Just for laughs and giggles - I popped the backs of my 10.3m pensils, removed all the stuffing. The bass response had definitely improved volume wise, the sound in general terms feels more free, but for some reason the quality of sound stage has noticeably reduced with the speakers being much more noticeable as the emitting sources.
The more I listen the less I like it - stuffing at the ready.
The more I listen the less I like it - stuffing at the ready.
It depends.
For 2-ch, I sit at the apex if an 8'x8'x8' triangle. On axis is 30* from the wall. I toe in from there ~10*, so the speakers are toed ~40* from the wall.
For HT, the speakers are square with the wall. At the main listening position (my chair) the speakers are ~15* toed-out. Since I am somewhat off center, one speaker is louder than the other, which centers the image.
Bob
A model proposed by Mark some time ago, and wistfully anticipated by some members of the club, but it was well back in the queue - IINM, the recent 2 revisions to the 10cm drivers were well underway before Mark's little set back.
As he's currently in the middle of a cross country trek (visiting the Wet Coast this coming weekend as a matter of fact) - he might not be able to immediately respond to the query.
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Your description is very close to what I noticed. Funny you should mention, but I also found an impact on the imaging. I clearly noticed it but didn't give it much thought at the time because I had no rationale for why it would have changed. But I couldn't live with the 'dead bass' of the original level of stuffing. I guess a tradeoff has to be made and I think I found what I like by using half the stuffing I started out with, probably close to 0.3lb to 0.5lb/cu.ft. which is 1/3 of what the specifications called for.
Bob - for your own listening pleasure, when you apply mild DSP to the A10.3, how much correction are you applying - is it equivalent to around 3dB of BSC for example ?
And if your client wanted to have some BSC would you also apply a zobel to the A10.3 ?
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More like 3dB/octave below 100Hz. I also have a 48dB/octave high pass at 30Hz.
No. a passive LR filter will do all that is necessary. Touch up with toe-in.
Bob
Having just spent a couple of hours listening to my speakers, more lightly filled and bass improved, I am aware that the soundstage is still less that it was when they were filled close to the recommended amount.
Any of you boffins care to speculate why the soundstage is better the more filling there is? And - simple physics would indicate that the LF would be the least affected by the increased amount of fill, so why such a large drop off in LF when adding a few extra gm of filling?
And what was the design choice for filling them to such a point that the LF suffers?
Or perhaps señor big un and myself are alone in these observations.
Any of you boffins care to speculate why the soundstage is better the more filling there is? And - simple physics would indicate that the LF would be the least affected by the increased amount of fill, so why such a large drop off in LF when adding a few extra gm of filling?
And what was the design choice for filling them to such a point that the LF suffers?
Or perhaps señor big un and myself are alone in these observations.
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First off, I think the modelling is done for maximally flat response and the models (MJK) may not be calibrated for the effects of the stuffing material we use in our builds. I've looked on some other forums and there seems to be a consistent message - nobody likes the level of stuffing recommended and universally pulls a lot of it back out.
I assume imaging is about phase coherence between the signal coming in to the speakers and the sound that comes out. I could envisage there being an issue with reflections back through the cone so it would be preferable to keep more of the stuffing behind the driver. But I wonder if the stuffing also affects the impedance of the box experienced by the cone and a lumpier impedance might disturb the phase coherence.
It's an unfortunate tradeoff - perhaps the only option is to stuff more heavily and 'fix' the bass with a filter. Somehow that doesn't feel like the solution I want.
Well I've progressed to some heavy sanding with coarse grit along all the end grain to get things level and smoothed off a bit. This stage seems to generate a lot of dust.
... I also seem to have lost one of the bezels which theoretically should be in my basement but is probably hiding with all those pens that never get found. This minor mishap could prove quite inconvenient...
I assume imaging is about phase coherence between the signal coming in to the speakers and the sound that comes out. I could envisage there being an issue with reflections back through the cone so it would be preferable to keep more of the stuffing behind the driver. But I wonder if the stuffing also affects the impedance of the box experienced by the cone and a lumpier impedance might disturb the phase coherence.
It's an unfortunate tradeoff - perhaps the only option is to stuff more heavily and 'fix' the bass with a filter. Somehow that doesn't feel like the solution I want.
Well I've progressed to some heavy sanding with coarse grit along all the end grain to get things level and smoothed off a bit. This stage seems to generate a lot of dust.
... I also seem to have lost one of the bezels which theoretically should be in my basement but is probably hiding with all those pens that never get found. This minor mishap could prove quite inconvenient...
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We never use then so i have lots of spares.
BTW, we did not find out Pensil10.3 lacking in bottom.
dave
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I'm still looking for that Bezel - haven't give up yet but it won't be long !
Quick picture of my listening tests. As of today, the speakers have gone away to their new owner who wants to paint them with some special furniture restorers chalk-paint and wax finish. I hope to be able to report further listening experience once they are finished. They will be connected to an SV811 SET when ready....
Quick picture of my listening tests. As of today, the speakers have gone away to their new owner who wants to paint them with some special furniture restorers chalk-paint and wax finish. I hope to be able to report further listening experience once they are finished. They will be connected to an SV811 SET when ready....
