Super Subs

[frederic]

Greetings old friends and new friends...

Some of you may remember me from the Tascam BBS, then the homerecording that David runs, now we have a new BBS to yap on Thanks for the invite John, things are looking good around here.

Anyway, John specifically invited me because I was asking stupid questions about hiding my subwoofer. Long story short...

I have four options. Keep the 15" subwoofer I have now, and be irritated that its in the way all the time (its big).

I can cut a cove in the center of the wall behind the console table, and shove it in possibly with some acoustical treatments.

I could use the entire crawl space as a subwoofer cabinet (which would require a different subwoofer, which is okay).

Or maybe I could soffit mount the subwoofer in the wall, facing my shins.

Just curious what some of you would do. I could take the easy way out and pick up two smaller sub and not deal with it.

What do you all think?

Thanks again for the invite John!

[John Sayers]

welcome mate - good to see you here as you can help contribute to the replies :)

I'll wait with you to see what Barefoot has to say in this, he's da man on speakers

cheers
john

[frederic]

welcome mate - good to see you here as you can help contribute to the replies :)

People would want my advice? Thats a new one. heh-heh.

I'll wait with you to see what Barefoot has to say in this, he's da man on speakers

He can take his time, I'm nowhere near closing up that wall. In fact, nowhere near closing up any walls. LOL.

Today was productive The Home Depot truck delivered late afternoon, I covered everything with tarps, I framed out the flourescent light, paying attention to things being level, then cut 22 58" stringers

Hey, it was something to do!

[Velvet Elvis]

frederic....

That's funny... I got done just a week or two ago putting in 23 stringers of my own (though they weren't for structural integrity... they were just to square off a ceiling in my loft so that I could put in recessed lighting).

What a pain.

btw - I'd be happy to 'store' your extra subwoofer for you once you build your new one

Velvet Elvis

[frederic]

That's funny... I got done just a week or two ago putting in 23 stringers of my own (though they weren't for structural integrity... they

I hear ya... I wasn't sure if I need these for structural purposes or not, but I decided it would really suck to find out AFTER I build everything out, install gear, and have a client over. Because you know thats when things would let go

This place is so discombopulated... walls with no joists above them, corners that aren't completely studded, just a lot of weird stuff that I didn't realize was there until I tore the insulation out.

And if I find one more structural piece nailed in with finishing nails I'm going to scream obscenities at my cats. When I pulled off the cedar paneling, the side window came with it. WTF is that?

Anyway, I wasn't going to do stringers, but if I screw the plywood directly to the joists, I section off the front, 30 degree slant, and the back 7 degree slant since there is a 90 degree joist going the width of the peak. Since I didn't have the courage to do a ridge vent, I've opted to suffer with a 8' ceiling that will give me 4" of space between the rafters and the stringers, plus the airspace between the joists, which will allow airflow from the soffits front and back up to the peak, then across the peak to the exhaust fan i have to install.

Finding a 12" exhaust fan was a real pain, I have to say.

btw - I'd be happy to 'store' your extra subwoofer for you once you build your new one

Um, sure! [/quote]

[barefoot]

frederic, great to see you here!

First of all, let me say I am 100% pro soffit mounting. If you can soffit mount your subs, that's great. Preferably you should mount them as much towards the vertical center as possible - and as close to the monitors as possible. Moving subs away from the wall and floor intersections will help reduce their excitation of room modes. Actually, slightly off center is best, say 3/5 the way from the floor to the ceiling.

Let me also say, however, that I am rather anti "off the shelf" subs. Subs and monitors should be specifically engineered to integrate with one another. Anything else is a roll of the dice that will likely not come up in your favor. The best you can do in this case is ensure that the subs and monitors have flat pass bands that overlap by a minimum of 1.5 octaves on either side of the crossover point. Sadly, this is not the case with most implementations.

And two subs are better than one. Subs are typically over taxed and create a lot of distortion. The more amps and surface area you have sharing the load the better. Also having two subs allows you to mount them off center horizontally as well, and closer to the monitors presenting less of a time misalignment issue.

Thomas

[frederic]

frederic, great to see you here!

Thanks, great to be here.

First of all, let me say I am 100% pro soffit mounting. If you can soffit mount your subs, that's great. Preferably you should mount them

The wall my console table will be facing (i.e., the back of the monitors will be facing) is the slanted ceiling wall, so the wall is 13 feet wide and about 36" high. I lose 3.75" of that due to headers and footers of that wall. So, thats 32.25 inches worth of usable space. The 15" sub I have will fit, but only if I downfire the sub at the floor. If I face it forward I have to turn it and cut out studs (which are support studs, unfortunately).

I could use smaller subs, thats not a problem at all, say two eights. Amps I got, no biggie.

as much towards the vertical center as possible - and as close to the monitors as possible. Moving subs away from the wall and floor intersections will help reduce their excitation of room modes. Actually, slightly off center is best, say 3/5 the way from the floor to the ceiling.

Got it. 3/5. Would that still apply with a wierd wall like mine? Do I face them down with coves underneath them? Or, face them forward at my knees (rather than my shins)?

