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07-02-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	21
Post ID:	23275
Reply to:	23274

Please excuse the mess

Romy, thanks for the explanation.

I was not sure if you still kept an eye on that thread Romy. As far as I know you need to be logged in to view the images in the diy threads so I will post a couple here to show where I am up to with the build (please excuse the mess). These are taken with the first rays of morning light streaming into the room this morning...

Morning Glory Side2.jpg

You can see the little 2-way standmounts that I am currently listening to behind which are the 'wings' onto which I will build the DSET. My recently completed equipment rack holds my dac, the linestage, audio computer and tuner. The dac is sitting on its vibration platform that I built and shortly I will have three more built for the other shelves.

I've been in a conundrum with the preamplifier. In the past I have never been happy with anything that I have tried and as a result have direct connected my dac to amplifier, but I do love my FM and find that if I have to change cables that I just stay listening to the source that is playing and don't listen to the other. In desperation I managed to find a second hand Placette Active Linestage but when it arrived I was quite underwhelmed by the hit to dynamics and some problems with HF in particular. As you may recall, the Placette does not have feet of its own (at least mine has no feet) and since I recently completed the audio rack I plugged the Placette back in and sat it on a towel and it does sound much more capable than I originally thought. I am hoping that once I get it on one of my anti-vibration platforms that I will hear in it enough potential to persist with it and try to make it work better. It is quite surprising how much difference the rack with damped shelves and the towel to further decouple it has made to the sound.

After I get through this round of steel work I will return to the lathe to finish the Upperbass horn and then will will the DSET in the spring when it is warmer.

07-03-2017

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Romy the Cat

Boston, MA
Posts 10,166
Joined on 05-28-2004

Post #:	22
Post ID:	23276
Reply to:	23275

A warning and disbelive...

anthony wrote:
You can see the little 2-way standmounts that I am currently listening to behind which are the 'wings' onto which I will build the DSET.

This is perfectly fine but if you willing to experiment with any low power SET (including Milq) then be very careful with this approach. Some of the small two way monitors have relatively badly defended tweeters. They are fine when you drive them with high power SS amps but driving them with low power SETs frequently kill the speakers. You see, when you drive the 90dB sensitive monitors with a few watts you drive the amp into clipping. You might not recognize it from listening (it take some experience to hear it) but as the clipping take place SET generate very nasty HF high order distortion that kill some tweeters topologies. The tweeter might not burn but rather gets very ugly “burned-type” of sound. Then the tweeters need to be trashed as it is not recoverable. So, by-amp only and do not use SET on your monitors.

anthony wrote:
I've been in a conundrum with the preamplifier. In the past I have never been happy with anything that I have tried and as a result have direct connected my dac to amplifier, but I do love my FM and find that if I have to change cables that I just stay listening to the source that is playing and don't listen to the other. In desperation I managed to find a second hand Placette Active Linestage but when it arrived I was quite underwhelmed by the hit to dynamics and some problems with HF in particular. As you may recall, the Placette does not have feet of its own (at least mine has no feet) and since I recently completed the audio rack I plugged the Placette back in and sat it on a towel and it does sound much more capable than I originally thought. I am hoping that once I get it on one of my anti-vibration platforms that I will hear in it enough potential to persist with it and try to make it work better. It is quite surprising how much difference the rack with damped shelves and the towel to further decouple it has made to the sound.

