Dayton RS sub project: Assault on SQ

[engr_dave]

:righton: Thank you Thomas. I knew it was something like that.

[coctostan]

Sorry to resurrect this thread, but I am considering opposing RSS390HO's. Do you wire these out of phase so when one is pushing, the other is pulling?

I've also heard that by inverting one of the drivers, you can reduce even order distortion. How does this work and why didn't you guys try this?

Great builds, by the way.

[ThomasW]

Sorry to resurrect this thread, but I am considering opposing RSS390HO's. Do you wire these out of phase so when one is pushing, the other is pulling?

Nope, they need to be wired in phase.

[coctostan]

Cool, thanks Thomas.

I see you guys are using an EP2500 and a K2. That is a huge amount of power relative to what my models suggest these drivers can take. Are you guys simply using a fraction of the amp's capability or are my models wrong?

[ThomasW]

It's a good idea to have some headroom in the amp. People buy the EP 2500 since it's not much more money than the EP-1500. The K2 was used because an amp he already owned.

[Brian Bunge]

The guy I built the quad RS 15 HO's is using the EP2500 and says that even at very loud levels the drivers are barely moving. I myself have decided on just using a pair of 15" HO's for my sub. I'm not quite sure what I'll use for an amp yet.

[coctostan]

I am thinking about opposing the RSS390HOs in plywood shells from tapeease (http://www.tapeease.com/Wood%20Cylinders.htm). Probably 24" dia x 27.5" height. My calculations estimate ~6.5 cu ft modeling to a QTC of 5.90. I plan to build a pair of these (4 drivers total) and run them stereo. I will probably try to find a Crown K1 or K2 to power the pair and clean it up with a DCX2496.

Anybody see any issues with this? This will be a dual use dedicated HT/music system. Hopefully they will integrate well with the sealed Statements I plan to build this winter.

[brent_s]

Cylinders implies you're going to fire the drivers vertically. Not sure you want to do that with the 390 series...WinISD puts GLoss (sag from gravity) at 4.7%. Technically, it's less than the recommended 5% limit.

-Brent

[coctostan]

I was under the impression that it was fine since it was within the 5% rule. My intentions were actually to build them so I could convert them from vertical to horizontal depending on which get a better response in the room. I was also thinking about making the horizontal cradle capable of holding both cylinders stacked if the stereo sub setup didn't work.

Should I be concerned with it being that close to the limit? (Thanks for the heads up by the way)

[ThomasW]

Should I be concerned with it being that close to the limit? (Thanks for the heads up by the way)

The effects of gravity are cumulative, so if you want the longest life out of the driver, don't mount it downfiring.

[engr_dave]

quad RS 15 HO's is using the EP2500 and says that even at very loud levels the drivers are barely moving

Interesting. At very loud levels, mine move a lot. Rough eyeballing says near 1" peak to peak. I haven't clipped the amp or bottomed the drivers yet, but I must have come close a few times. This is only at room-shaking, pants-fluttering volume/bass levels, however.

I've been very happy with the K2: silent and runs surprisingly cool.

I have read about inverting one of the drivers to cancel distortion. From what I gathered, the benefits are quite small, though. I may try it some day, but I honestly doubt I'll be able to hear a difference. Room interaction effects are MUCH more significant than even-order distortion artifacts.

Speaking of which... if you're building high-end subs like this you probably want to invest in a measurement mic and preamp and download "Room EQ Wizard". You'll be shocked at how ragged unequalized in-room response is. The DCX2496 has limited EQ functions - It's primarily a crossover. DEQ2496 is a powerful EQ (and RTA) that can accept digital parameters from REQW.

One nice thing about vertical mounting a dual-driver design (assuming you make the feet mountable to either end and don't invert one of the drivers) is that you can flip them over occasionally to eliminate the cumulative sag that Thomas spoke of.

Good luck, I think you'll be happy with the result. :T

[Brian Bunge]

Interesting. At very loud levels, mine move a lot. Rough eyeballing says near 1" peak to peak. I haven't clipped the amp or bottomed the drivers yet, but I must have come close a few times. This is only at room-shaking, pants-fluttering volume/bass levels, however.

It could very well be that your idea of loud and his idea of loud are quite different. Also, the internal volume in the enclosure I built is probably a bit smaller than yours so the air spring might be controlling driver movement to a greater extent than your enclosure(s). I do know that I ran them pretty hard when I was testing them at home and they were not moving much. Of course I didn't want to blow up someone else's sub either!

[ThomasW]

One nice thing about vertical mounting a dual-driver design (assuming you make the feet mountable to either end and don't invert one of the drivers) is that you can flip them over occasionally to eliminate the cumulative sag that Thomas spoke of.

