Compression ratio/new build

[Dag Johansen]

Hi, first post in this section.
Thought i would share my project with you.
First off i would like to say that it is not my intension to disrespect Tom Danley and his work, he is my gratest inspiration, but i am not doing this for money - just for fun.
Even if this project turn out very well i will not sell these speakers.

This is a 2-way project.

I have searched these forums to find out some more about compression ratio in this Synergy/Unity type horns.
Studying the photos of SH 50 one can see the holes for the twelves and they are not big.
The holes in my horn is 12,5cm2, two holes per woofer, so 25cm2.
That correspond to 1:9 compression with eigth inch woofers.
Would that be a problem?
I am aiming for 90-100Hz downwards.

So.... any input?
As i said, its just for fun!

My english is not that good, but i think you understand!

Dag

[pk]

Hi Dag,

That's very impressive woodwork! I can easely understand what you are after here. I really wish I had the woodworking skills and technical knowledge to clone the Danley SH-50's for a serious home rig.

What crossover frequency are you after? How do you intend to make the transition from square to circular for the compression driver? And which drivers will you be using?

Please keep us informed about the progress on this project (measurements, etc.!)

Thanks and good luck!

Best regards
Peter

[Dag Johansen]

Thanks for nice words PK.
The transition between the driver and the horn will be grinded to a round smoth surface.
To begin with i will try Eminence Alpha-8 for bass/midrange and Eminence PSD2002A - 1" Compression Driver for tweets.
I will have to experiment a lot with crossover frequency.
For this i have a plate-amplifier with buildt in DSP from Digmoda.
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I will post some meassurements when i get to that stage!

Dag

[pk]

Hi Dag,

Thanks for responding. It definately sounds like an interesting project! I may be wrong, but if I understand it correctly, then the crossover point between the mids and the tweeter is more or less determined by the positioning of the holes for the 8" mids (the holes should be placed at distance specified by 1/4 of the wavelength of the crossover point).

I am currently using the Beyms TPL-150H ad tweeters and like them a lot! Given the rectangular profile of the TPLs they should be great candidates as tweeters in a SH-clone (no need for making transition from rectangular to round).

BTW: the IcePower amps in your Digmoda's sound great!

Best regards
Peter

[panjilaras]

i believe the midrange port is frustoconical not just simple hole. JLH is the man for explaining synergy theory in layman term.

[jeno]

Hi!

Cool project!

Have you read the patents on the Unity horn and the Synergy horn? If not I recomend reading them before doing more work. They are easely found by the google patent search. If you are going for a trial and error aproach I think it may be very difficult to make this work.

If you read the Unity patent you will see that the area of the insert holes should equal the area of the horn at the insert point to match the impdance at the insert point. But in the Synergy patent you will see that the holes/ports may be reduced in size if you use a frustroconical shape or a stepped port. I don't think Tom Danley has given away the exact answer to this, so here trial and error may be the only way to do it anyway.

Anyway, good luck with your project! Would love to hear the result if you make it work.

[doug20]

I definitely have to follow this, its on the list of projects I would love to complete some day!!

[Dag Johansen]

Thanks for all the inputs guys!
Ok, i have now read the patent part about the holes and the frustoconical/stepped port.
If i understand it correctly it has to do with the bandpass effect!?
Would it not be better to make some kind of phaseplug to minimize the "chamber" in front of the driver!?
Or maybe thats the whole meaning of the construction, to make a small bandpass system, firing in to the horn?

I have been fiddeling around with loudspeakers for 35 years, and i know a lot, but i also realize that there is so much i dont know.
(and that many of you guys know a lot more than i do )

Anyway, this is a work in progres and i try to understand as i go along.

If there was a dealer here in Norway i would most likely bought a pair of SH-50 as they appeal to me.... they are downright sexy!

Dag

[pk]

Originally Posted by Dag Johansen

Thanks for all the inputs guys!
Ok, i have now read the patent part about the holes and the frustoconical/stepped port.
If i understand it correctly it has to do with the bandpass effect!?
Would it not be better to make some kind of phaseplug to minimize the "chamber" in front of the driver!?
Or maybe thats the whole meaning of the construction, to make a small bandpass system, firing in to the horn?

I have been fiddeling around with loudspeakers for 35 years, and i know a lot, but i also realize that there is so much i dont know.
(and that many of you guys know a lot more than i do )

Anyway, this is a work in progres and i try to understand as i go along.

If there was a dealer here in Norway i would most likely bought a pair of SH-50 as they appeal to me.... they are downright sexy!

Dag

Hi Dag,

If I were to start all over again, I think I would go for a pair of SH-50s as well! You may already be aware of this, but DSL has recently got a dealer in Europe (Poland).

soundmission.eu - Home

At least we now have a fair chance to listen to these beasts!

Best regards
Peter

[panjilaras]

JLH/GM/Bateman/Synergy experts, please slap me,

the frusto thingy is designed to:
1. low pass filter uper harmonics by air chamber inside port plus inside cone
2. of course as midrange sound exit, but it is small enough to make it invisible to HF, yet large enough to avoid port noise / high port velocity.

did you do simulation of this box? why not using delta pro 8a?