First trials of active horn speaker

Feb 7, 2011
132
90
28
www.the2ndtier.com
#2
Is that a B&C compression tweeter?

Mani.
 
Feb 7, 2011
132
90
28
www.the2ndtier.com
#4
Ah OK. Thanks.

Look forward to hearing more about these speakers...

Mani.
 
Aug 25, 2010
991
18
18
Destiny
#5
"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 :)
 

morricab

Well-Known Member
Apr 25, 2014
3,129
365
83
Switzerland
#6
"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 :)
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.

Did some more experiments yesterday and found 600hz 2nd LR works even better. This is the low end of the range for both driver and horn but at my volume levels there shouldn’t be any stress. I will hopefully make some measurements soon to see how well everything is really blending. This CP755ti is really smooth sounding and I don’t hear coloration from the horn, which is important.

I also have a pair of Beyma CP350TI drivers with elliptical horns that I might try as an alternative but only crossed above 1.5khz.

Later I can see what sounds better but so far with this bigger horn/driver a lower xover sounded better.
 
Likes: Robh3606
Aug 25, 2010
991
18
18
Destiny
#7
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 :)
 
Mar 23, 2015
2,231
629
113
UK
#8
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?
 

morricab

Well-Known Member
Apr 25, 2014
3,129
365
83
Switzerland
#10
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 :)
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.

I will likely eventually build a passive xover that will replace the miniDSP but it is just too easy for developing not to use one! I also have a Behringer DCX2496 that I could have used but it would never be a permanent solution whereas the miniDSP could conceivably be a final stop. I might also, for better FR control, use my Behringer DEQ2496 digital in/digital out prior to going into the miniDSP and using it only as a raw crossover and driver level matcher...let's see. Going the miniDSP route all digital means I needed two DACs (three if I ever go three way!) and two amplifiers (still shopping for the "final" amp for the horn).

The little Metrum DAC I am using on the mid/bass driver is really quite good considering how low money it cost me! The Monarchy is simply a great DAC that will go toe to toe with 5K+ DACs any day of the week...love it.
 

morricab

Well-Known Member
Apr 25, 2014
3,129
365
83
Switzerland
#11
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).
 
Mar 23, 2015
2,231
629
113
UK
#12
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?
 

morricab

Well-Known Member
Apr 25, 2014
3,129
365
83
Switzerland
#13
Hi,

Thanks for the detailed response - it makes sense.

I thought the Aries horn is a back loaded design?
It is but it is a pretty long horn (over 3 meters). Also, the construction is quite difficult as there are no sharp corners...it is all machined as a smooth folded contour. I don't have the tools to make something so nice like that...many speaker builders do not have it either. Any horn I would build would be compromised too much and so a TQWT is a good and relatively simple compromise...
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. A place where audiophiles and audio companies discuss existing and new audio products, music servers, music streamers and computer audio, digital to audio convertors (DACS), turntables, phono stages, cartridges, reel to reel, speakers, headphones, tube amplifiers and solid state amplification. Founded in 2010 What's Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals we enjoy learning about new things and meeting new people and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing