SEALED VS PORTED listening impressions and some in room measurements

[Ricci]

I just recently did a comparo of my sealed SDX15's and a XXX 18 in a sealed box that was basically an extended listening session to each with a comparison of the sound of each and the differences that I noticed. Nothing super scientific just my subjective impressions and I wrapped up by doing a rough set of max output and THD tests.

I figured that I could do the same thing keeping the model and quantity of drivers the same, with the change being the cabinet this time. The electronics, settings and amplifier remained the same for both cabinets. I tried to level match the 2 to be close to the same output level so the gains did have to change a little. I'm no Finnish subwoofer tester so this isn't anything of extreme exactness. The driver in both cabs is an 18" RE Audio XXX 18D2 that has the vc's wired in series for a DCR of roughly 4.5ohms. The amp is a bridged Crown CE4000. The ported cab is a 25cu ft power ported monstrosity of my design that is tuned to roughly 11.5hz with a 10" diameter sonotube and was built by custom builder Nathan Funk of Funky Waves Audio (shameless plug). The sealed cabinet is a very rough, ugly, but solid box of 10cu ft with a removable baffle system that I made for testing big drivers and to take a beating in general. I've been listening to the ported cab for months daily and the sealed cab I have been using and abusing for testing and listening for awhile also, so I have a good general idea of what both are capable of.




The ported cab










The sealed cab ( pardon the finish)














I'm going to do some more listening to music with the sealed sub tonight and possibly a movie too and then I'll post my listening impressions either tonight or tomorrow. After that I'll take some FR measurements and some THD and maximum output measurements for both the ported and sealed cabs.

[thxgoon]

Excellent! Looking forward to your results

[Sonnie]

That is sho-nuff a monstrosity of a ported box there.

[Ricci]

Well I did a bunch more listening to the sealed sub last night. I like it. I really wish that I had easier drivers and smaller enclosures to work with instead of these behemoths. A nice pair of moderate 12's would've been so much easier to do this sort of thing with!. Moving these brutes around is not easy and I couldn't get the 2 cabs in exactly the same spot (surprise.) Plus at the limit testing of each would be a much more comfortable affair with a slightly less stout driver. Maybe it's time for some Dayton RS's...

I listened to a good chunk of Rush Live in Rio last night which I've watched more than once on the ported sub. I also watched Pulse on the sealed sub. On the music side of things I've been listening to a Perfect Circle, MJ's Thriller, Stevie Wonder, Red Hot Chili Pepper's, Mars Volta, Fear Factory, Tool and a little Mudvayne. I've also watched the Incredible Hulk and I plan on watching another bass festy movie tonight on the sealed sub.

So far I haven't noticed a huge difference with the sealed sub on music. It seems to be leaner on the very lowest notes encountered in the music tracks. Actually it seemed a bit leaner sounding overall than the ported cab. Like the sealed one has a smidgeon less of the bass fundamentals and the upper bass is more forward just a tad. Like the sealed is rolled off a hair, or the ported is boosted one of the 2. They both should be fairly similar down to 30hz or so though. It might be interesting to activate the 30hz SSF on the amp with the ported cab and see how that compares to the sealed. With really punchy stuff like Primus the sealed cab seems to have a bit more "snap" to it. This could be just a figment of my imagination or the subs orientation though. Other than that I would like to say that I noticed a huge difference between the two, but honestly I don't with music. Both of them will get very loud and track different bass tones and textures well. At moderate or low levels they seem pretty indistinguishable to me with regular music type material. I've never heard what I would consider overhang, boom or sloppiness with the ported cab unless it was in the track. Maybe partly due to the super low 11hz tune that has the port contributing not much to music at all?

One of the comments I get repeatedly from people when they see the big ported cab is "when are you gonna turn THAT on?" This is usually while they have been listening to the system with it on for quite awhile. They don't understand that it only puts out what is there. They expect to be slammed with crazy amounts of bass the whole time. I have to explain that it IS on and is doing what it is supposed to do. When it gets called on to really do something they will know it. This is always followed with "well I don't hear it", or "make it do something then".

As an interesting note when I switched to the sealed cab it needed the level increased quite a bit to match the level of the ported one. The ported one seems to definitely be more efficient, although I don't know why this would be the case in the upper bass.

BTW.
Remember I'm not A/Bing these I'm going off of memory here and I clearly know which cab I'm listening too, so keep that in mind. I'm not using any EQ (yet) for either alignment either. I'm not a real big fan of large doses of EQ and the sealed cab'd XXX should be well extended down to 25 or 20hz. It really shouldn't matter much with the music listening. I may try to EQ the very low end of the sealed cab below 25hz up to match the ported cab for movies, but I honestly don't know if the amp and sealed cab can take it. I doubt it.

[ISLAND1000]

You've got to EQ the sealed sub to take full advantage of the XXX. Room boost just doesn't do it. The roll-off probably starts somewhere around 60-70Hz and drops at 12db. That accounts for your perceived softness on bass.
You'll use a lot of power EQing the XXX but not more than the CE4000 has to offer . . . . that is for "reasonable" listening volumes.

