Help - Low frequency horn – T18 |
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LORDSANSUI
Registered User Joined: 28 September 2016 Status: Offline Points: 12 |
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Posted: 28 September 2016 at 12:41am |
I’m new on the forum but I’ve being working
hard to understand this fascinating audio work.
I’m talking about Horn because the decision was
already made for my PA but I’m asking for help regarding what drive should I choose
my cabinet. The target is: Lower frequency as possible with
higher SPL considering the model available on the list at the final of the
post. Taking into account three very knew and well successful Low frequency horn designs
Doing reverse engineering comparing all those
drivers the main Thiele/Small parameters they have in common are: High VAS (> 440 L) and also high CMS once
those two parameters are direct correlated. Vas represents the volume of air
that when compressed to one cubic meter exerts the same force as the compliance
(Cms) of the suspension in a particular speaker. Why high VAS is desirable? What is the negative
effect of using low VAS on Low-frequency Horn?
Low QTS (< 2,9) A unitless measurement,
characterizing the combined electric and mechanical damping of the driver. In
electronics, Q is the inverse of the damping ratio.
The value of Qts is
proportional to the energy stored, divided by the energy dissipated, and is
defined at resonance (Fs). No doubt about QTS High BL This is a measurement of the motor
strength of a speaker. Think of this as how good a weightlifter the transducer
is. A high BL figure indicates a very strong transducer that moves the cone
with authority! No doubt about BL Low Xmax (< 6mm) Short for Maximum Linear Excursion.
Speaker output becomes non-linear when the voice coil begins to leave the
magnetic gap. Although suspensions can create non-linearity in output, the
point at which the number of turns in the gap (see BL) begins to decrease is
when distortion starts to increase Low Vd (< 0,725 L) This parameter is the Peak Diaphragm
Displacement Volume — in other words the volume of air the cone will move. It
is calculated by multiplying Xmax (Voice Coil Overhang of the driver) by Sd
(Surface area of the cone).
Here I see the first controversial parameter for Horn once usually high Xmax is desired for low frequencies cabinets and also high Vd, but looks like for Horn those variables are desired low to reduce throat pressure and as consequence reduce the distortion. Could someone confirm or explain? My cabinet is a close of Electro Voice T18 but is not possible to buy the original T18’s drive DL18MT and change the design is not an option, so I’m looking for local driver to install on this cabinet and see what is the best tradeoff it can reach regarding low frequencies and SPL. I’ve being also trying to study deeply the
theory behind the Horn design but without time and experience with this product
have been very hard to proper understand the things. Some references I tried: Low-frequency horn design using Thiele/Small
driver parameters (1977) è By D.B. Keele Jr On the Specification of Moving-Coil Driver for
Low-Frequency Hon-Loaded Loudspeakers (1979) è By W. Marshall Leach Jr I also tried to simulate the T18 cabinet using Hornresp
but the result is a little different from the original curve and maybe due to
some simplifications, losses or wrong input data. The throat was cute in sections like indicated
below. Edited by LORDSANSUI - 28 September 2016 at 1:46am |
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LORDSANSUI
Registered User Joined: 28 September 2016 Status: Offline Points: 12 |
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Hornresp input data
The result from Hornresp @ 1W right?: Original Electro Voice response (Lower SPL @ 60
Hz and higher peak @ 150 Hz: The question I’m trying to answer is: What
would be the best and the worst drive option on the list bellow? why? Once I
will not use T18 original drive what can I expected to loose and what can I
expected to gain?
Note.: Unfortunately also JBL 2240 and Eminence
Sigma Pro 18A2 are not available at my market. Thanks in advanced. Edited by LORDSANSUI - 28 September 2016 at 1:49am |
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Junior253
Registered User Joined: 08 September 2015 Status: Offline Points: 46 |
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i think it simulate on TH bassbin.it right
and sims at 2pi |
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LORDSANSUI
Registered User Joined: 28 September 2016 Status: Offline Points: 12 |
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some guys from other forum found two wrong input data ans requested to change it. they are: The steradians from 4pi to 2pi The segments from conical to parabolic The driver arrangement from ND to TH Here are the results
Link for larger image:
https://s16.postimg.org/3ou8k1g85/Hornres_all_spl.png - https://s16.postimg.org/3ou8k1g85/Hornres_all_spl.png
Link for larger image:
https://s16.postimg.org/k1h1v8mxh/Hornres_all_spl_40_110.png - https://s16.postimg.org/k1h1v8mxh/Hornres_all_spl_40_110.png
Link for large image:
https://s11.postimg.org/bk2s19u4z/Hornres_all_spl_40_80.png - https://s11.postimg.org/bk2s19u4z/Hornres_all_spl_40_80.png
Taking into account the SPL mean from two
different badwidth the simulations highlight some good drivers presenting
better results them the original one.
They are (the list represent just simulation
order and not rank)
Snake ESX185 JBL 18SW1 Snake HPX2180 SPL 18SG12 SPL 18SG16 Oversound 18-800-ST Oversound SUB-1000
The Snake HPX2180 would be the winner and the
Oversound SUB-1000 as the 2nd place them the Snake ESX185 as 3rd.
https://s15.postimg.org/5yu915yrf/Hornres_best_cases_SPL.png - https://s15.postimg.org/5yu915yrf/Hornres_best_cases_SPL.png
The doubt is just about the simulation errors,
i mean the result is a little different from the original SPL curse in terms of
shape. |
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