Helium - a true micromonitor

[tomzarbo]

Hi
Just did some crude tesing, thought people might find it interesting. I am no audio engineer.

I built a set of Heliums a while ago and they sounded good to me.
I recently bought a pair of BIC DV32 and these have less base and sound harsh and bright to me, probably because they have low output below 100hz
Play the Heliums with the BICs and I feel that the sound is better. I can now hear more of the high frequencies and still get the bass. For my ears the Heliums are lacking some trebble.
I have some hearing damage and cannot hear much above 8khz.

I used an EMM-6 calibrated mic to do some crude frequency response measurements with REW (please don’t give me grief about axis scaling) the speakers were outside on a stand and the mic was about 2ft in front, pointed at the drivers.

First thing I noticed for the Heliums, good output at low frequencies, even response across the range, but with a dip around 5khz. Did I build the crossovers correctly?

I don’t know if the 5khz dip is contributing to my listening experience, but the BIC DV32 are flat in this region. Perhaps that is why I am more satisfied with the listening experience when I play them together.

Any thoughts?

If I recall, the crossover for the Heliums was pretty high; somewhere around 5k...

That looks like a reverse null when the tweeter is wired reverse of what was spec'd. In other words, you may have the tweeter wired backwards.

TomZ

[Dunk_c]

OK, I will check that out pronto!
When I placed the mic directly in front of the tweeter, the dip was absent.
Thanks

[Wolf]

The tweeter is the typical measurement axis. The polarity is likely just fine.
Wolf

[Dunk_c]

I forgot to say that I put the mic closer, within 6” of the tweeter, not just aligned. Scrappy testing I know!

[scottsehlin]

If I recall correctly, I measured at 0.5 meters (or about 19 inches) at tweeter height, but with the mic pointed at the center of the baffle. Since the dip is right at the crossover point, and I haven't seen it in several measurements that I have done over the years, I would at least double-check the tweeter polarity.

[Dunk_c]

The one speaker I tested did indeed have a reverse wired tweeter, the other was OK. I might redo the sweep and repost results on weekend.
Thanks

[Dunk_c]

Tweeter polarity corrected and retested.

[scottsehlin]

Have you noticed a difference in listening with the tweeter polarity corrected?

[Dunk_c]

Scott, I honestly cannot say. I didn’t do any A/B type testing with the other channel before I rewired. I think this is the only way I could tell. I don’t believe I have much ability to hear subtle differences. I think it is something that needs practice and maybe training.

[stephenmarklay]

I noticed both of the 5w resistors are NLA at parts express. Is there a suitable swap or should I source these elsewhere?

[Chris Roemer]

That, or you could use the 1.8n(ohm) 5w, or a 2.2n 10w, and 47n 10w.
If you're worried about the 2.0n being "off", you could use Dayton's # 004-2.
IMO THAT 2ohmer (in shunt) is not super critical.

[stephenmarklay]

That, or you could use the 1.8n(ohm) 5w, or a 2.2n 10w, and 47n 10w.
If you're worried about the 2.0n being "off", you could use Dayton's # 004-2.
IMO THAT 2ohmer (in shunt) is not super critical.

Thank you sir. From what I have read using the 10w is space constrained but I think others have managed it.

[scottsehlin]

The 10W resistors will be fine. The 5's were nice when available to save a little space. Also, there are a couple of different tweeter resistor combinations that work (14 and 39 ohms or 15 and 47 ohms).

[Scarface1]

Re: Helium - a true micromonitor

Sensitivity is pretty low, as Bryan mentions. They are right around 79 dB. I was targeting about the same power Bryan recommends - around 50W. The good thing about the Heliums is that they can comfortably handle that power.

Hi Scott, I want to build this speaker for a 2.1 setup, but now I have use the nd65 because the subwoofer have a 80.7db SPL. I had to use 2 nd65-8 in parallel because of the missing Xmax.

Now I read the heliums are at 79db, will this work with a sub (w5-1138) with 80.7db. I think so but just for sure to avoid mistakes.

[Chris Roemer]

It doesn't work the way you think it does.
Besides, when you use 2 speakers in parallel, their (combined) sensitivity rises +6dB (which is even WORSE, right?)!