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.

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.

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.

T/S-parameters

Hornresp can calculate BL, CMS, RMS and MMD out of other T/S-parameters. Just double-click on the tab and a calculator will appear that will calculate the mechanical parameters from the T/S-parameters (Fs, Qes, Qms. Vas).

SD:

Driver diaphragm piston area (in square cm / cm2) - Table: Typical Sd values for different diameters. Footnote: 1 sq inch = 6.45 cm^2.

Driver's force factor, a measure of motor strength - This is equal to the magnetic flux density in the gap (B) times the length of voice coil wire in that flux (L), and thus the units are Tesla-meters. Sometimes it's stated as Newton/ Ampere's, read here why that's the same but different.

CMS:

Driver diaphragm suspension mechanical compliance (m/Newton) - Compliance is the inverse of stiffness. If you double click on the CMS box, the calculator will ask you if the {VEL}, {DEN}, and SD values are correct. Then it will ask for the driver's Vas in litres (cubic dm / dm3).
Footnote: 1 cubic ft ~28.32 litre.

RMS:

Driver diaphragm suspension mechanical resistance (Newton.sec/m) - For this parameter to be calculated you need CMS (so calculate this first if necessary), Fs and Qms.

MMD:

Driver diaphragm, voice coil, and other moving parts dynamic mechanical mass - Mms also takes the weight of the air displaced by the driver into account. Therefore Mms is higher, but usually not by much. Note: How Mms is derived might differ amongst manufacturers, Mmd can be calculated.

LE:

Driver voice coil inductance (Milli-Henry's / mH) - This parameter can't be calculated from other T/S-parameters. The Le will have a large influence on the high frequency roll-off of the horn in some cases. A higher voice coil inductance will limit upper usable range, however in a bass horn other compromises such as bends in the horn and the front chamber volume could impose a more significant limit.
An Adire Whitepaper demonstrates an impact on transient response which may be a more significant effect.

RE:

Driver voice coil DC resistance - For an "8 ohm driver" this will generally be around 5 - 6 ohms, for a “4 ohm driver” around 3 ohm.

... end of T/S-parameters

ND:

Number of drivers in the loudspeaker enclosure. - Input parameters --> Tools --> Driver Arrangement (or double click the Nd-tab). As Nd doubles so should horn parameters such as S1, S2, VTC, VRC, AP, ATC, etc. to keep the horn(s) the same as before. The horn length will remain (approximately) the same.

In the Nd-window you can choose series, parallel and isobaric loading. The picture on the left shows the situation. You can also choose a number of arrangements: Normal Nd (front and rear loaded horn), Offset OD (Offset Driver), TH/ TH1 (Tapped horn, see also below under Tapped Horns). And a bunch more exotic options, the number of which, is increasing over time, such as Multiple Entry Horn and 6th/ 8th order band pass.

VRC:

Rear compression chamber volume (litres) - This is the horn's rear chamber (in case of a front loaded horn). In most cases it's a closed chamber with the speaker mounted into one of its walls, like in a standard sealed box system.

• A horn sub that is meant to be used in singles generally has a large rear chamber to get a decent output on low frequencies. The downside of a large rear chamber is the accordingly lower mechanical power handling (Xmax is reached with a lower power input).
• A horn sub that is meant to be used in stacks generally has a smaller rear chamber. These kind of subs trust more on the horn loading of the stack to get decent output at low frequencies. If a horn like this is used on its own, it will have a relatively large dip in the frequency response (like the LAB horn). By stacking multiple horns together the mouth area will be enlarged. The lower the frequency, the bigger the mouth area needs to be to give good results.
• Band pass Horns (BPH) generally also have large rear chambers, mostly combined with a large VTC (throat chamber). It's hard to define a specific number here but a rear chamber above 80 litres (for an 18" or smaller) would be considered quite large. BPH are also typically meant to be used in multiples. The horn length is too short to be a true horn. By stacking the horns together, the virtual horn length will increase slightly due to a larger end correction from the larger mouth area, thus lowering the cut-off frequency of the horn compared to a single one.

LRC:

Rear compression chamber average length/depth - If you mask the resonance of the rear chamber, this has no influence (Input Parameters --> Tools --> Options: Throat chamber and rear chamber resonances), so you can put here any number you like (i.e. 20 cm). If you don't mask the resonances this parameter can influence where notches and peaks in the high frequency response occur, but in most cases these will be out of the frequency area you will use the sub for. As the LRC becomes larger, these resonances will be lowered in frequency. When you're new to Hornresp you can mask it but keep it in mind when you are finishing up on a design that will actually be built (and off course it will).

FR/ TAL:

On default FR and TAL are shown (for normal Nd and Offset OD). Upon double click on FR/ TAL (the letters, not the tab), they can be switched into Ap/ Lpt or Ap1/ Lpt (see below).

FR:

The airflow resistivity of any stuffing / damping material used in the rear chamber - You can leave it at default if you're using stuffing but don't know any values for it. More typically, stuffing is not necessarily used in sub horn rear chambers, so you can change this to zero.

