Graeme
One idea would be to use a sixth order alignment first proposed by your countryman Thiele in 1961
If you tune the cabinet to 40Hz and have a high pass filter with a 6db peak at 40Hz you will extend the frequency response and cut down the excursion. Article about Thiele here:
http://www.audioxpress.com/magsdirx/voxcoil/interview-thiele105.pdf
One idea would be to use a sixth order alignment first proposed by your countryman Thiele in 1961
If you tune the cabinet to 40Hz and have a high pass filter with a 6db peak at 40Hz you will extend the frequency response and cut down the excursion. Article about Thiele here:
http://www.audioxpress.com/magsdirx/voxcoil/interview-thiele105.pdf
Sorry for the delays in responding but got caught up in the Christmas spirit and family priorities.
Again I emphasise that I am an absolute beginner at this audio stuff.
When I plugged my HPD385 TS parameters into WinISD it calculated an optimal vented box size of 33.7 litres tuned to 50.23 Hz. Bass response of only 73 Hz at -3 dB.
Increasing the box size in WinISD to my actual size of 85 litres showed it still tuned to 50.23 Hz, but the -3 dB base extended down to 51 Hz.
I was surprised that WinISD calculated such a small box size for this speaker as everything I read says bigger is better. (Except my interior decorator)
Thanks for the article on Neville Thiele, Consort; he seems an impressive gentleman in addition to his discoveries.
The concept of a 'sixth order alignment' is beyond my current knowledge base and one of the reasons I am asking these questions. Getting a crash course on applied audio theory from peolple who have done it.
Thanks again.
Graeme
Again I emphasise that I am an absolute beginner at this audio stuff.
When I plugged my HPD385 TS parameters into WinISD it calculated an optimal vented box size of 33.7 litres tuned to 50.23 Hz. Bass response of only 73 Hz at -3 dB.
Increasing the box size in WinISD to my actual size of 85 litres showed it still tuned to 50.23 Hz, but the -3 dB base extended down to 51 Hz.
I was surprised that WinISD calculated such a small box size for this speaker as everything I read says bigger is better. (Except my interior decorator)
Thanks for the article on Neville Thiele, Consort; he seems an impressive gentleman in addition to his discoveries.
The concept of a 'sixth order alignment' is beyond my current knowledge base and one of the reasons I am asking these questions. Getting a crash course on applied audio theory from peolple who have done it.
Thanks again.
Graeme
Just been trying to find an on-line article on the benefits of the sixth order system but surprisingly little is available. Found an article here:
http://perso.orange.fr/francis.audio2/Snyder_nVasQts2.pdf
which shows the effect of a new surround is not that important in the enclosure design.
http://perso.orange.fr/francis.audio2/Snyder_nVasQts2.pdf
which shows the effect of a new surround is not that important in the enclosure design.
Hi,
there is a sixth order alignment for each fourth order alignment.
Bullock promotes the idea that the two that offer advantage are the QB5 and C6 and divides them into class 1, 11 or 111.
Having looked at class1 & 11.
I see that class11 offers high SPL without damaging the driver (no low bass) and class1 offers extra low bass but reduces the power handling (but still better than fourth order).
I think Linkwitz discusses the class1 version and shows the calculations for the electrical side of the alignment. But he does not examine the box side of the alignment.
I used "Bullock on Boxes" Audio Amateur Press by Robert M Bullock 111.
His box design program is now available on the web, but without the understanding of how the various parameters interact then you will get lost in the maths and the program/graphs. When I came across the program and tried to use it, I got completely confused by the rubbish I was generating, no patterns were emerging. I had to go back and re-read "On Boxes" to make sense of it.
there is a sixth order alignment for each fourth order alignment.
Bullock promotes the idea that the two that offer advantage are the QB5 and C6 and divides them into class 1, 11 or 111.
Having looked at class1 & 11.
I see that class11 offers high SPL without damaging the driver (no low bass) and class1 offers extra low bass but reduces the power handling (but still better than fourth order).
I think Linkwitz discusses the class1 version and shows the calculations for the electrical side of the alignment. But he does not examine the box side of the alignment.
I used "Bullock on Boxes" Audio Amateur Press by Robert M Bullock 111.
His box design program is now available on the web, but without the understanding of how the various parameters interact then you will get lost in the maths and the program/graphs. When I came across the program and tried to use it, I got completely confused by the rubbish I was generating, no patterns were emerging. I had to go back and re-read "On Boxes" to make sense of it.
