Ikea Midbass Horn - diyAudio
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Old 3rd July 2014, 04:46 PM   #1
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Default Ikea Midbass Horn

Here's a horn sub that fits into an Ikea Expedit.

I am doing an Opsodis setup, and so this 'sub' is really designed for midbass duty, not for sub duty. I'm actually sitting on a subwoofer, so this box goes to my left and to my right and it's designed to do midbass duty between my sub and my Synergy horns.

This is an xpost from someone else's thread on Ikea speakers; I didn't want to clutter up their thread with my content.

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Here's the design. It's a clone of the Danley BDEAP, but shrunk to fit into an Ikea Expedit. The drivers are a Dayton ND91. The horn is tuned to 180hz. The sealed part of the enclosure is 4" PVC that's been sliced in half. The wood is 1/2". You can use MDF or plywood.

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I got started by using Eazy Horn. These are the params it gave me.

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Here's the hornresp parameters

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Here's a comparison of the output of the horn with two woofers, versus a bandpass box with four woofers. The bandpass box plays lower and is smoother, but the horn is louder. The horn sim shows some nasty peaks. In my experience, I've found that hornresp exaggerates peaks. So hopefully it's not that bad IRL. Also, I would like to use at least two per side, for midbass impact, and arraying the horns will smooth the response. The BDEAP is designed to be arrayed.
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Old 3rd July 2014, 05:00 PM   #2
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Here's the frequency response. The blue line is the horn sub. The green line is my Kef sub, and 8" vented box. I use the Kef as a reference when I do sub measurements.

The Kef goes lower and the Kef is smoother, but what I really wanted from this box was something with high efficiency and high output. My mains are Synergy horns, and I didn't want to 'pad' the Synergy horns, so the midbass needed to be LOUD. Based on this measurement, it looks like this midbass horn is giving me about seven more decibels output in the passband than the 8" Kef. The Kef enclosure is also twice as big.

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Here's a comparison of the distortion of the two enclosures. The THD of the Kef is about 20-25dB below the fundamental; the THD of the Ikea horn is about 10dB better than that. The THD of both boxes goes up like a hockey stick as you get lower in frequency, due to excursion.

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Horn subs can be a p.i.t.a. to build, but I appreciate this curve. This is the phase response of the 8" Kef and the Ikea midbass horn. Note that the Ikea midbass horn doesn't have the phase rotation that the Kef does. This is because the Kef is vented.
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Old 3rd July 2014, 05:19 PM   #3
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Cost was a big factor for this sub. The wood in the sub was less than a dollar, the glue was twenty five cents, the drivers are $24 each. Total cost : about $50.

For comparison's sake, a good prosound 8" like the B&C 8NDL51 is $119. The B&C will require a passive filter, which costs about $10. So the B&C will be about as efficient, and has higher maximum output, but it costs almost three times as much.

I did some hornresp sims, and this box seems fairly compatible with other woofers. For instance, the response with the Faital 3FE20 is basically the same as the Dayton. Due to the simple layout of the box, you could probably get the cost down to about $30 a channel if you used a woofer that cost less than $15 each. There are some good candidates from Dayton and MCM.

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This gets particularly interesting when you realize how easy the horn is to build, and how it's designed to be arrayed, and how the Ikea Expedit makes creating an array very easy.
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Old 3rd July 2014, 05:39 PM   #4
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Out of curiosity, I tried the same enclosure with the MCM 55-1870. (MCM Audio Select 5'' Aluminum Cone Woofer | 55-1870 (551870) | MCM Audio Select) Using the MCM gets the cost down by 50%, to less than $25 per horn. (This assumes you're building at least two, and you're paying $11.49 per woofer.)

The MCM has wider bandwidth and flatter predicted response than either the Dayton *or* the Faital, so it looks like a solid choice. Main issue is getting the magnet to fit really.
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Old 3rd July 2014, 06:57 PM   #5
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Are the t/s parameters for MCM drivers really trustworthy?
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Old 3rd July 2014, 08:27 PM   #6
freddi is offline freddi  United States
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that's pretty cool - my town has no Ikea -
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Old 3rd July 2014, 10:42 PM   #7
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Quote:
Originally Posted by freddi View Post
that's pretty cool - my town has no Ikea -
Fun fact : Nevada is one of the fastest growing states in the USA. And has no Ikea. Go figure.

Fun fact 2: the best Ikea in the USA is in Portland. There's no sales tax, and it's less than a mile from Washington, which has no income tax.
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Old 3rd July 2014, 11:04 PM   #8
xrk971 is offline xrk971  United States
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I still don't understand the geometry.
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Old 3rd July 2014, 11:07 PM   #9
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Quote:
Originally Posted by xrk971 View Post
I still don't understand the geometry.
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It's a Sound Physics Labs B-DEAP

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Just smaller. 13" x 13" x 6.5" to be exact. Fits in an Ikea Expedit.
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Old 3rd July 2014, 11:33 PM   #10
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Quote:
Originally Posted by Patrick Bateman View Post
It's a Sound Physics Labs B-DEAP
Just smaller.
And instead of the B-DEAP's nearly two octave passband, the smaller unit has just over one octave of range, with rapid phase "rotation" (around 540 degrees) centered in the critical 450-900 Hz upper crossover region. Note that the Kef doesn't have the upper phase rotation that your "Ikea" midbass horn does .
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