I may have asked this already but....are the felt strips in the back of the panels meant to dampen the resonance by obstructing the sound waves or by spanning the distance between louvers to diminish resonance? It is generally agreed that the felt reduces top end. If you were to cut holes in the felt and reapply it in the same configuration, do you think the holes would allow for more top end while not impacting the dampening effect?
I think holes would allow the air to escape straight out and reduce the damping by an amount proportional to the amount of felt removed. Have a look at the measured responses from bolserst's post: Acoustat Answer Man is here
So it seems if you want to increase top end you would need to add damping. I've never considered my Monitor 3 to be lacking at the top. FR is very linear from 10k up. The room has a huge influence on how they end up sounding. Mine are about 3.5ft. from the back wall. They lean back about 3deg. The more upright, the more bass heavy they are.
I'm guessing that angling them back would even out the bass response since you'd spread the frequencies of cancellation over the range of distances to the back wall. I'm wondering about this with respect to my upcoming 2+2 DIY frames. Also, angling back would aim the center of the lower panel at the ears instead of the top near the gap between the vertical stack. How the angle affects the reflection off of the ceiling is another concern though.
I find myself wondering about the goal and how the speakers are being used. Do you really just want a little more treble or are you looking for improvement in detail retrieval or imaging?
Removing the felt would allow more high frequency output to the rear of the speaker. In a live room, that would make more difference than in a more absorptive one. The high frequency output to the front will be minimally affected, but top end detail may improve and the overall room balance could shift.
But, any change to the felt is a significant change to the design, and would require trial and error and accurate measurements to do well, especially if you're using the panels full range.
If it really is just a simple boost in the treble that's desired and you've already tried changes to speaker angles, some careful equalization or even a tweak to a tone control will likely be less detrimental than changes to the felt damping.
Removing the felt would allow more high frequency output to the rear of the speaker. In a live room, that would make more difference than in a more absorptive one. The high frequency output to the front will be minimally affected, but top end detail may improve and the overall room balance could shift.
But, any change to the felt is a significant change to the design, and would require trial and error and accurate measurements to do well, especially if you're using the panels full range.
If it really is just a simple boost in the treble that's desired and you've already tried changes to speaker angles, some careful equalization or even a tweak to a tone control will likely be less detrimental than changes to the felt damping.
My listening(ears) position is dead center to the panels vertically as their trajectory face upward just right. I sit 12ft. away with distance to wall behind my position, and speakers to front wall being equal. So symmetry is perfect.
The Otl servos have HF boost for room eq and I do have them up I would say no more than 2db, carpet on the floor, typical living room.
The Otl servos have HF boost for room eq and I do have them up I would say no more than 2db, carpet on the floor, typical living room.
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I mistakenly thought the felt was in place to dampen grid resonance, not diaphragm resonance. This is why I felt holes might work.
I have no lack of top end now that I have added a super tweeter to the system. The difference is quite substantial and can be dialed in to suit taste or counter room anomalies. I thought everything sounded amazing until I added the super tweeter. It really exposed what the speakers were lacking.
I have no lack of top end now that I have added a super tweeter to the system. The difference is quite substantial and can be dialed in to suit taste or counter room anomalies. I thought everything sounded amazing until I added the super tweeter. It really exposed what the speakers were lacking.
I’m old. Haha. This super tweeter crosses over at adjustable increments of 8k,10k,12k,14k, and 16k. It also has 3 levels of attenuation to dial it in.
Aperion Audio Aluminum Ribbon Super Tweeter Speaker Pair Gloss Black
Aperion Audio Aluminum Ribbon Super Tweeter Speaker Pair Gloss Black
My hearing falls off sharply at around 11khz. It's interesting that compensating for my hearing loss is not at all satisfying. It doesn't sound right unless I match it to my natural hearing ability. I suppose if pretty well everything wasn't in by then it would be a different story.
Btw, I just got zapped tweaking the angle of my speakers. Feels like when you get zapped from the coil on your car/motorcycle ignition. Ouch
Btw, I just got zapped tweaking the angle of my speakers. Feels like when you get zapped from the coil on your car/motorcycle ignition. Ouch
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Thanks, some of the weak points I see are the possible use of tantalum caps in the circuit. Also, a protection and delay circuit would be nice given the fixed bias scheme. Should the -150 drop out, the output tube current would go thru the roof. Has anyone made the fixed bias adjustable and added a resistor at the cathode for measurement? Also, with the 150v available, it seems replacing the phase inverter/eq opamps at the input would be a nice upgrade. I don't mind the discrete driver but opamps sound horrible to me. I might try to load this into LtSpice and try some experimenting..
Any other ideas to make this amp more reliable? Maybe a different output tube like a PL509?
Any other ideas to make this amp more reliable? Maybe a different output tube like a PL509?
