Yes I made hole yesterday, put table up against it so wasn't accessible, put temp grate over top. And still someone tried to put their foot through it last night when had a few mates over for a gtg. Doh! Another day and I would have had the bracing in at top to save it.
What a fool that guy must be.
Great forum from what i have seen of it so far. Your DIY project is coming a long very nicely now Norpus
Hey Norpus, looks awesome. I was eyeing off a ducted cooling air intake vent as a possible IB manifold cover as these are very solid but also very open, and should be able to be had in a number of sizes or could be cut to size. I'm talking about the steel ones which are about 1cm thick and has ~1cm square grid.
I thought you would have posted an update of the new IB setup Mr Norpus.
Then again from our phone conversation this afternoon you probably can’t get the smile off you dial long enough to type anything. ;D
Hehe yes why waste time on the confuser when there are dual IB subs in perfect phase in harman alignment to listen to.....
Some serious testing was done today with the help of SGRaudio who kindly provided 2 x 500w AB class sub amps for the first audition of this new combo. My sincere thanks to Stuart and Harry Ralston of SGR whose acoustic expertise and troubleshooting was invaluable this afternoon over 5 hours.
Firstly, the levels were checked and the behringer crossover between the mains( B&W802D) and front sub was adjusted from 44Hz back to 60Hz on the CX2310 and level matched. The mains were also centred, toed in and positioned correctly to image the stereo signal dead centre ( a few inches made a difference)
2ndly, the phase was adjusted by Stuart - it ended up being around ~45degrees, despite the physical distance of the front lip of the floor mounted manifold being only 12 inches behind the mains front baffle
The 500watt mono sub, running 2 ohms (2 drivers x 4 ohms in parallel) certainly had superior grunt than the Behringer A500 (labelled 230w x 2 in 4ohms). The oscilloscope readings from the HT tracks later got up to 400watts rms according to Stuart - no hint of amp clipping where the behringer would have clipped many dB lower for sure.
Once we were happy with the IB integration in 2ch, we hooked up the 2nd 500watt amp to the rear 2x15D8 Tempest IB. I was a bit concerned that this amp might be too much for these drivers (the Ava's loved the extra headroom). Sure enough, a 15Hz rumble filter was required to keep them from bottoming in the Master and Commander testing. The levels were matched individually at the 60Hz crossover (with front IB disconnected) and then both were integrated together with an appropriate level reset.
Phase on the 2nd IB we weren't sure what it might be. So we tried in phase (treating it as one big box just with 2 separated driver sets) and 180 out of phase due to proximity of back wall. I moved the spl meter across the room with warble tones playing and found the reponse was flatter when they were in phase. There was a null around the listening position (middle of room) when they were out of phase - ~ 6dB down. So that was easy - in phase it is
Testing - 2channel The dual IBs in Harman alignment were seamless - the bass control was truely smooth and simple. Even Harry who is not an IB fan, I thought was making positive body language signals. We also started to smile secretly - mmm we may be onto something here. Some favourite tracks were played and yes the bass was authoritative and rather sensual. Peaks on the oscillioscope still only suggested around 100watts rms being used, despite sonic levels being well above 100dB and normal listening. Big smile.
Testing - DTS
WOW is all I can say. As have all my guests today said. My centre channel has done the dance off the crtTV and crashed onto the floor with the vibrations. Never did that with the A500! Fortunately no damage as it fell on the blanket which had been covering the reflective crt screen. Oops
The sensuality of the timber floor undulating with VLF was sensational - yes twice as good as before with one IB. The sensation was just enveloping. With 2 x 500watts of sub 60Hz grunt now available with capacitance and toroidals to keep up the feed, the U571 depthcharge scenes were damn scary. The krunches were reality. F#k being a submariner no thanks! The tempests I'll have to be careful with in these scenes as they did bottom without the rumble filter. don't want to break them, so will be careful once this testing completed.
Final testing 2ch - 1 sub vs 2 sub in Harman alignment Stuart put on a track where a T-Rex comes from afar (5Hz) and when close devours something. With front and rear subs, the immersion was so much more. Harry commented we felt like we were inside the gut of the T-Rex with 2 whereas reverting back to the big front IB, the envelopment was lost and the image was mainly from the front again. Proof enough for us. BIG smiles all round, we cracked it! ;D ;D ;D
Oops, had a visit from the local EPA rep yesterday It appears my sub testing recently on U571 doesn't go down well with a neighbour. I can guess which one, but to be fair I wasn't really being considerate of them the last coupla days. Evidently it was making things shake in their house. Oops
I reckon the 2nd IB and the extra power must be making a big difference - noone has ever complained before. Oh well, funs over and I guess I don't have to stress test the toys anymore. My house will last longer too
Minimum 7mtrs away plus high fence plus brick wall I have done spl meter checks this week and the spl levels are not high at all at my boundary when A weighted (as the EPA would do). Usually well less than 70dB - but A weighting rolls off heaps below 100Hz which is fortunate.
I guess if stuff is audible or rattling in their habitable room that is against the local rules. Only would really happen at test levels, but thats what I was doing last week - too much fun (these people are the type who'd go to the EPA before they'd talk to their neighbour about an issue, despite the EPA advice to the contrary. pity)
Low frequencies carry extremely well. It's why large things have deep voices. Elephants can communicate across great distances silently using infrasonics. The female herd leaders are supposed to able to talk to each other at up to 8 kilometers. Nobody knew this until recently because nobody had ever heard it. I bet it made the windows rattle in the tourist Land Rovers! ;D
Bass also has a nasty habit of finding resonant chambers which amplify its effects. Modern lightweight building construction favours resonance at unpopular frequencies as far as big subs are concerned. Lots of badly-damped sounding boards and open plan living rooms with suitable dimensions!
The loudest bass in my garden (when a sub is playing) is in my closed wooden workshop 10 metres from the house. At 7 x 3 metres the shed looks innocent until you go in there with music playing indoors. The house windows are never opened when the system is operating but the bass still carries. It is actually very unpleasant and feels rather as if one's chest is being beaten with a pillow. I only went over for a screwdriver and was shocked at the bass levels in there. I also managed to make my wife's seed trays rattle in the greenhouse with the SVS!
I'd try making friends with your neighbours and suss out what is acceptable. Just don't brag about the huge loudspeakers you have indoors or they'll think you are a hooligan! ;D