Hi CLS,
I see you kept Estes right. Some manufacturers use different colours on their secondary wires, which does not help.
The T-bass needs less than 0.1 ohm driving resistance to work properly. Fitting another transformer between the amp and T-bass will not satisfy this requirement.
Loudspeakers on an OB have a higher dynamic impedance than when used in an enclosure which offers resistance to cone motion, so they require less drive. The lower load impedance presented to an amplifier is thus less critical than experience with enclosured woofers might suggest.
Cheers ......... Graham.
I see you kept Estes right. Some manufacturers use different colours on their secondary wires, which does not help.
The T-bass needs less than 0.1 ohm driving resistance to work properly. Fitting another transformer between the amp and T-bass will not satisfy this requirement.
Loudspeakers on an OB have a higher dynamic impedance than when used in an enclosure which offers resistance to cone motion, so they require less drive. The lower load impedance presented to an amplifier is thus less critical than experience with enclosured woofers might suggest.
Cheers ......... Graham.
Hi Estes,
I don't know if you saw this in my previous post (earlier in this thread):
Plus the wire colors of your transformer:
Black: 0V
R+O: 30V
Yellow: 60V
So you may get a clearer picture here. Among them, the R+O is the CT. And the 0V and 60V are interchangeable -- just take one of them to the top and the other to bottom, and you're done.
If in any doubt, use a multimeter to measure the resistance of the winding (between any 2 of them), you should see a very low resistance, say, <0.5 Ohm or so. So, at least there'll be some sound coming out.
------------------------
Say, I have an interesting finding to share here.
I've posted previously about my center OB sub, in which 2* 8 ohm woofers are connected in parallel. With the 'help' of T-bass, the impedance drops to 0.5 Ohm within a certain frequency range. The plate amp driving it is still alive, with very warm heatsink when working...
I got some free time the other day, and thought, why not try re-wiring them in series, and then I did. At first the volume was down quite a bit because of the much lowered voltage sensitivity. So I cranked it up some and roughly kept it at similar level with the main baffle.
It played for a while and soon I heard some strange sounds (or I should say noises). At some very low frequency notes (compared and confirmed with RTA), and up to a level, the woofers moved a lot and produced some loud deep bass. The long strokes of the cones were seldom seen. Strange thing was, some of the deep bass sounds shouldn't be there!
How did I know?
I'm not 100% sure actually, but the noises were 'additional' notes following the right ones, so it obviously sounded strange and very intrusive. (Did I mention those were strong deep bass?) So drum hits would be followed by 1 or 2 'echoes' which might be louder (or deeper) than the original hits. They're not slow, muffled, decaying 'tails', but additional strong hits. Because they were not in the correct beat, so it sounded noisy and annoying overall.
It kept playing so for a period of time, maybe 20~30 min, the heatsink of the amp was not any cooler than before.
I didn't have my laptop around at the moment, so I could not do any impedance scan. And I couldn't do any other measurement, either
Then I put them back in parallel, and everything came back to normal. Shortly afterward, I and families watched a movie which came with a lot of loud deep bass effects. The whole system (with 4 OB woofers and all driven by T-bass) worked so well -- LOTS of clean, deep, room-filling shaking power. Driving all these extreme low impedance loads, all my amps survived intact. Dramas were on the screen, not on these amps. Heatsinks were as warm as usual, but not any warmer. Good
I was very surprised by the big (abnormal) change brought by the series connection of woofers. I really don't know why it happened. Would it be possible that the back EMF between the 2 woofers are strongly bouncing back and forth with the transformer? Or could it be the satuation of the transformer?
I'm also wondering if anyone else had found this?
Simon, I remebered you connected your 4 woofers in parallel-series and it seemed fine. Am I right?
Any comments?
I don't know if you saw this in my previous post (earlier in this thread):
Plus the wire colors of your transformer:
Black: 0V
R+O: 30V
Yellow: 60V
So you may get a clearer picture here. Among them, the R+O is the CT. And the 0V and 60V are interchangeable -- just take one of them to the top and the other to bottom, and you're done.
If in any doubt, use a multimeter to measure the resistance of the winding (between any 2 of them), you should see a very low resistance, say, <0.5 Ohm or so. So, at least there'll be some sound coming out.
------------------------
Say, I have an interesting finding to share here.
I've posted previously about my center OB sub, in which 2* 8 ohm woofers are connected in parallel. With the 'help' of T-bass, the impedance drops to 0.5 Ohm within a certain frequency range. The plate amp driving it is still alive, with very warm heatsink when working...
I got some free time the other day, and thought, why not try re-wiring them in series, and then I did. At first the volume was down quite a bit because of the much lowered voltage sensitivity. So I cranked it up some and roughly kept it at similar level with the main baffle.
It played for a while and soon I heard some strange sounds (or I should say noises). At some very low frequency notes (compared and confirmed with RTA), and up to a level, the woofers moved a lot and produced some loud deep bass. The long strokes of the cones were seldom seen. Strange thing was, some of the deep bass sounds shouldn't be there!
How did I know?
