Cost-is-no-object DIY sub (1 Viewer)

[Dave Milne]

I've tried to surf through the plethora of DIY sub info in this forum but bogged down under the mountain of posts.

I'd like to build a front (main) sub to complement my LFE sub (which is built into the platform for the second row of seats in the theater... it makes a nice buttkicker as well as LFE sub). The LFE sub uses a JBL 2245 18" driver in 10 cu.ft. vented, equalized. It's flat to 22 Hz and puts out 121dB at 300 watts.

Bottom line: What's the best DIY sub assuming that driver cost is not an object -well, OK, under $1000.

Cabinet complexity is also not an object (PR, high-order and compound designs OK) but total volume is less than 8 cu.ft.

Electrically assisted is OK, i.e. sixth-order vented, equalized.

Power will be 550 or 750 w (I have a couple of bridgeable amps available)

By the way, my Lexicon MC-12 pre-pro has fully adjustable crossovers and separate delays for the LFE and main subs so that's not a problem.

 

[Jeff Rosz]

hello dave,
subjective but enviable, but let me just throw this out there...
how bout ~3/4 of this?... Link Removed

 

[Mark Seaton]

Hi Dave,
While I understand the cost-no-object factor you mention, with current drivers on the market, and the box size you are considering, you will find that your main task will be making the best use of the 550-750W you have. While I'm still waiting to see a driver which can achieve the same bandwidth and efficiency of our ContraBass, there are some great options if you open up to the purchase of a new amplifier like a Crown K2. The ContraBass kit will likely be going away soon, but they are available at the moment.
If I was designing a cost-no-object, 8 cu.ft., DIY subwoofer, I would look in the direction of the new Adire XBL^2 15" home theater driver discussed in This Thread. That page contains the projected T/S parameters of the driver. What I see as the killer 8 cu.ft. solution would be 2 of these drivers with 4 18" Stryke dual spyder PRs massed up to their limits (I would actually go past some, but you do that at your own risk), with a box fully stuffed with Miraflex, you should be set. From there just add a BIG amp and ideally an EQ to maximize the low end performance. This should equal the output of your current sub to 14-16Hz in-room, and so long as you don't let 5Hz dyno-stomps through, you will never bottom it out. Having a pair of drivers will help greatly with any power compression at moderate levels while allowing the high power to take care of dynamics, just how you want it.
One critical issue you didn't mention to us is the size of this room? Had you possibly considered using a pair of smaller subwoofers? What are you using as mains so we can compare what sort of headroom is justifiable? If absolute sound quality is your goal, I would suggest using multiple sealed drivers with lots of power and electronic correction.

 

[Greg Monfort]

>The ContraBass kit will likely be going away soon, but they are available at the moment.

====

Just the kit, or is the CB being superceded with a new design?

GM

 

[Mark Seaton]

Greg inquired:

Just the kit, or is the CB being superceded with a new design?

The kit particularly. The CB will likely still be offered as-is to sound contractors as it is now, with primary use for effects theaters and electronic organ extension, where the home theater market will see a more polished (mostly inside) Theater Calibrated version of the ContraBass, with associated pricing change/increase.
When power is limited, we still don't have a way to really beat the performance of the ContraBass as of yet. We may certainly keep our eyes open for parts which could enhance the performance though... Now if we could only find an effective PR with 5" p-p...
Of course we do have some other toys in the works.

 

[Vishwa Somayaji]

What about a sub based on that SV18 driver from subwoofers.com? That driver alone is $749 and its specs look great. For an 18" driver it has a great excursion.

 

[Robert_Gaither]

I don't know about the SV18 but the Northcreek Leviathon driver seems to be the best 18" out there but at it's price I think one could use multiple drivers from either Blueprint, Stryke, or Adire for the cost of either one of the above.

Of course if price is truly no limit then maybe getting a few custom built driver with the specs you abosulutely want are the way to go (contant TC sounds).

 

[Dave Milne]

Thanks guys, you've pointed me to some great stuff.
Jeff, I'd LOVE to do an IB, but there's just not any room available to use as an "enclosure" --they don't do basements in Arizona.
Mark, the XBL^2 driver looks interesting but geez... is there enough surface area on an 8 cu.ft. box for two 15" drivers and 4 18" PRs 85dB sensitivity is a paradigm shift for me; would need to step up to some serious amplifier power. BTW my speakers are all custom-built Dynaudio; L-R are Myrage (WMTMW config with 2x24W100, 2xD76 and 330D Esotar), center and sides are Twynn (MTM with 2x17W75 and D260 Esotec) rears are Xennon 3/75 (17W75, D54, D21). The theater is 14x22x9. And what is ContraBass? I surfed the servodrive website and there's no mention of subwoofers or drivers...
Robert, the Northcreek Leviathan looks nice. However, one forum thread I saw indicated that it was a re-badged Seismic 8196E. Would Seismic sell this driver directly?
You guys have me jazzed to cut some MDF... thanks!

