Starting to think sealed is best for extremely low HT - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 230 Old 09-07-2017, 02:15 PM - Thread Starter
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Starting to think sealed is best for extremely low HT

Hey guys I'm trying to design some HT subs and crossing over from car subs. Usually I build ABC ported boxes.

Here's what I'm seeing as the problems with either a regular ported or even an ABC ported box when trying to get to 10hz or upper single digits.

1 - High group delay especially when a HPF (subsonic filter) is factored in
2 - needing that HPF due to cone excursion below the tune
3 - the conundrum of increasing port area for lower velocity causing lower 1st port resonance

If I model a large sealed box for max excursion + 10%-20% @ 5hz I do get about -10db/octave but group delay is great and has no issues with regards to ports. With ported you try to address one problem and effect 4 other things but I can't get around the port resonance with low tuning even when I plan on running the subs only to about 40-50hz on the top.

The last boxes I built were for my front speakers which I screwed up with my car audio mentality. For arguments sake each 12" sub which was supposed to be the woofer in a 3 way is in 2.5cuft tuned to about 31hz with 2 3.5"x3.5" ports ~24.5" long. 1st port resonance @ 276.5hz, peak port velocity at 11.75m/s, peak group delay 36ms @ 16hz. As far as I'm concerned that all works out great minus the resonance and using a sub as a woofer (the original woofer blew with the new cabinets so I scavenged my Infinity 1260's).

Now that I'm going to build a dedicated home theater room I want to separate the subs from that frankensteined 3 ways crap and do it right but go low for HT now that I understand car audio low isn't the same!

Anyway I'm not really seeing the benefit of ported over sealed when going so low. Even disregarding all of the adjustments and just comparing a 1.5cuft sealed box (300w) to a 6cuft tuned to 10hz (200w excursion match) gets me ~+6db @ 10hz and the ported box needs to cut at 9hz from excursion.
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post #2 of 230 Old 09-07-2017, 02:57 PM - Thread Starter
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Some examples 4th HPF @ 10hz, 300w, 1 6" port:

6cuft 10hz - 122" long port - 55.41hz resonance:
50hz -1.45db, 40hz -2.84db, 30hz -4.92db, 20hz -8.16db, 10hz -13.77db
178ms peak group delay @ 8.56hz
19mm peak excursion @ 16.37hz
9.6m/s peak velocity @ 9.4hz

4cuft 10hz - 185.3" long port, 36.51hz resonance:
50hz -1.35db, 40hz -2.82db, 30hz -5.08db, 20hz -8.8db, 10hz -16.62
166ms peak group delay @ 7.89hz
17.09mm peak excursion @ 17.78hz
6.8m/s peak velocity @ 9.38hz

I also have a 2.5cuft box modeled along with all 3 of these but at 19hz to simulate the upper end if I were to do ABC ported. The thing to keep in mind with that possibility is that even though the port velocities look good at 10hz, those port sizes push the velocity to 13-22m/s for the 2.5 to 6cuft boxes. It also pushes the excursion to about 29mm since the HPF wouldn't be helping at those higher frequencies.
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post #3 of 230 Old 09-07-2017, 03:07 PM
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Its well established that sealed allows for more ultra low end and especially under 10hz with less problems. The reason it isnt an issue often is because with room gain and powerful ported subs many of us can hit 10hz flat or close. There is not a lot below 10 or 12hz but some here want it all. So yes if 5hz is your goal you want some serious sealed subS....capital S as you want several
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post #4 of 230 Old 09-07-2017, 03:28 PM - Thread Starter
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Yea that's the other thing I've been trying to sort out is how low should I be targeting. I'm not planning on a crazy amount of subs or amps. I have 2 300w plate amps to use and 2 1260 infinity subs but I've been looking at jbl cs1214's. While I might buy the jbl subs and save my infinities for putting back in my car, I will not be adding more amps as 600w is plenty. That ABC box I mentioned at 2.5cuft is already pretty nuts and that's just one sub at 300w since I haven't finished the other one yet.

