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  »  New  Macondo's Axioms: Horn-loaded acoustic systems..  No wonder...  Horn-Loaded Speakers Forum     72  392975  07-29-2007
  »  New  Jessie Dazzle Project..  Will this better to be auditable?...  Horn-Loaded Speakers Forum     172  1097556  08-03-2007
  »  New  Barn Conversion - James' Project..  The vintage vs. contemporary compression driver....  Horn-Loaded Speakers Forum     28  252518  02-04-2007
  »  New  Configuration from Italy: multisell++ and double model ..  In search of optimum.......  Horn-Loaded Speakers Forum     8  62741  01-02-2010
  »  New  Practical Guide for Back Chambers Tuning...  Back chamber’s cost-benefit....  Horn-Loaded Speakers Forum     5  49377  10-21-2006
03-16-2010 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 1
Post ID: 13167
Reply to: 13167
New speaker system
fiogf49gjkf0d
I recently completed some upper bass horns which I'm now enjoying very much. Sadly I lack the skills of someone like Jessie so my efforts are crude in comparison, but they are working well for me which is the main thing.

I already had some old frontloaded, folded horn cabinets so had a 3 way system of sorts running a while ago. I'd already chosen the JBL 2405 Alnico as my preferred tweeter & had acquired a pair from a church in the US. I'd been using the Vitavox S2 mid driver in a Vitavox 4 cell exponential horn until about 18 months ago when I bought some of the cast resin tractrix 400 Hz horns from Stereolab. These sounded more natural & played higher (being shorter) even if they are less impressive in some ways.

My problem was that both the S2 and the 2405 needed padding down quite alot, and that the folded front loaded 'bass' horn didn't really get up to 500 never mind 800Hz which was where I wanted to run the S2's from. The folds seemed to introduce uneveness in the response, arguably just behaving as a series of tapered sections each with its own problems. Such a folded horn also can't readily be time aligned with the mid horn although I suppose if digital were the only source, a digital x-over with delays to the mf & hf could allow for it.

The intention was therefore to make a straight horn & choose a driver which would get up to and beyond where I needed it to. Such a horn would also allow all 3 drivers to be physically time aligned. The mouth area was set by dimensions which would allow it through a typical doorway and the length was set by being at least a quarter wavelength of the frequency I wanted it to play down to.  I also thought it would be interesting to apply the Macondo axioms where possible.

The free software Hornresp was used to try several drivers & various horn profiles. I opted for a square section Salmon type horn (aka Hypex) and eventually settled on a particular Eminence 12" driver that seemed to give the required result.






The horn was made from MDF in 3 sections, 30, 40 & 50 cm long but approximates closely enough the profile that was modelled particularly when the joins are filled & filed smooth.









Back chamber





With driver installed



Initial testing



Some paint goes on.






I was pleased that the measured performance of the driver in the horn matched the predicted performance fairly well. The rolloff it does introduce has allowed me to simply series feed the MF & HF drivers via appropriate caps without any padding.

an early response plot, on axis with the S2 & stereolab horn.



The back chamber is sealed & partly filled. Adjusting this volume adjusts the Fs of the driver & how it reacts with the horn. I need to play with this some more. The back box is double thickness. Ideally the rest of the horn would perhaps be more massive but it seems to work well enough. It is pretty substantial where the pressure is highest. I perhaps also need to treat those drivers to some nicer series capacitors at some point.

Here in the UK we have a forum run show where enthusiasts can take their own equipment and set up systems. There were perhaps 45 rooms at the recent event so I and a couple of friends took a largish room (250 Cubic Meters) and set the horns up to play there. We used a home built 3W amplifier using the 6B4G to drive the horns and then a smallish XTZ subwoofer below. This Sub-woofer was really somewhat underpowered for the room, but despite that the result was good and the horns seemed well received. It did illustrate very clearly the demands a large room makes on LF systems. The horns had no difficulty filling that room but the bass system really needed to fill out beneath them would have to be quite large & capable.





I now need to find a relatively compact LF solution to go with them. I'm currently using a single, small active sub-woofer which just about manages in my 4.5 x 5m room. A proper LF will then give me the opportunity to high pass these horns and unload the bottom of what they do. I suppose the options include conventional active subwoofers, possibly tapped horns (although I'd like to hear some first ) but any other suggestions would be gratefully received.

I wish I was a better woodworker, but I can tolerate their appearance. These aren't the kind of project I'd pay a cabinet maker to do on the offchance that they would work properly. So I had to do it myself. 


03-17-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,495
Joined on 05-28-2004

Post #: 2
Post ID: 13174
Reply to: 13167
Welcome to the club
fiogf49gjkf0d

Guy, here some unconnected comments that you might find worth considering. They are in no order or importance, just random thoughts.

