Flint Acoustics: Outdoor Coaxial System

[Flint]

I am almost finished building my new small coaxial speakers intended for use in a protected outdoor area. The drivers are made from weatherproof materials (polypropylene, butyl rubber, etc.) and the cabinet is heavily sealed both inside and out, and the glue used is water-proof. I even made the grill cloth from window screen to keep bugs off the driver.

I will post a write-up as soon as I make measurements and spend some time listening to them. I am also planning to build a subwoofer to go with these, also designed for protected outdoor use. In my case they will be installed on my patio.

 

[bmwuk]

I'm sure it will sound nice

 

[PaulyT]

Cool. But if you could make them look like rocks or trees or fountains or small forest fauna, you'd improve your commercial viability.

 

[bmwuk]

Cool. But if you could make them look like rocks or trees or fountains or small forest fauna, you'd improve your commercial viability.

Or garden gnomes.

 

[Haywood]

Cool. But if you could make them look like rocks or trees or fountains or small forest fauna, you'd improve your commercial viability.

I vote for garden gnomes.

 

[Flint]

Well, here it is!



Those purple speakers are my new 5.25" coaxial speakers intended for protected outdoor use. They are tuned to sound decent when installed up under an eave or against the roof of a patio (where I'll use them).

 

[Flint]

These are sealed enclosures (to keep more stuff out of the cabinet) and I installed a window screen grill cloth on them.

Here are some build photos:


Photo 1: Raw Coaxial Driver from Dayton Audio


Photo 2: 1/2 inch MDF Panels which became the enclosures


Photo 3: Sides of enclosures being glued up using waterproof Tighbond wood glue


Photo 4: Rears of enclosures being glued on


Photo 5: Assembled enclosures being sealed

 

[Flint]

Continued...


Photo 6: Grill frames being sealed and primed


Photo 7: Cabinets being painted the final color


Photo 8: Assembled while auditioning


Photo 9: Grilled mounted on speaker
Photo 10: Rear of enclosure

 

[Flint]

Continued...


Photo 11: Speaker being measured in a nearly full Anechoic environment


Photo 12: Speakers being auditioned in my front room.

 

[Flint]

These are a very basic enclosure style, sealed and stuffed with 60% acoustic material.

I chose to go with a electric/acoustic crossover with an effective slope of about 12dB/octave. Because the output response of the tweeter was very high below 4kHz, I relied on an 18dB/octave butterworth crossover which resulted in a 12dB/octave acoustic slope. The woofer got a simple 12dB/octave crossover with a impedance equalization circuit.

Chart 1: Predicted amplitude and phase response with crossover, Blue = combined / Yellow = Woofer / Red = Tweeter

Once built, the actual performance as very close to the predicted performance:

Chart 2: Measured amplitude response using crossover (no cabinet).

 

[Flint]

After assembly of the complete system in the enclosure, I was very pleased with what I was hearing. I chose to go with a diminished "presence" response with a dip in the 2kHz to 5kHz range on purpose in order to have a more pleasing sound outdoors where we tend to need to play the sound louder and the reflections off the hard walls tend to increase the perception of the presence range.

Here's the power response smoothed in accordance with standard marketing practices:

Chart 3: Market Power Response

I could write a spec sheet claiming to have a range of 90Hz to 20kHz, +/-3dB. I could claim an even higher response limit, but we cannot hear above 20kHz, so I wouldn't bother.

Here's the anechoic response:

Chart 4: Anechoic Response at 1W/1M: Black = 0 Deg / Red = 15 Deg / Brown = 30 Deg / Orange = 45 Deg / Yellow = 60 Deg

 

[Flint]

In my listening tests, they sound a bit dull indoors, which was expected. They certainly put out plenty of volume and the bass is surprisingly plentiful and very clean. According to the measurements, the bass limit (-10dB point) is about 62Hz, so they should blend well to the subwoofer I am building next.

Outdoors, however, they really shine. In fact, while measuring the speaker up on the 9ft high stand on my driveway I put on a song to see how they sounded outside, and I was blown away. I ended up listening to about a dozen songs that way before I got back to work on measuring the speaker. I even put a video of that on all my social media platforms.

