My First Sub

[ThomasW]

It's not like doing metal or exterior wood where one needs a true primer. So anything that's relatively thin and easily absorbed is a ok primer.

The current trend, and something I think is a good idea, is using truck bed liner as the finish coat. It's significantly more durable than any paint. As a result it tends to protect the MDF better. It's impossible to get smooth. The best approach is to use a roller and live with the texture they create. The fact that it's a thick coating and has a texture tends to hide a myrid of sins....

Steve nn,

Downfiring is much better than firing into a sofa.

[steve nn]

Steve, Sounds like you are ready for a design thread! How about starting one with photos of your room, and where you think you will put these bad boys. (I don't mind the question here, but I think you would get better answers that way)

Hey -K- that's a good idea and please forgive if I imposed. Your not the first to mention this. Your sub seems to be coming along very nicely and Thank you for doing this Thread..it has been very informative.

Downfiring is much better than firing into a sofa.

I would agree in most cases. I can tell you that there has been many of us SVS users that have taken their baseplate off and fired the driver out into the room or towards the wall itself for a smoother FR response with out introducing EQ. When I played with the Titanic MKIII and the ACI Maestro, I really noticed it. I'm not sure what to attribute that to with them being both sealed designs? From the graphs it would appear that it was the 2dB gain around the 18-22Hz area wile not hurting SQ.

[collo]

Silicone sealant

Since you are currently building your second sub, it's probably not too late to grab a tube of Neutral Cure Silicone.

Normal silicone emits acetic acid as it cures, (which is why it smells like vinegar), so you should wait until there are no more fumes before mounting the amp and drivers 8O

I'm not sure what the neutral cure stuff outgasses, but it smells different and is what is recommended for sealing metal roofs - ie no acid released as it cures :T

regards
Collo

[---k---]

and Thank you for doing this Thread..it has been very informative.

Steve,
Don't thank me. Thank Thomas, Chris, Dennis and everyone else here. Without them, this thread would just be me asking stuid questions. They are the ones that make this valueable. :T to all of them!



Thomas,
Truckbed liner??? Wow, I haven't seen that.
When can I get that, and how much does it run?

[ThomasW]

Truckbed liner??? Wow, I haven't seen that.
When can I get that, and how much does it run?

Most larger auto supply stores sell it. I haven't bought any in years so don't know current pricing. Know that it's not cheap.

[Dennis H]

Al at RAW uses truck bed liner a lot. He rolls on a coat of flat black latex house paint and then sprays the liner paint from a rattle can (at least that's how he used to do it.) I think he uses Duplicolor brand and holds the can back far enough that the paint sort of mists on. Practice is your friend.

[---k---]

Well, I got carried away with the bondo tonight and probably created a lot of unnecessary work for myself, but.... I ended up putting a skim coat of bond on all the exposed MDF edges as well as filling all the holes. I'll have a lot of sanding to do tomorrow, but... getting there.

The second one will get the front baffle glued on in about an hour after the little plywood blocks glue and I an pound in the t-nuts.


Thomas,
You said a thin primer. Does a thin primer have advantages? I was thinking maybe something thicker like a basement wall sealer, just to give it more durability. Especially if I don't end up doing a truck bed liner because of cost. I'm thinking the final coat may be just a Krylon spray with some blue fleck, over a couple of coats of flat black.

Dennis,
RAW = ???

[cjd]

The primer is primarly intended to seal and prep the MDF. In general, the first coat or two should always be thin in order to do this well.

Make sure you keep track of the finish bases so you don't mix shellac with lacquer or something and get unexpected results.

Now you know why my speakers are all plain birch ply.

C

[---k---]

Chris,
I'm no where near ready to build with brich ply and not finish it with something that can cover up my booh boohs.


I did a lot sanding tonight of the Bondo I put on yesterday. I used way too much bondo yesterday. But, I covered up all of my uglies, so it is looking good. I got one coat of grey primer on 5 sides. I'll have to do some more sanding to smooth the transition from wood to bondo, but that is expected.

[noah katz]

"I'll have a lot of sanding to do tomorrow"

You can save a lot of elbow grease next time if you hit it with a coarse file while it's still a bit soft - between 5 and 20 min depending on temp, in my experience.

[---k---]

One Done!

Well, the first one got a coat of tinted primer last night, so it is complete for a while. I'll finish up the finish in a few weeks, after I settle on my new front mains. Here is what it looks like with a grey primer:





I actually have a few more things I need to do to really finish this thing up. I need to stuff it more. Right now it is pretty lightly stuffed. I don't have a scale to weight the R30, but there is probably only 3' feet of it in there. One layer against the back wall, and then another foot split around the driver. I also need to put the spike feet on. I'll eventually hook up the RS meter to the computer and take a few ETF measurements up close to see how I'm doing. But for now, I'm going to sit back and listen and demo a bunch of main speakers. (Don't worry guys, I think I'm going to be doing a pair of DIY bookselves this summer. )

Hopefully tomorrow night I will bondo up the second one, and it will get a oat of primer on Thursday and be ready to hit hard this weekend. :B

Thanks all for your help.,

[---k---]

Oh, and I put the second driver in this one, and just listening to some tunes and it is sounding good out of the box so far. It hits a lot tighter and harder than my old bloat box without being loud and overpowering. Liking it.

[steve nn]

Nice going Ryan. Congrats! :T

[ssabripo]

good job Ryan....post some more pics!!!! 👍

[---k---]

It is impossible to bottom my sub, correct?

Last night, I was showing off for a friend. I had the amp only about 3/4 of the way up (NOT bridged), and I had turned the sub channel to +8 on the receiver. During a couple of explosions, it sounded like it was breaking up. There was a small crackle. It wasn't a big bang or anything like that. My friend didn't even notice. But I did. Any thoughts on what this could have been?

I need to replace the weather stripping around the driver. When I was painting, I got some paint on it, and it is missing in a few spots. I figured it would be okay until I replaced it when I do the next one. So maybe I'm gettting leaks big enough to cause problems?

Or could this have been the amp clipping?

[BeemerZ1]

Sounds to me like the amp is clipping...
On the other hand, all speakers will meet a limit at a certain point.
But I don't think you have enough power to do that, at least without clipping.

[steve nn]

During a couple of explosions, it sounded like it was breaking up. There was a small crackle.

Do you have the capability to calibrate Ryan? +8 on your receiver is very high if you have a range from -10 to +10. Some receivers are a little to very hard to run with a pro amp, but I would think most offerings today wouldn't present to much of a problem. It's been awhile since I've ran one, so admittedly I'm out of the loop. It does seem as though some of the yami models didn't put out enough voltage with out the use of a attenuator.

Anyway.. what you might be experiencing is distortion. I used to clip my QSC every now and then, (mostly soft) but I don't recall hearing anything except the click of it shutting down? Your amp could function differently of course.

[ThomasW]

I need to replace the weather stripping around the driver. When I was painting, I got some paint on it, and it is missing in a few spots. I figured it would be okay until I replaced it when I do the next one. So maybe I'm getting leaks big enough to cause problems?

This maybe the problem. It's important to have an airtight seal. Small leaks can have a buzzing sound that's often mistaken for clipping/distortion.

If you can, after you replace the damaged weather stripping do a smoke-test. This entails having a cigarette or stick of incense and going around the perimeter of the driver while it's playing. Any air leak will show up as a deflection of the stream of smoke. Be sure to check near the driver mounting screws

[---k---]

Well like I said, I was showing off. Setting the receiver to 0 and the amp at about 2/3 get the sub pretty well balanced with the mains. I only set the receiver up to +8 because I was too lazy to get my butt out of the chair to turn the amp further up. ops:

If it is the amp clipping or distortion, that is kind of dissapointing, because I wouldn't think I was drving it that hard if it was only 3/4 the way up. And, like people said, the +8 on the receiver is a pre-out, so there really shouldn't have been a problem here.

I'll grab a smoke stick from our lab tonight on my way out of the office redo the weather stripping, and check for leaks. Hopefully that is the problem, because that is the easiest to fix.

Are there any tips for bending the weatherstripping around the circumferance? As I bent it, it would bunch up and not want to bend, so I just would cut a little out at each screw hole. Is there a better way?

Thanks,

[steve nn]

If it is the amp clipping or distortion, that is kind of dissapointing, because I wouldn't think I was drving it that hard if it was only 3/4 the way up. And, like people said, the +8 on the receiver is a pre-out, so there really shouldn't have been a problem here.

I think your amp is most likely fine. Might I suggest that the signal you send it needs to be kept at below the -0 mark if possible. I know there are two different schools of thought in regards, but I have always found keeping the signal below the 0 setting always equates out to cleaner bass. I wouldn't be afraid at all to run your pro at full if you can get away with it.. without being over calibrated. You most likely have another problem though like just suggested.

[SteveCallas]

Doesn't the Nady have red clipping lights? If the amp was clipping you should have noticed a flash or two of it.

Otherwise, as for output down low, if I'm not mistaken you are at something like -3db at 45hz and -15db at 20hz before factoring in room gain.

[---k---]

Yeah, the Nady has clipping lights, and I didn't notie anything. But, it is hard to look at the amp when you hear something funny comming from the sub. My eyes went straight to the sub.

I got some more weather stripping on my way home. I'll pull the driver and re-do it all tonight after I finish up the remaining bondo and sanding I got to do on #2. I brought home a smoke testing kit from work, so I'll check for leaks and report back.

[---k---]

Well,
I got out ETF tonight. Good news, with the sub pulled out into the middle of the room and the RS meter placed about 2" from the driver, it looks like the models [Edit2, it is falling off faster. At 35, I think it should be -5 where ETF showed -10db]. The bad news is with it where I was going to place it, YUCK! Big null, and not a lot of room gain down low. Here's hoping that the second one will clean this mess up, and what's left can be delt with using a BFD.

[Edit:
I moved the sub over to the left side and added the FR. Double Yuck!

I think I'm going to have to get out a test CD and do these by hand to check ETF. My old sub was never this bad when tested. :M]

[Edit2:
I know that I need to add a lot more stuffing to the box. and take more measurements. I was too depreased last night after seeing these things. When I listened to the sub, I thought that there was major lack of extension, and it seemed to be missing quite a bit, hence turning it waaaay up. I guess I got a lot of work to do this weekend to tune these things.
Any suggestions would be appreciated.]

[steve nn]

I'm sorry for asking, but prudence requires. Has correction been added Ryan?

[ThomasW]

I know that I need to add a lot more stuffing to the box. and take more measurements. I was too depreased last night after seeing these things. When I listened to the sub, I thought that there was major lack of extension, and it seemed to be missing quite a bit, hence turning it waaaay up. I guess I got a lot of work to do this weekend to tune these things.

Those plots aren't a result of the boxes needing more damping. If accurate, they're purely a function of room placement and the position where you're making the measurements.

Obviously you need to boost the lowest octaves with the BFD.

[---k---]

Steve,
No. No correction has been done with these plots, YET.

Thomas,
Yes, I understand that most of what I see is due to room placement. I only mentioned the stuffing, because I have very little in right now.

Do you have any explanation for why the sub is dropping off so fast? With the mic only about 2" from the driver, I thought that this measurement should be pretty accurate. Is there anything in the build that could cause a driver to drop off faster like this?

[Dennis H]

By "correction," I think he means the mic calibration file to correct for the RS meter's C-weighting. I think the ETF docs say none is needed but that is incorrect. The RCA output gets the same weighting curve as the meter.

[---k---]

Oh, thanks Dennis. I thought that he ment, had I attempted any correction with the BFD.

I use the RS meter as a mic, and then use the RS calibration file from ETF. It then corrects everything automatically.

[ThomasW]

Do you have any explanation for why the sub is dropping off so fast?

1) rather smallish sealed box
2) driver has a relatively high Fs
3) no room gain in nearfield measurements
4) need to add in the RS corrections

[Dennis H]

RS calibration file from ETF

If it's like the one I saw, it doesn't do any correction below 500 Hz. They claim the RS meter is flat down there. That claim is incorrect. Open the file with Notepad and check it out.

[steve nn]

These will differ a little from what your used to, but I think many would consider them more accurate.

10.293 -5.012
> > 10.595 -5.012
> > 10.905 -5.664
> > 11.225 -7.011
> > 11.554 -6.133
> > 11.892 -6.205
> > 12.241 -7.369
> > 12.599 -4.993
> > 12.968 -5.688
> > 13.348 -7.113
> > 13.74 -9.407
> > 14.142 -9.619
> > 14.557 -11.361
> > 14.983 -13.717
> > 15.422 -14.82
> > 15.874 -14.974
> > 16.339 -14.771
> > 16.818 -14.672
> > 17.311 -14.387
> > 17.818 -14.008
> > 18.34 -13.298
> > 18.877 -12.899
> > 19.431 -12.177
> > 20 -11.472
> > 20.586 -11.034
> > 21.189 -10.838
> > 21.81 -10.274
> > 22.449 -9.71
> > 23.107 -9.138
> > 23.784 -8.698
> > 24.481 -8.213
> > 25.198 -7.813
> > 25.937 -7.482
> > 26.697 -7.037
> > 27.479 -6.617
> > 28.284 -6.227
> > 29.113 -5.883
> > 29.966 -5.427
> > 30.844 -5.142
> > 31.748 -4.913
> > 32.678 -4.874
> > 33.636 -4.55
> > 34.621 -4.248
> > 35.636 -4.023
> > 36.68 -3.799
> > 37.755 -3.571
> > 38.861 -3.412
> > 40 -3.179
> > 41.172 -3.018
> > 42.379 -2.964
> > 43.62 -2.911
> > 44.898 -2.754
> > 46.214 -2.56
> > 47.568 -2.47
> > 48.962 -2.663
> > 50.397 -1.999
> > 51.874 -2.238
> > 53.394 -2.259
> > 54.958 -2.311
> > 56.569 -2.137
> > 58.226 -2.388
> > 59.932 -2.515
> > 61.688 -2.545
> > 63.496 -2.302
> > 65.357 -2.107
> > 67.272 -2.09
> > 69.243 -2.076
> > 71.272 -1.733
> > 73.36 -1.177
> > 75.51 -1.195
> > 77.723 -0.966
> > 80 -0.876
> > 82.344 -0.731
> > 84.757 -0.728
> > 87.241 -1.198
> > 89.797 -1.627
> > 92.428 -1.848
> > 95.137 -1.509
> > 97.924 -1.454
> > 100.794 -1.249

[ThomasW]

Ryan,

For grins try some measurements with Room EQ Wizard and see what it shows

[---k---]

Well, I opened up the ETF cal file in notepad, and if I'm reading it correctly, yeah it isn't correcting anything below 500. Odd! I've always seen the corrections more inline with what Steve posted. I'll have to email Doug Plumb about this.

I tried RoomEQ Wiz when it first came out, and it didn't like my laptop for some reason. I didn't have the problem with ETF. I've been meaning to give it another shot for some time, and just haven't. I saw John post that his next goal is to get overlayed waterfall plots working, which is very cool. And now that I have the BFD, I really need to make RoomEQ work.

[ThomasW]

REQW likes memory and a reasonably fast CPU.

Here's IIKEA's fullrange cal file

http://personal.inet.fi/private/ilkka/RS_calibrated.txt

[steve nn]

I've always seen the corrections more inline with what Steve posted. I'll have to email Doug Plumb about this

The correction numbers I posted were courtesy of Ilkka and might serve you well??

[wildfire99]

Yeah, the Nady has clipping lights, and I didn't notie anything. But, it is hard to look at the amp when you hear something funny comming from the sub. My eyes went straight to the sub.

In my experience, the Nady will start to clip a hair before the clipping LEDs will light. Your problem sounds like the one I had before. I ended up having my BFD (which was feeding the pro amp) misconfigured and it was clipping first. Adjusting it doubled the performance of the subs, or better.

On mine, feeding it studio levels (+4dbv), it's pushing max wattage just one click past the midline.

The second problem I had was positioning. It's definately interesting how various parts of the room can be excited by bass, just by walking around the room while it's being excited.

[---k---]

Well, the second sub is done! I celebrated by watching War of the Worlds. WOW! I got a butt massage. :B It didn't go real low, but we knew that. I didn't get a chance to hook up the BFD yet. Was busy fixing a few things and cleaning up the garage and house.

Fixing up things - I'm beginning to hate T-nuts just as much as Chris. While not really the T-nus fault, but I had a couple on both subs fail. I used a peice of scape plywood from work to back up the MDF to allow the t-nuts to grab. The plywood itself delaminated and split. Suck! I had to chip off the remaining plywood and sand the surface. I cut a couple peices of 1x4 to glue back there, but I didn't get the inside sanded perfectly level, so I just said screw it. I used a little gorilla glue and glued the t-nut into the MDF. I've seen people do this and say it works, so here is crossing my fingers.

Update on the crackling sound. I think I got that figured out. The foam insulation compresses over time. I think the driver had come loose due to the foam compressing, and the sound I heard was the driver slamming the the box and the bolt head.

Today I used some weather stripping from HD made for Auto/Marine. It worked MUCH better than the door crap. The adhesive was a lot stonger, and allowed me to bend it around easier. It also didn't bunch up like the door crap. Before I also had problems adhearing the weather stripping to the MDF. So to help, I smeared wood glue around the ring to seal the wood. Either this did the trick or it was the Auto weather stipping, but I got good adheasion.

The weather stripping was pretty stiff, so I layed the box on it's back and let the driver compress the weather stripping for a couple hours while playing some tunes. I was able to tighten the bolts slightly every so often. I think I'll check it over the next few days to make sure.

Anyway, I hooked them both up. I got some new speakers to try out the other day, so I needed to re-calibrate everything. I was in a hurry so I just used the Pio AutoCal. I have both amp channels up 2/3 the way, and the Pio set the sub channel at -2.0.

I had been listening to music all day long while I was in and out trying to clean up. It sounded pretty good. It definitily wasn't bloated or boomy.

I watched WoW. It was impressive. Pletty of bass. But, no real deep lows. It shook the house easily. This was still with the amp at 2/3 and the receiver at -1. So, I have plenty of volume, just need the EQ to push the low end up.

Getting there....
I'm very happy so far.

[ThomasW]

Good news... :T

As the I-Ching says perseverance furthers ....

[---k---]

I listened to a couple of CDs last night. The subs way outperformed the speakers, but that hopefully will get fixed tonight. Overall, the bass seemed a little lacking at times. We've all seen the frequency response, and know that I got some work to do with the BFD.

Before I hit the BFD, how do I go about tunning the amount of stuffing and is there anything else? I'm going to have to admit, that I'm a real beginner here. I've never had a big CD collection due to $$, and never had good equipment. I'm just starting to get that stuff now. So, I really don't know where to begin, or what I should be listening for. Am I best off just using ETF and REQ and looking at the FR graphs, or can you help me out and tell me what specific things I should be listening for? I'm willing to go buy any CD that will really show the differances.

Thanks,

[JonMarsh]

Pletty of bass. But, no real deep lows. It shook the house easily. This was still with the amp at 2/3 and the receiver at -1. So, I have plenty of volume, just need the EQ to push the low end up.

Getting there....
I'm very happy so far.

Uh, now, I'm not the subwoofer guru, I'm more the two channel channel music guy and crossover tweak head. But isn't there something a little contradictory about the above? Have you tried a quick measurement to see what you've actually got? "No real deep lows. It shook the house easily."

There's a little bit of a contradiction there....

~Jon

[ThomasW]

Ryan,

Give me a little time. I'm going to make a new sticky thread that deals with measuring the tuning frequency of ported and sealed subs. It will also cover both the scientific and non-scientific ways of tuning sealed boxes. It's going to take me a while to gather all the data into a single place

[TEK]

Ryan,

Give me a little time. I'm going to make a new sticky thread that deals with measuring the tuning frequency of ported and sealed subs. It will also cover both the scientific and non-scientific ways of tuning sealed boxes. It's going to take me a while to gather all the data into a single place

Looking forward to read all about it :T

[---k---]

Jon,
I have TONS of respect for you. I'm starting to read some of your design threads and getting excited about maybe tackling a small pair of bookshelf speakers this summer. But come on over and I'll show you what I mean. There was plenty of boom and things shaking. My wife was upstairs in our office space and said that the lid on printer/scanner was rattleing. Hehhehee. But, I think most of this was in the 30-40hz range. Based on my limited experance with my old 12" ported, it seemed like the 12" ported went lower freqencies. The Rocket Blast Off scene in Incredibles demonstates this. As the rockets are first starting up, there is a lot of low low rumble. I don't have nearly as much output as my old sub (one sub in in the exact same spot). And, based on what I've read online about some of the scenes from War of the Worlds, it seemed like I was missing something. Everyone descibes this low frequence erie sound. I never got anything that I would describe as erie. Just when something got slammed to the ground, I popped out of my seat a bit and went "wow". Maybe this is just my expectations? I don't know. But the plots above seemed to show little <30hz. And, a big boost at 20hz with the BFD or a LT was always part of Thomas recomendations. I don't think there is anything wrong with my subs right now. I just don't think that until I spend a little time tweaking the stuffing and a lot of time with the BFD, they aren't finished.


Thomas,
That would be very cool. I think there is a lot of stuff out there on sub placement, and I've read a ton of it. (placement of two big boxes like this becomes sort of a non-starter at this point.) But, I've never read anything that descibes how to listen, and what to listen for. What good bass sounds like. How to tell the bass from the sub from the mains. How to tune a sub with stuffing. How to accurately take the measurements using a computer (a lot of bad stuff out there though). Listening to mains, it is getting easier for me as I demo more speakers to pick out the differances, and be able to identify which is better. But, with subs it is so much more difficult. At the stores I never get a good listening session and they won't A vs B subs because they can't move the from room to room, and they all end up sounding the same to me. I think this will be very valuable. I'm really looking forward to it. Would that Pizza I owe you help to speed the process up.

[ThomasW]

Ryan,

I'm not going to cover all that stuff in the testing thread. I do have a general 'guide' for subs that's under construction. All the pages aren't linked together, but you can add page number where there aren't links at the bottom of the pages.

http://home.comcast.net/~thomasw_2/SubwooferSetupandEQpage.html

[---k---]

Thomas,
I just worked my way through your pages. Good stuff, presented in a very easy to read format. Well Done.

I think I got a somewhat of a handle on the computer testing. I just need to work on my ear.