Bottlehead Forum
Other Gear => Speakers => Topic started by: Deke609 on March 11, 2019, 06:49:06 AM
-
Hi all - I'd like to get my son set up with a pair of desktop speakers to go with his Quickie and Quicksand. DIY is a must - kit, or if need be, building from a schematic (the limiter here is that I don't have a tool for cutting large holes and would have to macgyver something to do the job, unless there's a cheap but effective tool/attachment commercially available).
Listening will be near field (2-5 ft), so I'm guessing sensitivity isn't much of an issue.
Suggestions?
Many thanks in advance,
Derek
-
For what it's worth, I had to cut some 6-8" holes in sheet aluminum recently, for my race bike. That was just beyond the capabilities of the fly cutter that fits on my drill press. I bought a circle cutting jig for a Dremel tool for about $12. It will do holes up to 12". I clamped the aluminum to a sheet of 3/4 plywood and the cutter had no problem zipping through both materials. The finish of the hole edge isn't as clean and perfect as a fly cutter makes, but it's perfectly serviceable for a driver mounting hole.
https://www.dremel.com/en_US/products/-/show-product/tools/678-01-circle-cutter-straight-edge-guide (https://www.dremel.com/en_US/products/-/show-product/tools/678-01-circle-cutter-straight-edge-guide)
-
https://www.parts-express.com/overnight-sensations-mt-speaker-kit-pair--300-706 (https://www.parts-express.com/overnight-sensations-mt-speaker-kit-pair--300-706)
https://www.parts-express.com/c-note-mt-bookshelf-speaker-kit-pair-with-knock-down-cabinets--300-7140 (https://www.parts-express.com/c-note-mt-bookshelf-speaker-kit-pair-with-knock-down-cabinets--300-7140)
https://www.parts-express.com/hitmaker-mt-studio-monitor-speaker-kit-with-knock-down-cabinet--300-7116 (https://www.parts-express.com/hitmaker-mt-studio-monitor-speaker-kit-with-knock-down-cabinet--300-7116)
https://www.parts-express.com/classix-ii-mt-bookshelf-speaker-kit-with-knock-down-cabinet--300-7112 (https://www.parts-express.com/classix-ii-mt-bookshelf-speaker-kit-with-knock-down-cabinet--300-7112)
For cutting holes and recessing driver flanges, a plunge router and the jasper jig get the job done pretty easily. If you aren't going to take up speaker building as a hobby, this might be a little more than you'd want to spend.
-
Thanks Doc and PB.
The Overnight Sensations look great and are priced right, so I ordered a pair. The ready-made knockdown panels will allow my 9yo son to build them with minimal assistance from me -- rather than the other way round.
-
Is there a sonic benefit to securing the crossovers to the inside of the the speaker cabinet? E.g., damping vibrations/resonances in the crossover components? If there is no real benefit, I'd prefer to fix rubber feet to the crossovers and simply have them sit at the bottom of the cabinet -- for ease of future removal.
I ask b/c the Overnight Sensation cabinets are pretty nice and it would be great to be able to reuse them in the future for an upgraded or entirely new speaker -- but that would be pretty difficult if the crossovers are glued to the inside base.
MTIA,
Derek
-
Let me know where you end up with this. I built a set of OS a while back and agree that it'd be preferential to have a cabinet I could upgrade without yanking the drivers out.
-
Don’t glue them, screw them down or just leave them gravity mounted. Probably, external placement is the best way to gain a sonic benefit. This gets the components out of the way of the woofer back wave and you regain the enclosure volume that the design was probably intended to have.
Jamie
-
Thanks Jamie.
"Gravity mounted" - I like that. Makes me feel like I'm being all science-y.
Intrigued stranger: How are those crossovers mounted?
Me: They're gravity mounted.
IS: "Gravity mounted"!? Isn't that just a fancy way of saying you were too lazy to fix them to the speaker?
