Sanity check sonotube sub DIY project

[HMenke]

Well, Thomas, I guess I had to dive inside the tube anyway so how's this look? Let me know because I definitely don't want to foul this up.

Pretty much you can now see down to the end cap. I pulled out an awful lot from way down in there - it grows in volume when you fluff it.

[WillyD]

I don't know much, but that looks good there, in the last pic. I would think no more than that is necessary along the inner wall (concerning the thickness anyway).

[HMenke]

Thanks WillyD. Y'know, I've planned and researched every aspect of this project but when it came to the fill I just spaced it off. ops:

Here are a couple of pics of the legs. I used banister studs for the upper end of the legs. This lets me attach to the bottom plug with a blind hole (no need for sealing the screws).

[ThomasW]

The standard approach is to line with a couple inches on the walls of the enclosure

This is a 20" dia tube, 2.5" foam, and an opening for a 6" port.

[HMenke]

I see. Would you adise that I remove of the Acousta-stuff and switch to foam, or forge ahead withthe poly? Other than easier installation, are there any other benefits of the foam? Are there any detriments to the poly?

[ThomasW]

The Acousta-Stuff is somewhat more absorbent than the generic PE foam. So using a lot of it will mess up your box model. It's fundamental use is for stuffing sealed boxes. I don't know of any way to get an even layer around the tube.

Might just drop by the local home center store and grab a roll of fiberglass insulation. Pretty cheap and the best thing available to absorb bass frequencies (nasty to work with though)

[HMenke]

I'm not in a hurry - have to travel this week. It wasn't too much trouble to pull the Acousta-stuff out. Now I am back down to the tube with a bit of fuzz here and there. What is a good source for the foam in your photo above? Edit: never mind, found it at PE.

[HMenke]

What characteristics are important for the foam? Open cell and...

Wondering if I can pick up something suitable locally from a fabric store.

[ThomasW]

There are differences between acoustic foam and the stuff sold at the fabric stores. There are absorption coefficients available for the acoustic foam, I have no idea what they are for the fabric stuff.

[HMenke]

Alright, I've got the 2.5" acoustic foam on the way from PE. Due to traveling for work it'll be at least a week until I get more build time anyway. Wish I knew what to do with this big 40+ dollar bag of Acousta-stuff. I'll probably hang onto it in case I get an urge to make a sealed sub or some full-range speakers.

In the meantime I am studying rumble filters. This one looks pretty straightforward:

http://www.users.bigpond.com/bcolliso/active-filter.htm

Anyone with experience building / using it?

[WillyD]

Alright, I've got the 2.5" acoustic foam on the way from PE. Due to traveling for work it'll be at least a week until I get more build time anyway. Wish I knew what to do with this big 40+ dollar bag of Acousta-stuff. I'll probably hang onto it in case I get an urge to make a sealed sub or some full-range speakers.

In the meantime I am studying rumble filters. This one looks pretty straightforward:

http://www.users.bigpond.com/bcolliso/active-filter.htm

Anyone with experience building / using it?

You could also use it if you wanted to make some sealed sats, right?

[HMenke]

Yes, that is also on my "to do" list! :B

[ThomasW]

Charles98 is working on a rumble filter....

[HMenke]

I've seen some of his photos - he did a nice job with it. I heard he is going to make a how-to page.

The challenge to me is not wiring up the filter so much as finding an open frame power supply that doesn't cost too much but has low enough ripple to do a good job. It isn't worth the extra complication to me to make the power supply too.

[HMenke]

back on track

Alright, I have now fully recovered the project from my bone-headed installation of the wrong dampening material. I cleaned out the last of the fuzz with lacquer thinner and got back down to bare tube for installation of the acoustic foam.

Thomas, I made a little box for side-mounting the binding posts, but after getting off track I decided to abandon the box to save time attaching the box and working the carpet around it. I just went ahead with bottom-mounted posts. It was just fast and easy which is just what I need at this point.

