Helium - a true micromonitor

[Goa604]

I absolutely admire your knowledge and i understand the use case of monitors, however would a similar but more basy build be possible in not much bigger size? Im in search of a speaker build i would use for fun music at my workplace. We usually play trending music so a basy speaker wouldnt hurt. Any advice if this build could be modified or is there perhaps another build similar to this one i could find? I would limit the size to about 4 liters. Thank you very much in advance.

[scottsehlin]

The Helium could be made a little more bassy by moving to an MTM version (using the 8 ohm ND91, which can be tuned for a little more bass extension). Speakers like the Overnight Sensations or my Lithium project are about 4.5 liters and offer considerably more bass than the Heliums. In 2017 at InDIYana, there was a nanotech challenge that had a size limit of 3 liters. There were several designs that had impressive bass performance. If you search for InDIYana 2017, you can find some descriptions. I entered the Rhodium design, but it includes a Ribbon tweeter and is probably overkill for a "fun work speaker" from a cost perspective.

[Goa604]

Thank you Scott! I will search for InDIYana 2017 and see if there is anything that would suit me better. Any recommendations on which build to look for? I would like it to sound very good, we are kinda tired of cheap bluetooth speakers. Thank you very much.

[andykriech]

I have built the Lithiums and several of the Heliums. Love them both.
I would build the Lithiums again if the size works for you. They are a very good sounding speaker and have good bass if fairly close to the wall.
Andy.

[Dunk_c]

I just replaced the fixed cables with binding posts on my speakers. Can someone recommend a speaker wire gauge? I need about a 2.5m run and I understand that the speaker impedance is low at about 5ohms IIRC.

How about 14 awg?

Thanks

[wogg]

14ga is plenty large, 16 would be fine too.

[Dunk_c]

Thanks, just wasn’t sure about the current demand of low ohm speakers

[MattyTeaks]

Have experimented with a few different iterations of the Heliums previously and loved them for their purpose.
With some modifications on another project, I've got a couple pair of 91-8's looking for work.

Considering giving a go at a Helium TMM design.
Opening up some space with a mini tower setup 2.5 way.

Worth the trouble?

[Dunk_c]

REL T Zero integrated with HMM in my work area using REW to set XO and volume, phase and position.
Sub bass On carpet over concrete
Graphs show best integration I could achieve when listening at desk (HMM toed in on desktop, sub under desk in corner) and when listening on a couch on opposite side of the room (HMM minimal toe in)

[Matt Clara]

14ga is plenty large, 16 would be fine too.

What happens if you use too fine a gauge? Asking for a friend...

[Jeff F.]

What happens if you use too fine a gauge? Asking for a friend...

Heat, and before that maybe less bass response at mid to high listening levels.

[wogg]

What happens if you use too fine a gauge? Asking for a friend...

What Jeff said...

Basically, too small a gauge is effectively adding a small resistor in series with your speakers. Heat wouldn't be a concern unless you're running crazy high wattage, but you could simulate the effect in Xsim if you want.

Use an online wire resistance calculator like this one. Add the resistance as a series element before your crossover in Xsim. for example, a 50 foot run of 18 gauge is 0.3192 ohms each way, so add 0.638 ohms. That will affect frequency response a bit based on impedance, if you've got a 4 ohm speaker wherever it dips in impedance will have more loss in the wire than areas of high impedance. Larger gauge wire reduces that series resistance and that effect on the output.

Let's say you have a 3 ohm minimum speaker with that 50 foot 18Ga run, you'll make a voltage divider with 3.638 ohms total and 3 ohms for the output = 82.4% of the signal makes it to the speaker. That calculates out to a 1.67dB drop at that frequency. Not huge, but adds up. Swap that 18Ga for 12Ga and your series resistance drops to 0.1588 ohms total. Now you've got 95% of the signal making it to the speaker and a 0.45dB loss.

If you want to get really crazy, determine the capacitance and inductance of the wire as well and model that. Spoiler alert: the capacitance and inductance is almost negligible.

[alandavidhenry]

I'm wanting to build five of these for a HT system but the ND16FA-6 driver isn't in stock anywhere (I'm in the UK and there is a supplier in France but they only have two in stock).

I can get the ND16FA-4 or ND13FA-4.
I have modelled all three tweeters in VirtuixCAD but it's the first time I've used it. I modified the crossover component values to produce a similar plots on the SPL graph but I suspect there is more to it than that to make a great sounding crossover?

Sorry if this is basic to everyone else on here but I'm trying to learn as much as I can whilst I have all this spare time whilst in isolation.

[Chris Roemer]

Well, that's MOST of it...

I'd try the 16FA-4 'cause it's the same dia. (similar radiation pattern PROBably, and same size V.C. - should handle similar power).
I looked at it using Scott's HP XO and it looks like an "almost drop-in". I'd drop the series resistor from 15n to maybe 10n (and you COULD probably omit the 39n parallel resistor - if you wanted). What'd you come up with?

[alandavidhenry]

Here is a comparison of the two. The 4-ohm seems to be more sensitive and handle more power:

	ND16FA-6	ND16FA-4
Impedance:	6 ohms	4 ohms
Power Handling (RMS):	10 Watts	30 Watts
Frequency Response:	3,500 to 27,000 Hz	4,000 to 20,000 Hz
Sensitivity:	88 dB 2.83V/1m	93 dB 2.83V/1m
Fs:	2125 Hz	2246 Hz
Re:	5.80 ohms	3.17 ohms
Le:	0.04 mH	0.03 mH
Qms:	3.45	3.71
Qes:	6.09	3.46
Qts:	2.20	1.79

On the crossover, I removed the parallel 39 ohm, series from 15 ohm to 22 ohm, capacitor from 2.2uF to 1.8uF and inductor from 220uH to 270uH.

Look very similar to me:

16FA-6



16FA-4