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Discussion Starter · #1 ·
I'm playing around with Sonosub.exe and winISD and have come up with some measurements.



A few questions:

First:

The area after(lower) the tune frequency, should I put much thought into this ? I was under the impression that below the tune frequency, distortion rises quickly. So for example, I have 2 plots, a 15hz and a 14hz tune. The 15hz tune looks better by about 1.5db from 30hz down to just under 15hz. Then the 14hz tune takes over and is 2 db better down at 10hz. Is this something to consider, or is this all port noise at 10hz.

A 12hz tune looks even better, about a 6db advantage at 10hz, but at 20hz, we're down 2.5db from the 15hz tune. My question is, should I even be worrying about a -10db versus -16db @ 10hz ? The 15hz tune will have almost double the efficiency at the lowest audible range. And at 10hz, the 12hz tune might just rattle stuff more.

Here is a plot of a 15hz tune versus 14hz tune.


Second question:

Port width. Is the deciding factor the calculated 1st port resonance ? Or are there more things to consider. Reason I ask, a 6" port seems much more manageable than an 8" port in regards to length. Also, if a port gets too long for the enclosure, what is the rule of them when going to 2 ports as far as diameter goes ?

Third:

Using an ep4000 to drive these, what would give the cleanest most accurate sounding bass ? I'm interested in accuracy over max spl. The drivers are single voicecoil, 4ohm, 18". So I could drive them 1 driver per channel, or bridge the amp and drive both at 8ohms.

Lastly:

EP4000 amp driven off an Onkyo 818. I don't know what the voltage range is for the Onkyo's preout. If it's too low for the EP4000, can I run both sub preouts into a Y and then to the ep4000 ? would this double my voltage ? This receiver does NOT have the Audyssey Sub EQ so it treats both preouts the same.
 

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Discussion Starter · #3 ·
Thanks for the input. I redid the values with a 360L/12.7ft^3 tube.

I get a end cap to end cap height of 57.76" and a port length of 41.81"

57.76" - 41.81" = 15.95" - Driver depth 9.76" = 6.19"

Is 6.19" clearance from driver to port enough ?
 

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Discussion Starter · #5 ·
That should be doable, I would personally flare the intake. Do you have a IXL or are you waiting for the new ones that are supposed to be coming out?
Don't have the drivers yet. I am working with Mach 5 on variant of the 18" IXL. Single 4ohm voice coil, same xmax. I guess it would be the IXL 18.4. So winISD might be slightly off.

Question about Winisd:

When inputing the box's internal volume, am I putting in the volume before or after sub and port ?

For example, sonosub.exe you enter the "effective volume", and the gross volume is listed below. With Winisd am I entering the effective volume or gross volume ?
 

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WinISD is the effective or net volume, to that you add the displacement of the driver and port to get the total internal volume needed.

I suggest you wait for the parameters of the IXL before you buy any sonotube, you need to see how it models to find out the volume of the sonotube required.
 

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Discussion Starter · #7 ·
Yup, he will be giving me measurements. He gave me some theoretical measurements, but winisd gets upset when I put them in.

Question about clearance to the ceiling. If I were to make these really tall, like 6'8" total height, will there be an issue with the port being close to my t-bar/drop ceiling ? Extension really increases if I can get the net volume up around 530L (19ft^3). I wonder if I could put a spaced out top cap on the top like you do for the bottom using dowels. This would direct the airflow from the port outward instead of straight into the ceiling panels.
 

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Discussion Starter · #8 ·
The larger enclosure looks like this:



Not sure if I want to go that large though. Is the size tradeoff worth the extra extension ? Excursion seems to go way up as well, 30mm at 10hz.
 

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Discussion Starter · #11 ·
How does 420hz and a 14hz tune model? Ideally you'd use an 8" diameter port, and 360 liters just seems awfully small to handle port length.
420L is do-able from a size standpoint. total height would be 6.3' tall. My ceiling panels are 7.5' so I would assume they're far enough away from the port to keep from making weird noise.


As for the curves, the 420L 14hz tune drops efficiency by ~1db from 30hz down to 15hz, and then extends about 1hz. I'm -6db at 12.3hz.

Which means with 2 of these in room I could possibly be flat to 12hz with room gain and Audyssey's low frequency EQ.



Is the extra 70L worth is for a couple hz extension if I'm giving up some in that sweet 20hz to 30hz area ?
 

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Discussion Starter · #14 ·
Steve,

What is "a better implementation of a port"?
I don't understand what that means, please explain?
Thank you.
I had some questions for him regarding port clearance to the back of the driver. With the smaller enclosure the port length was long to maintain a 15hz port. Or I had to reduce the port diameter.

With the larger enclosure I can keep the larger diameter port, keep it away from the driver, and the port resonance frequency is higher.

It's still at 166hz though. If I cross over with my receiver's bass management at 80hz, will I have any issues with the port ?
 

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Discussion Starter · #16 ·
Ok, sonotube is cut, drivers are tested and sitting in the corner. about to cut my end caps tomorrow.

A final decision on tune/port length before I cut the ports.

Here is a winISD plot at 650 watts with a 17, 15, and 13.2hz tune. All three plots have a high pass filter applied to limit excursion down below the tuning point, so it may seem like they're dropping off quickly. In actuality this is a more realworld since I will be applying a filter anyways for safety and headroom.

So, which plot do you like the most ? Don't pay too much attention to spl as I will be running 2 of these with 650 watts to each. Extension is more important to me than max spl. Excursion is safe, just a hair over xmax, and port velocities are ok, a max of around 24m/sec on the 13hz tune.

 
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