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Boomer1950

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

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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

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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?

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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.

 

 

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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.

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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 😅

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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.

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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. 

 

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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.

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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.

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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.

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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.

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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.

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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" 

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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

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

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

 

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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.

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The world has certainly gotten crazy since my last post.  My wife & I have been "sheltering in place" for the last 3 weeks.  Although I have plenty of time now to work on the box, I failed to buy the color paint before the quarantine started.  Being in the high risk group (senior citizen) has kept me from doing any shopping in-person.  I ordered some paint online from Home Depot, but it's taking them forever to ship it.  More waiting...

Some good news: The Stereo Integrity SQL-15 drivers have arrived in NC!  They're being shipped now, so it could come to me sometime soon.

I have finished the primer painting & sanding.  It looks pretty good to me.

77339369_Primerfinished.jpg.20bee67448b3b7dac5212aa9a81fd843.jpg

I haven't shown a picture of the finished grill attached to the front of the box with the magnets I embedded in the front baffle & the speaker grill - so, here it is:

30666207_Subwithgrill.jpg.3037883c8683ead361304f01080098af.jpg

The grill fits exactly as I had planned. I wanted the front face to show above the grill - it fits the same way at the bottom, but it's hard to see with the shadow there.  I intend to paint the box gloss black, but I've been wanting to have a two-color scheme - just to be a little different.  My current speakers are cherry wood & I thought a reddish brown accent would help the subwoofer match my other speakers somewhat.  In order for me to get some idea about how it would look I put yellow masking tape on the box where I intend to have the brown color.  The rest of the box with be gloss black.  I've already received the gloss topcoat that I'll apply to the entire box.

1557324897_subwithyellowstripe.jpg.4c5ad0e4bcd1c58925ca58d983da93c9.jpg

The stripe will go around the box - down the front, across the bottom & up the back.  After I paint the front baffle black with the brown stripe I don't believe you'll see through the speaker grill - as you can in this picture.

But now, I wait - for the paint on order & the arrival of the driver.  I'm very happy with the box at this point.

Everyone stay safe.  Wear a mask in public to protect the people you might meet.  Everybody needs to wear a mask in public.  Please.  Help protect the most vulnerable in society - those with underlying health issues & the elderly - like me & my wife!

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My driver from SI is arriving today!!  Nick called yesterday to let me know he was shipping it.  Obviously, the trip from Claremont to Burlington is a quick one for FedEx.

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The SQL-15 is here.  It looks great & I can hardly wait to hook it up - but I will wait a little.

1080387359_SIdriver.jpg.5520dbf4bc81c0ac6aa7f693ae5046f1.jpg378652621_DustCap.jpg.478961bd2411808f358fff99af1e3f7f.jpg

959080504_Sideviewdriver.jpg.c09f18f85a16d7ceb175a5a3e6f349f1.jpg

I added the plastic ties to give me something to hang onto.  I decided to see how it fits in the box.

1215552543_Speakerinplace.jpg.fcf3b7ed29064c32a05807afa7ecbaa7.jpg

It looked good at first, but then I noticed it wasn't going into the recessed driver support (inner baffle). I removed the plastic ties to make sure they weren't keeping it from fitting.  That wasn't the problem.  I assume the hole I cut is slightly small. This picture shows the edge of the driver sitting on the edge of the hole. 

1506694776_Speakerfit.jpg.85184484da978ddd7b3cae57def0eda2.jpg

My first thought is to hand sand around the inside of the hole & regularly check to see if I've made the hole big enough.  If you guys have any suggestions about how to handle this problem, they would be greatly appreciated.

 

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It's hard to believe, but I've finished my subwoofer - global pandemic be damned.  It seems like it took forever, but at some point you just have to stop.  Painting the box the way I did greatly increased the time it took. Leaving it square & painting it with truck bed liner would've saved me weeks.  No matter now.  Here's the finished box.

1175539833_FinishedBox.jpg.897b7a502675cc25c2768cc0882213c6.jpg

Just so someone will know I painted the bottom the same way... here's the bottom.

Bottom.jpg.b89e1862b7ac85d03cea6b19be928a5b.jpg

Because I have a dual 2 ohm voice coil driver, I wired it in series.  I ran one wire to connect the negative of one coil & the positive of the other voice coil.  Then the internal wire was split with the positive to one coil & the negative to the other. 

1432484371_Speakerconnections1.jpg.25b626b689a7d922d58c3c9e0ef2c3e3.jpg

387893396_Speakerconnections2.jpg.884d348c952ff4c525832a3a8ef5f61d.jpg

My concern over getting the driver positioned correctly so I could get the screws through the holes in the baffle was unnecessary.  With only a slight bit of adjustment the screws lined up & the driver was tightened into place.  Sliding the ports in & attaching them with 4 screws was even easier.  Voila!

863329525_FinishedSub.jpg.5109a7a16218f3261f72c1cb053d2185.jpg

I couldn't let a comparison with my former 100 wat12" Polk sub be overlooked.

872775522_SubvsPolk.jpg.27c2480a51c554823ca7820c57ff5e12.jpg

I took a picture of my entertainment center with the Polk sub in place.

474402453_PolkinPlace.jpg.24fcace1ba7ecf9cc5adc4ed90e5a662.jpg

Now with my new SI SQL15 sub with a 1100 watt Crown amp - with & without speaker grill:

1288544551_Sub-Grillinplace.jpg.2320bc946bb2f7e70ee87c72846a078b.jpg971272350_ModerninPlace.jpg.0e974662afa91cc9dacb7d22c91a61b2.jpg

It sounds absolutely wonderful, but I don't have a microphone I can use to give you any kind of performance data.  I'll get to that soon.

But I want to thank all the people who helped me get through this process - especially @dgage who helped me set up a visit with Nick at Stereo Integrity along with other good advice.  Everyone was so gracious to this old man that I can hardly express the extent of my gratitude

The picture of my MDF was taken on Jan 21.  On June 5 I hooked it up & listened to it for the first time. Worth every minute.

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Very nice!

My first sub was definitely not that well finished....

Glad you are enjoying it, but welcome to the rabbit-hole.  You may have just opened the Pandora's box we all have at one point or another...

JSS

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Thanks @maxmercy. I really wanted this to look nice, because the plan was to have it front & center in my living room - which it is.  My wife loves the way it looks & definitely prefers the "no grill" look.

But, the chances of me going further down this rabbit-hole - or opening Pandora's Box wider - aren't very good.  I can't imagine starting another project like this. I'm thrilled with the way it turned out, but it's a "one-hit wonder." Subwoofer building is very much a solo project & my wife & I don't do many of those anymore. It took what felt like an unnatural amount of time away from her to get this done.  The good news is we like doing everything together. 

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