Full range in the face. Advice please.

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I just finished making a single ended amp for my computer and I'd like to make a matched set of speakers for it. http://www.diyaudio.com/forums/tubes-valves/184965-two-amps-done-done.html I think I've settled on the Fostex fe126en, but there are too many enclosure,baffle step and Zobel options. The way my computer is set up, the speakers are around 3 feet from my face, which makes me think I'll really need baffle step correction. Or am I thinking backwards about that? Also, I have recently learned how to do simple things with wood, but I am definitely not skilled enough to take on building a horn enclosure. I was thinking either a version of the arpeggio from the articles here on diyaudio or the bass reflex enclosure on the fostex datasheet.

Any advice would be appreciated. Thanks.

Oh, and I listen to all kinds of music, from David Bowie to Bach to Dethklok.
 
frugal-phile™
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The factory enclosures have a rep (deserved) for not being very good. The 126 reflex looks particularily uglu (bottom curve). The other 2 are 4 litres tuned to 105 or 125 Hz.

I'd build the last one with a high resistance vent to flatten the peak and extend the response -- i suspect the vent would need to wrap around the box.

I'd suggest that the FH3 is probably the smallest box that will get decent bass out of these (well maybe a FH1 Level 0 or a modified Buschhorn 1, they are marginally smaller, a lot more complicated, and don't work as well)

To aid your woodwork, flat-paks of the FH3 are becoming available.

dave
 

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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?


I just finished making a single ended amp for my computer and I'd like to make a matched set of speakers for it. http://www.diyaudio.com/forums/tubes-valves/184965-two-amps-done-done.html I think I've settled on the Fostex fe126en, but there are too many enclosure,baffle step and Zobel options. The way my computer is set up, the speakers are around 3 feet from my face, which makes me think I'll really need baffle step correction. Or am I thinking backwards about that? Also, I have recently learned how to do simple things with wood, but I am definitely not skilled enough to take on building a horn enclosure. I was thinking either a version of the arpeggio from the articles here on diyaudio or the bass reflex enclosure on the fostex datasheet.

Any advice would be appreciated. Thanks.

Oh, and I listen to all kinds of music, from David Bowie to Bach to Dethklok.
 
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.
 
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.
 
frugal-phile™
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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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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.
 
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.
 
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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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/tlinespeakers/FAL/downloads/mMar-Kel70-1v0-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.
 
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-way/172806-flat-not-correct-stereo-system-new-post.html

Best Regards,
TerryO
 
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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