Rakesh reminds us of the decision to "go long".  Romy, how much wire has been involved with the testing so far?  Very long runs often present their own problems, including similar to what you have described.  I would schlep the B2 over to the horns and at least try them with short runs before I tore anything else apart.  Feed it with a laptop if you have to.

Best regards,
Paul S

Romy the Cat wrote:

It is was not bad sound but the sound that clearly indicated that something is very wrong: supper compressed, complete absent of LF, huge HF extension. The whole horn sounds like a bad MD driver.

Romy the Cat wrote:

I mean the driver from 14Hz to 150HZ gas absolutely linear impedance as it has no active load. I look at all of it and felt so tiered and I walked out if it. I think in the new room the horn is shooting into the wide open sealing and see no reflection  and all my back chamber calculation and testing the worked so great for horns in basemen is absolutely not applicable now.

unicon wrote:

Roman,  I suggest that you do add the mass in driver like coins in driver cone(and measure the coin weight too) and do added mass free air impedance test then you can see where it can bring another low resonance .then when it reaches 20% lower the free air you are getting the most out of your driver  .so in loaded horn you can be sure how much foam to add and having the goal impedance you can be almost sure everything is right. and i suggest not to try more than 20%

OK, this morning I tuned the playback and did some listing, trying to understand what was the problem. Sound was not just bad but it was very strange, it was almost as a mechanical replica of sound. I took my phase meter trying to set horns in phase with the rest of the system and I was shocked how the horns reacted to the 2+1 phase pulses. Any speakers do it like claps but my horns presented it almost as VC was rubbing the gap. Also, the midbass horn did not react to crossover properly- it output pretty much the same horribly-compressed MF sound aka a telephone from 30s….. This was no what I was signed for.

I decided to poke a small whole in back chamber on one of the horns and to see if it would impact resonance frequency. I disagree with el`Ol that the foam I use is too soft. It tested many time – this type of foam for the purpose of filling back chamber is as good as solid brick. I made a small 1-2mm hole from the driver window to outside and measured the resonance – there was no fucking resonance. I decided that foam glued the cone and the game is over- I started to cut the foam to replace the driver.

When I reached the level of fabric cover the window I realized that the fabric was not perpetrated by foam and the driver’s diaphragm was in absolutely intact virgin state. What the hell – I was asking myself. I opened one whole basket‘s window and measured the resonance frequency.  To my huge surprise I did see the resonance now. It was 54.6Hz. I need to mention that the resonance was nothing even remotely close to what I had in basement. In basement it was almost 50%, very sharp impedance dive, her in the room,  it was more like 5-10% and very smooth dive. I took foams from one more window - 52Hz. Eventually I took all non-compressible foams out of the chamber. The resonance drooped to 50Hz, or to the resonance of the driver in open air. Then I opened the back chamber lid wide open. The resonance dropped to 43.7Hz. That was already something but I needed a few more Hz, and I would like to keep the primary resonance just under 42Hz. I decided to fill the back chamber with compressible foam (furniture foam) that shall virtually expend the chamber volume. Laying the chamber with furniture foam made the resonance to rise to 47Hz. I deseeded to keep the back chamber wide open for now with 43.7Hz of primary resonance.

I reset the playback to run from generator to preamp and give it a try to play music. Here it was – the bass was as it had to be in its shine. OK, what does it all means?

The events I describe are hugely educational.  As now I understand I did wrong the size of the back chamber - it had to be as I initially thought - the 3 sizes of the driver total volume. However, disagree with the criticism that I did anything wrong. What I did was the only methods I trust in loudspeakers design -following my own empirical results.  In the middle of the thread I did tell that the reflective condition in the listening room will be different then reflective condition of the basement and the horns will “read” the walls differently.  That is why I thought to make the adjustable back chamber – to fine-tune the chamber after the horns will be installed. What I did not know and did anticipated was that the amplitude of the differences between room and basement will be so huge. The super small size of the back chamber was absolutely right for the basement location but absolutely incorrect for the room where horns see no reflections of any kind. A 50Hz driver shooting toward to wall via a horn like mine experience throat reactance that made resonance drop to 24Hz. In open air however it the drop goes to 43.7Hz. This is indication that throat reactance is not only derivative of the air mass in the belly of the horn but also hugely moderated by the reflective characteristics of the room profile.  I generally know about but I have no idea that the degree of this moderation might be near 100%.

