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post #1 of 40 Old 12-14-14, 01:44 AM Thread Starter
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Ported how low is too low?

Monday there will be a brand new Ftw21 sitting on my door step and this seems like a good time to ask a few thing's.

First is at what point have you just ported a subwoofer just too low? I don't want to run a high pass filter if it can be avoided and I understand that there is a trade off of output for going low but is there anything else that you lose in the deal?

I looked at 30cf sonotube ported to 12HZ will that allow me to avoid the hpf or at that tune am I still going to be stuck with one. The amp I have is a cv-5000 which if I recall will do around 1800 watts into 4 ohms and not too sure but maybe fairly flat to 10hz maybe lower.

My wife told me I can place 2 of these subs into our front room and I have tried to tell her how large they will be but she said she does not care about that as she will be using them as well and they will be behind the couch until the basement room that is built some day.

Anything else I need to know before I start this quest or will this work fairly well and with gain from a second driver down the road make up from the loss of 12HZ.

Thanks.
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post #2 of 40 Old 12-14-14, 03:34 AM
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Re: Ported how low is too low?

I think you should be fine. 12hz port and electronic roll off will net you a some what safe driver. Not 100% but it is very possible depending how hard your going to max out the FTW. Why do you noy want to use a Hpass?

I will be doing a sealed build with my subwoofers and while a Hpass is not needed I like having an external EQ to dial in rthe sub in my room.

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post #3 of 40 Old 12-14-14, 03:39 AM Thread Starter
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I want to avoid the hpf because of what it does to the signal phase plus the extra delay.

I am using a Onkyo prsc5508 so I should not need a extra eq.
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post #4 of 40 Old 12-14-14, 03:45 AM Thread Starter
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As of now I don't have anything to use for hpf I could buy or build something but I would like to try it first without.

The issue comes when I find that one movie that drops to 3hz and eats my driver. I normally watch at -10 from reference but boost the bass. With this setup going from sealed to ported I may not feel the need to run boost.
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post #5 of 40 Old 12-14-14, 10:14 AM
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Re: Ported how low is too low?

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phazewolf wrote: View Post
The issue comes when I find that one movie that drops to 3hz and eats my driver. I normally watch at -10 from reference but boost the bass. With this setup going from sealed to ported I may not feel the need to run boost.
In this day and age? You will find that movie, and chances are it will eat your driver sooner than later. Running a sub without a HPF is a recipe for a short life - especially in a bass reflex alignment - so you might want to reconsider that strategy. Have you ever encountered a manufactured subwoofer that wasn't designed to protect itself? I don't recall seeing one myself, but perhaps there are some out there.

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post #6 of 40 Old 12-14-14, 11:27 AM
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Adding an HPF at 10~12 HZ depending on what is required would indeed increase group delay. But correct me if I'm wrong you can hear the difference between higher and lower group delay but since the filter will be below 20hz this is the feel the bass zone and you don't hear it anyway. Even if it increased group delay 1 octave higher it would still be 20-24 hz and this is still a sort of unheard bass zone.

Personally i don't hear much at all below 22~25 hz I tested it with test tone. Maybe my subwoofer don't play loud enough or I have bad hear. I do feel the bass in this zone though.

This is one of the reason to tune LLT low. You don't hear the added group delay from the port so I guess it's the same for the HPF.
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post #7 of 40 Old 12-14-14, 11:54 AM
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Re: Ported how low is too low?

The chances of infrasonic content below 12-16 Hz is extremely low I would think. There is a short list of movies with 10 Hz content, but a huge list of movies with good bass! Your reasoning is sound, though, for example there are thousands of subs tuned in the 30s for music-only environments that last a long time because they don't see anything below tuning although they usually also have an HPF.

I have to agree, no HPF on a ported sub seems like a bad idea especially for HT. If you want low without the delay of the HPF, go sealed and add EQ. I also went that route and couldn't be happier. The only catch is the extra amp power for the sealed config, plus additional amp power for the EQ. The other bonus is a smaller box size.


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post #8 of 40 Old 12-14-14, 01:40 PM
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Re: Ported how low is too low?

There are movies already with sub 12 Hz content, Inception being one of them, it has some at 10 Hz which caused my setup some angst recently.

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post #9 of 40 Old 12-14-14, 02:07 PM Thread Starter
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Re: Ported how low is too low?

Well HPF it is then. On a other note however how low to port this baby as my wife said do what I want.

With the amount of content below 20hz where is a good compromise between spl and that low port number?

My current setup is a pair of Craig sub 18.1ss that wile I like have never really gave me what I wanted out of them.

With a 12HZ tune and 1200 watts the Ftw will output more below 40HZ then the pair of Craig subs and if I do add a second one it should be able to kill the old setup. On the other hand if I raise the port tune I will get more output from one this is hard.

Does anyone think the content I will be cutting out by going higher will be missed?
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post #10 of 40 Old 12-14-14, 02:12 PM
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Your best bet is to run it through winisd and see what you like. There will be trade offs in size, tune, ect
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