In previous article i mentioned i like the powerfull sound from horn loudspeakers and presented a mid-bass horn system. I will continue showing how it was built and show frequency response measurements and how i integrated the ALTEC 511B horn clone and 3 inch compression driver.
The 10 incher driver i used was a 6366 i worked on with HiPower. Other 10 inch drivers that can be used:
The mid bass construction is made of MDF of 20mm thickness and 8mm thickness. Below you can see some pictures with the construction:
The main problem with front horns loading cone drivers is high frequency response. Especially if the cone is large in diameter. You can have a strong motor, a very light cone, and a low inductance and still have a poor high frequency response. That is because of the air trapped between the cone and the horn throat.
This is similar to compression chamber in high frequency compression drivers. What happens is that at low frequencies all the air is pushed to the horn through so air behaves like a mass, similar to the air in a bass reflex port. At high frequency however not all the air from that volume gets into the throat. At some point is starts to be compressed and thus it acts like a compliance. This is a basic acoustic low pass filter and it’s the main culprit for high frequency response roll off.
This is very important when front loading a fullrange driver. You can only use minimal compression ratio so that most of the radiating surface of the driver is in the horn throat.
Observing this i constructed a 10 inch driver with a 4 inch voice coil so that the cone has a flatter profile and be closer to the horn throat.Took some experimenting but i went for a softer suspension and a high BL of 24Tm. Below you can check some pictures:
High Frequency response did increase and the driver had tremendous force but unfortunately i built just one. Not only high frequency improved but the overall sensitivity improved due to the stronger motor. The diameter of the magnet ring is 200mm and the system had a Qts of 0.14!
Below you can see two on axis frequency response curves for the horn using 2 6366 10 inch units. The black trace shows response with the back wall installed and the blue one is with the back chamber left open.
For high frequency i used a large format compression driver with a 3 inch diaphragm made from titanium and mylar surround. The driver can go to 700Hz fairly easily and has a pretty good high frequency response. It is based on 8074 from Hipower but modified the design for mylar surround and different phaseplug.
I used an active crossover to setup the system, using a first order filter at 3kHz managed to get an acoustic xover point around 700Hz. Horn cut at 600Hz 12db/octave. Here is the on axis system response:
As this is an old project of mine i am still trying to find the detailed schematic of the horn through my files. I will do another followup once i find them.
Thank you for visiting.