Default My First DIY Project: Slopzilla subwoofer completed, a tome by Greg

[bcycle]

Hello!

I may have posted this message (below) in the wrong place. It probably belongs in this DIY section. Also, not sure why the thread title is "Default My First DIY Project: Slopzilla subwoofer completed, a tome by Greg", it should be "My First DIY Project: Slopzilla subwoofer completed, a tome by Greg"

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Greets!


I know you all have all been waiting with BAITED BREATH to hear about progress with my DIY Subwoofer (aka Slopzilla). For those who haven't been paying rapt attention to previous postings on this project my goal was to build a DIY sub to complement my music/home theater setup that would meet the following parameters:

Cost: around $200.00
Produce reasonably clean uncolored sound for both music and movies.
Not too big; 4 sq. ft was my max size.
Bass below 25hz.
Play fairly loud.

After some research I ended up with the woofer, amp and some miscellaneous parts from Parts Express and bought the lumber and hardware locally. I did run $107.00 over budget due to the fact that I decided to upgrade to slightly better parts. Here's my parts list and dollars spent

The Parts:
DAYTON RSS315HF-4 12" HIGH FIDELITY SUBWOOFER $104.00
DAYTON SA240 240W SUBWOOFER AMPLIFIER..Amp 110.00
1 sheet MDF 4'x8' x1" 35.00
Egg Crate foam 20.00
Gasket Tape, screws, grill cloth, etc. 22.00
Black Paint and Primer 16.00
______________________________________________________________________
Total $307.00


Some Background:
The reason I dubbed the project "Slopzilla" is because I am NOT a craftsman by any stretch. I expected dents and drips and mistakes that would yield an unsightly appearance and anticipated that despite my goal for clean bass, this thing could end up a boomy, sonically uncontrolled piece of furniture. My expectations were also low since I don't know acoustical theory all that well. I relied on a lot of reading and research to help me get by but I had low expectations. The "Zilla" part is due to the fact that even though my goal was something relatively small, it's still pretty damn big.

The Design:
Since my craftsmanship is suspect and my budget low, I decided to make a the box very heavy (1 inch mdf) to compensate for my inability to create complex bracing, mitered joints and other elements that help stiffen and neutralize the sound of the box. I ran some numbers using some BassBox Pro to resolve shape and size and came up with the following.

Qms = 3
Vas = 3 cu.ft
Fb = 19.82 Hz
QL = 6.506
F3 = 18.93 Hz
Dimensions: about 16"w x 25"H x 26"D

SCHEDULE

Day 1:
Cut Wood
Make Holes
Put box together with screws n' glue. Clamped and let dry overnight

Day 2:
Silicone caulked all interior joints
Primed and Painted
Added egg crate foam
Mounted amp, woofer and port

HOW"S IT SOUND?

Movies:
I made my neighbor Rich help me lug this thing up to my "Man Room" on the 3rd floor. It seems to weigh about 100lbs, but the Dayton Driver and 1 inch mdf can do that I guess. I set it up to the right of my stereo and connected it to the receiver's sub output. First listen was with the new James Bond Casino Royal and I gotta say, it sounded pretty damn good. My neighbor Todd, (the movie geek with the projection home theater) said that he was "amazed at the sound". That it "made the hair stand up on the back of his neck" He said he was "jealous" and his manhood "diminished". I think this was a compliment. My impressions with movies; The woofer seemed to woof at the right times (explosions, loud parts, etc.) but it wasn't boomy or there when t wasn't supposed to be. The more I listened the happier I was.

Music
The next big test would be with music but I was disappointed to learn that the Sub-output on the Yamaha does not send a signal to the speaker in non-surround recordings while in "Pure Direct" mode. Pure Direct is my Yamaha's method of sending the signal through the cleanest path without signal processing and it actually sounds quite good. Even pre- sub I would get rock stable imaging and fairly neutral mids and highs and the bottom end was clean and tight (down to about 40hz) I like the Pure Direct. So the next question was, will I be able to enjoy the sub with with music while in Pure Direct Mode? I posted to Audioholics and received some very useful and helpful input from j_garcia about hookup possibilities. In the end I ran the pre-outs and the sub outs of the receiver to a line level a/b box. This allowed me to use the sub-output while in a surround mode yet switch to the pre-outs for listening to music.But, since I was not running the music throgh the sub's xover I was concerned there would be a doubling of the bass in the 40hz range between my A/D/S M9/90's (where the upper end of the sub met the bottom end of my speakers). I listened to a bunch of cds and there did seem to be a "hump" in the bottom end with a lot of the music. I posted to Audioholics and again got some great help (thanks Mtrycrafts, MDS, AVRat, and j_garcia). I ended up moving the Sub and angling it. I pulled my main speakers about 6" inches closer towards my listening area (so they're about 3 feet from the back wall) and voila(!), everything fell in place. The bottom end became very smooth and seamless. Tight where the music warranted and very low if the data was there. I was really surprised to be able to hear much more room ambiance in a lot of my CD's (the new White Stripes for example) which I did not get during my pre-sub days. Also, the imaging and mids of my main speakers improved a touch, possibly the result of moving the main speakers further from the back wall. Finally, I don't think I've come anywhere close to testing the limits of the 240 watt amp and it get's very loud in my 25x25 sq ft space with cathedral ceilings.

