Technical Questions

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

andrea — Tue, 07 Jul 2009 15:39:12 GMT

Excuse me

Why the hornresp parameters of pag 1 and 2 for k-horn are differents (see for ex Vtc)?

thanks

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

dBspl — Thu, 02 Jul 2009 20:17:29 GMT

The original Klipschorn had a woofer baffle opening of roughly 6" X 12". The baffle opening was cut in half at some point (probably in the 50's) to improve the upper frequency response of the bass horn.

I believe the first horn section in the Klipschorn (between the baffle opening and the first bend) does flare faster than the last two sections, but I can't be sure. My understanding of the purpose of a "rubber throat" was to control the horn resistance in a way such that it results in a flatter passband repsonse, but I've never seen any experimental evidence to suggests that it actually works.

dbspl

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

Edgar — Thu, 02 Jul 2009 18:36:17 GMT

PrestonTom:
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.

There are a couple of possible explanations.
- First, I didn't measure a Klipschorn; I measured a Speakerlab K from a set of 1980 plans that I have. It is possible that the Speakerlab was not a completely accurate copy of the KHorn. It is also possible that the KHorn internal design changed with time. Or it is possible that the KHorn didn't actually use a rubber throat.
- Second, in the KHorn (Speakerlab K), the woofer opening is 39in², but that dumps directly into a horn whose throat is 78in². Perhaps that is what someone has called a rubber throat?

Greg

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

PrestonTom — Thu, 02 Jul 2009 17:46:26 GMT

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

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

Edgar — Thu, 02 Jul 2009 16:06:57 GMT

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

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

hulkss — Thu, 02 Jul 2009 15:21:08 GMT

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

The Altec is a 16 inch driver and is too big and does not fit. The BD-15 is only available from one source in the Netherlands and is very expensive. I am now listening to the Ciare 15.64NdW1. It mounts identically to the K33E and bolts right in to a La Scala II cabinet. I did have to open up the access hole a tiny bit to get it in. You can see in the photo where I filed on the opening. It is availabe here for $158. Ciare at Assistance Audio.

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

Edgar — Thu, 02 Jul 2009 11:58:22 GMT

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

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

Edgar — Thu, 02 Jul 2009 11:11:26 GMT

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

In applications such as ports on vented boxes, yes. In horns, I think that the predominant problem with small throats is "horn throat distortion", which is related to nonlinearity of air at high pressure. While that can be a problem at the high SPLs used in sound reinforcement, for home use I doubt it.

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

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

jwc — Thu, 02 Jul 2009 03:21:44 GMT

Thanks Doc.

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

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

DrWho — Thu, 02 Jul 2009 03:11:42 GMT

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.

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

jwc — Thu, 02 Jul 2009 02:57:10 GMT

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

http://eminence.com/pdf/kappalite-3015.pdf

http://eminence.com/pdf/kappalite-3015lf.pdf

http://eminence.com/pdf/definimax-15lf.pdf

Thanks

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

DrWho — Thu, 02 Jul 2009 02:47:05 GMT

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?

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

Edgar — Thu, 02 Jul 2009 01:35:04 GMT

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

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

DrWho — Thu, 02 Jul 2009 00:42:33 GMT

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.

Re: "Hornresp" analysis input parameters for Lascala II and currennt model Klipschorn

Edgar — Wed, 01 Jul 2009 19:25:15 GMT

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