HiWave HiBM65C20F 3-1/2" BMR Wide Range Driver Measurements and Impressions - Page 2 - diyAudio
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Old 8th December 2012, 05:18 AM   #11
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Originally Posted by ra7 View Post
Might be a reflection of the driver surround or the pipe edge.
The dip could be the driver surround, but probably not the enclosure as the manufacturer's spec sheet shows a dip there.

As I'm listening, I'm finding these need a lot of power to open up.
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Old 8th December 2012, 05:40 AM   #12
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No, that dip is a phase issue due to a sort of mechanical crossover I'm guessing.
It must be some sort of transition from piston behavior to oscillatory behavior.
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Old 8th December 2012, 05:41 AM   #13
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Id like to see the distortion measurements Ben, if ya could? Pretty please
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Old 8th December 2012, 11:33 AM   #14
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Originally Posted by Melo theory View Post
No, that dip is a phase issue due to a sort of mechanical crossover I'm guessing.
It must be some sort of transition from piston behavior to oscillatory behavior.
(Very) roughly calculating from the manufacturer's data, it's in the ballpark for transition frequency, and also possible reflections from the front roll-surround.

Not sure I like the 20% +/- Fs variation, since that could put a pair of drivers at anything up to 34.4Hz apart in resonant frequency, although given the price, can't really complain.
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Old 8th December 2012, 04:01 PM   #15
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Originally Posted by Ben_Tech View Post
The dip could be the driver surround, but probably not the enclosure as the manufacturer's spec sheet shows a dip there.

As I'm listening, I'm finding these need a lot of power to open up.
At 81dB/W/m, I would think so!

But still, it's something to ponder for a cheap, effective surround speaker. I'm thinking a composite decking post with one of these on top, and maybe four Aura NS3's (unless there's a longer-throw 3"-4" driver of which I'm unaware) in series-parallel on the floor.
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Old 8th December 2012, 09:37 PM   #16
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Originally Posted by Melo theory View Post
Id like to see the distortion measurements Ben, if ya could? Pretty please
Here's a THD measurement at 1K. Let me know soon if you want to see any other frequencies. Note that everything below 1K is just the high room noise floor.

Click the image to open in full size.
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Old 10th December 2012, 11:00 PM   #17
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I listened to a few TV shows on the HiWave center channel today and found that, even with the center set to +8 dB in the receiver, the dialog was low compared to the music emitting from my reference speakers. I upped it to the max (+10 dB) and will try again.

The intelligibility was good, just not loud enough relative to the mains (which are not particularly efficient mind you). Sounded recessed, for lack of a better word.

I'm sure a line array of the BMR's would fix that but I only bought three, not the required four for a series/parallel wiring scheme. No big deal, will see how it goes.

Also, if the BMR was used (even in singles) for the front three, that would probably work as well as then all three would have the same power requirements.

Even though it only takes an hour apiece to build these in temporary form I'm debating if it is worth further experimentation or not.

Regardless, it has to be one of the best $10 speakers out there.
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Old 11th December 2012, 04:33 AM   #18
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How about this.....
Do a 1.5 way.
Wire 2 in series for a N impedance of 16 ohms, then put a cap on them where they fall in frequency.
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Old 12th December 2012, 01:06 PM   #19
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Another project with these cool little drivers.

BillFitzmaurice.info - View topic - SLA BMR drivers
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Old 28th December 2012, 08:58 PM   #20
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I bought a pair of these as well, I couldn't resist.
The dips are audible with a swept sine but not with music IMO.
The way I understand it, the biggest dip at 1.8k as well as the stepped response in the upper end is a result of the bending mode radiator technology. I can't remember where but I read about them not too long ago in a book. I think the technology trades an even response for wide dispersion and can provide decent LF if designed for it. I'll see if I can find the info.

-Matt
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