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Guide to WinISD Pro and Hornresp

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Young Croc
Young Croc


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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 24 February 2005 at 7:42am

- Your add could be here -

(reserved for updates) 
 
Update:
 
Ones every while people experience problems uploading new drivers to WinISD Pro. The main issue is that WinISD Pro standardly calculates the unknown T/S-parameters from the ones given. As soon as your input doesn't correspond with the mathematical coherence between the T/S-parameters a driver will not load.
 
The easiest way around this is go to the bottom of the "Driver Editor" and click-off the "Auto Calculate Unknowns".  An other way around is to only load those T/S-parameters that do not mathematically correspond to other T/S-parameters: The input sequence should be:
 
Qes, Qms, Fs, Vas, Re, Le, Sd, Xmax, Pe (leave the rest open).
 
Best regards Johan


Edited by mobiele eenheid - 12 March 2010 at 4:17am
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Young Croc
Young Croc


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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2005 at 12:31pm

Groupdelay

 

On this page the groupdelay (in miliseconds) is shown in relation to the frequency (Hz). A high groupdelay will result in a boomy/muddy sound. The groupdelay is created by the basreflexport and is thus one of the downsides of using basreflex cabs.

Most people however are used to this sound since basrelfex is used widespread in daily live.

Not only the highed of the groupdelay is to be considerd. The shape is also important. It's better to have a slowly forming round peak then a sudden needle-like peak that's there for just a few frequencies..Generally the groupdelay will reach it's maximum around the tuning frequency

 
A rule of thumb coming from Hifi is: frequency x groupdelay = 400 (max). Less being preferable. At 40 Hz that would be 10 miliseconds. A little bit higher (up to 600) around the tuning frequency can be overcome.

From this rule of thumb you can clearly see that the highed of the groupdelay becomes more important at higher frequencies and less important at lower frequencies. This is because the sensitivity of your ears increases as the frequency rises.

A high groupdelay in the 80 Hz and up area for instance will ruine the "kick'. Making it sloppy having less impact. Making the volume bigger or tuning the port lower, will increase the groupdelay. As you lower the tuning frequency the groupdelay will shift down along side with it.

 

You could lower the tuning frequency that much that the tuning will be beneath the lowcut (aka highpass) your using. The downside to this is that the output of the port will be lost as well.



Edited by mobiele eenheid - 06 July 2009 at 11:15am
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2005 at 12:29pm

Rear port- Air velocity

 

On this page the airspeed in the basreflex port(s) is showed. Either in m/sec. or ft/sec. For Hifi-applications 17 m/sec. (or 56.7 ft/sec.) is an useful limit. For PA-applications 34 m/sec. (or 113.3 ft/sec.) is more useful.

If the airspeed in the port(s) is to high it becomes hear-able, even at SPLmax. It's also called "Port noise".

 

A round port has a slight advantage over square or rectangular ports. By rounding of the corners with a router the port noise can also be reduced just a bit more.

The rounded corner is still part of the length of the port. Sometimes a flair is used.  Making the surface of the ports larger or using more ports, reduces the airspeed in the port but the length will increase.

A port that's to long won't work correct either, this also depends again on the diameter/surface of the port.

 

A rule of thumb is that the port surface has to be at least 1/9th of the surface of the cone.

The more power the speaker will get, the higher the air velocity in the port will become. That's why the air velocity in the port will often look to be nothing at all, since the Power on the "Signal-page" is standard 1,0 Watts.

By raising the power, you'll also raise the air velocity in the port. Off course you should use the amount of power in the simulation that you'll use in practice or the amount of power that the speaker can handle.

The lower the frequency the higher the air velocity get's (up to a certain point).

I've found the limit of 34 m/sec (113.3 ft/sec) to be rather correct. Therefore personally I prefer 30 m/sec. (100 ft/sec.) as the upper limit for PA-applications.

With 6th order bandpass designs there is also a front port. For this port the same rules apply as written above.



Edited by mobiele eenheid - 06 July 2009 at 11:12am
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 07 February 2005 at 12:28pm

Cone excursion

 

Directly related to the maximum power and powerdip is the cone excursion. In this graph the movement of the speaker (in mm) is shown in respect to the frequency.

In the case of WinISD Pro a6 it's the Xmax p-p (peak to peak). This is somewhat confusing because the maximum allowed excursion is now 2 times the Xmax (or Xmax p-p = Xmax times two).

On the "Signal" page, under "Power", you can type the amount of power that you would like to give to the speaker. Now you can see how much excursion the speaker will have, with respect to the frequency.