Sorry, I do not buy it. I do not deny the contribution of proper feet under a component of a popper isolation platforms but the difference should be not even near at the magnitude you describe. It cannot go from “underwhelmed” to “much more capable” if you put it on a better feet or into a better rack. If you are positive that the difference was as dramatic as you describe then I would look for other variables: like electricity change between two listening sessions or etc… Generally if the Placette works properly then it would be more transparent than any other component you have, at least it is my case, and it is possible that what you do not like in the sound of your power amp, front-end or anything else. It is hard to debug your playback remotely and I do not know what you use. You can very easy to conduct the Placette bypass test to confirm that it has no own impact. If you have a hit in dynamics and HF with Placette then you do want to experiment more with it as I feel you do not use then Placette properly. I did not see any preamp that do not eat dynamics …except Placette. As far as HF concern… the Placette runs video signal with low distortions, which is a few mHz!!!I personally do not find any problem with Placette HF with only exception of some “coldness”. It takes time to understand that the Placette coldness is not own coldness but a lack of the HF euphoria that we are so accustomed in hi-fi. Using less colored amps, tweeters, proper HF crossover, time alignment and cables will convert the “Placette coldness” into Placette’s neutrality. This is at least my finding. You might not come to the same conclusion, wish is fine. You might use any preamp of your chose but if you are going to go with Miq DSET filtration at the aps input then you would need a preamp the can drive a lot of current and that has VERY low output impedance. You will have difficulty with typical 200R-300R output impedance that is fine to drive a single loading resistor at the apm’s input. The Milq DSEt will have 6 filter by 30K each connected in parallel. You will need a VERY powerful output stage to drive all of it. The vest would be to have output impedance near 0R, kind of a short circuit, or a preamp with a positive current feedback but this is an exeriment for another day… :-)

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-04-2017

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Jorge
Austin TX
Posts 141
Joined on 10-17-2010

Post #:	23
Post ID:	23277
Reply to:	23276

Metal pipes

Hello Anthony,
I did experiment with metal tubes for bass in a sealed configuration as you are planning. The weight of them, even made out of thinner than you would like steel, is prohibitive. If you make them out of aluminum pipe, then it could be better, but still pretty heavy. The stack will probably be unstable and shakey.
Do not try to place them one further than the other, or not perfectly aligned, the bass will distort terribly, cancellations will cause a mess of the sound, remember they will be playing the exact same frequency. (I did that and learned from the experience)
Of course they look much better than the boxes with the added benefit of difussion of sound waves hitting on it, against the reflection from a flat side panel of a box, so there are a lot of considerations you must make.
The bass modules I am using now are actually a form of concentric tapped horns using a long excursion 8 inch woofer servocontrolled by a powerfull class D amp. These are a redesign from the original, longer, passive bass modules which sported a 6.5 inch woofer. I am using one per side now.

07-04-2017

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Romy the Cat

Boston, MA
Posts 10,166
Joined on 05-28-2004

Post #:	24
Post ID:	23278
Reply to:	23277

For sure my opinion shall means very little....

Jorge, your comment about the physical instability of the pipe stack is well taken. I think if it is gone from metal then it is possible to make it steady. In the way how Antony want to do the pipe feet I think it might be possible to run guy wire to the top of the pipes hip and to anchor them this way. I am sure the people who are good with industrial design in metal can come up with some solution, it was never my objective to think about it deeper. For sure the design need to be safe and to be more or less portable. It is not the last factor is that it has to be earthquake proved. It sounds ridicules but you do not want to have a minor earthquake and to find your speakers flying to the floor and crash your amps and tonearms.

I never was a huge fun of the pipe design that you and Anthony looks like embrace. There is none contestable topological advantage that the pipes might be aligned in a curve to make a very perfect time alignment. This is given. How practical it is I do not know. I think it need to be aligned one pipe a time, starting from the bottom during the pile assembly… Another point is the sharp rollback from the back wall. The pipe design will have a permanent sharp enclosure mode deriving from the one single reflection surface. The pipe des has it as well but there are many reflection surfaces and the modes are kind of defused. With the pipe I think the reflection mode should be only one and it should be more prominent than with box. Saying all of it and understanding that you have good 2 inch foam in the box, or perhaps 4” in the back wall, not to mention that you guys run it all at very LF it is possible as well then my comment about reflection mode are purely theoretical and will be negligible in practice. I never experiment with pipes and do not know what work in them and what is not.

If I were building my system again from scratch and would follow the same topology then I would probably go with stackable individual rectangular boxes with one or with two driver, probably one. The construction of the sealed boxes is VERY not expensive and if you order them in bulk then you get a large discount. But it is me and I do not particularly fide the pipes being more attractive visibly. Also, I am not sure how metal enclosure would work for damping. For sure my opinion shall means very little for those who desisted to use pipes and I am sure that it to make the use the pipes as an objective and took this task seriously then it is possible to make the pipes to work out well…

PS: Jorge, update you email adders if you would like to get your subscription notifications, you current email is bouncing.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-04-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	25
Post ID:	23279
Reply to:	23277

The pipes, the pipes are ringing...