[Ricci]

ISLAND1000 wrote:

You've got to EQ the sealed sub to take full advantage of the XXX. Room boost just doesn't do it. The roll-off probably starts somewhere around 60-70Hz and drops at 12db. That accounts for your perceived softness on bass.
You'll use a lot of power EQing the XXX but not more than the CE4000 has to offer . . . . that is for "reasonable" listening volumes.

Phil,
The XXX is actually quite good down to 25hz or so in the sealed box. It doesn't start rolling off until the 30hz area. I may EQ the sealed sub up below 25hz but I'm not sure yet. It shouldn't have that bad of a roll-off after some room gain. I'll post up some winisd simulations to show you what I mean.

[Ricci]

So far I've watched Pulse, The Hulk, M&C and Atlantis with the sealed sub and it acquits itself very well. I'd have no complaints using it full time. It sounds good and I never heard it complain with any of the movies. The lowest bass was well represented. I could tell when it was there even though it was substantially lower in level than the ported sub due to roll off. I may try to EQ the <20hz bass up a bit but I'm not sure how much I can get away with if I throw in something like WOTW at a loud level.

The 16hz hallway scene on pulse was good as were the M&C cannon blasts even without EQ boosting. On Atlantis when the big undersea robot attacks the submarine it was just as loud as normal seemingly but it sounded like the higher bass was more emphasized as it obviously was with the sealed subs rolled off low end. That's basically how most of the movie notes went. It was good and enjoyable but it does not fill the room with the same power the ported sub does below 25hz. This does not mean it is a weakling in the LFE department. Far from it. It easily has more deep bass power than my 2 SDX 15's (probably nearly a match for 3 SDX's below 25hz) and it can shake the room all the way down to 10hz.

The ported sub is a whole other league with movies though. On Pulse or the other movies it is simply more tactile with more headroom on the deep bass parts. Let me put it this way people talk about "punch" and "slam". The ported sub on certain parts at loud enough levels (like the sonic gun part in the Hulk or a M&C's cannon blasts) it "shoves" you. It's weird it's almost like a short gust of wind or the concussion off of a large fireworks display. A pressure wave just hits you but you don't really hear anything except things shaking. It's really cool and it kind of freaks people out when they experience it during a movie. I just don't think that the single sealed sub has enough ummph <20hz to quite pull this effect off. Maybe 2.

[ISLAND1000]

Ricci wrote:

Phil,
The XXX is actually quite good down to 25hz or so in the sealed box. It doesn't start rolling off until the 30hz area. I may EQ the sealed sub up below 25hz but I'm not sure yet. It shouldn't have that bad of a roll-off after some room gain. I'll post up some winisd simulations to show you what I mean.

Hey Ricci,
I ran the XXX in WinISD in a sealed box and it definitely benefits from EQ. As I said it starts to roll off around 60-70 hz and by 20hz it's down 9db.
As an example, model the XXX in a 6.85 cubic foot box, then add EQ/filter (under filter type) choose Linkwitz Transform, then click on "Modify" and choose an fp of 15hz. WinISD shows a max of almost 112db @ 20hz! That result is what you can expect from the XXX in a sealed box.

I've done the same project except with an LMS 5400 and an XTi 4000. It works! The DSP and EQ in the XTi simulates the Linkwitz Transform circuit plus cures in-room problems. It's amazing.

Which WinIsd sims have you done that show less performance?

[thxgoon]

Nice comparison! Maybe this will be a nail in the coffin for 'ported subs sound bad' aruguments.

I wouldn't worry about using eq with that amp and woofer. Me thinks they can take it Without EQ it's not as fair a comarison as the sealed design rolls of well before the ported design. This means the in room response is also rolled off in the same manner.

[Ricci]

ISLAND1000 wrote:

Hey Ricci,
I ran the XXX in WinISD in a sealed box and it definitely benefits from EQ. As I said it starts to roll off around 60-70 hz and by 20hz it's down 9db.
As an example, model the XXX in a 6.85 cubic foot box, then add EQ/filter (under filter type) choose Linkwitz Transform, then click on "Modify" and choose an fp of 15hz. WinISD shows a max of almost 112db @ 20hz! That result is what you can expect from the XXX in a sealed box.

I've done the same project except with an LMS 5400 and an XTi 4000. It works! The DSP and EQ in the XTi simulates the Linkwitz Transform circuit plus cures in-room problems. It's amazing.

Which WinIsd sims have you done that show less performance?

Man I think that you have some parameters entered wrong for this driver. I don't think it is possible to get it to start rolling off at 60hz no matter what you do or how small you make the box. These drivers are very extended in a sealed box more so than any other driver I can think of. The roll off starts at 35hz in the 10 cu ft box that it is in and is 3db down at 22hz. -6db at 18hz. See the attached FR sims. Green is sealed and orange is the ported. I've included inductance into the sims. BTW I'm also aware of what the XXX can do in the sealed box. I've been watching movies at near reference level with it for days.