This experience of mine give a huge room of thoughts, explanations and doubts. Generally people do not talk, do not think, and do not question it. What you can see on-line is a person make a picture of his shiny horn but no one question how the horn sound and what ingredients made it’s sound. I question everything and I expose everything in this thread. One might by $40K Goto bass driver, or some exotic bass electromagnet and feel that hell all set but did you ever see those people ever question or publish own resonance frequency of  their horns.  Without know the bass horn resonance frequency and ability to moderate it for a give location a bass horn in pretty much unturned instrument that produces absolutely accidental result. I wish that this conclusion would be a legacy of my projects.

Anyhow, it turned out the in my horn, shooting in non-reflective room pushed the Vitavox driver to it’s limit.  The 43.7Hz is a bit short but the driver has no cone mass to go lower. I would like to find a way to drop it for 3-4 Hz lower but I am hesitant to glue anything to the driver. The back chamber is open and I need to devise some kind of thermal solution to unclose the driver that would not impact the resonance.

At this point the midbass channel is more or less operate properly. It sounds fine and here is the frequency response of left Midbass after a 70Hz low pass 6dB filter.

I might start to work on the midbass sound and on the midbass integration with Macondo. I need to mention that Macondo since I moved to the new room did not have any proper setup done. Now I need to review the enter Macondo in context of the Midbass channels and the ULF channel. Midbass now a lot of louder then Macondo, 7R resistor set it equal but I am not sure how I will reduce the Midbass volume. I would like to do it by dropping loading of the Midbass out transformer. I think it is too early to think about it, I need to revise many other things. For whatever it worth he is the Macondo’s left channel raw initial sweep, for each channel but without the Injection Channel. It sure will be see a lot of work and will be a lot of better.

Now it will be interesting time – a lot of listening and a lot of thinking, No more wood cutting and dust.  That will be in way very interesting time – to make Melquiades, Macondo and the Room to sound properly. Even as now, listening what they do, I do see a lot of potential but it for sure need to have a lot of fine polishing of sound. As my carpenter do some minor cosmetics modification this well I will put the room treatment in the game and for now I am beginning to work on new crossovers.

unicon wrote:

what you did in your horn :  you coupled your horn and you added mass on cone. then imagine when the cone tried to make an impulse it moves forward and then in back chamber something stops it from moving(air pressure+-) your driver had been stopped from moving from back and horn chamber.

Yes, I did, it is a normal practice in my view how to tune back chamber. I did nothing more then follows my own guidance how it need to be done:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=2991

unicon wrote:

I suggest make you back chamber as large as you can or just make it infinite chamber like or isolate the back roof side areas.

Come on unicon, get some practical perspective on the subject. The measurement of the horns in semi-assembled state in the basemen was an attempt to get an APPROXIMATE back chamber size, in order to guess what to build. Of cause it would be great to make the back chamber “a large as you can or just make it infinite chamber” but when you have a carpenter who ask you what the demotion of the specific surface shall be then we need to stop operate by imaginary concepts and be very practical. The whole idea to make a test chamber that I have built and to find it’s size when the resonance frequency would be too high and too low. It is what I did and from that I intimated the back chamber size. Who knew that the reflections in the basement were so effective? I would refer you to my old post I made 3 days before we started the project:

http://www.GoodSoundClub.com/TreeItem.aspx?PostID=13990   

I very much questioned how the resonance frequency will change at floor level where I could make experiments to the cathedral ceiling level. I thought it would be 5Hz difference, but it turned out to be 22Hz difference. Well, now I know, now even you know….

unicon wrote:

in my idea in infinite chamber you can avoid some unwanted resonances like that  125 315 hz( if its not due to your horn mouthing sizes )

