Helium - a true micromonitor

[garychelette]

Is anyone still building these?
Just completed a 4ohm version for my bedroom and still have my 8ohm version for my computer. Still love these guys!

Gary

[Chris Roemer]

I know you'd THINK that a "beta" vers. was farther along than an "alpha"(test), but that's not the case here.
What was known (for quite a few yrs) as the "beta" vers. was (is) a simpler model w/quite a few "missing" graphs, compared to the newer "alpha" (a.k.a. the "Pro") vers.

I've used the Pro (alpha) vers. for many, many yrs, down to a box size of about 0.05cf (ND65s - vented) with NO issues (great results). Also model predicted (very accurately) slot ports. I've been measuring my own T/S parms for a LONG time (WT3, then DATS) AND verifying box tuning. Don't believe I've ever seen a discrepancy of more than a Hertz or 2.

[kennyrayandersen]

To use WinISD "Pro" (I'm using 0.50a7) you don't enter all the parms you can find. with "autocalc" turned on, JUST enter:
Qes, Qms (NOT Qts - it's actually ALWAYS calc'd from Qes & Qms - but then rounded on spec sheets), Fs, Vas(watch your "units"), Re, Le, Pe, Xmax, and Sd(MOST times, when it's given, it's in cm^2, so that's what I use).

I'm probably just stupid, but when I did that, it started calculating crazy numbers. In any case, the newer beta version, you'd think, should work, it just gives me different results than Hornresp, or Vituix (which both agree pretty close. I didn't know if anyone else had seen that, like maybe it was a really small box issue or something. Right now I'm inclined to not use Winisd since it's reportedly less sophisticated and it's also the odd man out (hopefully not like the V-22 flight control computers kind of way (there were 3 on-board computers and if one went bad the other 2 were supposed to over-rule the bad one. 2 of them were installed wrong...)!

[Chris Roemer]

To use WinISD "Pro" (I'm using 0.50a7) you don't enter all the parms you can find. with "autocalc" turned on, JUST enter:
Qes, Qms (NOT Qts - it's actually ALWAYS calc'd from Qes & Qms - but then rounded on spec sheets), Fs, Vas(watch your "units"), Re, Le, Pe, Xmax, and Sd(MOST times, when it's given, it's in cm^2, so that's what I use).

[kennyrayandersen]

And finally some guys were recommending Vituix. I loaded the ND19-4 into the database, and it seemed to agree well with Hornresp. Both say the driver can find joy in a 1 liter or slightly better enclosure (which seems to match Scott's original Parts Express flat-pack size). Since I'm making my own box, I just wanted to check to see whether the smaller box was optimum, or a bit squeezed. Also though you can get just a bit more bass out of it with a 1.2-1.4 liter box [it appears], the smaller box looks pretty good, if the Hornresp and Vituix sims are good. It still leaves me wondering why the Winisd is apparently off by so much?

[kennyrayandersen]

So, a couple guys I read liked Winisd Pro better, but I couldn't even get it to load a single driver, and when I tried to get it to auto-calculate as the help recommended, it gave me utterly nonsensical values for the other parameters. So, that was no beuno.

[kennyrayandersen]

This is the input to the Hornresp that I did: The red line is a 1.4 liter box and the gray line is a 1.2 liter box. Larger box volumes actually do worse (in any case no where near the 3 liter volume that Winisd is suggesting.

[kennyrayandersen]

So, I got around to doing a Hornresp model (Hornresp is more complicated to understand whether you got the inputs right IMO and not really any kind of users guide) and I got very near the original volume, and much lower than what the Winisd was coming up with.

After doing some reading, I understand that some of the equations in Winisp are a bit more simplified, but I wold have thought the box volume would be off by a factor of two. Here is the Winisd input I used:

[Chris Roemer]

You know, T/S parms DO tend to change somewhat over time (due to mfring. alterations). What values are you using for Qts, Fs, and Vas (since 2016 I've been using 0.41, 74, and 0.05cf)? The "initial" parms for this driver were different.
In a .1cf (2.8L) vented box, I think a tuning in the upper 60s (1"x4") looks high. I prefer a 5" tube (Fb in the LOW 60s). F3 (using MY parms) is in the mid 50s. ;-)

- "So, What gives? Is Winisd not good for small boxes? Not good or rather not particularly accurate compared to BassBox 6 Pro? BassBox Pro 6 is saying I can get an F3 of 73 Hz with a box volume of .03 cu ft (51 in cu or .84 liters) which is even SMALLER than the Parts Express project box. So, hep me!"

WinISD works FINE for small boxes.
I believe the main reason PE uses BassBox is that it's not free (like WinISD), AND, THEY are a seller - so they make money on it. I've never found it to be "better" at box sims than WinISD.
You DO know that a woofer in a (tuned) box can have an infinite number of rolloff curves - ANY of which can be "perfect" - depending on what the designer intends to do with it?