I am fooling around with ideas for low-effort finishing. I am experimenting with a spray-on truck bed liner called Plasti-Kote. So far the results are promising. It gives a semi-flat textured look. I put one coat on a scrap of wood and tomorrow I'm going to hit it again to see if I can get complete hide on the MDF surface imperfections. I just want a uniform textured look.

[ThomasW]

Oh man you need to start over the little peaks in the foam aren't all lined up. There needs to be a completely symetrical pattern otherwise the SQ is messed up.... :wink:

Wise choice to use the bottom mounted inputs. A fraction the work of the little box. And they make for a nice tidy installation, with nothing sticking out to bang the wall as you move the sub around.... :T

[chasw98]

That is why I bought my foam with triangles so I could line it up easier. I could hear the difference :rofl: With triangles lined up I could hear the deepest notes lining up in the troughs of the triangles.

[HMenke]

Har, har, laugh it up fellas! :P Seriously I'm just really glad you guys have my back and stopped my madness before it was too late! The foam was tricky to install reaching way down in there, but I "got 'er done" and I am ready to close this thing up and never see it again!

One thing did work out pretty well: the inside circumference of the 24" tube was just slightly less than (4) * 18" W pieces. I was able to fit all four in without needing to cut any lengthwise.

[HMenke]

How do you select the nominal frequency of a Linkwitz-Riley active high pass rumble filter, which has a rolloff of 24dB / Octave?

Also how do I model this in Unibox? I see it has this feature but an FRD file must be created.

[HMenke]

sub finishing method

I've completed my experiments with spray-on truck bed liner and I'm pleased with the results. This material gives a slightly sand-pebble finish, very uniform, that hides minor imperfections in the substrate. The overall effect is sort of semi-gloss/semi-flat. At some angles it looks flat while at other angles it looks slightly shiny with the pebble texture breaking it up. Overall it is very attractive and low-effort. Plus it will obviously be pretty durable and resistant to chipping. It takes two coats; the first for overall coverage and the second to achieve good uniformity.

Here is a picture of my scrap test piece. It's hard to get depth of field with my camera but you can see the texture in focus toward the front part.

Edit: photos of the type of material that comes in the spray can. It is also available in 1-gal cans for roll-on application.

[ThomasW]

Yep that looks pretty good, and all your buddies at the truck stop will be proud.... :B

How do you select the nominal frequency of a Linkwitz-Riley active high pass rumble filter, which has a rolloff of 24dB / Octave?

Good question....

I'd be tempted to use sockets for the frequency setting components then experiement. If you look at the Sidewinder link on Collo's filter page you can see how he plotted the excursion w/wo the filter he built.

To create a frd file you manually 'trace' the plot (SPL Trace) you want to import.

[HMenke]

Yep that looks pretty good, and all your buddies at the truck stop will be proud.... :B

Just wait'll they get a look at my port flaps! :B

[ThomasW]

Now that's the true spirit of things...... :T

Have you looked at Rod Elliot's subsonic filter?

http://sound.westhost.com/project99.htm

[collo]

I normally caution against DIY grilles across ports because of the dreaded "grille slap", but in your case I'd be concerned about "flap slap"..... :takecover:

[HMenke]

Yes, I think that's the one that Chuck used. I haven't decided which one I'll use. In the meatime I am trying to figure out what the corner frequency should be: 1) equal to the port tuning 2) higher than the port tuning 3) lower than the port tuning.

The Unibox page has this info about the FRD import feature:

FRD file import feature added. You can now import an active filter correction function and see the resulting frequency response, cone excursion, port air speed and much more. A typical design approach would be to simulate your box in UniBox and export the frequency response as a FRD file. Import this into the Linkwitz Transform program found on the FRD consortium Web and simulate your active correction filter. Export this correction as a FRD file and use the new import feature of UniBox to see the final results.