TAL:

The thickness of the used isolating material - You can leave it at default or zero depending once again on whether or not you want to use stuffing.

AP/LPT:

These parameters have a different meaning, based on the driver arrangement (Nd).  For normal Nd and Offset OD, the meanings are listed below. For TH/TH1 see Tapped Horns, further down in this guide.

On default FR and TAL are shown, upon double click on FR/ TAL (the letters, not the tab), they can be switched into Ap/ Lpt (rear chamber) or Ap1/ Lpt (throat entry). The difference of which can easily be spotted in the Schematic Diagram.

AP:

Rear chamber port cross-sectional area (sq cm) – Ap and Lpt characterise the port dimensions (Helmholtz resonator) in the rear chamber. The tuning frequency can easily be spotted in (amongst) the SPL response and diaphragm displacement-window as the bottom of a steep/sharp dip in the response.
For the combined or separate frequency response of the driver and/ or port, use Tools --> Output --> Horn/ Port/ Combined (Difference in cm).

LPT:

Rear chamber port tube length (cm) – See AP (above) and Port Assisted Horns (ahead).

Ap1/ LPT:

Specifies the throat adapter, located inbetween the VTC (throat chamber) and S1 (first horn segment).

VTC:

This parameter has a different meaning, based on the driver arrangement (Nd).  For normal Nd and Offset OD, the meaning is listed below. For TH/TH1 see Tapped Horns, further down in this guide.

Volume Throat Chamber (in cm3) - The volume of the front chamber. Notice that you'll have to use a factor of 1000 here to get the number in litres. In principle you will almost always have a front chamber because the volume of the air in/ directly in front of the cone is acting as a front chamber. The front chamber is the volume of air that is compressed when the cone moves forward as opposed to the air that moves down the horn. Sometimes it is hard to know where the boundary between these two areas is, especially with low compression ratio designs.

A large VTC will limited the upper frequency response. In high frequency drivers it's downsized by using a phase plug /phase bung. In a BPH the VTC is generally quite large (making the BPH look like a 4th order band pass, hence the name).

ATC:

Throat chamber average cross-sectional area normal to the axis of the horn (in sq cm) - In case you choose to mask resonances (see the LRC comments) this parameter will not influence the results. In the schematic diagram it's easy to see what the ATC is by comparing 2 different value's. In case you don't mask the resonance, you can keep the ATC the same as the Sd of the driver by default, or change it to move the resonances around.

The tools that you can use/pick depend on the current Window you're viewing. The tools listed below are the ones I used/needed most frequently in the first months (and still). Tools are listed per Window.

Window 1 (Input parameters):

Driver arrangement (multiple drivers) - Normal: With this Hornresp calculates the new T/S-parameters as they would be for a single driver when you replace multiple (of the same) drivers. For simulating multiple driver subs like the Labhorn or mulitple horns when stacked.
Driver arrangement – Offset: Newer feature to calculate a horn where the drive isn't firing straight down the horn but rather starts further down the horn from the sides. I.e. the 1850 horn, CV-style fold, Punisher, etc. S1 – S2 = horn before (the middle of the) driver, S2 -S3, etc. = horn after driver. Compression ratio = Sd/S2.
Driver arrangement – Tapped Horn: For simulating tapped horns (no prompt before calculating). See also Tapped Horns (ahead).
System design (hypex-designer) – With driver: For calculating the optimal hyperbolic exponential horn based on the T/S-parameters of the driver and the needed low-and-high frequency roll-off. Subs calculated these way for PA use aren't very functional in handling, size and weight (and the name “monster horn” quickly comes to mind). The normal route for PA use is to design 4 or 6 cabs that in total will have the same mouth area and horn length as one of these monsters. This way it does show that you need to have realistic demands when it comes to both SPL and low frequency response.
With the use of the "compare"-function (ahead) you can easily reverse engineer this “monster horn” to a more usable size and weight.
System design – From specifications: Newer option, S1 and VRC are fixed, nice for a quick mid/topdesign.
Find: Easy to find a record if you have too many already (you'll), just select and close (or double click). For an easy way to keep the active record list short, see Hornresp Merge (Updates).

Window 4:

Multiple speakers: For calculating the response from multiple cabs (stacked).

Window 3,4,5,6,7:

Sample: Depended on Window-type this gives a sample at a certain frequency. For example at Window 6) it will tell you the excursion the driver has to make at a specific frequency, so you can see what power your driver will handle.

Window 4,5,6,7:

Compare: Compare the current calculation with the previous. This way you can find the horn parameters that will suite you, by comparing each step with the previous while changing one (or more) parameters each time. Also enables you to compare the influence of the drivers T/S-parameters. You can also use Control + C, to capture the current result.

Window 1 t/m 7:

Options: Throat chamber and rear compression chamber resonances: Here you can tell Hornresp if it should mask the resonance coming from the VRC and VTC or not, it can also prompt you for each calculation.
Options: Default result window: SPL response (4) is regular.