Need help with choosing a budget subwoofer - some used options included

[rojo]

I should be able to pick up the bolts and t-nuts tomorrow, and I'll start working on it tomorrow evening or during the weekend.

Right after I printed the sketch for the carpenter, I decided to increase the port height from 3cm to 3.5cm, to decrease port noise, however I forgot to make the port longer so it ended up being tuned to 22hz instead of 20hz. It's just a 2db difference at 18hz and I don't know if I should bother with it any longer.

I'm also wondering if there's a point to getting a miniDSP for this giant box (it's 54 x 56 x 64).

I'm sure the tuning is good enough. As long as you didn't tune below the Fs of the driver, you're good.

Re: miniDSP, it is a great way to correct peaks in room response and to add some house curve. But as long as you perform the subwoofer crawl to find the best placement, you probably don't absolutely need a miniDSP to make the sub sound good.

 

[yonyz]

If I recall correctly, the Fs of the driver is 23.5Hz. Anyway, the frequency response on WinISD looks good in terms of SPL and port noise. Group delay isn't too great, but it's my understanding that this mostly matters for music.

As for doing the subwoofer crawl, it's not an option with such a big box in an apartment room. Its dimensions are specifically tailored for the only free corner in the room, but I'll hear it before I buy anything.

 

[yonyz]

Well it looks like I can't use most of the screw points on the plate amp. It has 10 screw holes, I can only use the 4 ones on the corners. I double checked the cutout on the cabinet and it's spot on like they specify on Parts Express' website: 10" x 6.25". And yet, when I insert the place amp into the cutout, I cannot align it so that there's space to drill the other 6 screw holes. I can see into the cabinet through the screw holes either on top or bottom of the amp, which means I cannot use at least the 3 on either side.

Rojo, can you please explain if you had a similar problem while installing the 500s amp in your build?

Is it OK to only use the 4 screw holes on the corners?

 

[rojo]

Well it looks like I can't use most of the screw points on the plate amp. It has 10 screw holes, I can only use the 4 ones on the corners. I double checked the cutout on the cabinet and it's spot on like they specify on Parts Express' website: 10" x 6.25". And yet, when I insert the place amp into the cutout, I cannot align it so that there's space to drill the other 6 screw holes. I can see into the cabinet through the screw holes either on top or bottom of the amp, which means I cannot use at least the 3 on either side.

Rojo, can you please explain if you had a similar problem while installing the 500s amp in your build?

Is it OK to only use the 4 screw holes on the corners?

As long as there's a good seal, I suppose you can get by with just the corner screws. It might be a good idea to seal the seam between box and amp from the inside with some silicone caulk or something.

 

[yonyz]

As long as there's a good seal, I suppose you can get by with just the corner screws. It might be a good idea to seal the seam between box and amp from the inside with some silicone caulk or something.

Good idea! I'll do that. Thanks.

 

[yonyz]

Introducing... "The Elephant in the Room":

And the FMOD crossover mess:

By the way, I was able to use all 10 screw holes on the plate amp, after all. It was a pita, though.
This is by no means a form of accurate measurement, but I definitely feel the bass even at 15hz.

Mission accomplished, I guess. Thanks for answering my endless questions, rojo!

 

[rojo]

Introducing... "The Elephant in the Room":

And the FMOD crossover mess:

By the way, I was able to use all 10 screw holes on the plate amp, after all. It was a pita, though.
This is by no means a form of accurate measurement, but I definitely feel the bass even at 15hz.

Mission accomplished, I guess. Thanks for answering my endless questions, rojo!

Very nice! Thanks for trusting my design advice. I know a DIY project can feel like a gamble. Buying a production model at your target price range would have been less risk, but also less rewarding. I'm sure the sub you built outperforms the Dayton, Klipsch, Bic, and other entry level subs you considered in the beginning. And you'll have the satisfaction of telling your friends, "I made this." Well done, @yonyz!

In case you're looking for some deep bass content, here's a DnB playlist to help you get your new sub broken in.