Have spent the last ten days absorbing Snyder's paper, Consort and Andrew, and found the physics rather daunting.
Also got confused with the concept of fourth-order and sixth-order systems as some references seem to use these terms when referring to enclosure design - sealed, vented, bandpass, etc - whilst others referred to the roll-off slope of the frequency graph - -6dB/octave, -12dB/octave, etc.
Now let us consider a sixth order system and test if my understanding of Snyder is correct, or at least heading in the right direction.
Firstly, from WinISD, I believe that my existing boxes are 85 litres tuned to 50.23 Hz. Each box has 2 vents x 110 mm diameter and 180.5 mm length.
First, I think, Snyder (p12 of article) proposes that I should retune these existing boxes one-half an octave lower; ie to 35.52 Hz. [50.23*2^0.5]. Plugging this tuning frequency into WinISD suggests that I would then require each 110mm vent to be 441.5mm long (unrealistic due to box size) or a single 110mm vent 180.5 mm long. To retune to 35.52 Hz do I simply plug one vent???
WinISD now shows the Gain curve decaying or sagging from around 300 Hz and a much shallower slope than before.
Next, I think, Snyder is suggesting adding a "second-order highpass filter with a Q=2 and with the cutoff frequency set to 35.53 Hz." If I have read correctly this filter should eliminate 'rumbles' or noise below 35 Hz and also boost the signal between 35 and 300 Hz to give a flatter curve.
How do I install such a filter (eg What circuitry and components) and does it go in with the existing crossover (a very simple affair). Or should the filter be incorporated in a replacement crossover?
Please be patient if my questions are really basic, but from my perspective I am on a very steep learning curve.
Regards to all
Graeme
Also got confused with the concept of fourth-order and sixth-order systems as some references seem to use these terms when referring to enclosure design - sealed, vented, bandpass, etc - whilst others referred to the roll-off slope of the frequency graph - -6dB/octave, -12dB/octave, etc.
Now let us consider a sixth order system and test if my understanding of Snyder is correct, or at least heading in the right direction.
Firstly, from WinISD, I believe that my existing boxes are 85 litres tuned to 50.23 Hz. Each box has 2 vents x 110 mm diameter and 180.5 mm length.
First, I think, Snyder (p12 of article) proposes that I should retune these existing boxes one-half an octave lower; ie to 35.52 Hz. [50.23*2^0.5]. Plugging this tuning frequency into WinISD suggests that I would then require each 110mm vent to be 441.5mm long (unrealistic due to box size) or a single 110mm vent 180.5 mm long. To retune to 35.52 Hz do I simply plug one vent???
WinISD now shows the Gain curve decaying or sagging from around 300 Hz and a much shallower slope than before.
Next, I think, Snyder is suggesting adding a "second-order highpass filter with a Q=2 and with the cutoff frequency set to 35.53 Hz." If I have read correctly this filter should eliminate 'rumbles' or noise below 35 Hz and also boost the signal between 35 and 300 Hz to give a flatter curve.
How do I install such a filter (eg What circuitry and components) and does it go in with the existing crossover (a very simple affair). Or should the filter be incorporated in a replacement crossover?
Please be patient if my questions are really basic, but from my perspective I am on a very steep learning curve.
Regards to all
Graeme
The earlier Tannoys get poorly represented by PGMs like Win whatever. The TS parameters are also suspect the Drivers (certainly their design parameters) predate that quantification.
Time and experimentation has proven that a 150 Litre (min) size enclosure and prefferably a 300 L one will give significant improvements regardless just what yr home computer Program claims
These drivers are also at their best with amplification that can source 20+ amps at min., that usually precludes Tube types. Bi Amping is "Salesman Talk" in my experiences .. But? as always, yr Mileage may vary.
There IS improvement available through parts replacements in the OEM crossovers. Caps certainly, but Resistors and coils are "fine" as is. The improvements are genuine and worth the small cost efforts..
Further improvements can be found by replacing the Coils with Air Foil types.. but this is a V complex exercise and I would not recomend it as a 1st or even 3 rd step in the process.
There is Lots of imformation potential at Yahoo Groups Tannoy.. Look there amoungst the Tannoy owners for genuine experiences.
G'luck.
