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Author Topic: 2" Compression Driver and 12" Woofer Crossover Freqs  (Read 5874 times)

David Winners

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #20 on: May 03, 2018, 11:43:56 PM »

I got out of music in 2006 to play in the sandbox, and got back into the business in 2016. Shortly after I decided to buy a rig and board, I found these forums and started reading. I soon realized that the world of sound reinforcement has changed dramatically.

Things that used to be prohibitively expensive and complicated are commonplace now. Processing power is so cheap that even middle of the road gear easily outperforms more expensive gear from just a few years ago.

A big eye opener for me was tuning my new (to me) pa. I have some EV QRx 112/75 speakers. I started with an analog Furman crossover, an rta and some pink noise, just like back in the day. The results sounded ok.

Then I started reading on these forums and realized that I had missed the digital revolution. I read and read and read some more until I thought I had a good idea of what was available today.

I traded in my 24 channel analog board for an X-Air mixer, bought a cheap measurement mic, downloaded REW and started measuring stuff. Then I got a DCX2496 processor and an NU4-6000 amp (because I'm on a budget and some people here said they don't suck) so I could effect some changes in a controllable manner.

What I found out is just how little I knew about audio. Every question I answered brought 4 more questions. I'm just now, a year and a half later, starting to really understand what I can really effect with DSP and what I have to deal with acoustically (or not at all).

I strongly encourage you to dive into this project. It will be a Hell of a learning experience if you follow it through. Aligning a 4 way system (5 with subs) will prove to be a challenge at best, and impossible at likely. Off axis response with 2 dissimilar horns and compression drivers is going to be a nightmare in the crossover regions.

It really comes down to what you want. Do you want to learn something, or do you want to sound good now?

If you want to sound good now, you would do better to sell your gear and buy a single DSR112 (or other powered speaker of your choice) and save your pennies for another. It will outperform your pile of speakers in every way.
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Scott Holtzman

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #21 on: May 04, 2018, 12:40:11 AM »



I strongly encourage you to dive into this project. It will be a Hell of a learning experience if you follow it through. Aligning a 4 way system (5 with subs) will prove to be a challenge at best, and impossible at likely. Off axis response with 2 dissimilar horns and compression drivers is going to be a nightmare in the crossover regions.

That's the truth, especially if you think meausrement software is "still a thing".  You never will get these drivers to play together and more important you won't get any more output out of the system.  Other than school of hard knocks it's a fools errand.  The physics just isn't on your side.

WRT powered boxes, it's simple.  Your spare is an extra monitor for larger gigs and on other gigs it stays in the truck as a spare.

Discrete amps that are better than the ones in the speaker are thousands of dollars.  Your DSP theory is wrong too because the one in the speaker will be have complex variable level eq and compression to get the most out of the box.

You have a choice live in today or go back to the 90's.

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Chris Grimshaw

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #22 on: May 04, 2018, 03:44:41 AM »

Keep in mind that Yamaha box does not have a 2 inch throat driver with a 3 or 4 inch voice diaphragm as most of us think when we hear the term "2 inch driver".

It is a 1 inch throat driver with a 2 inch diaphragm.

I think Yamaha's description is a little marketing play on words.

This is very very important, and we're still talking like the 2" driver is a large-format one when it isn't.

There's no benefit to running a pair of 1" HF units over different frequency ranges. Pick one, use it.


I don't get why 3 crossover points makes such a difference than the usual 2 but I guess I am about to find that out.

One crossover frequency (for a 2-way cabinet) is easy - you find the range of frequencies where the dispersion angles match up, align phase and frequency response and away you go. That's a simplification, as it's rather difficult to align the phase and get the frequency response nice and flat, but you get the idea.
Two crossover frequencies isn't too bad, either - typically the crossover points are well away from each other (usually at least a decade apart), so they don't interact much - you're effectively doing a pair of two-way crossovers.
Three crossover frequencies is where it starts to get difficult, because now the passbands are close together. A classic 4-way system, Nexo Alpha, has crossover frequencies of 80Hz and 250Hz for the low-mid section. Those are close enough that the phase curve of each one interacts with the other - by changing the lower cutoff, you've got to re-work the upper crossover, and vice-versa.
That makes life hideously difficult, even with DSP. You think you've got one side right, and bam, the other end is wrong.

Can you see why we're all recommending against a four-way setup?


What you've said so far is that you're doing events for up to 150 people, and your Yamaha 15"/1" cabinets aren't doing the job. What you've done to remedy that is buy a pair of 12"/1" JBL cabinets.
If you're still planning on using any parts from the Yamaha cabs, they're still not going to do the job.

The JBL 12"s look like good units (better than the Yamaha 15"), and if the 1" HF unit included is decent, I'd use those with a subwoofer (or two) and call it good. Putting more and more crossover frequencies into your system won't get you where you want to be. Adding a subwoofer and handing bass duties to something that can actually produce bass will get you much closer to where you want to be.

From earlier in the thread,
I would like to to add just one sub in the middle, and then the yamahas would contribute low end from the sides, but be supporting the main sub in the middle. I am doing a gigs to around 150 people, which I figure I can get away with without a sub for now, and then add subs as needed.