Either way I do not see how to port at 10hz or 12hz I suspect unless the port resonance is not an issue. From my second post you can see those are well within the bass region. My goal is not to always have more or have it all I just want to get pretty close to comprehensive coverage of what's available in movies so if that means 10hz or 20hz then I'll design for whatever that is.

If I go sealed I would probably buy the jbl's and put 2 per box.

In your opinion what frequency should I be looking to achieve as my bottom end? What do I do about port resonance? How much higher can I tolerate port velocity at 10-40hz compared to the more accepted 10-17m/s? What about group delay since we're not talking about 30ms or that frequency * delay < 400, 150ms+ seems astronomically high.
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post #5 of 230 Old 09-07-2017, 03:40 PM - Thread Starter
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White is the only one I've modeled in CAD and have a cut list for. It's 6.578cuft @ 15.64hz, 2 ports 6"x4.5625"x87" but it's an ABC design. The picture I added in a 4th order butterworth HPF @ 14hz. Group delay peaks at ~110ms ~15hz.

Red, orange, yellow are 10hz @ 2.5, 4, 6cuft and the teal, green, dark blue are previous 3's counterparts for ABC at 19hz. All with 4th order HPF @ 10hz. These are modeling the infinity 1260 at 300w.

Grey is 1.5cuft sealed. Ignore the pinks; jbl's, ported and sealed. I can grab other graphs if wanted.
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post #6 of 230 Old 09-07-2017, 04:05 PM - Thread Starter
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On a random note, what would happen if the 1st port resonance matched the tuning frequency?
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post #7 of 230 Old 09-07-2017, 07:52 PM
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There is no one better save all solution. Sealed vs vented boxes have their own individual trade-off. The key is which can you execute better in your room size, setup, gear and personal taste. Forget the group delay and stuff, it is nice to talk about but once you get below 20 Hz, it is not a major factor.
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post #8 of 230 Old 09-07-2017, 08:26 PM - Thread Starter
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So simply put:

Ported Pros:
-shallow roll off compared to sealed; 4-8db/oct
- more output from 8-22hz by 0-6db in the center of that region, spans 6-10hz; all depending on design

Ported Cons:
- much larger
- more material
- build time+complexity
- cost
- weight
- delay
- HPF or excursion problems
- port resonance

Sealed Pros (besides the ported cons):
- more output above 20-25hz but only by 3-4db

Sealed Cons:
- steeper roll off almost perfectly 2nd order 12db/oct

I'm having a hard time justifying ported, what are some opinions on how it sounds to have that extra 4-6db over that 10hz band down low compared to sealed where the sealed box will effectively still have a 1st order drop after room gain. For me this is much less about how loud since it's all relatively close to each other and mostly about the quality and consistency.

Anyway if anyone is curious I derived an equation where you plug in the total cross sectional area of your ports and it will tell you the optimal box volume to use. It's not perfect because it just looks at box and port volumes with no consideration for volume taken up by building materials as that is build specific but should get you close. For example it's less total volume at 20 square inches of port to use a 1.75 cubic foot box volume and port length of 133" than 3.5cuft and 65"; 3.3cuft total vs 4.25cuft total.

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post #9 of 230 Old 09-08-2017, 04:54 AM
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How big is the room? I don't see those subs coming close to enough output sealed to hear close to 10hz. You need a lot of power and subs to get output at 10hz in a room of any kinda of size.
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post #10 of 230 Old 09-08-2017, 09:58 AM
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Quote:
Originally Posted by MeltManBob View Post
Yea that's the other thing I've been trying to sort out is how low should I be targeting. I'm not planning on a crazy amount of subs or amps. I have 2 300w plate amps to use and 2 1260 infinity subs but I've been looking at jbl cs1214's. While I might buy the jbl subs and save my infinities for putting back in my car, I will not be adding more amps as 600w is plenty. That ABC box I mentioned at 2.5cuft is already pretty nuts and that's just one sub at 300w since I haven't finished the other one yet.

