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  »  New  Problems with horns: upper bass ..  Must it be about loading?...  Horn-Loaded Speakers Forum     109  925979  03-25-2005
  »  New  Phase plug for midbass..  Ulf plug...  Horn-Loaded Speakers Forum     23  260341  11-08-2006
  »  New  The Macondo’s Upper Bass Channel: what is next?..  Görlich again...  Horn-Loaded Speakers Forum     30  214733  10-28-2007
05-25-2006 Post mapped to one branch of Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 1
Post ID: 2439
Reply to: 2439
Transition : Driver to throat, when throat is smaller than driver
Hello all :::: This will be my first post, and I am writing first to thank Romy and the lovely Koshka for making the results of their research available to others, and also to ask for help :::: I am something of a "New Horns Guy" (cringe !), as I am fabricating horns based largely on the information gathered from this and a couple other sites :::: In designing a lower MF horn (100 - 1000Hz) with no front (compression) chamber, I am confronted with the question of how to make the transition from a large diameter driver to a smaller diameter throat. The only examples I've seen have the driver bolted directly to a flat surface firing through a much smaller opening, with no transition. Maybe I'm wrong, but this just does not seem kosher to me... I would like to include images showing two scenarios of my work in progress, but with the new format of the site, I can't seem to find the post where I once saw instructions for loading photos :::: I will include them if I can figure it out later.

Thanks in advance,

jd*




How to short-circuit evolution: Enshrine mediocrity.
05-25-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,644
Joined on 05-28-2004

Post #: 2
Post ID: 2440
Reply to: 2439
Throat’s side thickness...

Jessie, at the home page, in the left, within the GoodSoundClub Section there is the “Announcements” item of menu, which will bring you to the thread with the instruction how to upload the images to the site.

Regarding the issues that you are trying to address. You are absolutely right and the throat’s side thickness is a commonly avoided acknowledgment subject. Ironically the throat’s side thickness is not only silent problem with the upper bass horn but also with compression drives. I have seen many of then that have internally a perpendicular surfaces that I personally believe shouldn’t be there. So, what to do with that Red Area?

I do not know. It is possible to make it as a contra-horn introducing a little bell in the opposite direction and making the deriver act as almost a compression driver. However it would essentially minimize the effective diameter of the cone. Sound derives from the perimeter of the driver diaphragm and by masking the outskirt of the driver you will change the driver characteristic. In which direction would it be? I do not think anyone knows… I do not think that there is anyone out there who was able to assess how different drivers with the different diaphragm profile, loaded into the different throat’s holes would sound. theoretically, purely theoretically the slightly larger  driver loaded into a throat create unavoidable front chamber. This front chamber acts as a first order low pass filter and as a resonator chamber with own completely unpredictable sonic qualities. If we add to the mix the reflections from the Red Area then we have a completely erratic behavior. The good part that all of it has to do only for higher frequencies and in your case when the horn will not be doing a lot of HF it might be irrelevant.

If you try to make the horn with 100Hz then the Fs of that driver should be around 1/3 octave below. For such a driver 1000Hz is handle-able but it might already that the driver might have a cone too heavy for 1000Hz. You have to listen it and see how it does. To make the Red Area as right and accusatorily abrasive as probably would be a good idea. Still it would have purely intellectual-logical purpose as I down that the stricture of this surface will be auditable at 500Hz. I ma very much be wrong and I look forward to learn form someone who has data regarding the subject.

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
05-26-2006 Post does not mapped to Knowledge Tree
JLH
Indianapolis, IN U.S.A.
Posts 42
Joined on 07-20-2004

Post #: 3
Post ID: 2445
Reply to: 2439
Re: Transition : Driver to throat, when throat is smaller than driver

JD,

I
n the case of the mid-bass horn, the throat transition does not affect the sound enough to worry about IMO. Due to the narrow bandwidth (100Hz - 1000Hz) the step transition between the woofer cone and horn throat is acoustically invisible. In order to have cancellation you need a reflection that is half a wavelength away from the source (i.e. the cone). The longest distance from the cone to horn throat is about 2-1/2 inches. This corresponds to half a wavelength at 2700Hz. So, our upper range of 1000Hz is in no danger of being screwed up by the throat of the horn. The 1000Hz wave is too long to "see" the throat transition. About the only thing one might wonder about is whether the upper harmonics that help to develop our tone are being affected?

