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OK, so I'm thinkin' about building a low-cost tower setup for my HT. I can get the crossover built once I get a design for it so I don't need to buy those prefab ones from PE. So...first things first, I think I'm going to use (2) of these per tower to start with since I already have 4 sitting around unused - http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=290-308
And I have absolutely no idea what tweeters to get - please give recommendations of no more than $20 each. I did find some cheap ones from a good company (Audax) but they're only 3/8", is this a bad size for a tweet? Here's the link to them - http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=276-025&scqty=2
Whatever I get will be powered by a JVC 5.1 receiver putting out 100w x 2 @ 6ohms so I figured it would wire up like this: (2) 4 ohm mids = 8ohms 8 ohm midbass and tweeter = 4ohms 8 ohm + 4 ohm in parallel = 6 ohms
And in the future if I wanted to upgrade the mids I could get 8 ohm mids wired in parallel to 4ohms and end up at 8ohms instead of 6 - still a good match.
I'd like it to give a more room-filling sound when cranked up pretty high (compared to my Infinity Entra One bookshelf speakers with single 6.5" mids) - would 5-6" PA speakers be a good choice because of this? And although I don't want to spend this much I am considering 2 of these (one per tower) for the midbass (x'd over so it doesn't produce any vocals) drivers - http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-366 Are they as good as they look? Cause they look like they were built with nothing but SQ in mind... Also, about how much can I expect to spend on crossover parts once I get a design?
Posts: 537 | From: Canada | Registered: Oct 2003
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quote:Originally posted by kevox: so I figured it would wire up like this: (2) 4 ohm mids = 8ohms 8 ohm midbass and tweeter = 4ohms 8 ohm + 4 ohm in parallel = 6 ohms
I'll be honest, I didn't read the entire post (I suffer from A.D.D.), but the above doesn't work out.
The midbass and the tweeter won't be playing the same frequency range, so the overall impedeance the receiver sees won't be lowered even though you series the 8 ohm midbass and the 4 ohm tweeter. Assuming your points are 50-3000hz for the midbass and 3,000 and up for the tweeter, the receiver will see 8 ohms from 50-3000hz and 4 ohm from 3,000 and up.
quote:Originally posted by kevox: so I figured it would wire up like this: (2) 4 ohm mids = 8ohms 8 ohm midbass and tweeter = 4ohms 8 ohm + 4 ohm in parallel = 6 ohms
The midbass and the tweeter won't be playing the same frequency range, so the overall impedeance the receiver sees won't be lowered even though you series the 8 ohm midbass and the 4 ohm tweeter. Assuming your points are 50-3000hz for the midbass and 3,000 and up for the tweeter, the receiver will see 8 ohms from 50-3000hz and 4 ohm from 3,000 and up.
I was thinking the midbass would be more like 45-200hz or somethin lol. With the midrange woofers taking over the rest to produce the vocals...
Also, both the tweeter and the midbass are 8 ohm drivers - so I figured if I paralleled them to 4ohms and then paralleled that with the 8ohms I'd get from the 2 mids I'd end up at 6 ohms.
I'm not concerned with impedance rise and all that stuff - it's gonna do what it's gonna do so all I can do is design it to work at the optimal impedance of 6 ohms.
Posts: 537 | From: Canada | Registered: Oct 2003
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quote:Originally posted by kevox: I was thinking the midbass would be more like 45-200hz or somethin lol. With the midrange woofers taking over the rest to produce the vocals...
Whatever, my numbers were just as an example
quote:Originally posted by kevox: Also, both the tweeter and the midbass are 8 ohm drivers - so I figured if I paralleled them to 4ohms
This is where the problem is. Unless the tweeter and the midbass are playing the exact same frequency range, you won't get to 4 ohms. The only time parrellel or series wiring effects the impedeance (as between two speakers) is in the frequency range shared by the two speakers. So in your example (and these numbers are just pulled from my ass), if the midbass is playing 45hz to 250 hz and the tweeter is playing 3000hz and up. You parrellel those two speakers, the receiver "sees" 8 ohms from 45hz to 250hz and sees 8 ohms from 3000hz and up. It never "sees" 4 ohms.
If you parrelled your midbass and midrange driver (again assuming 8 ohm speakers). Assume frequency range 45hz to 250hz for midbass and 250hz to 3000hz for midrange. The receiver "sees" 8 ohms from 45hz to 250hz. From 250hz to 3000hz it "sees" 8 ohms. The only exception to this is because of the slope of the crossover (but that doesn't matter for this discussion).
quote:Originally posted by kevox: and then paralleled that with the 8ohms I'd get from the 2 mids I'd end up at 6 ohms.
See above.
quote:Originally posted by kevox: I'm not concerned with impedance rise and all that stuff - it's gonna do what it's gonna do so all I can do is design it to work at the optimal impedance of 6 ohms.
What I'm talking about has nothing to do with the rise a speaker sees in a box, after use when the voice coil heats up. I'm talking about a fundamental flaw in your wiring. Although, if you don't take these things into account---you could have some negative results.
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Oh I see, so the parallel/series wiring method really only works properly (or at least in the traditional way) when 2+ of the same woofers are used? Like 2 tweeters, 4 tweeters, 2 mids, 2 midbass's, etc.
Hmm, well then if the tweeter and midbass wont wire down to 4 ohms - what can I expect? It sounds like the midbass would still get its normal amount of power from the receiver but just that the tweeter wouldn't get the same amount of power cause it'd have a higher impedance?
I really don't mind if my tweeters don't see much power lol - they're tweets.
Would the overall impedance (that I thought was going to be 6 ohms) likely be above or below 6 ohms?
Posts: 537 | From: Canada | Registered: Oct 2003
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Those midbasses will play up high enough for you to cross them with a decent tweet. Look for a somewhat larger textile dome as some of the larger ones (i.e. 1 1/8") cross over very well at around 2.5k, which is what I would recommend given those woofers.
And I think your conception of impedence and wiring is still confused.
You WILL need a crossover network for these to work right. You want to match the impedence of the drivers (i.e. woofers 8 ohm, tweeter 8 ohm) for the most part. You cant just wire a 4 ohm woofer and 8 ohm tweeter and get a 6 ohm load. Thats just silly.
quote:Originally posted by JeremyD: You WILL need a crossover network for these to work right.
I know that; where did I say I wasn't intending to get one? The most I said was that I wouldn't need the Bandpass Xover to give my mids a HP.
But anyway it doesn't matter cause I'm definitely not doing it now...since my 15w6 is useless (never even got to use it ) I am saving up for an SE15 and that is gonna take quite some time so I'm not gonna waste $100+ on a tower speaker. thanks for the help though.
Posts: 537 | From: Canada | Registered: Oct 2003
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