Either way I do not see how to port at 10hz or 12hz I suspect unless the port resonance is not an issue. From my second post you can see those are well within the bass region. My goal is not to always have more or have it all I just want to get pretty close to comprehensive coverage of what's available in movies so if that means 10hz or 20hz then I'll design for whatever that is.

If I go sealed I would probably buy the jbl's and put 2 per box.

In your opinion what frequency should I be looking to achieve as my bottom end? What do I do about port resonance? How much higher can I tolerate port velocity at 10-40hz compared to the more accepted 10-17m/s? What about group delay since we're not talking about 30ms or that frequency * delay < 400, 150ms+ seems astronomically high.
i have 4 of the same infinitys in dual boxes. they are in sealed boxes with 2 drivers each...each box is 3.4cft. they are in a very large open living room....with some PEQ I am sending them 362watts for each box....only 180watts per driver. they are close to flat to about 8hz in a giant open room.

i would suggest 10hz as a very reasonable bottom end target. it takes huge spl to hear or feel that....100+db....even 15hz is great. with infinities and some amp boost u should be happy if u can get to flat at 15 to 20hz and may get lucky with extension to 10
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post #11 of 230 Old 09-08-2017, 11:59 AM - Thread Starter
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Room will be about 18x10.5 with 8' ceilings. I know my concept of nuts thus far is not as crazy as it gets but relatively speaking for what they are just the one sub in that box/cabinet I built is not something I can use whenever daily. I feel like after reading so much I am missing a decent amount of the bass considering they are tuned to 31hz and probably very uneven in their response because of being ABC ported boxes.

I would really like to get a mic and software to start measuring things but that's not something I've really looked into. Maybe you guys could recommend something that's not terribly expensive but would be able to give me a good comparative idea. Less concerned that x db measures x db and more concerned that the error is consistent. If I had that I would just measure what I have and go from there.

It's a shame those subs are discontinued, they seemed to me to be a great deal at ~$50/ea especially since they modeled well and I was able to push '750w' to each with a Lanzar Opti 3206D (?model). Modeled better than the 1262 as well but now if you can find them they are ~$125+ and I would assume there are better options in that price range. The only thing I've noticed at least with modeling is you can find SQ subs cheap but low power handling which is what I go for since I'm not at a point to run dedicated electrical circuits just for audio. So far I've noticed the jbl's take bigger boxes, handle less power and imo are ugly.

If I use the infinities they will each have 300w available which if I use that in a sealed box there's no room for EQ or I'll push well past their excursion. I have a design that's pretty close to what I would use for ported and it's ABC; ~3cuft @ ~9.6hz with 2 ports 3.125x4x240 (3 ports total but modeled with 2 for the ABC thing). That box gives a about 7db/oct slope to it's tune doing ~94db @ 10hz. The upper tune is about 18.25hz and that box model gives ~4db/oct from 20-40hz doing ~105.5db @ 20hz. Not sure how accurate it is to compare a box twice as large with twice the power and subs to having 2 separate boxes but it looks like +6db. The problem if it is one is between the upper and lower tuning with the ABC design the combined roll off is closer to a 2nd order like sealed.

Something I've never gotten a straight answer on regarding ABC boxes is if it has 2 peaks or if it's an infinite tune between the tune and 1.9x the tune. That was how I've understood it since 2003 but recently I read somewhere it's just 2 peaks. Anyway the logic as I remember it was that as the frequency increased above the tune the combination of ports became more restrictive progressively so instead of having a dip between the upper and lower bounds you had everything in between. I have noticed with the recent boxes I built that the force of air coming out of the ports can vary greatly between them. When I model these I model the tune, 1.9x and then a few in between.