The 15" Yamaha units aren't capable of much bass. A good modern 18" would absolutely crush them. Heck, a modern 15" would crush them. Both in terms of low-frequency extension and output.
By asking your midrange units to produce bass, you're robbing them of headroom. Midrange doesn't sound good if the driver producing it is flapping around all over the place.

You'll find the Yamaha speakers will go much louder and sound cleaner when they're not being asked to produce low end, and the same goes for the JBLs. Pick whichever sounds better, sell the others (or keep for backup/monitor use), add a good subwoofer.

You never said - what sort of amplification do you have?

Chris
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Jeff Bankston

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #23 on: May 04, 2018, 05:11:50 AM »

I cross my 12" and 2" horn at 1500hz. Any lower and its not as smooth. Any higher and it looses detail. Radian 850PB compression driver, Ciare 12" woof woof. I use Ashly 24db crossover. But thats my system, your system might not like that crossover freq.
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Ivan Beaver

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #24 on: May 04, 2018, 08:41:27 AM »

Thanks Chris, measurement software...is that still around? Allignment still a thing. I suppose I could give it a crack. I don't get why 3 crossover points makes such a difference than the usual 2 but I guess I am about to find that out.
This can be A LOT more complicated that it would appear.
First of all, if all of the drivers had a flat response,  you could simply rely on the same xover points to give a flat response.

But the drivers ARE NOT flat.  So very often the ACOUSTICAL response (and xover) is different than the ELECTRICAL xover.

In order to get it right, YOU MUST measure (and NOT using an RTA) what is going on.

Then adjust the xover points as needed to get a proper alignment.

In many/most cases, you will find that the electrical xover points are not the same.  They may be overlapping or underlapping-depending on a lot of factors.  So you may "think" there is a hole in the response, but in reality there is not-due to the response of the drivers.

This is often much easier said than done-ESPECIALLY on drivers that occupy different places in space.

Once you think you have a good alignment, then move the mic a couple of feet loser or further away and see if it still exists.

Of course there is a big difference between making it right, and simply thinking that you done a good job and letting it go.
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Luke Geis

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #25 on: May 04, 2018, 02:28:58 PM »

If you are dead set on going with a 3-4 way system I have a triplet of 4 way Ashley crossovers that may have been owned by MJ ( wink wink ) that are not only rare, but work rather well.

3 way passive systems are pretty much a way of the past unless you are getting a turnkey type system. QSC is one of the only ones I know of that will sell you a three way box and not require you to buy the needed processing or amplifiers with it. Martin, D&B, L'Acoustics etc. all require not only you to take a course or at least some training, but it must sell with the amps and processing. Why is that? Because if they didn't sell you a turn key system that was designed specifically to work as such, the end users would destroy all credibility that any company might have.

Most people do not understand the physics that go into designing even a basic PA speaker, let alone the complexities of a multi driver system. It is one thing to understand amplification and coverage angles, it is another to engineer a crossover network and speaker that in the end is not only desirable, but functional. I know enough to get me into trouble, but you won't hear me saying I can do it better than what is already out there. Go based on pay grade. If you get paid to run a system, do that, don't try and re-invent the wheel and then go putting them on cars. You get what I mean.
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Don T. Williams

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #26 on: May 04, 2018, 04:48:10 PM »

Really, you need to follow the advice of David, Scott, and others that have suggested giving up your quest to turn two "sow's ears" into a silk purse.  You will end up with an expensive burlap bag at best!  If my memory is correct, the QSC K series has over 60 channels of internal DSP filter available for the engineers to use to tune these products.  Those engineers have "tools" for their measurement and use that cost hundreds of thousand of dollars, as did their educations.  I know the same is true of JBL, Yamaha, RCF, and many other active loudspeaker manufacturers.  The modern active speaker is generations removed from what you are trying to do.
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Ivan Beaver

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #27 on: May 04, 2018, 05:02:14 PM »

Really, you need to follow the advice of David, Scott, and others that have suggested giving up your quest to turn two "sow's ears" into a silk purse.  You will end up with an expensive burlap bag at best!  If my memory is correct, the QSC K series has over 60 channels of internal DSP filter available for the engineers to use to tune these products.  Those engineers have "tools" for their measurement and use that cost hundreds of thousand of dollars, as did their educations.  I know the same is true of JBL, Yamaha, RCF, and many other active loudspeaker manufacturers.  The modern active speaker is generations removed from what you are trying to do.
But a free RTA app using the internal mic and a 1/3rd oct eq should do the trick-------
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Stephen Kirby

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #28 on: May 04, 2018, 05:44:18 PM »

Here's an idea using what he's got.  Put the JBL 12s up on sticks and the Yamaha's on the floor as aux fed subs with an elemental analog crossover and hopefully some sort of HP.  The horns should be left in as the hole they'd leave would affect the cabinet tuning.  The Yammies aren't going to produce any real bass but they will add a bit of thump to the kick drum at 80-100 that wouldn't be there with speakers up in the air.  By not asking the 12s to produce any bottom, they should have a bit more clarity.  That is about as loud as this pile-o-boxes will go.  Any louder would be a complete modern system up to the task.
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Dave Garoutte

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #29 on: May 04, 2018, 07:22:53 PM »

But a free RTA app using the internal mic and a 1/3rd oct eq should do the trick-------

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Re: 2" Compression Driver and 12" Woofer Crossover Freqs
« Reply #29 on: May 04, 2018, 07:22:53 PM »


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