With a CD horn you always design for flat acoustical power because you want even power distribution across its entire beam width. Another obvious clue is the fact you will aways have a falling high frequency response on an unequalized CD horn. If you run a simulation on a CD horn with an unequalized compression driver it will have a flat or rising acoustical pressure plot. We know this isn't correct.
No because acoustic pressure exhibits narrowing directivity as frequency increases. This is the reason for its rising response as frequency increases.
Does designing for flat acoustic power vs freq only apply when designing a CD horn combo? I note that all cone open faced driver specs are published as SPL vs freq and they tout how flat they are throughout the range. I guess I need to read up on this subject.
still struggling...please bear with me
Akabak is based on Webster's equation, which, being one dimensional, can't predict directivity. Per your quoted response, this falling response with frequency is a directivity effect and thus not predicted by the simulation. Therefore, the need for the rising SPL in the simulation in order to get flat SPL in a measurement of the speaker. The rising SPL in the simulation simply shows you've included CD horn equalization in your crossover.
Acoustic power is a characteristic of the source. Akabak predicts that the total radiated power is flat with frequency. Acoustic power is defined as the integral of the Intensity (i.e. SPL) over a surface that intercepts all the radiation - i.e. a segment of a sphere that covers the mouth of the horn. Given a CD horn, the integral can be approximated as the Intensity times the mouth area. Thus we can see if the power is flat with frequency, so must the intensity be flat.
Interestingly, use the "mean window" box in the SPL popup menu of Akabak to get the average SPL over an angle covering the horn mouth (which should be proportional to the power) and the SPL curve flattens out, except for a DIP around 3 kHz, which I would guess is related to the crossover.
Jack
An externally hosted image should be here but it was not working when we last tested it.
EAW does something like that with their Anya array.
Details are in their patents. The holes are a fibonacci sequence, similar to the second picture above.
http://www.sanecore.cn/sanecore/files/psecond/EAW_anya-photos.jpg
Here's a link to the pic; it's huge and you can't see the detail in the forum, easier to simply download it.
When I used a LeCleach horn for a Synergy horn, I ran into a massive dip due to the reflection off of the midrange ports. I used four symmetrical holes, located about 3.5" from the throat. I think the dip is caused by the size of the holes, the location of the holes, and the depth of the holes.
We can modify all of those variables, but those modifications all have an impact. If you make the holes smaller it changes the response and could limit output. Making the holes shallower is generally a good idea. I think that 'randomizing' the hole locations is an attractive option, since I would expect it to make the dip wider but shallower, which is easier to EQ away.
This issue is seen in the Danley horns too; the ones with wider coverage have smoother response at the crossover points. It's a tricky problem, because I definitely think there are some advantages to a narrower coverage angle. (LeCleach sounds really transparent, but has narrower coverage.)
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
These EDM kids like them Synergy horns 🙂
From this page:
https://www.facebook.com/pages/Alignment-Sound/164927260234328
So I am guessing a coaxial BMS and the Fatail 6pr150's?
They seem to have a clone TH221 also.
They seem to have a clone TH221 also.
I only guessed that one because he was talking about using that in his next build was all. I couldn't really make out what was there other than a Faital driver. He also said he had a bunch of BMS 4952 mids. So I was just taking a guess.
Cool to see more DIY synergy builds. Also cool to see the TH221 clone.
Cool to see more DIY synergy builds. Also cool to see the TH221 clone.
I'm still trying to understand why you guys are tweaking passive crossovers instead of slipping an active one and a getting the parameters to build passive???? Any receiver with direct multi channel in is about free at pawnshops and DCX2496 or minidsp is not bad
I'm going to start with a MiniDSP 4x10 and a stack of pro amps. If I ever convert it to a passive crossover it will because I want my wife to be able to turn it on. Never thought of pawnshops as a place to go for audio equipment.
I doubt standard active xo will work well with synergy speakers
anyway, I thought DSP was 'common standard' for this
me ... yeah, I would probably be daft enough to try and make a simple passive work
and I do wonder how Danley company makes sure their synergy designs works as intended
decent (Hdmi multichannel) receivers with volume knob controlled preamp outs are not so esy to find though. That's what you really need. Took me a while to find a cheap one.
SONY Str-dg**** series. Extremely nice AB design, analog in only. The DSP and conversion is pretty crappy, the multi direct in is really really nice. Amps are suprisingly clean. Some Pioneers of that era too.
Why not mock up in active ,build passive?
I doubt standard active xo will work well with synergy speakers
anyway, I thought DSP was 'common standard' for this
me ... yeah, I would probably be daft enough to try and make a simple passive work
and I do wonder how Danley company makes sure their synergy designs works as intended
Pete,
If you already have active (DSP), there would be no reason to go passive .
Things that are trivially easy to implement with DSP can be very difficult or even impossible to do passively.
If you are committed to a good frequency and phase response using passive crossovers on a DIY Synergy, you have to be committed to a lot of part substitution trials to achieve it.
There are no predictive crossover design programs that can cover all the variables sufficiently to get you more than "close, but no cigar".
Art
I've had very good simulations with PCD matching a build. That's using measured unfiltered responses of each driver (or set) mounted in the horn. I don't think you could get there with raw "test baffle" driver measurements, though, if that's what you meant.
1970, I used two EQs, made my own. Can't imagine why we are messing with passive still.