6.5" Subwoofer

[Flipx99 0]

I was curious of any of your experiences with 6.5" subs. I saw this thread on DIYMA as sometimes they get too technical for me.

I was wanting to put two 6.5" subs in my truck, but I am curious how well they will balance with the rest of my system. I currently have 8" Rainbow X-plain midbass and Cal27 tweeter.

I can fit 8,10,12,15,18...but if I can do more with less, I think that will be great.

[DevilDriver 28]

Very simple version: 6.5" speakers are, by nature, a bit limited in the amount of output you can achieve. There are a few designs out there that are almost viable for subwoofer duty if you get triplet's or quadruplet's going. The Tang-Band 6.5's are decent, the Mpyre 65X does not seem very dependable, and the EU-700 is, well, from eD.

More complicated: There are two really big considerations in terms of output: 1. Linear displacement, determined by Xmax (the linear stroke) and Sd (the effective piston area of the speaker), and 2. Efficiency, determined primarily by Sd, Mms (moving mass), and BL.

In terms of linear displacement, a 6.5" speaker is limited in two ways. First and most obviously, it has a small diameter diaphragm. In general, a 6.5" speaker will need roughly 1.5X the linear Xmax that an 8" speaker has to achieve the same amount of linear displacement. Second, a 6.5" speaker's Xmax is usually limited by the suspension. Again, keeping things very general, a 6.5" speaker has a smaller frame, and thus is accompanied by a smaller spider. The spider itself will be limited in the amount of throw it can support because there is not a lot of spider there to maintain a good restoring force over a long stroke. Of course, you can fiddle with the corrugations in a progressive spider to try and gain more throw from the suspension, but you will still be limited by the cone and frame geometry.

In terms of efficiency, we already acknowledged that Sd (the effective piston area) is limited on a 6.5" speaker. The obvious positive here is that Mms (moving mass) is quite manageable. However, it is tough to get a lot of BL into a 6.5" speaker. To increase BL, we want to increase the number of windings in the gap or increase the amount of flux in the gap (assuming we haven't approached saturation yet). Increasing flux in the gap is simply a matter of reworking the steel in the motor, ie. going with a taller top plate to carry more flux, going with a wider or taller magnetic stack, etc. However, you still need the windings in the gap to utilize this flux. To do so, it is often easier to go with a wider diameter former. But since there's not much usable spider already (and we'd only be eating up more spider by increasing the former's diameter), we're really digging ourselves into a hole.

Also, there are sacrifices in between the two. If you try to increase efficiency, by upping BL, you'll give up some linear excursion in the suspension. If you try to keep a lot of linear excursion, you'll give up some windings in the gap and lose BL, thus losing efficiency.

Personally, and this is just my opinion, an 8" is the absolute smallest I would consider usable for a subwoofer, and even then, you can run into similar issues. Hell, there are a lot of 10" subs on the market that have some major difficulties reaching the levels of excursion their motor is capable of.

[DevilDriver 28]

Just to add to this quickly...

Hoffman's Iron Law. It applies to speakers, too! Take a 6.5" speaker for example. They generally take a very small enclosure, have medium efficiency, and lack low frequency extension. Now, it's hard to change enclosure requirements too much for a 6.5" speaker; if we try to gain more low frequency extension, we're going to give up efficiency. If we want more efficiency, we're going to give up low frequency extension. Hoffman's Iron Law applies directly to speakers, the same way it does to enclosures.

[Aaron Clinton 2,372]

Neil's explanation was excellent, I feel it would just be safer to go with a pair of 8's or a single 10 that can fit in your install and blend well with your front stage.

[///M5 2,833]

Also having a midbass that is larger than your sub, is umm wrong. Considering the small size of boxes that today's 8 & 10" drivers can fit into it really would be prudent to step it up a notch.

[Flipx99 0]

Console is not wide enough for an really...I think I can do some mods if I had a nice sealed 10. It would just need to be cast basket instead of a 12 spoke. I would need it to slope in a narrow way pretty quick.

Just kicking around some ideas...

0--------0

I am never going to finish because I keep thinking of "better" ideas. My install keeps evolving.

Edited August 30, 2007 by Flipx99

[ANeonRider 3]

What vehicle?

[Flipx99 0]

What vehicle?

I drive an 01 S-10. The width of the console is ~6.5".

I have an ext cab and fire the sub backwards....and hide the amp in the jump-seat area.

So what I guess would be best is a 10" that would work in around 1 cf with a motor diameter of less than 5" to fit in the space.

It would stick out some behind the seats, but I don't think that would be a huge issue.