How long does this port need to be?

[cameron paterson]

Here is a website that tells you what length your precision port should be:

http://psp-inc.com/tools2.html

volume of box: 2.25
tuning frequency: 45hz
port diameter 4"
number of ports: 1
It says that it should be 5.7"
So with a port that has 2 flared ends how long does the port have to be?

 

[TLS Guy]

Here is a website that tells you what length your precision port should be:

http://psp-inc.com/tools2.html

volume of box: 2.25
tuning frequency: 45hz
port diameter 4"
number of ports: 1
It says that it should be 5.7"
So with a port that has 2 flared ends how long does the port have to be?

Bogus site.

 

[cameron paterson]

How long do I need the port to be? To tune at 45hz?

 

[TLS Guy]

How long do I need the port to be? To tune at 45hz?

We have been through this before. You still do not get it.

The T/S parameters of the driver determines how the box is tuned. The port and box is the weight on the spring. The speakers suspension the spring. At least that is a close analogy. So what you are asking is to know what weight to put on the spring for a given frequency, without knowing the specification of the spring.

So what is the driver and its T/S parameters?

 

[cameron paterson]

Dot know T/S parameters. Its supposed to be midbass so I was thinking a tune of 45hz.

 

[TLS Guy]

Dot know T/S parameters. Its supposed to be midbass so I was thinking a tune of 45hz.

For the last time, you can not design or tune a box for a driver you to not know the T/S parameters of. So if they are not published, then YOU need to measure them before any build.

You absolutely have to purchase one of these. No ifs buts or excuses.

 

[lovinthehd]

Didn't Erich give you specifics for the box for the driver? You might just ask him for the T/S parameters, too....

 

[lovinthehd]

He's trying to use this https://www.diysoundgroup.com/bundles/midbass-modules/mbm-12lx-kit.html

 

[cameron paterson]

Erich said that with just using the flared ends of the port it would tune around 45 or 50hz. I want 45hz.

 

[everettT]

Erich said that with just using the flared ends of the port it would tune around 45 or 50hz. I want 45hz.

Why do you want 45hz?

 

[TLS Guy]

Erich said that with just using the flared ends of the port it would tune around 45 or 50hz. I want 45hz.

Well Erich is wrong. The lowest you can tune that driver is 62.86 Hz, and that is using the most extreme extnded bass alignment. I have found the T/S parameters of that Magnum 12 woofer.

A driver will always tune somewhat above Fs.

I have enclosed the design below.

Your port should be 4" diameter and 7.3" long flared at both ends.

This is the data you needed to have.

Rated RMS Power:500 Watts Rated Max Power:1000 Watts Impedance:8 Ohm Sensitivity:93.5db 1w/1m Frequency Response:35hz -800hz Voice Coil:3" Magnet:109oz. Ferrite Overall Diamater:12.4" Cutout Diameter11.1" Mounting Depth Weight:19lbs.



Re:7.09 Ohms Le:1.55mH Impedance:8 Ohm Fs:41.9Hz Qts:0.34 Qes:0.35Qms13.09Vas:68.9L (2.43cuft)Bl:20.7Sd:520 cm^2Xmax:9.15mm

 

[everettT]

I suggest Cameron that you order these two books. The first to help you with speaker design
https://www.amazon.com/Loudspeaker-...n+cookbook&dpPl=1&dpID=514AaEuy+4L&ref=plSrch
The second to help you understand your room and Psychoacoustics
https://www.amazon.com/Sound-Reprod...loyd+toole&dpPl=1&dpID=51kMjxzNGDL&ref=plSrch

 

[cameron paterson]

It has an Fs of 41.9... why cant it be tuned at 45hz?

 

[TLS Guy]

It has an Fs of 41.9... why cant it be tuned at 45hz?

You are new to this and you have a little trouble getting the hang of it.

First that driver is very sensitive. There is an inviolable inverse relationship between bass extension and sensitivity/efficiency of a driver.

The other issue is the stiffness of the suspension. If you have a stiff spring it will oscillate faster.

Now Emminence who make that driver are primarily instrument speaker manufacturers. For that sensitivity is king and not bass extension. So that driver is right in line with their history.

The only way you could extend the bass would be to build an enormous back loaded horn. That driver would be a really good driver for a horn design given the T/S parameters.

However if you look at the design I did for you, this drivers does work for an extended bass alignment. The box Fb is actually 38.7 Hz. The bass roll off is relatively shallow from F3 to 45 Hz where it is only 6 db down. So you are not really arguing over anything important. The key is that the cabinet design is properly done for the driver in question and this design achieves that.

 

[cameron paterson]

So it will be tuned at 45hz if the port is 7.3" including the aeroports? There was talk about tuning this sub at 17hz.
Look here bro:

https://www.avsforum.com/forum/155-...iysg-magnum-12-general-discussion-thread.html

 

[TLS Guy]

So it will be tuned at 45hz if the port is 7.3" including the aeroports? There was talk about tuning this sub at 17hz.
Look here bro:

https://www.avsforum.com/forum/155-...iysg-magnum-12-general-discussion-thread.html

Well there are idiots all over the place. The design I gave you maximizes the linear bass output of that driver.

It is certainly mid bass, as 45Hz is actually still deep bass and the same frequency as the fundamental of a 16 ft organ stop. Midbass is 80 to 250 Hz. So 84 Hz is the fundamental of an 8 ft principal stop which still sounds pretty deep. Certainly anything below 60 Hz is deep or sub bass. So a speaker that rolls off at 60 Hz is certainly getting into the so called mid bass range.

Putting that driver in a box with Fb of 17 Hz is just idiotic and plain wrong.

 

[cameron paterson]

Should I go with 50hz? And just use the flared ports only? Which would make it 6" long.

 

[TLS Guy]

Should I go with 50hz? And just use the flared ports only? Which would make it 6" long.

I gave you the port dimension. There is One port flared at both ends. It is 7.3 inches long and not six. It is 4" in diameter. The box tuning frequency Fb is 38 Hz. The models are all included in the design pdf.

You still do not understand, like a lot don't. The driver determines the optimal tuning frequency. You do NOT ever start a speaker design pulling a box tuning frequency out of the back of your neck.

If you do nothing else today, for Heaven's sake understand at least that much.

You want a mid bass speaker for the driver you specified. I gave you a design that full fills that criterion. Now go ahead and build it.

 

[TLS Guy]

There is another issue that should be pointed out. The F6 of my design is 45 Hz. So if you crossed over to your sub with a fourth order LR low pass and a second order LR high pass at 45 Hz you will have a perfect fourth order LR crossover centered on 45 Hz.. So the FR of that module I designed for you is optimal.

 

[cameron paterson]

Ok so the port with flares need to be 7.3" for a 45hz tune? The flat packs are built. JUst need the amp.