Crossover Design Changes Based on Horn Dispersion

[toddalin]

I'm designing the crossovers for the surround mini-monitors that will use a W10GTI and a 2425 on a 2370.

They will be based on the "keeper" crossovers that show OUTSTANDING results using the W10GTI, LE175/HL-91, 075.

But the 2370 horn would have different dispersion characteristics than the HL-91. Apparently, this then would change aspects of the crossover???

Radian offers two crossovers that appear identical EXCEPT one is listed for a 60x40 horn and one is for a 90x40 horn.

So, what changes would have been made to the components to compensate for the horn dispersion if I wanted to implement them???

Thanks

http://www.usspeaker.com/radian%20324-1564-1.htm

http://www.usspeaker.com/radian%20324-1594-1.htm

[Earl K]

Hi Todd,

- I'm designing the crossovers for the surround mini-monitors that will use a W10GTI and a 2425 on a 2370.

- But the 2370 horn would have different dispersion characteristics than the HL-91. Apparently, this then would change aspects of the crossover???

- So, what changes would have been made to the components to compensate for the horn dispersion if I wanted to implement them???

- It's generally accepted that it's good design practice, to match the horizontal beam-width of the woofer ( in the crossover region ) to the horizontal coverage of the chosen horn.

- Therefore, if your chosen horn has 90° H. coverage, one would choose a crossover region where the woofers' beam-width has narrowed down to around 90° .

- Different diameter woofers all have different 90° ( 6 db down point vs frequency ) beam-widths .

- You'll need to measure your new tens to find the frequency range where they narrow down to about 90° ( assuming a 90° horn ) . A 10" woofer ( with a 8.5 " effective piston diameter ) is going to narrow to around 90° ( conical ), somewhere around 2000 hz .

I'm designing the crossovers for the surround mini-monitors that will use a W10GTI and a 2425 on a 2370.

They will be based on the "keeper" crossovers that show OUTSTANDING results using the W10GTI, LE175/HL-91, 075.

- I saw the pic of your RTA showing the net results. It did have better midrange blending .
- It's still somewhat a mystery to me how you got "Outstanding" results with a crossover that was designed around an 8 ohm woofer . If I remember correctly, you substituteded in a 3 ohm woofer load ( or 12 ohm depending on how you wired the dual voice coils ) . Why it all worked out for you, is now anyones' guess .

Radian offers two crossovers that appear identical EXCEPT one is listed for a 60x40 horn and one is for a 90x40 horn.

- How Radian offers two crossovers that are advertised as having the same crossover point ( and slopes ), yet are optimzed for different horn patterns is a bit of a ??? for me. I would have assumed a change in crossover point was necessary ( or a tinkering of the slope ) / so, I guess I can't help you much more on the subject .

[toddalin]

Hi Todd,
- I saw the pic of your RTA showing the net results. It did have better midrange blending .
- It's still somewhat a mystery to me how you got "Outstanding" results with a crossover that was designed around an 8 ohm woofer . If I remember correctly, you substituteded in a 3 ohm woofer load ( or 12 ohm depending on how you wired the dual voice coils ) . Why it all worked out, is now anyones' guess .

It's wired for 12 ohms.

A mystery to me too, but the analyzer shows what the analyzer shows.

BTW, without the crossover, the W10GTI measured horrid! There is a broad valley starting ~250 Hz to over 1,000 Hz, then a massive peak at about 2K Hz that doesn't show in any of the JBL literature.

What was amazing to me was that the crossover actually seems to increase the volume in this broad valley making it relatively flat.

I've seen where some crossovers increase the volume of the frequency just below the crossover point, and that appears to be what is happening here to the benefit of the speaker.

[Earl K]

- What was amazing to me was that the crossover actually seems to increase the volume in this broad valley making it relatively flat.

- I've seen where some crossovers increase the volume of the frequency just below the crossover point, and that appears to be what is happening here to the benefit of the speaker.

- Some of these descriptions imply that the woofer load is causing the LC components to "ring" a bit / with an attendant increase in energy . Usually the "ringing" won't be over 1 octave wide & typically it's much smaller in bandwidth .

