Twin Tall Floor standing 12 inch Subwoofer Build

[toffkanda]

Hello all,
I'm fairly new to this forum and have been studying several threads for a while now. I've finally plucked courage to share my first software guided build so you all can run a critique that will enable me do better next time. I have built a pair of floor standing passive 12 inch Subwoofers as well as the surround speakers that go with it (5.2). I desired to experience frequencies around 20Hz and below but with as little box volume and floor space as possible. I chose the 12 inch Epik sentinel Subwoofer drivers (not Epic!) because it seemed to my untrained mind to be built for as low a frequency output as possible in the smallest enclosure (not to mention that it was going for a bargain price). Here are the T/S parameters

After spending some time on WinISD, it seemed to me that I could get away with a 3cuft enclosure which with a 4th order LR crossover at 80Hz appeared to give me a fairly flat 3dB FR range from 18 to 85Hz when tuned to 19.5Hz.
Ports:
Dual 3.375" diameter ports seemed ok to me. Larger (4") ports would have been better airspeedwise but would have resulted in longer ports with audible resonance and a larger box than I intended. I reckoned that with 600 watts ceiling on power (since I was not planning for high SPL but a bit of a subsonic experience which I've never had) I might make do with this port size.
SPL:
The driver has a fairly low efficiency which is worsened by its highest output being at upper subwoofer frequencies (125Hz) which will mostly be cut off by the crossover.
Group Delay:
This appeared to get worse as one tuned higher (i.e 20Hz and above) for the same enclosure volume. On the other hand tuning lower seemed to reduce SPL.
Port Air Speed:
WinISD's port speed at 600 watts looked rather high but I figured that the maximum possible flaring I could achieve at the ends of the ports should shave off up to 8m/s of air speed. Core compression however may be a serious issue from 400 watts on. I couldn't think of any other way round this since I was reluctant to put more than 12.5Hz of 2nd order highpass on it for fear of limiting subsonic performance. In the process of wood work, I discovered that the maximum flaring looked really good and so was adopted as design aesthetics.

Wood Work:
I worked with a Carpenter on this project (not being hands-on myself) but I designed and directed every stage of the work. This is because skilled workmanship and necessary tools are hard to come by in my zone and I needed to maintain quality and find ways around unavailable tools. The boxes were made based on WinISD plans long before the drivers were shipped in. It was left to see whether the performance would match up with the simulation. Flush mounting was a huge challenge because it was done after the fact as the external driver diameter was not known at the time of cutting out the driver seating (a substitute driver was being used in the box while Epik driver shipping was delayed).
Please pardon the quality of workmanship (and planning too).

.

 

[toffkanda]

Marine plywood was used for all the enclosures (surround speakers included). Because of the fairly inadequate wood working skills and equipment, panels were joined by joined with screws and wood glue while caulking was with a mix of wood glue and fine saw dust. Flaring was done with rough sandpaper glued to an improvised cylindrical bit on a drilling machine which could then be manipulated into narrow spaces. Front box edges were rounded with a wood plane and the entire body ground with a sanding machine which was fitted with a plywood disc to which rough sandpaper was glued. The baffle was a double layer of 3/4" plywood for reinforcement, deep port flaring and flush mounting. The box spaces were stuffed to a moderate density.

 

[toffkanda]

MO

The finishing was a sprayed-on matte black done after filling and sanding with automobile body filler . What I found remarkable was the final look of the speakers. This design I feel could be used for bigger boxes with similar floor space saving as sonotubes

 

[Seth=L]

@toffkanda

Do I see a Lexicon processor?

 

[toffkanda]

Performance :
This is the first time I have extensively used WinISD and other software for making a subwoofer. I fear that I may have been seriously off course in my interpretation, deduction and assumptions while planning this project. That’s why I'd really appreciate corrective contributions to show me how I could do better. I'll say thanks in advance. I have an old Grundig audio receiver and a dated trio amplifier probably providing less than 100 watts max, to which I have added a behringer fbq6200 31 band graphic equalizer so I may not be able to optimize the sub's capacity for now although I am so impressed by the profound sofa vibration when I watch some movies. Also, using some you-tube downloaded test tones, frequencies within the simulated FR range appear to be equally emphasized except for some awful room gain between 50 and 80Hz (small room) which has been ameliorated with the equalizer. I don't have access to any audio testing equipment at the moment for a more objective assessment. I will need to get a good avr and a bigger amp to be able to enjoy what I suspect the subs and indeed the complete 5.2 surround system is capable of.

 

[toffkanda]

Hello Seth=L,
Do you refer to the electronics in my sitting room or to my grammar?

