Jump to content
Boomer1950

69 yr-old guy needs advice with 1st DIY sub

Recommended Posts

Good point, my testing was with sealed enclosures so ported or horns would indeed be different.  However, I agree with SME to go with thicker foam as I doubt 1” will do much of anything until you get over 1,000 Hz or so.  The following link goes over absorption of different products and thicknesses at different frequencies.

https://www.bobgolds.com/AbsorptionCoefficients.htm

Share this post


Link to post
Share on other sites

Thanks for all the feedback.  I'll be lining my box with 2" thick foam.

Learned something new yesterday - my ports won't be made from PVC pipe.  The flares & connector rings don't fit the standard  pipe. I've ordered port sections from Parts Express.  I already have the flares for each end.  

How much space do I need to have between the end of the internal port flare & the back wall?

Share this post


Link to post
Share on other sites
17 hours ago, Boomer1950 said:

Thanks for all the feedback.  I'll be lining my box with 2" thick foam.

Learned something new yesterday - my ports won't be made from PVC pipe.  The flares & connector rings don't fit the standard  pipe. I've ordered port sections from Parts Express.  I already have the flares for each end.  

How much space do I need to have between the end of the internal port flare & the back wall?

Common pvc pipe can be molded with heat to form flares like this: https://www.subwoofer-builder.com/port-flares.htm

The most correct answer without any conjecture or rule of thumb is to calculate how far the slug or slugs of air needs to move back and forth to produce the same sound pressure level at tuning. One can do that even with a program like winISD, using the port area as driver Sd.

 

 

Share this post


Link to post
Share on other sites

Another point for the foam lining: The internal cable to the connector won't rattle if it touches the walls.

Share this post


Link to post
Share on other sites
On 2/16/2020 at 2:06 PM, Boomer1950 said:

Thanks for all the feedback.  I'll be lining my box with 2" thick foam.

Learned something new yesterday - my ports won't be made from PVC pipe.  The flares & connector rings don't fit the standard  pipe. I've ordered port sections from Parts Express.  I already have the flares for each end.  

How much space do I need to have between the end of the internal port flare & the back wall?

In the design you posted here, you said the you would use ports that were 28" long including the flared ends.  For a 32" deep sub, that puts the port end 3.25" from the back wall.  I think that'll probably work just fine.

Share this post


Link to post
Share on other sites
2 hours ago, SME said:

In the design you posted here, you said the you would use ports that were 28" long including the flared ends.  For a 32" deep sub, that puts the port end 3.25" from the back wall.  I think that'll probably work just fine.

As long as there is none of the 2" foam on the back wall 😅

  • Like 1

Share this post


Link to post
Share on other sites

Time for an update...I finally glued the inner baffle to the front of the box.

315498897_innerbaffle2.jpg.fc66eaedc361fd0fc3a14ac56ab9e6b4.jpg252531912_innerbaffle1.jpg.61871e3e10e0882ac1872c1de1fda4ef.jpg

 

I received all of the parts for the ports.  I cut one 12" port section down to 10" for each port - one 10" piece + one 12" piece + 3" flare + 3" flare...  Each flare adds 3" to the length of the port, but only 2.5" counts as "port".  So, two ports - 28" long - are effectively 27" long ports. 

Ports.jpg.b541db35c8e231115a2be7ae59b1ac0d.jpg

I've started the foam installation by gluing 2" foam to the inside of the top - leaving gaps for the internal braces that will be glued to the top.

710153065_Topfoam.jpg.22a2cffe3668357efa007c11bec02cf1.jpg

I'm picking my moments to continue gluing foam to the box.  My wife really hates to smell it.  But, the 3M spray adhesive is excellent.  I used 3M's  "90" spray adhesive.  Spraying the box & spraying the back of the foam with adhesive makes a seriously tight bond. Now, more foam gluing.

Share this post


Link to post
Share on other sites

More foam gluing... a view from the top - you can see that I glued layers of foam together to create 3" - 4" thick foam on some walls.  All exterior walls have at least 2" of foam.