Time and experimentation has proven that a 150 Litre (min) size enclosure and prefferably a 300 L one will give significant improvements regardless just what yr home computer Program claims
These drivers are also at their best with amplification that can source 20+ amps at min., that usually precludes Tube types. Bi Amping is "Salesman Talk" in my experiences .. But? as always, yr Mileage may vary.
There IS improvement available through parts replacements in the OEM crossovers. Caps certainly, but Resistors and coils are "fine" as is. The improvements are genuine and worth the small cost efforts..
Further improvements can be found by replacing the Coils with Air Foil types.. but this is a V complex exercise and I would not recomend it as a 1st or even 3 rd step in the process.
There is Lots of imformation potential at Yahoo Groups Tannoy.. Look there amoungst the Tannoy owners for genuine experiences.
G'luck.
GraemeC said:
These box programs generally only recommend flat alignments. The issue with the Tannoys you have is the very low Qts. The woofer is overdamped when used with modern, low damping factor amps. Try modeling a 250 litre box tuned to Fs (22Hz). It produces a shelf - this can be EQ'd out if desired. Natural room lift in the bass may help fill the shelved down LF in some rooms.
Now add 6 ohms of series resistance (often referred to as "Rs" or "Rg" by box modeling programs) to raise the effective Qts and watch what happens to your model. You get nice, flat response, down to around 27Hz at the sacrifice of around 2 db efficiency. You do have to watch out for exceeding Xmax in the LF at higher powers (your program will show you this.)
The old, highly damped drivers were not built to use "modern," flat alignments.
Hi ,
I think you have understood it correctly.
the flat alignment is brought back by the high Q applied at the correct frequency.
You can achieve this by using an Equal Value Sallen & Key filter with the gain setting resistors set to achieve a Q=2.
If you need a Q exactly = 2 then this formula should be applied.
Av (Gain)=3-1/Q (1/Q=a = damping in some references).
Av=3-0.5=2.5 and you know that a non-inverting amp gain = 1+upper resistor/lower resistor so Ru/Rl=1.5. Try to get the parallel value of this pair of resistors to match the series pair of input resistors that set the frequency to minimise the output offset.
If Rfrq=10K the 2*Rfrq=20k then Ru//Rl=20k.
Print off Nat semi app note 779 and maybe some or all of these. oa26 & oa29 & oa 27 & oa21 & oa28, and Burr Brown ab017 & ab014 & ab015 and/or Ti Active Filters and/or Wjung's opamp guide.
I think your plan gives a class1 response which aims for maximising bass extension and will reduce maximum SPL slightly.
However, the 2pole electrical filter does reduce the very low bass signal getting to the amp and speaker, so reducing excursion.
I think you have understood it correctly.
the flat alignment is brought back by the high Q applied at the correct frequency.
You can achieve this by using an Equal Value Sallen & Key filter with the gain setting resistors set to achieve a Q=2.
If you need a Q exactly = 2 then this formula should be applied.
Av (Gain)=3-1/Q (1/Q=a = damping in some references).
Av=3-0.5=2.5 and you know that a non-inverting amp gain = 1+upper resistor/lower resistor so Ru/Rl=1.5. Try to get the parallel value of this pair of resistors to match the series pair of input resistors that set the frequency to minimise the output offset.
If Rfrq=10K the 2*Rfrq=20k then Ru//Rl=20k.
Print off Nat semi app note 779 and maybe some or all of these. oa26 & oa29 & oa 27 & oa21 & oa28, and Burr Brown ab017 & ab014 & ab015 and/or Ti Active Filters and/or Wjung's opamp guide.
I think your plan gives a class1 response which aims for maximising bass extension and will reduce maximum SPL slightly.
However, the 2pole electrical filter does reduce the very low bass signal getting to the amp and speaker, so reducing excursion.
Thanks Bare. I would love to go to large scale boxes, ideally Autograph replicas and I do have the wood working skills to to so. However, for domestic harmony reasons "singing wardrobes" are not acceptable so I am looking to optimise what I have, or perhaps go marginally larger.
Tannoy brochure says that the continuous power handling capacity of the HPD385's is 85 watts into 8 ohms, and my Yamaha CR1000 amp has continuous RMS power rating of 80 w into 8 ohms. This seems a good match. However, I understood that the Tannoys worked well with low powered tube amps, which is contrary to your suggestion that 20+ watts was needed.
I have taken your advice on upgrading the capacitors onboard. Thanks.
