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Multi-Way Conventional loudspeakers with crossovers

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Old 2nd December 2012, 09:01 PM   #11
Kaspari is offline Kaspari  Netherlands
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I redesigned the box to 50L and removed the 0,33Ohm resistance on the woofer.
Then optimised for a Port tuning frequency of 32Hz. Going for 1 bass is too dull for me indeed and I wanted to beep the 2x30L response so redesigning to 50L (2x25l connected) really was the only option.
Ran it trough Boxsim and it gave me pretty much the same reponse and the new design actually hardly looks that much bigger.

I expect to spend around €70,- on crossover parts:
-Jantzen Cross-Caps
-Jantzen 1mm air coil inductors
-SupremeES resistors (they don't cost that much extra anyways).
On drivers €280,- and the Box I'll try to keep down to €300,- with a 31mm front baffle and 20mm for the rest, good birch plywood all the way. The back will be padded with a 5cm layer of wool and the front and side panels will get a layer of lead bitumen and a bit of felt around the drivers.

Which brings me to a total of around €700,- for a pair.
What do you guys think of it? Worth the trouble?

Thanks for the help, I learned a lot tonight

Last edited by Kaspari; 2nd December 2012 at 09:12 PM.
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Old 2nd December 2012, 09:45 PM   #12
system7 is offline system7  United Kingdom
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This is all looking very nice. I was looking at Troels' Vifa C17WH tower which is along the same lines.

Vifa C17WH-

He suggests some (window?) braces to break up the big panels. Port on the middle of the back in his design, as it goes. Certainly putting it near the floor boosts the bass thorough floor reinforcement, so something to ponder there. People often put some fluff in the bottom third of floorstanders to damp the long resonance.

Probably the size of your listening room is a big consideration. But you've doubtless got tone controls. Go for it!
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Old 2nd December 2012, 10:46 PM   #13
Kaspari is offline Kaspari  Netherlands
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Quote:
Originally Posted by system7 View Post
This is all looking very nice. I was looking at Troels' Vifa C17WH tower which is along the same lines.
Vifa C17WH-
He suggests some (window?) braces to break up the big panels. Port on the middle of the back in his design, as it goes. Certainly putting it near the floor boosts the bass thorough floor reinforcement, so something to ponder there. People often put some fluff in the bottom third of floorstanders to damp the long resonance.

Probably the size of your listening room is a big consideration. But you've doubtless got tone controls. Go for it!
I love Troels his website. It's such a nice one to read and you learn a bunch from him.
I have quite a big listening room so a bit of volume wouldn't hurt. I certainly won't be lacking bass with this design in my room.

I've already incorporated two window braces in my design. Here are the two versions next to each other. The left one is the 50L version, I'm glad it hardly looks much bigger as the 30L version on the right
Top Dollar VI view.png
Just for good measure, the 50L version:
Freq.
Top Dollar VI (50L parallel DIY-F) Freq res.png
Cross.
Top Dollar VI (50L parallel DIY-F) Crossover.png
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Old 3rd December 2012, 09:54 PM   #14
system7 is offline system7  United Kingdom
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Frankly, I can only encourage you to have a go at this D'Appolito design.

0.18mH or a preferred value of 0.2mH is going to make almost no difference whatsoever.

Within a couple of minutes, your ears compensate. What I do think is this is a pretty easy load for almost any transistor amp. A Riga Brio-R will have no difficulty with this.

Cabinets are an interesting detail. I currently admire the Harbeth approach.
Interesting read I found on Lossy Cabinet designs by Harbeth

Do let us know how you get on. I really ought to do some of my own stuff too. Spend FAR too much time here, and not enough time building.
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Old 4th December 2012, 01:39 AM   #15
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Originally Posted by Kaspari View Post
-I worry about impendance peaks because when you cross at that point the rising impendance will shift the crossoverpoint. Or am I mistaken?
Absolutely, the impedance of both drivers need to be relatively flat through the cross-over frequency band, perhaps with a second order cross-over network, an octave above and below the cross-over frequency. Otherwise, crossing over is going to work out badly.

So what is the cross-over frequency of your 50L design? -Easier to ask then to extrapolate from your network.

Regards,
Pete
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Old 4th December 2012, 05:17 AM   #16
system7 is offline system7  United Kingdom
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Originally Posted by cT equals piD View Post
Absolutely, the impedance of both drivers need to be relatively flat through the cross-over frequency band, perhaps with a second order cross-over network, an octave above and below the cross-over frequency. Otherwise, crossing over is going to work out badly.