 

[yonyz]

Very nice! Thanks for trusting my design advice. I know a DIY project can feel like a gamble. Buying a production model at your target price range would have been less risk, but also less rewarding. I'm sure the sub you built outperforms the Dayton, Klipsch, Bic, and other entry level subs you considered in the beginning. And you'll have the satisfaction of telling your friends, "I made this." Well done, @yonyz!

In case you're looking for some deep bass content, here's a DnB playlist to help you get your new sub broken in.

Thanks for sharing the advice.
What did you do with your diy sub in terms of feet? Do you use a pad like the Auralex SubDude, or something else?

 

[rojo]

Thanks for sharing the advice.
What did you do with your diy sub in terms of feet? Do you use a pad like the Auralex SubDude, or something else?

Nah, I think I just used the rubber feet that came with the cabinet. Sorry I can't remember with certainty. It's been a while, and my sub is difficult to reach to verify. But I remember my cabinet was pre-drilled for those feet, and I'm pretty sure I used them so I wouldn't have to seal the holes.

 

[cel4145]

Introducing... "The Elephant in the Room":

And the FMOD crossover mess:

By the way, I was able to use all 10 screw holes on the plate amp, after all. It was a pita, though.
This is by no means a form of accurate measurement, but I definitely feel the bass even at 15hz.

Mission accomplished, I guess. Thanks for answering my endless questions, rojo!

Awesome sub!!!

 

[yonyz]

Hi,

A week ago I bought a Samson Go Mic and today I thought, why not use it to measure the subwoofer I built... Samson claims a flat response from 20hz to 18khz, which should be good enough.

So I opened the AVR setup and disabled Audyssey, and ran two test tones (sine waves) with REW, one at 40hz and another at 20hz. So at 40hz I got 61.7db, and at 20hz it's 43db. With no tet tones playing, the measured SPL (which is not calibrated) in the room is 38db.

Did another test at 30hz, and I get 47.5db.

It looks like there's a rather steep roll off way too soon, like the sub barely produces 30hz properly.

 

[BoredSysAdmin]

Samson claims a flat response from 20hz to 18khz, which should be good enough.

So I opened the AVR setup and disabled Audyssey, and ran two test tones (sine waves) with REW, one at 40hz and another at 20hz. So at 40hz I got 61.7db, and at 20hz it's 43db. With no tet tones playing, the measured SPL (which is not calibrated) in the room is 38db.

Did another test at 30hz, and I get 47.5db.

It looks like there's a rather steep roll off way too soon, like the sub barely produces 30hz properly.

Sorry, but you're using an axe to hammer nails. It's possible, but won't be very accurate. What you really need to measure sub response is a special measuring (preferably calibrated) microphone like this these:
http://www.parts-express.com/cat/measurement-microphones/2057

 

[yonyz]

Sorry, but you're using an axe to hammer nails. It's possible, but won't be very accurate. What you really need to measure sub response is a special measuring (preferably calibrated) microphone like this these:
http://www.parts-express.com/cat/measurement-microphones/2057

Fair enough. How about using an Audyssey mic (assuming there's a way to use it with a computer)?

Edit:

EMM-6 vs Audyssey XT mic:

Not too bad, right?

 

[BoredSysAdmin]

Fair enough. How about using an Audyssey mic (assuming there's a way to use it with a computer)?

Don't think it would do ether.
I am assuming it has a cheap mic and without having its calibration profile - it's would all guess work.
This is the cheapest option I would recommend:
http://www.ebay.com/itm/Radio-Shack-33-2050-Analog-Display-Sound-Level-Meter-Excellent-Condition-/262793091085 - Specifically older analog version, not more current digital one with lcd screen. It's fairly accurate and it's calibration profile is available online.
It won't measure 15hz bass , but should be fine above 30hz with cal file.

 

[yonyz]

Don't think it would do ether.
I am assuming it has a cheap mic and without having its calibration profile - it's would all guess work.
This is the cheapest option I would recommend:
http://www.ebay.com/itm/Radio-Shack-33-2050-Analog-Display-Sound-Level-Meter-Excellent-Condition-/262793091085 - Specifically older analog version, not more current digital one with lcd screen. It's fairly accurate and it's calibration profile is available online.
It won't measure 15hz bass , but should be fine above 30hz with cal file.

