Double bass bin La Scala

[NightVtwin]

I picked up 2 sets of La Scala's on ebay with the intention of setting up left, right, & center channels in my basement theater, and then relisting the remaining speaker. As an experiment I set up all four in my living room, and all I can say is WOW! There seems to be a coupling affect which has significantly improved bass response.

The cabinets are rough, so my thought is to reinforce and refinish the cabinets and stack two base bins with the mid and high horns on top in a seperate cabinet that can be aimed. The sides, top, and back would be laminated with 3/4" particle board using epoxy and screws, and finished with maple veneer and trim.

One set of speakers is a mid 80's industrial model, the other set are the ones Jay L had listed for sale and features his rebuilt crossovers.

My question is, what would be the best way to hook up the second woofer to the crossover - series, parallel, or perhaps a redesigned crossover?

Thanks in advance for any advice.

[mas]

Just an idea...

You might consider stacking the bass bin 'on top', depending on your listening position to bring you a bit more 'on axis' with the mid and high frequency horns. The LF bins will still couple.

If you are looking to redo the crossovers, it might be worth it to look at the Behringer DCX-2496 for an economical active crossover with signal delay/alignment available for $250.

[IndyKlipschFan]

Keep the bottoms as is../ One on top of one another.. Like your first picture...

Then take the tops.. on top of those, but flip the 2nd top one upside down so the tweeters are in the middle..

Then get back to us, after you wipe that childish grin off of your face too! haha Your gonna love it!

BTW, for what it is worth... This is my rear surround setup in my 9.1 HT too. hehehehehehe IT ROCKS!

[IndyKlipschFan]

My question is, what would be the best way to hook up the second woofer to the crossover - series, parallel, or perhaps a redesigned crossover?

Some of that depends on your amp and what load can it handle?

Kinda like in this pic but with the bottoms as is and the tops flipped was the idea...

[mas]

If you are combining MF & HF horns as well, you would want to do this.

But be aware, in a small space where your distance is less than ~10 unit lengths away, they are not going to be perceived as fully coupling, but rather as separate sources with associate comb filtering and polar lobing anomalies. Thus this technique is best for larger venues.

In all cases, the polar response will benefit due to vertical stacking as opposed to a horizontal coupling.

Exactly what are you trying to accomplish? Additional gain??? [:|]

[]

[IndyKlipschFan]

Mass..... help me out and post a pic with the top like you NOW have... on top of the two bass bins..

Part of "the secret" IMO of the K horn is getting that High end up in the air OFF OF THE FLOOR.. It just fills the room sooo wonderfully!

The bottoms are not too tall to do this stacked.. or if you like put both bottoms on the floor and the High Ends in the middle of them too.

Again experiement and see. Anyway, I think you will find the High Ends flipped on each other will really help you.

[Guest " "]

NightVtwin

"My question is, what would be the best way to hook up the second woofer to the crossover - series, parallel, or perhaps a redesigned crossover? "

The best way would be to get your hands on 2 Atlas AF-140's or 2 Crown CT-170's autoformers and use these connected between your woofers and crossover. If you put the woofers in parallel with out autoformers your impedance will drop to 1.8 ohms. However, with the autoformers, you can use a 2X impedance multiplication factor and bring the impedance back to 3.9 ohms of the K-33/K-43. The autoformers have an insertion loss of .6 db and a frequency response of 30hz - 15khz.

[JohnA]

La Scalas have a small mouth for the horn. Side-by-side will
let the bass horns work better together. The mouths will "couple"
and the bass will be a bit deeper. Run them in parallel and build
a new crossover network to use one HF section. It will have
plenty of output. Calculate your woofer as 3 ohms for the
crossover at 400 Hz, put a bandpass on the squawker, without the
autoformer (T2) and build a 4th order Butterworth high pass for the
tweeter at 5000 Hz, use 8 ohms for the tweeter. The tweeter
should also have a poly switch amd resistor or the Type AA diodes as
protection. Indoors, the tweeter will be hot enough; it will be
only 2 dB down from the rest, anout like the stock Type AA.

Do this and they will ROCK!

[freddyi]

bet all four side by side would be fun for mono

[PositivAttitude]

I'm reading these posts and find that you guys are really amazing. The ideas and knowledge that you offer to others is ALOT....[Y] Paul

[ajsons]

mas, those are great ideas.

be careful with what you post on this forum though. someone has been stealing ideas from forum members, and applying for patents for them, and the man is very good.... a very good THIEF that is..a real pro.

