100Hz two-way synergy project

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Gonna use two 12"s and a bms 4594he CD. So technically not a two-way due to the coax CD, but two-way still seems to be the the best description. Plans are to crossover between 12"s and the CD at 500Hz.

Syn will cross to a sub at 100Hz. That's the crossover point I've been using for all my multiway projects, and with recent straight and CBT line array projects.
I can't see trying to take the synergy lower than 100Hz, because to get a synergy down to 30Hz with authority gets ridiculous in size and weight. So since a sub is needed, I can't see the point in trying to reach much lower than 100Hz.

Going with 60Hx40V. First prototype shown below was set for pattern control at 420Hz.
I plan the final build to control to 290-300Hz, but i wanted to try my hand on a smaller one first, to try to get the learning screwups over while the material costs are smaller. Used BWaslo's excellent spreadsheet...bless you Mr. Waslo...I couldn't be at this point without you.

The measurements are the BMS CD sections at about 1m OA for any interested. Looks like 500Hz should work fine.
I wanted to measure the CD in the horn without the 12" ports to see how response changes when the ports are added.

Speaking of ports...I've been trying out different size holes, with different locations relative to the 12"cones, and with different thickness horn walls/ thicknesses.
I don't mean ports in the horn itself...I mean ports as they pass sound from the drivers mounted in a simple small box....before placed in the horn.
Also tried a bunch of different phase plugs to reduce volume under the driver, and raise freq response.
1/16th steel works best as far as port thickness (just like patent says) but not that dang much better than 1/4" wood...(which i was happy to see.)
Ports liked to be more towards a center axis, which increases distance to apex, but again not that much better than moving them towards driver end for needed tighter spacing.

Anyway, psyched to be back building again...thx for looking :)
 

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Thanks so much for linking your project, I had not seen it yet.
Just read the full thread.
Awesome build(s) ! Great discussions.
And your picts really help. The biggest unknowns for me, are figuring out the final box and access plates. Well that, and figuring out the dixie cup extender...bless you and Art of course, for making that clearer..

Yes, the box next to my synergy start is the Peter Morris 90 degree version. It also converts to the 60 degree version. Wonderful design Peter shared. But I must admit, I'm really hoping the synergy effort makes even better sound. A couple of PM90 measurements are below..the box sounds super and gets damn loud :D

I see you put your 12"s on the narrow angle panels. Right now, I was planning on the wide angle panels, but I've been reconsidering. Logistically, handling wise, and final box construction wise, is there reason to favor one over the other?
 

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I see you put your 12"s on the narrow angle panels. Right now, I was planning on the wide angle panels, but I've been reconsidering. Logistically, handling wise, and final box construction wise, is there reason to favor one over the other?
Mark,

On the SynTripP, the inclusion of the adjustable angle pole mount would not have been possible if the speakers were not located L/R on the narrow angle panels. With your larger cabinet, that issue may not be a consideration.
Although cone gravity displacement on a 12" won't be much of an issue, my preference would still favor placing the cones upright in the orientation the cabinet is typically used.

Good luck in your sonic pursuits!

Art
 
Thanks so much for linking your project, I had not seen it yet.
Just read the full thread.
Awesome build(s) ! Great discussions.
And your picts really help. The biggest unknowns for me, are figuring out the final box and access plates. Well that, and figuring out the dixie cup extender...bless you and Art of course, for making that clearer.

Yes, the box next to my synergy start is the Peter Morris 90 degree version. It also converts to the 60 degree version. Wonderful design Peter shared. But I must admit, I'm really hoping the synergy effort makes even better sound. A couple of PM90 measurements are below..the box sounds super and gets damn loud :D

I see you put your 12"s on the narrow angle panels. Right now, I was planning on the wide angle panels, but I've been reconsidering. Logistically, handling wise, and final box construction wise, is there reason to favor one over the other?

The dixie cup is just to make the box smaller and the horn larger. And it works! Saves a lot of weight and space.

I'm sure that 4594 sounds awesome! It'll do well in a synergy. I must admit that in my synergies the bottom end is a bit 'problematic'. The sensitivity is a bit low compared to the rest of the frequency spectrum. It drops off quickly below ~150 Hz without the hornloading. I've tried to improve it trying different bass reflex tunings, but that only goes so far...

Those measurement curves of your Peter Norris box are really something (even if it is with EQ, it is, right!?).

My reason for putting the twelves on the sides are mostly because of the space they would need, which would make the box quite a bit bigger. And this inner volume isn't really needed if you want to tune the bass reflex ports high. In fact, I had to fill up a lot of space to make the volume even smaller. Polyurethane foam did the trick ;). But all Art's comments also make a lot of sense.
 