I went to http://www.pvconsultants.com/audio/eq/linktran.htm and downloaded the Excel file. I was able to export my FRD from Unibox and import it into Linkwitz Transform Beta. I selected "Use FRD input model" and then "Enable Subsonic Filter." At this point you can select up to 2nd order with a Q of 5 (no orders higher than 2nd are modeled) and your target corner frequency Fc. That's as far as I've gotten because I'm unsure of the effect of the filter on the responce curve. It's not clear what some of the curve labels are such as "LT correction" and "Speaker".

My sub FR and driver excursion modeled in Unibox look like the attached graphs.

[HMenke]

zeroing in on Fc

I gave up on Linkwitz Transform Beta and went over to the filter modeling in WinISD.

I couldn't really get the FR curve in WinISD to precisely match the output of Unibox, but close enough I hope. The EQ/Filter function in WinISD is pretty cool. You can model a 4th-order Linkwitz-Riley active high pass filter. I am toggling between 12 Hz and 13 Hz. 13 Hz prevents hitting Xmax at all, but 12 Hz gives more extension and just barely allows hitting Xmax at 700W. The chances that I will play anything at 700W are about zero, so I am leaning toward 12 Hz.

Here are the SPL and Cone Excursion plots from WinISD with the filter enabled (graphs 1 and 2) and disabled (graphs 3 and 4)

[collo]

you beat me to it!

I've knocked up a small app to show changes to cone excursion and SPL as the filter frequency is changed.
Just move the scroll bar to see the changes

It's still pretty primitive - no save or autoscaling, but I've estimated your sub from the graphs you supplied, and used this as the default data.

As you've found 12 to 13hz is what you need

http://www.users.bigpond.com/bcolliso/filter-beta.exe

[HMenke]

you beat me to it!

I've knocked up a small app to show changes to cone excursion and SPL as the filter frequency is changed.
Just move the scroll bar to see the changes

It's still pretty primitive - no save or autoscaling, but I've estimated your sub from the graphs you supplied, and used this as the default data.

As you've found 12 to 13hz is what you need

http://www.users.bigpond.com/bcolliso/filter-beta.exe

Wow, now that is very cool! Very nice feature - makes it easy and quick to find the right corner freq. Nice job!

[ThomasW]

Wow, talk about great customer support!

Ask a question and you get a free custom application written ..... :B

[HMenke]

What I like about collo's application is how it allows you to adjust the corner frequency in real time and instantly see the effect on all graphs at the same time. It couldn't be simpler to use or more informative for "what if" scenarios. ;x(

[collo]

I'm glad you liked it!

Once it's cleaned up up a bit more (error checking, better data entry etc, etc), I'll make it available from my filters page

[HMenke]

getting close

I finished "painting" with the spray-on truck bed liner and its looking good. The stuff turned out to be a little trickier than expected on larger areas. You have to work fast and keep moving to get an even coverage. But once it dries, errors tend to fade away. It won't hold up to close critical inspection, but at a normal viewing distance I am happy with the result. I used more cans than expected as well. I bought out the supply at my local Wal-Mart (one can) and the other local store had none. They showed nine in stock but "couldn't find them" in the store room. I ordered two more cans online and used them up last night, still not done. So this morning I went to the next town south and found two more cans to wrap it up. Total needed: five.

I installed the grille sockets in the top cap to hold on my DIY port grille. Last weekend I finished it. I got the fabric stretched "tonight like a toiger" :B and it looks pretty cool. I'll post pictures with the final completion.

When the bed liner is good and dry, the next step is carpet. Then I am going to haul it into the HT room and install the woofer, binding posts, and the bottom floor plate. Then it will be done!

[HMenke]

Done!

Ready to hook up, test, set levels, and EQ on Sunday!

Thank you Thomas, Steve, Chuck, Ben, collo, and everyone else who jumped into this thread with help and advice. I could not have accomplished this mission without this forum and you guys! :T

Pardon my construction dust in the woofer shot. Amazing how it shows up on camera. I will be back at some point to post FR curves pre- and post-EQ.

