Hi all,
Has anybody every used a driver less than 8" for a transmission line subwoofer? In particular, the Dayton 6.5" woofer - Parts Express #295-306 - but others would be interesting to hear about. Note: the specs are below.
The enclosure will likely be a folded TL with the driver near the top of the front face and the open end of the line wrapped so that it exits out the front just below the driver. The overall height will be about 3 feet with a line length of about 6 feet. This way, it might be useful as a stand for my mains or my surrounds.
I plan to build two so that they can be driven in stereo for music and mono'ed for home theatre. My intention is to drive it with an old Sansui R-70 plugged into my old Teac 2A mixer with a passive band-pass in between (10~150Hz). Someday they may each get a chip amp with a band-pass input buffer.
Thanks in advance...
ensen
Current system for reference:
Sony NC-650V - dvd/cd/sacd
Teac 2A mixer - 6in/4buss
Yorkville YSM-1P active (mains)
Marantz 1530 - driving a pair of...
Tannoy Proto-J passive (surrounds/secondaries)
*****
Dayton 6-1/2" Woofer - Parts Express #295-306
Fully shielded version of the #295-305 features paper cone, treated cloth dustcap and butyl rubber surround.
50 watts RMS/75 watts max
Voice coil diameter: 1-3/8"
Voice coil inductance: 2.40 mH
Impedance: 8 ohms
DC resistance: 7.0 ohms
FR: 33-4,000 Hz
Fs: 33 Hz
SPL: 87 dB 1W/1m
Vas: .78 cu. ft.
Qms: 3.89
Qes: .34
Qts: .32
Xmax: 3.15mm
Has anybody every used a driver less than 8" for a transmission line subwoofer? In particular, the Dayton 6.5" woofer - Parts Express #295-306 - but others would be interesting to hear about. Note: the specs are below.
The enclosure will likely be a folded TL with the driver near the top of the front face and the open end of the line wrapped so that it exits out the front just below the driver. The overall height will be about 3 feet with a line length of about 6 feet. This way, it might be useful as a stand for my mains or my surrounds.
I plan to build two so that they can be driven in stereo for music and mono'ed for home theatre. My intention is to drive it with an old Sansui R-70 plugged into my old Teac 2A mixer with a passive band-pass in between (10~150Hz). Someday they may each get a chip amp with a band-pass input buffer.
Thanks in advance...
ensenCurrent system for reference:
Sony NC-650V - dvd/cd/sacd
Teac 2A mixer - 6in/4buss
Yorkville YSM-1P active (mains)
Marantz 1530 - driving a pair of...
Tannoy Proto-J passive (surrounds/secondaries)
*****
Dayton 6-1/2" Woofer - Parts Express #295-306
Fully shielded version of the #295-305 features paper cone, treated cloth dustcap and butyl rubber surround.
50 watts RMS/75 watts max
Voice coil diameter: 1-3/8"
Voice coil inductance: 2.40 mH
Impedance: 8 ohms
DC resistance: 7.0 ohms
FR: 33-4,000 Hz
Fs: 33 Hz
SPL: 87 dB 1W/1m
Vas: .78 cu. ft.
Qms: 3.89
Qes: .34
Qts: .32
Xmax: 3.15mm
Attachments
I just built a 2 way, using MCM 55-1855 as the bass driver, more similar to Dave's "Little""Snail"
This design was very easy to build (Sunday afternoon) and the bass from these little drivers is amazing, but I don't think it'll do for HT, if you like your sofa to shake.
•Impedance: 8Ù •Input power: 50W, Max 100W
•Sensitivity: 87 ±2db/W/M, •Frequency range: 45~15KHz
•Qts: 0.332
•Qes: 0.370
•Qms: 3.24
•Vas: 0.43 cu. ft.
•Sd: 0.0075m2
•Re: 6.5Ù
•Xmax: 2.2mm
•FS: 45Hz
This design was very easy to build (Sunday afternoon) and the bass from these little drivers is amazing, but I don't think it'll do for HT, if you like your sofa to shake.
•Impedance: 8Ù •Input power: 50W, Max 100W
•Sensitivity: 87 ±2db/W/M, •Frequency range: 45~15KHz
•Qts: 0.332
•Qes: 0.370
•Qms: 3.24
•Vas: 0.43 cu. ft.
