From my take on it, there are definite benefits to having two woofers per side . More displacement woudln't be a bad thing. Having two in a push push configuration should allow the drivers to help control each other, shouldn't it? Also, wouldn't the equal but opposite force of the drivers help to reduce cabinet vibrations? I think that's pretty important when, in my case at least, I didn't really have in mind that I'd mount the Fonken on top of another speaker at some point; I've not come up with a way I'm happy with to solidly anchor the cabinets together.
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My original reasoning behind having the XO lower was so that the sub is non-directional (80Hz and below) and also because a lot of the HT gear has built-in filtering for XO's at 80Hz.
For a stereo pair, with double SDX-7s I'm into the cost of 4 drivers. I have to wonder out loud if I'm better off with a single sub (XO at 80Hz) based on one or two SDX-10's ?? This would mean a dedicated sub leaving the Fonkens to fend for themselves in terms of stands but I can live with that. It might also mean that I'd consider putting a plate amp in the sub whereas with the SDX-7 stand-mounted idea I'd feel inclined to use separate amps.
In terms of mounting the Fonkens on top of the subs, I agree that the dual driver approach lessens the worry about box vibrations from below. There must be several options for sitting the Fonken on the top of the sub box, such as a) simply plonk it on top (thin felt between?) and fix a flat metal bracket across the join on the back of the two boxes where it would be out of sight, b) spiked feet on the Fonken located onto the top of the sub box where there would be corresponding felt pads or something suitable recessed into the top of the sub box.
With a higher XO and drivers in the Fonken stand we're kinda talking 2-way's now aren't we!
Dave - when you say the SDX-10 needs a fairly fast turnover, are you referring to the need to filter off the top end so that it has a fairly steep roll-off where it XO's with the Fonken ??
For a stereo pair, with double SDX-7s I'm into the cost of 4 drivers. I have to wonder out loud if I'm better off with a single sub (XO at 80Hz) based on one or two SDX-10's ?? This would mean a dedicated sub leaving the Fonkens to fend for themselves in terms of stands but I can live with that. It might also mean that I'd consider putting a plate amp in the sub whereas with the SDX-7 stand-mounted idea I'd feel inclined to use separate amps.
In terms of mounting the Fonkens on top of the subs, I agree that the dual driver approach lessens the worry about box vibrations from below. There must be several options for sitting the Fonken on the top of the sub box, such as a) simply plonk it on top (thin felt between?) and fix a flat metal bracket across the join on the back of the two boxes where it would be out of sight, b) spiked feet on the Fonken located onto the top of the sub box where there would be corresponding felt pads or something suitable recessed into the top of the sub box.
With a higher XO and drivers in the Fonken stand we're kinda talking 2-way's now aren't we!
Dave - when you say the SDX-10 needs a fairly fast turnover, are you referring to the need to filter off the top end so that it has a fairly steep roll-off where it XO's with the Fonken ??
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I really like the aesthetics of the middle design. Looks like it would be a nice way to go if you needed to increase the volume of the cabinet.
Right now I've got mine crossed over at 85hz through the plate amp on my old Velodyne sub. Really helps take the burden of my little Trends class T amp. When it was running full range it would start sounding compressed as the volume increased and/or the music got more complex. The only drawback with the set up now is the sub. Ugggh, talk about one note, booomy bass.
I think I'd like to start out crossing mine at 100hz, and go from there. I'd like to go with an active crossover so I don't have to worry about rethinking the cap values when I try a different amp on the high end. I've thought about building one from scratch, I think I've got a handle on what I'd need, but there a couple of things that are psyching me out.
Right now I've got mine crossed over at 85hz through the plate amp on my old Velodyne sub. Really helps take the burden of my little Trends class T amp. When it was running full range it would start sounding compressed as the volume increased and/or the music got more complex. The only drawback with the set up now is the sub. Ugggh, talk about one note, booomy bass.
I think I'd like to start out crossing mine at 100hz, and go from there. I'd like to go with an active crossover so I don't have to worry about rethinking the cap values when I try a different amp on the high end. I've thought about building one from scratch, I think I've got a handle on what I'd need, but there a couple of things that are psyching me out.
strider75 said:
I don't know about one woofer controlling the other, but double the Sd means (IIRC) 1/4th the excursion requirements.
As long as you tightly couple the drivers, the active vibration cancellation reduced the amount of energy directly transmitted to the box significantly. For the sake of a number let's say in the ball-park of 90%.
As far as setting the Fonken on top... at the moment we have a set-back piece of 3/4" MDF. Next time i want to put in mating sets of spikes & cups. Also worth exploring is something like verity does. They have a slab of aluminum in an MDF sandwich with some sort of lossy material as the butter (see there are good uses for MDF)
dave
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Planet10,
I see you are a big proponent of using BB ply, eventhough there are MANY box designs out there that spec MDF. I know nada about the plus' and minus' of either of these materials when it comes to speakers but I use BB ply a lot in my other hobby (building telescopes) so I'm more comfortable working with BB ply - really I hate working with MDF. For general applications are there times where I should stick to the MDF spec or am I OK to sub in BB ply?
Sorry I realize it's a very broad question.
I see you are a big proponent of using BB ply, eventhough there are MANY box designs out there that spec MDF. I know nada about the plus' and minus' of either of these materials when it comes to speakers but I use BB ply a lot in my other hobby (building telescopes) so I'm more comfortable working with BB ply - really I hate working with MDF. For general applications are there times where I should stick to the MDF spec or am I OK to sub in BB ply?