For the time being I'm going a little nuts with the cosmetic side of the box design and trying to wrap my head around having 2 boxes that are basically 2'x4'x2'... I'd post a picture but Sketchup is choking on doing a 3D intersection. I have no idea if I'll even attempt this cosmetic design as it would really push my carpentry skills not to mention I'm still going to see if I can stuff it with ports.

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post #12 of 230 Old 09-08-2017, 12:21 PM
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Quote:
Originally Posted by MeltManBob View Post
So simply put:

Ported Pros:
-shallow roll off compared to sealed; 4-8db/oct
- more output from 8-22hz by 0-6db in the center of that region, spans 6-10hz; all depending on design

Ported Cons:
- much larger
- more material
- build time+complexity
- cost
- weight
- delay
- HPF or excursion problems
- port resonance

Sealed Pros (besides the ported cons):
- more output above 20-25hz but only by 3-4db

Sealed Cons:
- steeper roll off almost perfectly 2nd order 12db/oct

I'm having a hard time justifying ported, what are some opinions on how it sounds to have that extra 4-6db over that 10hz band down low compared to sealed where the sealed box will effectively still have a 1st order drop after room gain. For me this is much less about how loud since it's all relatively close to each other and mostly about the quality and consistency.

Anyway if anyone is curious I derived an equation where you plug in the total cross sectional area of your ports and it will tell you the optimal box volume to use. It's not perfect because it just looks at box and port volumes with no consideration for volume taken up by building materials as that is build specific but should get you close. For example it's less total volume at 20 square inches of port to use a 1.75 cubic foot box volume and port length of 133" than 3.5cuft and 65"; 3.3cuft total vs 4.25cuft total.
The bolded statement is backwards, below tune, ported subs have a very steep rolloff and the drivers excursion substantially increases - thats why a HPF is typically used a few just below tune. If you're looking at a commercial sub from a reputable company, they probably will have a HPF implemented (amp). If you are going DIY, there are plenty of amps with DSP capabilities that have an available HPF to keep excursion in check. So it doesn't because a problem, as you have it labeled.
Sealed subs have a nice smooth, slow rolloff. Ported subs rolloff can be described like a cliff, while the sealed subs rolloff is like a hill. Rolloff for both usually starts around their F3, which is their -3dB point/frequency.

You can't really give an accurate list of pros and cons of ported and sealed and it apply to every sub. Each sub is different, and each ported cab is tuned differently. For example, the JTR 4000ULF proves most of your output comparisons wrong because its tuned so low. There just isn't a universal list like you have described.

What you need to do is decide on a budget, and narrow down a short list of potential subs within that budget.

If you're looking at smaller subs with 10/12" cones, ported is probably the best way to go. You're really not going to get much output below 20hz with a sealed 10" cone.
When you start getting into 15 and 18" cones, it might be time to look at sealed subs because these are going to have much better +/-20hz performance.
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post #13 of 230 Old 09-08-2017, 01:05 PM - Thread Starter
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bgtighe23 - Sorry bud, you took that out of context, I know I write a lot. If you have the time please go back and read the rest of what I posted for the context you missed. I'm interested to hear what suggestions you have with regards to my specifics.
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post #14 of 230 Old 09-08-2017, 01:14 PM
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When I get to a computer I will show you measurements between the two in the same room.
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post #15 of 230 Old 09-08-2017, 01:35 PM - Thread Starter
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Between what 2? The infinities and jbls? Either way looking forward to it.
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post #16 of 230 Old 09-08-2017, 01:41 PM
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Ported vs sealed. Same drivers. Sealed is easy, ported requires proper size box and port but once modeled is easy. You can't get low with ported without it being big to do it properly. I am running two ported LLTs now tuned to 8hz and beats the crap out of my 8 sealed 18s. The drivers are better though so not really fair.
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post #17 of 230 Old 09-08-2017, 01:42 PM
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The infinities are better than the JBL for low extension.
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post #18 of 230 Old 09-08-2017, 01:53 PM - Thread Starter
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Yea I've always gone ported except for a quick hold over box till I finished a ported build. Difference now is that the new 30hz is 10hz coming from car audio. With car audio I cared less about linear response, just tons of bass. Now I'm trying to sort out if other than being a bit louder going ported is worth it for quality sound and consistency.