EPILOGUE

So, here am patting myself on the back! I think as far as DIY projects go, building a sub was a no-brainer. Fairly simple construction and not too much rocket science can yield a pretty nice end product. I have learned that the cost/yield benefit to a high quality DIY sub is easier to pull off for a layman like me than if I were to attempt to build some decent speakers.

Thanks again to everyone for all your help!

Greg

Notes and Background: In my previous life, long ago I used to sell stereos. Not super hi end, but regular high end. (B&W's -801, etc., Quad, Revox, B&O, Rotel, Bryston, etc.) I don't know electronics or sound theory but as the result of listening to good stuff, I developed a pretty decent ear. I learned there's a lot of wiggle room even in mid-fi and if the setup doesn't sound right at the get go, one can always tune things up with by matching the components, better cables, speaker wire, placement etc. (You will not find me applying drops of fluid to my speaker connections or coloring the edges of my cds green ).

 

[Wafflesomd]

This thread is useless without pics.

 

[jinjuku]

Where did you get the egg crate foam from? I need to find a local source for that stuff.

Thx

P.S. Really nice looking sub. I bet that thing hits like a sledge hammer.

 

[bcycle]

Where did you get the egg crate foam from? I need to find a local source for that stuff.

Thx

P.S. Really nice looking sub. I bet that thing hits like a sledge hammer.

Thanks. Yup, it's still surprising me!

I think I bought it from these guys: http://www.uline.com/ProductDetail.asp?model=S-1819&ref=8002.

If you search "egg crate foam" you'll find a range of types and prices. Here's some other vendors:
http://www.foambymail.com/Eggcrate.html
http://www.foamdistributing.com/products/eggcratecon.html#softeggcrate
www.specialtymedicalsupply.com/medical-supply...
http://www.arrowpackaging.net/store/product_info.php?cPath=33&products_id=1048&osCsid=663438fb5d80b59949fce9d2c65e0366

Good Luck,,
Greg

 

[Guiria]

I think your sub looks sweet, nice work.

Do you have any in room response data?

 

[bcycle]

I think your sub looks sweet, nice work.

Do you have any in room response data?

Thanks G,

Honestly, I don't know how to measure my room response. I'm guessing a DB meter and a tape measure are involved?

Greg

 

[avaserfi]

Thanks G,

Honestly, I don't know how to measure my room response. I'm guessing a DB meter and a tape measure are involved?

Greg

There are a couple ways to measure room response, one easier than the other. The first is take a disc with test tones on it (Rives sells one calibrated for a Radioshack SPL meter) and play a tone and then record the SPL and the frequency you are playing at then make a graph.

The other and far easier, if you have the equipment, is use a program to do so. Room EQ Wizard is a free program that will do just that for you.

Plotting frequency response will be very useful so you can better place your sub as location is huge with the lower, longer, frequencies. As little as a couple inches could flatten or destroy your response.

 

[annunaki]

There are a couple ways to measure room response, one easier than the other. The first is take a disc with test tones on it (Rives sells one calibrated for a Radioshack SPL meter) and play a tone and then record the SPL and the frequency you are playing at then make a graph.

The other and far easier, if you have the equipment, is use a program to do so. Room EQ Wizard is a free program that will do just that for you.

Plotting frequency response will be very useful so you can better place your sub as location is huge with the lower, longer, frequencies. As little as a couple inches could flatten or destroy your response.

How does one download and use that program? Wouldn't you need a microphone?

 

[avaserfi]

How does one download and use that program? Wouldn't you need a microphone?

Close to the bottom of the link I posted previously there is a download section. You will need to register with hometheatershack's (its free) forums to access this download.

You will need a microphone, the more linear the better, but people have created calibration files for Radioshack SPL meters that work pretty well. So if you have one you are pretty much set. Once you have downloaded the program the help has a great guide to getting started with links to every interconnect/adapter you would need to take measurements and exactly how to set everything up.I don't think the writers could have done a better job with the program, for the price especially, to be honest.

