speakerfritz:

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

Here are the Belle (black) and LaScala (gray), K33E, using the models that I presented earlier in this thread.

Greg

Pls forgive the noob post. I wish I knew what you folks were going on about. Also, with the graphs and numbers, what is "ideal" or even "better"? What are the practical applications of such differences - do they indicate which is simply the best driver or where xovers have to be changed, etc?

Thx

nola:

Pls forgive the noob post. I wish I knew what you folks were going on about. Also, with the graphs and numbers, what is "ideal" or even "better"? What are the practical applications of such differences - do they indicate which is simply the best driver or where xovers have to be changed, etc?

Thx

Hornresp is a horn analysis and modeling program. You enter the dimensions of your horn, and the measured parameters of your woofer, and Hornresp predicts the frequency and phase response, acoustical and electrical impedance, diaphragm displacement, group delay, etc. It's only a model, so the results are only as good as the assumptions behind the model and the accuracy of the input data. But for comparing different woofer drivers in the same horn, or different horns with the same woofer, etc., it's a nice tool.

Ideally, you'd like for the frequency response to be ruler flat from DC to light. In the real world, of course, that never happens. In the frequency response plots that are being addressed in this thread, people are wondering what causes some of the peaks and dips that seem to occur in the same places in the KHorn, LaScala, and Belle Klipsch. If they are caused by the woofer, then changing the woofer to a different make and/or model might eliminate them. If they are caused by the dimensions of the horn, then changing the woofer won't eliminate them.

Ultimately, as I said before, Hornresp is only a model. While the model can predict general characteristics, the effects must be measured in the real world in order to have any credibility.

Greg

Here's some interesting food for thought. In post #1181505 I graphed a carefully measured internal path for the KHorn, and a Hornresp model for it. Well, I've been experimenting a bit with that Hornresp model and some alternate woofers. And, if you're subwoofing your KHorns, so you can afford to give up a few Hz of KHorn bass, Hornresp says that you can improve the midrange response of your KHorn by a considerable amount.

In the attached graphic I have duplicated that earlier internal path graph, only this time I've added a green line that shows the modifications suitable for use with a BD Designs BD-15 woofer. (This is a VERY expensive woofer, but there are less expensive alternatives that perform nearly as well.) And the Hornresp graph below that shows the improvement that results from the internal modifications and woofer substitution. (Black line is BD-15 in modified horn; gray line is K33E in stock horn.)

As always, models don't substitute for measurements, but this certainly points in an interesting direction.

Greg

Could you show the K-33E in the new horn? And just for kicks, could you show the BD-15 in the original horn?

I do know that the area expansion of the khorn was compromised to make it buildable....same thing goes for the Jub LF (according to the JAES article). Also, these models are only showing the effects of impedance matching the driver and how it relates to the flare rate. Hornresp sorta loosely models polar response, but it's only valid for an axisymmetric horn. I've found that it's often very difficult to optimize both polars and impedance transfer, so you gotta pick your compromises.

All that to say, it'd be interesting to see if you could actually realize a horn the maintains your model without sacrificing other attributes...and being actually buildable.

DrWho:

Could you show the K-33E in the new horn? And just for kicks, could you show the BD-15 in the original horn?

K33E in black, BD-15 in gray. The "ideal" K33E horn also uses the optimum throat size predicted by Keele (which is NOT the same as the optimum throat size for the BD-15) and slightly smaller than stock back chamber volume. For this plot I just used an exponential expansion instead of the piecewise conical approximation; the results are within a fraction of a dB of each other. The "original" BD-15 horn is unmodified from stock Klipsch spec.

I do know that the area expansion of the khorn was compromised to make it buildable....same thing goes for the Jub LF (according to the JAES article).

Agreed. In the "ideal" model I tried to limit the modifications to reduction of cross-sectional area, because it's a lot easier to make the area smaller than it is to make it larger! The exception is in the region between approximately 50cm and 90cm, where the area can be enlarged by making the internal "wedges" smaller.

Also, these models are only showing the effects of impedance matching the driver and how it relates to the flare rate. Hornresp sorta loosely models polar response, but it's only valid for an axisymmetric horn. I've found that it's often very difficult to optimize both polars and impedance transfer, so you gotta pick your compromises.