Jorge wrote:
Hello Anthony,
I did experiment with metal tubes for bass in a sealed configuration as you are planning. The weight of them, even made out of thinner than you would like steel, is prohibitive. If you make them out of aluminum pipe, then it could be better, but still pretty heavy. The stack will probably be unstable and shakey.
Do not try to place them one further than the other, or not perfectly aligned, the bass will distort terribly, cancellations will cause a mess of the sound, remember they will be playing the exact same frequency. (I did that and learned from the experience)

Hi Jorge,

Thanks so much for chiming in. It is nice to hear from someone that has been where I am going with this.

For this project I am not letting the weight of an object concern me. I have a very strong floor in my room and with some careful forethought I should be able to drag heavy items around by myself (or perhaps with a friend if really required). To date I have made 5 pipes, each 263mm diameter (10" or thereabouts) with 4.8mm wall thickness and 10mm welded endplates. They feel like they are about 30kg each which is very manageable, and by the time I damp them and install the driver perhaps they will reach 40kg each. I feel that this is manageable, especially because I have limited by the size of things that I can get into my room and I can carry one cannon at a time into my room.

I did wonder a little about cancellations and will experiment with it when the time comes, but thanks for sharing your experience.

Jorge wrote:

Of course they look much better than the boxes with the added benefit of difussion of sound waves hitting on it, against the reflection from a flat side panel of a box, so there are a lot of considerations you must make.
The bass modules I am using now are actually a form of concentric tapped horns using a long excursion 8 inch woofer servocontrolled by a powerfull class D amp. These are a redesign from the original, longer, passive bass modules which sported a 6.5 inch woofer. I am using one per side now.

I am not sure that they look much better, they might by the end of it, but the construction methods agree with my tendencies and are in my comfort zone. The diffusion angle is quite a valid one I would think that in the back of my mind this was one of the reasons that I have decided to investigate the pipes design. They should diffuse "in phase" as well which is a bonus.

I have had the 5 undamped pipes sitting up in the corner of my room and have had to take them out because when I play very loud music the pipes are induced to ringing. They store and release that energy over time and add a metallic tinge to the sound. They are now downstairs until I can get them damped.

Jorge wrote:
Hello Anthony,
The bass modules I am using now are actually a form of concentric tapped horns using a long excursion 8 inch woofer servocontrolled by a powerfull class D amp. These are a redesign from the original, longer, passive bass modules which sported a 6.5 inch woofer. I am using one per side now.

They do look a nice design. My one overriding ambition with the Bass Cannons is to have a bass channel that I can drive with a full 6C33C SET amp. My transformer winder has prepared an OPT that will drive 1R to 9W at 1% distortion and 2R to 17W. Each stack of pipes will have a box at the back where I can experiment with parallel and serial driver connections. If I can get this all to work I think that I will have a truly unique bass channel if only it can be coaxed into good sound.

Cheers,

Anthony

07-04-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	26
Post ID:	23280
Reply to:	23278

Earthquakes

Romy the Cat wrote:
Jorge, your comment about the physical instability of the pipe stack is well taken. I think if it is gone from metal then it is possible to make it steady. In the way how Antony want to do the pipe feet I think it might be possible to run guy wire to the top of the pipes hip and to anchor them this way. I am sure the people who are good with industrial design in metal can come up with some solution, it was never my objective to think about it deeper. For sure the design need to be safe and to be more or less portable. It is not the last factor is that it has to be earthquake proved. It sounds ridicules but you do not want to have a minor earthquake and to find your speakers flying to the floor and crash your amps and tonearms.

In my 43 years of life living only in this part of the world I have never felt the ground shake apart from when a neighbour was geligniting tree stumps out of the ground when I was a kid. That looked so much fun but I was never allowed to join in!

But I do take your point Romy, and to be honest, based on what my experiments have yielded thus far and where I expect the cannon stacks to be placed in the room in the event of an earquake I think they would tilt into the wall and probably crush some gyprock, but I doubt they would bend or topple.

