Horn loading x4 Scanspeak 10F midrange drivers

[Joseph Crowe]

I would like to share my blog post on horn loading x4 midrange drivers and the resulting acoustical measurements compared against a single non-horn configuration. Please let me know your thoughts or questions. This is now what I'm using for my main listening rig. After some EQ to flatten the midrange hump it sounds very good!
I also did distortion limited SPL tests and the horn will now do 122dB SPL (1% distortion threshold) form 250Hz-2kHz.
Cheers from Ontario Canada!

https://josephcrowe.com/blogs/news/scanspeak-discovery-10f-4424g-in-e-250-horn

 

[q3cpma]

Quite cool, your polar map isn't very readable, though; maybe use a lower scale. What do you think about benefitting from Geddes' patents like some absorbing material to coat the inside of the horn and reduce diffraction, since you're probably safe as long as you don't sell it; even if it looks like Klipsch uses rubber in its horns.

 

[Joseph Crowe]

Quite cool, your polar map isn't very readable, though; maybe use a lower scale. What do you think about benefitting from Geddes' patents like some absorbing material to coat the inside of the horn and reduce diffraction, since you're probably safe as long as you don't sell it; even if it looks like Klipsch uses rubber in its horns.

Thanks. I realized the coloured polar map scale was not set to the standard 25dB scale. So I've updated it here. I will update the blog as well.

 

[Joseph Crowe]

Quite cool, your polar map isn't very readable, though; maybe use a lower scale. What do you think about benefitting from Geddes' patents like some absorbing material to coat the inside of the horn and reduce diffraction, since you're probably safe as long as you don't sell it; even if it looks like Klipsch uses rubber in its horns.

The use of foam, which 30ppi open cell foam is common, really helps with certain horns such as constant directivity or many of the classic horns such as the Altec 511B. However I've had limited success with foams on my own ES horns which has the horn flare geometry wrap completely around to the rear of the horn similar to the JMLC horn flares. This type of horn does not have any measurable levels of resonance and so there is no need for the foam. Off axis response is textbook perfect and the burst decay plots don't show any anomalies either. You can see what I mean with the tests I've done with the TAD TD-2001 on the ES-800 Biradial wood horn. https://croweaudio.blogspot.com/2019/10/tad-td-2001-on-es-800-biradial-horn.html

 

[jhaider]

Very cool project! That's a really nice midrange on its own. Your waveguide looks to have excellent performance as well.

Why is the polar map scale ±60º instead of 90 or 180 though? Is that what you could reasonably measure?

 

[Joseph Crowe]

Very cool project! That's a really nice midrange on its own. Your waveguide looks to have excellent performance as well.

Why is the polar map scale ±60º instead of 90 or 180 though? Is that what you could reasonably measure?

Thanks, I did make measurements up to 90 but the standard is 60 which I think helps focus in on the coverage in the upper treble. My target response for a polar map is wide coverage (80 degrees+) up to 13kHz. The way the non-horn version quickly narrows in treble coverage compared to the midrange coverage is very detrimental to the sound quality. Instruments will not be rendered with proper timbre because of the bloated midrange power response into the room. If I extended the polar map to 90 degrees off axis the difference would be even more pronounced. I believe I saved these in another folder and I can publish this tomorrow.

 

[Joseph Crowe]

Also, for interest’s sake, here’s a polar map I did for a regular 2-way bookshelf speaker with a 6.5” woofer and 1” dome tweeter. This would be pretty common I think for this type of speaker. I’ll publish the other graphs tomorrow.