•Sd: 0.0075m2
•Re: 6.5Ù
•Xmax: 2.2mm
•FS: 45Hz
Hi x.o
I'm actually trying to get the last octave as the mains already have -3dB of 40Hz. Playing sine waves from my Denon Check CD indicates that 61Hz notes are clear, but only vague "sounds" are coming at 31Hz, which points to the published specs probably being correct.
The goal is to make the -3db point even lower for HT and even some music, especially if I ever end up having that apartment warming party. In particular, there is this one track on a Global Underground CD that does a bass downsweep. I'm curious to know how far it goes.
So, the whole design is about getting more low for less and everything I've read indicates that t-lines are really good at going low. Even lower than the others. The Daytons have lower Fs than other small drivers. By using the smaller drivers, I'm trying to get more from less size. By making the cabinet the size of a speaker stand, I get even more from less. By using two, I hope to get yet more.
An afternoon, you say? I've made the box more complicated by making the top rectangular and the bottom square, so I think I'm in for a bit more "fun."
The top to bottom taper is only external. Internally the line taper is constant from just below the driver right to the opening. The side view shows an aggressive depth taper to offset the widening of the cabinet towards the bottom. On the way back up, the line is parallel in depth to take advantage of the natural taper in the width.
ensen.
I'm actually trying to get the last octave as the mains already have -3dB of 40Hz. Playing sine waves from my Denon Check CD indicates that 61Hz notes are clear, but only vague "sounds" are coming at 31Hz, which points to the published specs probably being correct.
The goal is to make the -3db point even lower for HT and even some music, especially if I ever end up having that apartment warming party. In particular, there is this one track on a Global Underground CD that does a bass downsweep. I'm curious to know how far it goes.
So, the whole design is about getting more low for less and everything I've read indicates that t-lines are really good at going low. Even lower than the others. The Daytons have lower Fs than other small drivers. By using the smaller drivers, I'm trying to get more from less size. By making the cabinet the size of a speaker stand, I get even more from less. By using two, I hope to get yet more.
An afternoon, you say? I've made the box more complicated by making the top rectangular and the bottom square, so I think I'm in for a bit more "fun."
The top to bottom taper is only external. Internally the line taper is constant from just below the driver right to the opening. The side view shows an aggressive depth taper to offset the widening of the cabinet towards the bottom. On the way back up, the line is parallel in depth to take advantage of the natural taper in the width.
ensen.
Hi dave,
I've just glanced at the PDF on Martin's site and it is definitely not bedtime reading. So I will probably end up modifying the design after going through the article without the haze of late night forum play.
Still what I gather so far is that my effective line is about 96" which is just shy of the 102.5" I calculate based on driver Fs=33Hz. I think the actual is 32.8Hz based on some of the PDFs on the Parts Express website.
In any case, there is evidence on
http://www.pmcloudspeaker.com/transmission.html
that building a line shorter than 1/4 wave is okay as long as you stuff it to make it "effectively" longer. I read this somewhere, but cannot recall where right now.
I took rough measurements of the pic based on the monitor shown (DB1S) and the physical dimensions published in the specs - a reverse engineering trick I learned from recumbent bike building. So, even though the enclosure shown might have an effective line length of almost 5 ft, the actual physical line is only about 3.5 ft. I'm hoping it will be possible to stuff the 6 ft line enough to make it act like a longer line. If needed, I still have the option of making the line go all the way around the back of the mains and open up above them. I'd like to avoid that as outrageous size can pose an SAF problem, although it must be admitted that I am between S's.
Getting loopy now, off to sleep.
ensen.
I've just glanced at the PDF on Martin's site and it is definitely not bedtime reading. So I will probably end up modifying the design after going through the article without the haze of late night forum play.
Still what I gather so far is that my effective line is about 96" which is just shy of the 102.5" I calculate based on driver Fs=33Hz. I think the actual is 32.8Hz based on some of the PDFs on the Parts Express website.
In any case, there is evidence on
http://www.pmcloudspeaker.com/transmission.html
that building a line shorter than 1/4 wave is okay as long as you stuff it to make it "effectively" longer. I read this somewhere, but cannot recall where right now.
I took rough measurements of the pic based on the monitor shown (DB1S) and the physical dimensions published in the specs - a reverse engineering trick I learned from recumbent bike building. So, even though the enclosure shown might have an effective line length of almost 5 ft, the actual physical line is only about 3.5 ft. I'm hoping it will be possible to stuff the 6 ft line enough to make it act like a longer line. If needed, I still have the option of making the line go all the way around the back of the mains and open up above them. I'd like to avoid that as outrageous size can pose an SAF problem, although it must be admitted that I am between S's.
