2 'lesser quality' subs = 1 'good' sub? (1 Viewer)

[winniw]

Well, excuse my last post. I thought that we were building a subwoofer only. If this project is a center channel, then it would be best to flush mount everything, including the woofers, to avoid diffraction of the tweeter waves. Sorry.


Nick

 

[Mike Thomass]

so i will just order the speakers and parts today and cut the holes when they arrive. in the mean time, i will get some router bits and experiment with a custom jig and see if i can make it work and then decide if i need the special jig.


i planned to put two braces inside each cabinet. sufficient, yes?
as far as drilling holes into the braces goes, i mean, apparently they can be random size and location. but can there be too many holes? like, if i riddle the brace with holes, will it defeat the purpose of the brace? i assume the idea is to get as much open space as possible without weakening the brace.

as far as this polyfill stuff goes: one of the braces will be just below the bottom woofer i guess. so, i stuff a bunch of this polyfill between the brace and the top of the cabinet so it is in the space behind the woofers and tweeter, correct? how much do i stuff in there? if i get a 5lb bag, is half a bag too much? too little? are there better alternatives? do i need to do anything else internally? im assuming this polyfill stuff should be installed like home insulation. put in place but not matted down or compressed. correct?


please forgive all the questions, its part of my nature.

 

[Robert_J]

You need a 1/4" spiral upcut bit for the circle cutting. A 1/2" flush trim bit to smooth out the butt joints of the enclosure. Maybe a roundover bit if you want nice edges on the box. See my link to router bits above.


Two braces is fine. Window pane them. 4 holes so the middle looks like an "X".


It is important to stuff behind the woofers or put acoustic foam on the back wall behind them. This keeps higher frequency reflections from coloring the sound. 1 pound per cubic foot is average. It expand so much you will have to compress it to get it to fit. You can also buy $2.50 pillows at Wal-Mart and use those. I put a pair of them in each of the sonosubs I finished up yesterday.

 

[Mike Thomass]

i like the pillows idea

so i buy a few pillows, put 1 pillow in the top section, 1 in the middle, and one in the bottom to totally fill the cabinet? no polyfill needed? sounds easy enough.

if need be i can buy pillows and also the egg crate foam as well. youre the boss. tell me how you would do it.

 

[Robert_J]

The pillows are filled with polyfil. They are a little more expensive than raw poly but much easier to handle. No need to do the egg crate foam if you are using poly.

 

[Mike Thomass]

ok this heres my hopefully last batch of questions for at least a couple days:


once i put the two braces in, i will have three sections inside the cabinet. do i put the polyfill inside each section? or just the section where the speakers are?


if the fill goes in each section, are there any concerns about it covering the crossover? like will it act like insulation and cause the crossover to overheat? (i dont even know how much heat is generated by the crossover in the first place. im assuming very very little, but i dont know, so i ask)

 

[Mike Thomass]

im such a liar


ok, getting ready to order the parts i need. so im comparing the crossover schematic to the parts list for the dayton8, and it appears to me that the parts list is missing a 22uF cap (to combine with the 50 to make a 72uF cap)

i believe this is the exact part that i need. correct?

 

[Robert_J]

I didn't look at the other part numbers but non-polarized caps are the lowest quality. Next are poly caps http://www.parts-express.com/dayton-metallized-capacitors.cfm . The best are 1% tolerance caps http://www.parts-express.com/dayton-loudspeaker-precision-1.cfm .


Will it make a difference in the sound quality? I don't know. It would raise the price but I would go with a minimum of the poly caps but I'm a little nuts about my crossover parts.

And you are correct in comparing the diagram to the parts list. There is has been talk about this missing part for years but no one has ever updated the list.

 

[Mike Thomass]

the rest are non-polarized. see edit below

i will get all poly as you suggest. i will get a 60 and a 12 cause they dont have a 22 poly

i was looking at the 1% caps, they are crazy expensive. maybe later down the road i will start using the 1% stuff if my ears ever start picking up different qualities of sound.

do you recommend upgrading any of the other components?


