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Old 17th July 2010, 02:44 PM   #1
lazyfly is offline lazyfly  Australia
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Default Alpair 7 SPL's

Hi folks,

Can anyone tell me why my Alpairs seem to 'cut out' for what I'm guessing are milliseconds when I start to give them a bit of willy. Not a lot of willy, I'm well aware that they're a small full ranger and are treated as such.

It happens about 12 o'clock with a 29dB gain 34watt PP EL34 amp and one of Nelson's buffer's with 0dB of gain. ALso with a Tripath amp which at the time I assumed was the amp clipping but the EL34 certainly isn't so I'm guessing the Tripath wasn't either. It's happened in both the Brynn cabinet and on OB with a high pass of around 120Hz at the time.

It's not a mechanical xmax limiting sound, but more that they just momentarily go extremely quiet for, as I said, a millisecond then resume, turn them down and they are okay. Now to reiterate, they are not played loudly as such. For example, I believe the FE127e's play a little louder, with less bass in the Brynn of course, but theirs is a mechanical breakup and very obvious. It doesn't explain why it happens with a HP filter either. The CSS FR125 clap out sooner, but again like the FE, it's a mechanical break up. And yes, both of these are larger drivers, but the FE for example, has far less excursion (though greater than published).

I'm not so concerned about it's SPL's, but what it's actually doing as I've never heard this in a driver before.

Any suggestions? Is this intentional? Is 120Hz too low a HP (2nd order)?

Cheers fellas. Have a lovely weekend

*edit: bit more info and clarification.

Last edited by lazyfly; 17th July 2010 at 02:51 PM.
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Old 18th July 2010, 07:53 AM   #2
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Hi laz,
Quite an intriguing situation. The Alpair 7's are sensitive to all inputs, hence their wide emittance range. They wouldn't "cut out" by themselves. Given the relative low mass of the Alp7' power-train and their decent excursion, there's nothing to hold these drivers back from converting and emitting a signal.

I suspect something in your set-up is changing the signal to the drivers. I think they're going "quiet" because for a moment, they're not getting anything much to play.

To be frank, I've never yet heard any low-mass full range driver creating an acoustic omission in the way you describe; But I rarely use any sort of filtering so maybe others can expand on this intriguing situation.

Cheers

Mark.

Last edited by markaudio; 18th July 2010 at 07:57 AM. Reason: typo mending
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Old 18th July 2010, 08:22 AM   #3
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Hi Laz,
Sorry, I forgot to ask if you'd tried running the Alps without the filter?
Cheers

Mark.
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Old 18th July 2010, 11:40 AM   #4
lazyfly is offline lazyfly  Australia
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Hi Mark,

Thanks for replying to my questions.

The drivers run without the filter in the Brynn cabinets, apologies for not making that clearer. The thing is that I haven't actually pushed them farther to see if perhaps they are just very close to their xmax and this is a precursor to it.

I've put a HP filter back on them, and further up, to about 200Hz and they certainly can be pushed along further up the volume control, I got to 3-ish o'clock and without the bass they were fine, hence my precursor comment above.

On another note, I loved your story re: hooter. We had a similar situation with a cockatiel who was caged up on the kitchen floor with a pair of budgerigars, dogs and cats walking and stalking them all day. This was in the home of a family whose daughter was studying to be a veterinary nurse!

Good job saving the little fella, I bet he was worth the effort. Happy endings like that are few and far between
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Old 18th July 2010, 12:39 PM   #5
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Hi Laz,
Check out the max. playing excursion. Ideally should be no more than about 3 to 4-mm on heavier peak loads (big roll of a drum or anything that generates large LF). The cone Dia is only 70-mm so there re limits. That's 1 thought. Wondering if the driver are being caught out by the odd LF heavy load (even allowing for filter)???

Yup, glad you like Hoots. We also rescued Sisso (abandoned on the Wan Chai streets) and Ronnie, given up to be killed off at our local vet. She hadn't got the heart to ring the final curtain for this little mite. We're life members of the SPCA, (RSPCA).

Cheers

Mark.
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