- Or / you could just be seeing the results of the horn circuit adding it's energy into the mix .

- Or some of each scenario .

[toddalin]

- Some of these descriptions imply that the woofer load is causing the LC components to "ring" a bit / with an attendant increase in energy . Usually the "ringing" won't be over 1 octave wide & typically it's much smaller in bandwidth .

- Or / you could just be seeing the results of the horn circuit adding it's energy into the mix .

- Or some of each scenario .

This is with the horn disconnected.

[Robh3606]

Hello Toddalin

I can't see the links at work so I am shooting from the hip. If all else is equal as far as driver impedances and crossover slopes it could simply be that they are just changing the amount of high frequency compensation. The wider the pattern typically the more HF compensation you need. The narrower horns tend to do a bit of self EQ. The easiest way to check is to look at the directivity plots of the 2 horns and you can usually tell from there what crossover mods they would need between the two horns. It's not exact but it gives you a good idea. Comparing the two horns the more the directivity changes with frequency the less compensation you need for flat on axis response. The key to this is too find the horn plots or take a crack at the schematics.

Rob

[Earl K]

This ( mid boost ) is with the horn disconnected.

Ahhh,, Okay .

- Then the most likely scenario is that you've created a " resonant, ringing midrange filter" which fills in the response dip ( just before F3 on the low pass section of the crossover ) .
- FWIW; back in the 70s', JBL used do this quite a lot in network design ( the 4343 is a prime example ) .
- Nowadays, this approach is generally frowned upon / though I notice that the DD66000 used something very similar in its' horn circuit.

- Anyhow, since you enjoy the sound of this induced resonant energy ( transmitting into a quite heavily coned 10" subwoof ), I wouldn't recommend that you go chasing a higher crossover point, just to satisfy the theory of "matching" the horizontal horn dispersion to the woofers axial dispersion .
- Undoubtably, raising the crossover point ( and redesigning for a more normal LC transform ) will eliminate this midrange "ringing" . And then, more than likely, your satisfaction ( that you presently enjoy for the sound of this woofer ) wil disappear .

- As RobH has pointed out, the 2370 needs some CD horn boost to flatten out it's response / so you'll need to study ( & borrow ) some 2426J circuits ( for the 2370 ) to marry onto the existing LF portion of your network .

[Zilch]

Todd - what is the resolution of your RTA?

If you haven't done so yet, let me recommend you upgrade to 1/6 octave....

[toddalin]

Todd - what is the resolution of your RTA?

If you haven't done so yet, let me recommend you upgrade to 1/6 octave....

Obviously from the photo, 1 octave.

I agree, and day before yesterday had a Behringer 2496 Ultra Curve for $102.05 on evil-bay with 1 second to go when two scalpers moved in and one ultimately got it for $112.

[toddalin]

Hi Todd...
busy this Saturday morning?
-grumpy

Saturday would be great! Linda's going to a yoga retreat all day and Glen wants to pop by and pick up an Altec 421A. Maybe this could happen at the same time.

Glen?

[grumpy]

The earlier, the better for me, but I could probably rotate the day and do some
work in the morning & early afternoon. Let me know.

[toddalin]

The earlier, the better for me, but I could probably rotate the day and do some
work in the morning & early afternoon. Let me know.

Let's see if Glen chimes in. Anytime after 9:00 a.m. is good for me.

[glen]

Let's see if Glen chimes in. Anytime after 9:00 a.m. is good for me.

I generally like to sleep in a bit on Saturdays
so 10:00AM or so would be more my speed,
afternoon would be O.K. too.
If it needs to be earlier not mess up people's schedules
I can make it whenever you say.

Sounds like fun!

[toddalin]

Who doesn't ? If OK, I'll drop by ~9am and can stay up to a few
hours & overlap w/Glen. Measurement setup and social niceties
will take a bit of time anyway. Looking forward to the visit. -grumpy

Actually, Linda also expressed a desire to sleep in and would prefer that we don't start until after 10:00 a.m. Her Yoga retreat starts at noon.

[glen]

I'll see you around 10:00AM then!