Low budget PA Synergy project

[Droco]

While I'm still busy perfecting my large (110x80x60cm) synergy horn for home use, I have decided to start designing a small synergy horn for PA use.

Design goals:
- 40 (horizontal) x 60 (vertical), to be able to arrayed into a 80x60 and 120x60 horn
- conical horn (designed with bwaslo's spreadsheet)
- directivity control down to ~200-250hz
- 80hz crossover to subs
- active crossover using miniDSP HD

The part where I would like some assistance in, is recommendations for drivers. I'm thinking a 2-way with 700hz xover should work if I use a 2" or 1.4" CD, but I'm not sure if the cheaper CD drivers (from P-Audio for example) are able to do this with success. 4x 10" drivers for the low end (probably ported with a 80hz tune). 3-ways using midbass drivers add a lot of build and design complexity I would like to avoid.

 

[1hiep0]

a small synergy horn for PA use.
I'm thinking a 2-way with 700hz xover should work if I use a 2" or 1.4" CD.

Droco, This might be interest
SynTripP: 2-way 2-part Virtual Single Point Source Horn
or this with 2 12" but might not be cheap
Synergy horn for 135 dB+

 

[kipman725]

I would strongly recommend going 3 way as it can save money and increase performance. To reduce complexity use a passive XO between the tweeter and the mids. As you point out tweeters that can go down to 700Hz are expensive whereas 1" drivers that can get down to 1.3kHz are not so expensive and have improved HF performance. At the same time the crossover to the bass drivers can be done at a much lower frequency allowing the use of larger lower quality drivers. If you look at high output two way synergy designs they use expensive high performance drivers, by going 3 way even though you have more parts the overall cost is less.

Here is my synergy like project:
BM-D446 on PH-4220
I am very happy with the BM-D446 1" compresion driver and the faital pro 3FE25 both of which are budget drivers. If making your own horn you might be able to fit 6" mids on which could allow you to reduce the quantity to 2 per horn. The key with the crossover is to incorporate the acoustic rolloff characteristics of the mids into crossover slopes (IE the electrical slopes are asymmetrical and crossover is only possible at one frequency). Making little paper mache rear chambers for the mids is very fiddly and takes ages, also impedance measurement is needed to confirm proper sealing, however its very cheap

 

[mark100]

I'm confused by your directivity goal?
Do you mean horizontally, when 2 or 3 units are arrayed together?
Or vertically for one...since your box is 40x60?
In any case, it looks like your are taking about big sized boxes, not small...????

And like kipman725 said, and as you surmised, ...cheap and a CD down to 700Hz don't go together.

All that said, I've become very happy with a 60x40 (285Hz control) that uses a 1.4" coax CD, and two 12"s. Alas, neither cheap nor small...

 

[Patrick Bateman]

If you want moderate output, look at the SH50 and it's many variations. It's a three way that peaks at 133dB.

If you want to save a few bucks, look at the SH95. Because it's a two way, maximum output is "only" 126dB.

But that's still a LOT.

IMHO, its WAY harder to make a two way Unity horn than a three way, so you have your work cut out for you.

Read more here : Two Way Synergy???

 

[Droco]

Droco, This might be interest
SynTripP: 2-way 2-part Virtual Single Point Source Horn
or this with 2 12" but might not be cheap
Synergy horn for 135 dB+

Thanks for the 2-way suggestion! I'm not yet fully satisfied with my horn, and allthough I know some weak points I still need to fix, I still need to get some insight to know why I doesnt sound as I would like it too. Mine uses similar drivers, nd active crossover. Plan is to use 4x woofers and a coaxial in the end to make an absolute SPL monster (140db+).

 

[Droco]

I would strongly recommend going 3 way as it can save money and increase performance. To reduce complexity use a passive XO between the tweeter and the mids. As you point out tweeters that can go down to 700Hz are expensive whereas 1" drivers that can get down to 1.3kHz are not so expensive and have improved HF performance. At the same time the crossover to the bass drivers can be done at a much lower frequency allowing the use of larger lower quality drivers. If you look at high output two way synergy designs they use expensive high performance drivers, by going 3 way even though you have more parts the overall cost is less.

Thanks for reminding me! Using a passive crossover between the 2 could also negate the need for extra XO channels, so thanks for the suggestion!
On the other hand, it does look like a few 100USD 1.4" drivers could hit 700hz -3dB, although this is based on specs, not real life experience so I might be wrong.

Here is my synergy like project:
BM-D446 on PH-4220
I am very happy with the BM-D446 1" compresion driver and the faital pro 3FE25 both of which are budget drivers. If making your own horn you might be able to fit 6" mids on which could allow you to reduce the quantity to 2 per horn. The key with the crossover is to incorporate the acoustic rolloff characteristics of the mids into crossover slopes (IE the electrical slopes are asymmetrical and crossover is only possible at one frequency).
So you mean the crossover between HF and MF, while still using an active crossover between HF+MF and LF?

Making little paper mache rear chambers for the mids is very fiddly and takes ages, also impedance measurement is needed to confirm proper sealing, however its very cheap

Cant you just use a square box around it? And arent there some backchambers you can buy for these kind of smaller drivers? In any case, fidgitty is OK, as long as I can pull it off

 

[Droco]

I'm confused by your directivity goal?
Do you mean horizontally, when 2 or 3 units are arrayed together?
Or vertically for one...since your box is 40x60?
In any case, it looks like your are taking about big sized boxes, not small...????

Well, "small" is relative. I was not defining it yet as smaller is better, and I will get them as big as they need to be. I was hoping for something with max 50cm in any direction.

And like kipman725 said, and as you surmised, ...cheap and a CD down to 700Hz don't go together.

All that said, I've become very happy with a 60x40 (285Hz control) that uses a 1.4" coax CD, and two 12"s. Alas, neither cheap nor small...

I use a second hand JBL 2447 (~150 euro each) and it does the trick easily, the weight is th hough one.. over 12kg The coaxials are awesome for PA, so I might consider using them, but they are so expensive...

 

[Droco]

If you want moderate output, look at the SH50 and it's many variations. It's a three way that peaks at 133dB.
Cant seem to find the drivers that they use, as to get an idea of what is necessary.

If you want to save a few bucks, look at the SH95. Because it's a two way, maximum output is "only" 126dB.

But that's still a LOT.

IMHO, its WAY harder to make a two way Unity horn than a three way, so you have your work cut out for you.
Harder in what way?

Read more here : Two Way Synergy???

 

[Soldermizer]

Patrick said "IMHO, its WAY harder to make a two way Unity horn than a three way".


At first seems counter intuitive, but you are the guru. In any event I am so grateful to have my trashed pair of Yorkville U15, which are a well regarded, two-way Unity unless you count the 15 inch woofer for < 300 Hz