Afterr experiencing full 1.5 months of full range sound with the Metronome i had the following apprehensions,
1. If the full-range is allowed to do more low frequency duty thenit adds to the mid-range colouration. This i believe is due to increased cone movement that is required for the low frequency reproduction. This imo adds coloration to the overall mid-range presentation.
2. Also in this particular fostex driver above 5KHz to 6KHz the mid-high and high freq is produced more by the Whizzer cone. This whizzer is integrated as part of the main cone by applying some kind of glue near the voice coil. The movement of the whizzer happens along with the main cone again causing sever col0ration and harshness to the mid-highs and highs. This cause the overall sound stage to be not very smooth than required.
I tried compensating the whizzer cone movement by adding some damping material behind the whizzer cone and main cone but that also damps the main cone movement reducing the low end extension.
To reduce the cone break-up a bit at the mid-highs i tried doping the cone with some light 'Multani Mitti' coat (fuller's earth). This reduced the mid-highs quite a bit and reduced the harshness too. But this removed also the zing and energy from the music.
So what were the other practical options.
i) I considered removing the whizzer cone altogether and adding a diy phaseplug to remove the cavity resonance caused by the cavity left between the magent pole and the voice coil. Notputting the phase plug causes the driver to whizzle a lot beyond tolerance.
ii) Remove the fostex from low frequency duty and add a sub-woofer for low-end support. This modificiation will cause lesser movement of the main cone as they do not have to move a lot for low frequency reproduction. I did not want to introduce any passive cross-over component on the mid-range driver and hence decided to do this by over-damping the enclosure. The
overdamped enclsoure now made the Metronome to behave more like a Aperiodic enclosure rather than a ML TL enclousre. This significantly tightened the mid-range making it crisp clearwith clean smooth sound stage. Also i removed my compensation network as i wanted the Fostex to roll-off
natrually.
I have measured last week the Fostex with the phase plug and no whizzer and the roll-off happens smoothly around 7KHz onwards. There are some phase changes at around 8.5KHz and 12KHz looking at the minimum phase graphs and this i need to re-validate.
Now there is a huge gap in the top-end from 7KHz till 20KHz which needs to be addressed. I thought of many options of using a tweeter - dome, ribbion and finally settled with the Ahuja Piezo tweeter. This tweeter works exceptionally well beyond 4KHz onwards and integrates magnificently well with the fostex if implemented correctly. I will be using this piezo tweeter from 4KHz and beyond and will integrate it with the Fostex full ranger. Currently they are under test and listen mode.
To address the low-end, I borrowed my elder brothers passive TL sub which i had build almost 10 years ago for use in his HT setup. This rescued the day for me as the Fostex has now been rolled off at around 150Hz to 200Hz and it definetly needed a low end support from other source.
Adding stuffing to the Metronome caused the phase curve to intersect at zero degrees for the driver, system and the terminus. This allowed me to operate the subwoofer at 0 deg mode.
Now i am fully convinced about the beauty of the cross-over less full-range speaker with the low-end been handled by a active TL sub. There is no cross-over for the Fostex and the piezo tweeter just has a parallel resistor for level matching with the Fostex with no passive components.
So how does the above translate to subjective listening. I would just add one line - the most satisfying experience ever had in my entire life.
I also now realize what our FM Sumanta always felt, i quote him during his conversations with me. He says - its immaterial of what 'Brand' of driver you buy, its important how you implement them in the final outcome.
As for me - only using the Fostex and live with its laurels did not appeal me. I took the risky approach of almost destroying the driver with my adventures which gave me a couple of sleepless nights and some nightmares too. After systematic approach of the issues and trying to solve the issue by practical and more economical means was the solution. The solution need not be very expensive or complex but rather mere common-sense at the end of the day.
I am sure the Fostex can easily be replaced by other stock drivers like Queena or Boston Acoustics which are available att 1/50th the cost, but that is for an another day at work.