Modeling is obviously more involved for ported but it's not bad at all, somewhat of a PITA though for ABC because even though you can get something to look good at a low tune you have to jump over to the higher tune just to find out your air velocity is through the roof. I'm used to balancing all of these different things but the problem is tuning this much lower introduces more considerations that normally don't come into play.

Then there is the fun of designing it in CAD, paying attention to making the best use of materials and cuts then adjusting your box response model.

Sketchup finished choking, this is the front face based on the 2'x4'x2' box size. Still have a lot of contours to figure out then the fun part of stuffing ports in there!
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post #19 of 230 Old 09-08-2017, 02:16 PM
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Ported subs done right won't have those problems. Sound quality should not matter if both done right.
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post #20 of 230 Old 09-08-2017, 02:39 PM - Thread Starter
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I have no measured experience regarding some of these things so I'm probably being more concerned than I should be. Namely group delay, port velocity and port resonance. I've always tried to keep port velocity <17m/s. Never paid attention to group delay or port resonance. In a car especially my fox mustang things like group delay just don't matter much but with this dedicated theater room I have much more control over things and more freedom.

That 3cuft @ 9.6hz with the super long 240" ports seems alright except for the port resonance which is at ~29hz. I've got the excursion <16mm on a 13.1mm xmax, group delay under 20 @ 20hz but starts to climb fast below that; 85ms @ 10hz, peak 183ms @ 7hz. Group delay is a bit worse looking at the 18.25hz top end tune for ABC; 32ms @ 20hz. That top tune has a port resonance of ~105hz so maybe I'm alright because as the frequency goes up so does the response of the box always keeping resonance away from what's being play but I'm not positive on that.

Port velocity peaks at 8m/s for the 9.6hz, 14m/s at 13.5hz and 16.5hz for the 18.25hz tune. Overall not bad at all I think. Where I screwed up on the last cabinets was basing it on the tune and not on the 1.9x tune. I can hear port noise with them but when I plug the 1.9x frequency in I get ~28m/s @ 59.5hz! I haven't played test tones to get an idea yet of what frequency has the port noise but not considering the higher end of the box was my goof.

Right now I'm focusing on tuning as low as I reasonably can within the largest volume I'm comfortable giving up for the boxes and based on best cut use of materials as my initial 6.578cuft @ 15.64hz needs 4 full sheets of 3/4 ply and at $50 each this is not a project that I'm entirely ok with trashing if I'm not close to happy with.
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post #21 of 230 Old 09-08-2017, 04:23 PM
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As far as single digits and coned-based subwoofer's go: IB is better than sealed.

A 3Hz horn sounds cool for max spl etc, but it would be the size of a Boeing hanger...
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post #22 of 230 Old 09-08-2017, 10:19 PM
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I was at a point where you are now.



A SI HT-18 in a sealed approx 7ft3 box...........200 bucks total for box and sub.....super easy to build, uses one sheet MDF.


Add as many as you need/have room for.....if you anticipate a lack of room for them, step up to a nicer driver until you can fit what you think you might need.


I have one in a 12x12 room and it blows the doors off of 4 ported 12`s I was using....no comparison.


I plan to add a second, maybe a 4th.....


If you are worried about the lows at all, skip all the little subs.....go with a 18 and to skip all the worries/planning/research.....just go sealed.


I made my box so I could use a hole saw later and slide in a round port, needless to say, that aint never happening as sealed low end room gain is no joke. Mine goes well below 10hz.....


