How long does this port need to be?

TLS Guy

TLS Guy

Seriously, I have no life.
Ok so the port with flares need to be 7.3" for a 45hz tune? The flat packs are built. JUst need the amp.
If that is the way you put it fine. It is clear to me you do not understand the whole concept of tuned cabinets. So all I can tell you is do what I say and you will be fine.
 
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cameron paterson

Audioholic Chief
Cool thanks. I will let you know how they sound.
 
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cameron paterson

Audioholic Chief
If I tune my box at 45hz what happens to the box if its crossed over around 50hz?
 
TLS Guy

TLS Guy

Seriously, I have no life.
At this point you have two choices, build the model from @TLS Guy or from DIYSG. The two are not the same and not interchangeable.
The two boxes have the same internal volume. So he can build that box and use the port I designed.
 
TLS Guy

TLS Guy

Seriously, I have no life.
If I tune my box at 45hz what happens to the box if its crossed over around 50hz?
I'm starting to understand what your problem is understanding all this. I'm pretty sure you think that the frequency you tune the box to Fb, is how low the speaker will play. This is absolutely not true. The tuning frequency just about never is the same a the speaker F3.

In the speaker in question the box tuning frequency Fb is 38 Hz but the speaker F3 is 62Hz which is just over half an octave above Fb. So the optimal tuning frequency for that enclosure for your application is 38 Hz and not any number you keep pulling out of the air.
 
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cameron paterson

Audioholic Chief
I wasn't pulling the optimal tuning frequency out of the air. You said the tuning frequnency would be 45hz at 7.3" long port. My question is can I run a hpf that is 50hz thru my mini DSP to the MBM even though its tuned at 45hz?. I don't want it bottoming out.
 
TLS Guy

TLS Guy

Seriously, I have no life.
I wasn't pulling the optimal tuning frequency out of the air. You said the tuning frequnency would be 45hz at 7.3" long port. My question is can I run a hpf that is 50hz thru my mini DSP to the MBM even though its tuned at 45hz?. I don't want it bottoming out.
I did not say Fb, which you call the tuning frequency, is 45 Hz, it is 38 Hz. So this number has nothing to do with the response per se, or where you set your crossovers. It is the box air cavity resonance. Normally it lies pretty much between the two peaks of impedance in a ported enclosure.

The point is that your speaker will be 6 db down at 45 Hz. So this makes it the optimal place to put an LR crossover.

It will not make a whit of difference whether you actually put the crossover at 45 or 50 Hz. You will NOT hear the difference. The real point is that this is the optimal box for what you are trying to do.

However as I said before this whole concept of mid bass modules is total nonsense in my view. If you do do it you want to make it a composite fourth order LR. So that as I told you would be electrical second order LR high pass and fourth order LR low pass at 45 to 50 Hz range.

The whole problem with all this is that because of the overlap of crossovers you get what is called band pass gain. Crossover points should be at least two octaves apart, and preferably more. So that means you need to cross those mid bass units over to your mains no lower than 180 Hz. At that frequency you will localize them, and so they will need to be right up against your main speakers.

The main point is that good speaker design keeps the number of crossovers to the minimum. A good full range pair of single driver speakers can sound incredibly good.

Every crossover added is a quality spoiler.

So any decent sub should be able to handle up to 80 Hz without a problem. Any decent set of mains should be highly capable of handling above 80 Hz at power. If either fail in that regard they are just bad speakers and need thowing out.

So the wise designer finds ways to eliminate crossovers and NOT add them.
 
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cameron paterson

Audioholic Chief
So with a 7.3" port, the sub will be tuned at 38hz?
 
Alex2507

Alex2507

Audioholic Slumlord
So with a 7.3" port, the sub will be tuned at 38hz?
He already said that was the resonant frequency of the box. Let me help you if I can. Just do what TLS is telling you and believe him about where you're at in understanding what's happening here. I built a pair of subs he designed and I still don't understand all the stuff he said while helping but the subs sound great. I've considered using other people's designs or even design goals for possible future projects but have always favored what he had to say based on the strength of the last time I listened to him.

If you really want to hit a particular frequency, ask him what driver to get for the job instead of asking him to do it with what you have. If you want to use what you have, he'll tell you the best thing to do with it, which he has. We all like build pics.
 
everettT

everettT

Audioholic Spartan
He already said that was the resonant frequency of the box. Let me help you if I can. Just do what TLS is telling you and believe him about where you're at in understanding what's happening here. I built a pair of subs he designed and I still don't understand all the stuff he said while helping but the subs sound great. I've considered using other people's designs or even design goals for possible future projects but have always favored what he had to say based on the strength of the last time I listened to him.

If you really want to hit a particular frequency, ask him what driver to get for the job instead of asking him to do it with what you have. If you want to use what you have, he'll tell you the best thing to do with it, which he has. We all like build pics.
Well considering he has a TC Sounds 18" sub, he could have all the mid bass he wants if he throws it in a sealed alignment instead of the ported he has.
 
TLS Guy

TLS Guy

Seriously, I have no life.
So with a 7.3" port, the sub will be tuned at 38hz?
Look, please stop using that phrase "sub tuned to". It is meaningless and confuses you and makes you look ignorant. You have now been told multiple times to stop using sub tuned to x frequency.
 
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cameron paterson

Audioholic Chief
Sorry I am ignorant I don't know about this stuff... I do not want to tune at 38hz. Thanks tho!
 
TLS Guy

TLS Guy

Seriously, I have no life.
Sorry I am ignorant I don't know about this stuff... I do not want to tune at 38hz. Thanks tho!
So after all this you still have no clue. I know you have no concept of what Fb is and you think you can place it where you want. Well you can't. The correct Fb is 38 Hz whatever you say. The F3 which is what I think you are after is 62 Hz in you mind talking about tuned to. It is an extended bass alignment and is 6db below reference level at 45 Hz, which is exactly what you want.
 
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cameron paterson

Audioholic Chief
Will I get the kick in the chest feel better tuned at 45 or 50hz or at 38hz? Answer if u want wouldn't want to upset you lol
 
TLS Guy

TLS Guy

Seriously, I have no life.
see post 35
Well you get the maximum performance when the driver and box are correctly matched. My design does that. So if you muck the design about in any way, you will reduce the kick in the chest you are looking for.

The design is optimal for that driver, so if it is not what you want you need a different driver. What you will get is a highly potent and sensitive driver which will have enough spl. to deafen you. It will not ring and be very tight.

In closing I have to say you have not upset me, but astonished me. Over the years I have taught many students and residents, and you are probably the most obdurate student I have ever encountered.

Learning is for life, and you are very frustrating person to try and teach. In this age more than ever we are all called to be skillful people and be life long students.

If you don't take a hard look at your responses on this thread, life will become increasingly difficult for you and limit your earning potential to say nothing of your life satisfaction.
 
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cameron paterson

Audioholic Chief
Ok I get my amp tomorrow I made the ports exactly 7.3" long! Cant wait to hear them tomorrow! Thanks a bunch TLS Guy!
 

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