Rgs, JLH

05-26-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,644
Joined on 05-28-2004

Post #: 4
Post ID: 2448
Reply to: 2439
Throat transitioning spacer illustrations....

Posted on behave  jessie.dazzle as his Mac has problems to upload the images, The images and text are his:
'************************************ end ******************************

Here are some illustrations of a proposal using a removable transitioning spacer (fist shown without the spacer):

This will allow experimentation with a veriety of transition profiles.
Jd.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-26-2006 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 5
Post ID: 2449
Reply to: 2439
Re: Transition : Driver to throat, when throat is smaller than driver
Thanks Romy and JLH for your input :::: It seems very likely that in this application (100 - 1000Hz), the return on my investment may be small to nonexistant, and that I may be wasting my time in trying to create a smoother transition :::: Looking at my computer models, intuitively it would seem that unless the taper of the transition spacer were a lot more gradual (meaning a much deeper spacer when measured along the horn axis), it may not have much "smoothing" effect at all :::: However, I remain disturbed by the following (silly ?) visual analogies :::: Imagine trying to coax a soap bubble through a funnel having a sharply-stepped passage... Another image : Fitting an intake manifold to the port on a cylinder head, where the diameter of the manifold is greater than the diameter of the port ; in this case, at higher velocities, the stepped edge creates turbulence, further reducing the opening, and if fuel is introduced up stream of this junction, the result will be a puddle (until the manifold heats up, possibly going "boom") :::: I think I will just have to physically try the experiment... Because I cannot actually see the waves passing through the horn, I realize that there is no chance of completely understanding the cause of any difference I may hear. It should be enough to answer in simple binary fashion : i.e. : "ahh, better", or "whoa, worse" :::: Any additional thoughts would be very appreciated :::: jd :::: PS, Thank you Romy for uploading the images : I've tried it now with both the Safari and Explorer browsers (Mac OS X v.10.4.6)... There is simply no "yellow icon in the tool bar" as stated in the instructions for photo uploading...



How to short-circuit evolution: Enshrine mediocrity.
05-27-2006 Post does not mapped to Knowledge Tree
JLH
Indianapolis, IN U.S.A.
Posts 42
Joined on 07-20-2004

Post #: 6
Post ID: 2450
Reply to: 2449
Re: Transition : Driver to throat, when throat is smaller than driver

Remember that at the cone the wave front is not spherical, it is a flat plane. It only becomes spherical after transversing down the horn. This happens because the distance along the sides of the horn is longer than straight through the center axis of the horn. Of course I am talking about a round horn and not a square horn here.

Rgs, JLH

05-27-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,644
Joined on 05-28-2004

Post #: 7
Post ID: 2451
Reply to: 2449
Upper bass horns: throats or the basics?

Jessie,

Perhaps if you search something in the throat jungle you might fish some interesting results. You see, optimizing the driver to throat transition you might get some HF out of upper bass driver. But besides getting more HF there is something else in there. Let me to explain.

Pretend that you have a perfect upperbass driver with very light cone, no excursion and with an ability to do OK higher frequencies. Then still to get HF out of that upper bass horn might be complicated. The upperbass horn has LF equalization that from my perspective screw up transient response at HF no mater what we do. I am not talking about the fool what make bent horns. Even in context of a straight spherical horn that for instance does 100Hz and the driver could be pushed up to 4000Hz the sound at 4000Hz is not necessary good. The horn is just too deep for highest frequencies: the radiation pattern suffers and the transients of the HF suffer… not to mention that the 100Hz horn would be with dumped diaphragm that is optimized for lower knee. I feel that for better result at higher knee other horns would be more suitable.  So, it is not about getting out of the upperbass horn more HF but rather to see HOW GOOD those HF would be. Most of the upper bass horns do not do HF well.

Perhaps a solution might be found in the optimization of a driver to throat transition. I personally do not think so as the premises that   “the upperbass horn is too deep for given HF”, the basis horn geometry will not be changed even if you make the very good throat transition. Perhaps a solution might be found in use of compression drivers for upper bass horns.  There is only one know to me driver that would be suitable for the task: ALE P1260, the one that Johan Dreyer used in his “Fundamentals Channel”. Another solution might be truing to inject into upperbass channel another overlapping channel with correct (or excessive) transition characteristics at higher frequencies. It is what I will be trying to do and I do not know yet if it will be working…

Anyhow, prior to any experiment with driver to throat transition we need to clearly identify what we are looking for. It is not about out intellectual satisfaction that one solution would be more “kosher” then other. We need to hear a specific horn. Then to identify what it dissatisfy us if any and then, ONLY THEN try to address this specific problem of sound. If it will be addressable by the driver to throat transition then it would be it….

