Actually, your point about the ports is a good one. I don't think the compression driver will be affected, but reproducing 150hz with the 5" midranges will generate a lot of air at the port.
IE, you'd likely need to enlarge the ports.
In that case, I'd just go with a three way. It's a lot easier to add more drivers to a Synergy horn than it is to widen the bandwidth of a driver. For instance, I've frequently considered going to a four way Synergy, because it's such a pain in the *** to fill in the hole that occurs at 1500hz. IE, something like this:
compression driver : 1500hz - 20khz
2" mids : 750hz - 1500hz
5" mids : 375hz - 750hz
8" midbass : 100hz - 375hz
IE, you'd likely need to enlarge the ports.
In that case, I'd just go with a three way. It's a lot easier to add more drivers to a Synergy horn than it is to widen the bandwidth of a driver. For instance, I've frequently considered going to a four way Synergy, because it's such a pain in the *** to fill in the hole that occurs at 1500hz. IE, something like this:
compression driver : 1500hz - 20khz
2" mids : 750hz - 1500hz
5" mids : 375hz - 750hz
8" midbass : 100hz - 375hz
Using a round or circular elliptical horn for a Synergy is a bad idea. Yes, Yorkville did it and it was done with the PSE-144. That doesn’t make it a good idea. The reason why a rectangular horn is superior is the acoustical pressure inside the horn is much lower in the corners. By placing the midrange entry ports in the corners you reduce the acoustical image size of the ports which will help prevent frequency abnormalities. Using a round horn will make things much more difficult in an already very challenging design.
The PSE-144 seems to be relatively free of "abnormalities" and is easily corrected with simple DSP.
PSE-144 Response
PSE-144 Response
I'm sure it will turn out good; all of Spencers horns are fantastic. I wish I had his craftmanship.
But John is still right.
This measurement is on a 120dB scale; that's just silly. Let's see a measurement on a 50dB scale without any DSP filtering applied. And let's see some polars. The effect of the exposed midrange taps will be most noticeable in the off-axis response.
Again, not saying Paul's will be bad, but square is the way to go. The rectangular QSC waveguide works fantastic, is $35, and is available worldwide. The rectangular JBL waveguide is definitely on the small side, but it's excellent in it's passband and it's $12. It's really really hard to do better than these two.
But John is still right.
An externally hosted image should be here but it was not working when we last tested it.
This measurement is on a 120dB scale; that's just silly. Let's see a measurement on a 50dB scale without any DSP filtering applied. And let's see some polars. The effect of the exposed midrange taps will be most noticeable in the off-axis response.
Again, not saying Paul's will be bad, but square is the way to go. The rectangular QSC waveguide works fantastic, is $35, and is available worldwide. The rectangular JBL waveguide is definitely on the small side, but it's excellent in it's passband and it's $12. It's really really hard to do better than these two.
I don't think you should be comparing a tiny high frequency horn to one that covers 250 Hz - 20,000 kHz. The whole purpose here is to get a wide bandwidth point source loudspeaker with good pattern control.
I don't care at all that the plot is for active XO with some correction. I have not built a speaker in the last 20 years that I did not apply digital XO and correction to.
Just extend the mouth then. The stock QSC waveguide is good to 900hz; extend the mouth to get down lower.
I don't see any practical way to make the QSC into 250 Hz synergy horn.
Patrick did you do any more testing with your 152 WG and synergy idea?
I remember seeing the videos but you seem to do so many projects that maybe you just moved on to something else.
I thought about just building a SH with my 3.3" drivers and a CD. Just make a small horn that doesnt have to go down very low at all. Then try and build an extension that would contain bass drivers to complete a 3 way. That way I can work on trying to get the CD and midranges correct and not waste MDF/Plywood.
Either way with all things SH projects I keep seeing I have hope still that I will be able to complete my own to my satisfaction.
I remember seeing the videos but you seem to do so many projects that maybe you just moved on to something else.
I thought about just building a SH with my 3.3" drivers and a CD. Just make a small horn that doesnt have to go down very low at all. Then try and build an extension that would contain bass drivers to complete a 3 way. That way I can work on trying to get the CD and midranges correct and not waste MDF/Plywood.
Either way with all things SH projects I keep seeing I have hope still that I will be able to complete my own to my satisfaction.