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Link to budget Home Theater build

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post #23 of 230 Old 09-08-2017, 10:43 PM - Thread Starter
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Nice sub! Just modeled it at 300w in a 16cuft box and it's damn nice! I'll keep them in mind if I decide I want to start spending that kind of money on 1 sub/box. I do like the idea of sealed especially if I want to try my hand at pushing my carpentry skills cosmetically, tough enough trying to design it with 3 16'-20' ports. Anyway here's an updated look at it, currently trying to deal with the ports to see what I can squeeze in there without causing a ton of dead space.
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post #24 of 230 Old 09-09-2017, 01:48 AM
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Have you had a subwoofer system in your home? If you mentioned it I missed it, I just saw you talk about car audio.

I was into car audio before I got into home audio and it takes way more of everything in a house to even get anything like a car for the feel and sound of the bass in car audio. I think you will be disappointed coming from car audio trying to use 12" subs for bass into the teen or single digits. But build them and find out for yourself and then you will know, maybe they will be enough for you.

The only way I see most people being happy with a few 12" subwoofers if they are used near field as in within 6-12" or less of your listening position. Especially coming from car audio most will have a high "tolerance" and "expectations" for the bass they are used to in a car. Even using 18" subs I would suggest at least 1 used near field to get the most "bang" for your buck so to speak. It is going to take a room full of subwoofers to get even anywhere close to the bass in a car if you place the subs far-field in a home.

I would look at the $160 SI HT18" for a lower cost option unless you want to use 6-8+ of the Infinity 12" to get the output down low you will need from them. 3 of the 12" Infinity's will be fairly close to 1 SI HT 18" if WINISD is fairly accurate in the sim.
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post #25 of 230 Old 09-09-2017, 02:11 AM - Thread Starter
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Yea I mentioned that I recently built new speakers but the woofers ended up just being subs especially since I cannibalized my 1260's from the car when I blew the woofers from my Technics 3 ways with the better box. So far I've only gotten to listen to 1 because the finish stage of the build is taking forever; the mdf is all put together just putting 8th inch ply on top, sanding etc. I was impressed with the box and bass portion of the build, not concert level volume impressed but it was nice. I'm also pretty sure I'm impressed because it's music and for movies I apparently don't really know what I've been missing out on. I did notice the room gain didn't help like cab gain does in a car, not saying it isn't there but from reading I think room gain is lower in the spectrum than cab gain.
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I do like how that 18 models and I may go that route but that's a $500 proposition if I go with the dual sub setup like I planned. Would be nice though for so many reasons and I am giving it serious thought. Part of me still wants to do this stupidly complicated build just because it would be an accomplishment and I could implement things better than I did with the recent speakers. Anyway one thing I am trying to keep in mind is that I won't get to use any of this regularly unless by some miracle I get the room treated well enough. Even that single 1260 in that speaker is probably more than I could get away with regularly without bothering the neighbors.
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post #26 of 230 Old 09-09-2017, 02:14 AM - Thread Starter
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post #27 of 230 Old 09-09-2017, 02:38 AM - Thread Starter
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White - current cabinets - single 1260 2.5cu @ 31hz 300w
Purple - SI 18 sealed 12cu 300w
Red,Orange, Yellow - 4.14cu @ 8.37hz 225w (excursion before tune is limiting), ~12hz, ~16hz for ABC
Teal, Green, Blue - messing around with different volumes and tunes to see what it gets me.
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post #28 of 230 Old 09-09-2017, 02:24 PM
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To the OP, read up on LLT. Performance and accuracy wise, for a given driver, ported always wins unless you are limited to a very small enclosure. It's just physics.
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post #29 of 230 Old 09-09-2017, 08:41 PM
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I have no idea what's going on in post 26 but I'm fairly sure WinISD can't simulate that at all. All you can do with WinISD is sealed and ported boxes, and even then it's only accurate if the box is small compared the the wavelengths inside the box. IMO WinISD is a steaming pile of garbage and absolutely can't be used to even get an idea of an ABC box performance. This is especially problematic when extremely low resonant tunings are involved, and even moreso when using extremely small boxes with extremely large ports. In other words you can throw out everything you've simulated, it has no bearing on reality at all.

