Someone's probably going to tell me that this is a bad idea, but... [Archive] - Audio & Video Forums


View Full Version : Someone's probably going to tell me that this is a bad idea, but...

04-06-2011, 01:21 PM
A wild idea for a DIY project popped into my head (on the other hand, maybe this will be "been there, done that" for some of you). I drive a '96 Mazda B2300 (reg cab). For the past twenty years or so, one of the most common solutions for getting more bass in the space constraints of the average small pickup has been to stick a 6" Bazooka tube behind the bench seat. I don't think I've ever seen a bad review from anyone who has gone this route (although I've heard some grumblings from audiophile purists who disdain them).

Anyway, I'm thinking about what DIY alternatives might be possible. One thing I was wondering about was what setup would be possible just using the sub output from the head unit (Pioneer DEH-P5200HD). The receiver is advertised as outputing 50Wx4ch (commonly said to actually be about 22Wx4ch). The manual claims that when the subwoofer output is turned on, the receiver bridges the two rear channels to make 70Wx1ch into 2 ohms (I'm not sure what the actual output is).

I started looking into what you could do with that, and one of the things I came up with was making a box that would hold four 8 ohm woofers or two 4 ohm woofers (5.25" or 6.5") wired in parallel and using at least two 5.25"/6.5" passive radiators per woofer. One of the combos I'm thinking about is Peerless' SDS-830656/SDS-830657 with their SDS-830880.

Any thoughts on feasability or sound quality issues?

Mr Peabody
04-06-2011, 05:20 PM
You will need a super high efficient woofer or find space for an outboard amp. Although the channels may bridge, a head unit just doesn't have enough room for the size power supply to generate ample power no matter what is stated on paper.

I would also suggest maybe a single large driver if you can make the space work, like a 10". A 6" just doesn't ring "sub" to me. Could provide some fun midbass punch though.

Does the head unit have a built in crossover? If not, there's another thing to consider.

A sealed box would work best in small spaces but sealed boxes require more power. Also, less math to do with a sealed box, just find a woofer designed for sealed box and match the minimum cubic feet. With a ported box you'd have to figure your cubic feet, pick a woofer and find a program or formula to tell you what size and length of port you would need.

It's been a long time since I've done any car audio. If Infinity still makes the Perfect sub series they were very good in sealed enclosures. One of those with a small Rockford bridged and you'd be slamming. If budget is there I actually like Precision Power amps better. Then again, due to space and heat, for your project if considering an outboard you should really use a digital amp.

Why not put a box in the bed with four 15's and run the port into the cab :) :)

04-06-2011, 07:46 PM
Believe me, I know that what I've posted above is an answer to a question that almost nobody is asking. It's been bounced around over on one of the Crutchfield forums a few times over the last several years by people (that probably aren't audio DIY'ers) asking about what most people think of as a traditional sub (10"/12"). I'm thinking of something that's more in line with what the head unit is actually capable of driving.

Based on my reading, I think the "sub output" is really somewhere between 30w and 40w rms. I'm going to assume that it's on the low side of those figures. The drivers that I'm looking at are all rated from 30w to 60w. As for efficiency, could the arrangement that i've described be considered a line array?

The head unit does have a HPF/LPF, both with settings at 50hz, 63hz, 80hz, 100hz, and 125hz. It also has gain settings and bass boost.

I'm not really expecting a lot of "thump" out of this kind of thing, but it would be nice if it was clean and smooth at decent volume, while taking some of the low frequency load off the door speakers. If this were fun and maybe even economical, that would just be a bonus. It would certainly apeal to my "road less travelled" nature!:D

Mr Peabody
04-06-2011, 08:24 PM
When I mentioned efficiency I was talking about the rating in SPL, with using the head unit amp the higher the rating the better, 100dB give or take.

Sounds like a nice project and I can see using what you have and keeping expense down.

04-06-2011, 08:34 PM
The 5.25" is rated at 86 dB and the 6.5" is rated at 90 dB. So no, they aren't super efficient. I'll keep looking. Thanks!

