un ported enclosure = fail??

[Captain_Ahab 5,000+ posts]

 

[dappa5 10+ year member]

ROFLMAO RANDOM MUCH???

 

[dr_peeb 10+ year member]

People say this forum is biased in favor of ported boxes. Ive disagreed with that idea before. But, this isn't even the first time Ive seen a sealed box referred to as 'un ported'... I guess Im gonna have to change my stance on the debate. //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif
What a beautiful not-daytime we are having here. Its very not-hot, but also not too not-cold either. Maybe my not-wife will gimme some not-plutonic relations tonight.

If she reads that she will not.

 

[mvw2 10+ year member]

Ported and sealed boxes sound the same.

What I mean by this is that the vast majority of the sound characteristics made are made by the woofer itself.

All the box really does is change the frequency response. That's pretty much it. The final Q of the sub + enclosure vary a little bit but if built for a flat frequency response, sealed or ported, you'll be typically between 0.6 and 0.7 for both boxes. In the end, the major difference is only frequency response. The sub will sound the same. You play a 60Hz to 200Hz range in music with both enclosures, the sub will play almost exactly the same.

What does change is the frequency response, and this is where the box option becomes important.

Basically you have a sub. It has some frequency response. Let's say it peaks between 70Hz and 200Hz and rolls off on both sides. Let's say it has a Qts of 0.40.

You toss this sub in a box. What this does is modify the Q (relative damping) of the sub. You aim for 0.707 for the sealed box. The relative spring force goes up (air in box becomes a helper spring), and you get a more extended low end response from the sub. Now the roll off point drops down to 40Hz.

You toss this sub in another box, this time ported, tuned for a flat response. The Q again goes up but to around 0.60 instead. Low end response goes up again. We add the port too which is a tuned column of air that has a resonance frequency. The port acts like an EQ boost. We pick a frequency below the roll off point of the sealed box, let's say 30Hz for this sub, and we get a flat, extended response down to 25Hz. The box bumps up the low end response. The port bumps up the low end response. The only side effect of the ported design is that the port uses the energy from the back sound wave coming off the back side of the speaker inside the box. This means the port is out of phase with the front side and you get some group delay effect from this, typically a 15ms to 25ms delay for frequencies around the port tuning frequency. The delay is somewhat undesirable but not a big deal as long as it's not high enough to be noticeable.

Through all of this the sub is the same sub and roughly with the same relative damping. The sound from the sub is the same. It sounds the same. All that is different is the frequency response.

Now placed in a car, we have a secondary issue, cabin gain. This is another EQ boost source but this time a sloping one, typically start at around 60Hz and ramping up roughly at 12dB/oct. from there. Where this starts has to do with the physical dimensions of the car. In the home, there is also a gain effect, but because the room is a lot larger, the starting point is a bit lower.

In a car, the goal is to exactly counter that gain effect with the sub + enclosure natural roll off. If you get it right, the in-car frequency response will be flat. If your sub rolls off too early, the bass can sound somewhat anemic. If your sub doesn't roll off soon enough, you can get a boomy, bloated response. Note that cabin gain is roughly 12dB/oct. The natural roll off of a sealed enclosure is 12dB/oct. They match. For a ported enclosure, it is much steeper. They don't match. As well, the gain effect happens early enough in a car where a ported enclosure really isn't needed for most any sub. This sort of makes sealed enclosures a better fitting option for most car installs. At the same time in-home and with the gain effect happening much later, it makes ported enclosures a better fit in home theater setups.

Now EQing can fix anything in this regard. Ported or sealed, a sub that rolls off at 50Hz or 30Hz, it really doesn't matter. You can just run over the bass frequencies with an EQ (decent one with a good number of bands) and smooth out the in-car response. This feature makes neither option advantageous.

So what's better? Sealed will be more limited by excursion. To play low, you need to move a lot of air. This means it is preferable to pick larger diameter woofers and woofers with more excursion, i.e. not a 10" with 8mm xmax. Ported enclosures have an advantage of using the port to improve low frequency output and requiring less cone movement to do so. This makes the ported design advantageous for woofers of smaller diameter and of less excursion as you can get more output from them then with a sealed design. A ported design has more group delay which can be problematic if very high. Sealed enclosures have very little. One could argue this is a strike against sound quality. Then again ported enclosures typically operate the sub at lower excursion levels meaning the sub is operating more so in its linear range, a bonus in SQ for ported enclosures.

In the end, neither are better.

Really the right option is the one that best fits the end goal. You will pick a sub + enclosure design that will give the correct end frequency response that when used in the car will give a pretty flat frequency response. That's about it.

 

[andrewmoore13 10+ year member]

People say this forum is biased in favor of ported boxes. Ive disagreed with that idea before. But, this isn't even the first time Ive seen a sealed box referred to as 'un ported'... I guess Im gonna have to change my stance on the debate. //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif
What a beautiful not-daytime we are having here. Its very not-hot, but also not too not-cold either. Maybe my not-wife will gimme some not-plutonic relations tonight.

Isn't it not-platonic?

 

[n2audio 5,000+ posts]

FWIW - your sealed box will work fine temporarily. The rec sealed box is 1.0, but it plots ok in 1.75, just use some caution when cranking it - being that much bigger than recs could reduce it's power handling some. Or your could secure something inside the box to take up some space.

You lose some output with a sealed box, but you gain it at the upper end of the sub spectrum, especially vs a low tuned ported box. They both have pro's and con's. I recently went to ported from sealed because I went from two 12's to one and wanted to retain as much output as possible. I've had good results with both.

MVW - is "frequency response" not a BIG component of sound? If two speakers have a different frequency response based on their enclosure is that not "sounding different"?

You're taking the amp challenge basically verbatim and applying it to enclosures.

Edited for accuracy:

Have some one post up the frequency response of a (poorly designed)ported box. Then compare it to the flat frequency responce of a sealed. Then make your decision. If you like more output with a peak go ported.

If you want a smooth responce in all frequencies go sealed.

I've been experimenting with ported enclosures for less than a year, but I know enough to know a well designed ported enclosure can and will usually plot as flat or flatter than a sealed design.

The ixl12 is pre-loaded in win isd pro. Look at the ideal closed plot vs the ideal ported plot and tell me which one is flatter.

 

[mvw2 10+ year member]

It is a large portion of the presentation we do hear, but it's an adjustable factor. I prefer to differentiate characteristics I can change and characteristics I can not. As well, frequency response is not an end-all aspect. Two subs with the same frequency response will sound vastly different from each other. It's the same as two different mid woofers or two different tweeters. Even though you can set them to output the same frequency response, no two will sound the same. Subs are no different.

When it comes to enclosures, I've run a good portion of the variety of subs I've owned in both a sealed and ported configuration and have used several of these subs both in-car and in-house for testing and general playing around. The enclosure largely is a tool for adjusting frequency response. Sub A still sounds like sub A whether it's in a ported enclosure or sealed enclosure. Sub A will never sound like sub B irregardless of enclosure type. Now, we can change the Q of the design and influence some aspects of sound. The same sub at 0.5 Qb and at 1.0 Qb configurations will sound different. We can make the sub looser or tighter, fuller or punchier. We can affect excursion use and power handling. We can modify the roll off point or create a peaky response. There is some variation we can do. We just can't make one sub sound like another. We can make two similarly sounding subs more alike maybe, but they need to sound similar to start with. I've run 7 different subs in my current car. I can't say any one sounded remotely close to each other, and I can't say the enclosure has the majority of influence on the end sound beyond frequency response change, which can be EQed, and potentially relative damping depending on how correct the box is for the sub.