Finally, Accept your recommendation re Tannoy groups on Yahoo. However, I have an unspecified bug (or something) in my computer that precludes me from logging onto Yahoo. ISP blames browser, browser blames Windows, MS say they never make mistakes, and Yahoo do not reply to queries. Meanwhile I have to go to a friends to get onto Yahoo.
Graeme
Tannoy brochure says that the continuous power handling capacity of the HPD385's is 85 watts into 8 ohms, and my Yamaha CR1000 amp has continuous RMS power rating of 80 w into 8 ohms. This seems a good match. However, I understood that the Tannoys worked well with low powered tube amps, which is contrary to your suggestion that 20+ watts was needed.
I have taken your advice on upgrading the capacitors onboard. Thanks.
Finally, Accept your recommendation re Tannoy groups on Yahoo. However, I have an unspecified bug (or something) in my computer that precludes me from logging onto Yahoo. ISP blames browser, browser blames Windows, MS say they never make mistakes, and Yahoo do not reply to queries. Meanwhile I have to go to a friends to get onto Yahoo.
Graeme
I read none of the topic.
What I am going to say, based on the new Tannoy 15 inch coaxial type things... Use all the tube gear you can to make them provide the magic you are looking for in the midrange. Without tube gear they are detailed, sound nice, but lack magic.
I am an *** for posting this but I had to when I read the topic name.
What I am going to say, based on the new Tannoy 15 inch coaxial type things... Use all the tube gear you can to make them provide the magic you are looking for in the midrange. Without tube gear they are detailed, sound nice, but lack magic.
I am an *** for posting this but I had to when I read the topic name.
Hi,
I absolutely hate the way Yahoo operates it's Bulletin Board, but there is a great deal of Tannoy knowledge in the posters there.
They do not want to migrate here and we won't open a Tannoy category due to lack of demand. So, one has to frequent both. Bother!
HPD385 will work on valve amps and 20W is right in the territory of single ended and smaller push pull.
If you really wanted to, you could use a small valve amp on the treble and a bigger BJT on the bass.
These speakers really respond to bi-wiring and the next stage before going active is bi-amplifying. I have done both and it is worth it (although only with SS amps).
I absolutely hate the way Yahoo operates it's Bulletin Board, but there is a great deal of Tannoy knowledge in the posters there.
They do not want to migrate here and we won't open a Tannoy category due to lack of demand. So, one has to frequent both. Bother!
HPD385 will work on valve amps and 20W is right in the territory of single ended and smaller push pull.
If you really wanted to, you could use a small valve amp on the treble and a bigger BJT on the bass.
These speakers really respond to bi-wiring and the next stage before going active is bi-amplifying. I have done both and it is worth it (although only with SS amps).
Hi Jeff
I tried modeling the Tannoys in WinISD at 250 litres tuned to 22 Hz and the curve sagged away from about 400 Hz to 25 Hz (-7.5 dB), then dropped sharply approx 6 dB per octave.
Unfortunately I do not know the software well enough to put in the "6 ohm series resistance" so was unable to follow further.
Your approach seems interesting and the loss of 2 Db does not seem significant as WinISD suggests the current setup can produce 94.7 db.
Cheers
Graeme
I tried modeling the Tannoys in WinISD at 250 litres tuned to 22 Hz and the curve sagged away from about 400 Hz to 25 Hz (-7.5 dB), then dropped sharply approx 6 dB per octave.
Unfortunately I do not know the software well enough to put in the "6 ohm series resistance" so was unable to follow further.
Your approach seems interesting and the loss of 2 Db does not seem significant as WinISD suggests the current setup can produce 94.7 db.
Cheers
Graeme
Graeme,
The paper you studied mentions Don Keeles paper avaliable here:
http://www.xlrtechs.com/dbkeele.com/papers.htm
scroll down to no 8
Using Keeles equations on your driver you get a F3 of 37 Hz which is also the box tuning freq and the box size is 64 litres so you are fairly near.
On-line High pass filter designer here:
http://www.beis.de/Elektronik/Filter/ActiveHPFilter.html
You need a second order filter and if you start with a capacitor value of 0.22uF it gives sensible resistor values.
Do not agree with last poster you need a solid state amp to give the bottom end grunt!