Below are a couple of images from where I have loosely stacked some cannons to try to gauge if the stack was going to be rigid enough...

Cannon Mockup 1.jpg

At 4 cannons high and with only two sets of braces (each without their gaskets) this cannon stack was rock solid. The braces are 10mm x 10mm steel with M6 double ended screws to bind them together. Of course as I go higher the situation may change, but I can stop at 6 or 7 or 8 with this design if I have to.

Cannon Mockup 2.jpg

After powdercoating I have experimented with the amount of ringing in the pipes and what level of damping I require. Below you see one tube with four sets of bracing applied, this time with the 2mm cork gaskets installed. The braces work as a 'pre-tensioning' device in that they apply considerable pressure to the tube which further increases the rigidity of the pipe walls. Adding the third brace really knocked the amplitude out of the excitements and decreased the duration of ringing and the fourth brace further improved the result. However, there was still some residual energy being released as ringing, quite low in amplitude, but still there. With four braces applied to the 4.8mm wall steel pipe, I would rate a knuckle wrap as the equivalent of doing the same on a 16mm plate of steel. I researched damping paints as well as automotive butyl rubber/aluminium CLD sheets and have ordered some of the latter to place inside the pipes to eliminate the last of the stored energy. Driver excursions as going to be quite small if I can get 6 or 8 tubes in a stack so I actually have high hopes that I can make these steel enclosures very inert for their purpose.

Cannon Ring.jpg

Romy the Cat wrote:

I never was a huge fun of the pipe design that you and Anthony looks like embrace. There is none contestable topological advantage that the pipes might be aligned in a curve to make a very perfect time alignment. This is given. How practical it is I do not know. I think it need to be aligned one pipe a time, starting from the bottom during the pile assembly… Another point is the sharp rollback from the back wall. The pipe design will have a permanent sharp enclosure mode deriving from the one single reflection surface. The pipe des has it as well but there are many reflection surfaces and the modes are kind of defused. With the pipe I think the reflection mode should be only one and it should be more prominent than with box. Saying all of it and understanding that you have good 2 inch foam in the box, or perhaps 4” in the back wall, not to mention that you guys run it all at very LF it is possible as well then my comment about reflection mode are purely theoretical and will be negligible in practice. I never experiment with pipes and do not know what work in them and what is not.

I will be experimenting with stuffing the pipes. At this early stage, I want to first see if I can make the enclosure inert and then move on to acoustic testing.

Romy the Cat wrote:

If I were building my system again from scratch and would follow the same topology then I would probably go with stackable individual rectangular boxes with one or with two driver, probably one. The construction of the sealed boxes is VERY not expensive and if you order them in bulk then you get a large discount. But it is me and I do not particularly fide the pipes being more attractive visibly. Also, I am not sure how metal enclosure would work for damping. For sure my opinion shall means very little for those who desisted to use pipes and I am sure that it to make the use the pipes as an objective and took this task seriously then it is possible to make the pipes to work out well…

At this stage I am not wedded to the pipes idea, but am wedded to the idea of a modular bass stack whether that be one or two drivers per box, steel or wood or some other material.

07-04-2017

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mats
Chicago
Posts 85
Joined on 09-18-2005

Post #:	27
Post ID:	23281
Reply to:	23280

Unwed Mate

Anthony, you crack me up!
After doing this absolutely amazing work in steel,
you proclaim that you are "not wedded" to the pipes.
I love that spirit. Most people would likely at this point
proclaim the unalterable superiority of the design,
and spend years trying to prove it.
I sincerely look forward to your findings.
I trust that your detachement will serve us all well.
Meanwhile, I hope you have time to play some music that
you love while creating!

Mats

07-05-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	28
Post ID:	23282
Reply to:	23281

Ex-pat?

Mats, your sig says Chicago but you type like an Aussie.
One thing I have learned in life is that you almost never get good results unless you stay objective. I just want nice soft bass...

07-05-2017

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Romy the Cat

Boston, MA
Posts 10,166
Joined on 05-28-2004

Post #:	29
Post ID:	23283
Reply to:	23280

Ok, it looks good now...

