Extremis crossover help please

[Grahamt]

Hello,

I would really like to do a 2 way monitor with the Adire Extremis6 and the Hi Vi TN28. Why the TN28 you ask? Well, it is cheap, available, people seem to like it, and it looks great. Also, to be honest, I blew most of my budget on the Extremi (is that plural?). I will try to explain my logic and hopefully people can explain where I have made mistakes, and make other suggestions.

Speakers are one of my main hobbies and I have been reading about speaker design for about 1 1/2 years, books by Dickason, Murphy, Weems and many websites. Just enough to be dangerous. I have built a few subs and speakers and have no problem soldering and want to try to design my own, hopefully with some valuble input from members here. I am well aware that going with a tried and true design will ensure better results, but I want to throw caution to the wind. My goal is to build a pair of speakers with better detail, clarity and output than my Paradigm Mini Monitors. If these are even 10% better, I will be blown away.

Well here it is


Crossover: I have picked 3 kHz because the impedance of both drivers seems to be pretty steady there, and there is some break up in the response on the Extremis just above that which I hope to avoid with a steep slope. Also, I want to keep things simple and avoid impedance compensation for resonance and rising inductance.

I have chosen the 4th order LR because there will be very little overlap, and it seems to be a good choice for attenuation, driver offset, lobing etc. ie forgiving.

I used the dreaded textbook formulas to design the crossover. It looks to me that the impedance of the Extremis is about 17 ohms at 3 kHz and the TN28 is a steady 6 ohms. These were my R values. Please correct me if I am wrong.

Baffle Step Loss: I would like to compensate for about 3 dB of loss, not the full 6. I calculated the F3 to be about 500Hz for a baffle that is about 10" wide. I made the first inductor on the lowpass kick in at 500 Hz. I could be wrong but that will be a 3dB attenuation, right?

Lpad: so with the BSC, my midrange is down 3dB so I want to bring my tweeter down an extra 3 dB, for a total of 6dB.
BTW, the Extremis is 86dB and the Hi Vi is 88dB, both at 2.81v.

Here are the links for the Extremis and Hi Vi tn28.
http://www.adireaudio.com/TextPages/...eFrameText.htm
http://www.partsexpress.com/pdf/297-409.pdf

I know that improvements can be made by measuring and tweaking, but is this a good starting point?

Thanks for the help in advance,
Graham

[Shaun]

Hi, Grahamt

Is this your first loudspeaker crossover design? I would not recommend using the method you seem to be wanting to use, especially considering the level of performance you're aiming for. I'd recommend downloading Speaker Workshop (speakerworkshop.com), and building a home measurement system. This way, you'll be designing (the crossover) for the system as-is, not theoretically (which is really the painful way to go).

Hope this helps.

[Grahamt]

Hi Shaun,

Yes, my first attempt at design. I have Speaker Workshop but found it to be intimidating, and forgot about it. I just found Jay Butterman's tutorial on SW so I will give that a read through. Thanks for the advice. I know that I have a lot to learn about design, and this is a long term hobby for me. I thought that this way would be easier than learning how to use SW but I will give it another shot.
Thanks for the advice,
Graham

[Grahamt]

After browsing through the tutorial I have come to the conclusion that I do not have enough time to devote to this project at this time. This is a long term hobby as I said before, and will pick it up again later when I can afford the time and measuring equipment. I suppose my only option is to wait until someone comes up with a design for the Extremis. Hopefully with a tweeter I can afford (XT25 is about the limit). Adire will be using a tweeter out of my league (Hiquphon, Morel etc).