The paper you studied mentions Don Keeles paper avaliable here:
http://www.xlrtechs.com/dbkeele.com/papers.htm
scroll down to no 8
Using Keeles equations on your driver you get a F3 of 37 Hz which is also the box tuning freq and the box size is 64 litres so you are fairly near.
On-line High pass filter designer here:
http://www.beis.de/Elektronik/Filter/ActiveHPFilter.html
You need a second order filter and if you start with a capacitor value of 0.22uF it gives sensible resistor values.
Do not agree with last poster you need a solid state amp to give the bottom end grunt!
GraemeC said:
The series resistance is used to include things like the output resistance of your amp, the resistance of the speaker cables and crossover inductors. This extra resistance alters the effective system Q. I am sure WinISD has a method for including this in the simulations, but I am not familiar with the program.
Your initial simulation is as expected. Adding the series resistance will lower the damping at LF, effectively raising its ouput while attenuating the midband. A resistance value can be found that will make the response flat.
The chief drawback is that it requires a bigger box than you would like to take advantage of this effect.
Whether or not a SS amp or a tube amp performs better will depend on the box size and tuning. I don't think it is possible to say one will always be better than the other with this driver. In some cases, a higher output resistance (like in some tube amps) will give a flatter and deeper bass response.
It is possible that those who say a SS amp is required are listening to underdamped alignments. A valve amp may make this problem even worse and it may make a flat alignment slightly underdamped.
Hi Graeme,
DO NOT use a unity gain S&K filter. The maths for different Q values is terrible. The component value selection is even more difficult than the maths.
Use the equal value S&K with the variable gain. Once you see the schematic the Rupper and Rlower for gain setting will become obvious.
DO NOT use a unity gain S&K filter. The maths for different Q values is terrible. The component value selection is even more difficult than the maths.
Use the equal value S&K with the variable gain. Once you see the schematic the Rupper and Rlower for gain setting will become obvious.
Hi Andrew
Have just spent the last two weeks or so trying to digest the National Semiconductor Applicaton Notes that you recommended. Heavy going as I am learning the physics behind the maths as I go. I think we are on a useful track.
When I tried to log onto Burr Brown I just got diverted to Texas Instruments who apparently have taken over Burr Brown. Could not find the "ab's" on the TI site, or guides to opamps in terms that I could understand.
Similarly, when looking for "Wjung opamp guide" I got books on Amazon, etc.
Now I am stuck on trying to evaluate what specific opamp would be optimal. Or at least avoiding those that could be disastrous. My knowledge is basically zero!
This is turning into a far deeper intellectual exercise that anticipated
Cheers
Graeme
Have just spent the last two weeks or so trying to digest the National Semiconductor Applicaton Notes that you recommended. Heavy going as I am learning the physics behind the maths as I go. I think we are on a useful track.
When I tried to log onto Burr Brown I just got diverted to Texas Instruments who apparently have taken over Burr Brown. Could not find the "ab's" on the TI site, or guides to opamps in terms that I could understand.
Similarly, when looking for "Wjung opamp guide" I got books on Amazon, etc.
Now I am stuck on trying to evaluate what specific opamp would be optimal. Or at least avoiding those that could be disastrous. My knowledge is basically zero!
This is turning into a far deeper intellectual exercise that anticipated
Cheers
Graeme
Hi,
I cannot avoid the arithmetic if I want to follow what's going on.
I have an alternative, that I don't recommend, follow blindly and hope for the best.
Have a look at app note 26 http://www.national.com/an/OA/OA-26.pdf#page=1
you may find this more comprehensible.
It was in the list I gave you, have you printed that list off and paper filed under "filters"?
BTW,
ignore the opamp suggestions, they are all aimed at above audio frequency usage.
Can you locate the build instructions for the filter Group Buy? It contains the formulae you NEED with the schematics and how to implement on the Group Buy PCB. I think there are some opamp suggestions in there.
I cannot avoid the arithmetic if I want to follow what's going on.
I have an alternative, that I don't recommend, follow blindly and hope for the best.
Have a look at app note 26 http://www.national.com/an/OA/OA-26.pdf#page=1
you may find this more comprehensible.
It was in the list I gave you, have you printed that list off and paper filed under "filters"?
BTW,
ignore the opamp suggestions, they are all aimed at above audio frequency usage.
Can you locate the build instructions for the filter Group Buy? It contains the formulae you NEED with the schematics and how to implement on the Group Buy PCB. I think there are some opamp suggestions in there.
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