Css trio 12 loaded horn

[mwmkravchenko]

Who needs excuses, your experimenting!

[Oscillate]

Mark ...which (rack mount) power amplifier would you suggest for the Trio12 horn?

"The Fs is at 18 hz and the F3 is 16 hz." & "Hornresp gives peaking at 200 watts and 125 db..."

Obviously nothing with a built-in low frequency boost / LT circut. Also wondering at
what Hz most power amplifiers set their high-pass filter? Would something like these
two be apprpriate?

Behringer NU1000
Crown XLS 1000

[mwmkravchenko]

This is a bit on the picky side but I'll say it anyway.

Neither of these has any great sound quality.

But for low end use they will be able to pour in the power.

Most amps have an F3 or the point where they drop to half power (-3db) lower than you will find on almost any recording. So that is generally not an issue.

Anything with a low end boost can possibly cause you problems. I say possibly because it depends on the boost level. A horn does not like being driven lower than it is designed for. But this horn is very happy very low. So with some care you could get away with some low end EQ if you ever felt the need. Beats me when you could use it.

Mark

Mark

[mwmkravchenko]

Attachment 33889I have been asked a few times what this sub will do with one hundred watts.

Here is a nice graph for you guys to look at. The bottom line is one watt the top one is one hundred watts. It is calculated with the mouth close to a corner. In hornresp I consider the 1Pi setting to be closest to a real life corner in most homes. Unless you are in a basement where you can strap on an extra 3 db on the figures.



The graph below is the same driver in a conventional sealed box tuned to 16 hz fed one hundred watts.

Attachment 33889

Just a little bit of difference. By the way every ten db difference means it sounds twice as loud as the level ten db below.

Mark

[mwmkravchenko]

The other question I get most is what about the roller coaster response on the low end?

I hate to be the guy to tell you but the nice graphs that your favorite software shows you on the screen is not what you listen to in your room. The horns are actually flatter in room than almost all conventional sub boxes. The ripple shown is real and there in use. But it is actually not very large peak to peak. Plus or minus 2 db most of the time. In terms of actual audibility it is not a true issue.

Mark

[top_down]

Hi Mark,

You've answered some of my questions here already (thank you) so I'm going to revise my list of questions a bit!

1. Is Audyssey MultiEQXT sufficient to take care of any eq that is required or is something like a miniDSP or Behringer PEQ going to be required?

I'm sure a lot of guys like me have 300w or 500w plate amps that can be repurposed for this (a pro amp seems like total overkill now!), so I'm going to dig a little deeper on the boost question:

2. Is a HPF a requirement to protect the driver? What frequency is best?

3. Is the Sallen Key filter available on most plate amps adequate if the boost is limited with a resistor change? If so, which would be better: 1db of boost or is a little more helpful? At 1dB I think 13.9hz or 18.7hz are the choices. At 2db of boost we have 16.2hz. I'm looking at an Oaudio chart but the PE/CSS charts should be similar if not identical.

I can model all these filter choices in WinISD and know what to expect on a ported sub but on a horn I wouldn't know where to start. If a HPF is a requirement for this horn then most plate amps are going to provide that with at least 1db of boost thrown in even after a resistor change. It would sure be nice to see what 1 or 2db of boost per the plate amp resistor charts would do to the horn's response. (hint, hint - please publish a response curve with a BASH amp with 1db of boost (or whatever works best))

4. I'm thinking of building this thing as sort of a long and low media console (16.5" high) and set my TV, receiver and DVD player on top of it. I've got 102.5" between the mains so it does fit. But setting stuff on top... would it just shake the ____ out of all the electronics? You guys were laying on it, what did it feel like when it was running 115dB?

5. Should I point the horn out towards the room or to the left towards the left wall like your prototype?

6. Can I put a grille over the outlet? Could I do perforated metal to match a Martin Logan ESL panel or just grille cloth?


Thanks!!!

[mwmkravchenko]

Questions and answers:

1. First listen to this monster and tell me if you need EQ. It was designed to work in tandem with the mythical every room gain. It is true that there is structurally reinforced reflections that tend to show up as greater loudness in a given room. It is also true that each room shape and size has a slightly different effect. So what I did was take a mean or average of what could be expected in most rooms. If you factor in room gain of about 3 db at 60 hertz and 6 db at 30 hz 8 to 9 at 15 hertz you end up with a pretty flat response. Engineered to perform.

So that being said. Do you need fancy shmanchy EQ's?

Maybe. But keep this in mind. Every db in peaking requires quite a bit in terms of greater excursion. In fact on the TRIO12 a 3db gain will require 4mm of greater displacement. You quickly run out of linear throw on the driver.

2. High Pass Filter. To cut the low end or not?

Well what are you listening to that has any real content down lower than 14hz?

