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Old 18th October 2008, 01:54 AM   #11
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The HiVi and TB look ok. Lower efficiency could work well if you use the woofers higher spl to get some baffle step compensation. Just to pad down the tweeter to match.

Power handling matters, but it's proportional. Half of the total power consumed is below 350Hz.
More important question is how powerful is the amp you have to drive these?
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Old 18th October 2008, 03:10 AM   #12
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It'd be a Harmon Kardon HK3490.

120w x2 channels.

Here's a link.
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Old 18th October 2008, 03:45 AM   #13
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Here's a much better midrange for about the same price: Vifa P13
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Old 19th October 2008, 04:32 AM   #14
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Default Parts list....final i hope!

Alright, I'm going to take your advice on the mid there and stick with the original tweeter/woofer.

That means the final list will be

1. Tweeter
2. Mid (Vifa P13)
3. Woofer

Now, taking from your other posts, I should have a crossover point at 300 hz. for the woofer. I'm not sure how exactly you figured that out. Could you explain more?

Should the Tweeter cross over somewhere at 4000 hz? Is there overlap between the drivers that we're looking to get? Or is it driver dependent the amount of overlap?

Another question. What do the "orders" mean in the different types of crossovers... IE 1st order butterworth, 2nd order etc.... Should I choose one of these specifically, or is it a matter of personal preference?

Thanks for all the help, I hope I've not been to much of a pain with all these questions.
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Old 19th October 2008, 04:59 AM   #15
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Well, looking at the response graph is semi-helpful, but these are usually not very accurate. I based that more on baffle step (look this up) where I'd assume for a 12" driver, you'd have a 15" wide baffle. This would correspond to ~300Hz baffle step.

Your mid-high crossover point for these drivers can be as high as 4K, but you may want to go a bit lower although I don't think I would.

Orders are the amount of attenuation per octave - 6db/octave, 12db/octave and so on. Butterworth, Bessel, Linkwitz Riley are alignments or types of crossover filters. Selection of the type and slope (order) is determined by the individual response of each driver and their combined response. This bears reading up on but like anything else in the realm of audio, the more you learn, the more ignorant you know you are. Generally, you can expect reasonable results from second order butterworth filters for these drivers.

Here's some light reading:
Baffle step

Here's a handy crossover calculator
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Old 19th October 2008, 03:48 PM   #16
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Default calculations.

Alright, now that i've got finalized parts, I put in the values for a crossover with your crossover calculator link. I may have input them wrong but here's what it spit out and what I put in to figure those things out.

Inputs: High pass impedance: 4 ohms
Low pass impedance: 8 ohms
Frequency: 300 Hz.

The outputs then were as follows.

C1: 93.75F
L1: 3.001333333333333mH

C2: 46.875F
L2: 6.002666666666666mH

Am I correct in that the "C1, C2" are referring to capacitors, and the "L1,L2" to inductors?

I wasn't sure if I should have input the frequency range of the woofer crossover (300 hz, like you suggested), that's where I thought I went wrong. And I may not have, I just don't know. Also it was only a 2-way crossover...is that the correct application for the 3-way speaker?

I downloaded Unibox and I have a few questions on how to use it.

Should I take the values for the woofer, tweeter and mid and add them to the Unibox database? Or should I only add one of them to the database?

Under Drive Unit configuration, should I select 3 drive unites in series or parallel? The program isn't very clear on some things, I don't exactly know where to start.
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Old 19th October 2008, 06:10 PM   #17
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The other poster said that he expected a lot of "don't do this" posts, but so far there aren't any. So here goes.

Designing a three way speaker (especially one that sounds good) is no small task for those with experience designing XOs and the tools and software to measure your own drivers frequency response in your enclosures. It sounds like you may be lacking on both of these counts. You will get much better results building an established design done by someone with the tools and design experience to get it right.

Second, XO calculuators like you linked to just don't work very well. They assume a resistive load instead of a loudspeaker which has a reactive load (changes with frequency). Not to mention that they don't take into account the drivers frequency response.

Here is the frequency response of a three way center channel design I did recently with well behaved paper drivers in red. Those same drivers with textbook values like the ones you were linking to are in blue. As you can see the frequency response of the textbook values system is terrible.

Click the image to open in full size.

If you want to take up this hobby, start buying some books, software, tools etc as it is a great hobby. On the other hand, if you just want to build a speaker or two, you will be much better off using someone elses design.

Good luck,

Regards,

Dennis

PS Unibox is just for simulating the woofer or mid low frequency response in a box. It has nothing to do with XOs or tweeters
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Old 19th October 2008, 06:57 PM   #18
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Default Re: calculations.

Quote:
Originally posted by N10


Under Drive Unit configuration, should I select 3 drive unites in series or parallel? The program isn't very clear on some things, I don't exactly know where to start.

First I need to apologize.I didn't notice that the tweeter is 4 ohm and you should think about getting an 8 ohm one.

Second, what are your expectations for this design? Like anything else, the more you know the better the results will be. As mentioned above, designing a good three way is not an easy task even for those that are well versed on this. You are starting to learn, so don't expect a masterpiece the first time. As for the established designs, you learn very little from doing one, you just end up with a facsimile of someone else's work. Will it sound good? Will it sound good to you?

On with the show.
You can do a pretty serviceable job with that calculator. No, it won't be perfect, but it will be a good start. You need to set 2 crossover points. One at 300 and one at 4k. The midrange will have a high-pass filter(above 300) and a low-pass filter(below 4k). The tweeter will have a high-pass only (4k) and the woofer will have a low-pass only(300).

Unibox will model the enclosure for the bass driver. That is it's purpose and it doesn't really handle the other two (although you could model an enclosure for the mid with it).
I will try to find time later to demonstrate it a bit.
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Old 19th October 2008, 11:51 PM   #19
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Unibox.
First after you open the file is to enter the T/S specs of the bass driver you want to make a box for.
Resonant frequency - Fs, voice coil resistance - re, mechanical and electrical Q of the driver - Qms & Qes, cone area- Sd, equivalent volume of air that equals the suspension stiffness - VAS and linear excursion - Xmax.
I have put in the specs for the woofer you selected. In the middle column, you'll see some of the calculations that Unibox has done based on the T/S specs.
On the right you set the drive unit config box to single drive unit for a box with one woofer.
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Old 20th October 2008, 12:00 AM   #20
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Here is an example of a vented box for this woofer. Box volume is 100 litres or about 3.6 cubic feet. This is a fairly large box, but it is nearly ideal for this driver. Response goes down to ~30Hz.

The vent would be a 4" pipe about 10" long.

This will easily handle the 120 watts that your receiver has without running out of Xmax - the cone movement is within it's normal range of back and forth motion.
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