Mark,

On the SynTripP, the inclusion of the adjustable angle pole mount would not have been possible if the speakers were not located L/R on the narrow angle panels. With your larger cabinet, that issue may not be a consideration.
Although cone gravity displacement on a 12" won't be much of an issue, my preference would still favor placing the cones upright in the orientation the cabinet is typically used.

Good luck in your sonic pursuits!

Art

Art, this horizontal vs vertical mounting stuff makes me reminiscence to the PPSL sub discussion ;)

And yep, it only makes sense that drivers in upright orientation has to be the default preference.....

I think after I mess up this prototype, I will go to side mounted...if for no other reason than replacing vertical side panel port attempts on a 60x40, will spit out a lot less wood destined for the scrap pile ! (than replacing long horiz panels)

Thx for well wishes re sonic pursuits :)
 
The dixie cup is just to make the box smaller and the horn larger. And it works! Saves a lot of weight and space.

I'm sure that 4594 sounds awesome! It'll do well in a synergy. I must admit that in my synergies the bottom end is a bit 'problematic'. The sensitivity is a bit low compared to the rest of the frequency spectrum. It drops off quickly below ~150 Hz without the hornloading. I've tried to improve it trying different bass reflex tunings, but that only goes so far...

Those measurement curves of your Peter Norris box are really something (even if it is with EQ, it is, right!?).

My reason for putting the twelves on the sides are mostly because of the space they would need, which would make the box quite a bit bigger. And this inner volume isn't really needed if you want to tune the bass reflex ports high. In fact, I had to fill up a lot of space to make the volume even smaller. Polyurethane foam did the trick ;). But all Art's comments also make a lot of sense.

Yep, the dixie cup idea rocks, especially for portability / PA.
I'm toying with the idea of making it out of thick foam board...

The PM90 measurements we definitely EQed, and used linear phase crossovers. I stuck 'rephase' on their comment field to help folks gather linear phase was involved.

Interesting to hear the bottom end of your synergies is a little problematic...
I've been studying posts on port placement (which mostly talk about mids), and have been trying to incorporate comments about port location needing an appropriate flare rate to reach down low in frequency.
In Hornresp I keep getting that a port location within 1/4WL of a 500Hz crossover, has a pretty high flare cutoff freq.

Sometimes I get the impression that mids used in synergies are as much for the purpose of being able to move the low ports further out the horn, as they are for bridging to the CD...

On thing is for sure ...Gotta get better with hornresp :eek:
 
Sometimes I get the impression that mids used in synergies are as much for the purpose of being able to move the low ports further out the horn, as they are for bridging to the CD...

Hmm, that might very well be. But why then doesn't Art's SynTripP have mids? Why does his design get away with it? :scratch2:

I have experimented with bigger ports, letting them run further down the mouth, but that didn't seem to help much. Made things worse for the CD response if anything...
The most important thing was getting the ports as close to the CD entry as possible in order to get them to play high enough, but with 500 Hz as a crossover point, that seems a little less important. :up:
 
Yeah, I hear you re Art's SyntripP working without mids....
I'm guessing Art's box gets the low end it does due to very well designed BR ports..??
I've been studying your design and Art's quite a bit as I try to make sense of how ports work vs measurements. I've tried a lot of different sizes, shapes (circle vs ribbon vs teardrop), locations (corner vs center), distance from throat, etc.

The only thing I know for certain yet, is that how tight I screw the horn back together makes the biggest difference of anything I try :p

One big puzzler is that frequency response doesn't really go up as I minimize port to throat distance. I've been getting response to 500Hz almost independent of port location (or size)...from 2.5" to 6.5" (center of ports to throat).
Initial quick attempts at volume reduction under cone have shown more of an effect at raising freq response than port location.

I've pretty much used up the first prototype's ability to handle any more port experiments. Between thin sheet steel used as a port closing guillotine, and foam pugs and duct tape, she's about had it. Off to the junk pile !

Gonna build a 2nd proto now, exact same size 60x40, and will move drivers to the vertical panels (so a 40x60 in BWaslo's calculator, ableit with an 851Hz control freq)
 
Thanks ! Your projects are awesome...often over my head re horn design...
I didn't know the difference between a conical and a tractrix till I recently got in the synergy hunt. :eek:
I really like your Heil AMT with B&C 6.5" displayed in the current AMT Synergy thread. Wow.
Hey, a stupid question I've been dying to ask someone working with foamboard...how do you mount the drivers to the foamboard? What holds up well?

Speaking of the AMT Synergy thread....the following measurement might be of interest in relation to the discussion there, about HF drivers getting moved by mid energy put into the horn.