 

[Seth=L]

Hello Seth=L,
Do you refer to the electronics in my sitting room or to my grammar?

Electronics.

 

[toffkanda]

Electronics from top down ;
Satellite TV cable decoder
Behringer graphic equalizer
Grundig digital audio receiver
Trio integrated stereo amplifier
Samsung Blu ray player
............ Nothing interesting really.

 

[TheWarrior]

So how do they sound?

 

[toffkanda]

Sorry for the late reply just woke up. It was bedtime in my time zone.
Maybe I haven't listened to a lot of good subs but I'm really impressed with these. I watched a movie earthquake 12.0(?) and there were scenes of sustained intense low frequency and it felt as if I was having butt massage from the sofa. There was a frequency point at which I heard the drivers sound as if they were farting a higher octave superimposed on the music, yet looking at the drivers you realise they haven't begun to approach their excursion limits. I read and thought about it and I feel this is what is meant by clipping especially as the gains and volume of all the appliances involved were near max setting. For music there is a lot of house tremor with glass louvre/ceiling rafter rattling. Rap music from artistes like future appear to have a lot of tactile content with the sleeves of one's trousers trembling contrary to the assertion on most forums that such content isn't there. There is also a percussive effect that saturates the room when beats are rendered. All these with a small amp and am wondering how it would perform with the appropriate size of amp.

 

[Bizarro_Stormy]

... I heard the drivers sound as if they were farting...

Whoops, my bad...

I get a bit gassy when exposed to low frequency sound waves...

Won't happen again...

 

[TheWarrior]

Sorry for the late reply just woke up. It was bedtime in my time zone.
Maybe I haven't listened to a lot of good subs but I'm really impressed with these. I watched a movie earthquake 12.0(?) and there were scenes of sustained intense low frequency and it felt as if I was having butt massage from the sofa. There was a frequency point at which I heard the drivers sound as if they were farting a higher octave superimposed on the music, yet looking at the drivers you realise they haven't begun to approach their excursion limits. I read and thought about it and I feel this is what is meant by clipping especially as the gains and volume of all the appliances involved were near max setting. For music there is a lot of house tremor with glass louvre/ceiling rafter rattling. Rap music from artistes like future appear to have a lot of tactile content with the sleeves of one's trousers trembling contrary to the assertion on most forums that such content isn't there. There is also a percussive effect that saturates the room when beats are rendered. All these with a small amp and am wondering how it would perform with the appropriate size of amp.

Haha, I was wondering what those long pipes were going to sound like!

First, why did you choose to make two long (seemingly random length) PVC pipes inside the enclosure? I'm not in anyway trying to insult you. I genuinely am curious as to why you chose to build those in, even with a 90 deg turn.

You chose a great woofer, but you need to educate yourself a bit more to get the most out it!

First, your box is entirely too large for a driver with such low QTS.

Here is an Audioholics article on the Epik Sentinel:
http://www.audioholics.com/subwoofer-reviews/epik-sentinel/purchasing-packaging

You will see the sub was specially designed to be as small as possible while still delivering true 20 hz tones. I feel bad considering the work you put in to grinding out your ports, but the original was built with a 'slotted port'. Its the width of the front baffle, and only an inch or two tall.

My best advice will be to replicate the original sub's design! Your box looks very handsome, and I am sorry for the time you've put in to it already, but speaker design is much more than just putting a driver in a box!

 

[toffkanda]

http://forums.audioholics.com/forums/threads/best-curve-for-my-twin-12-inch-subwoofers.95837/
Warrior please take a look at this thread. There you said the exact opposite of what you are saying now about this same project. When I was looking for more information before the build, you shut me down.