I'm not 100% sure actually, but the noises were 'additional' notes following the right ones, so it obviously sounded strange and very intrusive. (Did I mention those were strong deep bass?) So drum hits would be followed by 1 or 2 'echoes' which might be louder (or deeper) than the original hits. They're not slow, muffled, decaying 'tails', but additional strong hits. Because they were not in the correct beat, so it sounded noisy and annoying overall.
It kept playing so for a period of time, maybe 20~30 min, the heatsink of the amp was not any cooler than before.
I didn't have my laptop around at the moment, so I could not do any impedance scan. And I couldn't do any other measurement, either
Then I put them back in parallel, and everything came back to normal. Shortly afterward, I and families watched a movie which came with a lot of loud deep bass effects. The whole system (with 4 OB woofers and all driven by T-bass) worked so well -- LOTS of clean, deep, room-filling shaking power. Driving all these extreme low impedance loads, all my amps survived intact. Dramas were on the screen, not on these amps. Heatsinks were as warm as usual, but not any warmer. Good
I was very surprised by the big (abnormal) change brought by the series connection of woofers. I really don't know why it happened. Would it be possible that the back EMF between the 2 woofers are strongly bouncing back and forth with the transformer? Or could it be the satuation of the transformer?
I'm also wondering if anyone else had found this?
Simon, I remebered you connected your 4 woofers in parallel-series and it seemed fine. Am I right?
Any comments?
Hi CLS,
Mine seem ok in series-parallel but they're cheap speakers using cheap drivers and cannot play much deep bass.. so any negatives of using series-parallel may not be as audible as in a higher end system that can produce more prodigious deep bass, such as yours.
I'm using 2 x 8ohm in parallel next. Baffles are mostly cut now... but I'm abroad for another week so progress is slow
Simon
Mine seem ok in series-parallel but they're cheap speakers using cheap drivers and cannot play much deep bass.. so any negatives of using series-parallel may not be as audible as in a higher end system that can produce more prodigious deep bass, such as yours.
I'm using 2 x 8ohm in parallel next. Baffles are mostly cut now... but I'm abroad for another week so progress is slow
Simon
Two parallel 8 Ohm woofers will result in 4 Ohm. Two series 8 Ohm woofers will result in 16 Ohm. Your cross-over was designed for 4 Ohm. With a 16 Ohm load the T-Bass circuit will be underdamped, resulting in a long decay time, during which overshooting instead of settling could produce the effect you describe.CLS said:
Hi,
Overshooting, yes, very likely. The cones really moved a lot.
But there's no xover between plate amp and drivers. Low pass filter is line level and built-in with plate amp.
And the L/C combinations in the T-bass circuit should not interfere with the load, as I remember.
Still wondering.
Overshooting, yes, very likely. The cones really moved a lot.
But there's no xover between plate amp and drivers. Low pass filter is line level and built-in with plate amp.
And the L/C combinations in the T-bass circuit should not interfere with the load, as I remember.
Still wondering.
Hi CLS,
Overshoot ? Second beat ? Or delayed transient residual ?
Could be the amplifier NFB - use headphones on output terminals to check for this.
Or it could be the resistors in series with the L and C being too low for the loudspeaker resistance being driven.
The L an C are to turnover in a manner which counteracts loudspeaker resonance, storage and baffle characteristic, thus those component values change only slightly with driver impedance. However, too low values of R in series with the L and C with respect to driver resistance can lead too impactful a reverse pulse at a lower turnover which no longer counters driver dynamics; this might be what you are hearing and again could be checked for with headphones, this time across the loudspeaker terminals.
Cheers ...... Graham.
Overshoot ? Second beat ? Or delayed transient residual ?
Could be the amplifier NFB - use headphones on output terminals to check for this.
Or it could be the resistors in series with the L and C being too low for the loudspeaker resistance being driven.
The L an C are to turnover in a manner which counteracts loudspeaker resonance, storage and baffle characteristic, thus those component values change only slightly with driver impedance. However, too low values of R in series with the L and C with respect to driver resistance can lead too impactful a reverse pulse at a lower turnover which no longer counters driver dynamics; this might be what you are hearing and again could be checked for with headphones, this time across the loudspeaker terminals.
Cheers ...... Graham.
Thanks Graham.
Alas, I don't have any headphone on hand
By the way, I didn't mention the T-bass setup of my parallel center sub. The L is 8mH and C is 1880uF (4x 470 in parallel). No R in series with any of them. Both L and C are somewhat large, because I wanted to push it as low as possible. After all it's a sub.
I like it very much when in parallel, works so well, no complaint.
Furthur experiments can be done until I settle down in the new place. I'll be moving in the near future, so busy....
Alas, I don't have any headphone on hand
By the way, I didn't mention the T-bass setup of my parallel center sub. The L is 8mH and C is 1880uF (4x 470 in parallel). No R in series with any of them. Both L and C are somewhat large, because I wanted to push it as low as possible. After all it's a sub.
I like it very much when in parallel, works so well, no complaint.
Furthur experiments can be done until I settle down in the new place. I'll be moving in the near future, so busy....