Getting loopy now, off to sleep.
ensen.
purplepeople said:
Stuffing does not make the line longer. But tapering from fat to skinny will lower the fundemental resonance vrs a straight line of the same length, so achieves the same result -- shorter line. You can also tune the line to above the Fs althouh in your case you probably don't want that.
dave
So, according to Martin's Alignment discussion, the calculation goes like I have it below and it looks like I have to modify the enclosure to a bit to look more like Option B.
ensen.
Option A
Fs = 33Hz
Qts = 0.32
Bl = 11.07 (from http://www.partsexpress.com/pdf/295-305.pdf)
Sd = .020 m2 = 31.7 sq. in. (6.5" dia with 1.375" voice coil)
If I choose Sl / So = 0.1 to make the line as small as possible then:
Le = 64"
Zn = 40.01
Ze = 1.88
So/Sd = 5.08
So = .10 m2 = 155 sq in = 12" x 13"
Sl = .01 m2 = 15.5 sq in = 2" x 8" =
and finally...
L = 1.625m - .6(.01 / pi)^.5 = 1.591m = 62.6"
Option B
If I adjust to Sl / So = 0.2 I get instead
Le = 75" = 1.905 m
Zn = 34.255
Ze = 1.88
So/Sd = 4.35
So = .087 m2 = 135 sq in = 12" x 11"
Sl = .017 m2 = 27 sq in = 3" x 9"
and finally...
L = 1.905m - .6(.017 / pi)^.5 = 1.709m = 67.3"
ensen.Option A
Fs = 33Hz
Qts = 0.32
Bl = 11.07 (from http://www.partsexpress.com/pdf/295-305.pdf)
Sd = .020 m2 = 31.7 sq. in. (6.5" dia with 1.375" voice coil)
If I choose Sl / So = 0.1 to make the line as small as possible then:
Le = 64"
Zn = 40.01
Ze = 1.88
So/Sd = 5.08
So = .10 m2 = 155 sq in = 12" x 13"
Sl = .01 m2 = 15.5 sq in = 2" x 8" =
and finally...
L = 1.625m - .6(.01 / pi)^.5 = 1.591m = 62.6"
Option B
If I adjust to Sl / So = 0.2 I get instead
Le = 75" = 1.905 m
Zn = 34.255
Ze = 1.88
So/Sd = 4.35
So = .087 m2 = 135 sq in = 12" x 11"
Sl = .017 m2 = 27 sq in = 3" x 9"
and finally...
L = 1.905m - .6(.017 / pi)^.5 = 1.709m = 67.3"
Correct, the stuffing will not make the physical lenght longer, though, it may make the acoustic length longer. Using the universal wave equation and the known fact that stuffing slows the velocity of sound, one can prove this. I have a TL using the 5.25" HM130Z2 by Audax. Terrific sounding, but doesn't hit the real lows as you have mentioned.
Perhaps you could use the Daytons in tandem with an active sub-amp....not very clear eh? Well, you can use one Dayton woofer in each TL enclosure for the sub-frequencies then, in a sealed enclosure atop the TL system, you can use smaller mid-bass drivers to hit from 100Hz., and a tweet. I mentioned sealed because sealed keeps the namesake of the TL, natural, uncoloured sound and dare I say it? "fast" bass.
Heck! if you do decide to use a system similar to this, you CAN use a larger driver...cheaper? car audio? The possibilities are endless....I love DIY
Perhaps you could use the Daytons in tandem with an active sub-amp....not very clear eh? Well, you can use one Dayton woofer in each TL enclosure for the sub-frequencies then, in a sealed enclosure atop the TL system, you can use smaller mid-bass drivers to hit from 100Hz., and a tweet. I mentioned sealed because sealed keeps the namesake of the TL, natural, uncoloured sound and dare I say it? "fast" bass.
Heck! if you do decide to use a system similar to this, you CAN use a larger driver...cheaper? car audio? The possibilities are endless....I love DIY
Hi Bose(o)
I just need the low notes. My mains are plenty loud and accurate for most needs. Even from the hall outside my apartment with the door closed, you can hear the precision of the system.
http://www.proaudioreview.com/par/june02/Yorkville_YSM1P.shtml
Really, in most cases, I don't need the subs, but I admit to wanting to have gut-thumping capability just to impress the guests, and with a pair of subs that also integrate well physically. What I don't want is some huge black cube where people end up putting their drinks. Initially they will be driven by the Sansui R-70 receiver and will probably get chip amps when I get around to it. I like active speakers - the longest cable runs are actually shielded and are line-level so can be wire balanced if necessary.