The green trace is one of my beginning 12" port attempts.
At first I thought the notch at 375Hz was quarter-wave cancellation. (May still be..port center was 6.5" from throat, and bms 4594 may have an acoustic depth of 2.5" or so.)
But whether it is 1/4 cancellation or not, the notch at 375Hz went mostly away when I shorted the lower section of the ring-radiator CD, pink trace.
 

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If you add another 2.5in from port throat to cone face center, that makes 9in and would correspond to a 375Hz 1/4wave cancellation. When you short the CD voice coil it acts to stiffen it so that the motion of the air pushing against it doesn’t get damped out as much. That’s good evidence that there is an effect. When you have the CD connected to an amp, it is even “stiffer” because it is reactive. If something pushes on the cone, that generates a back emf and if your amp has negative feedback, it will compensate by pushing back. So I think that notch goes away when you hook it up to an amp.
 
Yep, the numbers talk 1/4 wave. The interesting part to me, is where do we calculate 1/4 wave from, for determining synergy notch cancellation. I've heard some say from the throat, I've heard some say from the CD diaphragm. ...I'm not sure what to think re these reflections.
But I do feel certain phase timing between port and CD is diaphragm.
 
I'd argue that it can't be from the throat. The wave has to bounce off of something and the throat is not a hard surface...

That makes sense to me too.


Anyway, bit of a progress report and a few ongoing questions....

2nd prototype shown below, with 12"s on the sides now. After a bunch of port tries, here's the best I've found so far. 1" wide, 3" long, round ends, frustumed, ...center is about 13cm from throat.

Not sure those are going to be big enough...hey, is there a way to model the port velocity in hornresp?
Also, how do you model BR ports?

Anything bigger than those ports really seems to start messing with HF response.

Raw measurements of the passbands, along with a quick and nasty tuning are below.

Had to take a listen :) It sounds amazingly good for a box that is held together with a dozen sheet rock screws. The 12"s are held on with just 2 screws each :eek:

As long as I keep volume below maybe 100dB/1m...not that many resonances Lol
Oh, and I guess i still have to enclose the 12"s .....and BR port them...

Much to do still...
 

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re' .hey, is there a way to model the port velocity in hornresp?

Yes. go to the acoustical power screen of your HR sim. Click tools menu and select particle velocity/'throat port exit.

Also, how do you model , BR ports?

Go to the input screen, click tools (you may have to click edit first) select chamber type/rear vented. Next go to tools/loudspeaker wizard/chamber where you can play with the vent tuning
 
Thanks diyuser2010,


and thank you nc535.
I've got the BR ports working per you instructions :)
But I think I'm missing something still on entry port velocity.
When I go to acoustical power, tools, particle velocity...I get choices for throat, S2, and mouth. I'm thinking S2 is the entry port, the one whose parameters I vary in the ME1 record ????

I vary Ap1 in the ME1 record, activate it, and then go to the main record, to see if velocity changes for S2, (or for the throat, trying to figure out what is what).
No matter what changes I make to Ap1 in the ME1 record, I see no changes in particle velocity for either S2 or throat...

I need to get this velocity stuff down because I'm finding the entry ports mess with HF response alot more than i thought they would.

Did many outdoor measurements today...surprised to see how much variation there is on and off axis, even with no entry ports at all.
And then how entry ports amplify the straight horn variations.
Anybody else have this experience?

The really crazy part of measurements appears to be an on-axis hole around 2kHz, horn alone, no ports. A hole that hat gets really ugly with even the smallest of ports.
Off axis looks pretty good :confused:
 
My referents are to an offset driver (with a BP chamber) ported into a horn at S2. When you build up the full ME1, ME2 model, names might change as well as where to look for things like particle velocity.

You could strip down your model to just the offset driver in a single record and then things might be more clear. I can't imagine changing the offset port area at constant power and not seeing a change in its particle velocity. But if you also have a bass reflex port in the same sim, its easy to be looking at the wrong thing. I would be happy to play with your model and pass it back if you care to post it or pm it to me.

As to the polars, a single segment conical has well known deficiencies, notably a narrowing just before it loses control of directivity and a healthy mouth reflection. If you remove the offset driver port and sim it as an Nd, then HR will show you the directivity of the single segment conical horn. Adding a 2nd segment will definitely improve your polars but HR will no longer be able to compute its directivity.

It will be nice if you get even a semi quantitative picture of the effect of the offset driver port holes on the polars. Its worth doing the engineering to be able to minimize their size. To me that would include tuning the bass reflex so that the last half octave or so came from the reflex ports further down the horn instead of the offset ports.
 
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