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Very nice mate, how many hours did you have on them before they left?
And I was wondering what fill you used in the back? I used a hollow fibre toy stuffing, though it has a tendency to clump and I'm sure that's not ideal.
I also have a couple of bezels if your stumped.
Regarding the bass response, I have been amazed at how much difference the quantity and position of the stuffing makes. I also played with the polarity, and actually found very little change in the quantity or quality of bass response, but supprisingly when out of phase, the soundstage became extraordinary. Not entirely right, if you know what I mean, but some instruments sounded like they were behind me.
This leads to a question - can the speaker placement and room shape create artifacts that lead to poorly phased sound within what should be the sweet spot?
And I was wondering what fill you used in the back? I used a hollow fibre toy stuffing, though it has a tendency to clump and I'm sure that's not ideal.
I also have a couple of bezels if your stumped.
Regarding the bass response, I have been amazed at how much difference the quantity and position of the stuffing makes. I also played with the polarity, and actually found very little change in the quantity or quality of bass response, but supprisingly when out of phase, the soundstage became extraordinary. Not entirely right, if you know what I mean, but some instruments sounded like they were behind me.
This leads to a question - can the speaker placement and room shape create artifacts that lead to poorly phased sound within what should be the sweet spot?
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The drivers had about 250 hours on them when they left me. I expect I'll have a chance to hear them again in a week or so at their final home. For stuffing, I used some Quilt Batting used for making... quilts. It's polyester, density is around 2oz per sq. yard. I don't know who makes it as it was private labelled for Len's Mill Stores in Ontario. This stuff is not clumpy, it comes in sheets and is self supporting. I cut it up into strips and distributed it about - the density is fairly light. I reckon I could have squeezed in about the weight called for in the pdf design document but it would have been very tight and in my trials I settled on about 1/4 to 1/3 the recommended weight. It may yet get adjusted in it's final home of course.
I didn't try different polarities but I do remember the most esoteric sound I ever heard was a mono source into two speakers, one wired out of phase with respect to the other. Despite the mono source, the sound seemed to come out of all over the place, it was something to experience ! Years ago when I bought my stereo speakers (PMCs) and amplifier (Bryston) I went to the shop to finalize my choice. My father was visiting me at the time and so he came along. After a bit of listening the salesperson noticed both speakers were wired out of phase and switched them around. My father and I were both surprised that we could hear a clear change in the sound. It was subtle but the correct phase sounded better.
So - about my SET. Well the SV811 is not mine but my friends. I don't know how much it puts out but it sure puts out enough. This tube is designed for Class A2 and I believe 20W+ is normal. This isn't a beginners amplifier, we're talking multiple bias supplies, Thoriated heater, interstage transformer with high transconductance driver tube, power supply on separate chasis, chunky output transformers. It's also an expensive amplifier to build.
My current SET is based on the 6H13C which is the russian equivalent to 6AS7G with 6SN7 driver. It has a low gain and I probably get 2W+ out of it. It plays loud enough but the volume is usually cranked past half-way when it's being used.
I am going to be constructing a new SET for myself. It will be based on a direct driver from a high gain 12AX7LPS into a 2A3. No coupling cap or interstage transformer, just a piece of wire. I believe the approach I'm taking represents the pinnacle of 2A3 amplifier design (of course I would say that !) but the project keeps getting stalled whilst I build other things. There's more about it here:http://www.diyaudio.com/forums/tubes-valves/221739-nice-little-valve-amplifier.html
I didn't try different polarities but I do remember the most esoteric sound I ever heard was a mono source into two speakers, one wired out of phase with respect to the other. Despite the mono source, the sound seemed to come out of all over the place, it was something to experience ! Years ago when I bought my stereo speakers (PMCs) and amplifier (Bryston) I went to the shop to finalize my choice. My father was visiting me at the time and so he came along. After a bit of listening the salesperson noticed both speakers were wired out of phase and switched them around. My father and I were both surprised that we could hear a clear change in the sound. It was subtle but the correct phase sounded better.
So - about my SET. Well the SV811 is not mine but my friends. I don't know how much it puts out but it sure puts out enough. This tube is designed for Class A2 and I believe 20W+ is normal. This isn't a beginners amplifier, we're talking multiple bias supplies, Thoriated heater, interstage transformer with high transconductance driver tube, power supply on separate chasis, chunky output transformers. It's also an expensive amplifier to build.
My current SET is based on the 6H13C which is the russian equivalent to 6AS7G with 6SN7 driver. It has a low gain and I probably get 2W+ out of it. It plays loud enough but the volume is usually cranked past half-way when it's being used.
I am going to be constructing a new SET for myself. It will be based on a direct driver from a high gain 12AX7LPS into a 2A3. No coupling cap or interstage transformer, just a piece of wire. I believe the approach I'm taking represents the pinnacle of 2A3 amplifier design (of course I would say that !) but the project keeps getting stalled whilst I build other things. There's more about it here:http://www.diyaudio.com/forums/tubes-valves/221739-nice-little-valve-amplifier.html
12AX7's have all the drive of a wet noodle.
Maybe fine for an EL84, even a 12AT7 would be a better choice. This is just my opinion of course.jeff
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