HiWave HiBM65C20F 3-1/2" BMR Wide Range Driver Measurements and Impressions - Page 4 - diyAudio
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Old 10th March 2013, 10:12 PM   #31
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Location: Sheffield
Hi Derek, looks like you might've misinterpretted slightly - I'm gonna build a bipole, not a dipole.

The former has all the drivers wired in phase, but two facing backwards. You get force cancellation (as the drivers are moving in opposite directions), so the cabinet won't try to walk around.
Another useful effect of this set-up is that baffle step losses are compensated for: each driver effectively sees an infinite baffle, as the same waves are coming around from the other side of the cabinet.

The cabinet will be sealed for a first attempt.
I might look into the 3.5" Peerless passive radiators at a later time - tuning could be interesting with the ~0.6 Qts of the drivers I've ordered.

Dipole construction will have lots of cancellation: I think even 100Hz would be wildly optimistic.
I might give it a quick try during the construction of the cabinet, but would expect lots of eq would be needed, which would take its toll on battery life.


Last edited by chris661; 10th March 2013 at 10:16 PM.
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Old 25th July 2013, 01:29 PM   #32
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I am pondering doing an MTM with the l.5 inch drivers, however I am wondering if the tweeter is even necessary? Wiring the drivers in parallel would increase the sensitivity to 87 db, correct? I would need a BSC if running full range. Thoughts?
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Old 9th September 2013, 01:32 PM   #33
lithoc is offline lithoc  Malaysia
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Originally Posted by Ben_Tech View Post
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.

I have few questions to ask

Did you test the speaker using only BMR driver for left + center + right ?

How does it loud enough for some action movies ?

BMR driver claims to have lesser "fall off level" compare with conventional cone type driver, do you notice the same? Try listen from far?
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Old 1st August 2015, 05:03 PM   #34
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Just so that others are aware, you can't run these in series. You end up with no treble, not exactly sure why but the NXT side of things doesn't like it.
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Old 1st August 2015, 05:51 PM   #35
sreten is offline sreten  United Kingdom
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Originally Posted by snoopy33 View Post
Just so that others are aware, you can't run these in series. You end up with
no treble, not exactly sure why but the NXT side of things doesn't like it.

AFAIUI the drives have some built in BSC and a dip before they
enter the random break up mode of the flat diaphragm. So in
theory two units will add effectively in the pistonic region but
only at random in the break up region, boosting bass by 3dB.

rgds, sreten.
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Old 1st August 2015, 06:18 PM   #36
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Here's mine. The problem now is to get the NXT's to function I'm down to 1 ohm, which is going to require either a 3-4 ohm resistor (I doubt this will work) or a transformer? to match the bass unit. Ideas?
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Old 1st August 2015, 10:10 PM   #37
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You have various ways to connect those 8 drivers. Your choice (to minimize series connections) is to use only parallel connections so the overall impedance becomes 1 ohm.

If you wish to do your amplifier a favor, you can connect four pairs of drivers in series (hence one series connection per each pair) and yield an overall impedance of 4 ohms when you parallel connect the four pairs. It a tradeoff but life is about trades. You can try it and report how this connection sounds.

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Old 2nd August 2015, 06:54 AM   #38
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Hi Jim, as I was saying earlier, you can't series these without loss of treble. Some mid range clarity is lost as well.

I'm running an Icepower ASX2 50, perhaps it can take the 1 ohm but the spec says 3.

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Old 2nd August 2015, 02:02 PM   #39
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I understood your desire to not have series connections. What I suggested is a way (essentially only a one series connection solution) to trade a little treble/mid for an impedance which is friendly to your amp. As I suggest you can try it and listen whether it would be successful.

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Old 2nd August 2015, 02:12 PM   #40
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That was the plan originally, and two in series (16 ohm) / 4 rows results in hardly any treble.

There's no way around it that I can see, it's 1 ohm or bust.

Even with one, I find the sound quality to be lacking, the driver needs equalisation to get it up to a competing level.
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