All that to say, it'd be interesting to see if you could actually realize a horn the maintains your model without sacrificing other attributes...and being actually buildable.

All completely true. Models don't substitute for measurements, or for construction! Frankly, I think that the addition of corner reflectors would probably have more significant effect than the relatively minor changes in cross-sectional area. The "foldback" region, where the path hits the corner and turns nearly 180° to exit the horn, seems to be particularly troublesome.

Greg

Just one thought to throw out there....doesn't decreasing the cross-sectional area increase velocity related distortions?...which predominantly is problematic with the lower frequencies. Klipsch and company seem pretty adament about using rubber throats in all their horns. I can't tell if it's for decreasing throat overload, and/or controlling HF polars, or maybe something else?

Could someone put these three in there for comparison please....

Kappalite on top, Kapplite LF in the middle, and Definimax on the bottom:

All using the exact same horn and rear volume shown in Greg's latest hornresp screenshot.

Thanks Doc.

I was messing with this awhile ago.  I remember thinking the Kappalites "behaving" similar to the K33 in horn or bass reflex.

jc

DrWho:

....doesn't decreasing the cross-sectional area increase velocity related distortions?

Klipsch and company seem pretty adament about using rubber throats in all their horns. I can't tell if it's for decreasing throat overload, and/or controlling HF polars, or maybe something else?

Yes, even Roy has said that PWK was quite fond of rubber throats ... though for the life of me I have never been able to figure out why.

Greg

Here are the best five performers that I was able to find, out of dozens that I tried. Parameters as indicated in the lower right corner of each plot. In each case the K33E in the stock horn is shown in gray for comparison.

The absolute best of the lot is the Altec 515-8GHP, but I wasn't even going to include it because I thought that it was unavailable. But this morning I was browsing the Great Plains Audio site and discovered that they're now making them again!

The BD-15 is within about 1 dB of the 515, but is quite expensive.

As far as I can tell, the B&C 15PE40 is not available in North America.

I don't know about availability of the Ciare 15NdW1.

The EV DL15X should be readily available. If not, the DL15ST is essentially identical.

Greg

Edgar:

Here are the best five performers that I was able to find, out of dozens that I tried. Parameters as indicated in the lower right corner of each plot. In each case the K33E in the stock horn is shown in gray for comparison.

The absolute best of the lot is the Altec 515-8GHP, but I wasn't even going to include it because I thought that it was unavailable. But this morning I was browsing the Great Plains Audio site and discovered that they're now making them again!

The BD-15 is within about 1 dB of the 515, but is quite expensive.

As far as I can tell, the B&C 15PE40 is not available in North America.

I don't know about availability of the Ciare 15NdW1.

The EV DL15X should be readily available. If not, the DL15ST is essentially identical.

Greg

hulkss:

The Altec is a 16 inch driver and is too big and does not fit.

It looks like it will fit in the KHorn woofer chamber. However, I currently have neither a KHorn nor a 515 with which to check.

Greg

Edgar, Thanks for measuring and posting these items.

I have done something similar for the bass bin outlined in the JAES, 2000 article (which later became the Jubilee bass bin). I am confused about something however. When I plotted the cross-sectional area as a function of distance (the expansion) and also plotted the appropriate exponential functions, the "rubber throat" was clearly evident. The initial section (first 20 cm) had a cross section that jumped from 0.029 cm2 (at the throat) to a factor about double in that distance. IOW a flare rate of nearly 100 Hz (as described in the paper).

I do not see that rapid flare in your graph for the Klipschorn. I thought the Klipschorn also had a comparable rapid flare in the initial section.

Regarding the other question: Yes, I also believe the rubber throat was to minimize the 2nd harmonic distortion that is created when the relatively small volume of air (near the throat) does not symmetrically oscillate in pressure variation. Others have suggested the rubber throat is a way to cheat and shorten the "necessary" length of the horn. However, when you look at the exponential (at 38 or 40 Hz flare) next to the measured values (with the rubber throat), the length really has not been shortened.

Again, thanks for your efforts on this,

-Tom