What would you do?

[johnsalvini]

Hi folks, I have been lurking here for a couple months and have learned quite a bit from you all. Thanks! Hope I can contribute to the "collective" as time goes on.

Here are a few "before" pictures:

Images not available

So here's the challenge: my 2 ch setup is in a large room above the garages. I added a large dormer in there many years ago, and framed in soffits on either side for decoration. I have some improvised subs in these soffits & it sounds better there than most other locations in the room. AND, they are situated directly behind the main speakers from the listening position. So I think that if the entire soffit on each side was converted into a sub box, a really first class setup could be realized. I'm going to start gutting them out and building in double-layered and braced boxes within the resulting spaces. I'm thinking of making the front opening about 32"w X 38"h. That way I can have the flexibility to substitute different front baffles and drivers. This size could accomodate up to: (2) 18", or (4) 12", or (4) 15" drivers on each side...could make for some fun experimenting in the future. I could even build the opening so that a vertical internal baffle could divide the cabinet into two cavities with different volumes. That way a couple 12s could be augmented by an 18. (of course that would mean another crossover).

So the possibilities are exciting (well, maybe I'm wierd that way). I looked through the Parts Express, Madisound, and Zalytron catalogs; plus all the sub drivers mentioned on this forum (adire, sonic craft, adire, TC sounds, etc.)
OMG, there are millions!

So, to the point: What would YOU do?

Goals: (in order of priority, based on my limited knowledge)
1) Musicality...this setup will be strictly for 2 channel music.
2) Highest sound quality/low distortion.
3) Able to convey even subtle low freq info (such as an ever-so-lightly touched kickdrum in the background of a piece where you "sense" it more than actually hearing it).
4) Flexibility to use with standard 2way monitors, or with high efficiency monitors for tube equipment, or with ribbons or electrostats in the future. (might not be possible; I don't know)
5) Super low frequencies are nice but not as important as all the above.
note: I don't mind spending extra on the drivers if it makes a difference since the cabinets will be totally cheap and I already have the electronic xover.

Stats:
-room volume about 3900 cu ft. (22'4"X23'2"X7'6"ave.)
-volume of proposed boxes about 40.8 cu ft(1150 l each) (21d"X60h"X56w")
-current equip:
Arcam CD33 cd player
DEQX PDC 2.6 preamp/active xover/para eq
Bel Canto eVo6 6 ch amp
North Creek Vision Monitors (SS D2905/9900 Revelator Tweets & SS 15S/8530K 5" Mids) originally designed to high pass at 85hz 3rd order.
Crown K2 amp standing by for this project.

sure appreciate your input,
hope this wasn't too long,

John

[rumatt]

photo link no workie

[ThomasW]

Link fixed by Mr Moderator..

[johnsalvini]

Thanks for fixing the link Thomas.

We talked about this once and you suggested the 12" Auras. At the time I thought that it would be useful to be able to cross these over at up to 400hz, but the more I think about it, the less it seems necessary to go that high. What do you think? Almost all main speakers go cleanly down to at least 90 hz.

John

[ThomasW]

Hi John... :T

The rule of thumb we use is there should be linear operation a full octave above and below the XO point. Doing that guarantees no holes or other weirdness in the frequency response.

This means the mains need to be linear to 45Hz or so for a 90Hz XO point. If they aren't the XO point should be raised.

ColoradoTom just bought 8 of the AuraSound 12"s for a little add-on dipole woofer project to his big SoundLab ESLs. I'll know more when I hear what those sound like.

I guess the decision you should make is whether or not to keep and work with, or replace the mains. Once that decision is made, it's easier to figure out the other variables.

BTW is there a primary listening area? Or is the whole room the listening area?

[johnsalvini]

That rule of thumb makes sense since xovers provide gradual slopes.

Intuitively it seems like building the subs into the soffits could be a nice, clean, and acoustically sound(ha-ha) installation. Is it possible to make them versatile and sensitive enough to use with just about any mains? I really love it when the music just seems to flow effortlessly and that's what I'd like these subs to be capable of. The mains that I have now sound awfully good to me; and I still haven't run dedicated circuits or tried different cables or invested in a quality equipment rack yet. Last night I unwrapped a couple new CDs and for about 3 hours was just in awe how good it was. So the Visions will be staying for a while. In the future, though, I would like to try some other speakers, and maybe some tube gear, too.

I'm trying to get back to working on the HT/Library (a long term project) but would have serious withdrawls without "groovy tunes" in the meantime (can you relate?). I can bang out some boxes for this really quickly since, being built in, they don't have to be pretty.

The whole room is the listening area. It was a large bedroom over the garage but my wife is letting me use it as a dedicated listening room til the HT is done. (It might be a little difficult to get the fox out of the henhouse once he's in there; wink). These subs will stay built into the soffits til we sell the house. If/when that day comes, I can just pull them out, replace them with built-in bookcases, and then patch the drywall.

The internal volume of each box can be anything up to about 40 cu ft.

Image not available

I still can't seem to get pics to display. Maybe another web picture host would work.

[johnsalvini]

Finally got it. Here is the room presently:

[johnsalvini]

And this is with the cover over little sub removed. I want to cut into the drywall where the little sub is now and basically convert the entire soffit into a sub enclosure by lining the interior with a layer of OSB and another of MDF. And then make the front opening about the size of the one that is there now...except not as wide and moved over toward the edge away from the side walls.

[ThomasW]

If the 'sweet spot' is the sofa, the idea of using the AuraSound 12"s in the walls still makes sense to me. I'd make the actual baffle removable, so the number of drivers could be adjusted to the desired output. Start with a pair/side.

[johnsalvini]

Thanks for the guidance Thomas. I'll start doing the demolition this week.

I'm curious to know the rationalle for determining between, say, 2X12" or 4X12", or 2x15", or 4X15", or even an 18" or 2.

John

[ThomasW]

Multiple AuraSound 15"s and 18"s are insanely expensive.

Since you have the huge IB in the library, do you need/want overkill levels of bass in this room too? If so we might look at other drivers.

A pair of 12"s usually has more output that a single 15" of similar Xmax. So the idea would be start with 2-12"s/side because I think that will be plenty, but leave room for more if needed/wanted.

[johnsalvini]

:rofl: What! The king of overkill telling someone to exercise restraint? :rofl: Oh my! Usually I ask myself, "What would Tim Taylor do?" and that has guided most of my home improvement projects. Why have an electric garbage disposer when you could get a 13hp Honda powered one that you could chip tree branches with?

Seriously though, you're absolutely right. No overkill... I just want really high quality base in here. I will do just as you say & build it so the front baffles can be reconfigured. As a matter of fact, it would probably be smarter to go ahead & build in the bookcases. Then build the sealed sub cabinets to just fit inside of them instead of all the shelves.

This would ,however, cut the internal volume down to about 20 cu ft each. That should still be plenty, don't you think? At what point does the size of the box start to affect the movement of the cones in such a way that it acts as a spring and makes it sound mushy or boomy? At that point I'd have to get a bass box design program & try to figure out how to use it.

Thanks for all your help,

In addition to some other blessings, I am greatful to have the opportunity to enjoy a hobby or two like this one.

Happy Thanksgiving,

John

[ThomasW]

If you want to ponder box models here's some info

When the volume of the box = the summed Vas of the drivers used, the Qtc is the Qts multiplied times 1.4

At 25 times the summed total of the Vas, the Qts is only raised by a factor of 1.02, so for all intents and purposes Qts=Qtc.