Subwoofer decision agony for serious music-only setup... please help

[hex168]

Reply to Post #6 - sealed.

[lunchmoney]

Thanks. A bit too expensive though, particularly since I'd like to use the DSP plate amps instead of the Crown (I have no other EQ)

[tomzarbo]

I would check the vent velocity graph, it might be getting high with a 1.5 inch port.
Also, make sure your input voltage is something approaching real world... I can't see on those graphs.
TomZ

[lunchmoney]

I would check the vent velocity graph, it might be getting high with a 1.5 inch port.
Also, make sure your input voltage is something approaching real world... I can't see on those graphs.
TomZ

Thanks Tom. Is this what you're referring to?

[djg]

Cheap? The MCM 55-2421 8" sub. I have two in my Table Tuba. $30 at Newark. One might call it a Tang Band W8-740 copy. With a 10" PR as several suggested designs here.

[tomzarbo]

I remember that driver. It only has about 2/3 of the excursion of the W8-740 which I've seen moving a lot more than it's listed Xmax...
...but boy, it sure is a TON cheaper! ...And you can actually purchase one instead of 50. Nice one!
TomZ

[tomzarbo]

Here is a screen shot, not sure how good the plot line shows up though...


This is with a test driver that came with the program I believe, just to show what I was talking about.
If you don't raise the 'system input power' I don't think you will be able to tell what the vent velocity will be at working power levels.

The graph is under the second from the left where it defaults to 'transfer function magnitude' I think.

Tomz

[lunchmoney]

I see.... not sure what to put there.... I'd be using a 250 watt plate amp, but I'm skeptical of it putting out that much power. Any recommendation?

[tomzarbo]

I'd try a level that puts excursion at full published Xmax at least.

[billfitzmaurice]

That or Pe, whichever comes first.

[lunchmoney]

Ok, so if I enter 130W for "System input power" I reach the 8.4 Xmax of the DCS205-4 (give or take).

The bad news is that in order to keep the port velocity under 17m/s I need a port that's 3.75" x 32.20"... sounds like the port isn't making sense.

[Pete Basel]

How about this, with the DSP plate amp - looks to be on sale: https://www.parts-express.com/Dayton...net-P-300-7091
I'd simulate it to see how much EQ you'll need to get it -3dB in the low 30s.
This plate amp is also on sale, check if there is enough power to get the woofer to Xmax at about 30-35 Hz:
https://www.parts-express.com/Dayton...IaAoTOEALw_wcB

Probably a lot more amp features than you need.

Sealed you need all the displacement you can get, I prefer a 12".

[invaderzim]

" is also on sale "

They've really gone to making everything look like it is on discount sale even more than before. While that likely works from a marketing standpoint it is annoying when they make it harder to spot what is an actual special sale and what is just a price.

[Pete Basel]

invaderzim I'm aware that PE discounts everything all the time but I _thought_
that those prices looked lower than usual. You might be right but still the prices
are pretty good.

[a4eaudio]

Ok, so if I enter 130W for "System input power" I reach the 8.4 Xmax of the DCS205-4 (give or take).
The bad news is that in order to keep the port velocity under 17m/s I need a port that's 3.75" x 32.20"... sounds like the port isn't making sense.

Well, I think your simulation is correct. BUT...

• A larger cabinet and/or higher tuning will shorten the required port. For example, 0.80 cf tuned to 36Hz now your port is 3.75" x 26" (which still doesn't seem reasonable)
• You can add a flare to your port to reduce chuffing and get away with something higher than 17m/s. A recent thread suggests most of the difference is in the flare on the outside but you can add a 3/4" roundover to the outside (and inside if you want) with a router bit. A 3" x 16" port now gets you to 27 m/s which is probably an okay port velocity but still maybe not feasible port length.
• The port velocities above are at 130 watts and xmax, are you really listening at this volume level? At 65W you are down 3db and a 2.5" x 11" port gets you to port velocity of 26 m/s.

I'm just fiddling in WinISD and don't have the experience that others do, what do you experienced designers target when designing a realistic sub that otherwise would require an impossibly long port length?

[fpitas]

Well, I think your simulation is correct. BUT...

• A larger cabinet and/or higher tuning will shorten the required port. For example, 0.80 cf tuned to 36Hz now your port is 3.75" x 26" (which still doesn't seem reasonable)
• You can add a flare to your port to reduce chuffing and get away with something higher than 17m/s. A recent thread suggests most of the difference is in the flare on the outside but you can add a 3/4" roundover to the outside (and inside if you want) with a router bit. A 3" x 16" port now gets you to 27 m/s which is probably an okay port velocity but still maybe not feasible port length.
• The port velocities above are at 130 watts and xmax, are you really listening at this volume level? At 65W you are down 3db and a 2.5" x 11" port gets you to port velocity of 26 m/s.

I'm just fiddling in WinISD and don't have the experience that others do, what do you experienced designers target when designing a realistic sub that otherwise would require an impossibly long port length?

If you use a bottom or rear port, the velocity can be higher because the chuffing noises get attenuated. You'll still get power compression. It's fun to design for continuous full power at the lowest frequency, but you have to ask yourself how realistic that is. I guess if you're a super-duper basshead maybe.

[LOUT]

I think a pair of $20/each 8" PR's like these:
https://www.parts-express.com/Dayton...diator-295-492
with about 30grams added could get a DCS205-4 down to ~40hz F3 in less than 1ft-cu.

A single, larger PR like this:
https://www.parts-express.com/Dayton...diator-295-494
would be cheaper and likely dig a couple hz deeper, but this particular one will limit your volume headroom about -2db (around 80watts I think)....while a nicer PR with more XMAX/movement will almost surely cost more than the pair of $20/each 8" listed above.


If you don't mind the box building aspect (and if it's not too much trouble), it might be a good idea to test something like a 3inch-diameter PVC pipe ported box first. If you like it, sweet, finish the box and make it look nice. If you notice bothersome port wind-noises with some music, then those PR's are likely worth the added cost.

For whatever it's worth, I made a couple boxes purposely using a ridiculously small port-diameter, and for most music I don't start getting bothered by their puffing noises until they're somewhere in the ~60m/s range by some rough SIM calculations. It's definitely easier to hear with sine-wave tests or bits of music where everything goes away except a loud, clean, deep synth-bass....otherwise I've been mostly pleasantly surprised.
That said, I'm NOT a picky listener for the most part as far as I can tell. But I'd hazard a guess that ~30m/s shouldn't be a problem for many folks.

[Pete Basel]

Old design here but both the JBL and Infinity drivers are NLA, not sure if there is a good substitute:
http://techtalk.parts-express.com/fo...he-way-to-20hz

I always thought that going for 20 Hz was a bit much for an 8", I'd go for 28 for music with a more
efficient driver.

[hex168]

Sub EQ is cheap (unit linked is $60), but I agree it is starting to add up. Perhaps defer EQ until the $ are handy?

https://www.parts-express.com/Dayton...roller-230-520

[hex168]

You will get a better result from two physically separated subs and DSP EQ than from single sub alternatives. If you want to start to go down the rabbit hole:

https://www.audiosciencereview.com/f...timization.15/