'Perceive v2.0' Construction Diary

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Schiiit!

This thing has got to be the daftest thing I've ever owned...

The day started out with me testing the sub indoors but it was just sooo nice outside that I picked up the laptop and decided to go measure and have a few brews in the sun. I also snuck in a spray session whilst the going was good, this sub is definitely a keeper.

Talk about nice weather for September in the UK:

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What can I say about the sound?

From running indoors: It digs deep, really deep and loud too. Running a 12hz cycle at triple figures is just sick, I can see the blinds flapping around, feel the floor pulsing and that 'orrible sense of pressure in the air, yet I can't hear a thing. From the few 'bass moments' I choose from showcase films this sub provokes a sense a profound fear when running 6dB hotter than reference level - definitely sweet 🙂

Port noise isn't a problem, the drivers bottom before I can get it to make nasty noises.

Sounds really good with music but the B&C is slightly tighter at lower volumes but thats about the only thing it does better and what the B&C doesn't do is sound anything like as clean at high SPL's and it can only dream of churning out the depths this does.

I'm trying to think of something negative to say... its early days so I'll post back if I find anything.

I've got a good few winMLS/Arta measurements but I need to transfer them across from the laptop and TBH after playing around all day(hey, its hardwork 😀) I'm fooked. Will get them up tommorow.

But I'll say the highlight of the measurements had to be running 105dB @ 15hz with just a tad less than 10% THD and this was outside with the mic at 2m from the port! The XLS is a funny old driver, one minute the distortion is really low but raise the dB a notch a two and it goes through the roof, luckily this happens to be at insane SPL's that you wouldn't want to use anyway but given the above example, if you raise it to just 108dB @15hz then THD jumps to over 35% from 10% at 105dB, remember that those figures where taken outside at a distance of 2 😉. Its a curious trait that I haven't seen before whilst testing, all the drivers I've had tend to show progressively more distortion thats fairly linear with SPL.

I may redo the meaurements whilst running sealed to check this behaviour as I was wondering if it was port noise but I can't hear the usual nasties so I doubt it.

Anyway here's the pics:

Shot of port detail showing the use of PVC pipe that I heated and bent into shape to smooth the airflow through the port turns:
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First few coats of primer applied to driver enclosure:
An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
ShinOBIWAN said:



Sounds really good with music but the B&C is slightly tighter at lower volumes but thats about the only thing it does better and what the B&C doesn't do is sound anything like as clean at high SPL's and it can only dream of churning out the depths this does.

I'd certainly trade a bit of "tightness" for another octave! 😉

Still though.. not an apples to apples comparison The B&C was only one driver in a fairly small volume. :bawling: 😀

Instead of the special effects and synth music - try something with low level low freq. hall sound. Doesn't have to be classical, just something to judge the effect with soundstage "expansion". I think you'll have a rather wide grin on your face when you hear what that extra octave will do for music. 😉
 
jleaman said:
What are you powering it with.

UcD700 with each pair of drivers wired in parallel and then the two pairs wired in series.

The UcD is probably just about right as I seem to be excursion limited, there is a hefty 2000VA toroid helping to keep huge amounts of current on tap though.

Actually it maywell be the amp clipping when I mentioned the problems with distortion varying massively between just 2-3dB. If the weather is nice over the weekend I plan to measure the sub again but sealed this time. I'm not really complaining about the output or distortion because I'll likely never run it at those high SPL's but it would be nice to know if this is a driver trait, a box/design problem or the amp itself.
 
richie00boy said:
Can't see any pics - are you using a free host? What did the box get tuned to in the end?

I designed around a 14hz tune but I ended up taking out 12cm off the port because you nearly always end up with a lower than predicted tuning frequency. Final and measured tune is just below 14hz.

Monthly bandwidth exceeded on my image host, so that's why the pictures aren't showing.
 
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