Pico Neo Plans?

[stephenmarklay]

I've built two of the Pico Neos now and both times they were a big hit. Built one set for boy's dorm room and the last set for the nephew's Christmas present. The BIL texted a couple days after Christmas, "Those speakers haven't stopped going since we got home last night. Best gift ever." Chris, you hit a home run with the Pico Neo.

The rs225 also make very disturbing sounds then they hit xmax.

Thanks Kornbread! I can’t wait to build them up!

[Kornbread]

Y
My notes say that its Xmax is 5mm (that's where distortion starts to rise significantly). I believe that its got an Xmech (or Xlim) of about 2X that number though. That's where the suspension bottoms out ... Either one can take the driver's rated 20w RMS (temporarily) w/out damage. MOST drivers can't take that kind of power above their Xmax ratings, although most of Dayton's ND series can. Dayton's "Classic" series (5", 6.5", 8", 10") make very bad sounds when they breach Xmax.

I've built two of the Pico Neos now and both times they were a big hit. Built one set for boy's dorm room and the last set for the nephew's Christmas present. The BIL texted a couple days after Christmas, "Those speakers haven't stopped going since we got home last night. Best gift ever." Chris, you hit a home run with the Pico Neo.

Need to add that the latest Pici were powered with a clearance fx202a amps ($39) from PE. It is surprising how good the paring sounds for such an economical outlay of cash and effort. Also, the power and output levels the ns3 can reach without protest is impressive. In Bassotronic's, Bass I Love You, parts of the work reach down to, IIRC, 10hz. It is impressive watching those tiny buggers way exceed their rated 5mm xmax when putting them through their paces. They look like a pair of demented sexual implements getting their jig on.

The rs225 also make very disturbing sounds then they hit xmax.

[stephenmarklay]

Your green curve VERY closely matches my orig. PicoNeo (I DATS'd MY NS3s about 8 yrs ago: Q .69, F 84, V .035cf)
My notes say that its Xmax is 5mm (that's where distortion starts to rise significantly). I believe that its got an Xmech (or Xlim) of about 2X that number though. That's where the suspension bottoms out.
Either of your alignments will work fine. Either one can take the driver's rated 20w RMS (temporarily) w/out damage. MOST drivers can't take that kind of power above their Xmax ratings, although most of Dayton's ND series can. Dayton's "Classic" series (5", 6.5", 8", 10") make very bad sounds when they breach Xmax.

Don't look at ISD's "max power curves" to see the drivers' limitations, look at the "cone excursion" curves (adj. the "signal" watts) for a better idea.

Just because WinISD's excursion plots run down to 20Hz (or below) doesn't mean you've got to be concerned about a driver/box combo playing that low. If a driver/box rolls off @ 80Hz, it won't be outputting enough down 2 octaves lower to be of concern. I like to have at least half-an-octave "leeway" below F3 for overexcursion (a full octave offers more protection, but often can't be managed).

Over the yrs (like, the last 5-10) I've seen Dayton's T/S specs vary quite a bit (once they got DATS/Omnimic it seems like they might update data every few yrs. or so) on the ND series - usually in a complimentary way though (as far as box modeling goes).
For the ND90-8, my latest data (2017) is: Q .65, F 71, V .06cf
An older "batch" had: Q .65, F 80, V .05 (w/a resultant modeled F3 roughly 10Hz higher).
You've got to remember that when you pick apart a "published" design (for study), you're only looking at a snapshot in time. The laws of physics don't change, but driver "updates" and production batch runs certainly do.

Thank you so much Chris.

Working backwards in you comments. I definitely don’t want to sound like I am “picking apart” your design. But, I think you took the right way. Trying to model a proven design helps me understand when a model is “good” or workable. I just don’t have enough experience to look at a plot and say “yeah that looks good” and more forward.

Second, your comments about excursion help a lot. I wondered about that and wrongly surmised that WinISD was showing the excursion down to 20hz based on the output I see on the SPL plot. I just learned something very useful. I was looking at the excursion plots and adjusting the signal to keep excursion below xmax down to 20hz but I see that is not necessary.

I plan on getting Dats this year which will be great!

[Chris Roemer]

Your green curve VERY closely matches my orig. PicoNeo (I DATS'd MY NS3s about 8 yrs ago: Q .69, F 84, V .035cf)
My notes say that its Xmax is 5mm (that's where distortion starts to rise significantly). I believe that its got an Xmech (or Xlim) of about 2X that number though. That's where the suspension bottoms out.
Either of your alignments will work fine. Either one can take the driver's rated 20w RMS (temporarily) w/out damage. MOST drivers can't take that kind of power above their Xmax ratings, although most of Dayton's ND series can. Dayton's "Classic" series (5", 6.5", 8", 10") make very bad sounds when they breach Xmax.

Don't look at ISD's "max power curves" to see the drivers' limitations, look at the "cone excursion" curves (adj. the "signal" watts) for a better idea.

Just because WinISD's excursion plots run down to 20Hz (or below) doesn't mean you've got to be concerned about a driver/box combo playing that low. If a driver/box rolls off @ 80Hz, it won't be outputting enough down 2 octaves lower to be of concern. I like to have at least half-an-octave "leeway" below F3 for overexcursion (a full octave offers more protection, but often can't be managed).

