Simplest bass horn design to use as a tv-bench

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What size?

I can go 50 inches wide and maybe 20 inches depth

The Decware isn't a horn, it is a bandpass box. Horns are way larger. This is an example of a horn that only reaches down to 50 Hz: Speakerplans.com

Aha! Do the gradual horn like expansion is the ports in this case?
I was under the impression of band pass enclosures being something like a ported design with the front of the woofer being sealed.

fwiw LittleMike packed a lot of path into his relatively tiny Anarchy tapped horn:

LittleMike's Anarchy Tapped Horn - Home Theater Forum and Systems - HomeTheaterShack.com

Looks like only 88 db sensitivity? :scratch2:
 
Aha! Do the gradual horn like expansion is the ports in this case?
I was under the impression of band pass enclosures being something like a ported design with the front of the woofer being sealed.
Hmm yes what you describe is a regular bandpass box. I was under the impression that the Decware had this configuration, though now I take a better look at it, I see that there is no enclosure to accompany the port. My bad.

Maybe the air column in front of the woofer does not act as a port but as a 1/4 wavelength resonator, similar to a Helmholtz resonator (enclosure + port). The length isn't exactly 1/4 wavelength because it tapers.


I can go 50 inches wide and maybe 20 inches depth
What height would be acceptable?
 
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sorry - I was thinking something small. For something with good 40Hz capibility away from a corner plus gain and power, go search for the Vitavox "THUNDERBOLT".

Here's a thread with a build and Jim Bell's offset driver Hornresp model. (The back chamber is closed so I don't know why there's
a confusing slot shown in the build - ?)

Also, in my sim, (probably as a goof vs looking at JBell's input) I set the segments as "parabolic" which gave a nice response - but Jim's model specified "conical" and that gives a LF dip with Kappa15a and JBL's M151. When does one pick conical vs parabolic
for a fold like the Thunderbolt ?


Bass Horn Build (The Thunderbolt)

I've been told by a world renown horn pro that the drawing in the picture below is true scale and IIRC the woofer frame is 15" in diameter.. Look up the horns dimensions and see if it will fit your circumstance.

You see even with a low moving mass - low qts speaker like EV's 1L that its over 100dB@40Hz in half space.

looking at the pic below, its roughly 3ft deep

w6sZoyx.png
 
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ah - from page 3 of that Thunderbolt thread - Jim Bell's refined model using PAR segments. It could be directly scaled to a 12 but would move the LF cutoff upwards. He also tightened the back chamber in this model. That could be done with foam insulation pieces.

205188d1294889087-bass-horn-build-thunderbolt-thunderbolt3-jpg


Here's a Thunderbolt simulation with Eminence Kappa15a 2 pi vs a really solid corner

dOiULUh.png
 
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Looks like only 88 db sensitivity? :scratch2:[/QUOTE]

Hoffman's Iron Law: High sensitivity, small size, low extension. Pick any two.

I have two Anarchy tapped horns driven by an Adcom GFA-535 in a 20'x12' room and they are definitely surprising for their size. They go deep and play reasonably loud before showing signs of stress. A 6.5" woofer with 12.5mm of Xmax doesn't hurt. I use them mainly for movies in a 7.2 system.
 
And what height?
SPL requirements?

About the same as depth, so maybe 20-25 inches?
I'm more concerned with dynamics than SPL requirements. Something like 115 db with 50 watts is more than sufficient.

sorry - I was thinking something small. For something with good 40Hz capibility away from a corner plus gain and power, go search for the Vitavox "THUNDERBOLT".

Thanks for the link to this design!
I'm thinking something with a 10-12 inch driver using the floor as an extension of the horn mouth. Along the lines of that Decware design.

Or something like this (just a dirty photoshop, but you get the general idea):
 

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About the same as depth, so maybe 20-25 inches?
I'm more concerned with dynamics than SPL requirements. Something like 115 db with 50 watts is more than sufficient.

A single 15" in a classic BR designed to your desired dimensions, can get you to the desired SPL but with a little bit more power, will be much easier to integrate with mains, and goes deeper than what you want.
 

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Dynamics are the difference between loud and soft parts. As long as the subwoofers plays in its linear regime, all subwoofers have equal dynamics.

If you mean that you want a tight bass, the problem usually lies with room modes. Using multiple subwoofers and a parametric equalizer (DSP) or bass traps can fight them. Once this problem is solved and you want even more punch, boost the 100 - 150 Hz region.
 
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Very much so, much easier to integrate a sub that has a reasonably flat response, since you'll get all sorts of issues when you put it in a room anyway. A sub with a jagged response may end up having peaks and dips in the worst possible places, requiring much more adaption to suit the room.

I agree that two subs is better than one, but since OP has a specific placement intended for the sub, splitting it in two might not make much of a difference.
Two 12" or even 15" can work pretty well in separate 120 liter chambers though.
 
About the same as depth, so maybe 20-25 inches?
I'm more concerned with dynamics than SPL requirements. Something like 115 db with 50 watts is more than sufficient.

Hmm, for an actual compression horn a 25 x 50" mouth = ~13543/150 = ~90.3 Hz, so terminated on the floor and perpendicular to it [2pi space] = ~90.3 x 0.707 = ~63.8 Hz.

Length = ~13543/2/40 = ~169.3" x 0.707 = ~119.7", so between these two you don't have nearly enough space for the kind of performance you're wanting at 40 Hz.

The Thunderbolt with its rolled off LF, modest 'ripple' seems a good compromise, but both these horns require sitting pretty far away for max impact whereas a multi 12-15" HE driver short throw truncated reflex horn similar to Altec's 'A' series cinema systems are much better suited for HIFI/HT apps.

GM
 
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