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
09-22-2006 Post does not mapped to Knowledge Tree
angeloitacare-idiot
Aracaju (SE) Brazil
Posts 51
Joined on 09-15-2006

Post #: 8
Post ID: 2877
Reply to: 2439
Driver to throat, when throat is smaller than driver
hi jd*

this homepage will give u more informations abought hornmouth and phaseplug.

http://www.users.bigpond.net.au/ggoodacre/centauri/diy/plugs.html

angelo

09-22-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,644
Joined on 05-28-2004

Post #: 9
Post ID: 2878
Reply to: 2877
Unless you beelive in the urban myth of a full-range driver
Angelo, I do not think this site add anything applied to the subject. I personally do not feel that upper bass horns require any phase plugs; quite in contrary they are dreadful for upper bass horns. When a straight horn employed then the horn does not loose the driver’s HF in cavities and the resonant chambers of a typical bend horn. As the result most of the straight upperbass horn has excessive HF and I relay do not see needs to expend the HF via the phase plugs. Sure, unless a person would like to make a commercial version, Stereophile advertised “upperbass horn that runs up to 20 kHz”. I would personally even consider making a front chamber for the upperbass horn in order to kill in the some HF (front chamber is a first order low pass filter). So, by construction an elaborate phase plug for upperbass horn be careful what you are asking – you might get completely unnecessary HF. Do not forget that if a cone of the upperbass bass driver is light and soft enoght to be capable to produces well the 4-5Khz region then… it was a wrong driver selection for 80hz region…

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
09-24-2006 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 10
Post ID: 2883
Reply to: 2877
Re: Phase Plugs and Upper Bass
Hello Angelo,

Even though it may not be a good idea to use a phase plug in a straight Upper Bass horn, I did find the information educational, and just wanted to thank you for the link. Thanks also to Romy for his comments on the subject.

The design of the Upper Bass horn may incorporate provisions for a removable ring-type spacer allowing instant creation of a front chamber (this simply moves the driver deeper into the horn, requiring that the tail of the horn be longer... It also means I would have to block out the additional length in the rear chamber when not using the spacer). The only reason not to do it is the fact that in my case, when not using the spacer, it would further degrade driver alignment relative to the Bass Horn (45Hz). This is due to the walls I have to work with.

Best of luck with your Orpheans,

jd*


How to short-circuit evolution: Enshrine mediocrity.
09-24-2006 Post does not mapped to Knowledge Tree
angeloitacare-idiot
Aracaju (SE) Brazil
Posts 51
Joined on 09-15-2006

Post #: 11
Post ID: 2884
Reply to: 2883
Re: Phase Plugs and Upper Bass
hi Jd*

probably u know the site of volvotreter, with quit a nice description how to built a wood tractrix horn.

http://www.volvotreter.de/roundhorns.htm

i want to built a tractrix horn with 95cm diameter hornmouth. Have u made such a horn already ? how was your experience ? what was the most difficult part ?

regards Angelo
09-26-2006 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 12
Post ID: 2890
Reply to: 2884
Horn Construction
Angelo,

We should probably start a new thread to discuss horn construction in general, as this thread is about a specific aspect of that subject (driver to horn transition).

To answer your question very quickly... As previously mentioned, I will be documenting the construction of the horns as I make them... and will be happy to pass along whatever information you may find useful.

I have made one midrange horn so far (approximately 30cm diameter at the mouth)... the project required one weekend, working full time, not counting the time to make the threaded plates, which were done before starting on the horn body. I expect the second one will go quicker.

By far, the most difficult aspect has been making time for the project.

toot toot,

jd*


How to short-circuit evolution: Enshrine mediocrity.
Page 1 of 1 (12 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  Problems with horns: upper bass ..  Must it be about loading?...  Horn-Loaded Speakers Forum     109  925979  03-25-2005
  »  New  Phase plug for midbass..  Ulf plug...  Horn-Loaded Speakers Forum     23  260341  11-08-2006
  »  New  The Macondo’s Upper Bass Channel: what is next?..  Görlich again...  Horn-Loaded Speakers Forum     30  214733  10-28-2007
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