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Change FR regression line slope with crossover?

Nate R

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in 2014 I built a kit amp and a single Classix II, and put them inside an old radio cabinet as our main living room sound source. Happy enough with this, despite a bit of missing treble due to some thicker speaker grille fabric/metal grating in front of the speaker.
Now, my wife wanted to change to a different, smaller cabinet for holding our TV and audio equipment. Classix wasn't going to fit....needed smaller drivers. So, I built a pair of Carmody S2000s. I'm using them inside an old phonograph cabinet behind the original speaker grille. (SAF and all.)... our TV sits on top of this cabinet.

After listening some... I then stuffed the ports and that improved the boominess....I was getting some resonance/noise from within the phonograph box from the rear facing port firing into it, I think. That helped a fair amount, but I'm still not thrilled. I find I'm not really into the voicing of these so far. Felt that way from the second I fired one up in open air. (it's not just the box they're in.)

I will be adding a sub elsewhere in the room to handle the lowest ends...but since I've spent the money on these drivers, and they fit the cabinet opening I have...I'd like to try and salvage them/change them to my liking.


From Amir's measurements, it was noted these have a fair amount of down slope:

index.php


If I take some old Minimus 7s and put them in the same positions in the cabinet, I find I like the response better (except for the missing bass on those.. more than I'd like the sub to make up for...) Which have flat or even upward response curve. So I think that's more the sound I prefer.

Is this something I can change within the crossover? Like, can I make these flatter, like the C-Notes, the Zaph 5.2s, or the Minimus 7s? Or is this impossible with no audio measuring equipment, and I need to buy some C-notes and figure out how to make them work in this cabinet, or Overnight Sensations or something else? (The S2000 uses the same cabinet as the OS)

I'm willing to make a new cabinet to better fit this space with a downward firing port if needed, or front facing ports might work, or possibly sealed....... But that still won't help the downward regression to higher frequencies. I'd rather spend some DIY time vs more money on different speakers....But if I'm chasing my tail I'll bite the bullet and get something else (like the OS, C-Notes, Zaph, etc)

Knowns: I know the tweeter used in this kit (a Wavecor). I know the values of the crossover components and can figure out the circuit. (Like, there's an L-pad setup with a 5.1 ohm resistor in series with the tweeter, and a 15 ohm in parallel)... So I assume that I CAN brighten the tweeter response..but I get the impression that inductors, capacitors, and how they interact with resistors and the drivers can shift the whole slope/curve? As in, I don't think I should just change the 5 ohm resistor with like a 1 ohm and call it a day? (There's an inductor across the tweeter leads that I think shifts things, too?)
Also, the woofer is DIYSGs/Denovo's own making, so I can't find/measure/get T/S parameters for it. Does that matter if I have a known crossover design, with a known response?

I just don't have any experience yet with crossover design, etc.... looking for some advice on whether the slope of the curve can be changed, and how I go about analyzing the current crossover and what values/components to look at changing to get the result I want. I played around a bit with Xsim, but it gets messy w/o parameters to import.

Thoughts?

Thanks for your time!
-Nate R
 

Rick Sykora

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no eq or tone controls?
 

DVDdoug

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As in, I don't think I should just change the 5 ohm resistor with like a 1 ohm and call it a day?
I'd just try bypassing the resistor altogether (shorting across it) with a clip-on test-lead. If that works you can permanently bypass it or if it's too bright you can try a different resistor. It's probably not worth trying to make it perfect but maybe you can make it sound better to your ear.

If it was me I wouldn't attempt any more re-design of the crossover beyond that. If I wanted to go further I'd probably convert the speaker to active and bi-amplified. You can do a lot more with active crossovers & filters, and it's easier to modify & tweak. Or you can do even more if you wanted to use DSP.

Also, the woofer is DIYSGs/Denovo's own making, so I can't find/measure/get T/S parameters for it.
There's a gizmo for that, if you think it's worth it.

Does that matter if I have a known crossover design, with a known response?
The box/port tuning is below the crossover frequency so it's a separate issue.
 

Rick Sykora

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Will add my usual for those who aren't experienced with crossover design, could ask the designer.

Carmody is not here (AFAIK) but has an account on the PE forum.
 
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Nate R

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no eq or tone controls?
Will add my usual for those who aren't experienced with crossover design, could ask the designer


Fair points....I'm doing this on the cheap-ish... So running an all-in-one Fosi DA2120C... so tone control exists but is extremely limited. I would have looked at the MX3S, but reports of that amplifier chip having problems with some crossovers (like OS) made me leery to find something with a different chip. But either way, an all in one makes DSP or EQ difficult.

Carmody's site is specific about contacting him and that he can't do custom stuff time wise these days...but maybe I'll see if he wants to discuss on the PE forums...

As I play with Xsim on the tweeter....noting the crossover is around 2500 hz......I see that the woofer has that downslope, too. There's an inductor in series and a capacitor parallel to the woofer..... I'm reading that this will act as a notch filter.... So I guess I need to model a similar woofer to see how to alter that, too.
 

Rick Sykora

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While still do have s2000s around, am less inclined to try to redesign them when the designer is active. Have enough other plans of my own queued up (notably when eq might be sufficient).;)
 
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