Building a superior 2x10 cab

[Arjank]

Today (or tomorrow) I get the Oberton 8NCX coax driver
Saturday I'm gonna put it in a testbaffle and measure it to see how the mid/highs are behaving. I hope it will give a uniform off-axis response (power response).

 

[Arjank]

Just got the driver, it's to pretty to put inside a box....

 

[Sundogue]

Just got the driver, it's to pretty to put inside a box....

That looks great. I'd like to see how it performs for you.

I'm thinking of a fEarful build and just wondering how that speaker would match with a 3015LF.

I agree...almost looks too nice to cover up with a cab.

 

[L21B32G]

I'm really interested in how your design turns out Arjank.

I just bought a pair of Radian 5312 coaxials along with passive crossover networks that I got for a great price. http://www.usspeaker.com/radian 5312-1.htm

I know they are heavy speakers but I was planning on trying them along with an Eminence 3015LF as a dedicated subwoofer. I would use an active crossover between the 15 and 12. This would be my "large" rig.

It seems to me an eight inch coaxial would be better in terms of size/weight and possible upper frequency fidelity.

Do you think it would be worth giving it a shot with the Radian?

 

[Arjank]

I'm thinking of a fEarful build and just wondering how that speaker would match with a 3015LF.

If it will match with the two 10" woofers then it will probably also match with the 3015LF. The sensitivity will be aprox. the same. The 8NCX (or any other good 8"coax) could be the next step in the fEarful series, but thats not up to me to say.

 

[Arjank]

Do you think it would be worth giving it a shot with the Radian?

I think your plan might work very good, you may not have the smooth mids of the 8" but the lower mids will be very punchy. It also depends on the crossover design. An active crossover would be the key in your setup. I would go for a pretty low crossover between the 12 and the 15 e.g. 150hz.

 

[greenboy]

There are reasons why coax drivers haven't gained much traction in the SR sector, and they are largely the same reasons I didn't run with them for bass guitar. They were on my radar (and that of Alex of barefaced bass) some time before the first dedicated mid designs got finalized.

In most coax designs the transition between the driver aperture and the horn mouth is rather flawed (because of the extra piggybacking distance) and that leads to some non-pleasing distortion. Next, to make a coax work, one has to either disturb the midwoofer's dispersion with diffraction artifacts and disturbance off the backside of whatever central-appended HF waveguide/horn - or one has to use the midwoofer cone as the HF waveguide. Which is flawed in geometry & transition. That's partly why those directivity plots are funky though they just are a symptom.

It's all tradeoffs. But with a well-chosen non-coax waveguide at the same crossover point you can exhibit much smoother polars/directivity plots. As much as I loved coaxes, And so did Alex, we both decided the trade-offs didn't match up for us.

But. Also, as a fan of copious overdrive and distortion I didn't especially want to be running on a compression driver in the midrange or lower treble, because to get that beautiful tonal beast happening even nearly nice as a well-chosen mid driver allows, well, that would require a lot of passive filter work and still comes up a bit short.

I am going to pay attention to those drivers though.

 

[Arjank]

I'm fully aware of the drawbacks of a coax driver. But, in a good coax driver all parts "fit" to a certain degree. The Oberton coax driver is very well designed to minimize some of the points you mentioned. One other example of a great coax driver is the one from Thiel(hifi).
With a well designed crossover (and the 8NCX) I will have less phase problems and a more uniform radiation pattern then a "regular" three way design. I really think it would be a step forward instead of a step back to use the 8NCX.

But with a well-chosen non-coax waveguide at the same crossover point you can exhibit much smoother polars/directivity plots.

To crossover at 500hz with a waveguide/horn I will need the BMS 4590(2"/ 1" coax driver) in a rather large Tractrixhorn. This will sound very good, but is far from practical. Thats why I choose the 8" coax.

 

[greenboy]

In this century I wouldn't be worried too much about improvements - and then present Tractrix in the same breath ; }

Please, feel free to pursue your goal. I have already pursued mine. I chose the set of trade-offs that I knew I could leverage best for the intended result. It works like gangbusters.

If I were to design an ADDITIONAL series for bass guitar rest assured I'd know what I'd want to do, without any public advice, or the need for design by committee.

 

[Arjank]

If I were to design an ADDITIONAL series for bass guitar rest assured I'd know what I'd want to do, without any public advice, or the need for design by committee.

I don't want to step on your toes. Like I said earlier, it's not up to me to say to use a coax for the fEarfull.
I only share my thoughts which are based on my own experience. You have yours, and that's good. It would not be good if all designers would think the same way. If that would be the case there will never be any improvement.....
That I choose the coax was due to the comments from other people in this thread. They made me think ten times.......

In this century I wouldn't be worried too much about improvements - and then present Tractrix in the same breath ; }

I strongly believe in my design and for me it has the least set of trade-offs for getting the studio sound on stage.
As far as horns go, the Tractrix function just has the least artifacts sound wise and it has the most uniform radiation pattern.

 

[greenboy]

As far as horns go, the Tractrix function just has the least artifacts sound wise and it has the most uniform radiation pattern.

I won't argue about this because it's so evident that the SR world disagreed ages ago, and the home enthusiasts are largely pursuing Constant Directivity too. But it wouldn't hurt to read up a little. At [Invalid or Expired Link Removed] these are pertinent:

Wayne Parham / Pi Speakers High-Fidelity Uniform-Directivity Loudspeakers pdf

Quadratic-Throat Waveguide - a prominent engineer at Peavey outlines history & milestones of horn development

Progressive Transition (PT) Waveguides - JBL tech article with text, photos & graphs

 

[Arjank]

In the german magazines Klang&Ton and HobbyHifi, they have used lots of different types of horns in the past. But as far as I have read (and seen in the graphs) the directivity of a (round)tractrixhorn is more uniform. In german they also call it "kugelwellenhorn".
The only drawback of a tractrix is it's size.
And one of the other reasons I think that the SR doesn't want these horn is that they want great dispersion in the horizontal plane and narrow in the vertical plane. A round tractrixhorn does not do that.