Unfortunately the stretching of the suspension continues regardless of whether the drivers are facing up or down...and as said earlier these effects are cummulative.

When the cones are heavy it's best to mount the drivers vertically if the goal is to have the drivers last a long time.

PE's 5yr product warranty doesn't cover driver death from the effects of horizontal mounting.

[coctostan]

Interesting. At very loud levels, mine move a lot. Rough eyeballing says near 1" peak to peak. I haven't clipped the amp or bottomed the drivers yet, but I must have come close a few times. This is only at room-shaking, pants-fluttering volume/bass levels, however.

Could it be that the high levels you guys are talking about are at different frequencies? High levels at 15hz will push the cone to its limits. High levels at 40hz won't move the cone much. Right? (I am pretty noob to this, so I could certainly be wrong)

Speaking of which... if you're building high-end subs like this you probably want to invest in a measurement mic and preamp and download "Room EQ Wizard". You'll be shocked at how ragged unequalized in-room response is. The DCX2496 has limited EQ functions - It's primarily a crossover. DEQ2496 is a powerful EQ (and RTA) that can accept digital parameters from REQW.

I was planning on going the REW route. From my research, the DEQ2496 is not compatible with REW. I'm also not sure why the DCX2496 would be inadequate. I know it doesn't take measurements, but it should allow me to simulate a LT circuit using a shelving filter and then apply probably 5-6 PEQs. Am I wrong in these assumptions? Dave, what kind of filtering are you using?

I really appreciate the advice. I will probably align the tubes horizontally. They will be pretty close to square so it shouldn't really matter from a sound standpoint which way I orient them.

I was originally looking into some 15" large ported sonosubs, but I think I would prefer something much smaller. Although these guys probably won't have the output of the sonosubs, I think they will be adequate for my 3500 ft3 room.

[Geoff]

I see that InPhase is getting ahead of me, so I'd better post some progress! :B

I sanded the primer with 220 and had to apply automotive spot putty in a few areas. Then another round of primer and final sand with 320. Finish was DuPont Lucite "Diamond Black" automotive acrylic lacquer. I shot three medium-wet coats which pretty much emptied the quart that I bought (thinned about 100% to 17sec viscosity). I gave it a week to dry and shrink, then color sanded with 600, then 1200. I used paint thinner as a lubricant because I'm paranoid about getting water around MDF. DuPont 606S white polishing compound gave it a final finish, although probably any decent rubbing/polishing compound would work. Be careful not to rub through the finish on the corners, although the 1/2" roundover really helps minimize that danger.

The last photo shows PE spikes and terminals installed on the bottom.

Next steps - wiring, insulation, and driver install. :T

I'm a bit curious as to why you and others choose acrylic lacquer as opposed to usually much tougher enamel for ones gloss finish.??

It's been along time since I sprayed lacquer (body shop like 15 years plus) & not sure if "acrylic" based lacquer was even around then. Personaly I did not like working with it as temp senstivity while painting was a constant thing, along with ("as time passed on") re-polishing was required keep it looking excellent. Things advance with paints with time like most everything, so lacqure specificaly acrylic lacqure might not be anything like the lacqure I was used to.

I much prefer automotive PPG base/clear coat enamel ($$) or even Sherwin W. as it's very tough, last nearly forever when applied correctly and dose not require re-polishing/swirl remover etc, nearly as often, especially in a home enviroment. More sand & paint steps usually but worth it IMO. Also the NO shrink 2 part primers of today are a vast improvment over the best old primers.

I'm all for getting updated/education in the latest atomotive paint goodies & "reasons one might prefer using "acrylic" lacquer over enamel. Aside from less prep/paint steps, lacqure touchup or maybe later fade in reasons which I'm sure your aware of.

By the way supurb looking finish.!! Black glass is the way it should look and you seem to have captured that extremly well.!
Just beautiful wood and paint work.

Regards
Geoff ¥

[engr_dave]

Thanks Geoff. You're probably right that modern enamels and base/clear systems have advantages over lacquer. Over the years I've just gotten comfortable with lacquer. It is easy to work with, one-step, no mixing or pot life issues, dries quickly and polishes nicely, no witness lines when buffing through multiple coats, and repair/blending is a snap. Temperature is an issue as you mentioned, but picking the right thinner "speed" and/or retarder usually takes care of that.

I don't have access to a paint booth, so every project gets color-sanded and buffed. In years past, enamels were trickier to buff out. Today's catalyzed enamels and clearcoats get much harder much faster and may be equivalent to -or better than -lacquer.

It used to be that lacquer was cheaper than enamel, particularly two-part enamels. But I was shocked recently to find the price of DuPont Lucite black lacquer nearly twice that of black Centari (enamel). Apparently lacquers are becoming scarce and pricey as a result of VOC regulations. It looks like I'll be switching to enamels.