Anthony, these last images do give a perspective of the size that made me to feel much better and the pipes are sufficiently large. Purely from visual assessment then are twice larger then what Jorge did and I do welcome it. Frankly, and I have no idea why, when I see just an image from front of the types they look unpleasant to me. However, what I see the side view then they look much more attractive and more holistic. I have no idea why I feel this way. I think it they were my bass modules then I would position them with a slight angle to see the size of the pipes. Is it is funny to hear from a guy who just a few days back was bitching about the angling of horns? Anyhow, you will need to stuff the pipes with foam. It sound a bit contra initiative as you will be losing so important volume of the enclosure but it will be only visual lost. At the LF the foam will be acoustically transparent but it will help to damp the internal pressurizing of the enclosure. It is not about the damping of the walls but rather let the pressure inside to rise gradually, foam will be compressing and smooth the event when the force of the code will be equal to the pressure of the enclosure…

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

08-28-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	30
Post ID:	23374
Reply to:	23283

Testing of the first Bass Cannon

So, I have finally started testing a single Bass Cannon in my room.

First, I had to get the rigidity as high as possible and then damp the steel ringing as much as feasible. I used butyl rubber/aluminium automotive deadener on the inside of the tube which really worked well and then on the 10mm thick backplate and frontplate (that the driver screws into) I used the same vicoelastic polymer and 2mm aluminium CLD arrangement that I have been using to great success in the DSET power supplies and amplifiers. I did some hard knuckle rap tests and measured on my phone the amount of time to stop ringing and I have got it down to about the same as a double brick wall. There is a local speaker manufacturer that makes my standmounts that puts a lot of effort into low energy storage cabinets and my steel Cannon tubes are damped quicker than those and at a lower frequency. So rigidity and damping is good for these Cannons...I am very happy.

So I screwed in a driver and was concerned by the sound scratching and tapping the woofer made...it was horrible and there was obviously some energy storage or something similar happening. I listened to the radio and female voices sounded particularly horrible (yes I know they are being reproduced by a 10" woofer) although the effect was a little more veiled by music. I figured that a feedback loop was happening between the driver and the flat backplate of the cannon which contributed to the impression of energy storage and ridiculously long decays after the music stopped. So I cut some leftover fibreglass insulation into the circles matching the inside diameter of the Cannons and stuffed it in...instantly better...good in fact...and I was greatly relieved.

So next item was to do some impedance testing with various amount of fibreglass sheets in the Cannon. First up with no stuffing:

BC 0 Sheets.jpg

Look at that, the ringing is clearly visible at about 180Hz along with harmonics! So I added one sheet at a time so that I could identify when the ringing was damped and the effect on Fs and the peak of resonant impedance. Without boring you with every test, the backplate ringing was damped out with a couple of sheets of fibreglass and another couple further lowered the resonant impedance while adding the fifth started to increase the resonant frequency. At this stage I think that 4 sheets looks about ideal because it gets the maximum reduction in resonant impedance whilst barely raising the resonant frequency. Below is a graph of all 0/1/2/3/4/5/10 sheets of fibreglass stuffing in a single Cannon:

Using a low output impedance SS amp meant that the frequency response was barely affected by the various amounts of stuffing:

Frequency Response various stuffing 29082017.jpg

Frequency Response various stuffing 29082017.jpg

It all looks as expected from an SPL point of view. If I parallel 8 Cannons with 4 sheets of fibreglass stuffing the DSET Bass OPT will see a range of 0.8R - 4R, which is pretty good I think considering it is wound to drive 1R and I am yet to add resistance for speaker cable of which there will be a lot for this channel. The Cannons are tuned to 47Hz which is higher than I had wished, but adding stuffing has done nothing to reduce Fs but adding more and more does eventually raise it. I don't know if different stuffing materials would be able to help lower Fs, but it looks like I am stuck at 47Hz
For what it is worth I will do some testing with a fullrange Melquiades with the Bass OPT installed to see how a higher output impedance affects the SPL graph.

Below is a single Cannon ready for SPL testing in-room. I've not been too OCD about setting up to remove the room from the measuring equation, relying on a short gating to get some idea of what the speaker is capable of.
Its alive.jpg

08-29-2017

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Romy the Cat

Boston, MA
Posts 10,166
Joined on 05-28-2004

Post #:	31
Post ID:	23375
Reply to:	23374

That will be fun to experiment.