04-07-2011, 07:39 AM
Look at Parts Express and they have some good deals on low depthmount subs. My Son is usuing the Boss (yeah yeah) 10" shallow mount and it thumps. I have seen a lot of junky Boss crap, but something inherent in the shape of their shallowmount design gives that budget woofer better stability and it plays nicely when pushed.

But Mr P is right, you need way more headroom than an in-dash is going to get you. You're gonna clip the chipset in that deck trying to get satisfactory bass. Even a cheap outboard sub amp would be a better solution. Also, don't think for a second your going to get any lower than about 70 hz from a 6" woofer, no matter what its specs say. I love passive radiators, but anything lower than an 8" PR is just gonna make weird noises (been there, done that). PRs are more for home application anyway.

Trust me, I'm not a guy who likes spending money. Parts Express is your friend and they have some decent stuff. Just remember to keep expectation real and take listed specs w/ a grain of salt.

04-07-2011, 08:08 AM
Thanks, 3LB. I'm all over Parts Express, Madisound, etc., so I know what you mean. I will keep this thread updated as I figure out what I want to do. There are truly loads of options, depending on what I want and what I'm willing to spend.

04-07-2011, 08:31 AM
I used the Infinity 1060W Reference Series 10" 4-ohm Subwoofer from here
It worked great for me in the trunk of my 98 Civic.
It's only 91db though.

04-07-2011, 01:04 PM
Thanks, GMichael. If I decide to go bigger, then I'll almost certainly go with an outboard amp. All options are still on the table while I consider what I'm able to do.

Pioneer tech support says the continuous power output of the rear channels "combined" is 40w.

04-07-2011, 06:05 PM
In order to get decent quality bass out of a system, 60-80% of total system power will be dedicated to sub-bass. The lower you can x-over a sub the easier it is to integrate it, and that will require that you have enough power to hear a sub that's x'd over that low, and a subwoofer that will reproduce that low frequency.

04-07-2011, 06:51 PM
I agree with that. If I were to use the head unit alone, the sub would be getting about 50%. I understand that's not great, but I don't think it's all bad either if I can match the driver to the power source.

My 5yo daughter wants to send you guys some smilies. :23: :23: :aureola: :14:

Mr Peabody
04-07-2011, 07:18 PM
You might try parts sites that sell Pro audio drivers, they are typically more efficient.

04-07-2011, 07:56 PM
That's an excellent idea! Any ideas on which sites to check out?

04-10-2011, 05:06 AM
This might work for you. I have something similar ( a self powered Kenwood sub from Crutchfield ) that easily fits behind the bench seat of my Chevy standard cab S10 and it makes a huge difference.

04-14-2011, 05:20 PM
This might work for you. I have something similar ( a self powered Kenwood sub from Crutchfield ) that easily fits behind the bench seat of my Chevy standard cab S10 and it makes a huge difference.
I've wondered about those. Like I stated in an earlier post, I've been pleasently surprised by some Boss stuff, but sorely disappointed in some other Boss stuff, like decks that quit working after a few months, factory defects out of the box, etc. One subwoofer I bought, is dog-doo. You get what you pay for, but this was a ripoff at even only $30. That Boss powered sub reminds me of a seat shaker, which is no replacement for a real sub, but might be better than expecting a deck to provide good low bass.

I referred to a low profile sub last week, , and its a great deal, but its specs need to be taken with a big dollop of salt. Paired with this amp, , it romps and stomps. Once again, a grain of salt please. 2000 watts rms? ummm... I don't think so. But it is really clean sounding amp on a pair of stereo speakers, so it is good at providing clean thump. And the price is right. Hey, there's worse risks. Just don't expect to win any contests where decibles or super low sub-bass are criteria.

Mr Peabody
04-14-2011, 06:18 PM
I can believe Boss has a couple stand out pieces. I'm not sure what the story is behind these budget lines but it seems there's always an occasional piece that's an outstanding value. In the late 80's early 90's we'd pick up a line or two, always a farmer or used car dealer just wanting something to make noise to fill a hole in a vehicle for little of nothing, and in these lines there would be the amps or subs, something we could sell a load of to support the line and make it worth dealing with the defects of other areas of the line.