[Toffkanda]

This is a build critique thread by someone who feels he must have a horn.
Before you read please note ;
1. This is one of those jobs by people who have messed around with Hornresp for some weeks and feel they know enough to design and build their own rather than picking any of the available proven tapped horn designs on the forums for sure results.
2. The builder has insisted on forcing the driver available to him to fit a tapped horn rather than working with proven drivers for acknowledged tapped horn Subwoofer performance.
3. The builder working with mostly scrap plywood and no prepared cutlist or pre-cut panels, built as measurements dictated, cutting one panel after fixing the previous, fumbling away blissfully.
4. The builder has no plans or wherewithal for now for acoustic measurements on completion but hopes to rely on listening sessions until such a time as he is able to to acquire or have access to the relevant equipment and know how.
If these sins can be forgiven, then here we go.
First the sims as they seemed ok to me.

 

[Toffkanda]

The driver is a 12 inch Epik sentinel, a heavy strong motored driver with the attached t/s parameters.
The goal is 16-17hz Fc and about 3 times the SPL of that driver in a bass reflex cab, enough to fill my big room (4500cuft) since I don't have enough drivers. The horn is really tall with a very small footprint,should be unobtrusive in a room corner. Success with this should generate a twin.

 

[Toffkanda]

Ah yes., the driver t/s parameters....

 

[theJman]

Your first post cracked me up! It almost sounded like a guy talking about his wife to his friends... "sorry fellas, but I have to wear this shirt and go to her families house instead of heading to the bar with you and watching the game".

 

[Toffkanda]

My wife is fortunate that I have nothing to hide from her except of course the occasional purchase of fairly expensive(by our currency standards) sub driver or audio equipment (which I confess to much later) so it comes natural for me to lay out my audio sacrilege upfront. Seriously I'm yet to come across any other DIY Sub audiophile in my locality and it is such an uphill task accessing the things/materials/skills available to you guys over there in the US. I try to to scratch my itch with whatever is available to me that can work. The build is not finished yet but I think I honestly came very close to what was simulated (assuming nothing is fatally wrong with the simulation).

 

[Toffkanda]

A little background ;
looking at the t/s parameters it occurred to me that it might be suitable in a tapped horn because of a low Qts, low Vas, high BL and strong aluminum cone. Using Little Mike's BL^2/Re/Sd assessment it yields 0.27 which is just outside his comfort zone (0.13-0.25).
In a bass reflex cab it wants a small volume for true 20hz performance and from the Hornresp simulation, it seems to be no different in a tapped horn. Indeed by simulation it appears to do 20hz and below under a 300 litre volume but of course other parameters including SPL may not be worthwhile over a ported box.
Also the sentinel is known for palpable room pressurisation and it appears to correspond with the relatively high throat pressure which I assume is a testimony to the powerful motor. It does desire a really high compression ratio but one has to resist this in modelling, hence a final ratio of 3.75:1.
I have not tested but I'm convinced by DIY Speaker guy's argument about the FR differences of large voice coil/high inductance motors and I see that it applies to this driver. So in modelling I ticked the large voice coil option under loudspeaker wizard to get a modified FR.
There also appears to be some benefit in applying the filling/stuffing option to the 1st segment, it seems to lower the 60-100hz spikes.
I'm therefore expecting reasonable SPL at 2pi ([email protected]), percussive room bass pressures, useable extension down to 14hz and quick agile LF Impulse.

 

[Toffkanda]

Just finished the cabinet. I'm 6ft 2". Add an inch for my sandals.
I hope to be as tall as this cabinet as I grow up :grin2:.
I'll be coupling it shortly. There's the horn mouth at the bottom and the driver access window above it which is to be covered with perspex for visibility of the driver.

 

[theJman]

Man, you don't mess around; no sooner do you make this thread then the cabinet is built. Well done...

 

[Toffkanda]

Thanks Jim.
I have to figure out how to skirt the edges of the driver window perspex where it is sunk to flush with the wood because it's edges looks untidy when bare. I need to come up with a kind of margin frame design to beautify the edges. Whether real (aluminum, wood or plastic) or virtual (tape, paint or veneer),I'm wondering what looks best:scratch:

 

[Toffkanda]

I briefly tested the horn using just a 30watt old amp with volume dial halfway and test tones 10-20hz and it was very pleasing to me. Almost too loud for the environment it was kept. I look forward to playing it with a 600 watt amp soon.
The test tones shook a lot of things but also showed up a leak at the speaker terminals and added noises from the perspex driver window vibration. It is obvious I need to brace the perspex horizontally from within using a removable brace.

 

[theJman]

Output=great, WAF=not so much...

That thing is probably going to dislodge your fillings, but I'm sure it will be a lot of fun to play with. :hsd:

 

[Toffkanda]

So right Jim. The Wild Horn has been sitting in my office all this while. Eventually I'll have to introduce it to my wife. It was built with my new home in mind but that house is still fairly far from completion. I don't even have storage space for it in my present home but I had to build it now because the urge was strong.

 

[Toffkanda]

People of the forum, I present the Wild Horn ;

 

[theJman]

Built in record time I might add! Were you able to fix the rattles and air leak?

 

[Toffkanda]

I'm on it as we speak.

 

[Toffkanda]

I have had to uninstall the perspex plate remove the compact foam gasket which I feel may be providing vibration clearance on the screws, replacing it with a putty-like non-setting material (flash band). The brace is a 3/4 thick piece set to put pressure horizontally on the perspex without causing a gap in its seating. The brace is bound to the perspex with a water based glue while being held snugly at the sides glue-free with a single screw on each side. The brace is black and when dry, the glue is expected to be close to transparent, otherwise it will be covered on the perspex with black tape. I hope that the 3 inch wide brace being mounted at S3 right across from the driver perpendicular to the air path will not cause turbulence noise (my max airspeed at horn mouth is probably under 13m/s though.
What can I say? This is secondary intention work and far from ideal. The perspex sounds better on tapping it but testing will tell. On hindsight this brace should be part of any fresh design utilizing 5mm perspex wider than 8 inches.
The connector terminal leakage merely required spreading thick glue around the inner parts of the terminal communicating with the outside.

 

[theJman]

I'd rather have that then a rattle. Some constant vibration sound would be like water-boarding for me.

 

[Toffkanda]

Jim, everyone else ;I am happy to report that there's indeed a wild horn in Africa,
My goodness! I'm only taking a 30watt amp to the limit and I've discovered how many things are loose and can shake in that room, certainly none from the cabinet itself.
Like the scientist tinkering with coarse tools on his crude Frankenstein project, I'm tempted to shout "it's alive!".
Playing a 10-19hz mp3 tone clip, the sensation of my head submerged under water was intense. I felt like trying to pop my ears as you would in an ascending jetplane. For other tones I could feel my trouser sleeves fluttering as well as seeing the same on the window curtains across the room. I really feel gratified. Now I can justify the size of this behemoth to myself. :grin2:
Next is to find a suitable 600 watt amp and dsp.

 

[theJman]

Next is to find a suitable 600 watt amp and dsp.

Along with something to shore up your walls?

 

[Toffkanda]

Haha. My office walls are lucky the Wild Horn won't stay there for long. I have to add more concrete work to my new house under construction though.
Finally came across behringer dcx 2496 new but it sells for a currency equivalent of 250-300 dollars. Over here that's a lot to invest in a hobby at the moment. Hope I can get it before the currency slides again.
Most amps here are low grade Chinese but I'll keep looking.
Avrs are not popular here and fairly used ones come without the remote controller making it difficult to reconfigure them.