Hi Mani,Is that a B&C compression tweeter?
Mani.
The horn flare is an elliptical profile designed for constant coverage and minimal diffraction. Not sure what you mean horn compensation on the compression driver."Crossed at 650hz with 2nd order Butterworth. Horn gain is reduced by 14db compared to 96db Fostex driver! "
Hello morricab
Nice! So what type of horn flare?? You doing any horn compensation on the compression driver??
Rob
Ok, I understand you well now. Thanks for clarifying. So far, I have not made measurements as I didn't really have much free time. I have been tuning by ear but will put the measurement tools to use soon and see how close I got "by ear" to a reasonable response. I did do a bit of boost above 5Khz because that is where the driver itself starts to droop with a steady shallow slope to 20Khz. I put in about 3-5 db of boost and left the rest flat (the driver actually measures very flat from about 600Hz up to 4-5Khz); however, I don't know yet what the horn is contributing because the measurements from Beyma were in a Beyma horn. Once I measure a bit on and off-axis I will be able to give you a better idea what this driver is doing in this horn.Hello morricab
Depending on horn type CD or Exponential, as examples, the Exponential would be relatively flat on axis because it uses the DI ,directivity index ,which increases with frequency to compensate for the mass roll off of the compression driver. You are flat on axis and rolled off off axis. The off axis roll off gets more pronounced the higher you go.
A modern CD horn has a much more constant DI with frequency so the on axis response follows the mass roll off. You typically get a peak in output around 1-3K and a roll off above. This will be consistent off axis as well because of the more constant DI. On a CD horn you would use either passive or active EQ to flatten both the on and off axis response. That EQ is the horn compensation I was curious about.
The amount of roll off in a CD horn gets less the narrower the dispersion pattern is. So a 60X40 would require less EQ, horn compensation, compared to say a 60X100 as an example. The only way to know for sure is look at the on axis response curve for your particular compression driver and horn combo as different responses are certainly possible on the same horn with a different compression driver.
I as a rule use CD type horns so all of my systems have horn compensation built into their passive crossovers. Even my active set-ups use passive compensation as all of my active crossovers are simple analog. I enjoy designing the passive networks even though it can be much more time consuming than using DSP active filters.
With you using a digital active it should be quite simple for you to dial them in if you feel the need. Modern digital DSP is a mighty handy tool. One of these days!
Rob
Dear OP,
Please can you tell us more about how the mini DSP is working out for you as I deliberated it for my project but decided to keep purist (but still my get one to experiment with). Also what was the design criteria for selecting the Fostex? Did you consider trying to back load that to get sensitivity up a lot to avoid curtailing the compression driver so much?
So far it works very well. It does precisely what I wanted from it, which is xover, attenuation level matching, time delay and some eq. I didn't want one with analog out (I already have that with a Behringer DCX2496) because I wanted to use high quality DACs. The other amp I will get will need to be integrated because then I will do the level matching in the analog domain with amp gain rather than with digital attenuation (not sure how much that is degrading the sound with this box at this time). I might eventually go passive with it but this is a great design tool and the SQ from only one speaker so far (need that other amp first) is really quite good and measurements should help me dial it in further both in frequency and time.
The bottom part is a commercial speaker (Decware HDT) so that design was settled on a long time ago. It actually gets a lot more bass out of this Fostex (a proper 38hz) than any of the backloaded designs. The cabinet design is using multiple tuning with three internal ports, a transmission line of sorts and passiver radiators on the sides. The damn thing is very fast and the cone barely moves...like in a horn! Horn loading would boost maybe a few db but sacrifice the bass punch. 96db is pretty good and low level listening its forte. As mentioned above, I want to eventually have analog gain level matching rather than digital attenuation.
That being said, I will replace them with Supravox single driver speakers (99db and no whizzer cone) in a TQWT loading. Evenutally I will transplant that driver into a new DTQWT with 2 x 10 or 2 x 12 inch drivers on the backside (like Horning is doing). The Supravox driver will also feed the TQWT then and contribute to the bass along with the two dedicated bass drivers. This would be a variation on what Troels Gravessen has done in DIY (but later as a kit from Jansen). I will use a preferred midbass and true horn upper mid/high rather than his midbass choice and a normal softdome tweeter in a waveguide (not my first choice for HF drivers).
Hi,
Thanks for the detailed response - it makes sense.
I thought the Aries horn is a back loaded design?
It’s what I had handy to play with .Hmm, if you're going to xo @ 600 Hz you really don't need a single driver. I'd consider a larger woofer that will match your horn's directivity at xo... maybe an Acoustic Elegance TD12 or similar.
Right now it's likely the dispersion of the single driver and horn do not match so you have a step in the polar response which is nice to avoid if possible.
So does it sound right at all having two different DAC's and amplifiers?
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