My Dual 15" DIY Sub Project - completed

**---k---** · 13 January 2006, 11:10 Friday

Holy S***, it looks like you stole some of my photos!

Those look great, and almost exactly what I going for. So how do they sound? I would love to see some FR graphs and stuff to compare to mine.

Also, how much stuffing did you use, and what did you use? I need to add a lot more to mine. I just got some R30 lining the box.

**ThomasW** · 13 January 2006, 13:11 Friday

Nice job..... :T

Only suggestion would be using an LT circuit if/when the budget allows. That would fill-in the bottom end and not alter the sound quality.

I'm curious as to a comparison between your DIY subs and the ACI Titan? Obviously there will be ouput level differences. My question primarily relates to sound quality, since I've never heard an ACI sub, but I'm a fan of Mike D's stuff.

**cbj** · 13 January 2006, 16:53 Friday

Thanks for the comments.

---k---
Sorry, about that. I took these pictures myself, I swear! I started up my project about the same time you started up your thread. I didn't have to worry about the shielding though and I think you were able to get away with a little larger enclosure than me. In addition I think you did a better job of bracing than I did. In terms of stuffing I used fiberglass insulation with the paper backing removed. I just went to Lowes and picked up a roll that was the cheapest and that I thought weighed 9-10lbs. I think it was R19 and cost $10. I stuffed each enclosure with about 3lbs.

Here is a FR graph from my listening position which is about 12ft from the subs. It was done with Room EQ. I have a really nasty dip around 60HZ (obviously) and the low end starts to take a dive after 30Hz. Ignore the numbers at the top right of the chart, I forgot to remove them when I saved the graph.

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Here is the response with 4 filters from the BFD. I have cuts at 50Hz and 66Hz and boosts at 59Hz and 20Hz. I will probably play with it a little more, but I am pleased with the response with 4 filters.

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Thomas,

I am definitely considering a LT down the road. That is one reason I went ahead and got the higher wattage Nady. As for the comparison with the Titan it is a little hard because I am going by memory. I sold the Titan so I could build these. My goal was to have comparable sound quality to the Titan with higher output levels. These are still breaking-in and I am not done with the BFD yet, but overall I am very pleased. The DIY do have a higher output level and I think the sound quality is very good. The Titan probably had a shallower roll-off on both the top and bottom end down to about 20Hz. Unfortunately I didn't have RoomEQ back then so I am going by old RS meter measurements. Probably the biggest proof of how good the DIY subs was when my wife said "You know I was skeptical about this whole project, but these new subs are definitely an improvement."

**---k---** · 13 January 2006, 17:11 Friday

Very cool. What did you use for paint?

**ThomasW** · 13 January 2006, 17:19 Friday

Both you guys might want to set up a medium bandwidth filter at 20Hz and dial-in some boost..... :T

**cbj** · 14 January 2006, 09:07 Saturday

The first picture is with cheap black spray paint as a primer coat. I used truck-bed liner paint from Wal-mart, I think the brand name was "Plasti-Kote". I did 3 coats of the bed liner with a roller. If you use truck bed liner, be sure you shake the can several times each time you put on a new coat, otherwise the texture material in the paint will clump together. I would also suggest you wear gloves while applying the bed liner paint, or else it'll stain your hands for many days to come.

I do have a filter set up at 20Hz, but I need to widen the bandwidth and increase the gain. Maybe I'll get around to that this weekend.

**Brian Bunge** · 14 January 2006, 09:31 Saturday

Thomas,

I helped a friend of my built a Titan II sub back when ACI sold them as kits. IIRC, they have a Q around .6 and sounded very good to me the few times I've had the opportunity to listen to his system. The sub has nice slam without sounding bloated.

I too am a fan of Mike's products and of Mike himself. He's one of a handful of the true gentlemen I've had the pleasure of meeting in the audio world.

**kgveteran** · 14 January 2006, 11:14 Saturday

I think the hand cart in the background tells the whole story on weight and build quality.

Great job.Ditto the L/T circuit.

KG

**steve nn** · 14 January 2006, 11:40 Saturday

I appreicate any comments, questions, or suggestions. Since finishing this I am looking forward to more DIY projects down the road.