As for changing Mach numbers and line lengths, I think that adding stuffing to "slow the speed of sound" and "make the line longer" are refering to the same thing, which is that it takes more time for a wave originating at the driver to make its way to the open end of the transmission line.
Physics has proven (to me) beyond most reasonable doubt that the speed of sound in air is dependent on pressure and temperature and remains the same if those two values don't change. It is faster in denser fluids like water and faster still in solids like steel. It does not slow when it hits the stuffing, but it does follow the contours of the surface of the stuffing which forces the wave to zig and zag over a greater distance. The line is not longer, but the travel distance is. The speed of sound is not slower, but it takes more time for the wave to hit the opening.
Wavelength has a role to play here. If you choose a stuffing with extremely rough surface elements - say tennis balls - they will also lower frequencies than stuffing that is finer, like Velcro. This is why most stuffing like wool will attenuate high frequencies but not work on bass notes. In addition to damping the energy in the wave, it forces small wavelengths to travel along the surface irregularities making them take "forever" to reach the opening of the line. If you look at the egg-crate stuffing used by PMC, it will not only attenuate higher frequencies because of the open-cell foam material being used, but will also make some of the lower frequences travel a longer distance, increasing the "effective" line length as stated in their specs.
Since I am going to use a line-level filter for highs, I won't be adding any stuffing except for fine-tuning the harmonics generated by the enclosure. I may use large diameter "speed bumps" to tune the line length but again, only as needed.
What do you all think about adding an adjustable baffle to allow for variable driver offset, as indicated by MJK?
Also, my intent for putting the opening near the driver is so that together they are more of a point source and if the mains sit on top, then also close to those drivers. I know I will lose some gain from the floor. Is there really 6db of gain by putting the driver or opening near the floor?
ensen
I just need the low notes. My mains are plenty loud and accurate for most needs. Even from the hall outside my apartment with the door closed, you can hear the precision of the system.
http://www.proaudioreview.com/par/june02/Yorkville_YSM1P.shtml
Really, in most cases, I don't need the subs, but I admit to wanting to have gut-thumping capability just to impress the guests, and with a pair of subs that also integrate well physically. What I don't want is some huge black cube where people end up putting their drinks. Initially they will be driven by the Sansui R-70 receiver and will probably get chip amps when I get around to it. I like active speakers - the longest cable runs are actually shielded and are line-level so can be wire balanced if necessary.
As for changing Mach numbers and line lengths, I think that adding stuffing to "slow the speed of sound" and "make the line longer" are refering to the same thing, which is that it takes more time for a wave originating at the driver to make its way to the open end of the transmission line.
Physics has proven (to me) beyond most reasonable doubt that the speed of sound in air is dependent on pressure and temperature and remains the same if those two values don't change. It is faster in denser fluids like water and faster still in solids like steel. It does not slow when it hits the stuffing, but it does follow the contours of the surface of the stuffing which forces the wave to zig and zag over a greater distance. The line is not longer, but the travel distance is. The speed of sound is not slower, but it takes more time for the wave to hit the opening.
Wavelength has a role to play here. If you choose a stuffing with extremely rough surface elements - say tennis balls - they will also lower frequencies than stuffing that is finer, like Velcro. This is why most stuffing like wool will attenuate high frequencies but not work on bass notes. In addition to damping the energy in the wave, it forces small wavelengths to travel along the surface irregularities making them take "forever" to reach the opening of the line. If you look at the egg-crate stuffing used by PMC, it will not only attenuate higher frequencies because of the open-cell foam material being used, but will also make some of the lower frequences travel a longer distance, increasing the "effective" line length as stated in their specs.
Since I am going to use a line-level filter for highs, I won't be adding any stuffing except for fine-tuning the harmonics generated by the enclosure. I may use large diameter "speed bumps" to tune the line length but again, only as needed.
What do you all think about adding an adjustable baffle to allow for variable driver offset, as indicated by MJK?