 

Give the cab a volume of 400 ltr and tune it to 40 Hz with 700 Watts of power going to it.

Around 49 Hz the excursion is now about 19 mm/ 0.75 inch. Xmax times 2 (=Xmax p-p) is 18 mm/ 0.71 inch. So the speaker will exceed Xmax but only around this frequency.

If you would use an equalizer to lower that frequency-band enough than the Xmax would no longer be exceeded. This is off course not very practical, especially because a lot of "energy"  is housed at that area..

 

When a speaker exceeds the Xmax it will loose control over the movement of the cone. Instead of moving only back and forward the cone will also start to move sidewards. In basreflex cabs this is usually noticeable because the quality of the sound is being reduced.

If the cone exceeds Xmax too far it will hit the pole-piece and thus starts to destroy itself. In that case the speaker exceeds the Xmech. Xmech is usually around 2 times Xmax (guitarspeakers generally have a Xmech several times larger than Xmax). And some speakers like the Ciare 12.00 SW have a Xmech quite close to Xmax.

Not every speaker will loose control at the same rate. The 18LW1400 for instance won't loose control quickly when it's exceeding the actual 5 mm/ 0,2 inch. Also Xmech is 25 mm/ 1 inch.

 

Using basreflex cabs both hearing and eyesight are useful tools to "see"  if Xmax is exceeded. Exceeding Xmech the speaker will produce a ticking sound which you will hopefully never hear.



Edited by mobiele eenheid - 06 July 2009 at 11:08am
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2005 at 8:18pm

Maximum Power Chart (aka Powerdip)

In the "Maximum Power" window is showed how much power the speaker can handle without exceeding the Xmax. A graph with on the Y-Axis the maximum power and on the X-Axis the frequency.

To make it easily understandable it's best to simulate a basreflex cab (br-cab) with the 18LW1400. With a volume of 200 ltrs and tuned to 40 Hz. If you look at the maximum power you'll see a straight line (with a value of 700 watt). Below 34,5 Hz the maximum power drops down fast. This indicates it's best to use a low-cut at 34,5 Hz.

Next simulate the cab with a volume of 400 ltrs, still tuned to 40 Hz. Now there is a small dip created in the straight line. This is the so called powerdip. Around 49 Hz the maximum power is only 615 Watts.

The bigger you make the cab or the lower you tune it, the bigger the powerdip will be. The smaller the volume or the higher the tuning the smaller the powerdip will be.

This simulation uses a sine-wave to do the maximum power calculation's, music however isn't a sine-wave. The dynamic range of a sine-wave is 3 dB. Low frequencies mostly have a dynamic range of about 3-6 dB. Meaning that in some cases (6 dB) you can double the amount of power as showed by the simulation, depending on the style of music/sound. Mid and high frequencies will usually have an even bigger dynamic range into the signal (say 9 -12 dB).

It's still best tho if a speaker doesn't has a powerdip (unless off course the powerdip is out of the represented frequency range). With most subs/woofers the powerdip is somewhere around the 40 á 60 Hz area. Those frequencies are of great importance to most types off music. Also a speaker will frequently be used at a higher power than the rated rms-powerhandling.

By raising the powerhandling you can see where the powerdip is, in case it's not visible at maximum power (parameters, double click on the Pe-number and type the new {higher} number, changes will not be stored).

With some cabs/loudspeakers the lower powerhandling created by the powerdip will be significantly lower than the rated powerhandling. Some speakers show this lowered powerhandling even on a very "friendly tuning". In most cases the lack of Xmax is to blame. Sometimes it just shows the speaker not being intended for use in a br-cab or the intended application. You can make the volume of the cab less or the tuning higher, but in some cases you'll just have to sacrifice to much.

Guitar loudspeakers are often designed to exceed Xmax. In those cases the "sound" of the guitar speaker/combo is partially created by the distortion formed. Most speakers that are advertised as being guitarspeakers will have a very tiny Xmax. Because the Xdamage (Xmech) is several times higher, the speaker will not be damaged. The sound however, so useful for a guitar will ruïn the sound of a good PA.



Edited by mobiele eenheid - 12 March 2010 at 4:16am
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2005 at 8:11pm

Transfer function magnitude

 

This is the so called frequency response. Here the amplification or weakening (in dB's) is put against the frequency. This is where you usually try to get a response/ line as flat as possible, without getting into problems on the other pages. Small holes or peaks won't matter to much (up to about 2 dB). The response doesn't necessarily have to be flat, tho it's common to try so.