You said you didn't mean to be insulting but your last sentence is an insult. You can do a critique without being condescending.
First, the article you refer me to I have read several times over and so with every other article available concerning this driver.
This project was not intended to copy the Epik sentinel verbatim,neither am I the first to use this driver after Epik (http://www.ccmostwanted.com/store/Custom-Built-Epik-Home-Theater-Subwoofer_151726708163.htmll).
The box in this thread is even bigger than mine. This was not random, put it WinISD and show me the error of my ways.
Second, the optical illusion of long pipes in a long box leads you to believe it was of seemingly random length. The lengths are exactly 37". Added to half the thickness of both flanges gives a total length of 38.125". I won't have resonance closer than 182Hz. It's cutting it thin I know but people have done worse and gotten away with it. If you read across forums you'll see that.(http://forums.audioholics.com/forums/threads/simple-12-infinity-kappa-vq-midq-plans.45528/).
As for 90 degree turns see here http://www.subwoofer-builder.com/snorky-gal/snorky-gallery.htm. If you ask me, a lot was wrong with the Epik sentinel in its original form hence the early discontinuation of that line despite its wide acclaim. In the same article you refer me to, you can can perceive in the listening comparison, serious group delay and plate amp modifications ( buzzing) required to make it a go. The port outlet surface area was 25% less than with these pipes.
The transient distortion I heard on my subs I studied carefully, blocking the ports and listening. It was from the driver itself which led me back to some more research. http://www.talkbass.com/threads/speaker-farting.635520/, http://forums.anandtech.com/showthread.php?t=152887, http://www.avsforum.com/forum/89-speakers/1399048-what-does-clipping-sound-like.html. There is no relationship whatsoever with the port length in this matter. By the way that same distortion sound was on the front left and right speakers when I set them to large (on the receiver). I don't know anywhere near as much as you do but not every newbie is an ignoramus and even if they are, they should be helped as much as patience can allow. I only seek fair criticism.
By the way I don't know why you seem to be pitying me. I'm enjoying these subwoofers immensely, and more every day. I also discovered that I over-enhanced the 20hz on the equalizer. This has since been corrected and I have never heard that sound again.

 

[TheWarrior]

@toffkanda whoa sorry! In that thread you can see I was talking about a different driver. Your first post did not specify, so I linked a driver that I found.

If you knew I was talking about a different driver, then so sorry, but you can't fault me for your choosing to take my recommendation for a different driver! I have no idea what WinISD parameters you used, but your 'farting' subwoofer, as seen in the link you posted, is caused by the driver exceeding its limits. Why? Its enclosure is too large!

Your first post in this thread FINALLY had T/S Parameters! And the VAS is 69L with a .25 QTS, and you built an 85L enclosure. If you do not understand why this is wrong you will need to educate yourself before trying again. And I do not recommend using the subwoofer in its current state at any volume that causes 'fart noises'. Otherwise you won't have drivers to build a new box for!

That driver was custom designed for a small enclosure. And to your advantage, the baffle width port makes the fabrication much easier than creating those ports you created. They are very nice! That box is definitely worth keeping, just get a driver designed for that size enclosure!

 

[toffkanda]

Warrior thanks for admitting me into your educational Academy. Now I know that I should look at the Vas together with the Qts before making a volume decision. Can I ask a question?. Is my shift from the optimum volume really that bad? given that in this thread http://www.hometheatershack.com/forums/ported-subwoofer-build-projects/17798-shiva-x-extended-bass-shelf-2.html, a volume of 350L was used for a driver of 97L Vas and Qts 0.39,can't I be excused on account of an EBS design? http://www.diysubwoofers.org/prt/ported5.htm. Please kindly explain the parameter relationships in arriving at a box size.

 

[TheWarrior]

You're welcome!

Well, if you are hearing fart noises, I'd say it's bad! There is no fix other than a correctly sized enclosure, sorry!

As for your example, you are comparing two different drivers. Study what Qts and Vas are, because you would realize how silly it is to compare a driver of .25 Qts to one of .39! Those are two completely different animals!

Study, and try again!

 

[toffkanda]

Another thing is, how come you are assuring me that I will destroy my drivers presumably by overexcursion when WinISD gives a a safe margin for my box volume, 600 watt design limit and 2nd order 12.5Hz highpass?

Warrior,
This 'study and try again' thing is really fatiguing. Do you know that the recommended box volume for this driver by T/S parameters is somewhere between 14 and 17 litres? Come on, a student needs study notes, references etc. You make threads short with this sort of answers.

 

[toffkanda]

Warrior thanks for your help. I have found my answer. It is true that low Qts speakers when subjected to conditions approaching an infinite Baffle situation (oversized boxes) are apt to reach their Xmax sooner. They are however still being used for IB builds http://www.diyaudio.com/forums/full-range/186571-qts-openbaffle-how-low-can-you-go.html. I have also found evidence that WinISD can predict the overexcursion resulting from such situations http://www.hometheatershack.com/for...what-ib-infinite-baffle-subwoofer-system.html. So if my Subwoofers were in danger of such destruction, WinISD would know it.( please look at the excursion simulation in my last post). I have even simulated my Subwoofers with 8 times the volume at 600 watts and am still unable to go beyond the highpass restricted point of excursion. It was only with irresponsible parametric equalization at 20hz that I was able to simulate overexcursion. Farting was a wrong choice of words to describe the distortion I heard but I am more than ever convinced that I have made a reasonably good sub. Thanks again.