Also, my intent for putting the opening near the driver is so that together they are more of a point source and if the mains sit on top, then also close to those drivers. I know I will lose some gain from the floor. Is there really 6db of gain by putting the driver or opening near the floor?
ensenNot changing the direction of the thread to the stuffing of TLs, though I did take your comments into account and have understood that the change would be very slight like the diffraction index of air at 10 degrees Celsius versus 15 degrees celsius....very, very slight.
The thing that I'd worry about is the excursion of the driver as it is a lesser size than an 'true' sub-woofer it would have to compensate the air moving ability somewhat. I have had tremendous results with a Vifa 8" for a car subwoofer (TL ofcourse) and outside, this thing could pump! So far, 75% of my friends have TL subs by yours truly ! Why do you want 'only' a 6.5" driver?
The thing that I'd worry about is the excursion of the driver as it is a lesser size than an 'true' sub-woofer it would have to compensate the air moving ability somewhat. I have had tremendous results with a Vifa 8" for a car subwoofer (TL ofcourse) and outside, this thing could pump! So far, 75% of my friends have TL subs by yours truly
! Why do you want 'only' a 6.5" driver?Not to be a wet blanket, but if you want gut thumping low bass, why choose a 6.5 inch woofer, even one with a low fs? My experience (with IMFs) is that TLs go surprisingly low, but they may not satisfy your desires. TL bass is typically described as smooth (resonance free) and deep, but not as fast or punchy. I didn't think it was that great for rock music, and might not be for HT since most of what we think of as gut thumping bass is not actually all that deep.
purplepeople,
I checked you math for the alignments you calculated and it looks fine.
You wrote :
I am not sure I agree with this reasoning for the reduced speed of sound in a fiber filled pipe. Remember that a sound wave traveling down a pipe is really small back and forth motions of air at any given location. These motions act like a falling chain of dominos as the sound wave travels along the length. A particular molecule of air does not really move very far and returns to its original postion after the wave has passed.
I think that the slight slowing of the speed of sound in a fiber filled TL is due to the loss of the perfectly adiabatic expansion and compression of the air as the sound wave passes. As the air is compressed it increases in temperatue slightly and some heat is transfered to the fiber. When it expands it drops in temperature and the now warmed fibers give the heat back to the air. This is the same as what happens in a closed box when it appears to have a larger volume when fiber filling is added.
If you buy my hypothesis, the the absolute lower limit for the speed of sound is calculated as follows :
c' = c (1.0/1.4)^0.5 = 0.8452 c
This represents the transition from an adiabatic process to an isothermal process. In reality, I doubt that this lower limit can be achieved and more then likely the lower limit is closer to the following :
c' = c (1.2/1.4)^0.5 = 0.9258 c
When a sound wave, that is at least four times longer then the length of the pipe, encounters a fiber that is that small I think that the wave just passes around the fiber as if it were not there. Remember that shear stresses are not present in air so I do not see the sound wave "bending" as it wraps around an object.
Hope that helps,
I checked you math for the alignments you calculated and it looks fine.
You wrote :
I am not sure I agree with this reasoning for the reduced speed of sound in a fiber filled pipe. Remember that a sound wave traveling down a pipe is really small back and forth motions of air at any given location. These motions act like a falling chain of dominos as the sound wave travels along the length. A particular molecule of air does not really move very far and returns to its original postion after the wave has passed.
I think that the slight slowing of the speed of sound in a fiber filled TL is due to the loss of the perfectly adiabatic expansion and compression of the air as the sound wave passes. As the air is compressed it increases in temperatue slightly and some heat is transfered to the fiber. When it expands it drops in temperature and the now warmed fibers give the heat back to the air. This is the same as what happens in a closed box when it appears to have a larger volume when fiber filling is added.
If you buy my hypothesis, the the absolute lower limit for the speed of sound is calculated as follows :
c' = c (1.0/1.4)^0.5 = 0.8452 c
This represents the transition from an adiabatic process to an isothermal process. In reality, I doubt that this lower limit can be achieved and more then likely the lower limit is closer to the following :
c' = c (1.2/1.4)^0.5 = 0.9258 c
When a sound wave, that is at least four times longer then the length of the pipe, encounters a fiber that is that small I think that the wave just passes around the fiber as if it were not there. Remember that shear stresses are not present in air so I do not see the sound wave "bending" as it wraps around an object.
Hope that helps,
Not as techie as you guys, but I have a good set of ears so I'll chime in...
