That's interesting that the 150Hz hump shows up in the models too....could always EQ it out and get away with a lower xover frequency.

DrWho:

That's interesting that the 150Hz hump shows up in the models too....could always EQ it out and get away with a lower xover frequency.

Yes, flat response down to 80 Hz looks possible for the LaScala by pulling down the peak. I'm going to give this Ciare 15.64 NdW1 a try. Available at Assistance Audio This is a Neo magnet woofer with lower mechanical damping and a more powerful motor (than the K-33) for quick high impact response.

Interesting ...

You and I used very different models, and even very different woofer parameters, yet Hornresp comes up with very similar results. Your LaScala model in black, my LaScala model (from my post yesterday, with Vrc corrected to 58 L -- apologies for the oversight there -- also 3 dB correction applied for the 4/8 Ohm difference) in gray:

Greg

Edit: K33E in both cases.

Edgar:

You and I used very different models, and even very different woofer parameters, yet Hornresp comes up with very similar results.

I opted to use a similar throat model in the LaScala as you used in the Khorn. That is, calculating throat area (S1) at the "splitter" after the horn doubles into two paths. Then entering the slot area as (Atc) area of the throat chamber. I also lengthened the last horn segment and shortened the middle segment slightly maintaining the overall length. This was to prevent the "Cir > 1" warning. The help file in "Hornresp" states that results are invalid if this message appears.

I have modeled a lot of horns in "Hornresp". It takes fairly big percent changes in a model to make a significant difference in the SPL output. After all, a 6b change requires the acoustic pressure to double.

hulkss:

It takes fairly big percent changes in a model to make a significant difference in the SPL output.

I think the plot of more interest is the acoustic impedance response....you'll be able to see smaller differences more readily. You gotta double the impedance to introduce a 3dB change in the frequency response. The more jagged the acoustical impedance, the more ringing you're gonna get... (assuming that the wave travelling down the horn satisfies the assumptions hornresp makes).

hulkss:

I opted to use a similar throat model in the LaScala as you used in the Khorn.

It's a tough call -- how to handle folds when the cross-sectional area changes significantly within the fold. After I developed the LaScala and Belle models, I went back to my KHorn model and changed the throat model. The overall effect was negligible.

This was to prevent the "Cir > 1" warning. The help file in "Hornresp" states that results are invalid if this message appears.

Yes, I understand. The warning says that the throat acoustical impedance becomes invalid. I experimented with that a bit and found that changing the area enough to avoid the message had no discernible effect upon the results, so the models must be very "close to the edge".

I have modeled a lot of horns in "Hornresp". It takes fairly big percent changes in a model to make a significant difference in the SPL output. After all, a 6b change requires the acoustic pressure to double.

That matches my experience, as well. Overall, horns are pretty tolerant of moderate changes in cross section, as long as overall length, throat area, and mouth area are maintained.

I'm still refining the LaScala and Belle models. It's not like it matters, so I think maybe I'm a glutton for punishment. I revised the throat model as suggested by hulkss, and made a few minor changes in the cross-sectional area profile. These models still get the "Cir > 1" warning in Hornresp, but if you ignore that and compute the response, and then modify the areas just enough to avoid the warning and again compute the response, the differences between the two are very small.

LaScala here; Belle in a followup post.

Belle

 What happens if you add corner reflectors to the back of the La Scala bass horn?  How does the response curve and impedance curve change?

John Albright:

 What happens if you add corner reflectors to the back of the La Scala bass horn?  How does the response curve and impedance curve change?

This graph may be misleading.  Because you set the lines equal at 100 Hz, it makes the K-33 look like the worst driver and the Altec look like the best.  What do the curves look like if they are not indexed to be equal at 100 Hz.  How did your Ciare 15.64 curve in the real K-horn compared to the predicted response? 

A Peavey FH-1 is similar to a La Scala  with a smaller back air chamber and a bit longer horn.  The OEM woofer distorts excessively.  Any way to estimate how the Ciara woofer would behave in them?  I have 4 that could use better woffers, but we need to keep the high power handling of the OEM woofer. 

hulkss:

I evaluated dozens of current production 15" drivers and could only find a few that would outperform the stock K33 by any significant amount. Here they are all on one graph. The Bob Crites driver is the only 4 ohm impedance "direct" replacement in the group.

I tried to match the responses at 100 Hz so they would be relatively easy to compare. I'm not sure if all these drivers will fit. I'll model the same drivers in the La Scala next.

Here's a list of some other woofers worth checking-out in this application. I have chosen them because they all show nicely extended high frequency response in Hornresp. But I have not tried them specifically with the KHorn, LaScala, or Belle models, so I do not know how well they will perform with the Klipsch throat dimensions or rear chamber volumes.

B&C 15NDL76
B&C 15PE40
B&C 15PL100
B&C 15PS76
B&C 15PLB76
B&C 15TX
B&C 400AMX
BD Designs BD15
Ciare 15.75SW
Ciare 15NDH-4

Greg

the real question is not what causes the 200hz hump, but rather, what causes thew 300hz dip.

 wonder if the belle has the 300hz dip...we may have an implied answer.