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Old 16th March 2011, 08:55 PM   #11
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by cricha5 View Post
I've now looked at the EL70, and it looks perfect. Thanks. Decision made. Will try baffle step correction only if needed and no Zobel network. Done.

Now for the enclosure. I really do like the last design posted and I think I can build it, but I don't understand the theory behind it. What is the baffle that divides the driver for? Why not just use a port?

After a failed theremin experiment, I will no longer build something without understanding it completely first.

If you're talking about the horizontal tapered piece with holes that connects with the driver, or the short vertical piece below, those are braces. One of the theories behind most of Dave's designs is couple as many adjoining and opposing panels as possible to brace the enclosure for rigidity. Others include use of low mass/stiff materials (i.e. Baltic Birch or other high density plywood) rather than MDF, concrete, Corian, etc., and the general avoidance of loading of enclosure panels with additional mass.

Note that venting is accomplished by narrow slot(s) rather than a single larger diameter round port of equivalent CSA. Even on enclosures as small as this, we've noted improvements on past builds with the extent of bracing as shown, as well as with slots vs round ports. Also note that the full width panel defining the slot vents and full depth center spacer contribute to overall bracing.
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Old 16th March 2011, 09:06 PM   #12
cricha5 is offline cricha5  United States
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Great. Questions answers. Thanks. On to planning! I'll post when they are done.
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Old 16th March 2011, 09:11 PM   #13
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The "baffle that divides the driver" is a holey brace. It braces the cabinet, and more importantly shunts energy from the driver to the back (& sides) of the box thus sharing the energy across way more panel.

The slot-vent is at the bottom of the box. The high aspect ratio makes the box less sensitive to dynamic changes in the T/S parameters (ie tuning of the box)

dave

Edit: Chris beat me to it.
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Old 16th March 2011, 09:48 PM   #14
AEIOU is offline AEIOU  United States
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Quote:
Originally Posted by cricha5 View Post
arpeggio-loudspeaker makes a good argument for a Zobel network for SET amps.
I wonder how it affects the sound. Does it sound better with a Zobel as opposed to without? Easy enough to do though. In my experience Zobels kind of soften, attenuate the upper frequencies, which is not a problem if you are low passing a driver. Maybe I'll have to try it with some of the full range projects I've got going.
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Old 17th March 2011, 03:34 AM   #15
cricha5 is offline cricha5  United States
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Just picked up some wood from Lowes. I got a few peices of 3/4 inch, 7 inch wide pine. I modified the design for the fewest cuts possible. So now it'll be (LxWxH) (7x8.5x12):

4 Sides 7 x 12
2 Back 7 x 12
2 Front 7 x 10.25
4 Bottom/Top 7 x 5.5
2 Lower Brace 7 x 5.0
Top Brace wait for speaker
Middle Brace ??

See all the 7's. Means I only have to cut the boards one way. Made my last sealed speaker box for a 3'' HiVi like this and it worked like a charm. The joints will just be but joints since I only have a band saw in the grad student machine shop, a workmate and a dremel. I generally put a few screws in too. Glue is the bane of my existence. My skills come from working on cars in Louisiana. Glue doesn't work here with the heat and humidity. Drill it, tap it, screw it. I wish I could tap wood... I've been using those inserts you screw in. They work ok... I'll use poly fill instead of gluing on carpet since I've got a big bag of it right here.
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Old 17th March 2011, 02:01 PM   #16
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You did actually measure the width of your boards? You probably bought "1x8's", which are usually 3/4"x7.5". Also, if the boards are imports, particular from Asia, the lumber will be in standard metric sizes and give odd Imperial measurements.

Bob
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Old 17th March 2011, 05:32 PM   #17
cricha5 is offline cricha5  United States
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Yes, that's right, 7.5. The width measurement is no at all critical when cutting like I am, just as long as they're all the same.

We import wood?!? Besides being cheap, I got pine because I thought it might be local. You can't swing a cat without hitting a pine tree here.
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Old 18th March 2011, 01:24 AM   #18
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Quote:
Originally Posted by chrisb View Post
Second the suggestion on EL70 / CHR70 for nearfield - BSC not likely to be required.

Box as small as attached would make a pretty decent little desk-top and not a hard build

http://homepage.mac.com/tlinespeaker...map-231009.pdf
BSC is still needed near feild - I was incorectly told that I wouldn't need it and mesured and found that baffle step correction was needed. CHR-70 I use and recomend, however I do use 2x10" subs crossed at 90Hz and bass is quite light without them.
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Old 18th March 2011, 01:37 AM   #19
TerryO is offline TerryO  United States
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Quote:
Originally Posted by AEIOU View Post
Baffle step is not necessitated by your distance from the loudspeakers. More by their distance from nearby boundaries, significantly the rear wall.
Why would you need a Zobel? Do you plan on crossovering them? Or are you just trying to hold down the rising impedance for your amplifiers sake?

Just a quick note, if the speakers are anywhere except built into the wall you will have a degree of Baffle Step.

The Baffle Step frequency is dictated mostly by the size of the baffle itself and rarely has much to do with boundary distances.

For OB boundary issues see:
http://www.diyaudio.com/forums/multi...-new-post.html

Best Regards,
TerryO
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Old 18th March 2011, 07:27 PM   #20
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by cricha5 View Post
Yes, that's right, 7.5. The width measurement is no at all critical when cutting like I am, just as long as they're all the same.

We import wood?!? Besides being cheap, I got pine because I thought it might be local. You can't swing a cat without hitting a pine tree here.


oh my yes "we" import wood - a lot more than you'd think, and sometimes our own, but your lumberyard or building supply dealer should be able to confirm country of origin

Take it from someone residing in a province with still huge remaining natural reserves ( take a day-time flight from Vancouver to Prince George, or even drive the "short" highway from Port Alberni to Port Hardy and ask yourself, OK, were are all the "disappeared" forests?), depending on your proximity to either coast, don't be surprised to discover that raw logs are exported for processing and re-imported with "value added" - all at the cost of domestic jobs & tax revenues. But let's not forget these practices were developed by visionary economic geniuses, and sanctioned by politicians and bureaucrats with only our own best interests at heart.

oops, rant off


Bob's right - confirm the actual sizes of your dimensional lumber
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