I run a pair of Transmission Line subs (for L-R balance) using Focal Kevlar 8" 8K5412 drivers, and a single 150w amp module running both subs in parrallel. The low end bass extension and articulation of this sub is superb! It supposedly measures down to 13Hz @ -3dB.
I don't know why anyone would want to go with a smaller driver unless WAF/SAF is a factor and you are trying to design the box downwards in size? Going to a smaller driver may give a little more speed, which may or may not be noticeable, but you would lose out big time with lack of bass extension and less slam. Even the 8" driver could do with a bit more slam, let alone a 6.5" one.
My folded box is basically the same as the TL sub shown on Sheldon Stokes' ESL website, having a 4.2m long folded line. However, I don't believe you should lay it on it's side like Sheldon has done (although handy as a stand for the ESL, the bass gets very dirty sounding this way).Ideally, the box should stand upright with its tallest dimension in the vertical plane, driver at the top and port exiting at the top on the back. IMO, this keeps the bass unit and the port clear of the floor, thereby reducing 'floor-bounce effects' and bass colorations.
The bass from this TL sub is VERY FAST and 'audiophilish', and goes very well with my Quad ESL's; my big 90kg Raven R1 ribbon/dual Accuton Ceramic C79/dual Cabasse 21NDC speaker array or my super fast thin-membraned (3.8 micron) kit electrostats...with the latter speaker being my favourite one!
Regards,
Steve M.
I run a pair of Transmission Line subs (for L-R balance) using Focal Kevlar 8" 8K5412 drivers, and a single 150w amp module running both subs in parrallel. The low end bass extension and articulation of this sub is superb! It supposedly measures down to 13Hz @ -3dB.
I don't know why anyone would want to go with a smaller driver unless WAF/SAF is a factor and you are trying to design the box downwards in size? Going to a smaller driver may give a little more speed, which may or may not be noticeable, but you would lose out big time with lack of bass extension and less slam. Even the 8" driver could do with a bit more slam, let alone a 6.5" one.
My folded box is basically the same as the TL sub shown on Sheldon Stokes' ESL website, having a 4.2m long folded line. However, I don't believe you should lay it on it's side like Sheldon has done (although handy as a stand for the ESL, the bass gets very dirty sounding this way).Ideally, the box should stand upright with its tallest dimension in the vertical plane, driver at the top and port exiting at the top on the back. IMO, this keeps the bass unit and the port clear of the floor, thereby reducing 'floor-bounce effects' and bass colorations.
The bass from this TL sub is VERY FAST and 'audiophilish', and goes very well with my Quad ESL's; my big 90kg Raven R1 ribbon/dual Accuton Ceramic C79/dual Cabasse 21NDC speaker array or my super fast thin-membraned (3.8 micron) kit electrostats...with the latter speaker being my favourite one!
Regards,
Steve M.
Size
As an apartment dweller, any of the cannon type lines are just too big. A small footprint is worth its non-weight. Future WAF is the added bonus. I don't have a spouse now, but in future, it would be far worse to have a great sounding, but huge sub that had to be given up due to WAF. Just ask all those guys who had to sell their motorcycle.
You can see that with a 6.5" driver, the calculation shows that the closed end is already quite big. Thanks for checking, Martin. Imagine the size now with an 8" or 10" driver. I don't want it to be (much) bigger than any current or future TV screen.
Whether the 6.5" Dayton will do the job remains to be seen. However, the larger drivers have not impressed me. That's why I've asked if anyone has used the smaller ones. Most small TLs use drivers with good response out to the XO freq and give up low end extension for it. In this case, the driver only has to be good below 200Hz.
ensen
As an apartment dweller, any of the cannon type lines are just too big. A small footprint is worth its non-weight. Future WAF is the added bonus. I don't have a spouse now, but in future, it would be far worse to have a great sounding, but huge sub that had to be given up due to WAF. Just ask all those guys who had to sell their motorcycle.
You can see that with a 6.5" driver, the calculation shows that the closed end is already quite big. Thanks for checking, Martin. Imagine the size now with an 8" or 10" driver. I don't want it to be (much) bigger than any current or future TV screen.