 

[WmAx]

Where did you get the egg crate foam from? I need to find a local source for that stuff.

Thx

P.S. Really nice looking sub. I bet that thing hits like a sledge hammer.

I highly recommend against using such foams. They have a very low co-efficient relative to frequency vs. thickness. For example, a 2" piece of this 'packing' foam (and this includes foambymail -- they claim acoustic foam but 3rd party measurements suggest fraudulent claims ) may absorb nearly 100% of the energy at 1000Hz, but at 500Hz, perhaps only 30%. Where as a high grade acoustic foam such as Auralex at the same thickness would absorb nearly 100% at 500Hz, and still some appreciable amount at 400Hz. The most effective materials are generally high density fiberglass and high density mineral board. For example, a 2" thick piece of non-faced 8# mineral board or non-faced 6# fiberglass would have nearly 100% energy absorption at 250Hz.

Note: Absorption numbers referred to here are assuming A-Mount specification, which means mounted flat against a solid surface(the cabinet wall in this case). Co-efficients change according to the mount type. Absorption used in the capacity of this post refers to the attenuation of reverberation and reflectivity of a pressure wave off of the boundary surface, not transmissive properties through the material.

-Chris

 

[bcycle]

I highly recommend against using such foams. They have a very low co-efficient relative to frequency vs. thickness. For example, a 2" piece of this 'packing' foam (and this includes foambymail -- they claim acoustic foam but 3rd party measurements suggest fraudulent claims ) may absorb nearly 100% of the energy at 1000Hz, but at 500Hz, perhaps only 30%. Where as a high grade acoustic foam such as Auralex at the same thickness would absorb nearly 100% at 500Hz, and still some appreciable amount at 400Hz. The most effective materials are generally high density fiberglass and high density mineral board. For example, a 2" thick piece of non-faced 8# mineral board or non-faced 6# fiberglass would have nearly 100% energy absorption at 250Hz.

Note: Absorption numbers referred to here are assuming A-Mount specification, which means mounted flat against a solid surface(the cabinet wall in this case). Co-efficients change according to the mount type. Absorption used in the capacity of this post refers to the attenuation of reverberation and reflectivity of a pressure wave off of the boundary surface, not transmissive properties through the material.

-Chris

I'm counting on the 1" MDF to minimize the sound and vibration of the box. I thought the egg crate foam might reduce standing waves since I was dealing with a box with parallel surfaces but my brain is very small and it makes me do silly things. Nonetheless the thing sounds pretty awesome!

G

 

[jinjuku]

Note: Absorption numbers referred to here are assuming A-Mount specification, which means mounted flat against a solid surface(the cabinet wall in this case). Co-efficients change according to the mount type. Absorption used in the capacity of this post refers to the attenuation of reverberation and reflectivity of a pressure wave off of the boundary surface, not transmissive properties through the material.

-Chris

I have a sub project in the works. Do I line all surfaces besides the baffle board with the R13 insulation that I purchased, or just the opposing box wall? Or is this something of trial and error?

Thx.

 

[WmAx]

I'm counting on the 1" MDF to minimize the sound and vibration of the box. I thought the egg crate foam might reduce standing waves since I was dealing with a box with parallel surfaces but my brain is very small and it makes me do silly things. Nonetheless the thing sounds pretty awesome!

G

The packing foram can not have an appreciable effect. You need to use a material such as I suggested in the previous post. But realize, in a cabinet with small dimensions relative to wavelength(most subwoofers), excitation of the standing waves related to the cabinet dimensions are not usually an issue if a proper crossover frequency and slope rate are utilized. However, other sounds from the subwoofer could potentially benefit from damping(internal suspension and air turbulence noises).

-Chris

 

[WmAx]

I have a sub project in the works. Do I line all surfaces besides the baffle board with the R13 insulation that I purchased, or just the opposing box wall? Or is this something of trial and error?

Thx.

I am not sure which insulation you are using -- but if you are using standard low density home insulation -- it's not very effective vs. thickness. Refer to materials such as 5lb/ft^3 to 8lb/ft^3 density fiberglass board and mineral wool board. Use in thickness of 4" to absorb virtually all internal reflections/reverb at >125Hz, which will still have some appreciable absorption properties slightly <100Hz. This would be a suitable thickness in large subwoofer cabinets. For small cabinets(<2 ft^3), 2" is more practical. You need not put it on every wall(unless you are going for overkill). Just one wall per parallel set is sufficient, since for subwoofer applications we are only trying to prevent excess oscillation. In a mid-range/mid-bass system, you would cover every possible surface. However, the actual use of this material in subwoofer cabinets of average to small size in many cases is minimal, if at all. Please refer to my post #13 in this thread.

-Chris