Something stirs in the Undergrowth

Dedicated to those large boxes at one end of the room
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BudP
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#1396

Post by BudP »

If you look closely you will see that the TL is a continuous slant, just one angled board, that the drivers are working into a variable density for pressure but the equivalent of a long load line due to the angled inner partition. The exit is to the rear of the faceted front and as it is an inverted phase it is audibly in phase with the back side of the Eminence driver. Since the TL drivers are long throw devices working in direct opposition within a confined space, their instantaneous overpressure capability is quite high and they are able to force significant pressure waves out of that small opening, which is full panel width, just narrow in height. Being at the floor level the port has significant advantages in coupling into the room.

No port chuff at all and pants flapping power into mid 30 Hz with modest energy down into the low twenty Hz region. Loaded into a fireplace with a room that has a significant volume adder in a two, 1/2 level set of stairs opposite the fireplace wall, the bass is both deep and powerful. No overhang, no ringing, just fast response, delicate nuance support and reasonably efficient. Here is a copy of the pic.
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Lowther Delta 8 Open Baffle small.jpg
"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
steve s
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#1397

Post by steve s »

Thats an interesting set up bud.
I would expect to hear a nice compromise of smallish size and quality with those , i like them...
which lowthers are you using ?
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BudP
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#1398

Post by BudP »

Thanks for your interest Steve,

The Lowthers are PM6A 16 ohm silver voice coil. That to obtain the 3mm xmax Jon Ver Halen said was mandatory for open baffle. I now wish I had opted for the 8 ohm items, as the voice coil weight is actually audible. Gary Koh of Genesis commented that they sounded like they have a gravity problem. The crossover is a series item at 300 Hz and I will never return to parallel crossovers. Both 8 inch drivers have zobels hidden in the spine of the upright baffle brace.

The open baffle was an experiment to see if I could control front to back suck out using a minimal baffle size. The EnABL pattern applied to the baffle thickness edge accomplished the needed segregation. The null zone does not make it past the edge of the baffle so these things are close to omnidirectional and very coherent in time structure. An interesting oddity is when standing behind them, facing the listening area, the audible illusion is that of being on the back side of whatever performance is provided. As you walk past into the more normal listening area, the front half of the sound just paints itself in place, but you are still aware of the back side.

The attached FR plot is unsmoothed and was to be used to develop a notch filter for the 7.5 to 10 kHz Lowther bump. However, I figured out how to control the whizzer cone back side emissions and the bump has almost gone away without the notch filter.. I am also experimenting with a piezo film tweeter from the old Pioneer speaker systems, as a slant in fill for the top octave. Not quite where I want it yet ,but very close. When friend Dave Rosgard can bring his test rig back I will post a new FR graph with all curent changes.
Attachments
Sys_Zbl.jpg
"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
waveguide
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#1399

Post by waveguide »

BudP wrote:Thanks for your interest Steve,

The Lowthers are PM6A 16 ohm silver voice coil. That to obtain the 3mm xmax Jon Ver Halen said was mandatory for open baffle. I now wish I had opted for the 8 ohm items, as the voice coil weight is actually audible. Gary Koh of Genesis commented that they sounded like they have a gravity problem. The crossover is a series item at 300 Hz and I will never return to parallel crossovers. Both 8 inch drivers have zobels hidden in the spine of the upright baffle brace.

The open baffle was an experiment to see if I could control front to back suck out using a minimal baffle size. The EnABL pattern applied to the baffle thickness edge accomplished the needed segregation. The null zone does not make it past the edge of the baffle so these things are close to omnidirectional and very coherent in time structure. An interesting oddity is when standing behind them, facing the listening area, the audible illusion is that of being on the back side of whatever performance is provided. As you walk past into the more normal listening area, the front half of the sound just paints itself in place, but you are still aware of the back side.

The attached FR plot is unsmoothed and was to be used to develop a notch filter for the 7.5 to 10 kHz Lowther bump. However, I figured out how to control the whizzer cone back side emissions and the bump has almost gone away without the notch filter.. I am also experimenting with a piezo film tweeter from the old Pioneer speaker systems, as a slant in fill for the top octave. Not quite where I want it yet ,but very close. When friend Dave Rosgard can bring his test rig back I will post a new FR graph with all curent changes.
It looks alright and I bet it sounds great for the size, but do you really make and sell i/v transformers. I tried your email but no respnse. I may buy the mumetal cores and make my own if you do not makethem anymore. Thanks
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BudP
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#1400

Post by BudP »

Waveguide, I must admit to being acronym challenged. What is an I/V transformer please? We do make a number of signal level nickle core devices, ranging from 600 ohm to 2800 ohm in effective primary impedance supported through primary inductance. I have attached a data sheet of our most popular 1kZ ohm DAC buffer device in case that is what you are after.