EDIT:not all are non-polarized. the 12uF and 7.5 were polyprop already. not sure how i misread that.

so only the bigger caps were non-polarized. perhaps as a cost cutting measure?

 

[Robert_J]

Some say you don't get as much benefit with poly caps in the woofer circuit. Unless I'm going for uber cheap speakers, then I use poly throughout.

 

[Mike Thomass]

as an FYI to anybody who might be interested in this very same project-

the cost of the parts has gone up since that dayton8 project page was created.

it lists the parts at $156

my total looks to be about $255

so $100 more

about $38 of that is due to me upgrading some of the capacitors. about $9 or so is due to the parts list missing 2 caps

the price of the inductors has nearly doubled.

so that pricelist should total ~$217

 

[Robert_J]

Inductors = solid copper = $$$$


$50 per speaker is quite an increase but quality retail speakers have similar increases as well. Factor in shipping large speakers and your savings over retail is still pretty good.

 

[Mike Thomass]

Originally Posted by Robert_J

Inductors = solid copper = $$$$


$50 per speaker is quite an increase but quality retail speakers have similar increases as well. Factor in shipping large speakers and your savings over retail is still pretty good.

agreed

 

[Mike Thomass]

so im about to order the stuff from partsexpress.


in the item list, with the speakers it is asking me if i want to add screws (#8 screws) and speaker gasketing tape. for the tweeter, it is just asking if i want to add screws (#6 screws)

do i want that stuff? i thought the speakers would have come with screws and never even thought about gasketing tape.

 

[Robert_J]

The woofers used to come with screws. In fact, the 6.5" ones would come with 8 screws even though there were only 4 holes for screws. I'd use the extras in my tweeters.


That was a few years ago. I can't guarantee that the speakers will have screws now. Call customer service.


Gasket tape is also available at Lowes in the insulation section. Closed cell foam weatherstripping.

 

[winniw]

For a gasket, I always just spread some silicone caulk on the box, around the driver hole, about 1/16" thick, as smoothly as possible and smooth it with a wet finger-tip. Let it dry before installing the driver.


For screws, I always use socket cap screws, held in with T-nuts, so that I could take the driver off and reinstall it as often as necessary. If you use wood screws with MDF, here is what I would recommend. Do the first installation with only two #6 screws and be sure not to tighten them any more than absolutely necessary. If you have to open it up, to change something like the crossover or stuffing then you take out the two #6 screws and later, of course, you will use all six or eight screws for the final assembly. If you ever have to open it up agaian, use #8 screws for the reinstallation. Pre-drill all screw holes.


Nick

 

[Robert_J]

I use 3/4" plywood blocks (1" x 1") on the back side of the screw holes. They hold much better than MDF. In my opinion, t-nuts and bolts are overkill for regular speakers.


For my subs, I would use t-nuts if I didn't have the TC Sounds specific screws. Allen head and a very aggressive thread pattern.

 

[Mike Thomass]

Originally Posted by Robert_J

I use 3/4" plywood blocks (1" x 1") on the back side of the screw holes. They hold much better than MDF. In my opinion, t-nuts and bolts are overkill for regular speakers.


For my subs, I would use t-nuts if I didn't have the TC Sounds specific screws. Allen head and a very aggressive thread pattern.

so the regular screws wont hold or something?

what method should i use on this current project of mine?

any other little things like this i should know about?

you glue 1x1 blocks behind where the speaker screws will be and thats that?

 

[Robert_J]

They will hold just fine if you don't repeatedly remove the drivers. MDF is made from a find sawdust so when you compress it with a screw, it will turn to powder. Insert and remove the screw multiple times and there will be nothing left for the screw to hold on to anymore.


Yes, I glue 1x1x3/4 plywood or other hardwood blocks behind each screw hole. The screw is long enough to go through the MDF and catch in the actual wood block. It insures a good bite and I'm able to torque the screw down more. I would have mentioned it later in the build process. It was one of the last things I did during my build.

 

[Mike Thomass]

thanks robert

i placed the order yesterday with partsexpress. should be here tomorrow.
im very anxious to get going

12 gauge wire for the crossover is fine?