Seas CA15RLY X2 cabinet volume suggestions

[system7]

Interestingly Steve, this crossover works really well! I have pulled the upper mid on the Audax woofer down by using 22uf as the shunt. Not hot on the midrange at all, no listener fatigue, at all! If there's one thing I hate, it's that.

But yes, I know, this was originally an MT xover and not an MTM

That's why I "was" considering using the 12ga 1.5mh I have on hand. I paid good money for them and it sucks to have them sitting in a cardboard box in the basement. However, if it simply refuses to work, I have a couple of 1mh tape coils but they're only 16ga. I could try your notch and see how that works too. It's not expensive.

I noticed you're using an 8 ohm visaton. Lojzek helped me out with this crossover solution for the tweet but it's a 6 ohm crossover. Aren't these 2 ohms difference imperative? I would think this changes the game, completely.

The 1 ohm resistor before the bass drivers... what is its purpose?

I still think 1mH is about right, and 1.5mH or 2.5mH is going to sound bassy, but it's your speaker. What's wrong with tape coils?

The 1 ohm resistor is just to separate the two basses in the modelling, otherwise we forget it's an MTM.

8 ohm nominal is 6 ohms DCR usually. I use modelling like this to get a rough idea what is going on.

Because it's fresh in my mind, here's Lynn Olson's Ariel MTM. A good design.
The Ariel, Part II

They all start to look the same after a while, eh? How hard can it be? 😀

 

[ShaneF]

Nothing wrong with tape coils! They're nice but a lot more money for limited returns. And yeah, I forgot to take in to account the actual resistance being at about 6, anyway.

Let me ask this, then: the 1mh I have is only 16ga. If I were to bump that up to 14ga or 12ga, what sonic affects can I expect? I know that the resistance changes the higher the gauge. See, the thing I don't get is the whole "fire hose in to a garden house" trick. People spend a Princess' dowry on speaker wire the size of their calf muscle but if they were to open the cabinet of a store-bought loudspeaker, low and behold, there's wire in there that you wouldn't feel safe wiring up a light bulb with!

 

[system7]

I usually measure components, if only because they are often incorrectly labelled. Resistive DCR of coils is inaudible, but might affect the bass damping slightly. After all, you've got 6 ohms resistance in the speaker, is 0.3R going to matter?

And work with what I have. A 4.7uF and a 5uF capacitor aren't really going to sound much different.

In fact 4.7uF and 0.2mH tweeter filter works much the same as 3.3uF and 0.3mH in practise. You keep the product constant for the quick conversion.

In other words, I don't fret about tiny changes. A 10% component change produces a 5% effect. It's a square root thing in an LC filter.

 

[Lojzek]

That's why I "was" considering using the 12ga 1.5mh I have on hand.
I paid good money for them and it sucks to have them sitting in a
cardboard box in the basement. However, if it simply refuses to work,
I have a couple of 1mh tape coils but they're only 16ga.

I noticed you're using an 8 ohm visaton.

1) Steve is probably very sorry for using Visaton drivers in his sims, as always !😀

2) 1,0 mH, 16 ga is in my book considered to be high end. No worries.

This is a promised sim with TFFC tweeter. I can't guarantie anything except
that I've traced manufacturer's measurements with not much hassle thanks
to FP Graph Tracer, produced by a member on PE TT forum. This program
recognizes curves at once and you don't have to click mouse 200 times
while constantly aiming the plot.

Both of the drivers are meant to be in phase.

 

[ShaneF]

That looks pretty reasonable, and inexpensive! I can try 1mh or 1.5mh and "fap around" with the caps. 🙂

The XO is pretty simple for the tweet. That's nice too.

Thanks for that!

 

[ShaneF]

So with the 1mh coil (bass drivers), you wouldn't recommend using the complete crossover for the tweet with the 27tffc? Just a simple cap and coil? The tweeter I have stopped using has basically the same electrical parameters.

http://solen.ca/wp-content/uploads/27tbcg.pdf

http://solen.ca/wp-content/uploads/27tffc.pdf

 

[Lojzek]

The last graph I posted has following values:

woofer: 1,5 mH; 10uF
tweeter: 1R5; 6,8uF; 0,25 mH

There are some differences in IMP graphs.

 

[system7]

1) Steve is probably very sorry for using Visaton drivers in his sims, as always !😀
...snip

NO, it's working very well. The W130S is 0.6mH Le, so is quite similar. 😀

I've been looking at Lynn Olson's Ariel idea, but the second order tweeter seems to leave a hole in the midrange.

I think Shane CAN use his 3rd order tweeter filter here. It's actually quite BW3, which is the right idea for D'Appolito. The bass circuit is not very critical.

I don't see anything wrong with those old SEAS tweeters. I'd use them. The 27tbc/g is a metal dome, the 27tffc a soft dome. Both might like a 7.5R/0.68uF Zobel. Or that 22R.

 

[ShaneF]

I decided to go with a nice classy piano lacquer black for this set of monitors. First coat of seven... after two coats of shellac-based primer.

 

[ShaneF]

I am going to play with the ribbon for now and get a dome in two weeks. They need one more coat of high gloss piano lacquer black, wire them up and they're good to go! 🙂

 

[ICG]

That's not a ribbon, that's an Air Motion Transformer.

 

[system7]

This looks good:

That's not a ribbon, that's an Air Motion Transformer.

An astute observation... 🙂

It's an Airborne RT-4001:

Airborne, RT-4001

3.6 ohms flat, 89dB. >2kHz XO recommended. Does change the filter requirement to 4 ohms. Which means bigger caps, smaller coils. Bit like Solen's suggestion on the top end:

We've pretty much been doing a (different) 2.75kHz crossover on the bass anyway.

 

[ShaneF]

Yeah, sorry, I knew that. Brain fart! 🙂

 

[ShaneF]

They are working out really well! The bass drivers are 'starting' to loosen up and I am getting stuff down in the 50-40hz region. This makes me happy because I hate subwoofers.

 

[system7]

Shane this is marvellous. I see the tweeter is a 85mm rebate, which is small and rather good for an MTM.

I did a sim of the 4.7uF/0.33mH/6.8uF tweeter filter with 4 ohms and it's not too bad at all, just a little peaky. Doubtless you'll need to adjust level slightly with a resistor in front of the tweeter filter.

So, yeah, enjoy. I wish I had your woodwork skills. This is a nice project. 😎

But we still need to see the filter. Without it, it is NO HELP to anybody!

 

[ShaneF]

I just went with the Solen set-up. It's working out quite well! I am quite happy with the strings and cymbals so far. I have followed Marantz' cueue to "biamp" by using A+B channels and added some silver/copper Totem speaker cable, inside and out of the cabinets.

 

[ShaneF]

Watching Godzilla on Netflix... the orchestra sounds.... "epic" 😀

... or... "Apocalyptic" 😀

 

[system7]

You may just have built a poor man's version of the 15,000 Euro Gryphon Mojo. 😀

6moons audio reviews: Gryphon Audio Designs Mojo

Congratulations, my friend. And thanks for sharing all the travails. A great project.

And a big thanks to Solen for an unusual filter:

Freely given away in the best traditions of real humanity. 😎

 

[ShaneF]

Yup!

... and it's worked out just fine 🙂

 

[ShaneF]

I might give that filter on the bass a go. I have the .3 mh, 20mfd but only an 8 or 12 ohm resistor on hand.

Which? 8 or 12?