I'm not a fan of complex bandpass boxes with small cross sectional area ports either, so I would never do ABC.

What I am considering is a variant of a ported box for my roughly 11 x 14 ft room with somewhere around 6 hz tuning.

Here's a couple of pointers. You don't want any UNPLANNED (unsimulated) resonances anywhere inside or near your passband. With single digit tunings this will require massively flared ports. The huge flares keep velocity down at the ends and then you can size the middle portion of the port as small as feasibly possible which will make it shorter. "Flare It" program can help set the required port cross sectional areas.

Single digit bass isn't going to be easy to hear, in fact if you hear anything at those frequencies it's most likely distortion. Bass that low is more felt than heard and it takes a LOT of moving air to feel those frequencies. Even in my small room I'd not consider less than two 18s, and I'd lean toward four 18s if I could afford it. Yes, room gain is real, and you will need all of it, even with multiple 18s in a resonant enclosure. A couple of 12s is going to be disappointing.

Group delay will only affect frequencies that the port supports, otherwise the group delay won't be higher than a sealed box at higher frequencies. While high group delay might sound like a bad idea it probably isn't - are you really going to notice if your 5 hz notes are delayed by even 1/2 second?

High pass filters are not required if you pre audition your media before playing it at insane levels. This is even more true with super low tunings, for example if you are tuned at 5 hz, there's not a whole lot of media with tones lower than that. So run through your movie at low(ish) volume, run through the low (demanding) parts over and over a couple of times and see how loud it can go before it sounds bad. Then don't turn the volume up past that point for that movie. Ever. Then no high pass filter is required. No high pass filter = no excessive filter group delay.

Small boxes with very low tuning and extremely long ports are a bad idea in general. Resonances inside or near the passband will be almost completely unavoidable and if you don't simulate them with proper software you won't have any idea at all how they might affect your response. Making the box larger will allow for a shorter port. Using larger (or more) drivers in a single box will allow for a MUCH larger box with MUCH shorter ports.

Sealed is painfully easy but for very low bass IB is (almost) always the best answer if going sealed. Less power required, less power compression, lower q (which is nice if you don't have eq that can extend to single digit frequencies), efficiency is shifted to lower frequencies. Win win win win win win. Don't worry about overexcursion, just turn it down when it starts to sound bad and don't start too loud in the first place with new media and you won't have any problems. Until a couple of months ago I've never had any type of high pass filter, limiter, or any of that fancy stuff and I don't blow speakers up. Just take it easy at first and turn it down when it sounds bad. But you can get more output over at least an octave if you go ported. Properly planned resonances can be very beneficial and powerful.

Higher excursion subs won't sim accurately unless you really know what you are doing due to lossy inductance issues.



If you are interested, maybe soon I can post up a sim or two showing how to do simple ported boxes with single digit tuning. If you plan it right you won't have issues with overexcursion, resonances etc. Group delay will be high but there's no way around that unless you use tons of power and eq. But I'm only going to post an example if you ask for it. Somehow I have a feeling that you have a long road to travel before you are ready for the complexity of what it will take to do even a simple ported box proficiently.
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post #30 of 230 Old 09-09-2017, 10:14 PM - Thread Starter
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Steve - Yea I came across the term LLT and have been looking into that. I've always been in the ported camp but sub 30hz is presenting issues I've never really had to worry about and I'm not trying to build gigantic boxes. Honestly considering a 2'x4'x2' box was a bit to swallow especially since I plan to do dual subs.