Thanks for looking.
1. If the full-range is allowed to do more low frequency duty thenit adds to the mid-range colouration. This i believe is due to increased cone movement that is required for the low frequency reproduction. This imo adds coloration to the overall mid-range presentation.
2. Also in this particular fostex driver above 5KHz to 6KHz the mid-high and high freq is produced more by the Whizzer cone. This whizzer is integrated as part of the main cone by applying some kind of glue near the voice coil. The movement of the whizzer happens along with the main cone again causing sever col0ration and harshness to the mid-highs and highs. This cause the overall sound stage to be not very smooth than required.
I tried compensating the whizzer cone movement by adding some damping material behind the whizzer cone and main cone but that also damps the main cone movement reducing the low end extension.
To reduce the cone break-up a bit at the mid-highs i tried doping the cone with some light 'Multani Mitti' coat (fuller's earth). This reduced the mid-highs quite a bit and reduced the harshness too. But this removed also the zing and energy from the music.
So what were the other practical options.
i) I considered removing the whizzer cone altogether and adding a diy phaseplug to remove the cavity resonance caused by the cavity left between the magent pole and the voice coil. Notputting the phase plug causes the driver to whizzle a lot beyond tolerance.
ii) Remove the fostex from low frequency duty and add a sub-woofer for low-end support. This modificiation will cause lesser movement of the main cone as they do not have to move a lot for low frequency reproduction. I did not want to introduce any passive cross-over component on the mid-range driver and hence decided to do this by over-damping the enclosure. The
overdamped enclsoure now made the Metronome to behave more like a Aperiodic enclosure rather than a ML TL enclousre. This significantly tightened the mid-range making it crisp clearwith clean smooth sound stage. Also i removed my compensation network as i wanted the Fostex to roll-off
natrually.
I have measured last week the Fostex with the phase plug and no whizzer and the roll-off happens smoothly around 7KHz onwards. There are some phase changes at around 8.5KHz and 12KHz looking at the minimum phase graphs and this i need to re-validate.
Now there is a huge gap in the top-end from 7KHz till 20KHz which needs to be addressed. I thought of many options of using a tweeter - dome, ribbion and finally settled with the Ahuja Piezo tweeter. This tweeter works exceptionally well beyond 4KHz onwards and integrates magnificently well with the fostex if implemented correctly. I will be using this piezo tweeter from 4KHz and beyond and will integrate it with the Fostex full ranger. Currently they are under test and listen mode.
To address the low-end, I borrowed my elder brothers passive TL sub which i had build almost 10 years ago for use in his HT setup. This rescued the day for me as the Fostex has now been rolled off at around 150Hz to 200Hz and it definetly needed a low end support from other source.
Adding stuffing to the Metronome caused the phase curve to intersect at zero degrees for the driver, system and the terminus. This allowed me to operate the subwoofer at 0 deg mode.
Now i am fully convinced about the beauty of the cross-over less full-range speaker with the low-end been handled by a active TL sub. There is no cross-over for the Fostex and the piezo tweeter just has a parallel resistor for level matching with the Fostex with no passive components.
So how does the above translate to subjective listening. I would just add one line - the most satisfying experience ever had in my entire life.
I also now realize what our FM Sumanta always felt, i quote him during his conversations with me. He says - its immaterial of what 'Brand' of driver you buy, its important how you implement them in the final outcome.
As for me - only using the Fostex and live with its laurels did not appeal me. I took the risky approach of almost destroying the driver with my adventures which gave me a couple of sleepless nights and some nightmares too. After systematic approach of the issues and trying to solve the issue by practical and more economical means was the solution. The solution need not be very expensive or complex but rather mere common-sense at the end of the day.
I am sure the Fostex can easily be replaced by other stock drivers like Queena or Boston Acoustics which are available att 1/50th the cost, but that is for an another day at work.
Thanks for looking.