I look forward to mounting these under the roof of my patio and enjoying them. I may go through that process before I build the subwoofer so I can enjoy them immediately.

If I were to sell just these speakers as a stereo pair, I would need to charge about $300 for them, probably list their "retail" price at $450.

The specs would be:

• Response: 90 - 20,000Hz, +/-3dB
• Effective Bass Limit: 65Hz (-10dB)
• Impedance: 8 Ohms
  
• Power Handling: 160 Watts RMS, 80 Watts Continuous
• Sensitivity: 85dB SPL at 1W/1M
  
• Max Output: 101dB SPL at 1 Meter per speaker

 

[Flint]

As for the bright and somewhat unusual colors I keep painting my speakers, I am just demonstrating what is possible and I am completely bored with so much grey, brown, and black used in damn near all home audio and home furnishings.

When I chose the colors purple and green, I was holding the cans of paint next to each other on the paint aisle of the store. It wasn't until I assembled these speakers that it dawned on me that I chose the colors used by The Joker in the 1960s Batman TV show.

 

[Zing]

It won't be long before you're wearing clothes in those bright colors.


Oh wait.

 

[mcad64]

I wonder if your neighbours ever wonder" What is that crazy Flint guy up to now?"
Mike
Oh yeah, I dig the colour!!

 

[Flint]

I wonder if your neighbours ever wonder" What is that crazy Flint guy up to now?"
Mike
Oh yeah, I dig the colour!!

Most of my close neighbors are fully aware and some visit while I work. My left-side neighbor has a wood shop in his garage as well, but he makes small furniture pieces. When we are both out there working, it gets pretty noisy on my street.

 

[Wardsweb]

Go with color Flint. You will be in good company.

 

[Dentman]

I'm so far behind on all this stuff. Very nice.

 

[Flint]

I just finished installing these speakers outdoors under the ceiling of my patio. I put them deep in the corner and angled them down and towards the middle of the area where I put my seats.




Since I knew these would be placed in a corner, I tuned the bass performance to be a tad "weak" in an anechoic environment because I would have solid reinforcement from one plane (ceiling) into the midrange and another plane (larger house wall behind the seating) up to about 120Hz. Also, since all the surfaces are fully reflective, I designed the crossover with a large depression in the midrange to counteract the reflections in that range which will make the sound "honky" if it were a flat output to start with. The treble is a tad brighter than I'd like, but the amp I am using now (Dayton Audio DTA-2.1BT2) has a tone control to tame it a bit.

Great sound, and it can play way louder than I'd ever possible want.

Next step is to build the matching sealed 12" subwoofer and hook it up.

I'll make listening position measurements and post them later.

 

[Flint]

Today is a gorgeous day, so I took my PC and test gear onto my patio and did some measuring of the installed system.

Here's a chart with the frequency response for the coaxial speakers installed:


I adjusted the gain of each curve so they are the same approximate level so you can see the differences between left, right, and out in the yard.

• Bright Red Line - the response of both speakers with the microphone placed about 10 feet out into the yard at standing ear height
• Orange Line - the response of the left speaker from the most center listening seat with the mic at seated ear level
• Black Line - the response of the right speaker from the most center listening seat with the mic at seated ear level

I am most surprised at the fact almost all of these curves are identical despite the difference in mic placement, using one or two speakers, or whatever. I may put all the curves onto one chart just to make it more clear.

The dip centered at 400Hz is from the reflection off the wall behind the listening position. The speakers are mounted out in front of that wall about 6 feet away. That is the equivalent to a floor bounce null, but it is off the rear wall.

So, the bass is solid to about 100Hz and I am building a subwoofer right now to supplement the bottom end. The midrange still appears depressed in the measurements, but it doesn't sound that way since the walls, floor, and ceiling are darn near 100% reflective. The treble is a tad strong, and that is also how they sound. This is my only real complaint which I could have addressed with changes to the crossover. Maybe a impedance compensation circuit on the tweeters would have mellowed that just the right amount. However, at lower listening levels, which is where they will most often get use, the boost in the treble sounds kinda nice - sorta like a natural loudness curve which I like most of the time. However, when I turn it up enough to really listen closely to music, it is bright to my ears. But how often will I turn them up that loud outside?

Fun stuff!!!