Crossover help/advice

[Owen Bartley]

I have decided to build a pair of switchable bi/dipolar rear surrounds, originally created (I think) by Dan Brown here. I plan on modifying them slightly to delete one of the woofers, making it a TWT type design, and just wanted to know;
a) if I should absolutely change the crossover to make up for the woofer I'm removing, and
b) what exactly I should change.

His site seems to not be the most stable, so I'll post some more info and an image of his crossover. The original design uses 2 of the Dayton DC160-8 paper cone 6 1/2" woofer and 2 of the Dayton DC28F-8 silk dome tweeters. His design has the 2 woofers facing the front (direct radiating) and 1 tweeter on each side (the tweeters have a DPDT switch wired between them to select bi or di operation).

I'll be changing the size of the cabinet (reducing), removing one woofer, and keeping the rest mostly the same, so how much should I worry about changing the crossover? The only thing I could really think was that the impedance would be off. This was chosen to be a budget project, and one to get some hands on experience and practice speaker and crossover building, since I've only done a sub before. If they work out, great, if not, I can put them into the system of a less critical friend. Any help from the pros would be very much appreciated.

Edit to include crossover parts list:
C1 (027-430, Dayton MPP)
C2 (027-420, Dayton MPP)
Ce (027-358, Non-Polarized Electrolytic)
L1 (266-806, 18 ga. AirCore)
L2 (266-816, 18 ga. Air Core)
Req (016-6, 10W)*
Rs (016-2, 10W)
Rp (016-12, 10W)

[Dennis H]

You could do it but you'd have to completely redesign the crossover starting from scratch. Two woofers in parallel play twice as loud as one so removing one of them isn't trivial. I doubt that anyone here has measurement files for those drivers on that sort of box with side-firing tweeters so we probably won't be much help.

[morbo]

Dennis is right, complete redesign. Your best bet would be to email Dan and ask him if its even workable with one woofer, from there maybe he won't mind revisiting his original measurements and remodelling with one woofer for you. Otherwise there's not going to be much folks here can do to help, short of building a prototype, measuring it, and doing a fresh xo, essentially starting from scratch.

[Owen Bartley]

Thanks guys. It really wasn't what I wanted to hear, but I'm better off knowing before I start to order parts. I did email Dan and haven't heard back from him, which is why I thought I'd try here, since there are a lot of people who really know their crossovers.

I guess another option would be to use all the drivers, but in a more standard surround configuration, with either: A) a woofer and a tweeter on each opposing side, or B) for corner placement, a woofer and tweeter on the front, and a woofer and tweeter on one side. Would those changes still require a redesign of the crossover?

[morbo]

I guess another option would be to use all the drivers, but in a more standard surround configuration, with either: A) a woofer and a tweeter on each opposing side, or B) for corner placement, a woofer and tweeter on the front, and a woofer and tweeter on one side. Would those changes still require a redesign of the crossover?

Yup - I think moving any driver onto a different 'face' will mess with the phase - a lot. I guess the obvious question is, if you're ok with using all the drivers anyway, why not just build it as designed? If you read the page explaining the design, quite a bit of thought went into it, its not just setup that way arbitrarily...

[Owen Bartley]

that's true, I just didn't want something so big. I may have to go with the original design if there's no relatively simple way to modify it though.

[morbo]

Yeah, I hear ya on that. I've considered the same design, and discarded for the same reason, plus, its a bit pricey all told. But its one of the few well-thought out non-monopole surrounds out there. FWIW check out this one too:

http://www.gr-research.com/kits/av1rs.shtm

[Owen Bartley]

Thanks Morbo, that must be a good speaker, 'cause a few people pointed me towards it in another forum too. I just don't think it would work in my room... I don't really have the ability to wall mount, and I was hoping for something more stand-friendly. I really liked the idea of a combination of direct radiated and reflected sound, but unless I start a design from scratch it isn't seeming likely.

It looks like I'll just have to keep looking, and maybe just save the cash for this project and put it in my power amp fund.

[Owen Bartley]

New plan. I was reading ahead in the LDC and I stumbled across this one of the sample projects, using this woofer and 2 of this tweeter. Has anyone built these? Any thoghts?

[Brian Bunge]

Owen,

See my response in your thread on HTS.

[Owen Bartley]

^^ Thanks Brian.

I am 90% committed to building this project, but I'm hung up on my crossover parts selection. I've been looking around the PE website and have absolutely no idea which type of caps, resistors, and inductors to choose. I thought the following:

Capacitors: Dayton Metallized Polypropylene 4uF, 8.2uF, 15uF
Resistors: Dayton 10w Non-Inductive 1, 2, 4 ohm
Inductors: Erse 18g Perfect Layer Air Core 0.2mH, 2mH

Does that seem reasonable? I tried to stay away from the cheapest stuff, and the really expensive ones. Keep in mind this isn't for a serious monitor speaker, it's my first attempt at a rear surround.

While I'm at it, what's the general method for hooking everything up to the finished crossover? Should I get some kind of terminals to go on the boards, or can I just run a wire from the input cup to the first component? Should I be using solid wire to connect from XO to XO and from the XO to the speakers, or is stranded (speaker) wire more suitable?

There is a lot more going on behind the scenes than I thought!