 

[Mark Seaton]

Dave wrote:

85dB sensitivity is a paradigm shift for me; would need to step up to some serious amplifier power.

Indeed it is major shift in efficiency, yet you will find that with a limit on the enclosure volume, different designs will generally be trading off passband efficiency with low end response, or the slope of the rolloff. Comparing two drivers in the same volume enclosure, with the same input power, you will find that the resulting output near cutoff will be similar, with the rest of the response hinged around that point. The ContraBass still follows similar laws, but due to its very high motor strength and other possible parameters can achieve higher efficiency. With this higher efficiency and maintained low cutoff there is a resulting steeper corner below tuning. Almost all of the designs take in various trade-offs. As for the NC Leviathon driver mentioned, do note it is some slight variant (cosmetic?) of the Seismic driver. I've never seen it confirmed either way, but there has been much speculation as to the real vs. posted T/S parameters. Getting back to the low sensitivity issue, this is one reason I recommended using TWO of these newer 15s. With two at work, the large amps will be needed more to prevent clipping than to sustain the required output. With one driver per channel on a Crown K2, MacroTech, or big QSC amp you gain 6dB in output (in the passband) with both drivers driven with equal power over a single driver(equivalent to 3dB gain at the same total 1W input).
I would suggest you consider more power given the quality and capabilities of your system. It could prove quite pleasing to add another 1/2 octave to the system. Looking at some of the higher sensitivity options out there, you may find that selling your old amps and upgrading to maybe a K2 if used in-room (no fan), or other behemoth amplifier would end up at similar cost.
The ContraBass kit is not something we ever had planned to offer for sale. Our designer, Tom Danley, has long been active in various DIY communities. Out of generosity from Tom, a kit was offered a few years back to the DIY-BASS list, which is when Greg got his pair. About a year ago, Mike Early of Link Removed apparently inquired about offering the kits online. The kit details can be found Link Removed. As you will see, it is not an in-expensive kit compared to conventional driver systems. Where many had kept the price down was in finding suitable surplus motors, yet you do have to deal with the fact that most suitable surplus motors you will find have a DCR of 0.8-1.5 Ohms. For a variety of reasons, the kit's offering at EarlyM will be coming to an end in the near future, but I will give a few week notice to the DIY forums and boards to not cut off any who had been holding out. I'm thinking we will find some avenue to allow some kit sales to those in the DIY community, probably through one of the DIY list and/or forums.
Regards,

 

[Dave Milne]

Mark, thanks for the info and links.

Wow! I didn't realize the ContraBass was such a unique approach. I think I'll settle for conventional drivers in a conventional box. Call me old fashioned.

So I understand the recommendation is 8 cu.ft. with two XBL^2s and 4 PR18s massed up to 3Kg each. I haven't tried to model this in BassBox Pro (the only program I have at the moment) but I infer this is an Fb of 16-18Hz (?)

My PR experience is limited, but I assume that it would be acoustically equivalent to create two 4 cu.ft. boxes --each with a single XBL^2 and two 3Kg PR-18s. This would provide some extra placement options and ease the transportation (weight and size) problem.

Any updates on the release date and pre-order price of the XBL^2? Meanwhile, I guess I'll start shopping for a big amp like the K2. I'm also finishing a preamp for my measurement mic so I can map out the best placement options...

Dave

 

[Robert_Gaither]

The emails I've exchanged with Northcreekmusic in the past stated that they literally just use the frame of the seismic and customize it for their use (Wilson does the same) with a different cone material, surround, and motor (since if I remember correctly the original Seismic was designed for pro use). Unfortunately to me, this driver would be hard pressed compared to a pair of the newer 15" (or 18" from Blueprint) woofers from the sources I stated earlier eq'ed and I'll take it from Mark about the PRs (this is one subject that I'm trying to learn about and am interested in is the PRs).

What's also nice about buying any of these drivers is that you will definitely get direct support in building your new sub and they should steer you in the correct direction from most likely the individuals who spec'ed them out.