Subwoofer Hookup Advice

Thanks guys....some really good info coming out here...I am learning heaps!

One other question I have is about the bridging of the 2 channel amp....If my understanding is correct, the L+R inputs are "mixed" (don't know if this is correct term) into one amplified mono output....does this result in any lack of sound quality?  Is this the preferred way of running an amp, or is it "pushing" the amp too much?  My system is still sitting in boxes ready to go into the car, so I am open to any and all suggestions....I am not going for loud SPL, just a nice sounding, good SQ type setup.....

Yes, the channels are added one to the other, for a mono signal.  But if it affected sound quality in any way, you wouldn't have gotten a go-ahead to bridge the subs that way from us.  We already answered the questions here in previous posts.  Remember, the load on the amp is the same both ways, and the output to the subs is the same, too.

Now, what about your sub enclosures?  Are you going to build them? That would be preferred.

Thanks stevdart...

Ideally I would like to build the enclosures myself...I need to do some reading about the subject as I don't really know what the best design is and how best to build an enclosure...

The subs specs call for a 0.5cubic ft sealed enclosure, so that is what I will be aiming for.......I have seen some installs where the subs cone is facing and firing inside an enclosure and the back of the sub is open and exposed and I like the look of that.... so, would a 0.5cubic ft enclosure be OK for doing that type of install, or do you need a bigger/samller/different enclosure if installing the subs like that?   What are the pro's/cons of running subs like that as opposed to conventionally (with the back of the sub inside an enclosure)?

You can run the sub either way in this case. It is all determined by the net volume of the enclosure. If the box volume is .5 cu.ft. net internal volume, then you need to add the space that the driver takes up to this volume. (the driver occupies a volume of air) Let's say that the sub displaces .12 cu.ft of airspace, the gross volume of the box would now be .62 cu.ft. internal, less the sub mounted conventionally of .12 cu.ft, leaving a net volume of .5 cu.ft. internal.

You can choose to mount the sub either way, there is little to no sound difference that you will ever hear. One of the potential pitfalls to this type of mounting system is if you are going to carry objects in the trunk, if they are not secured they can hit against the sub and break of the speaker wires and or the speaker wire terminals.

If this is for a sealed box, you can be out by a country mile on air volume before it will adversly affect how the subwoofer is going to perform. A sealed box is very forgiving in how it operates. Try it both ways if you like to see if you can hear any difference. There is a great enclosure volume calculator on this site. Play around with it and see how changing the measurements change the overall volume.

When I see inverted subs I smell SPL.  Seeing the cone indicates SQ.  But that's just me.  Here's the sub manual.  Those are some nice subs, and I see they are rated at 450 watts RMS.  But should do fine with 300W each.  There is a model of a sealed enclosure in the manual.  It looks as though Boston is allowing for the displacement of the speaker when they indicate building a .5 ft^3 (internal dimensions) box.  They show  a box at 7.5" X 11" X 11", which comes out to 0.525 ft^3.  The dispacement of that sub must be close to .12, which is much more than the overage in the model indicates ( 0.025 ).  So the actual air volume after the sub is mounted will actually be less than 0.5.  I don't see anywhere in this manual where they provide the displacement of the sub.  I take that, along with their statement "Eclosure measurements are internal and include basket displacement" to mean that the box at 0.5 is what you build it at, not what's left after the sub is mounted.  If you have the right room, you might just build the boxes as shown in the model.  If they are going to be shaped differently, just design the box so that the volume of the inside come out the same as the model.

You have to know what the dispacement of the basket is, along with the volume of the cone area, to invert the sub and still have the proper air space.  The basket will be outside the box, as well as the area inside the cone.  So the remaining amount of air space has to be lessened to compensate.  As for sound quality, there should be no difference in the two mounting types as long as the air space in the box is proper for each way.

Cool, thanks for that....

I actually will have this install going into a 1969 beetle, (where the back seat used to be), so will have heaps of room to utilise.....

I want to do something a little different than just a square or wedge shaped box, so was thinking of doing a Fibreglass enclosure, building some MDF sub rings, and strectching some grill cloth into a nice contoured shape along the back firewall and sides of the back seat area...one sub either side....kinda hard to imagine without a pic if you are not familar with beetles :)  Keeping that in mind, is the internal shape of the enclosure super important?  eg; if I do build a FG enclosure with an irregular shaped internal airspace, and the intenal volume of the enclosure is 0.5cft, would that work OK?

I guess doing that, the only hard thing would actually be working out the internal volume of the enclosure.....