Hmmmm, I do not think so. With open back I do have infinite chamber, you can’t make bigger chamber then open air. I do not think that there are any correlations between the unwanted peaks you see on horn response and anything in back chamber. The peaks are most likely are room related and has nothing to do with horns and impedance on those frequencies is dead stable (I tested it). Sure I would need to find a way to deal with the peaks and most certainly with the 100Hz suck out but it will be a very different subject and it will hardly had anything with the back chamber. BTW, my carpenter did propose me last night to add a few feet of the back chamber; the way how the back chamber was designed we did have a provision to let it to grow. I declined the offer foe now. Let see how it goes…

jessie.dazzle wrote:

The Velodyne SMS 1 will allow you to do just about anything, up to 200Hz.

jessie.dazzle wrote:

Is this because of the way you are driving them? When testing my one completed mid-bass horn (AK151 into 40Hz Exponential with 8" throat), and powering it from an amp that drives everything from upper bass to HF, the output was not noticeably louder than the rest of the horns. You have DSET amps and I am guessing that you ran the new horns form the outputs that once ran your direct radiating line arrays; is this the reason for the "excess" volume?

skushino wrote:

Have you considered the opportunity of raising your upper bass HP crossover?  How high do you plan to use your mid bass horns?  If your mid bass is comfortable playing up to 280hz (or whatever the right freq is), you can use your upper bass horn to play more conservatively, without trying to push it so hard for maximum amount of bass output.  You can use your upper bass more like a midrange horn, with a comfortable margin underneath.  When the upper bass was the lowest horn in Macondo, it had to be pushed.  Now with the big horns for carrying the load of your low channels, it should be an opportunity for the upper bass horns to be used differently.

Paul S wrote:

Romy, what is the un-labeled "box with dots" before the grid? Does the wiper track well enough near the top, and will this give you enough slack, to just use total R it as it is?

OK, as now, I see no problem to conclude to the project successfully in 1-2 weeks. The horn give much less problem then was expected, as my progress with crossover going on the midbass horns sound more and more disciplinized. Today I will be exploring the option to roll off the upperbass lower end vs. extending the midbass upper end. The crossover I use is not too comfortable for those tasks but I will survive it.

There is one aspect that at this point is not resoled and I would need to deal somehow. I do not have a position how to proceed at this point so, I will lay out all options. The problem is that my Vitavox 15 driver has too light cone/too strong suspension for this type of horn. The current setting has 43.7Hz of primary resonance. To keep everything as I understand it perfect I would like to have 35-40Hz primary resonance and then to lock it at 42 Hz with large a back chamber. With 43.7Hz I have no spare Hz to close up the back of the horn. So, here is the options I have how I might deal with the problem.

1)  Leave it as is. The 43.7Hz is near OK primary resonance for these horns. If I built a very large fiberglass-made sarcofague around the back end of the horns then I might be OK to keep horns unclosed from behind. This is what I am doing for now.

2)  Find another driver with free air primary resonance of near 40Hz. Possible and I can always do it in future.

3)   To glue to the driver some mass to drive the primary resonance down. This is not brainer was to do it but I have no collage how it will affect the driver sound. I am sure the motor will handle it but to impact the driver paper is a bit dangers. Also if I do it then what material and what techniques to use.

4)   Soften the driver suspension by soaking the outer spider with minerals. Again, it might fuck up the driver, not to mention that it will be stiffening back with time goes by

5)  Introducing artificial impediments in the mouth or near the mouth that would reflect a part of the horn pressure back to the horn belly and introduce more aggressive throat reactance. This will drive the primary resonance down but it might also modify the sound of the horn.

6)  Trying to change loading of output tube of the amp the drives the midbass horns. Currently the 6C33C is load to 1500R with midbass horns. I wonder if change of loading will slightly alter the primary resonance

If anyhow know any other ways to drop primary resonance then, please, advise.

Romy the Cat wrote:

To my huge surprise and pleasure my midbass horn has absolutely no honk. I heard bass honk in ANY, even the best midbass horns that I heard (BTW, some honk does not bothers me and I even consider it desirable).