[chasw98]

Looks good! You might want to just let it play at a low volume for an hour or so to "exercise" the driver before hitting it with sine waves and sweeps.

[ThomasW]

Looking good Henry ...... :T

Can't wait for the first performance report ..... :B

[HMenke]

First impressions

Thanks again Chuck and Thomas - I feel like this is as much your sub as mine!

Woke up early this morning despite the time change - couldn't wait to give the new sub a listen. Chuck you make a good point about break-in, so all I did for set up today was calibrate the level to match the other speakers. Of course I also defeated the parametric EQ settings for my old sub (Paradigm PS-1000) in my Behringer DSP1124P.

I built this sonosub mainly because I like movies and I wanted to get more depth and transient impact. I was hoping for - but not really expecting - better control and clarity. Well, what has surprised this morning is how this thing sounds with music! I never listened to music with my old sub turned on because I found it muddy, boomy, and therefore distracting even at low levels.

Well, today I turned on HDNet and heard "Chick Corea: Rendezvous in New York" in Dolby Digital. He was playing with an acoustic ensemble of piano, trombone, sax, drums, and upright bass. Astonishing! This sub does not call attention to itself, but man does it reproduce the music! The deep bass notes are just "there" and they are not localizable. The sub is behind me to the left, but the music is firmly anchored to the soundstage in front. Hearing accurate, deep percussion for the first time was, for me, a revelation. h:

I also have the Rives Audio test CD. There are sample music tracks on this CD that you can use to subjectively evaluate your system after you are all done with test tones and measured tweaks. I remember a few months ago, after I had EQ'd my old sub for the first time with the Behringer, I popped in this CD expecting great results. I was really disappointed in how bad and distorted it sounded. The old sub just couldn't cut it. Well, as I'm sure you can guess by now, the sonosub is stellar with these tracks and it hasn't even been EQ'd yet!

There is music on the Rives Audio CD with deep bass content, some of it percussive and highly dynamic and transient. This sonosub (and let's not forget to also give credit to the mighty RLp-15 driver and the strong, silent Samson S700 amp) handled everything without strain and delivered a captivating experience. I am totally hooked on listening to music with this sub - I feel like I need to go back through my favorite CDs and listen to them all over again for the first time!

Next I put in a DVD of the first chapter of Toy Story 2; with Buzz Lightyear blasting around, there is some great bass in this part of the movie. It sounded great, without boominess yet with more substantial presence down low. I got a kick out of laying on the floor to watch the driver in action. It was hardly moving - hard to imagine what it can do at even half its maximum output. 8O

I can't believe what I ended up with for the money. My hat's off to the guys in this hobby who pioneer high-performance DIY projects like this and share their knowledge with others. The rest of us are just riding along on your coattails, carried to new levels of audio performance that would otherwise be unobtainable commercially or affordably. Not to mention the sense of accomplishment and pride that I take when I look at - and listen to - this awesome sub.

Henry

[chasw98]

Henry:
The same thing happened to me. I am listening to a lot more music than I used to with my old setup. It is so much more pleasant. Wait till you dig in and pull up all your old music. It will sound new and fresh again. All the thanks goes to Thomas. I am just passing on what he has taught me. ;x(

Chuck

[HMenke]

Alright, I am back after completing the dreaded "spouse initial demo", i.e. "OK, so let's hear this thing you've been obsessing over for the past month."

We sat down and she said, "Now you know I don't have the 'Golden Ear', so I'm not sure I'll be able to tell any difference." Voice inside my head: "Uh-oh!" :roll:

We demo'd a DVR recording of the aforementioned Chick Corea ensemble, followed by Toy Story 2 Chapter 1 again. Guess what? She digs it! At one point during Toy Story she actually laughed out loud and said "I can feel the couch moving under me!" Keep in mind this was not cranked, probably about 90dB average program level.