Anything else is a roll of the dice that will likely not come up in your favor. The best you can do in this case is ensure that the subs and monitors have flat pass bands that overlap by a minimum of 1.5 octaves on either side of the crossover point. Sadly, this is not the case with most implementations.

With the electronics I have, I can control the volume applied to the subs, as well as the crossover point left and right (or combined if one dual coil sub), and if its a matter of tuning with an RTA I'm happy to do that. My monitors are not exactly the best monitors in the world (Aiwa Home Theater double woofer with all three drivers replaced with vifa components) but I'm used to them.

And two subs are better than one. Subs are typically over taxed and create a lot of distortion. The more amps and surface area you have sharing the load the better. Also having two subs allows you to mount them off center horizontally as well, and closer to the monitors presenting less of a time misalignment issue.

I can do this.

Though, my monitors (whether my hybrids, my event 20/20's, or possibly behringer truths down the road) are not soffit mounted and never will be, because of the ceiling slant. i have to have them about four feet from the wall minimum to clear the ceiling and leave some "air" behind them.

The subs would then be 4' behind them. I presume thats not terribly ideal, aye? heh-heh

thanks for the comments!

[frederic]

While taking down 2x4's out of the attic, I found two 8" subs of unknown manufacturer. Both work, I hooked them up quickly, so I may take a wild leap and soffet these into the short wall.

I did use these in my studio at one point, but honestly, I can't remember when.

I wonder who made them.

[John Sayers]

I saw these subs at that Angel Mountain studio posted at HR

http://www.pilchner-schoustal.com/am/

look where they put their sub

cheers
john

[frederic]

I saw these subs at that Angel Mountain studio posted at HR

http://www.pilchner-schoustal.com/am/

look where they put their sub

cheers
john

I did, thank you

[knightfly]

Hey, Thomas - you lucky guy, you get to 'splain yet another mis-conception away for me -

"The best you can do in this case is ensure that the subs and monitors have flat pass bands that overlap by a minimum of 1.5 octaves on either side of the crossover point." -

I was under the impression that you wanted a steep filter slope between sub and mains so the two wouldn't try to reproduce the same info out of phase (probably) , and have been using a Yamaha dual 8" sub with 24 dB filter in conjunction with a pair of KRK K-ROK's for some time now - the combo sounds really good to me, no holes or lumps I notice - in fact, several people have asked me how I get those little speakers to go so low (the sub is behind the mix desk on the floor) - point is, it just sounds like one continuous system down to the bottom.

I've not actually gotten into things with a scope to see what stops where, could it be that I just lucked out? Why the 3 octave overlap?

Thanks for any enlightenment you can provide here... Steve

[frederic]

I was under the impression that you wanted a steep filter slope between sub and mains so the two wouldn't try to reproduce the same info out of phase (probably) , and have been using a Yamaha dual 8" sub with 24 dB filter in conjunction with a pair of KRK K-ROK's for some time now - the combo sounds really good to me, no holes or lumps I notice - in fact, several people have asked me how I get those little speakers to go so low (the sub is behind the mix desk on the floor) - point is, it just sounds like one continuous system down to the bottom.

That was my perception as well, you want steep rolloff at the sub at the top of its range, and steel roll off at the bottom of the monitors.

This is one useful thing about behringer - I use a few ultra-curve pros, where I can effectively block frequencies above and below a certain point on the EQ for the sub, and using another EQ pass above that same frequency for the monitors. Because they are digital, I can make the rolloff as steep, or casual as I want. I have a pair of old peavey crossovers too, but they are all analog and rather noisy. probably late 80's vintage stuff. I like the behringer's because they take digital out, and convert it to analog just before the amps. Made wiring easy

Anyway, I could be totally doing this wrong, of course, but I had the same perception as you.

[knightfly]

Yeah, Frederic, I've believed most of my life the old standby quote "if it sounds good, it IS good"... (of course, that's assuming that you've not finished destroying your ears yet... sigh) Steve

[barefoot]

Steve,

Sorry it took so long to reply. I was on "vacation". (actually spent my whole vacation working on my speaker business)

Anyhow, attached is a quick simulation of a rather best case example of using a generic crossover. The red curve is an extremely nice sub response extending from 20Hz up to 300Hz. The blue curve is a monitor that is flat down to 40Hz. The faint blue and red curves represent a 4th-order Linkwitz-Riley crossover at 80Hz. The green curve is the summed response.

Notice the -1.5dB dip in the summed response. Not terrible, but take a look at the response curves you're starting out with. They're about as nice as you could hope for. You'd be extremely lucky to have things work out so nicely.

The response of the sub and monitor are basically those of high and low pass filters. The phase response is not flat in the regions above and below the speakers cutoff frequencies. So you can't count on a flat summed response using a generic crossover unless the responses of both speakers extend well above and below the crossover region.

On the other hand, as long as there is sufficient overlap a custom crossover can almost always be designed to yield a flat summed response.

Thomas

[knightfly]

Thomas, thanks for that - I hope your "vacation" time was productive...

The Yamaha sub I've been using has a 4th Order filter, but I doubt the K-ROK's are nearly that flat - it took a while, but I eventually found settings for Xover freq and sub level that work as well as I could have asked for. My final criteria is that you don't know the sub is on til you turn it off... Steve