Nice! Your pics and graphs do a very good job of conveying what you just built.

I too am a fan of Mike's products and of Mike himself. He's one of a handful of the true gentlemen I've had the pleasure of meeting in the audio world.

Me to Brian... I was as impressed with Mike as much as I was the Maestro. Quality of character coupled with nice SQ/SPL. He has a very good handle on what makes a good sub imo and is always a pleasure to work with.

**---k---** · 14 January 2006, 15:23 Saturday

Truck bed liner? Very cool. It got suggested to me too. (Did you choose it before or after you saw it recommended to me?

). Is there anyway to get a few more photos that show off the finish?

Also, how much volume are you using for your driver? I calculate that you have a ~90L box.

Also, can you discuss how you think it sounds any more. Is that FR graph you showed for one or both? And Mine will both be hooked up soon. We'll have to compare some notes.

Very cool!

**cbj** · 15 January 2006, 09:31 Sunday

I really like Mike's stuff as well. The rest of my setup consists of 25AE Sapphires, a Protege center, and Emeralds for surrounds. I have been reading up on the LT circuit, but it will probably be awhile before I get around to building one. Now that I have finished the subs the next couple projects will be home improvement stuff.

I chose the truck bed liner based upon some pictures here and over at Home Theater Forum. Here are a few more pictures.

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The internal volume of each boxes is 3.08 cu ft or 87.3l, once I take into account the volume taken up by the driver and braces I get somethere from 78 to 80l net. Looking back I could have made the boxes a couple inches taller and ended up with around 90l, but I am happy with the way they turned out.

The FR is for both subs from my seating position. I haven't done any nearfield measurements yet, which I would need to do to make a LT.

**cbj** · 07 February 2006, 11:39 Tuesday

I played around and took some more measurements yesterday to try and get an idea of what my room is doing to the frequency response and to work with the EQ a little more.

First both subs from about 1 ft away. I'm not sure why I have the dip around 34Hz.

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From the primary seating position 12ft away. A nasty dip around 57Hz, a couple small peaks at 50Hz and 66Hz, and a dive below 30Hz.

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And finally with EQ. I used 4 filters- 2 cuts and 2 boosts.

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My FR isn't perfect by any means but I'm pretty happy with it. My next step is going to be some acoustic treatments to see if can fix some of the dips and peaks and reduce the amount of EQ I am using.

**ThomasW** · 07 February 2006, 11:53 Tuesday

Do a nearfield 2" from one of the dust caps. That basically eliminates the effects of the room.

There's nothing wrong using more filters particularly 'cut'. I'd try to flatten the plateau between ~30Hz and beginning of the null at 57Hz. Pull that down so it's at the same level as the little bump at 20Hz. Then do the same for the plateau between 58Hz and 90Hz.

**---k---** · 07 February 2006, 13:10 Tuesday

I'm kind-of surprised by your 20hz - 30hz response. Looking at mine and Steve's (our three subs are nearly identical) graphs, it looks like we are getting room gain at is filling this region in nicely. I'm sure it has a lot to do with room and placement. Are you just co-locating them in the corner like the photo up top shows?

My measurements for comparison. My subs are located under my mains.

**cbj** · 07 February 2006, 15:39 Tuesday

Thomas thanks for the advice. I don't have a real stand for the RS meter, so I will just have to hold the meter with one hand and click the mouse with the other hand to get the nearfield measurements. The only reason that I didn't use more filters was because I thought I read somewhere that more filters increased the Q of the sub. Of course I don't know how much of an increase or if I would even be able to tell the difference. I will try and see if I can get a smoother response with a few more cuts.

--k-- I'm a little surprised by my 20-30Hz region too. I need to get some nearfield measurements done, but I'm pretty sure it is the room and the current location. Currently the subs are stacked and co-located in the corner behind the A/V Rack and TV, like the last couple photos. I guess the other thing I could do after nearfield measurements is measure each sub individually and figure out if I get a better response from either since they face different directions. Hopefully I will get a better feel for what is going on then.

**ThomasW** · 07 February 2006, 18:34 Tuesday

Steep narrow 'boost' filters change the "Q", wider 'cut' filters aren't a problem

**steve nn** · 07 February 2006, 19:17 Tuesday

The volume is about 80l net and they weigh a little over 125 lbs each. Here are a few pictures.