I come here as to no longer hitchhike another thread
Gave the circuit a try as to CLS' recommendation .
You can look at the story before at
http://www.diyaudio.com/forums/showthread.php?postid=1805716#post1805716
Yes - I might have to admit it's been a really crappy "on the fly" setup I used (as already told) -
- so not exactly the best platform to draw serious conclusions - but it definitely was good enough to reveal the shortcomings of passive components after the power amp (the 250VA torroid is in the lower right corner under the 0.5 Ohm air core's, by the way).
The differences from paralleling capacitors in that circuit were clearly audible down to the 1nF silver mica - step by step (this is also one of the reasons I always will have reservations about passive XO).
Imagine - that was for a total capacitance of close to 1000uF and a frequency range of pure bass !!
Besides that I can backup Grahams observation that additional resistance after the circuit due to different cables *is* clearly audible - but this is also the case for adding some meters of decent cable *without* that circuit (the REGA cable shown - I normally don't use but had at hand for the purpose).
OB bass is *that* revealing !
Michael
Gave the circuit a try as to CLS' recommendation .
You can look at the story before at
http://www.diyaudio.com/forums/showthread.php?postid=1805716#post1805716
CLS said:
Yes - I might have to admit it's been a really crappy "on the fly" setup I used (as already told) -
- so not exactly the best platform to draw serious conclusions - but it definitely was good enough to reveal the shortcomings of passive components after the power amp (the 250VA torroid is in the lower right corner under the 0.5 Ohm air core's, by the way).
The differences from paralleling capacitors in that circuit were clearly audible down to the 1nF silver mica - step by step (this is also one of the reasons I always will have reservations about passive XO).
Imagine - that was for a total capacitance of close to 1000uF and a frequency range of pure bass !!
Besides that I can backup Grahams observation that additional resistance after the circuit due to different cables *is* clearly audible - but this is also the case for adding some meters of decent cable *without* that circuit (the REGA cable shown - I normally don't use but had at hand for the purpose).
OB bass is *that* revealing !
Michael
Hi Michael,
At least the transformer-bass circuit does provide an alternative.
What it comes down to is that a LF driver always stores energy, and it gets trapped within the driver system with respect to the amplifier. EQ etc cannot counter this because all it tends to do is cause more trapped energy acting in driver/baffle/room time.
Once T-bass is implemented however EQ no longer causes an excess of trapped energy acting separately.
I managed to get my website up again. T-bass is here -
http://www.gmweb2.net/new_page_1.htm
(Won't be long before your new baffle is up and running Simon!)
Cheers ...... Graham.
At least the transformer-bass circuit does provide an alternative.
What it comes down to is that a LF driver always stores energy, and it gets trapped within the driver system with respect to the amplifier. EQ etc cannot counter this because all it tends to do is cause more trapped energy acting in driver/baffle/room time.
Once T-bass is implemented however EQ no longer causes an excess of trapped energy acting separately.
I managed to get my website up again. T-bass is here -
http://www.gmweb2.net/new_page_1.htm
(Won't be long before your new baffle is up and running Simon!)
Cheers ...... Graham.
LspCad & T-bass
I don't know if this is mentioned earlier, that You can model the T-bass circuit AND a dipole speaker in the excellent program LspCad. You can see that the T-bass system goes some 12 hz lower at F3. The pulse output is almost the same. The impedance curve is totally erratic in the T-bass simulation........
I have only the demoversion so I can't save the setup file for the shown circuit.
I don't know if this is mentioned earlier, that You can model the T-bass circuit AND a dipole speaker in the excellent program LspCad. You can see that the T-bass system goes some 12 hz lower at F3. The pulse output is almost the same. The impedance curve is totally erratic in the T-bass simulation........
I have only the demoversion so I can't save the setup file for the shown circuit.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Hi Michael,
Did you do anything to your original xover/EQ? They are supposed to be re-adjusted to make it reasonably flat. T-bass would force the amp to dump much more current, thus more output around the tuned frequency. If your system was flat with original xover/EQ, now there should be a bump in the low bass.
After you sort the T-bass circuit to a level and with proper xover/EQ, I bet you'll get a much better result.
CLS
Did you do anything to your original xover/EQ? They are supposed to be re-adjusted to make it reasonably flat. T-bass would force the amp to dump much more current, thus more output around the tuned frequency. If your system was flat with original xover/EQ, now there should be a bump in the low bass.
After you sort the T-bass circuit to a level and with proper xover/EQ, I bet you'll get a much better result.
CLS
Hi Jonas,
That 10mH/220u is like an MJK recommended LF crossover.
Conventional and T-bass are quite different concepts.
Take those components out, they are causing additional storage in their own time, also a phase shift which you not investigating in music time.
Steady sine established amplitude responses are quite different to what we really hear in Music Time.
Cheers ....... Graham.
That 10mH/220u is like an MJK recommended LF crossover.
Conventional and T-bass are quite different concepts.
Take those components out, they are causing additional storage in their own time, also a phase shift which you not investigating in music time.
Steady sine established amplitude responses are quite different to what we really hear in Music Time.
Cheers ....... Graham.