[WMcD]

If I was in your situation . . . which I am not. Try a no cost experiment first.

I would follow mas's suggestion as a starting point, tweeter to tweeter. That is getting close to an MTM system which has theoretical merit of the pattern in the crossover region. And as he says, building a vertical stack will narrow the vertical pattern . . . in theory.

I see that John A is talking about keeping the bass bins close together to increase mutual coupling of the bass mouths. But I think there are a few other considerations. Even if stacked, the bass bins are still fairly close when stacked in terms of wavelenght. Also, the upper bass bin is indeed getting farther from the floor . . . but it is getting closer to the ceiling. Maybe that helps a bit.

I would put like units in a given stack because I believe this is the critical acoustic alignment.

Also, I would just wire the inputs to each in the stack in series, observing red to black polarity. As mentioned by others, a parallel load on the amp is just too much unless you've got an amp with a 2 ohm output impedance (some apparently do). [Edit: Here I mean the regular input to the crossover. The internal crossovers are used.]

On this subject of series. There was a link to a website posted by a good person here. The website argued that damping of the system, in view of the "back emf" is ruined by the series circuit. I believe that is incorrect as long as the two units have substantial the same impedance variations over frequency.

The argument there was that the in the parallel circuit, the emf is dumped into the near zero output impedance of the amp. (This I agree with.) When the amp is putting out zero volts, both the hot (plus) and ground (minus)output of the amp is at ground (assuming zero output impedance of the amp).

There is sort of a implied argument in the article that in the series connection, each speaker "sees" the impedance of the other speaker for purposes of dumping the emf.

(+ amp) -- (+speaker1 -) - - (series junction) -- (+speaker2 -) -- (-amp)

In my view, the reverse emf of speaker 1 is trying to drive the junction to a positive voltage. But the reverse emf of speaker 2 is trying to drive the junction to a negative voltage. Therefore, the junction voltage is zero. That creates a virtual ground at the junction. Therefore, each speaker "sees" whatever the output impedance of the amp might be.

In any event, the stacking and series is a no cost experiment.

Maybe there is some concern the amp will not perform well with the doubled impedance of the midrange (because of the series circuit) where the autotransformer in the LS is already making it somewhat high. But this combined series impedence is no higher than a CW or Heresy. No one worries about that. One of PWK's DfH shows that the increased impedance of the Heresy makes for less amp distortion. No one worries about H's.

Gil

[Marvel]

This is reminding me of some of DJK's earlier constructions. Dennis had built a ton of the LS bass bins, which made it easy to stack and combine. The best would probably be four of the bins on each side, in a 2 x 2 configuration. That would make for a huge sound, but also take up a lot of space. You guys with all of the Industrial LS could do this pretty easily.

It's all easy for me to say since I don't have them here to shift around. [*-)]

Bruce

[michael hurd]

Could also do the horn flex mod and add ports to increase the low bass output of these.... there are two ways of doing this, depends on which ones you have, the industrials or the home version. DJK laid it all out in what you need to do, either on here or the audio asylum website.

[DrWho]

Electrically speaking, you can't just wire in a second bass bin, in series or in parallel because it moves the effective crossover point for the bass bin. It's not quite a doubling or halving of the crossover point because the values of the caps and inductors need to shift in opposite directions. What you end up with is a wierd slope and about half an octave difference in the crossover point. I think it sounds better in parallel as long as your amp can drive it (which most pro amps can do).

All that to say, the best approach would be to rebuild the crossover if you're set on doing this crazy configuration. You should be able to salvage a lot of parts in the old crossovers and purchasing transformers is most certainly not an approach I would consider...

I would go ahead and wire in parallel and take advantage of the 6dB increase in sensitivity, which will allow you to run less attenuation on the squawker and tweeter. In fact, you might even need to bring down the output of the bass bin since the K77 tweeter won't be able to keep up. Nevertheless, you should be able to find a configuration that maintains the same effective crossover points.