Whether the 6.5" Dayton will do the job remains to be seen. However, the larger drivers have not impressed me. That's why I've asked if anyone has used the smaller ones. Most small TLs use drivers with good response out to the XO freq and give up low end extension for it. In this case, the driver only has to be good below 200Hz.
ensen
Impact
I think that thump must be a question of driver speed. My analogy is from the large flight simulators. They only need to create short accelerations in order to fool the trainees into thinking the "airplane" is performing large g-force motions. I think the same with my stomach. If I thump it with enough speed, it will feel the same as pushing it with a large surface. So, larger cone, larger voice coils and magnets, and so larger moving mass. Larger mass needs more amp just to accelerate. I cannot afford Bryston 7s just to have thump, even though I know it is a question of total system energy. I'm just trying to get some thump in my apartment, not the disco.
That need for speed is also why I chose the TL. The air spring inside a sealed box creates a resistance to changes in box volume - ie. moving the cone. Ever try to move a bike pump after blocking the valve? The pump doesn't want to do anything. TL is open so air can move in and out if it wants to. Ports are similar except that the port diameter limits the amount of air that can move through it, so we still get some air spring effects.
Recently, I actually heard a 15" Velodyne and I thought it was very mushy. It vibrated my stomach but it was not thumping it. It was disappointingly slow. And awhile back I listened to a Sunfire Jr. and it was amazing. But I recall that it was using some kind of servo feedback. Accurate servos are not cheap and neither was the Carver. My brother-in-law has a pair of Linn Keiledhs that put out surprising thump if you want them to. I'm pretty sure they are MTM with 5" drivers in a TL. I think that commercial TLs are expensive because of their performance, not their cost. Those PMCs start at twice the price of the Linns.
ensen.
I think that thump must be a question of driver speed. My analogy is from the large flight simulators. They only need to create short accelerations in order to fool the trainees into thinking the "airplane" is performing large g-force motions. I think the same with my stomach. If I thump it with enough speed, it will feel the same as pushing it with a large surface. So, larger cone, larger voice coils and magnets, and so larger moving mass. Larger mass needs more amp just to accelerate. I cannot afford Bryston 7s just to have thump, even though I know it is a question of total system energy. I'm just trying to get some thump in my apartment, not the disco.
That need for speed is also why I chose the TL. The air spring inside a sealed box creates a resistance to changes in box volume - ie. moving the cone. Ever try to move a bike pump after blocking the valve? The pump doesn't want to do anything. TL is open so air can move in and out if it wants to. Ports are similar except that the port diameter limits the amount of air that can move through it, so we still get some air spring effects.
Recently, I actually heard a 15" Velodyne and I thought it was very mushy. It vibrated my stomach but it was not thumping it. It was disappointingly slow. And awhile back I listened to a Sunfire Jr. and it was amazing. But I recall that it was using some kind of servo feedback. Accurate servos are not cheap and neither was the Carver. My brother-in-law has a pair of Linn Keiledhs that put out surprising thump if you want them to. I'm pretty sure they are MTM with 5" drivers in a TL. I think that commercial TLs are expensive because of their performance, not their cost. Those PMCs start at twice the price of the Linns.
ensen.
Convince me...
I re-read the thread and I might be convinced to run a larger driver surface. I'm still against larger drivers for the extra mass but since I'm already planning to have 2 cabinet, how about 2 drivers per cabinet, or more? Do I just multiply Sd by the number of drivers for the re-calculations?
ensen.
I re-read the thread and I might be convinced to run a larger driver surface. I'm still against larger drivers for the extra mass but since I'm already planning to have 2 cabinet, how about 2 drivers per cabinet, or more? Do I just multiply Sd by the number of drivers for the re-calculations?
ensen.
Calculating Sd
In my calculations I estimate Sd based on the are total area covered by the driver minus the area of the voice coil. In lieu of (or even to confirm) published Sd specs, should I be using different measurements.
Example. I looked at the 6.5" drivers of my Proto-Js. The actual conic section has a diamter of about 5" while the whole moving section including the butyl surround is about 5.75" and finally, since the voice coil cover moves also, should I really be subtracting that area?
Which then begs the question: At what point am I being too precise with my measurements and calculations? It goes to the old adage of "measure twice and cut once."
ensen.
In my calculations I estimate Sd based on the are total area covered by the driver minus the area of the voice coil. In lieu of (or even to confirm) published Sd specs, should I be using different measurements.
Example. I looked at the 6.5" drivers of my Proto-Js. The actual conic section has a diamter of about 5" while the whole moving section including the butyl surround is about 5.75" and finally, since the voice coil cover moves also, should I really be subtracting that area?
Which then begs the question: At what point am I being too precise with my measurements and calculations? It goes to the old adage of "measure twice and cut once."
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