- "I'll also attach what the response looks like for configurations with the 3 liter ported box, the other boxes were 2.5 liter for the ND105-PR and 2.8 liters for the dual ND90-PRs. That seemed to be the 'right' volume for each.
I'll try horn response next -- is there something else I should be modeling the box alignment with?"

You can't ALWAYS match a ported box FR using a PR(s). Often you can get very close, but sometimes not.
Do you have something against a 4" long 1" port tube for this project (I'd feel better w/a 1.25"id, 1.5 would be even better)?
I'll do quite a bit to avoid (the expense of) using a PR.
I haven't run all your box sims, but it seems like you know what you're doing.

Another (free) option is a slot port.

Once you get up to 0.10 cf, the TCP115 drivers model well (at a significantly lower co$t), and (IMO) they look much better.

[kennyrayandersen]

So, I'm trying to go through this myself, fer my own edumacation. I don't need to use the parts express box, and in fact prefer to just build my own because it's just easier to get what I want. In any case, I got to thinking that first I would check the box alignment. Parts express lists a volume fir the ND91-4 of .03 ft cubed (I believe they used to list it as .04 ft cubed), but i a really small box that's a lot of round-off; so, I broke out the Winisd and started looking at various box volumes and tuning frequencies.

First, it starts off by giving you a 3 liter volume and a nice curve, but 3 liters is .106 cu ft -- far larger than the one listed by Parts Express, which claims to use BasBox Pro 6. That volume is also larger than the original box used in this thread. OK, so I says to myself -- self, let see how small we can get the box. Long about 2.36 liters, it really starts losing F3. So then I tried using a passive radiator, in fact, I used 2 different passive radiator configurations. The first is with a single ND105-PR, and the second was with dual ND90-PRs. The box volume seems to work about right for either the passive, or the port, but the F3 of the ported is about 78 Hz and the F3 of the passives even higher (on fact the passives seem to under-perform compared to the port) (see attached screen grab). If I want to drop the F3 to 70 Hz or below the box has to be at least 3 liters, and the woofer appears to like a box that is somewhat bigger than that, but the gains in F3 don't seem to be justified over the 3 liter volume (marginal improvement in F3 with increasingly larger changes in box volume).

So, What gives? Is Winisd not good for small boxes? Not good or rather not particularly accurate compared to BassBox 6 Pro? BassBox Pro 6 is saying I can get an F3 of 73 Hz with a box volume of .03 cu ft (51 in cu or .84 liters) which is even SMALLER than the Parts Express project box. So, hep me!

I'll also attach what the response looks like for configurations with the 3 liter ported box, the other boxes were 2.5 liter for the ND105-PR and 2.8 liters for the dual ND90-PRs. That seemed to be the 'right' volume for each.

I'll try horn response next -- is there something else I should be modeling the box alignment with?

Thanks Guys!

[djg]

Seen these?

https://www.parts-express.com/passive-aggressive-mini-speaker-kit-pair--300-7148

[kineticmac]

Hey guys,

This is my first post on this forum and this is also the first sourround system i'm building!
I'm looking for a surround speaker build and this Helium speaker looks promising. It needs to be as small as possible so i can sell this to the wife.
I do have a few questions:

1. I've input the driver parameters into winISD and i can't seem to make it work. If i select a port of 3/4inch i get a length of 5.27inch and a port velocity of over 64!
The box is 0.04cubic feet en it is tuned to 71.48Hz.


































Isn't the port velocity way too high? What am i doing wrong?

2. The distance from listening position to speaker is around 3 feet. Will this speaker be loud enough to watch a movie (not music)?
The front speakers are 160W 91db distance10 feet.
3. I know the surrounds will never play anything like the front speakers but i'm wondering what a good spl level is for a surround speaker and i can't seem
to find it on google. What's a good level?

Any help is welcome!

[Dunk_c]

Interesting topic!
They do sound excellent with or without a small sub (Rel T-Zero is what I am using, I posted an amateurish freq response in post 429, and the sub is only doing duty up to 40Hz).
So as long as the amp is not clipping when sending bass signals to the HMM that it cannot reproduce, all should be OK and bass blocking filters might not have a significant effect on sound quality, especially as I am only listening at <75dB at 4 meters.

[scottsehlin]

I think bass blocking has the potential to help the midrange/midbass sound cleaner. How much difference it will make depends on how loud they are playing. It will be hard to kill them, even running unfiltered, so you can try it out as-is and decide if you want to add a filter later.

I once had a setup with a pair of bookshelf speakers with an F3 around 50 Hz that I ran wide open, then brought a sub in below that just to add extension. I felt it added something without changing the tonality of the main speakers - so was worth doing. That was a small system in a small to medium sized room mostly for personal listening, so I really wasn't straining the woofers too much.

[Dunk_c]

Thanks for that Guys. Scott, what are your thoughts on HMM integration with a sub bass speaker for fuller range sound reproduction, as opposed to speaker protection implications of a bass blocking filter?