Seriously?

Well yes it is possible to bottom out the driver how you could accomplish that is a bit on the crazy side of things. The rear chamber acts as a sort of spring that keeps things behaving down that low.

So if you want to do this you cut create a high pass filter and cut out everything below the horns passband. About 14 to 15 hertz is safe.

WinISD will not model what happens inside a horn. In fact when it comes to accurately modeling driver excursion I do not use WinISD. It has some interesting gremlins that make it rather untrustworthy at times. I use Hornresp. Very accurate. But it will not model a EQ peak directly. That you have to do the hard way.

BASH = TRASH nuff said. I don't like them.

Their power ratings are way over blown. But they can be economical. For this box I would recommend the 500 if you were buying from scratch. It will give you more headroom. But keep in mind that a good solid one hundred watt amp will knock your socks off.

3. Sallen Key? Is that like a car key?



OK I'll behave. Yes a mild boost at 13.9 or 18.7 will do two things. Remember that you will get a bit of greater output but you will also get a greater rate of roll off in the response below that knee or center point of the boost point. So it will act as a bit of a high pass filter or low end cut off.

4. Unlike a conventional sub this puppy does rock and roll. It behaves itself. If you build it out of OSB and brace it as is instructed you have an extremely stiff box. Again I state unequivocally that 7/16" OSB is plenty strong to build this out of. Of you don't like the finish skin it with something you like. The material qualities of OSB make almost ideal for building loudspeakers. It has two outside layers that are very dense with a softer core. Thus it is naturally internally dampened. Perfect for subs where you want something not to vibrate.

I used to build everything with 1 1/8th " MDF. Remember I'm a cabinet maker by training. Then try moving such beasts when a single sheet weighs in a 189 lbs. Just try pushing it across a table saw! It occurred to me that light and stiff will work just as well as big and heavy. In fact there is less energy storage potential in a lighter structure than in a heavy one.

5. Every room can be different. Some will load better close to the ceiling some from corners. Some from the middle of the longest wall. Short answer play around. If you have a predetermined position it might be best to point the mouth towards the wall and listen. Move it away a bit and listen some more. The distance between the mouth of the horn and the closest boundary does change the tonality of the response. You can tune this box to a degree.

6. Yup. Your choice both are good ideas.

Mark

[kadijk]

Thanks Mark. Great info. I can't wait to start the build. I'm planning on driving the sub with either my Yamaha ax330, rated at 65w/ch, or my Kenwood kr-v7030 rated at 100w/ch. Both work good as sub amps in my mind because they have a line direct option with no post processing, so I run the sub feed out of my receiver into the cd line in on these amps and then just turn up the bass gain and turn down the treble gain for a cheap, reasonably powerful sub amp. I hope one or the other will be appropriate for the trio horn. What do you think?

[mwmkravchenko]

Leave your tone controls on the middle position. A sub feed off of a receiver is already limited on the top end and most bass controls boost at about 100 Hz. To high up to be helpful on a sub.

[kadijk]

Finally...saw dust is flying in the Kadijk shop!! At least into the dust collector, hopefully. Yes, the taxes got done, books caught up to date, some things done around the house and top it all of, I cleaned the garage to prep for this project. I wish I had a "before" picture...



I have around 500 sqft of shop area, and before cleaning up, I had around 40 useable. 4 truck loads to the dump and some serious organizing, and things are a little more acceptable. Still need insulation and drywall, but I can't wait any longer to get this show on the road.

As you can see, I got the main sides cut and laid out ( thanks to mose for the layout plans). I have decided to use 1/2" mdf instead of the suggested osb, and 3/4" for the driver mounting board. I will be using biscuits for all joinery onto the "bottom", and in the corners. I think that I will be doing a combination of carpenters glue and PL Premium, depending on the situations as they arise.



One little hic-up today. Yesterday I cut and machined the motorboard( driver mount) and was completely unhappy with the way it turned out. With the hole cut the right size for the driver, there is not enough edge thickness for the threaded inserts to grab. So today I made a new one, and took a few extra steps in the process. First I did a 3/16" rabbit for the driver to sit in rather than having it simply flush on the board. Then I routed the hole 1/8" smaller than the actual driver flange. After laying out the mounting holes, I reset the circle jig and cut the original size hole( in this case 11"), leaving the area close to each screw untouched so that there is enough edge thickness for the inserts. And then for good measure, I rounded off all the edges to improve air flow coming directly off the driver. Test fit everything, and then used Elmer's Ultimate polyurethane glue(similar to Gorilla Glue) to lock in the threaded inserts.


New and improved motorboard with inserts glued in



first attempt at the motorboard. You can see the threads of the inserts coming through the edges. I couldn't leave it like that and sleep well...

Time to let the dust settle, and get some rest.