Looks fine, Anthony. I am not sure what resonance frequency tells you. Anyhow, a great advantage of your pipe topology for LF is that you will be able to pile up as many drivers as you need in order to hit the desired reference DB level. There is a tricky thing in it. After you properly damp your pipes (and I do not know how to do it properly) the LF will be very sensitive to the way how you load the Milq’s output stage. You want to idle the output stage as much as you can, still without losing gain and power. More idle = faster transients, more load = more harmonics and slower decay. Here is what the trick is. You presumably find a configuration of your drivers and loading and you like sound. You feel that you need juts + 3dB and adding 2 drivers will give it to you. However, adding 2 drivers will change the impedance of the entire LF section and will require a new transformer. So, what you might want to do is to your other Lundahl transformers to fine a proper lodging. Lundahl has very flexible remappable primary and secondary and you can choose any configuration you want. You can even put section in opposite polarity to ask as subtraction sections… very very flexible. You can do some crazy shit like connect all of your LF drivers in parallel, that will form some kind of sub 1R array and to wind a transformer against it. So, it will be a pross for you to find a proper loading, until you do it do not waste money for expensive LF OPT. You can make a large LF transformer with multiple taps of course but it might be a bit difficult as it will be very little wire in the transformer and you might not have the best core filling with each tap. Lundahl from this perspective is superb – each section in there is perfectly symmetrical and cover all bobbin.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

08-30-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	32
Post ID:	23376
Reply to:	23375

Free first order crossover

I realised this morning that I have done a "not-so-standard" thing in using leftover fibreglass batts for stuffing the tubes. The batts that I have on hand are high density batts, not the low density type of fibreglass that is usually used for stuffing speakers and it is having an interesting effect. Looking at the spec sheet of these particular batts they start absorbing at about 100Hz and really get efficient at about 250Hz and they are having effectively acting as a low pass filter for the channel. Completely accidental of course.

Think of if this way. The backwave from the driver is goes back into the tube and because it is a subwoofer the low frequencies push straight through the fibreglass and some of them are reflected back to the driver and some of them pass through the walls of the tube and into the room...there is no way to stop this and it is what it is, but the more rigid the tube is the less sound that will pass through it. Because the rear of the Cannons will be placed against a wall the sound that passes through the tube wall and the sound that wraps around the baffle (or no baffle in this case) is reflected off the back wall with a 5.8ms delay or phase shift. However, the high density fibreglass inside the tube starts attenuating the backwave at about 100Hz and I have reason to believe that almost all of the 200Hz+ backwave is absorbed (the resonance of the pipes is about 190Hz and this is completely removed). So we have no attentuation of the backwave in the tube at 20Hz, a bit starting at 100Hz and full-on attenuation at 200Hz...that is a low pass filter with the knee set at about 100Hz which is just perfect for this application because this is approximately where the line level low pass filter will be set.

As I mentioned earlier I just used the fibreglass that I had on hand, but it does a good job of removing a lot of out of phase energy above 100Hz which I think is a good thing, while not affecting lower frequencies. So I think that I have just found an unintended benefit of the tube or Cannon topology.

08-31-2017

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Romy the Cat

Boston, MA
Posts 10,166
Joined on 05-28-2004

Post #:	33
Post ID:	23377
Reply to:	23376

Hmmm… I can’t comment on this.

Hmmm… I can’t comment on this. I never played with pipe and I do not know what works and what does not in there. I think to worry about high pass filtration via the foam inside the pipes is not what I would care. The foam in there to virtually evened the size of the enclosure and therefore to drive resonance frequency down. The resonance frequency itself does not say much and what does, in my view, is how and what the sound drivers produce. I know the drivers very well and I always appreciate in them softness with which the can play bass. It is a bit contra-intuitive and everyone is looking for had-ass bass and a lot of punch. It is very easy to get it from this drivers, just drive it with some kind of SS crap. To get the driver to play fast attack with gentle release is VERY hard. In my view those driver is they are properly loaded can produce very good result in the fast-attack -gentle-release department. The amplification just need to be right and the loading need to be very sensible. If I were you I would male at this point the pipe hollow and empty (juts a smalls layer perhaps) and would think about the specifics of damping by filler after the LF amp will be in place.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