I'm a little surprised by my 20-30Hz region too. I need to get some nearfield measurements done, but I'm pretty sure it is the room and the current location.

No matter what sub I use I can always expect a big bump at around 30 and a slight dip at 20. My room is 12 X 24 X 10' so there's no way around it...well except for dialing it out of course. All my subs have been constant in exhibiting this. I also found my drop after 18hz is in-fact a null by NF measurements that I think will be able to be overcome by a few different options that have already been mentioned.

Since this was done with my old ART351, things look (and sound) much better now after receiving the FBQ2496. After you get things figured out, you might elect to cut from 30hz on up a bit more and you should come in fairly flat? I'm flat down to 18, but thats as good as I can do for now. You can also play around with the fill to a degree.

Do a nearfield 2" from one of the dust caps.

That will give you a real good idea on what's going on.

**---k---** · 07 February 2006, 23:34 Tuesday

I bought a $9.99 samsonite camera stand from micro center a few months back. holds my spl perfectly. You can usually find them for ~$15.

Just for fun, have you try opposite corners and see what you get.

**Dennis H** · 08 February 2006, 14:22 Wednesday

I'm a little surprised by my 20-30Hz region too

Are you using the RS meter correction curve?

**cbj** · 08 February 2006, 15:39 Wednesday

Thanks for all the suggestions guys. It probably be a couple days until I get around to it, but here is the plan.

1) Do nearfield measurements of each sub separately to make sure I don't have anything strange going on with either one.
2) Do measurements from my seating position of each sub separately to see if I get a better FR based on the direction the subs are pointed.
3) Use some more cuts to try and get a better FR.
Hopefully I will get some better results because possible locations for the subs are extremely limited.

The only thing that could be throwing the low end off is the fact that I am not using the C weighting compensation in RoomEQ. I am using the digital version of the RS meter and the reports I have seen say that you need to use the C weighting for the analog but not the digital version of the meter. Can anybody confirm that or is there an easy way that I could check it myself?

**SteveCallas** · 08 February 2006, 15:54 Wednesday

I'm pretty certain the digital meter needs the correction as well - that would probably expain your FR.

**cbj** · 08 February 2006, 16:48 Wednesday

My understanding is that you need to use the corrections if you are using the readout on the Digital meter, but not when you use the RCA output. I that reasoning from the first post here.

**Dennis H** · 08 February 2006, 17:43 Wednesday

The trouble is RS has made a number of different meters with the same model numbers so it's hard to know what's going on with any particular meter unless you get it calibrated. Anyone who is serious about audio should invest in a mic e.g. the Behringer/Nady. You don't have to spend a lot to get good quality. Consider it a tool purchase like a router or a soldering iron.

**SteveCallas** · 08 February 2006, 17:56 Wednesday

cbj, it should be easy enough to test. Run a 20hz sine wave from RoomEQ - see what level your meter displays and see what level the program displays. If they are the same, you need to apply the correction.

**cbj** · 10 February 2006, 11:44 Friday

OK, here we go again. I was able to get in some more measurements yesterday. First off here are the nearfiled measurements for the L and R subs

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From these two measurements I figured out a couple things. First my RS digital meter output is not C-weighted so you do not need to use the correction values when using it. The same is not true for the display. I played a 20Hz tone and the meter measured around 82db on the output while the display showed about 76db. Also now I can see that my subs have output down below 30HZ and the rolloff must be due to the room. Finally, it looks to me like the FR from each sub is pretty close to it's twin. The R has a little shallower rolloff which might be from stuffing differences I guess.

Next I measured each sub separately from my listening position. Again L and then R.

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From the individual graphs I didn't see how the positioning of the L or R sub had a signifigant advantage. The L sub falls off a little more gradually from 65Hz to 100Hz but the R sub is a little flatter from 30Hz to 50Hz. I decided to keep both subs where the are for now.

Next another measurement of both subs from the listening position. No real change here from my earlier measurements.

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I decided to only add boost down low (20Hz) and not try to boost the 57Hz null at all. I did however use 7 cuts between 30Hz and 80Hz to try and get smoother response. Here is the RoomEQ predicted repsonse. If it works I should get 20-100Hz of around +/-3db (with the exception of the null)

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Finally here is the result which is pretty close to RoomEQ's prediction.

I think my next objective is to get some acoustic treatments to try and counter that null around 57Hz. Anyone have any other suggestions or observations?

**ThomasW** · 10 February 2006, 11:53 Friday

Anyone have any other suggestions or observations?

Go in with some wide filters, and bring down all the levels on either side of the null.

Using wide filters (sometimes filtering frequencies outside the passband) helps flatten large areas.

**---k---** · 10 February 2006, 11:57 Friday

Thomas once suggested to me to try rotating my subs so they fired the other direction. I haven't tired it, but it sounded like a good suggestion. I've seen results really change just by moving the mic a few inches, so it wouldn't suprise me if I moved the face of the drive that I would get a differnt response.

I would also take a few measurements like a foot forward and back, see how much it changes.

**SteveCallas** · 10 February 2006, 12:42 Friday

cbj, so the line level output of the digital meter does not need correction applied to it - good to know, thanks for doing that experiment. Everybody talks about how innacurate the RS meters are, but those first near field responses look like your meter is performing just fine to me.

**---k---** · 10 February 2006, 12:46 Friday

Steve,
I've come to the conclusion that most people who post on these forums - myself included - only know what they are talking about 50% of the time.

**cbj** · 10 February 2006, 14:32 Friday

Thomas- I'll give the wider filters a try and see what I can come up with, thanks.

-K- Although you might not be able to tell it very well from the photos my left and right subs (actually top and bottom) already face different directions. That's the reason I decided to measure each sub separately and see if there was a particular direction that worked better. Overall I thought the results were pretty similar since both have the 30Hz roll-off and the 57 Hz null.

Steve- I don't know if all the RS digital meters are the same, but at least my meter doesn't need the correction values for the output.

**TEK** · 10 February 2006, 15:05 Friday

Isn't it a good idea to mesure the respons several places in the room?
Mainly around your listening position, but as ---k--- (

) said, it may vary a lot if you just move the mic a few centimeters.

So if you only mesure at one exact location, you may actually be fixing up a very local problem and add huge problem all other places in your room.

First you should try to get a respons that is as flat as possible around the seating position by reallocating your sub's and speakers as well as adjust the phase.
When that is done, you may start adjusting the EQ

TEK

**dyazdani** · 10 February 2006, 16:08 Friday

Originally posted by kgveteran

I think the hand cart in the background tells the whole story on weight and build quality.

Great job.Ditto the L/T circuit.

KG

Yep. I'm building a RL-p15 sub as well - I've estimated the final enclosure weight based on the density of MDF I have around the house. I've calculated 150lbs - all sides will be 2 x 0.75" except the baffle which will be triple layer. The inner layer will be ply though for better T-nut grip.

Add the driver and you're looking at 190lbs each. 8O

**---k---** · 10 February 2006, 16:19 Friday

Danish,
Wow! How big are the boxes you are building. Mine, which are similar in size to CBJ's are only about 75lbs w/o the driver and ~110 w/ driver. I can move the empty boxes around by myself.

**dyazdani** · 11 February 2006, 00:00 Saturday

It's going to be 20X23X22 at the moment (external), I'm still finalizing the design.

The piece of MDF I have weighs 28lbs and a 24x48x.75 sheet is 0.5 cubic feet. If you work out the gross - net volume - driver hole + bracing (estimate), I got just shy of 150lbs. There may be some variability in the density though based on where I get the MDF.

**steve nn** · 11 February 2006, 02:47 Saturday

I got just shy of 150lbs.

That seems pretty close. My 1.25" 22" cube must be darn close to 130-140 lbs I would think.

**---k---** · 11 February 2006, 15:23 Saturday

I'm going to have to buy a bathroom scale and weigh mine. Maybe they are heavier, and I am stonger, than I previously thought.

**steve nn** · 11 February 2006, 18:07 Saturday

and I am stonger, than I previously thought.

The word on the street is your a pretty rough dude Ryan. :lol:

:k>

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My Dual 15" DIY Sub Project - completed

My Dual 15" DIY Sub Project - completed

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