 

WinISD Pro standardly calculates a frequency-response as flat as possible and as much low-end extension as possible. The program doesn't keep the groupdelay nor the Maximum Power in mind. Sometimes the volume and tuning will get extreme values, sometimes it's very useful.

Designing a loudspeaker is about finding a compromise between all those values. It's person/application depended what's most important to be correct. Luckily there are some standards to keep in mind.

 

If you are using your basreflexsub for PA don't try to get as much low end extension as possible. For most parties a f3 or f6 of about 40 á 42 Hz is useful enough. This doesn't mean that the frequencies below 40 Hz will not add to the sound. In most cases they will, especially for Home Theater-applications. But when used for most types of music it's not necessarily. Also low frequency production is very energy and space consuming and therefore quite the opposite of having a small soundsystem. If you're convinced you need better low frequency reproduction, tune at the Fs of the driver or higher.

 

For PA-applications you'll get most times more low end extension with an 18 inch then with an 15 inch. This is not just because the 18" is bigger. The bigger size will give it (in principle) changes in T/S-parameters that will make it more useful for low frequency reproduction. But these changes can be made in more ways than just increasing the diameter.

Actually a lot of speakers optimized for low frequencies are 12" but due to the low Fs of these speakers, necessary to get good low frequency reproduction, they're also less efficient and thus need (much) more power to get to the same SPL-levels as an average 18" would need.

 

There is a physical law that correlated size of the cab, efficiency and low end extension. For instance you can make a relative small cab to go very low (below let's say 20 Hz) but this will result in a inefficient model. On the other hand you can make a cab of the same size go much louder due to it's efficiency. But then you won't get the same amount of low end extension.

Thus the reason why for most PA-applications 40 Hz is low enough. You could make it go lower but the cabs would increase in size accordingly. In the end it's your personal choice and application that will make most choices for you.



Edited by mobiele eenheid - 06 July 2009 at 10:58am
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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2005 at 8:06pm

WinISD Pro

 

Frequently I encountered questions about how to work with WinISD, or people that think that they have to let WinISD do all the calculating. And build the cab WinISD comes up with right after starting up.

That's why I've written these pages that should explain the meaning off the most important tabs/pages from WinISD.

ATTENTION: A lot of people are still working with WinISD 0.44. De explanation given is about WinISD Pro (a6 and a7). It's mostly that WinISD 0.44 doesn't have the pages these explanation is about and by that's not giving the information necessary to make a good cabinet.

To make things more clear for the reader/practicer I've added a few examples based on the 18sound 18LW1400.

I used the following Thiel/Small-parameters (to avoid the use of other parameters and thus different results):

 

18LW1400

Qes: 0,31

Qms: 7,2

Qts: 0,297

Fs: 31 Hz

Vas: 297 ltr

Mms: 190 g

Re: 5,0 ohm

Bl: 24,7 Tm

Le: 2,3 mH

Xmax: 9 mm (it's actually 5 mm, but that's an other story, I'll use 9 mm here anyway)

Pe: 700 W (that's the W RMS value, nowadays it's specified as 1000 W AES).

Sd: 1228,5 cm^2

Z: 8 ohm

 

The other parameters are calculated on the hand of these, by WinISD Pro. The Help-function of WinISD Pro should give you the basic knowledge to fully understand this slightly advanced explanation. The explanation is about making a basreflex sub, since this is one of the easier things to build.

The standard calculation done by WinISD Pro after start up is leading up to confusion amongst many users. The only thing the program does is calculating a frequency response as flat as possible., with as much low end extension possible as well. The program doesn't bother with the powerdip created, groupdelay, etc.


A bug that can be encountered in a7 is that the tuning will be suddenly be resetted to 0.00 (zero). If you're having problems inputting T/S-parameters (and getting them accepted) turn of the auto-calculation, see also the updates sectio below.

WinISD Pro a7 is surely not the best program out there. But since it's freeware (that's how LEAP started ;) it's a good start in understanding how the parameters influence the function of a loudspeaker, furthermore to avoid the "rotten apples".

 



Edited by mobiele eenheid - 12 March 2010 at 4:15am
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Young Croc
Young Croc


Joined: 15 August 2004
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 30 January 2005 at 8:00pm

Hi all,

I?m working on the English version of my small guide for WinISD Pro. By translating it into English it should be able to help a lot of people out there starting with speakerbuilding-simulating. Any advise-point outs are welcome as well.

Scroll down for the Hornresp guide.
 
Johan


Edited by mobiele eenheid - 07 February 2008 at 2:40pm
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