Sq/SPL sub

optimus29 said:

I'm looking to change up my sub's.. Looking for 1 10" sub that will do both SPL and sq at same time.. Still want extra boom, but want that kick pedal feeling in chest.?. Looking at Dayton's, SSA dcon, jl, any opinions on sub's that would be good fit for subthump single box??

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Assuming the single driver enclosure has an air tight internal volume around 3/4 ft3, a raw driver w/T.S. rating of .5 to .9 Qts/sealed will work nicely in that space.

It's important to know that every speaker has a "sound" of its own, regardless of where/how/what it is installed in. And every ear listening to a speaker has preferences. So any recommendation is going to be automatically biased. I'm not suggesting bias is a bad thing because there are lots of things only experience can teach us. Things like reliability, and how a particular driver might or might not fit in a particular enclosure have value but "how something sounds" is subjective and biased.

And then there's the psychology of consumerism. What I mean is: humans are predisposed to preferring the results of a decision they've made. When buying and building something as subjective as audio stuff, the power of "needing" to make a good choice biases the brain towards being pleased - because investing time, effort and dollars building something "usually" turns out quite well. SO its pretty common for a hobbyist to be very pleased with the decision(s) they've made as soon as they hear the results of their efforts.

I blather about those things as a way of encouraging you to research available options with all the attributes specific to your project. Qts is the primary specification you are interested in, starting with the enclosure, followed by the Thiele/Small parameters of the driver to be placed in the enclosure.

In that regard, .75 f3 is a GUIDE, not a hard requirement. Look for a driver that:
a) will physically fit (diameter & depth specific to the enclosure)
b) has T.S. parameters within the RANGE of the enclosure (1/2 to approx 1 f3 in a 3/4 f3 enclosure)
c) has power/impedance appropriate for the amp it will be connected to.
d) fits your budget.
e) has a decent quality reputation

The most likely outcome will be deep satisfaction that comes from completing a project and a rewarding listening experience.

optimus29 said:

I was looking into the subthump box.. It can be modified for larger volume..The only thing I'm concerned about is the shell of box is constructed out of 5/8 MDF, and the baffle is made out of 3/4 MDF.. Would that be an issue even though I could have it made down to specs for subwoofer

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Here's the basic deal:
In an acoustic suspension enclosure (sealed box), air is used to support/limit/resist air movement generated by the drivers diaphragm movement. The air itself, since it can’t go anywhere in sealed boxes, provides a cushion against which the dancing diagram can push and pull. As air pressure in the enclosure rises and falls, the walls of the enclosure flex at strange, wild and unknown frequencies adding unwanted “color” to the sound.

When there are no size considerations, an enclosure could be built in a whole bunch of ways to maximize volume and eliminate cabinet induced “coloration”. All kinds of methods can be deployed to manage air movement, brace side walls and mechanically fine tune.

But when building something for a tight space, things change quickly because the combination of both internal and external dimensions become more important.

It makes sense the walls of a small-ish enclosure would be thinner than a baffle from a single perspective: thinner walls = more interior space in a box of limited exterior dimension. Personally, I think the idea of a “thicker baffle” in a small box is hogwash –because the extra 1/8” thickness in baffle is going to lend less sonic benefit over ¾ than would have come from increasing internal volume. Having said that, I wouldn't go tearing apart an already finished enclosure in search of adding .009 f3

Anyhow, don't worry too much about fractional increases here and there. 3/4 & 5/8 MDF in a small box is pretty stout, walls won’t be flexing much, even under ultra-high pressure. Since it’s sealed, tuning comes down to experimenting with a combo of fill, high density foam in corners and EQ.

optimus29 said:

Another question about subwoofers.. What's a good frequency range.. I see sub's that range from 20-200.. And others around 30-300 and up.. Which frequency for SQ sub!!
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Those are meaningless numbers without knowing how they were derived.

You don't want your sub playing higher than 120hz anyway with 80hz being the most popular high cut-off frequency. On the low end, classic rock probably only goes down to around 50hz. They didn't record bass back then. Modern rock like some Linkin Park will get into the 30's. If you want to go lower there are some Decaf tracks (Decaf is a guy that will tweak certain songs and boost frequencies. He's popular in the car audio bass community.) which reach into the 20's.

But all of that is irrelevant because your sub and box combination determine how low your sub will play and how flat your frequency response will be. You can model it in programs like Unibox and WinISD. But then you put it in the truck and it will sound completely different. That's because the environment plays a huge part in bass response. The cabin of the truck is larger than a compact car but smaller than an SUV so you will get some good gain down to at least 20hz.

Oh6 has posted some great in-truck response graphs on the factory sub and I think he used Room EQ Wizard. I have that program as well and a calibrated mic. I just need a decent laptop to run it on. With all of this software and hardware you can find out cabin gain and a lot of other interesting things about the sound in-vehicle.

If you want to dial in your low end there are EQs for cars or even home ones you can adapt like the Mini-DSP or my favorite the Behringer Feedback Destroyer. Using that one I've EQed my home theater to + or - 3db from 120hz to 17hz with usable output around 15hz. It's great but I want to go lower and louder. That's a discussion geared more towards the DIY forum at AVS.

And after a rambling post, I get back to my answer - ignore that marketing crap and buy a quality sub. Your other option is to invest the money on measurement tools and really do some research. It's a fun hobby.

optimus29 said:

Another question about subwoofers.. What's a good frequency range.. I see sub's that range from 20-200.. And others around 30-300 and up.. Which frequency for SQ sub!!
.