It's sitting in the garage.
I'm having good luck with a funky Beolab kinda-thing, documented in "soundbar Bateman style" here on diyaudio
The synergy horns are very articulate, and are a real xray onto the recording.
But my beolab-type thingies image better, and the footprint is a fraction of the size.
The dynamics of both are similar; I might give a little edge to the Beolabs. I listen to them at a distance of less than one meter, so it doesn't take much to sound dynamic at that distance.
I'm having good luck with a funky Beolab kinda-thing, documented in "soundbar Bateman style" here on diyaudio
The synergy horns are very articulate, and are a real xray onto the recording.
But my beolab-type thingies image better, and the footprint is a fraction of the size.
The dynamics of both are similar; I might give a little edge to the Beolabs. I listen to them at a distance of less than one meter, so it doesn't take much to sound dynamic at that distance.
Square, meaning flat horn sides is strictly a cost saving, ease of construction measure. It permits the use of cut plywood or other panel material and allows for easy mounting of the midrange drivers over the ports. No fancy tooling or 3D CAD required.
I have seen measurements of dozens of synergy horn projects with the midrange ports in all positions, shapes, and sizes. The important factor is the distance down the horn from the compression driver acoustic center. One guy moved the ports right into the corners and the performance worsened. The other factor is tuning the front chamber resonance with the midrange driver (port area and length).
What problems did you face in hornresponse? Did you try any test setups to verify whether practically it works or not ? I am not using hornresponse and am tempted to try it outside the horn to start with.
Agreed. However the Synergies are intended for pro applications where the mids operate at very high SPL. I feel the affect of mids on the CD is SPL dependent and in home listening situations the mids are producing very less SPL. I am aware that the mids do affect highs adversely and it can be measured. I am questioning its perception in SPLs in home listening situation. Probably this is the reason why PSE-144 gets away with the elliptical mouth profile.
Thanks. Can you post a link to non-rectangular horn mouths (other than PSE-144) ? It would help me.
Mine are going to be active. Its already a 2 way horn + woofers below (outside) the horn. Cant afford the size and complexity of 3 way.
I had the same problems I always have with dual reflex bandpass:
1) it's hard to get flat and wide response. There is a complex interaction of the two ports. Sometimes you get narrower response than you would with a single reflex.
2) The results of a dual reflex bandpass are unpredictable. For instance, if you move one of the ports a couple of inches, it can change the response
Again, not saying it won't work, just saying that I never had any luck with it. I did try building a couple this way, back in 2010 or so.
Bose owns the patent on dual reflex bandpass boxes. Bose themselves stopped using them; they switched to transmission lines. Methinks they did it for the same reasons; it's very difficult to get predictable results with dual reflex and triple reflex bandpass enclosures.
Using a rectangular horn for a Synergy is not strictly for cost considerations. If that were true then the SM-60M and SM-60F horns should have never been created. In addition, I don't know how many times Tom has explained the same thing on this and other forums. Comparing Tom's results with various DIY attempts isn't even remotely applicable. An axial symmetrical or elliptical round horn is the least desirable form for a Synergy horn due to the technical details laid out in the patent. If someone wants to lean heavy on the DSP and EQ and adulterate their music that's their prerogative. However that doesn't change the fact the corners in a rectangular or square horn are the most ideal location for the mid and woofer entry ports in a Synergy horn.
It is unfortunate that you do not recognize the tremendous benefit that is brought to music reproduction systems throughout the use of digital signal processing. Here is a testimonial to the use of DSP from Audio Mastering Engineer Bob Katz: Bob Katz on Speaker Correction
Many scientists including Earl Geddes and others have thoroughly discussed the distortion in horns when transitioning round compression drivers to rectangular horn cross sections. This is a bigger compromise than the midrange entry points and severely affects the high frequency performance of a horn.
Oh, I'm fully aware and I recognize the ease (and design laziness) that DSP has brought forth. If it is done correctly from the beginning there is little need for such heavy handed measures.
"Not everything that can be counted counts, and not everything that counts can be counted." - William Bruce Cameron
Much of the "issues" Earl and others have been barking about are not audible and are of no consequence.
"Not everything that can be counted counts, and not everything that counts can be counted." - William Bruce Cameron
Much of the "issues" Earl and others have been barking about are not audible and are of no consequence.