007 at 11:08am
Originally posted by tb_mike tb_mike wrote:

Originally posted by mobiele eenheid mobiele eenheid wrote:

As the drivers are relatively small compared to the frequencies the reproduces would they not act as a single driver?
 
Wkr Johan

Very good point.
Id explain it more as frequency and wavelength proportions.

JSG mashed did you calculate the delay in output from the 'late' driver and if its audible before reccomending  delaying it?What looks bad on paper needs to be verified.
If wavefronts from the two drivers arrive out of phase, this will cause amplitude response issues due to cancellation. This is why the original WSX uses a "letterbox" throat section - it reduces path length variations across the cone.
 
You need to remember that if the drivers are run from the same signal, thats 2*18=36 inches of source. Add the reflection from the inside end of the duct and that's effectively 72 inches or 180cm of distributed source. That fits a half wave at just below 100Hz, so sensitivity is already rolling off. There's not much point in using a horn if you only want to go up to 100Hz.
 
Delaying the second driver creates a more concentrated wavefront since output from the first and second driver arrive in phase. There's still the reflection from the second driver - this is why I suggest running the second driver to a lower cutoff - so it contributes where it works well, and not where it doesn't.
 
There's also an impedance angle. Impedance in the context of active systems is confusing, but basically, the second driver will see a greater load impedence because there's already pressure right in front of the cone (fron the first driver) that is in-phase with the second driver's output. This permits greater aucoustic power to be developed for less cone excursion. The loading is similar to the case of 2 drivers close together and run in-phase.
 
I guess there's also another, more perceptual angle to this. Percussive type signals are common in bass (drums, string plucks) and are characterised by high narrow peaks that resemble a band-limited impulse signal.
 
Now, if you run such a signal through an all-pass that fiddles the phasing without changing amplitude content, you will see the the peak is not as high. The same energy is there, but it has been spread around. If you play this signal back, you may find that the phase artifacts are too small to be discerned explicitly. But you may also find that you *can* sense the disappearance of that high instantanious SPL associated with the peak.
 
I think this is down to a combination of non-linearity in the ear and the Haas effect, but your milage may vary.
 


Edited by jsg mashed - 05 November 2007 at 11:30am
...because Good is Dumb.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357 Quote  Post ReplyReply Direct Link To This Post Posted: 05 November 2007 at 2:17pm
Originally posted by tb_mike tb_mike wrote:

Originally posted by biotec biotec wrote:

one driver has a longer horn path than the other?
 
That design will be inneficient and peaky as the drivers will be out of phase over some of the response. It's like using two different types of cab.

Nope.The horn is being excited at two different points.I dont think it will be audible below 80hz.But I havent bothered calculating it,Im meant to be studying right nowLOLThere will be two different reflections from the start of the horn that will appear at the mouth at some high frequency probably out of passband.


I guess we are still looking at the original my preferred 2x18,
well here is an SPL plot, to further spark debate..




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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2007 at 3:16am
Levyte: 170Litres backchamber.If you ported this large rear chamber at say 34hz this may help like old Wbins.But they had cutoffs closer to 60hz.
Ive been to indoor gigs where all they had were a few crusty wbins with ported rear chambers,I was happy enough after half a dozen drinks :)
Personally just build a WSX-like thingand be done with it.

You can see the justification of tom danley,to use low Fs car style lab12s for tiny rear chamber,and maximum horn volume. I think the are 20Litres or so each.

JSG : I simply see it as a delayed source,0.001second behind .I dont think is is audible at 50hz!By high narrow peaks do you mean in the time domain,a peak of energy with a fast decay?

It would be nice if we could get a model going like the hornresp waves function,see it happening.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote mykey Quote  Post ReplyReply Direct Link To This Post Posted: 06 November 2007 at 3:19am
I can't still get me head round this
 
are you still going for a double wsx?
 
WHY?
 
just have 2 wsx, i thought you were designing something new, something different?
 
and a cab of over 36'' wide??? are you OK lev? don't need a lie down?
well you will after carrying it.
 
I'd better go before I start winging againLOL
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