The email thing concerns me, hpurvine@gmail.com is what I use, though the same at AOL will also get to me.
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Dac Buffer 10148 Data Sheet 01.pdf
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"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
waveguide
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#1401

Post by waveguide »

BudP wrote:Waveguide, I must admit to being acronym challenged. What is an I/V transformer please? We do make a number of signal level nickle core devices, ranging from 600 ohm to 2800 ohm in effective primary impedance supported through primary inductance. I have attached a data sheet of our most popular 1kZ ohm DAC buffer device in case that is what you are after.

The email thing concerns me, hpurvine@gmail.com is what I use, though the same at AOL will also get to me.
Hi BudP.

Sorry about the digression from the lovely speaker, which seems ideal fora smaller system where very fine articualtions is required with real bass. I like TLs.

The i/v bit is related to the DAC chip being a left and right channel output giving an audio output delivering current or voltage to a following high impedance op amp or valve prepamp. Sowter make some using 80%nickel cores with appropriate i/put and o/put impedances with wide band width. I think the 600Zohm one is probably fine, but I would find a 2:1 gain even better. Thanks for the data sheets.
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#1402

Post by chris661 »

BudP wrote: No port chuff at all and pants flapping power into mid 30 Hz with modest energy down into the low twenty Hz region. Loaded into a fireplace with a room that has a significant volume adder in a two, 1/2 level set of stairs opposite the fireplace wall, the bass is both deep and powerful. No overhang, no ringing, just fast response, delicate nuance support and reasonably efficient. Here is a copy of the pic.
Cool, what're the bass drivers?

Chris
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BudP
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#1403

Post by BudP »

Wave, we need to harmonize our terminology. In transformer parlance, 2:1 means a step down in voltage delivered by the secondary. Is this your intended meaning?

As a further thought topic, transformers do not provide a load to follow on circuitry, the impedance they do provide to things like back emf etc are reflections of the impedance generated between the primary inductance and the device using that primary inductance as it's load. The 600 ohms, or i k ohms, do not refer to primary DCR, they refer to the impedance provided by the primary inductance at the lowest frequency of interest. Thus 1:1 1:2 2:1 or 4:1 all have the same primary impedance, or in more practical terms, the same number of turns, core area and permeability and it is the variance in secondary turns that creates the trade off in voltage for current. I will warn you that a step up transformer provides an increasingly difficult load for the device driving the primary, the eventual load capacitance seen by the secondary is multiplied by the square of the turns
"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
waveguide
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#1404

Post by waveguide »

BudP wrote:Wave, we need to harmonize our terminology. In transformer parlance, 2:1 means a step down in voltage delivered by the secondary. Is this your intended meaning?

As a further thought topic, transformers do not provide a load to follow on circuitry, the impedance they do provide to things like back emf etc are reflections of the impedance generated between the primary inductance and the device using that primary inductance as it's load. The 600 ohms, or i k ohms, do not refer to primary DCR, they refer to the impedance provided by the primary inductance at the lowest frequency of interest. Thus 1:1 1:2 2:1 or 4:1 all have the same primary impedance, or in more practical terms, the same number of turns, core area and permeability and it is the variance in secondary turns that creates the trade off in voltage for current. I will warn you that a step up transformer provides an increasingly difficult load for the device driving the primary, the eventual load capacitance seen by the secondary is multiplied by the square of the turns
Hi BudP

Yeah I should ahve written 1:2 1:1 would do but 1:2 would be better.

The CS4397 chip will need something resistive to work into as well as Z. There iwll be no DC on the primary as the 3.3volts on input output cancels out. FR would be up to 50KHz within 1 dB also with mild droop at 20Hz no issue. You will know what will be best for a voltage out DAC chip and can advise me.

Thanks
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BudP
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#1405 CSS SDX7 woofer specs

Post by BudP »

Chris, I have attached a set of specs for the drivers. IF you want the CSS PDF document please email me.
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SDX specs.txt
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waveguide
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#1406

Post by waveguide »

waveguide wrote:
BudP wrote:Wave, we need to harmonize our terminology. In transformer parlance, 2:1 means a step down in voltage delivered by the secondary. Is this your intended meaning?

As a further thought topic, transformers do not provide a load to follow on circuitry, the impedance they do provide to things like back emf etc are reflections of the impedance generated between the primary inductance and the device using that primary inductance as it's load. The 600 ohms, or i k ohms, do not refer to primary DCR, they refer to the impedance provided by the primary inductance at the lowest frequency of interest. Thus 1:1 1:2 2:1 or 4:1 all have the same primary impedance, or in more practical terms, the same number of turns, core area and permeability and it is the variance in secondary turns that creates the trade off in voltage for current. I will warn you that a step up transformer provides an increasingly difficult load for the device driving the primary, the eventual load capacitance seen by the secondary is multiplied by the square of the turns
Hi BudP

Yeah I should ahve written 1:2 1:1 would do but 1:2 would be better.

