Will this Crossover work?

[farmerjack61]

I need help, professional help!!!

Greetings from Tasmania, Australia, where most sane people buy their speakers!


Once again I find myself doing things back to front. This is what happens when you live down under!

• I purchased a nice subbie (12" Venom) from ebay. (That's how this epic started).
• I really liked the thumping shockwaves that came out of it, so I got another one - they were new and only cost me $40ea + $15 postage.
• When I looked at them sitting on my carpet, I suddenly realised that I would have to build a box for them.
• I want a pair of low impedance, high power, full - range speaker boxes to match the rest of my surround speakers.
• I decided to buy four 6.5 inch DME Woofer/Mids (N178CS) which are a favourite of mine - yep, once again, they're cheap, with solid construction and a wonderfully satisfying sound. I realise they can only handle 50W RMS, so I intend to paralell two for each box's midrange section. I know they work really well between 100Hz right through to 5kHz at a good volume level.
• Finally I decided on a pair of nice looking silk dome tweeters from Altronics (C2003) they are rated at 80W RMS with a frequency response of something like 2k - 20k.

OK, that's the shopping done. Here are my thoughts - so far.

1. My amp has an output limited to about 120W RMS.
2. Two 6.5" fifty watt mids will handle 100 watts in paralell?
3. The tweeter will remain intact even though it's rated at 80 watts because I am only using it from 5kHz and over??
4. I will need to build a box inside the box to stop the subbie from pumping that pair of mids?

Now, here's the deal $$$.

Take a look at the schematic that I will attach or post and tell me what the impedance of my speaker box will be. Have I got it all rong? I am aiming for 3-6 ohms. My father says I have only enough electrical knowledge to make my work dangerous, is he right? Will she blow? I am a wood machinist after all.

I will pay $5ea. (into the DIY kitty) for the first two sensible suggestions, advice or ideas . Tossing the speakers out and starting again is not an option.

I will also pay $10 for a (really) funny audio anecdote.

Here's a snap of the proposed crossover:

PS. I don't know anything about HTML so if the picture or link doesn't appear on this post please get back to me and I will try again.

Cheers and bye for now, Phil Elliott

[Inductor]

first question: why are you placing the woof in series with the mids?
second question: can your amp handle the low impedance from the parallel mids?

[farmerjack61]

Hello inductor.

In reply to your first question "Why place mids and woofer in series?"
The simplest explanation I can give is that; "Due to the number of speakers inside the box and their individual impedance, something has to be placed in series with another section in order to get the stated parameter of 3-6 ohms overall average box impedance (the mean average of measurements made all along the audio spectrum). I tried (on paper at least), a series connection between woofer and tweeter but this gave me a figure of around 3 ohms which is getting (almost) too low.

To your second question; If my amp frazzles at 4 ohms (a minimum of 4 ohm - remember that the rest of the spectrum will be higher than 4 ohms impedance), I will send it back to the manufacturer and ask them to take another look at their design. To sum up what I have stumbled through here;
YES I am very confident that my old Sony amp will cut the mustard.

Thankyou inductor for your questions and observations, there are plenty of mugs out there that don't know the difference between series and paralell crossovers and I am only new to the concept of series crossovers. This is why I have posed the question; "Will it work?" I am still not sure if it will work and may just have to try it out and see.

Sincerely, Phil

[wolf_teeth]

Read Paul's FAQ's:

undefinition

That will help you immensely.
Wolf

[PeteMcK]

Zobels are unnecessary on the Sub & Tweeter (& IMO on the mids, but it'll make it easier for a beginner...)
Do you have parameters for the DME Woofer/Mids (N178CS) ? I'm thinking that a 2.5 way would be the best way to go for this combination of drivers.

[Cal Weldon]

Originally Posted by PeteMcK

I'm thinking that a 2.5 way would be the best way to go for this combination of drivers.

Agreed 100%. Farmerjack, a 2.5 way is a system that will utilize a box for each woofer and and a box for each 2 way that you will build from the mid bass and tweeters. You will require a plate amp for each of the woofers or you have the option of getting a more powerful plate amp and putting the two woofers in one box. Then the mid/high boxes can be placed more where you like as they are smaller and the (one or two) woofer(s) can be put out of the way. This is assuming you have a WAF to consider and that you would like to have this less conspicuous than perhaps when you were a young'n. Are you with us so far?

[PeteMcK]

actually Cal, I wasn't thinking of bi-amping, but that's always a good option....
cheers,

[Cal Weldon]

I hardly think it's an option with a less than 85dB sensitivity of the woofer, 90 for the mid bass and one would assume around 93 for the tweeter. I can't find that exact model but this may be the one to which Farmerjack refers., the 3004 rather than the 2003?

Altronics - Your One Stop Audio Visual & Electronics Supplier

Doing it this way will save you a lot of headaches with the XO.

[PeteMcK]

Cal, Re: 'less than 85dB sensitivity of the woofer' - good point...
A classic mistake that most newbs make, attempting to buy a bunch of drivers & stick them in a box.... the importance of the relative sensitivites of the drivers is vastly underestimated, if taken into consideration at all...

[PeteMcK]

DME parameters here: DME Audio
In Unibox they look like a pair of these will get down to ~50Hz in a ~50L ported box;