But by the time you've got a properly implemented passive, it will probably cost about the same as moving to an active crossover. Or you could take it to the next level and go with a digital active crossover and implement time-alignment like MAS mentioned. There are all sorts of advantage to this, but of course it comes with an even bigger price tag. But if you've got a double stack of lascalas in your living room, then you must be crazy enough to go all the way []

As far as the acoustical issues....I've found that the lascala bass bins sound better when stacked on top of each other. The MTM alignment is cool and all, but I think the extra coupling associated with having them so close to each other outweighs the other issues. But maybe that's cuz I've only heard them wired in parallel in that configuration without corrections to the crossover? It's free to try any configuration you like (until you throw out your back), so you might as well just try a few ideas and see which your ears enjoy the most.

[WMcD]

I edited my post to make it more clear I was talking about wiring the inputs to the crossovers in series.

Of course I agree with Mike B. about the need for a new crossover if the woofers are in series (and double the resistance). Lets assume you have a simple first order (6dB per octave) crossover with just an inductor (L). When you put the drivers in series you will need an inductor of twice the value to maintain the crossover point.

But, let's look at the series circuit which I suggest, just showing the woofer region:

(+) - - - L1- - - - Driver 1 - - - -(-)(+) - - - - L2 - - - - Driver2 - - - - (-)

Here we wind up with two inductors (L1 and L2) in series. Inductors in series add. (This is similar to caps in parallel adding).

Funny thing when you put the drive units in parallel: Now the total woofers half in impedance and you need an inductor L of half the value. Two equal inductors in parallel give half the individual inductance.

Consider the circuit below, in which I'm trying to show the parallel wiring at the inputs to the crossover terminals. The terminals are (+) and (-).

The points "*" will always be at the same voltage. So that is the same as if a wire connected them. If you imagine that wire to be there, we see that we do have drivers in parallel and inductors in parallel.

(+) - - - L1 - -*- - Driver 1 - - - (-)

(+) - - - L2- -*- - Driver 2 - - -(-)

Gil

[Guest " "]

" I would go ahead and wire in parallel and take advantage of the 6dB increase in sensitivity"

Assuming the amp can handle a 1.9 ohm impedance load......else.....4th of july will come early.

[Guest " "]

Here you go.

Connect the woofers in parallel and run the connection to taps 4 and 2 of the atlas af-140 autoformer.

Next connect the crossover connection for the woofer to taps 4 and 3 of the  af-140 autoformer.

The af-140 will apply a 1.96 impedance multiplication factor to the 2 k-33's in parallel, which will bring the impedance back to that of a single k-33.

The insertion loss is only .6db.  The autoformer has a frequency response of 30hz - 15khz, and can handle 150 watts continuos.

The autoformers can be purchased ofr 50 bucks each.

You need one for each woofer pair.

SL1.1450.pdf

[DrWho]

You know Gil....that's a great point, sorry I missed it.

If you've got two complete sets of lascalas, you can use the two crossovers you already have to balance things out perfectly. Wire the two crossovers in series, connect one of the crossovers to the LF,MF,HF drivers just like normal, and then connect the LF section of the second crossover to the second bass bin. The series wiring will offset the 3dB gain you have by doubling up on drivers. For experimental purposes this is absolutely the best way to go. In fact, it wouldn't take much to build the two crossovers together in much the same way if you wanted this to be a more permanent solution.

Tis a much better approach than trying to throw autoformers at everything...[^o)]

[Guest " "]

"Tis a much better approach than trying to throw autoformers at everything"

If your amp can handle a 1.8 ohm load then you don't need the autoformers.

If your amp can not, do as the big boys have been doing for 40 years, and use things like autoformers and line transformers to solve these common senerios.

I posted the tech data, it's pretty easy to follow.

Putting two crossovers in series or putting two crossovers in parallel does not address the impedance issues.

After you smoke a few amps.....you will understand what i mean.

At least no one will be able to say  "I did what speakerfritz said, and I smoked my amp".

and about this

"If you've got two complete sets of lascalas, you can use the two crossovers you already have to balance things out perfectly. Wire the two crossovers in series, connect one of the crossovers to the LF,MF,HF drivers just like normal, and then connect the LF section of the second crossover to the second bass bin."

What a mess....have you every built a crossover......your going to reduce the capacitance by running the xovers in series with the same load (1/2)....your going to double  inductance by running the xovers in series with the same load (2X), a frequecny shift night mare, and you still would not have addressed the impedance issue in the LF section.

The autoformer is the standard soultion for impedance matching.....the fundamental issue here is the impedance change of adding a second woofer......very simple and straght forward.