Btw. I did use a fEarfull kind of design 15 years ago . Two cabs with each a 15"woofer and a 5.5" fullrange driver. That was in the days that I played in a Primus coverband I blew one 5.5" driver on a gig when I hit a few harmonics with the distortion on and wanked the tremelo, hahaha.

 

[greenboy]

And one of the other reasons I think that the SR doesn't want these horn is that they want great dispersion in the horizontal plane and narrow in the vertical plane. A round tractrixhorn does not do that.

If it ever becomes fashionable for rooms to be taller than they are wide and deep, CD will be able to competently address THAT too ; }

Btw. I did use a fEarfull kind of design 15 years ago . Two cabs with each a 15"woofer and a 5.5" fullrange driver. That was in the days that I played in a Primus coverband I blew one 5.5" driver on a gig when I hit a few harmonics with the distortion on and wanked the tremelo, hahaha.

Must have been a bad design for that type of use. On the other hand, running lower-rated compression drivers very far down in an instrument rig really limits things when heavy distortion/fuzz is stomped in. And it really sounds like azz unless one does a ridiculous amount of filtering. Too many passive components, no thanks.

 

[Arjank]

Must have been a bad design for that type of use. On the other hand, running lower-rated compression drivers very far down in an instrument rig really limits things when heavy distortion/fuzz is stomped in. And it really sounds like azz unless one does a ridiculous amount of filtering. Too many passive components, no thanks.

The design was not bad for that use, the driver just could not handle it.
I never used a compression driver when I used distortion/fuzz or whatever.
And what is it you saying that it will sound like a.. if you don't use a ridiculous amount of filtering?
And whats wrong with many passive components when used the right way?
I might use some extra components but they are just to straighten the impedance of the drivers near the Fs, else the actual filter will not work correctly. If you don't do this it will give (phase)problems at the crossover points. The response may look great on-axis, but off-axis it will look like s...

Seems like you don't like what I write......

 

[greenboy]

Hey Arjank,

I gave you input and you expressly asked for it. I however, was not asking for input on how to "take the fEARful forward". It already is forward. It doesn't need to go anywhere. Nevertheless I shared why I made some of the choices I did and why they work better for my design goals. I could tell you more but I see now that you would just consider it something to debate about.

So follow your own muse, as was succinctly put to you earlier in the thread by someone I could talk to all day long and never feel put upon. He and I somehow manage to discuss this stuff from our own unique perspectives, and take and use information from each other without ever feeling any friction. We can do it differently but still appreciate each others' insights and experience. It's a kind of give and take that you and I perhaps have a personality or language barrier that's in the way.

EDIT: Do realize I think that driver is pretty cool. And that it merits consideration. But like anything it is a set of compromises, and not necessarily a game changer.

 

[Arjank]

I however, was not asking for input on how to "take the fEARful forward".

It was never my intention to do that, Sundogue came with the idea matching the coax with a 3015 and so the link to the fEarfull was made.

someone I could talk to all day long and never feel put upon. He and I somehow manage to discuss this stuff from our own unique perspectives, and take and use information from each other without ever feeling any friction. We can do it differently but still appreciate each others' insights and experience. It's a kind of give and take that you and I perhaps have a personality or language barrier that's in the way.

Thats exactly the same thing I want, discuss it from our own unique perspectives and appreciate each others insights. If you read this thread you can read that I appreciate all the comments that people give. This is what made me think about my design more thoroughly.

but like anything it is a set of compromises, and not necessarily a game changer.

+1

I hope we can continue this thread and keep things positive.

The next step in my 2x10 cab will be building the cabinet and measuring the frequency response off all three drivers. I'll post the measurements and then we can discuss about the best crossover points for this design.
I will measure the coax on-axis and 15 and 30 degrees off-axis.

Btw. I just played some music over the tweeter part of the coax. By ear it sounded very promising, the dispersion is also pretty good.

 

[greenboy]

From my perspective for bass guitar, I'd want those two major pinches below 3K minimized. I've seen far better done with discrete drivers. The minor one at around 10K, not necessarily as important for the application, and it's actually better off-axis than on.

 

[greenboy]

I will measure the coax on-axis and 15 and 30 degrees off-axis.

What gear and procedure are you using for measurement?

 

[Arjank]

That directivity sonogram from Oberton doesn't say anything to me. It does not mention how the drivers are filtered. So I don't give any comments on that.

I use MLS to get the impulse response and I use a calibrated mic with a bandwidth of 20-21.000hz. With my measurement setup I can check the frequency response, decay and impedance.
I once did a comparison between my setup and the one used by one of the German magazines (they use a B&K mic). I measured the same tweeter and my results were exactly the same. Only the decay diagram looked a bit more rugged above 10khz, anomaly of the mic.

 

[Sundogue]

Sorry guys...didn't mean to put the idea of fEarful out there and cause such a fuss.

I was just thinking out loud. I know nothing of the positives or negatives of using the coax. It simply looked interesting in some kind of simpler three way, kind of way..

For what it's worth there aren't a whole lot of commercial 210's that I care for much and it wouldn't take a whole lot to make a superior one.