Me: Why no. In fact, we tested our approach both theoretically and experimentally.
First, we considered what "in theory" should keep the crossovers from accelerating out of the cabinet using Newton's three laws of motion. You will
be familiar with the first of those: an object at rest or in motion will stay at rest or in motion unless acted upon by a contrary force. The other two
provide: Vector sum of F = ma , and FsubAB = −FsubBA
Based on these merely theoretical equations we determined that the only value of F (force) that yields a = 0, is 0, unless of course you know
of a way of reducing the mass of an object to zero -- which is fanciful. Thus, theory predicts that if you don't want your crossover accelerating out
of your cabinet, don't apply force to it. Absent such a force, it will stay put.
Second, we conducted empirical testing. Why? Because, as any good designer will tell you (e.g., Paul Joppa), a theory is only as good as the
soundness of its assumptions. So we beat the hell out of the thing. And sure as shit, Newton was right: no force is definitely the way to go.
So, yes, "gravity mounted". Please don't bump the speakers.
-
Or, you could just screw them down.
Jamie
-
Hah! Yeah, I think I'll try - but the largest opening is pretty small. Going to be tricky getting my hand in there with a small screwdriver. And I'm not sure about screwing into the base of the cabinet. It's only 1/4 inch ply. Maybe even a bit smaller. So gravity mounting may be they way to go. :)
-
Glue small 1/2 inch plywood blocks on the enclosure floor in positions that will engage the xover
boards and screw down to those. I’m serious about external mounting though. It is the best way to gain an audible improvement, short of upgrading the xover components. Paul Carmody designs some great speakers and they are worthy of upgraded xover components.
Jamie
-
Smart! that's the ticket. Many thanks.
External mounting make sense - why have the crossover components subjected to vibrations and percussive forces? But these speakers are for my son who, being 9 1/2, and not unlike how his dad was when his age, is sure to knock them over, spill stuff on them, and just generally abuse them, albeit accidentally.
-
If you can remove the boards through the woofer hole, pull them out and screw them to the small wood blocks while outside the enclosure. Then apply glue to the bottom of the blocks and replace them in the enclosure. Later, if you want, you can unscrew them and remove them to make mods or mount them externally or whatever.
Jamie
-
Even smarter! Now I feel foolish for not having seen this. Many thanks Jamie.
Complete tangent -- Jamie: did you assemble speakers (from schematic or kit) for your Stereomours? If so, what did you build and what would be your recommendation?
cheers,
Derek
-
It’s all about your room, your listening style( near-field, semi near field, etc.) and other gear that you might want to use ( one sub, two subs). With 3.5 W you need something fairly sensitive but in a small room like mine (10 x 15 x 8 ) 90 dB and up works pretty well. You can see a picture of the MTMs I’m using now on a post in this board. I designed these with some help from friends (I selected the drivers and enclosure volume and they helped me with the Xover).I listen semi-nearfield with actively crossed subs and I find these to be really good, but what I hear may not be what you hear so YMMV, as they say.
Jamie
-
Many thanks Jamie.
-
Derek,
There is a design by Michael Chua that looks interesting to me. It’s a coax based on the Eminence Beta 10CX. An interesting driver that you screw a one inch compression driver into the pole piece. You can use any one inch CD that has that thread pattern. Michael chose a Selenium
220. The enclosure is a simple, 1 cubic foot box and I believe the Beta is surface mounted, which would not require routing precise rebates. It looks like it comes in around 94 dB, so plenty sensitive. This might be a good design for small rooms and it can be built fairly inexpensively ( around 270.00 for the drivers plus your cabinet material and Xover parts). You can find the details on the Ampslab site. Michael is very helpful and responds quickly to email.
Jamie
-
Thanks much Jamie. I will check it out. But I must admit that I only understood the last half of your post! "Compression driver" - huh? Much to learn!
94dB sensitivity sounds pretty appealing.
cheers,
Derek