08-31-2017

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martinshorn
Germany
Posts 114
Joined on 04-14-2017

Post #:	34
Post ID:	23378
Reply to:	23377

TSP related

Hi Anthony. No miracles. Round shapes happen to be far more rigid than flat. That will also increase the pressure on the flat opposite plate, which has to be of quadruple stability. You can easily eliminate this by the so called impulse compensation of installing one more driver on the opposite of the pipe. Alternatively a long rigid metal bar tension connecting plate and magnet.
Anyhow this is less a wall instability interference, but rather a reflection. At 180 cycles lambda/2 equals about 3 feet. Stuffing eliminates that pretty good. Long layers in small closed cabins let the standing wave decrease way more than the free field absorband spec assume. Especially that absorbency of 0.3 are sufficient already.
Stuffing influences TSP easily predictable when u check via TSP calculator playing with your given cabine size multiplied by 1.1 or 1.2 up to 1.3 for heavy stuffing (proven to be most common values). How much it lowers the fs depends on the VAS, meaning indirectly the suspension stiffness. If you got low VAS, like 50 or less, it wont influence much anyway. But it gets you Qts down which may look like a hipass, but actually just lowers the knee of the filter while increases xcursion on the subsonics. Still a highpass second order, just lower Q.
A little side note from my side: i happened to find the Sound more boring and tired when stuffing, though the measures are better. Cant explain why. Id rather try to avoid stuffing but stay away from the resonance with my passband. Alternatively use little stuffing only which decreases the ringing already dramatically (ideally in the middle of the pipe just a piece of foam, most efficient in the middle!).
Cheers, Josh

09-02-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	35
Post ID:	23380
Reply to:	23378

Improved stuffing

Thanks Josh,

I tried the "stuffing in the middle of the pipe" and with 2 sheets in the middle managed to get very similar results to 4 sheets placed at the far end of the tube, but with a steeper SPL curve. I then tried lower density stuffing and managed to remove most of the ragged SPL response above 150Hz (it also had a tidier impedance response in that region) so I am now on the hunt for lower density stuffing to see if that is going to improve things further.

The lower density polyester wall batts also managed to reduce Fs as more were added, and it looks like I may be able to keep Fs at 45Hz or thereabouts with a drastically lowered resonant peak which will help things when I start testing with a Melquiades LF amplifier and its higher output impedance. I have a room node that may be easier to manage if I can get that Fs lower in frequency, about 40Hz would be optimal, but I don't like my chances of getting there with the use of even less dense stuffing. We will see.

Cheers,

Anthony

09-02-2017

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martinshorn
Germany
Posts 114
Joined on 04-14-2017

Post #:	36
Post ID:	23381
Reply to:	23380

Such trials are fun

hi anthony, have fun with that, results are worth it.
Your findings don't need to match mine but i share my favorite briefly Smile

I found explanation from an famous german engineer. Hes calculating an Rms thiele small to indicate mechanical friction losses in drivers. He found that some sound tired and boring when having hi loss.Its got common ground with stuffing in my opinion and explained my impression. So if i had your tubes, id stuff a hi density foam disk into the middle of the pipe. Same diameter, maybe 10-20cm max depth. Hi density breaking fragile foam, like 10.000-15.000 density. Which is highly effective, eg sold by BASF as "melamine foam". That could be the minimum damping just to kill the ringing to a neglectable level. Rest of the pipe id keep blank. Also install the foam disk rigid in place not to move under vibration. Just my 2 cents. Was experimenting with a Lowther driver that got very "transparent " membrane and so very sensitive to cases and stuffing. Thick n heavy woofer may react less sensitive.

09-03-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	37
Post ID:	23382
Reply to:	23381

The melamine

As it so happens I have some melamine here and I cut up 5 x 1" thick discs and pushed them into the middle of the tube (I also trialled 1 disc and 4 discs) and while they removed the resonance they did the same thing as the high density fibreglass batts in that they created impedance wiggles from about 100Hz+. These impedance wiggles transferred into SPL wiggles and I doubt that they will be a good result. Also, the closed cell and hardness of the melamine seemed less effective than the other stuffings at absorbing frequencies over 200Hz, but I am glad that I tried it.