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^^^Robert_J has his poop in a group with his comments. The 10Hz delta between the drivers you mentioned might be meaningful if you had the space available to build an enclosure taking advantage of any sub driver characteristic, but RL drivers don't have the option because you are starting with a box that fits a space, not building a box optimized for a speaker.

Your goal is to get on the acoustic *dart board* by selecting a raw speaker possessing characteristics within range of the enclosure that fits your space. Once installed, the dart can be moved closer to bulls eye with use of level, crossover, EQ and phase adjustments that compensate for things you can't model, like "room gain" and phase relationships with the rest of the system.

Adding to what Robert mentioned, if your head unit has auto EQ and remote mic input, running an automated alignment routine in a networked system can extract "last mile" detail out of the system. Once that routine is committed to memory, you are free to fine tune to your ears G spot - and you WILL need to fine tune. Setting up a system is almost never a *one-and-done* proposition because program material varies widely.

You've selected a box that fits space and functional needs. And narrowed your search to a few drivers that will fit in it. Don't agonize over stuff you can't really change anyhow. Hit the gas and go. You're almost there.

Do down fire subs always "sound a lot better" than up or reverse fire? How about forward forward fire? Reverse fire? Band pass? Folded horn enclosures? Do they always sound better in any given environment? Opinions vary. The environment any speaker delivers its output into is an extension of that speaker - hence the term "room gain" - which includes "room attenuation".

In the case of the RL under rear seat space, there are many environmental influence at work. A down fire sub in any environment will have its own energy reflected directly back into it, which, depending on coincident frequency can have positive or negative influence over its sound. The worst effects of that is heard as "muddy" ugly bass. In the application under the back seat of an RL, pressurized air produced by the woofer passes thru carpet, carpet padding, reflects off a coated metal surface, spreading in all directions, including directly back into the woofer itself - crashing into its surface slightly out of time (phase). And that ain't good.

The concept of "cabin gain" is real in every application - it's the aggregate of things that cannot be accounted for in most vehicles - because we are relegated to designing/installing in a space we use for more than just listening. We gotta have places to put stuff and carry passengers. So we have a lot of factors to consider - none of them are "optimal", acoustically speaking.

When an up fire woofer is stuffed under the back seat, and the back seat is down, the seat bottom becomes a kind of horn throat, allowing pressurized air to "squirt" into the passenger cabin on a more direct path than a down fire. That "squirt" *could be* beneficial, resulting in increased output. Lift the rear seat bottoms, and an up fire woofer configuration will sound very different as its energy delivers into the cabin (more or less) unimpeded - which *might* result in more natural sounding low frequency energy.

The upside to down fire configuration is: the woofer itself is protected from debris and liquid accidents. The downside is more "unpredictable" results.

The upside to up fire configuration is: a) the opportunity for "max_quality" by manually changing the environment (lifting the seat). b) The hard surface under the seat (into which the woofer will fire) affords potential "squirt" more directly into the listening space. The downside: potential contamination from debris falling onto woofer surface & potential damage from accidental liquid spills.

Know this: everything here is offered at the concept level, coming from a place of no real world experience specific to the RL. But the comments are universally true for any vehicle and - for that matter - any listening space.

Conceptually speaking, I favor up fire configuration. Primarily due to the (potential) beneficial effects of lifting the rear seat.

Software allowing frequency, level and phase adjustments are meant to compensate for many (but not all) of environmental effects on speaker systems. So getting the most out of the physical set up is important.

Your check list is limited and prioritized. It goes like this:

Space available. Entire area under back seat, or partial?
If partial, Which side - larger or smaller?

Up fire or down fire? Consider all factors, make the choice and move on.

Now you know enclosure internal volume.

Choose the sub driver that fits budget with T/S parameters dictated by the enclosure volume. Unless you are designing a specific enclosure to optimize sub selection, get in range of the space available in your enclosure of choice. Move on.

Once installed, tune to your ears pleasure.

Done

BTW: which ever route you go, you WILL be happy with the results. Because its yours. And you built it.

This upfire downfire topic is a good one. I had a ported 8" upfiring but the port was firing on the side.

The upfire with a sealed box, may generate some vibrations or rattles from the plastic under the seat. I still think to have a very close gap in either direction, down firing may be the preferred choice.

Until you try it you may never know it.

Perhaps build a box you can reverse and try it both ways, have some T-nuts on the corners to add screw feet on the corners, that way you reduce the gap on the top when upfiring it.

And screw the feet to use it in a downfiring application, you will have to spend a lot of time choosing crossing frequency points and EQ settings to find the bass you prefer before deciding the final position.
In a downfiring application I would not be too afraid to get as close to the bottom, and leave just a safe space for max excursion without hitting the floor if the sub needs larger mounting space, while in an upfiring position, the bigger the gap from the seat to the box the better, that way you may be able to Velcro some 1/4"-5/8"closed cell foam, helping to just deflect the sound a bit, to prevent all energy and air to reflect on the plastic.

Constrained layer dampening material like Dynamat will be better, but messy and hard to remove.

Perhaps a sheet of aluminum sandwiched with CLD , and just Velcro or glue it to the bottom of the seat, it may only take 1/8" or less, and it could be also just laid on the floor for the other application. You may also glue some fabric on it to make it blend and match the sub fabric, to avoid the silver sheet color on either side.

Either side will work, and like you were told, don't over analyze it, our cabins provide great output and with good tuning even an inexpensive average sub, can sound good.