1)      Talking and describing about horn we shall always mention at least 5 mandatory characteristics

a)      Cut off frequency of mouth
b)      Diameter or surface of throat
c)       Profile and size type
d)      Crossovering used
e)      Driver

Without naming those characteristics the horn is described and to make a clear picture of what one does or trying to do is very difficult

2)      A proper LF solution will not give you an opportunity to high pass your bass horns and unload the bottom – it needs to be done anyway. In some case what the Fs is relatively high, close to the horn rate it might be arguable. In you care you use 100Hz horn (presumably) and a driver with resonant frequency of 50Hz (presumably). You will be able to raise the resonant frequency for 15-20Hz via your back chamber but it still will be a good 30Hz under your horn rate. I do feel that in this case the unloading of bass is necessary. If not you will not get more bass – horn will cut it off anyway but you will get worse bass in the region that the horn will pass

3)      If you (your wife) like a white colors for the horn then why do not finish the MF and HF channels in white? I think it does make send to keep the colors of the entire acoustic system consistent.

4)      The time alight you were trying to set is fine but I see that tweeters’ axis are not firmly fixed. You need to make absolutely sure that axis of your MF and HF channels are parallel and will not be altered by change. Any minute angling of those drivers will toss the time alignment away. You can ease test it and to see that a very minor change of angle of HF driver will offset your efforts for time alignment. I see that you have some kind of mounting plate on your tweeter. Use it and bolt the tweeter to the frame.

5)      How many DB you need to attenuate your MF channel in respect to you upperbass channel?

6)      You might consider driving your upperbass from a separate amp if the attenuation above is too high. Get for teat some kind of 50W SS amp and see what will happen. Be as that if you use high-damping SS amp then the influence of back chamber will be much more negligible. The result will greatly depends on the driver you use

7)      The 12” driver, what is the size of the throat? I guess it is 7” by 7”?

8)      In the response you posted I think you use a tweeter as well. Anyhow, I do not think that you will be listening on axis but most like at some angle. I would encourage you to discard and never use the on axis response as it has absolutely no practical meaning. The point I am trying to make that in all measurement it is critical to have a very direct relation between you hear and what you measures. If you do not use your horns axis then do not measure them on axis

9)      I would say that your MF-HF channels are a bit “in the wall”. I would like them to be more extended into the room if you have space. When MF horn will stop “reading  the walls” it will give you very pleasant auditable space behind the speakers.

10)   If you would like then you might consider adding one more channel – the lower MF channel, or something that I call a Fundamentals Channels.  In your case you might do it in very interesting configuration. Take a look. You remove your MF from the backs of the upperbass and point you upperbass channels to the walls.  Loading then die to the walls will give you an extra let say 10-15Hz of bass + you will have more mature bass. Then you move your MF island for 3-5 feet ahead and place it atop of a new Fundamentals Channel.  This new Channel might be some kind of Altec 288 driver in 180Hz hyperbolic rectangular horns. The Fundamentals will be running from 350Hz-450Hz to 800Hz-1000Hz and the rectangularity of the horn will not affect sound badly.

11)   In your current configuration your MF island does not look like aligned with your upperbass. The upperbass cone is somewhere at the beginning of the back chamber but in S2 driver the cone is in very back. So, I presume that you have a good foot that you might move your MF island forward toward to the mouth of your upperbass. In addition to the alignment it will make the system more compact and more proportional.

12)   The 3 sections of  30, 40 & 50 cm long – did you chose them by some kind of resonant modes principles or it was just an arbitrary decision?

13)   Bass section – this is difficult.  I also would like to hear the tapped horns but I did not yet. For a time being you might consider getting some kind of commercial high price subwoofer as a temp solution. Look for sealed only active devises of high price. Get 2 of them used, use then for as long as you need, and then sell them. You will not lose a lot of money but you have a good buffer for a time being. Among the commercial subs you might look at your British Rel Subwoofers. The do not shake room during those stupid films but they are relatively acceptable for music, this top of the line models.

14)   What was the total cost of your upperbass project?

15)   How do you joins the 3 sections – juts glue and why you decided do not brace them in the joints?

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-18-2010 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 3
Post ID: 13181
Reply to: 13174
More questions than answers!
fiogf49gjkf0d
Here are a few answers

1.   a, 84 Hz
      b, 4.8 inches square
      c, Hyperbolic exponential, T 0.8 1/2 Pi
      d, none so far on upper bass horn. S2 and 2405 have series capacitors feeding them.
      e, Eminence Kappa 12. 

4.  Both tweeter and S2 can be moved forward & backwards. I need to improve this upper frame really. this was just to get started.

5. I don't need to.
7. 4.8" x 4.8"
8. Useful advice, how do you measure the Macondo, from your listening position?
9. The main pictures were taken with the speakers at this hotel. I'll take your advice and try to bring them into the room some more.
10. I do have some JBL 2482's and was considering perhaps using those on the 140Hz Stereolab horns, although your 180 Hz Hyperbolic suggestion is another option. I do want to learn more about how to manipulate the elements I have first.
11. I'll try to do the time alignment more exactly when I put this system back together here this weekend. I've been too busy recently. I was interested to read JLH's views on this on Audio Asylum.  http://www.audioasylum.com/forums/hug/messages/14/148141.html  Not sure what to make of that discussion.
12. They were segment lengths that allowed me to closely enough follow the Hypex profile.
14. Alot of time, (I'm bad at woodwork) but only $150 in materials + 2 drivers at $99 each
15 PVA Glue & dowel pins between sections although how much strength they add, I'm not sure.