So what is the cross-over frequency of your 50L design? -Easier to ask then to extrapolate from your network.

Regards,
Pete
The crossover -6dB point on the treble filter is 3kHz in post #13's frequency response plot. What's hard about that?

I don't know of a single reactive crossover that doesn't have impedance peaks. You can of course use low inductance drivers and lots of resistors and Zobel networks in a crosssover for a lower, flatter impedance as in the weird Sonus Faber Extrema loudspeaker.

This design is just a piece of pure audio nonsense, since the treble filter's series resistor soaks up huge amounts of amplifier power needlessly. I am being polite in the following post to spare someone's feelings, but I'm saying that it is a STUPID design.

Sreten & Speakerman go at series XOs
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Old 4th December 2012, 02:31 PM   #17
Kaspari is offline Kaspari  Netherlands
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Quote:
Originally Posted by cT equals piD View Post
Absolutely, the impedance of both drivers need to be relatively flat through the cross-over frequency band, perhaps with a second order cross-over network, an octave above and below the cross-over frequency. Otherwise, crossing over is going to work out badly.

So what is the cross-over frequency of your 50L design? -Easier to ask then to extrapolate from your network.

Regards,
Pete
The original XO frequency was 1800Hz but I fidgetted quite a bit by just changing values by hand and seeing the reaction or running the optimiser. I've also always learned that the imp curve has to be flat as possible in the XO region, for some reason the resonance compensation circuit I calculated had no effect, I'll redo it soon because I too don't like the peak near the XO region.
Despite what System7 says the XO isn't easily deductable because you have to first calculate the total impendance of the two drivers including the networks combined with them. It's supposed to be around 2000Hz, but I was thinking about crossing it higher anyways to make life a tiny bit easier on the tweeter, but not too far because the two midwoofers have some ugly breakups at higher frequencies that I don't want anywhere near the audible region.
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Old 4th December 2012, 08:54 PM   #18
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Originally Posted by Kaspari View Post
Despite what System7 says the XO isn't easily deductable because you have to first calculate the total impendance of the two drivers including the networks combined with them.
Assuming a parallel cross-over network, then the high-pass and low-pass sections operate in parallel circuit, that is, there is no interaction between them. That is what I think, anyway, so your above statement is puzzling to me.

Ideally, the procedure that I would follow would be:

(1) Get the impedance of the tweeter and woofer in the crossover region to be as flat as possible.

(2)If you want to put extra effort into the project to get the best results, this involves actual, physical measurement of the flattened impedance of the drivers in the cross-over region.

(3) The values of inductance and capacitance of the high- and low-pass filters then follow from the measured impedance of the drivers at the cross-over frequency, and the cross-over frequency.

Very straight-forward, I would say, or not?
Pete
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Old 4th December 2012, 09:20 PM   #19
Kaspari is offline Kaspari  Netherlands
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Originally Posted by cT equals piD View Post
Very straight-forward, I would say, or not?
Pete
Hi Pete, it is indeed.
The problem is that, eventhough I've been reading and pondering for a long time. This is my kick off project, it's not my first design, but it's the first that is buildable for moderate costs and where I'm confident enough it'll sound the way I like, or close at least. Sure I want to measure it someday. I want to go on measuring and building speakers. This one I want to simulate into "perfection" first from my comfy chair, then build it, then get the kit to measure it and in the end enjoy my speakers while I build and measure more.
I know it's best to start with good measuring kit. But the way I see it now I'd rather spend the money on actual speaker material to get going and perfect it further from there when I buy proper kit. From what I know and have read Boxsim is a complete, intuitive and quite capable program. It's not profeesional software but it gives a starter like me time and means to potter around and have some certainty once the built speaker gets measured it won't be miles off. For now that's enough for me, the box and the units won't change and trying a new, optimised, crossover later on will only make the build more rewarding in my eyes.
I have a pair of Tannoys I really like so I can patiently tune these further in the future without having to miss out on good quality music
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Old 5th December 2012, 03:08 AM   #20
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Oh, okay, I think that I understand now. You are referring to the red (impedance) trace, impedance as seen by the amplifier "looking into" the speaker system. That is, the graph of your post # 13. Assuming that you are using a solid-state amp with relatively very low source impedance, the fluctuation of that red trace isn't going to be problematic at all. That is, within a wide range of total impedance of the speaker presented to the amp, output voltage of the amp remains a constant.

Can Boxsim simulate impedance of the drivers versus frequency? Most of the time, it isn't too difficult to get DRIVER IMPEDANCE in the cross-over region fairly flat.
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