Throwback Sprite Variant

[dstmbgh]

This past Christmas my youngest daughter was home from college and informed me that one of her roommates had moved out, and now, when she and her other roommate wanted to listen to music on something "better" than their laptop speakers, they had to plug into the TV. Any self-respecting speaker-builder-hobbyist father can't have that, now can we? So, I saw this as an opportunity to enjoy indulging my hobby so that she could better enjoy listening to music. My enjoyment of music is such a meaningful part of my life that it gives me great satisfaction to enhance this aspect of my children's lives. At any rate, here are some pics:

I already had on hand some oxblood grill cloth, advertised as suitable for vintage Fender amp restorations, which gave me the idea to do a throwback vintage Fender amp kind of look, sans actual tweed.

P.S.: Picture #2 above better represents the actual color.

[mattp]

Re: Throwback Sprite Variant

Very cool. Paint I assume? It looks like a vinyl wrap, excellent job.

[dstmbgh]

Re: Throwback Sprite Variant

Technical Info:
Inspired and informed by Paul Carmody's Sprite, I used two Dayton Audio ND90-8 3-1/2" Aluminum Cone Full-Range Drivers and Paul's contour filter.

Unlike Paul's Sprite, I used the Lepai LP-2020A+ Tripath Class-T Hi-Fi Audio Mini Amplifier with Power Supply. This amp has bass and treble controls, their maximum/minimum effect pictured here:

Paul states that he achieves "a nice 3 dB push between 70-90 Hz" by using a box volume just over 4 liters and a tuning of 63 Hz. With use of the amp's bass boost, however, I did not need to use the alignment to boost the bass, and chose instead to use a slightly larger volume -- 0.165 cu ft or 4.67 liters -- and a bit lower box tuning -- 51 Hz -- in order to provide better power handling in the 50 Hz region. I chose to still use Paul's contour filter because it provides a desirable flattening effect in the range between 400 and 2k Hz where the tone controls provide little to no effect.

Using 1" ID black polyethylene pipe for the ports enabled a port length for a 51 Hz tuning that comfortably fit the box dimensions, providing plenty of breathing room. I have not yet noticed any chuffing problems.

[dstmbgh]

Re: Throwback Sprite Variant

Thanks To:

Paul Carmody for the basic idea and the contour filter.

Chris Roemer for very helpful information regarding the box alignment.

Bolland83 for the idea from his published boombox build on an attractive way to mount the amp. He mounted his on top; I chose the front.

What would I do differently:

Only one thing that I can think of: I would order the amp without the power supply and get a 12V 5A one to increase the amp's output with lower distortion. I was pleased that the power supply that came with the amp was 3A rather than the 2A that I anticipated, but 1) the cord was impractically short -- only about 2 1/2 feet, and 2) might as well make use of the amp's full potential. I remedied the short cord length by ordering on ebay a 6' female/male extension cord, so as to prevent the need for a more bulky AC extension cord.

[dstmbgh]

Re: Throwback Sprite Variant

Very cool. Paint I assume? It looks like a vinyl wrap, excellent job.

Yes, it's paint. How nice it is that the big box stores now make available an 8 oz sample size of any color they offer for less than $3 -- just right for smaller projects.

More Build Details:

I used 1/2" mdf. Sealed with wax free shelac, then primed with interior oil based primer. The paint is latex flat applied with a small craft roller. Finished with Varathane Crystal Clear low-odor water-based satin spray. The faux Fender logo I printed from an online photo, cut it out, glued it on, and covered it with the spray clear coat. On a whim I looked into buying an actual vintage Fender logo on eBay -- $55 plus shipping. Ha, not gonna happen.

I lined three of the interior walls (the back, the top, and the side closest to the driver) with Walmart convoluted foam mattress topper.

[dstmbgh]

Re: Throwback Sprite Variant

Another small build tip: I used the Penn-Elcom H1008 Black Leather-Look Strap Handle, and it does not come with mounting screws. At my local hardware store I found that automotive chrome interior trim screws (phillips, oval-head) matched the strap's mounting hardware perfectly. FWIW.

[Wolf]

Re: Throwback Sprite Variant

Very Slick! I like it, Dave.
Wolf

[VegaMan]

Re: Throwback Sprite Variant

fantastic work. that grill cloth and color came out great looking.

[Paul Carmody]

Re: Throwback Sprite Variant

This past Christmas my youngest daughter was home from college and informed me that one of her roommates had moved out, and now, when she and her other roommate wanted to listen to music on something "better" than their laptop speakers, they had to plug into the TV. Any self-respecting speaker-builder-hobbyist father can't have that, now can we?

Love that part.

And yes, that's an awesome build.

[Uncle Bob]

Re: Throwback Sprite Variant

I like the simple little reveal around the speakers...very nicely done.

[dstmbgh]

Re: Throwback Sprite Variant

Love that part. (in reference to ...they had to plug into the TV. Any self-respecting speaker-builder-hobbyist father can't have that, now can we?)

Yeah, I suspect that many of you are like me: we zero-in on opportunities to build speakers like a heat-seeking missile.

Thanks, guys, for the compliments.

[dstmbgh]

Re: Throwback Sprite Variant

I like the simple little reveal around the speakers...very nicely done.

Thanks, Uncle Bob. For the grill frames I used the smallest outside corner trim that I could find, and then matched the radius of its roundover for all the other routered edge softening.

For the amp front panel cut-out, I tacked on some cleats to the backside of the front facade mdf piece to set the dimensions in order to use a flush trim router bit for easy clean cuts.

[bolland83]

Re: Throwback Sprite Variant

That looks great! Those amps look better mounted that way for sure, nice choice of hardware too :D Glad I could be of some inspiration, though I think your build looks cooler than mine.

[thekorvers]

Re: Throwback Sprite Variant

Awesome build. Very nicely done. So how do they sound?

[dstmbgh]

Re: Throwback Sprite Variant

Awesome build. Very nicely done. So how do they sound?

Today I took it over to Phil Bamberg's. He first tested it with OmniMic, and then we listened to some Keb Mo, fed straight from his DVD player via RCA plugs. OmniMic showed that it had substantial, non-boomy bass down to ~ 50 Hz, the kind of treble roll-off to be expected from a 3 1/2" full-range driver, and impressively flat response between. Just a little use of the treble tone control helped to lift the roll-off, and use of the bass tone control seemed non-essential (could be used per the listener's preference or the recording's need). Placed on the console between Phil's Series 6 speakers, we listened to the boombox and agreed that it was full-range enough, well-balanced enough, and sufficiently non-irritating/non-fatiguing to provide a listening experience that was genuinely enjoyable, even for one accustomed to audiophile sound. Are they high-end/audiophile, i.e., do they give Phil's Series 6 a run for their money? H3LL NO. But, especially considering its size and cost, is it ONE-H3LL-OF-A table top sound box? H3LL YES.

Phil suggested that a possible construction device that might further improve the fidelity (without additional components or eq) would be to angle the drivers outward slightly, thereby getting more treble energy dispersed into the room, helping to compensate a bit for the very close placement and high-frequency roll-off of the drivers.