Still... H2 is 60 dB down, H3 even more...
And very benign breakup at HF, very smooth response. Good stuff!
And very benign breakup at HF, very smooth response. Good stuff!
You mean a full range driver?
They are probably already approaching the limit to how high-powered they can get.
As an easy to visualise reality check: a candle flame puts out about 80 watts of heat. Imagine holding the magnet of a typical 2.5" driver over a candle flame. It would quickly get hot enough to scorch all the moving parts.
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This Fountek driver is rated at 15watts.
Boutique Haut-parleurs & Audio DIY
The voice coil is 20mm, the magnet is 40mm.
The standard way to dissipate more power would be to make those components bigger.
The Peerless NE85 does exactly this: it has a larger (25mm) voice coil, and is thus rated for a mighty 20watts. That's probably about as good as it gets.
In the wacky world of DIY, you could try using computer cooling hardware (heat pipes, a CPU fan or whatever) to wick heat away from the motor, and you might get more power handling from a small driver.
There are papers and patents for this idea going back about 40 years.
AES E-Library >> Heat Pipe Cooling Enables Loudspeaker to Handle Higher Power
As far as I know, the idea has never been used in a commercial system.
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The problem is that a driver is close to a 2nd order thermal model ("slow" magnet, "fast" coil), and doing this would only decrease the magnet thermal resistance, ie not adress the voice coil power compression., which I think is the most relevant one in our application.
No, not a full range, just an mid/upper mid. I would still want to use a tweeter above, and a "low-mid" below, in a 4-way config.
For example:
T - 1600 Hz up (or so, give or take)
UM - 1000-1600
LM - 300-1000 (maybe as low as 800 Hz)
W - 300 Hz below
With a UM at around 2.5" and with a fairly small flange, this would allow a reasonable amount of flexibility to achieve a 1/4 wl c-c at crossover frequency, which is what I like to aim for.
I can think of a few non-exotic ways to minimax power handling vs driver spacing:
1) Use a single driver for 300-1600, rather than splitting this between two small drivers.
2) Use an oversize (more than 2.5") driver, but hack your units to allow closer C-to-C distance (like the attached pic).
3) use a driver that has the biggest voice coil + magnet that can be squeezed into a given frame.
e.g. the Peerless NE85W-04 is a 2.5" mini speaker. It has a 25mm voice coil in a 85mm frame.
A dome mid like the Morel MDM55 gets a 54mm voice coil into a 85mm frame.
1) Use a single driver for 300-1600, rather than splitting this between two small drivers.
2) Use an oversize (more than 2.5") driver, but hack your units to allow closer C-to-C distance (like the attached pic).
3) use a driver that has the biggest voice coil + magnet that can be squeezed into a given frame.
e.g. the Peerless NE85W-04 is a 2.5" mini speaker. It has a 25mm voice coil in a 85mm frame.
A dome mid like the Morel MDM55 gets a 54mm voice coil into a 85mm frame.
Attachments
Again, 1/4 wl c-c at crossover. And some tweeters are quite capable of this, at reasonable living room SPLs.
Many drivers that are small enough to go up tight at 1600 don't have good distortion performance at 300 Hz.
I suppose but there are plenty that do. I am certainly not a less is more kinda guy as I run a 4 way myself, but finding a driver that plays nicely from 300 to 1600 shouldnt be too hard. On my 4-way, I am actually running a driver from 250 to 2800. I arrived there because of an issue I needed to address, but this is a far cry from 300 to 1600.
Notably a small upper midrange driver (around 2.5 inches in diameter) doesn't start into pressure losses off-axis until very near 6 kHz.
-practically speaking then you've got the distance from the tweeter's surround to the midrange's surround.
Assuming you "route-in" some of the tweeter's *faceplate and put it as close as possible to the midrange - then you should have enough to meet your 1/4 objective substantively higher in freq. than 1600 Hz.
*I'm also assuming the upper midrange driver's faceplate is small, if not (and if possible) it would also need "routing-in" to push the two driver as close as possible to each other.
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For discussion purposes, an NE85W right next to an NE19VTS, flanges directly touching, gives 0.32 wl c-c at 1600 Hz.
In the distant past, 40 years ago, the Japanese company Sony released the APM (Acurate Pistonic Motion) loudspeaker series, using technologies that many considered the technologies of the future. Having measured the tweeter of the Sony APM-33 speakers, let's go back from today's future to the past to see if they were really that cool.
Sony APM-33W - SONY APM-33Wの仕様 ソニー
Sony APM-33 tweeter | HiFiCompass
Sony APM-33 woofer | HiFiCompass
Sony APM-33W - SONY APM-33Wの仕様 ソニー
Sony APM-33 tweeter | HiFiCompass
Sony APM-33 woofer | HiFiCompass
My brother owned some of these about 30 years ago. Interesting looking but sounded like crap. Pisstonic motion🙂
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This isn't what determines the vertical off axis interference patterns though. That's the c2c separation between the two drivers. At least on average.
To be fair the top of the range woofer used 4 voice coils which makes (a little) more sense.
Sony APM-8 on thevintageknob.org