Over the yrs (like, the last 5-10) I've seen Dayton's T/S specs vary quite a bit (once they got DATS/Omnimic it seems like they might update data every few yrs. or so) on the ND series - usually in a complimentary way though (as far as box modeling goes).
For the ND90-8, my latest data (2017) is: Q .65, F 71, V .06cf
An older "batch" had: Q .65, F 80, V .05 (w/a resultant modeled F3 roughly 10Hz higher).
You've got to remember that when you pick apart a "published" design (for study), you're only looking at a snapshot in time. The laws of physics don't change, but driver "updates" and production batch runs certainly do.

[stephenmarklay]

Chris’ pico neo was brought to my attention and now I have to try it myself. I am in need of a learning moment however

I used winISD to play with both the AURA NS3 and the Dayton ND90 which model similarly. I included the plots to make sure I “get” it…

Based on what I read the highlighted graph, the aluminum NS3 in a 1.5cf box tuned to 56hz, roughly uses the parameters used in the Pico Neo. I don’t think the matches the description of the curve Chris obtained however.

THe ND-90 with the same parameters is directly below the highlighted one with a 1 db peak around 58hz (the tuning freq on this model). This looks closer to what I remember Chris writing about and looks promising to me (which is pretty uneducated I might add).


The similar curve but with a little lower F3 is the aluminum NS3 but now in a 0.2cf box and tuned to 50hz. This looks like it may also be a winner.

Just as a reference the curve with the least extension is the TCP-115. That one does not go as deep (wow right?) but also looks pretty good to me.


The one thing I noticed is that each of these is only good for about 3W (5w for the Dayton) before I run into excursion problems.

Does any of this jive with reality?

[tdv]

Re: Pico Neo Plans?

Schedule 80 1.25" PVC has an average inside diameter of 1.255". You would probably have to special order this at the big box stores. If you have a plumbing shop near by you may have better luck.

[fastbike1]

Re: Pico Neo Plans?

The dimensions aren't wrong. Schedule 40 and 80 pipe is also sold in "nominal" dimensions just like lumber.

Thanks. Looks like HD has the dimensions wrong. Looked up Sch 40 and it is 1.38. So I am back to Chris's suggestion of the BT-55 Tube. Found it on Amazon:

BT-55 Body tube specifications: Inside Dimensions - 1.283 in. Outside Dimensions - 1.325 in

[blank264]

Re: Pico Neo Plans?

What would the port length change too if 1.38 pvc was used?

[ani_101]

Re: Pico Neo Plans?

It will throw your tuning off a bit (I believe Paul C made this mistake once). A 1.25" Sch 40 pipe is actually 1 3/8" ID. From 2" and above the actual diameters are close enough to nominal to not matter to the tuning.

Thanks. Looks like HD has the dimensions wrong. Looked up Sch 40 and it is 1.38. So I am back to Chris's suggestion of the BT-55 Tube. Found it on Amazon:

BT-55 Body tube specifications: Inside Dimensions - 1.283 in. Outside Dimensions - 1.325 in

[fastbike1]

Re: Pico Neo Plans?

It will throw your tuning off a bit (I believe Paul C made this mistake once). A 1.25" Sch 40 pipe is actually 1 3/8" ID. From 2" and above the actual diameters are close enough to nominal to not matter to the tuning.

I found this pipe at Home Depot - seems to be a 1.25 inch PVC pipe.
1.25 inch pipe

[Chris Roemer]

Re: Pico Neo Plans?

I found this pipe at Home Depot - seems to be a 1.25 inch PVC pipe.
1.25 inch pipe

looks good to me

[Whitneyville1]

Re: Pico Neo Plans?

A little "over kill". Drain pipe for sinks works fine. A paper towel core coated with lots of layers of polyurethane varnish can even be used (!)

[ani_101]

Re: Pico Neo Plans?

I found this pipe at Home Depot - seems to be a 1.25 inch PVC pipe.
1.25 inch pipe

[alphaiii]

Re: Pico Neo Plans?

No problem, exactly, but volume's not the thing. It's more like length has to be proportional to cross section. A larger dia. vent needs to be longer to tune the same box to the same freq. A 1.375 vent should probably be 7" long then, not 5" long. (This is one of the problems with getting a large enough vent to prevent chuffing in a small enough box. A smaller vent fits better, but has a higher probability of chuffing.)

Chris

OK, got ya. I haven't done much in the way of modeling ported designs, only sealed subs... so I'm new to this still.

Thanks for the input.

[Chris Roemer]

Re: Pico Neo Plans?

Any issue with using this port in the Pico Neo:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-388

5" length would put it pretty close to the 1.25"x6" port's volume.

No problem, exactly, but volume's not the thing. It's more like length has to be proportional to cross section. A larger dia. vent needs to be longer to tune the same box to the same freq. A 1.375 vent should probably be 7" long then, not 5" long. (This is one of the problems with getting a large enough vent to prevent chuffing in a small enough box. A smaller vent fits better, but has a higher probability of chuffing.)

Chris