3.5" sub in a huge box with a really large passive radiator?

[Kjeldsen]

Originally Posted by realflow100

i'm just asking a question to see what everyone thinks of my idea >.<

Not a good idea. If you don't mind a large box then use a large woofer with it

[Boscoe]

Originally Posted by realflow100

I'm not talking a full 400 watts to it.. I mean't enough power so it runs just under it's top limits without overheating or getting slowly cooked.

Why don't you download WinISD and add some drivers to it that have good amount of info on. Simulate the response, box size, excursion etc. try and spot the links between the drivers. This way you will start to learn how drivers work in boxes.

[bear]

Back up a second. OP said "with a really large PR".

Once you say that, just use a large driver, skip the PR in a *car*.

The larger the PR, the better the coupling to the air and the more linear it will be (less excursion) but this is irrelevant for your situation.

The *limit* will be more or less the Xmax of the little teeny tiny 3.5" speaker.
Maybe a large number of 3.5" speakers and you'd get somewhere.

So, bottom line, silly idea... needs re-thinking.

My free advice is to start with what you want to achieve in your car, figure out all the parameters that will create a limit of one sort or another (like dimensions, space, etc...) and THEN see (or ask) what might be the best compromises given those realities...

[djmeverett]

Originally Posted by realflow100

How low can a high excursion 3.5" subwoofer go in this kind of box with a really powerful amplifier? (400 watt amplifier)
Not to kill the speaker but enough to drive the speaker Just under it's true limits without distorting or get too hot
And with a really large passive radiator in a big box?
How much bass could it really put out? Would you feel vibrations in your windows in your car? of course you may not see them but could you feel it?

What exactly is the speaker you're talking about or have?
When you say 3.5" are you talking about the size of the voice coil or the diameter of the speaker?
The volume of your box and "passive radiator" or port will be determined by the specs of the speaker.
35-40hz is about as "low" as you'll ever be able to practically achieve.
Your eyeballs will start to vibrate so "seeing" the windows also vibrate may be difficult to focus on and a little fuzzy. Then of course there are your eardrums to consider....damage to both if you expose yourself to that long term.
Buy some stock in hearing aid companies...for your retirement.
You could build a box big enough to sit inside sealed with a subwoofer in it and do your testing that way!
What music to you listen to that is your source of sub notes?

[Inductor]

Originally Posted by djmeverett

35-40hz is about as "low" as you'll ever be able to practically achieve.

Why do you say there's a limit?! Maybe it's your limit...

Also it was like as djmeverett mentioned, there's a misunderstanding between voice coil vs. speaker cone size... What driver do you have in mind realflow100 ?
If for a subwoofer of considerable small dimensions (~2") it's more like a computer speaker, you can look at pic.1,
If for something more of the liking of a 12" 400W and being discussed here look at pic.2, just for the sake of comparison, you decide.
Bose 502B Panaray Subwoofer Speaker

[djmeverett]

Originally Posted by Inductor

Why do you say there's a limit?! Maybe it's your limit...

Well I'm not setting any "limit" just practically speaking....anything below that point your talking a good deal of $$ and design to get something useable that's flat, not distorted and lower than that. And IMHO I'm not convinced lower than that is really practical or useable at least for my ears, eyes and head.
I just think that's part of the phone gag that realflow100 may be pulling our legs here in getting us into arguments for fun and amusement!
That's all I was trying to point out to the OP who I believe doesn't really understand any of this and may be just trolling....no data no info no detail...??
I may be totally wrong but other people on here in multipe posts from realflow100 have noticed this pattern....just saying!

Maybe realflow100 could give us more info on this setup and speakers and such....photos are always good.....

[Inductor]

realflow100 are you a troll ???

[tvrgeek]

I believe the OP needs to take a little side trip into one of the many sims that will show the SPL obtainable for a given set of T/S parameters. ( Sd and Xmax) WinISL does this, as does a spreadsheet on Linkwitz's site. Frequency response is only one issue. The other is the plot that shows SPL across frequency.

What do we think of your idea? Come on, THINK! If a 3.5 inch driver could produce sufficient output at sub frequencies, do you think the market would be full of 12 inch subs? 3.5 inch makes a good headphone. I too have seen designs where they used dozens of small drivers because they were not clever enough to use one. SPL depends on the Sd and Xmax total of all the drivers at any given frequency.

Now on to the PR. A PR is nothing but another way to build a port. It is a sprung mass. It acts just like the air in a port tube. Nothing magic. About the only time they are useful is when the port would be too big for the box. It may be easier than trying to put a 6 foot long port into a 2 foot box.

Now to some of the other remarks. Speaker "seeing" a cabinet. OK, never seen eyes on a speaker. A vary large box is essentially free air. Anything over about two or three times VAS basically. I think that is what was being intended. The reason to put a speaker in a box is to use the "springiness" of the air in the box to counteract the drivers natural resonance. This allows you to try and get sound out of it below its resonance without it flying apart. A bigger box does not mean more bass. It can mean LESS if it is too big.

[Juhazi]

tvrgeek tells us the truth as usual! There is no way to change laws of physics.

Speaking of headphones and perhaps very small and airtight cars might give us some possibilities but I don't think it's wise here...

[DeonC]

Ok guys, can I throw a spanner in the works here?

First of all, that thump in the chest is at around 100Hz, not so? Let's ignore going really deep, and just for the heck of it see what we can come up with here.

Now, let's consider some of the 3" and 4" drivers available from the likes of AuraSound, Mark Audio and TangBand. I know that TangBand used to make a 4" driver specifically intended to be a subwoofer driver. The other brands mentioned also have 4" drivers with good excursion capability.

Next, has anyone here considered what a pair of these drivers could do in a tapped horn? Two drivers, one mounted above the other, could get interesting, not so? Nothing that will keep sub manufacturers out of sleep, but still could be more than most would expect given the size driver. Is anyone prepared to run a few sims using some of the drivers from MA, Aura and TB? I for one would love to see what you can come up with, even if it is mainly just an intellectual exercise.

Enjoy,
Deon