? for Mike P. (and others willing to help)

[dcartes]

I was hoping that Mike P. (and possibly others) would be willing to review this design, and advise me accordingly.


The design will incorporate 4 EHQS 12 (4ohm version) drivers in a tower configuration with a slot port at the top (or bottom).

The inner dimensions of the box are 20" wide x 60" tall x 21.5" deep for a gross internal volume of 14.93 ft^3. After subtracting out .675 ft^3 for bracing, drivers, and port material, I come up with a net internal volume of 14.26ft^3.

The slot port measurements are as follows: 20" wide x 3.75" tall x 23" deep for what I believe (or was told) to be around a 23hz tune.

For an amp, I will be using a Buttkicker BKA1000-4A (1000watts into 4ohms) or 250watts into each of the four drivers. The four drivers will be wired in series/parallel to deliver a 4ohm load to the amp. Hopefully, it will not burst into flames-

The specs for the drivers are as follows:
Qts : .375
Qes : 0.49
Qms : 1.506
Fs : 25 Hz
Re : 1.8
Vas : 157 L
MMS : 90g
BL : 7.2 Tm
SPL : 89.1 dB
SD : 510 M^2
Xmax : 9.1 MM

Magnet Width : 5.25"
Cutout : 11.00"
Mounting Depth : 5.00"
Total Height : 5.60"
Displacement : .04 cF
Outside Diameter : 12.00"

I am including a drawing of a side view of the port construction, a dimensioned front view, and a crudely rendered drawing of the cabinet.

So, I guess I would like to know:
1) Is the design sound?
2) Will I have to worry about over excursion issues with this amp?
3) Any improvements that you would suggest?

Any input that you (and others) could give me on this design would be very much appreciated.

Thanks,
Micheal

[Mike P.]

Looks good. The tuning will be around 21.5 hz. 650 watts will take the subs to Xmax, you'll need a Hi-Pass filter around 18 hz to keep the subs from bottoming out. The port area is big enough that air speed is a non issue. With room gain you should be getting 114 - 116 db at 20 hz.

[dcartes]

Thanks Mike for the quick reply and the graph.

Two things.

Can you explain how I would do the High-Pass filter?

The other is can you tell me what program you used to model the project? Are there any good tutorials that will help me learn to do this on my own? I have built many speakers / subs, but have always had to rely on someone else coming up with a proven design. I would really like to be able to do this myself, but every time I try to do it with the various modelling software, all I become is incredibly frustrated.

Thanks again for your input. I now feel assured that the design is sound.

Micheal

[Mike P.]

An add on unit for a HPF would be the Reckhorn B1 or B2 from Creative Sound Solutions, or the Elemental Designs eQ.2. They would be in the $80 - $100 range.

The program used for modeling is WinISD Pro. There is a tutorial here:

http://www.hometheatershack.com/foru...inisd-pro.html

[Mike P.]

Here is the file for the EHQS 12. Save the file to the "Drivers" folder in WinISD.

Elemental designs EHQS 12.wdr

[dcartes]

Thanks for the HPF advice Mike.

I have ordered a Reckhorn B-1 to use as a High-Pass filter.

I have tried modeling the project myself using WinISD Pro (using the file that you provided), but (like always) my results don't seem anywhere near correct. I have included a screenshot of what my graph looks like. I have also included screenshots of the settings windows I used. Any ideas as to what I'm doing wrong?

Thanks,
Micheal

[Mike P.]

Right click anywhere on the graph for options. Set the ranges to what is shown.

[dcartes]

Here is what I come up with after making the changes. My SPL graph is not even close to what your's looks like.

[Mike P.]

One step at a time, now we're on the same page since we're using the same ranges. Now in the Signal tab, enter 650 into the "system input power" box. Then in the EQ/Filter tab, click on Add, select Highpass, change the cutoff frequency from 20 to 18 and click on Add again.

[dcartes]

Thanks again Mike for taking the time to work with me. I really want to learn how to do this for myself.

Our graphs are the same now.



So I now have the following questions.

1. Is the "System Input Power" box is where you enter the total number of watts to be delivered to the sub from the amp at the nominal ohm load of the sub (4ohms in this case)?

2 .If so, I'm assuming the reason you entered 650w into the box is due to the fact that even though my amp can deliver 1000w into a 4ohm load, the drivers will reach their xmax at ~650w?

3. How did you determine that the subs will reach xmax at ~650w?

4. How did you then determine that I would need a HPF set to ~18hz to avoid the sub from bottoming out?

I'm then assuming that because you determined that I would need the HPF set to ~18hz that this is the reason that you added the HPF at the cutoff range of 18hz in the EQ/Filter tab.

Thanks,
Micheal

[Mike P.]

1. Yes.

2. Correct.

3. The effects of the input power can be seen on the cone excursion graph. Input power is limited to Xmax or the subs recommended power handling, whichever comes first.

4. The effects of a HPF can also be seen on the cone excursion graph. Without a HPF the graph shows over excursion below 18 hz. With a HPF the sub is now protected, as the graph shows.