03-18-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,495
Joined on 05-28-2004

Post #: 4
Post ID: 13182
Reply to: 13181
Some more comments.
fiogf49gjkf0d

 guy sergeant wrote:
7. 4.8" x 4.8"

Hm, and you used 12” driver with 4.8" x 4.8" thought?  With you look for 6”-8” driver and Fs drivers. I know it would be very hard to find them with near 100dB sensitivity…

 guy sergeant wrote:
… how do you measure the Macondo, from your listening position?

Only, I absolutely refuse even to look at any other measurements.

 guy sergeant wrote:
I'll try to do the time alignment more exactly when I put this system back together here this weekend. I've been too busy recently. I was interested to read JLH's views on this on Audio Asylum.  http://www.audioasylum.com/forums/hug/messages/14/148141.html  Not sure what to make of that discussion.

What JLH says is correct but only enough to satisfy interest in the subject of the Morons of the “Dan_ed” level. John talks about acoustic alignment that is the only aliment that counts. Still, acoustic alignment is a way to monitor and to measure alignment but alignment itself is still done mechanically, by sliding drivers against each other. If cause no one line up the throats, people align diagrams refracted after crossover, or acoustic center of the driver radiation.  So, I do not see anything wrong or conflicting in what John said. I would not agree that time from diagram to listener means nothing but he was saying it as an illustration to educate the Morons that alignment needed to be measured acoustically not with a ruler. Ironically with a certain experience it might be measured by distance and the acoustic measurement might be discarded. But to do it one needs to know how the given channel and the given crossover measured time-wise and then if you have high precision positioning table then you can do aliment by distance only. Where I disagree with John is in his comment that horn’s phase response changes with frequency. Of course it changes but it is irrelevant for time alignment a multi-horn system.

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-19-2010 Post does not mapped to Knowledge Tree
zanon
Posts 54
Joined on 11-14-2009

Post #: 5
Post ID: 13187
Reply to: 13182
How can you eyeball alignment then?
fiogf49gjkf0d
Romy:

I learn something new today.

Let me ask this then -- when you see multiway horns, where the throats and openings are all over the place, I often see you comment "these people do not know anything about time alignment". I thought it was because you could see diaphrames were not aligned, but now I know better.

So, how can one tell visually whether multi-horns are time aligned or not? It does not seem possible given what I learned about phase when you have xover.
03-19-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,495
Joined on 05-28-2004

Post #: 6
Post ID: 13188
Reply to: 13187
Sounds like a hypocrisy, right?
fiogf49gjkf0d
Zanon,

I do understand the sarcasm you would like to express. From one side I insist the people are clueless based upon that fact that they have not aliened diaphragms and from another side I pitch that the perfect alignment might be accomplished only by acoustic measurement but not by geometrical measurement.  Sound like a hypocrisy, right? In fact it is not. The true time alignment might be described only by equidistant of diaphragms. Why in suck case I stress the acoustic alignment? Because the acoustic alignment refines degree of geometrical alignment. Geometrically measuring distances from diaphragms to listening spot we can set canals approximately in the same period. However, there is no measurement of distance that would allow you to set the sinusoid summits. You just do not know what is the acoustic center of the driver, how it was modified by crossover and other conditions. This is why John advocated acoustic alignment. However, what I see the Morons who spend no efforts to align drivers at all and place then a foot from each other then there is no even need to talk/thing with them about acoustic time alignment. There is one exception that mostly never is used by people and that I will later recommend to Guy when I have time to write.

Rgs, the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-14-2010 Post does not mapped to Knowledge Tree
noviygera


Chicago, IL
Posts 137
Joined on 06-12-2009

Post #: 7
Post ID: 13504
Reply to: 13167
One more horn speaker system to look at
fiogf49gjkf0d
This is a pro audio company that came out with a nice looking system, supposedly they are more about SQ than others:

http://www.voidaudio.com/product_detail.asp?id=42


Page 1 of 1 (7 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  Macondo's Axioms: Horn-loaded acoustic systems..  No wonder...  Horn-Loaded Speakers Forum     72  392975  07-29-2007
  »  New  Jessie Dazzle Project..  Will this better to be auditable?...  Horn-Loaded Speakers Forum     172  1097556  08-03-2007
  »  New  Barn Conversion - James' Project..  The vintage vs. contemporary compression driver....  Horn-Loaded Speakers Forum     28  252518  02-04-2007
  »  New  Configuration from Italy: multisell++ and double model ..  In search of optimum.......  Horn-Loaded Speakers Forum     8  62741  01-02-2010
  »  New  Practical Guide for Back Chambers Tuning...  Back chamber’s cost-benefit....  Horn-Loaded Speakers Forum     5  49377  10-21-2006
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