Her summary comments: "You can definitely feel it more, but it's not really louder. It seems like it comes on and goes off when it's supposed to. It really adds to the experience, but it never gets distracting. Sometimes I didn't like the old subwoofer when it starting booming and vibrating. Don't you think we have a really great home theater? Why would we ever go out to the movies now?"

I tell you, it doesn't get any better than that in this house when it comes to getting projects like this "officially sanctioned." 8)

[---k---]

Henry,
You sub looks fantastic. Also, I love how you mounted you amp. I've been thinking about building some type of vertical rack for my amp ever since I saw you photo and someone mentioned how much better it would be for cooling (since I've cut my fans probably in half).

It is interesting to hear your wife's impression. My wife is probably similar. She could have really cared less, just wanted me to be happy and stay out of trouble. But, after I got done, she said that she would humor me and listen, but she didn't expect to hear much differance, because she usually can't. hehehehee I made her jump and duck in here seat during Incredibles! Also, listening to music, she just the same things as your wife. I think half the fun of this project is getting the response from those nay-sayers.

[HMenke]

Measured performance

Hi Ryan,

Hey thanks, I appreciate it. Whenever I do something like this, there's always that nagging fear that it will turn out bad and be an embarrassment. I am so pleased with the results I can't stand it! :B

The amp mounting has worked out great. It's so convenient to have the hookups close to the sub. Even still, I'm using 10-gauge for the short run to the sub and also internally (found a great price on the heavy gauge from cablewholesale.com). Thermally, I've got convection working a little against the fans because the intakes are on the front panel, so the air is exhausted out the bottom. I thought about reversing the flow but really it seems to be just fine as is. The amp isn't even getting warm much less hot.

A few months ago, I moved my "standard" sub location from the LF corner to the LR of the room. Now that the sonosub has shown that it also likes this corner, I will go ahead and permanently install my line level sub cable and my remote switched AC power receptacle here as well.

Here are some initial measured performance graphs. The first is without EQ and the second is with 10 bands of parametric EQ applied. The uncorrected graph is a bit wild; I have a tough room with two peak modes. At this point I don't know what is causing the dip between 16 and 32 Hz, but I was able to eliminate it with gain filters.

I can't say enough good things about using a laptop with Room EQ Wizard, a decent external sound card, the RS meter, and a midi connection to an equalizer like the DSP1124P. You just measure the sub in-room, set your filters in the software, upload to the equalizer, measure again, tweak filter settings, upload again, measure to be sure, and you're done.

Henry

[chasw98]

Gotta love that midi connection! Right, Henry? Graphs look good!

[HMenke]

Oh yeah, no more getting up and standing next to the BFD to tediously change filter settings on by one! I've still got some more tweaking to do on the curve but for a first pass not too bad.

Later on I'm going to run a sweep with the mains connected to see how they blend with the sub. With my old sub, I went back and tweaked the high end to smooth things out in the upper bass region. I expect the mains will fill in the crazy dips that show up in that area.

[collo]

Well done Henry!

It looks just like a bought one. Also congratulations on achieving such a high SAF - your ruse of keeping the level down for a while seems to have paid off! :T

[HMenke]

Thanks collo! I think you're right; if someone visits my house I think they would assume this is a commercial product because it really doesn't look "home made". It surprised me a bit that it turned out that way.

I was mostly going for function, but a couple of things I did from a 'styling' standpoint that contribute to a more 'high tech' look: a) the large-diameter port grille on top b) a 45-degree chamfer bit on only one side of the end caps, floor plate, and grille frame c) 1/8" roundover to remove the remaining sharp edge, but still retain the 'square' shoulder look.

Here are some images pulled from my CAD model that show some of these edge details.

[ThomasW]

Looking good Henry ....... :T

Now quickly start working on the second one before she knows what's happening..... :rofl: