Sanity check sonotube sub DIY project

[HMenke]

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

She doesn't know how lucky she is that there's no available cavity for an IB next to my HT! :twisted:

Thomas, I've been meaning to ask you if you have any thoughts about the dip in my uncorrected response curve. Is it a null, or do I just have three peaks: 1) port tune 2) first room mode 3) second room mode? Also, how does the low end extension look to you compared to the Unibox model expectations?

On my sub EQ strategy, I boosted the null area. Would it be better to cut all peaks? Subjective sound quality has changed - maybe not for the better - since the EQ'ing. The blend with my mains doesn't seem as smooth.

Henry

[ThomasW]

Looks like the box tuning is spot on, and yep you've go a nasty null just above it.

Yes I'd play with cutting the frequencies around the null to see if that sounds better than using so much boost.

Use a separate bank of filters so you can A/B the different settings.

I realize that means getting up from the chair since midi won't push those buttons, but we must make some sacrifices for this hobby ...:wink:

[HMenke]

I realize that means getting up from the chair since midi won't push those buttons, but we must make some sacrifices for this hobby ...:wink:

Jeesh, it was bad enough that I had to dive into the tube to work on the dampening material, now I have to get up off the couch too? Oh, the humanity! :lol:

I'm glad that the box tuning looks good. If you imagine the curve without the room mode peaks and the null, you can sort of see that the characteristic ported box "shelf" - slowly dropping off to the left before rolling off altogether - is hiding in there. I don't think I should boost above where the curve naturally wants to lie. I like the idea of A/B filter banks; that would be a slick way to dial it in.

[---k---]

Jeesh, it was bad enough that I had to dive into the tube to work on the dampening material, now I have to get up off the couch too? Oh, the humanity! :lol:

Depending on how far you sit from your BFD, maybe you can reach it from your chair with a broom handle.

[Valorum]

Congratulations Henry, looks like a great success :T

[HMenke]

Thanks, I'm really pleased with what can be accomplished when you know the right people! I saw you have a project thread going too. All I can say is these guys know their stuff and can help you avoid problems or straighten you out if you foul something up! ;x(

I went home last night intending to run some more curves. When I walked into my HT room, it still had "that new sub smell"! So I ended up just watching movies and enjoying the new sub!

[ThomasW]

Henry,

You're quite welcome. And don't worry there's plenty of time to make measurements, right now enjoy your new toy.... :B

[Bent]

people say mdf in unhealthy...
but I like that new sub smell too.

[HMenke]

people say mdf in unhealthy...
but I like that new sub smell too.

It's a good thing "normal" people don't read these forums, or we'd all be committed! :B

I have formulated a recipe for "that new sub smell" that could be bottled and sold on the internet for people who just bought or are selling an old sub:

0.25 oz. 3M adhesive spray
0.25 oz. black spray paint
0.25 oz. wood glue
0.25 oz. Liquid Nails
0.25 oz. latex caulk
0.25 oz. polyurethane stain
0.10 oz. MDF dust
0.10 oz. acoustic foam, finely ground
0.10 oz. black acrylic carpet fibers
0.05 oz. solder resin

[collo]

Just have to come up with a snappy name. It would give all those commercial "male" scents a run for their money... :P

[Valorum]

Eaux De Sub
For when you need to shake things up

[HMenke]

CAD model of this sub

In case anyone would like to build a sub like this or have a starting point for CAD modeling, here is the CAD model of this sub for download:

http://home.insightbb.com/~henry.menke/Sonosub_300L_24_inch_dia_tube.dwg

This is an AutoCAD LT 2002 drawing file. You can view it in Explorer (looks a little weird with a white rather than black background) but only edit or queery the geometry in AutoCAD. If you can import the generic CAD format .DXF into another CAD program, here is a .DXF file of the same model:

http://home.insightbb.com/~henry.menke/Sonosub_300L_24_inch_dia_tube.dxf

[Kingdaddy]

If anyone is interested and has Autocad 2000 (full version) and up, I have a nice 3-D drawing of mine.

[Brian Bunge]

Speaking of AutoCAD, anyone have a recommendation for a decent book to learn AutoCAD? I've got a full version of it loaded on my laptop, but just haven't had the chance to learn it.

[HMenke]

Speaking of AutoCAD, anyone have a recommendation for a decent book to learn AutoCAD? I've got a full version of it loaded on my laptop, but just haven't had the chance to learn it.

Have you checked if there is a tutorial with it? Some CAD programs have you go through the process of drawing something and you learn by doing.

[HMenke]

Could the dip in my room response (see measurement graph previous page) be caused by the presence in the room of my old ported subwoofer? I have to leave it in the room for the time being, until I get the kids' game room completed. The old sub (Paradigm PS-1000) as measured in this room seemed to be tuned around 30-35 Hz.

[Dennis H]

When I was learning AutoCAD many years ago, I went to the local community college and took some classes. The textbook was "Inside AutoCAD" and it was pretty good back then. It probably still is but I don't have any recent experience. They come out with a new version of the book every time there's a new AutoCAD release so you'd need to make sure you got the right one. That said, check out your local community college. It's hard enough a program that there's really no substitute for hands on practice and an instructor who knows what he's doing.

[ThomasW]

Could the dip in my room response (see measurement graph previous page) be caused by the presence in the room of my old ported subwoofer

Nope, sorry that would be way too easy.....

The thing to do is move the new sub to a different location and run a quick set of measurements for comparison.

[HMenke]

:roll: Wishful thinking...

I'm pretty much stuck with my location at the LR. Up front no room between the screen and L-R speakers, RR is the door, center rear is my PJ.

I might try a 180 degree phase shift, but really I may be worrying about nothing. I've been dialing in the EQ and it is looking real flat and SQ is superb even though I have +15dB boost at one filter. Normally I would not want more than 6dB boost. Tonight I watched the Fast and the Furious on DTS, which I consider a reference soundtrack and it was the best I've ever heard it in my HT. I am loving the transient impact and effortless power down low.

[HMenke]

More listening impressions

Since I don't have my active high pass filter built yet, I have been consciously avoiding "subwoofer workout" movies. Well, curiosity got the better of me and I demo'd "Master and Commander" and "War of the Worlds". All I can say is "Woah..."

I had no idea just how intense the LF content is getting in some movies these days. I was dumbfounded by the visceral impact that this sub adds to the experience. I mean, when you are accustomed to an "intermediate" commercial sub like my old PS-1000, you just aren't even aware of what you are missing. I was living like an animal compared to what I have now.

The RLp-15 seemed to handle these movies well at the levels I demo'd. There are two cannon fire transients in MaC near the end of the opening battle sequence that do have me worried a little though. I wasn't able to tell if they were just simply very intense, or if the driver was getting a little distressed, because the LF vibrations seemed to have even greater intensity than the other transients that came earlier. I put my fingers lightly on the surround during this scene and it did not seem like the cone was going into overexcursion, although certainly it moved more than any driver I've ever seen before, maybe 1/2" or so.

Where MaC is great for experiencing transient impact, WotW is fun due to the extended amount of time you get to experience LF activity. When that machine comes out of the ground, and when the death rays fire...it just transfixes your senses.

[chasw98]

Fun, isn't it

[SteveCallas]

Since I don't have my active high pass filter built yet, I have been consciously avoiding "subwoofer workout" movies. Well, curiosity got the better of me and I demo'd "Master and Commander" and "War of the Worlds". All I can say is "Woah..."

Yeah, with a sub like this, the high pass really isn't needed at all for normal or even spirited playback - it's use is reserved for protecting against the absolute extremes of stupidity. With a normal ported sub, it functions as more of a necessity. I believe the combination of processor low frequency rolloff, amplifier low frequency rolloff, amplifier single digit brickwalls, and "bottomless" drivers all add up to designs like this being pretty safe.

But for those times when your idiot buddy is over and you go to use the bathroom for a minute, only for him to crank the amp and master volume all the way up because he "wanted to see if he could crack the ceiling", you'll be glad you have a high pass in place 8O Luckily for me, that's not based on actual events.

[HMenke]

Yeah, with a sub like this, the high pass really isn't needed at all for normal or even spirited playback - it's use is reserved for protecting against the absolute extremes of stupidity. With a normal ported sub, it functions as more of a necessity. I believe the combination of processor low frequency rolloff, amplifier low frequency rolloff, amplifier single digit brickwalls, and "bottomless" drivers all add up to designs like this being pretty safe.

But for those times when your idiot buddy is over and you go to use the bathroom for a minute, only for him to crank the amp and master volume all the way up because he "wanted to see if he could crack the ceiling", you'll be glad you have a high pass in place 8O Luckily for me, that's not based on actual events.

That kind of stuff can and does happen! I remember the time a guy was at my house (I was a teenager at the time) and he grabbed a shotgun off the rack in my room and pointed it at me! :E Fortunately I'm at an age now where even the idiot buddies have acquired at least some common sense.

[HMenke]

Chuck, an update on my solid-state relay. It definitely works, but an issue has cropped up. It seems there must be some non-linearity of the AC power waveform, probably around the zero crossing. Well, for some reason this is inducing a buzz in the toroidal transformer of the amp. It comes and goes and was driving me nuts. I fingered the solid-state relay as a possible culprit, so I plugged the unit directly into an unswitched outlet. It has been running silently ever since. I'll either have to go with a mechanical relay, or just throw in the towel and leave it switched on all the time.

[chasw98]

Interesting. After your idea of the SSR, I grabbed one at work at and set it up to use in my system. It is working quite well. It is switching all 3 of my Behringer amplifiers and I can't hear any buzzing. Is it a mechanical buzz or is it audible through the speaker?

[HMenke]

Interesting. After your idea of the SSR, I grabbed one at work at and set it up to use in my system. It is working quite well. It is switching all 3 of my Behringer amplifiers and I can't hear any buzzing. Is it a mechanical buzz or is it audible through the speaker?

It's definitely mechanical at 60 Hz. I pulled the cover off (nice feature of the amp: the whole top sheet metal comes off with six screws - with the way it's mounted you can get at everything inside) and listened through a paper tube to each area and it was the transformer or something under the transformer. I pushed on it and the buzzing didn't stop or change pitch. It seems to be a very well made toriodal unit, tightly constructed and potted in the center. I do know that there is a single large threaded stud that holds it in place; the stud sticks out the bottom and has a nut on it. I might get adventurous and pull the transformer to see what if anything could be underneath it that may be buzzing. It's possible it could just be the bottom side windings buzzing against the bottom cover plate. If so, some well-placed felt stickies might cure the issue.

[chasw98]

Now obviously, while you have the cover off, insert the SSR and take it out to see if it comes and goes. The other idea that occured to me was to set your amp on a level surface. You did mount it against a wall, right? Just a thought.

[HMenke]

Yes it is there when powered by the SSR and not when powered right off the line. Tomorrow I'll pull it out of the wall bracket and see what's what...have to do that anyway to get at the xformer mounting nut on the bottom.

[SteveCallas]

Cheater plug?

[ThomasW]

DC in the line will cause toroidal trannys to hummmmmmmm

[HMenke]

Cheater plug?

At first I did get 60Hz hum from the sub due to running the inputs unbalanced. I am using a cheater plug on the sub amp and also on my BFD. Due to shock hazard concerns I only use cheater plugs with GFCI protected circuits.

DC in the line will cause toroidal trannys to hummmmmmmm

What's strange is how it only does it 50% of the time, usually after it has been on for a period of time. I think A) my solid state relay isn't giving me a clean sinusoidal waveform at the zero crossing - which means some HF and maybe DC is in there and b) there's something under the transformer that can buzz under certain conditions. Man I wish I didn't give away my O-scope last year...

I bought the SSR pretty cheap at surplus and judging from the looks of it, it could be 20 year old stock. Maybe the newer ones pass the current with minimal distortion. Chuck what model are you using?

[chasw98]

I will crawl behind the rack this afternoon and check.

[HMenke]

Thanks for checking.

I just pulled off the transformer and there's nothing to buzz under it. It is very well-made with a 3/16" thick closed cell foam pad isolating it from the case.

Since it didn't buzz before, I am starting to think the SSR is bad. I could be getting only half wave power out of it. It's a 15A rating; I probably should go up to 20 or 25A.

[swithey]

At first I did get 60Hz hum from the sub due to running the inputs unbalanced. I am using a cheater plug on the sub amp and also on my BFD. Due to shock hazard concerns I only use cheater plugs with GFCI protected circuits.

Not to hijack this thread -- but I have had a concern with unbalanced design of the Behringer amps vs a standard dedicated "balanced" plate amp. So, with an unbalanced audio, the 60Hz Hum is pretty standard? Is the "cheater" plug the only solution? If I want to make it balanced, is there a external box/circuit I can build DIY or buy inexpensively that will balance the audio so a cheater is not needed? Steve's GFI protection is an option if a cheater plug is the only fix, but would rather do it "grounded" if possible.

In my setup I am running a dedicated CLEAN (well, as clean as I can get) 20amp circuit for my subs. I was concerned about hum and I was hoping this dedicated circuit would significantly reduce any possibly of hum.

Thanks,

Steve

[HMenke]

From my limited experience (Behringer DSP1124P Feedback Destroyer Pro equalizer and Samson S700 amp) it seems that most "pro" audio gear is intended to be run balanced through XLR or 1/4" TRS connectors. When connecting up to unbalanced consumer audio gear using RCA connector adapters, 60 Hz hum gets introduced into the unbalanced signal ground due to the chassis of the pro gear being earth grounded via a 3-prong plug (as opposed to consumer gear which is double-insulated and floating with a 2-prong plug).

There are some unbalanced to balanced converters, and some hum blockers out there, but I have no experience with them because they cost too much IMO. I have found the most cost-effective and simple way to deal with the issue is to just lift the ground of the pro gear and maintain safety with a GFCI outlet. Normally, if the pro gear shorts the hot to the case internally, the grounded case causes the panel breaker or fuse to trip instantly, protecting life and property. The case can never rise to the hot line level. However if you lift the ground with a cheater plug, that protection is lost. The entire case could become live and electrocute you if you touch it while grounded.

With GFCI protection, if the pro gear ever shorts the hot to the case internally, you won't get electrocuted if you touch it while grounded, because the GFCI will trip at ~ 4...7mA current imbalance between hot and neutral, indicating that a ground fault has occured. You will still feel a shock but you will not get injured by it.

[chasw98]

Not to hijack this thread -- but I have had a concern with unbalanced design of the Behringer amps vs a standard dedicated "balanced" plate amp. So, with an unbalanced audio, the 60Hz Hum is pretty standard? Is the "cheater" plug the only solution? If I want to make it balanced, is there a external box/circuit I can build DIY or buy inexpensively that will balance the audio so a cheater is not needed? Steve's GFI protection is an option if a cheater plug is the only fix, but would rather do it "grounded" if possible.

In my setup I am running a dedicated CLEAN (well, as clean as I can get) 20amp circuit for my subs. I was concerned about hum and I was hoping this dedicated circuit would significantly reduce any possibly of hum.

Thanks,

Steve

Follow proper and sound grounding principles (this might mean building your own cables) and you will not have a problem. You will get 60 Hz hum whenever there is a difference in the ground potential. This means everything should emanate from one common ground point, balanced lines, unbalanced lines, AC ground, etc. Do not give a signal the chance to choose more than one path to ground.

[ThomasW]

There are basically two kinds of 'balanced' gear.

One is called 'dual differential'. This stuff is expensive and has the same active circuitry on the (+) and (-) runs with the ground obviously separate.

The other kind simply has input/output transformers that convert the SE signal to a balanced one.

Having either balanced design doesn't inherently eliminate ground loops. It does lower the noise on the interconnects and makes it much easier to have very long line level runs.

[swithey]

From my limited experience (Behringer DSP1124P Feedback Destroyer Pro equalizer and Samson S700 amp) it seems that most "pro" audio gear is intended to be run balanced through XLR or 1/4" TRS connectors. When connecting up to unbalanced consumer audio gear using RCA connector adapters, 60 Hz hum gets introduced into the unbalanced signal ground due to the chassis of the pro gear being earth grounded via a 3-prong plug (as opposed to consumer gear which is double-insulated and floating with a 2-prong plug).

There are some unbalanced to balanced converters, and some hum blockers out there, but I have no experience with them because they cost too much IMO. I have found the most cost-effective and simple way to deal with the issue is to just lift the ground of the pro gear and maintain safety with a GFCI outlet. Normally, if the pro gear shorts the hot to the case internally, the grounded case causes the panel breaker or fuse to trip instantly, protecting life and property. The case can never rise to the hot line level. However if you lift the ground with a cheater plug, that protection is lost. The entire case could become live and electrocute you if you touch it while grounded.

With GFCI protection, if the pro gear ever shorts the hot to the case internally, you won't get electrocuted if you touch it while grounded, because the GFCI will trip at ~ 4...7mA current imbalance between hot and neutral, indicating that a ground fault has occured. You will still feel a shock but you will not get injured by it.

Thanks so much for your explanation. So what you are saying is "to lift the ground and eliminate the hum" use a cheater plug but only on a GFCI protected circuit (at the breaker) for safety purposes. I can do that very easily since I have not purchased my breakers yet. Thanks!

Steve

[swithey]

Follow proper and sound grounding principles (this might mean building your own cables) and you will not have a problem. You will get 60 Hz hum whenever there is a difference in the ground potential. This means everything should emanate from one common ground point, balanced lines, unbalanced lines, AC ground, etc. Do not give a signal the chance to choose more than one path to ground.

Then, I believe I have this covered. All (3) sub outlets are a "home-run" (not daisy chained together like standard electrical) back to a single box. The (3) runs are for HT front, HT rear and HT Wiring closet -- just covered all the bases for whatever direction I go with -- plate amp or seperate amp (in the closet). We'll just play it by ear and see what happens when I get my hooked up. Thanks again guys!

Steve

[swithey]

There are basically two kinds of 'balanced' gear.

One is called 'dual differential'. This stuff is expensive and has the same active circuitry on the (+) and (-) runs with the ground obviously separate.

The other kind simply has input/output transformers that convert the SE signal to a balanced one.

Having either balanced design doesn't inherently eliminate ground loops. It does lower the noise on the interconnects and makes it much easier to have very long line level runs.

Thanks Thomas. I'll do some resarch on this "just in case" I get a hum on my final setup.

Steve

[HMenke]

Thanks so much for your explanation. So what you are saying is "to lift the ground and eliminate the hum" use a cheater plug but only on a GFCI protected circuit (at the breaker) for safety purposes. I can do that very easily since I have not purchased my breakers yet. Thanks!

Steve

That's what I do. Keep in mind though that the GFCI doesn't 100% eliminate risk, since it has to be tested regularly to make sure it's working, but it allows you to reduce the risk if you chose to lift the ground. I would probably not lift the ground if there is a likelihood that a person touching the equipment would be grounded (water pipe nearby, wet area on floor, etc.). In my case there is no solid ground nearby and the area is very dry and well-insulated by the flooring.

[collo]

Do not give a signal the chance to choose more than one path to ground.

There are plenty of articles on reducing hum from eath loops. Google is your friend.
Here's one I wrote a while back:

http://www.users.bigpond.com/bcolliso/earth-loop.htm

[chasw98]

I will crawl behind the rack this afternoon and check.

OK, I pulled the rack out and here is the unit I am using. A Potter & Brumfield SSRT-240A25. It is rated for 240 VAC and 25 Amps.

[HMenke]

OK, I pulled the rack out and here is the unit I am using. A Potter & Brumfield SSRT-240A25. It is rated for 240 VAC and 25 Amps.

Thanks Chuck, I really appreciate the effort you made for me. ;x( I think it's the 25A that is the key. I have a feeling the inrush of the amp is killing the 15A SSR.

[HMenke]

Just ordered it from Jameco (best price and in stock):
RELAY, SS
SSRT-240A25, 25A 240VAC AC-IN
Jameco#:553035
Qty 1: $29.65
Shipping: $5.95
Total: $35.60