Based on my measurements thus far, GreenStuf R1.5 Wall Batts (a low density polyester fibre) placed at the midpoint of the tube seem to do the best job at providing a smooth impedance and frequency response in the 100Hz+ region whilst also eliminating the tube resonance, so that is the direction in which I intend to pursue.

Thanks for your help Josh.

09-03-2017

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martinshorn
Germany
Posts 114
Joined on 04-14-2017

Post #:	38
Post ID:	23383
Reply to:	23382

Don't forget the ears

hi Anthony. Don't forget to make a brief listen with the stuffings. I predict u might be surprised. Especially with focus on "live sound", soul, tapping feet, joy etc... crunchy beat vs fat slow base Smile

10-01-2017

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anthony
Posts 338
Joined on 08-18-2014

Post #:	39
Post ID:	23432
Reply to:	23383

The half-stack

I have finally put together a half-stack of my Bass Cannons concept.

Half Stack Side.jpg

The four Cannons wired in parallel and stuffed according to my previous trials on a single tube end up with Fs=41.7Hz and an impedance response as shown below...

Half Stack.jpg

...which means that when 8 Cannons are in the stack the impedance will vary from 0.85R to 2.9R at resonance which nicely suits the Bass OPT that I have here. To test the half-stack I soldered in the Bass OPT to the prototype Melquiades circuits and took some measurements and did some listening. The SPL response is quite linear which is good and the cabinets behaved themselves when I played sines between 10Hz and 100Hz...not many vibrations and steel ringing very well under control. In comparison to the small 2 way standmounts I have here the sines were easy and uncompressed and undistorted to listen to, a really huge difference in tone and yes, I was pushing the two way harder than it would like, but the volumes were similar.

Although not really fair, that little test has driven home to me just what these Cannons can bring to my audio. Only fools listen to sine waves but in this instance it was very instructive and helped me out in a "you've made all this effort but does it actually do what id needs to do?" kind of way. Yes, they work, and they are a quantum leap forward from those little standmounts.

Here is the prototype Melquiades and the big bass OPT pushing sub 2R into the half-stack...

Ah valves.jpg

So, at this stage it looks like the Bass Cannons project is a "go" to finish. They actually look pretty good in the room, and you can see that I have begun by time aligning them for a 2.35m listening distance.

10-02-2017

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Romy the Cat

Boston, MA
Posts 10,166
Joined on 05-28-2004

Post #:	40
Post ID:	23434
Reply to:	23383

Looks VERY good.

I need to give it to you and I need to retract my comments about your bass pipes. I did find them to be ugly in your prototype drowning but assembled I find them look very present, in fact quite wonderful. Connection al, of then in parallel is good and bad. The good part is that drivers will not work over each other, the bad part is that you need a very precise match of Milq output transformer to drive them. It is a .2-.3 of transformer ratio in this or that direction and you will be losing dumpling. I hope you have a lot of tap in your transformer. In some way it is convenient to connect them in combination on order to have a conventional impedance and then you can tray many non-custom transformers.

I am glad you made the Melquiades prototype. Drive your bass section with 0dB digital (max that your DAC outits) and see the voltages you have at grid of first tube and how close the output tube approached to class A2. With 6C33C you do not want to enter A2, I would advise to stay under 85% of A1. Load your bass array, drive full power and get sympatric clipping on your Milq output stage. Then get with your RTA sweep and see if your 4 driver can load the room. If you have no enough gain or power then add another pair of your bass tubes. You understand that the more you put the tubes in duty then easier it will be for everything. Still, you might try it even now. I did not know your room and if you have let say -12dB at 40Hz then the given amp or LF section might not be for your room. There are many options if it is the case, like switching from 6C33C to 211 or GM70 but I thing if your room is not over 10000 sq feet then you should be fine with a reasonable amount of bass drivers. My current room is about 550 sq feet and I get a full 20hz from 6 drivers…

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

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