300 - 1500 Hz: Horn vs Open baffle mids

[rick57]

We recently had "Horn vs Open baffle bass"

But as you know, most of the music is in the mids, and the need for a massive horn doesn’t apply over the mids.

Driver budget say max $US 300 per side.

Over 300 Hz, room modes are less of an issue, though still effect sound quality
And good off axis response is *highly desirable.

So to start the discissions, some contenders from both ‘corners’:

Horn:
Not my area, though maybe will be:
PHL/ Audax Pro 170/ Fostex??/ B&C 6PEV13 or with Faraday ring B&C 8PE21: dB = ??

I hear conical horns are best. Are pyramidical horns equally good?
Is a back chamber necessary?

Dipole:
From the SL school:
- Two SS/ Usher/ Excel mids (two = lobing): 94 dB
- Or one (-6 dB, no lobing Problems): 88 dB

Towards horn sensitivity:
- PHL 3451: 100 dB

What's best?

[John Sheerin]

A large horn <b>is</b> necessary to cover 300hz and up - a 150hz flair rate horn would be a good start. This is because horns store a lot of energy at their low end, at least in limited measurements I have taken (working on taking more, but that means I have to build more horns). With a 500hz tractrix horn, I had to go an octave or more above the flair frequency to get clean output.

[Mentero]

Hi,

Here is my take:

midhorn

I experimented very little with back chambers, but did not like the results.

With the open back, you can call it an open baffle, or a horn, depending on your mood.

Very easy to build and try, too.


Miguel mentero

[rick57]

Hi John
Good point - how big might a 150hz flair rate horn be?

Hi Miguel

The B&C 6PEV13 spec gives 99 dB. What approx dB do you think it’s giving in your pyramidical conical horn?
I note the curves are unsmoothed, but I might have hoped for more smoothness. Do you think that’s more driver or specific horn configuration?
What do you not like about rear chambers?

> sure deserves further investigation
What will you change?

Driver wise:
What’s the best up to $US 300/ driver
Any Fostex contenders?

Regards

Richard

[KCHANG]

Hi Rick57,

One speaker project I put together recently uses one Audax PR170M0 on a 3'-wide OB on each side to covery 300Hz to 8KHz, and this system sounds quite good to me. I also have a pair of JBL CS3115 speakers that have horn-loaded 8" drivers covering 400Hz-1600Hz. They both sound great, but I like the overall presentation of the Audax system better. The Audax on OB is not as efficient as the horn-loaded JBL midrange, but 98dB is not too bad.

Kurt

[rick57]

I see that many horn ‘mids’, at least those listed at http://ldsg.snippets.org/sect-6.php3
Do not go below 500 or 1000 Hz.

Hi Kurt

That comparison is interesting. JBL's being reasonavbly good, though I don't know that model; what was the horn profile?

There’s a trade off in most things, and I don’t yet know what the trade off with horns may be for the higher efficiency.

As you say, 98dB is not too bad; the PHL 3451 (although 10 inch) has similar db & FR specs.

Richard

[KCHANG]

Hi Richard,

The CS3115 is nearly identical to the VS3115 model shown here:

http://www.jblpro.com/pub/obsolete/venue/vs3115.pdf
http://www.jblproservice.com/pdf/Ven.../VS3115-WH.pdf

The midrange horn looks like a rectangular conical horn to me.

Kurt

[John Sheerin]

A 150hz horn is big. Here is a 150hz tractrix I built a long time ago:



A Le Cleac'h flair with a rollback at the mouth would be even bigger. You can find calculators or equations online to calculate the exact size.

Most pro-sound response ratings (especially for compression drivers) are not necessarily indicative of what you can do for hi-fi usage. You will typically be using 1/10 to 1/100 the power, different horns, and so the response range you can get is different.

[rick57]

Hi Kurt
Looking at the JBL PDF, I didn’t realise quite how directional horns were, or how small purpose built morns mids were.
When you said “I like the overall presentation of the Audax system better”, could you elaborate – in what respect?

Hi John
To me, that 150 Hz horn doesn’t look too big. (My other half may see things differently). On the aesthetic side, the colour isn’t exactly low key – is that Coca Cola Red?

How might a conventional driver with the right parameters for horn loading (eg B&C, PHL) compare with a compression driver (cd)?
I assume a cd is more efficient – any other differences?

Thanks

[Tim Moorman]

I'll chime in, too. I think either system can sound very good, but there are two different approaches here, naturally.

The OB school suggests a wide range high efficiency (generally) mid driver covering the vast majority of the spectrum with supplemental drivers added top and bottom for the extremes.
This is an ideal place to start in diy due to the simplicity of crossovers and enclosures.

Due to the nature of the beast, a horn midrange is not so broad in its coverage, and also due to its limited bandwidth (relative to full or wide range mids) needs to be matched well with other drivers because the crossovers fall into the more audible portions of our hearing.
The result, however, can be well worth the additional complexity.

Tim