| Search | Login/Register
   Home » Horn-Loaded Speakers» The bogusness of the coaxial compression drivers? (7 posts, 1 page)
  Print Thread | 1st Post |  
Page 1 of 1 (7 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  Orphean horns of bd design..  Re: They are easy and accessible ... still give to them...  Horn-Loaded Speakers Forum     6  95358  09-15-2006
  »  New  Orphean horns / BMS drivers..  the magico ultimo are not the best i heard...  Horn-Loaded Speakers Forum     2  28166  11-17-2006
  »  New  Swing hornspeaker of bd-design..  intern of the swing ...  Horn-Loaded Speakers Forum     2  29507  12-10-2006
03-28-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,540
Joined on 05-28-2004

Post #: 1
Post ID: 4087
Reply to: 4087
The bogusness of the coaxial compression drivers?

I have written in past about my lack of love to the BMS drivers. The crazy, as far as I concerned “annoyingly wiling” angeloitacare brought this subject to this forum while he was galloping across Web, “picking from graves” about his new dB-Design’s Orphean horns. The Orphean horns use the coaxial drivers and it made me to pay attantion to them again.

I am not wiling to knock the dB-Design products. The dB-Design do whatever they do in the context of what they can, what they understand and in what they can sell to their mostly primitive and “lightly informed” customers. The dB-Design uses in their Orphean horns the coaxial BMS 4592ND driver. They claim that they highly modify the driver (whatever it means). I do not know the externs of the modification but I’m sure that wherever they do they keep the coaxial concept unchanged. I will leave alone other negative qualities of BMS and dB-Design and I would like to expend a little the coaxial concept itself.

Many companies in past made the coaxial drivers. Nowadays the car audio campmates love the coaxials drivers because the understandable space reasons. However, do the coaxial drivers in fact offer any SONIC ADVANTAGES in context of our larger space – the listening rooms? Obviously we are not talking about the specific BMS drivers anymore. The BMS was made for very different then Sound objective. If you see that BMS is very proud that their 112dB sensitively drivers can handles 1500W of power then you know in whish ass those drivers should be stuck up. Lets turn our attention form the elevator transducers – BMS to an enter family of the coaxial compression drivers.

Any company that sells coaxial drivers loves to tall story about point source sound. Sure it is the case but why it IS NECESSARY BETTER? In fact I feel that it worse as the unified acoustical centre does not allow learning that the crossover between the drivers does not work properly. However, the biggest problems I see when people try to merge the ides of coaxial drivers with horns.

It is known to anyone what dealt with horns the each frequency range there is an optimum size of horn. Make deeper horns and you loose response and transient at HF and pick some HF beaming. Make too shallow you have not enough LF equalization and your driver acts as a direct radiator. So, a small compression transducer with 2” throat will obviously run a horn profile for let say -500Hz…. and this profile is WAY too deep for any HF that might be radiated from THE SAME THROAT. Is it absolutely FUNDAMENTALLY IMPOSSIBLE to use coaxial compression drivers (with front horn) of am I missing anything?

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
03-28-2007 Post does not mapped to Knowledge Tree
Michaelz
Posts 38
Joined on 03-01-2007

Post #: 2
Post ID: 4088
Reply to: 4087
Horn for part of FR
Some drivers have a rising db curve from low to high frequencies.  The horn may help with flattening the FR.  If the FR of a given coaxial compression driver is flat, I would agree with your conclusion.
03-28-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,540
Joined on 05-28-2004

Post #: 3
Post ID: 4089
Reply to: 4088
Juts the applied theories about the coaxial compression drivers

 Michaelz wrote:
Some drivers have a rising db curve from low to high frequencies.  The horn may help with flattening the FR.  If the FR of a given coaxial compression driver is flat, I would agree with your conclusion.
Michaelz,

all cabperson drivers have rising db curve from low to high frequencies. The entire concept of compression driver (that is misleading name) is not that a diaphragm is loaded into a front chamber (actually in most case it is back chamber) but that the driver must use horn for external equalization. It is worthless to talks about frequency response of a compression driver without a horn and any rising of decaling db curve from low to high frequencies is juts improper selection of horn EQ for a given driver (or a defect of the gioven driver itself, which BTW is very common)

So, let see what the “bad” people do in the coaxial drivers. The LF part of the coaxial is presumably properly loaded but not the HF. In the BMS driver the HF kicks-in at 7KHz and for 7KHz the 300Hz horn is irrelevant- it is like the horn does not exist. So, the LF part of the coax is loaded but the HF part is shooting though with being loaded (or loaded with own small horn). However the 2” throat of the LF horn is VERY small opening and… this hole (though wish the HF driver shoots) is located… at the front of the mouth of the HF horn – this is VERY bad.

From my photography life I know that diffraction is a process of nonlinear bending of the source waves to the area of geometrical shadow. Interesting the diffraction become to be noticeable when the diameter of the hole is co-measurable with the length of the waves … It is exactly what should be doing on in the coaxial compression drivers.

Sure, it is juts the theories but a do not see any rational for myself to not subscribe those theories…


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-28-2007 Post does not mapped to Knowledge Tree
Michaelz
Posts 38
Joined on 03-01-2007

Post #: 4
Post ID: 4090
Reply to: 4089
A graph
I am not sure if this is the driver you are talking about.  It seems that the external horn could just help with the drop from 700 Hz to lower frequencies.
http://www.bmspro.info/photos/bmspro_info/bms-4592nd.pdf

I can see why it is bad with 7K Hz from theLF part of the co-axial driver coming out from an impeded 2" opening.
03-28-2007 Post does not mapped to Knowledge Tree
Michaelz
Posts 38
Joined on 03-01-2007

Post #: 5
Post ID: 4091
Reply to: 4090
My bad
I take that back.  The graph shows the FR with the horn already in place.
03-28-2007 Post does not mapped to Knowledge Tree
Michaelz
Posts 38
Joined on 03-01-2007

Post #: 6
Post ID: 4092
Reply to: 4091
Crossover point
the croosover point of LF and HF looks located at about 6 KH where the wave length is a little more than 2".  Then the impeded opening of the LF driver should be less of a problem theoretically.
03-28-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,540
Joined on 05-28-2004

Post #: 7
Post ID: 4093
Reply to: 4090
It’s not surprise that the BMS drivers sounded like mBS….
Yes, it’s the drivers that inspired me to write up this thread. The response looks like it rises slightly atop but it is almost OK for this type of the drivers. Running the driver off the axis it is possible to roll off the HF rise. It is pretty much whatever the BMS said in their PDF file I find controversial or bogus. BTW, the BMS is the only company among all that is produce compression divers … who is …proud for having high excursion of the diaphragms… This is actually is very funny.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
Page 1 of 1 (7 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  Orphean horns of bd design..  Re: They are easy and accessible ... still give to them...  Horn-Loaded Speakers Forum     6  95358  09-15-2006
  »  New  Orphean horns / BMS drivers..  the magico ultimo are not the best i heard...  Horn-Loaded Speakers Forum     2  28166  11-17-2006
  »  New  Swing hornspeaker of bd-design..  intern of the swing ...  Horn-Loaded Speakers Forum     2  29507  12-10-2006
Home Page  |  Last 24Hours  | Search  |  SiteMap  | Questions or Problems | Copyright Note
The content of all messages within the Forums Copyright © by authors of the posts