Based on what I've read, the Audyssey mic is +-2db at the frequency response that Audyssey works at, which I believe is 16hz and above. I think it's worth a shot considering I already have one.

That RadioShack mic has a shipping cost of $36 (I'm located in Israel), so it's almost $60 overall.

 

[yonyz]

Hey, check this out. Apparently the Samson Go Mic wasn't actually flat because it was set to Cardioid mode, where the FR is actually 80hz-18khz.

According to the manual, the Go Mic's Omni mode is 20hz-20khz, and pretty flat too:

So I re-did the SPL test (with the Generator tool) on REW, and here are the results near my listening position (the Go Mic cable isn't long enough):

While 20hz is still fairly loud, notice the weird dip at 50hz. Maybe it's my room... Or maybe the Go Mic is useless for what I'm trying to do.

 

[shadyJ]

Its your room. you have a null caused by cancellation, and that type of dip is a common feature of that. Only way to get rid of it is too move the listening position, move the subwoofer, or get another subwoofer which can shore that null up.

 

[yonyz]

Its your room. you have a null caused by cancellation, and that type of dip is a common feature of that. Only way to get rid of it is too move the listening position, move the subwoofer, or get another subwoofer which can shore that null up.

Thanks! What about everything else that can be seen on the graph? It's not just 50hz, but most of the graph is far from flat. Strangely, 20hz is louder than anything up to 60hz. Is this all my room?

 

[rojo]

Thanks! What about everything else that can be seen on the graph? It's not just 50hz, but most of the graph is far from flat. Strangely, 20hz is louder than anything up to 60hz. Is this all my room?

Yep, this is at least partly room gain. Most of the time this sort of slope is desirable, although it's really up to user preference how steep that slope should be. Another part is just the position of the mic. 18 - 20Hz is roughly the same SPL as 60 - 70Hz. The 60 - 70Hz peak could be the result of a room mode where waves combine to form a stronger SPL.

Thing is, I bet if you move the mic 6 inches in any direction, the response will significantly change. That dip at 50Hz might move to 60Hz, or could disappear altogether.

Most importantly, how does it sound to you? The dip at 50Hz is probably narrow enough to be inaudible, but that mode from 60 - 70Hz could make the sub sound boomy. Did you ever get a miniDSP? If your PC is the only source, you could use the freeware Equalizer APO to manipulate that response curve as you see fit.

 

[yonyz]

It sounds fine to me, I just wanted to see if my subwoofer meets the expectations I had when I was building it. It looks like the -3db point with this sub in my room is at 14.5hz, which is cool.

I used a USB extension cable to place the microphone where I sit to watch movies/TV shows. The new measurements can be seen below The blue graph is with Audyssey XT set to ON, and the purple graph is with Audyssey XT set to OFF.

Notice that the dip at 50hz is gone when Audyssey is OFF, but then I get more peaks at higher frequencies. I think that it's best to keep Audussey on, and try to fix that dip at 55hz with software. I assume it would be easier than trying to fix the multiple dips that occur when Audyssey is off.

Now here are the same measurements, with 1/3 octave smoothing. This demonstrates what I said above, that the FR (up to 200hz, which is all I've tested) is overall better with Audyssey being enabled.

Overall, though, the FR is still far from flat (which I assume is not necessarily undesirable).

Lastly, a graph of a 0hz-22khz sweep, with 1/3 octave smoothing applied (RED - Audyssey enabled; BLACK - Audyssey disabled):

Again, it's not flat, but it sounds good to me.
Let me know if I should upload other graphs.

Edit: So after spending this entire Saturday on messing with measurements and stuff, I ended up installing the trial version of Dirac Live. It was as quick and easy to set up as Audyssey, and the result is a much flatter response (which you are able to tweak to your own preferences). I did lose a lot of overall volume (7db) and audio sounds more "tamed" and less explosive, but the bass is more even now and not "bloated". That dip at 55hz is gone, by the way. I definitely wouldn't spend the ~$600 it costs, though. It's just an insane price to pay for such software.