Experiments with M2 horns.

[natehansen66]

Nice work! I do outdoor measurements myself and I can appreciate what a pain in the rear it is. I drag my amps and stuff outside so that's a bit easier than running cables everywhere. To make sure I understand your setup: speaker and mic at 40" off the ground with the mic at 2m (78.74")? Is that 40" the location of the cd exit? That would only give you about 2.5ms of clean impulse for the wg and a bit less for the woofer since it's closer to the ground.....it definitely looks to me like you've got some reflections in your data.

Hopefully I just misunderstood your setup and I'm not the guy raining on your parade . I generally try to keep the mic distance equal to the distance to the ground to maximize the time with no reflections. A 40" mic distance should get about 3.6ms of clean data which is about what I can get in my living room.

Another method for eq'ing a cd horn is to cut the midrange frequencies where you see gain from the device, rather than boosting hf. In the digital realm it's all the same, but you could probably get away with a little less digital attenuation on the tweeter channel if it's needed.

[Don C]

The crossover data is copied from the file that 4313B posted earlier in this thread. Here's a graphic, from my system, below.
Regarding the height, I remembered the measurement data wrong. I measured again. I had 48 inches not 40. That was to the base of the horn, so it was 55 inches to the center of the driver. I measured 78 inches to the screen in the throat from the tip of the microphone. It's a Stanley tape, I tend to round off to 39 inches to measure meters. Its a bad old habit I guess. There was grass and weeds in front of the speaker on the ground, I wouldn't expect a sharp reflection. Here's the impulse response that I was seeing, you can see the little glitch I saw that made me decide to set the gate at 4.2
The measurement is saved, so I can re-plot the data at any gate time I like.

[Aaron]

For my system, I had to set my limiter thresholds to zero to avoid compression, how about you?

[Don C]

I'm not noticing any compression, but I'd love to bypass those limiters anyway.

[natehansen66]

The crossover data is copied from the file that 4313B posted earlier in this thread. Here's a graphic, from my system, below.
Regarding the height, I remembered the measurement data wrong. I measured again. I had 48 inches not 40. That was to the base of the horn, so it was 55 inches to the center of the driver. I measured 78 inches to the screen in the throat from the tip of the microphone. It's a Stanley tape, I tend to round off to 39 inches to measure meters. Its a bad old habit I guess. There was grass and weeds in front of the speaker on the ground, I wouldn't expect a sharp reflection. Here's the impulse response that I was seeing, you can see the little glitch I saw that made me decide to set the gate at 4.2
The measurement is saved, so I can re-plot the data at any gate time I like.

Ok, that makes more sense.

[Aaron]

Don, could you give your best guess as to the size of the heat sinks you put in your BLU box?

[Don C]

25mm square.

[srm51555]

Hi Don,

Any updates on your project.

Thanks,
Scott

[Don C]

They sound great with the horns just sitting there on the PS1400s, so my motivation to build the bigger cabinets is weak. I'm busy with other things. I'm playing them almost every day though. For those who are disappointed that they can't obtain the D2 drivers, these 2452s with the coated diaphragms sound pretty amazing to me. The 2452s were still shown as available at Speaker Exchange for less than 400 brand new in the box, last time I looked. Add 179 each to replace the diaphragms with the aquaplas coated ones and you are in business. OK it's still not really cheap, but this stuff was far more expensive just a couple of years ago, and who knows how long the fire sale will last.

[sebackman]

Don,

Turn the limiter to +20 db and they are automatically turned off.

By the way, JBL states 36db LR filters and in our BLU units there are only NTM36. Does anyone know how close that is to LR36?


Kind regards
//RoB

[pos]

They are probably building the LR 36db/oct by chaining two Butt 18dB/oct

[Don C]

All I know is what BSS tells us. It sounds like they make it from two filters in series, but with slightly different frequencies.
LINK

[Don C]

I'm trying to visualize M2 components in a 4365 sized box here.


Edit: Getting fussy with the drawing.

[zeljkor]

http://sound.whsites.net/articles/ntm-xover.htm

All I know is what BSS tells us. It sounds like they make it from two filters in series, but with slightly different frequencies.
LINK

[Don C]

Thanks for that, it's a good article.