diy speaker guy - Post 26 is the exploded view of the cabinets I built and put pictures up of; the 2.5cuft @ 31hz, 3.5x3.5x24 ports x2 + a third inside for the ABC with the chambers split 2/3 and 1/3 with allowance for the sub volume.
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I've tried to see what is better than WinISD but most of the info is from 2015 and earlier and you're the first to say it's a POS. I'm not saying you're wrong as I have no grounds to personally say one way or the other but I've used it because from everything I've been able to read it's usually regarded as a good program. Anyway I have generally leaned towards larger boxes and smaller ports but after spending some time with Excel and deriving some formulas I realized there is an 'ideal' box volume for a given port cross sectional area when considering simply the box volume and port volumes. Obviously that will have to be tweaked for the dead volume from the wood. For example at 9hz and 20sq in total port area the least amount of volume will be ~2.75cuft for the box and another 2.75cuft of port volume with the ports being 262.5". Conversely if you wanted shorter ports with the same area say 107" length you need about 6cuft for the box and 1.25cuft for the ports. Option 1 total 5.5cuft, option 2 total 7.25cuft.

I like the info on the flared port as port resonance is something I'm concerned about now.

As for those speakers I recently built I modeled them at the 2.5cuft 31hz and modeled a few more up to 58hz but I forgot to size the ports based on the 58hz velocity and no WinISD can't do ABC; I just approximate it with multiple models since as I understand it it's like having that volume from the tune to 1.9x the tune. Maybe I have no idea what I'm doing but I tend to think I have a decent grasp on what I'm doing considering the amount of time researching and building I've got into this over the past 15 years. I'm not saying I have all the information or what I've worked off of is completely accurate especially since I've never had the equipment to go back and measure what I've built. I do know that nothing I've built has stood out as sounding bad and everyone that has listened to anything I've built has been impressed but I take that with a grain of salt since they don't have a lot of experience. The best indication I've had that I was on the right path with my thinking and construction was having a stereo shop owner who did all the custom cars for CDT Audio be impressed enough with my first car sub which was an ABC box using a $50 Pioneer 12 and $100 300w Profile amp running on speaker level inputs and stock cassette radio that he gave me an aftermarket deck to install just so he could hear it with semi-proper connections. I also got to meet with one of the designers from CDT (that stereo shop owner made that happen) and he too was impressed.

All I'm getting at is I have the skills to build pretty complicated things and the intelligence to design but I'm limited by information and tools which is why I'm here trying to get information and be pointed to better tools. If WinISD is such a POS then what do you suggest to use even if it's just for standard ported and sealed boxes that aren't limited like you said to small boxes wrt wavelengths? Do you have a suggestion for modeling ABC boxes as well since I like building them? Do you have any budget recommendations for a mic and software so I can start fact checking my own builds?

I'm not necessarily targeting a specific frequency or sound level. I'm trying to accomplish a comprehensive movie watching experience. I do have some personal limits such as I'm not willing to go larger than a 2'x4'x2' box times 2 for dual subs. I also have societal limits such as neighbors and for the time being roommates. Even when I was back in my house in Texas for my last job, I couldn't get away with turning up my generic Technics 3 way loudspeakers. I literally had the next door neighboors call the city AND the cops on me. Granted they were just grumpy people but I can't imagine how to get away with 4 18's regularly unless you had either extremely good sound control or you lived on some property with quite some distance to your neighbors and you had full say so of what goes on inside the home.

I am going for dual subs because I've read it helps even out the sound reproduction, I would consider more as well down the road but after I get the rest of my speakers up to standard and a good receiver.

My main goal is clean, accurate sound with some SPL as I have always aimed for in car audio; SQ>SPL. I want to build something that has some extra horsepower so to speak but isn't a funny car sitting in the garage waiting to be used on the weekends.

If you have the time I'd be interested to see a simulation like you mention. With regard to this long road, challenge accepted. Please show me how I have a long road in front of me to do even a simple ported box considering I already understand most of the fundamental relationships between adjusting different factors and the carpentry skills to build quite a bit. I'm all about it man, if you have the knowledge and experience and are willing to share I'm willing to learn, that's the only reason I get on forums like this.

Please let me know though about suggestions for the mic and software and better modeling software as well.
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