The CS4397 chip will need something resistive to work into as well as Z. There iwll be no DC on the primary as the 3.3volts on input output cancels out. FR would be up to 50KHz within 1 dB also with mild droop at 20Hz no issue. You will know what will be best for a voltage out DAC chip and can advise me.

Thanks
With more good info from Budp I am going to try one of his great traffos to see if it suits my system. I hope he can find one for me to try, other wise I am happy to wait 8 weeks.
P.H.
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#1407

Post by P.H. »

BudP wrote:I now wish I had opted for the 8 ohm items, as the voice coil weight is actually audible. Gary Koh of Genesis commented that they sounded like they have a gravity problem.
No Lowther driver has a voice coil that is suitable for proper midrange and above midrange reproduction. Everything above 0,18-0,20 grams (including the weight of the former material) is not suitable. If it weights more - you will always feel/hear that gravity problem to some extent, of course depending on how high your reference points are.
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Greg
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#1408

Post by Greg »

I've just realised that this thread has now been running for nearly six years
:roll:

Mark, surely by now you are frustrated at not yet coming to a final solution?
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IslandPink
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#1409

Post by IslandPink »

Yes ! ( although it's been a very interesting journey ).
But I have a pretty good plan of what to do now :
Supravox 285GMF + Fostex 208Ez on Quasar-clone baffle ( perspex front, birch-ply sides ) with series crossover , for bass and mids up to about 800 or 1000Hz . Low-pass in the amp ( GK-71 amp ? ) for the upper low-pass at 800 .
Then ; upper amp ( 2A3 most likely ) driving Radian745Be/Azura and a tweeter ( G3 ribbon or B&C bullet ) from 800 or 1000Hz upwards. Radian will roll-off naturally, tweeter comes in with 1st-order quite high, eg. 8-10kHz.
If I need a sub, I have an IPL one, for the 40Hz & below area.

All I need to do now, is get rid of some speakers ( easier said than done :roll: ). I've got a house full of speakers and boxes, and need to raise some funds.

Ps. I'm off for a week now in the Lakes , to chill out . I'll comment more when I get back .
"Once you find out ... the Circumstances ; then you can go out"
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rowuk
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#1410 Opinion based on "air"?

Post by rowuk »

A pretty bold statement. I would really like to hear the rationale behind it - if there is any at all. Perhaps it is simply based on a definition of midrange that is "unique to P.H."?

If ones reference points are truly high enough, we realize that it is not the raw ingredients, rather how the cook prepares them. The assumption that if one disagrees, their reference points are not high enough is a big danger in web blogging. A pretty stupid assumption considering that our talents and capabilities vary from musician to background music listener and from engineer to "challenged with a simple AM radio".

What one particular mix of ingredients "needs" can often be very diametrically opposed to another mix. This is very visible in the amount of top musicians using and being happy with small Bose systems. They listen VERY analytically and get all of the information that they need for a satisfying experience - or musical analysis. Genuine audio people prefer dramatically different systems and based on many of the online comments, are not happy with just about any topology. Who is more "right"?

I simply think that there is little correlation between specs and real SOUND QUALITY.

Headfi defines it like this(http://www.head-fi.org/a/describing-sound-a-glossary)
Midrange (Mids) - The audio frequencies between about 250 Hz and 6000 Hz.

Considering the amount of acoustic power with serious music required at 250 Hz, I think the voice coil weight claim is rubbish. The Lowthers are LF challenged because they ARE too light and have a very high BL, which is why a properly designed LF like Buds is a very intelligent move. I am not sure, considering the sound of the entire Genesis speakers series, that Garys comment about "gravity" should get a lot of concern.

If there is an issue with gravity, I would think that the reason is because the ULF extension does not match the UHF extension. To get proper anchoring, both ends need to line up. 50Hz cutoff with 35000 top end often sounds like it will topple. 20Hz with only 15K extension may sound "anchored", but inflexible, not "tuneful".

The gravity issue may also be a function of the higher order cutoff of the transmission line lower knee and the room. Sharp cutoffs when music or room information is present are always audible. A simple test might be a big cap to simulate a 6dB/8va rolloff starting at 50 or 60 Hz - just to test the concept.
P.H. wrote:
BudP wrote:I now wish I had opted for the 8 ohm items, as the voice coil weight is actually audible. Gary Koh of Genesis commented that they sounded like they have a gravity problem.
No Lowther driver has a voice coil that is suitable for proper midrange and above midrange reproduction. Everything above 0,18-0,20 grams (including the weight of the former material) is not suitable. If it weights more - you will always feel/hear that gravity problem to some extent, of course depending on how high your reference points are.
Whenever I feel blue, I start breathing again.
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