.foam.jpg.12c49a4ab217568af5489a5aae5b2664.jpg

Except for the wall that the ports will be pointing at..

.114933154_portwall.jpg.733f6ebb61de2c325da4633701ae67be.jpg

The ports fit tightly through the foam "tunnels" - top port path

825406465_upperport.jpg.ebf1b937c7d657def420fa44263bd0ae.jpg

Lower port path

1767725895_lowerport.jpg.7fa7e55f5bc359b83e55a29a22ed6d95.jpg

The internal speaker wire runs down a foam covered track in the middle of the box.  I added a little more foam on the wire path to prevent any rattling of the wire.

1852582337_wirepath.jpg.ac7e3c7b32b0d64c087779c73da73e92.jpg

I also drilled the hole for the SpeakOn panel connector.  

Speakon.jpg.372247f6a168589d0134212e92cb06cd.jpg

Next up?  I only have 2 pieces of the box left to attach - the top & the outer baffle.  The construction of the box is almost complete. 

 

Share this post


Link to post
Share on other sites

I need to make a speaker grill for my sub - to provide protection for the driver & to make the sub look a little better (in my wife's eyes).  I've read something about people using Neodymium magnets sunk into the sub face to attach the grill.  A few questions:

I used .75" x 1.5" pine for the 4 sides & five .5" dowels running top to bottom for protection.  It weighs 35 oz. before I mount the magnets.  Does this sound too heavy to use?  I've spent virtually no money making this frame, so suggestions to "start over" won't be traumatic for me.

618003614_grillframe.jpg.a3262e1f68f51abcca0a2c5e6f9ba8b1.jpg

307465960_grillonsub.jpg.0a1554fc57c184e36093fda16777b26e.jpg

I have a 1" Forstner bit to sink 1" magnets into the face & onto the 6 blocks on the grill frame.  I assume I should cut the holes just slightly deeper than the depth of the magnets & then cover them with wood putty & sand smooth.  I was planning to mount the same magnets onto the grill, but flipped to the other side than the magnets in the sub face.  I bought a piece of 36" x 36" grill cloth from Parts Express to cover the grill frame.  Am I moving in the right direction?  I've not done anything that can't be redone to make it better.  I only have time invested in this plan so far.

Thanks in advance for any feedback.

Share this post


Link to post
Share on other sites

I glued the top onto the sub.  Just the 2nd baffle left to attach.   Progress will now slow to a crawl as I start to sand - paint - sand - paint - sand - paint... until desired finish is attained.

Share this post


Link to post
Share on other sites

I just read that the driver I ordered from SI (SQL-15) will be at their facility in 30-45 days.  I hope to have my box sitting & waiting for a while, if all goes well.

Share this post


Link to post
Share on other sites
11 hours ago, Boomer1950 said:

I need to make a speaker grill for my sub - to provide protection for the driver & to make the sub look a little better (in my wife's eyes).  I've read something about people using Neodymium magnets sunk into the sub face to attach the grill.  A few questions:

I used .75" x 1.5" pine for the 4 sides & five .5" dowels running top to bottom for protection.  It weighs 35 oz. before I mount the magnets.  Does this sound too heavy to use?  I've spent virtually no money making this frame, so suggestions to "start over" won't be traumatic for me.

618003614_grillframe.jpg.a3262e1f68f51abcca0a2c5e6f9ba8b1.jpg

307465960_grillonsub.jpg.0a1554fc57c184e36093fda16777b26e.jpg

I have a 1" Forstner bit to sink 1" magnets into the face & onto the 6 blocks on the grill frame.  I assume I should cut the holes just slightly deeper than the depth of the magnets & then cover them with wood putty & sand smooth.  I was planning to mount the same magnets onto the grill, but flipped to the other side than the magnets in the sub face.  I bought a piece of 36" x 36" grill cloth from Parts Express to cover the grill frame.  Am I moving in the right direction?  I've not done anything that can't be redone to make it better.  I only have time invested in this plan so far.

Thanks in advance for any feedback.

If the holes for the magnets are drilled into the rear of the baffle that will reduce the amount of finishing work needed, compared to drilling the front side of the baffle.

Share this post


Link to post
Share on other sites

You may want to grab body filler if you’re going to paint it.  Much better than high-build primer or wood putty.  Looking good though.  And one key with the magnets is don’t mess up the polarity unless you’re using magnets on one side and steel discs on the other side.

Share this post


Link to post
Share on other sites
8 hours ago, dgage said:

You may want to grab body filler if you’re going to paint it.  Much better than high-build primer or wood putty.  Looking good though.  And one key with the magnets is don’t mess up the polarity unless you’re using magnets on one side and steel discs on the other side.

Agreed! Bondo works wonders... "putty and paint makes it what it ain't" 

Share this post


Link to post
Share on other sites

You guys convinced me.  I ordered some Bondo which should be here tomorrow.  I'm a big fan of 3M & I was glad to see that this was a 3M product.  I bet it works great.

I'm totally amazed that I have been able to use the Forstner bit (my first time using one) as well as I have.  I made a couple of practice holes on scrap MDF & then I jumped in.  I had 6 holes to drill on the grill that wouldn't be as critical as the holes on the outer baffle.  Those 6 holes went better than I could've imagined.

1514922127_grillmagnetsinstalled.jpg.334d1c02910db982d3225584cdcfcf9d.jpg

I installed the magnets on the grill "upside down".  That was done to allow me to install the magnets on the outer baffle with the counter sunk screw hole facing up - making the surface of the magnet smooth - no screw head sticking up as on the grill.

1644391409_magnetingrill.jpg.df768b3b8ed41c22eb3a2d192722b9be.jpg

I didn't show the holes in the grill, so here's one of a hole in the baffle.  Forstner bits work great, by the way.

1279792858_Forstnerhole.jpg.8c443d4d511dad1a49c160e5d8256c56.jpg

And, the magnet dropped into place.

2114827148_magnetsunk.jpg.6be1286e89c81732e32cb7a12184f9b3.jpg

If I can do this, anyone can.  Here are the 6 magnets in place on the outer baffle.

1804916498_bafflewithmagnets.jpg.7e0c40b582bcf25e7ab64c2e7f3ba6d2.jpg

Finally, the grill attached to the baffle using the newly installed magnets.  Works like a charm!

790763375_grillheldbymagnets.jpg.4dd9d0c3ab0b2f918a01c2b9396309b1.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Great work! Looks like you are putting together a quality first build. 

My first couple builds way back did not look this good.

 

Share this post


Link to post
Share on other sites

Just a quick update.  I have attached the front baffle, so all of the construction is over.  Here's a pic of the completed box with the grill frame attached by magnets. 

767165642_Subwithgrill.jpg.c4f036f43f0b7146c6a4213f96b9563a.jpg

It was at this point that serious sanding began.  I decided to take the edge off of the sharp edges of the corners.  I used a sanding block to "blunt" those edges.  After a lot of work I had barely changed the shape of the corners.  I knew after I used a router once that I would not be able to use a router indoors - the blizzard of dust would ruin my house.  I realized that using a round-over bit once the box was built was out of the question.  My wife & I are not able to pick up the box & take it to the carport to mitigate the dust in my house - remember, I'm 69 & my wife is 70.  I have no idea how much this box weighs, but I guess it's easily over 125 lbs.

I had never used a plane while working with MDF (hell, I've never sanded this much either), but I decided to give it a try - starting on the bottom of the sub in order to "hide" any screw-ups.  I liked the early results so I continued to the rest of the box.  I'm pretty happy with the results so far.

1782523396_sandedbox.jpg.546a50ff91d204d4709a024f5615b831.jpg  

Some more sanding to go before I start applying oil-based primer.  I took the sub off of the saw horses because I need to roll it around to work on the various sides.  Taking it off the saw horses was an exercise of "controlled fall."  No damage to the sub, the room, and most importantly, no damage to me.

  • Like 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...