Sorry I realize it's a very broad question.
planet10 said:
Ah, I had been thinking that the SDX7 was buying a lot of bandwidth to discard, but this makes sense.
Bigun said:
I remember reading somewhere that the point of equal energy higher and lower in frequency was around 300 hz. Ever since, I've thought maybe it makes more sense to build your 2-way with that as an XO point. Some OB setups and the Fonken+Woof designs are the closest I've seen to this. I wonder how a skillfully done dedicated 2-way closed box design like this might look.
Since I haven't Dave's skills, I thought the plate amp / dedicated sub was an option with a lot of flexibility. Higher re-usability as well, if you ever decide to try another design.
strider75 said:
If the sub is ported you could try blocking the port. A rolled up pair of socks or a tennis ball makes a nice, reversible mod. Uh, as long as you don't shove it so far in you can't grab it no more...
Ryan_Mc said:
Here is a very wide ranging answer
http://www.diyaudio.com/forums/showthread.php?s=&threadid=98834&highlight=material
There are places where MDF is useful, but you can usually find a sub (solids can be useful.
dave
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Like a Wet Paint sign
planet10
Very nice woodwork:
Um... The thing that scares me is the little guy with his hand less a few inches from your driver.
Anecdotally, It doesn't matter how many times they are warned, it seems like there is an attractive force between dust caps and little fingers. And tumbles happen. I can't count the times I've found dented dust cap.
At times I have resorted to wire grills until/unless I'm sure the fascination with touching the driver is gone.
planet10
Very nice woodwork:
Um... The thing that scares me is the little guy with his hand less a few inches from your driver.
Anecdotally, It doesn't matter how many times they are warned, it seems like there is an attractive force between dust caps and little fingers. And tumbles happen. I can't count the times I've found dented dust cap.
At times I have resorted to wire grills until/unless I'm sure the fascination with touching the driver is gone.
An update and a couple of questions
With a lot of assistance from Dave, I've decided on an enclosure and drivers. I'm building a cabinet similar to the Fonkenwoof with two 7 inch drivers per cabinet in a push push configuration. The cabinets are being made of 3/4" baltic birch ply, are approx. 1 ft^3 and are vented with a single rectangular port at the top of the enclosure which is 1" tall, 7.25" wide and 11" deep. Modeling the cabinets in winISD I come up with a -3db of 43.4hz. The crossover I'm using is one I bought as a kit from audio-kits.com; it's a Linkwitz-Reilly 4th order active crossover set at 120hz.
Now the questions:
Should I line the interior of the cabinet in any way? When I built the Fonkens I used 3/4" thick polyester batting on the walls; it is my understanding that this is done in a full range speaker to reduce reflections that may come back out through the driver's cone. Is that also necessary in a bass only design such as this? If the batting isn't needed, I was planning to spray the inside walls of the cabinet with sound damping paint to minimize cabinet resonance. Is this a good idea or not?
There is a driver brace in between the two drivers, meaning it runs from one side of the cabinet to the other width-wise. Should I place the brace so that it is not at an even fraction of the distance from one side of the cabinet to the other? Meaning, should it not be exactly 1/4 (or 1/3, or what have you) of the overall depth of the cabinet from the front wall of the cabinet? My thought is, as was the case in the Fonken cabinet, that if it were at an even interval in the cabinet it would tend to amplify a certain frequency. Am I thinking right?
With a lot of assistance from Dave, I've decided on an enclosure and drivers. I'm building a cabinet similar to the Fonkenwoof with two 7 inch drivers per cabinet in a push push configuration. The cabinets are being made of 3/4" baltic birch ply, are approx. 1 ft^3 and are vented with a single rectangular port at the top of the enclosure which is 1" tall, 7.25" wide and 11" deep. Modeling the cabinets in winISD I come up with a -3db of 43.4hz. The crossover I'm using is one I bought as a kit from audio-kits.com; it's a Linkwitz-Reilly 4th order active crossover set at 120hz.
Now the questions:
Should I line the interior of the cabinet in any way? When I built the Fonkens I used 3/4" thick polyester batting on the walls; it is my understanding that this is done in a full range speaker to reduce reflections that may come back out through the driver's cone. Is that also necessary in a bass only design such as this? If the batting isn't needed, I was planning to spray the inside walls of the cabinet with sound damping paint to minimize cabinet resonance. Is this a good idea or not?
There is a driver brace in between the two drivers, meaning it runs from one side of the cabinet to the other width-wise. Should I place the brace so that it is not at an even fraction of the distance from one side of the cabinet to the other? Meaning, should it not be exactly 1/4 (or 1/3, or what have you) of the overall depth of the cabinet from the front wall of the cabinet? My thought is, as was the case in the Fonken cabinet, that if it were at an even interval in the cabinet it would tend to amplify a certain frequency. Am I thinking right?
Re: Like a Wet Paint sign
These do have grills, but Tysen has been very good about not poking the dustcaps. He will go up to the speaker and put his ear to it thou....
We did have one incident where a "crash" caused the dustcap on a silver iris to get "dented" fortunately that was just a matter of screwing off the tweeter and poking it with a stick to make it as new.
dave
HK26147 said:
These do have grills, but Tysen has been very good about not poking the dustcaps. He will go up to the speaker and put his ear to it thou....
We did have one incident where a "crash" caused the dustcap on a silver iris to get "dented" fortunately that was just a matter of screwing off the tweeter and poking it with a stick to make it as new.
dave
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