A true constant directivity speaker does not change its directivity. That is all about CD.
But that says zero about dispersion width. An omni is constant directivtiy as well even if you disagree with this fact
A dipole or cardioid are CD as well in theory at least. And both would exhibit wider dispersion than 1" in a 15" WG.
For such EQ one needs to look at dispersion width and its interaction with the room.
I think that its a fair comment.
6.283:
Yes omni, dipole, cardiod are all CD with varying directivities. I think that the term you are looking for is Directivity Index (DI) which defines the differences. A flat DI means CD and the level at which it is flat determines how directional it is. An Omni is CD at 0 dB, a dipole is CD at 3 dB, cardiods are something like 4-5 dB and my waveguides are typically in the area of 7-9 dB. But all can be CD ( Omni, dipole, cardiod are all very difficult to maintain over a wide bandwidth.)
Now it appears that you comment implies that the amount of HF droop should depend on the DI, not just on if the system is CD. I am not saying that this is right or wrong, I just don't know if it is true or not. I know of no data to say either way. On what logic would you make such a claim (if in fact that is what you are saying).
6.283:
Yes omni, dipole, cardiod are all CD with varying directivities. I think that the term you are looking for is Directivity Index (DI) which defines the differences. A flat DI means CD and the level at which it is flat determines how directional it is. An Omni is CD at 0 dB, a dipole is CD at 3 dB, cardiods are something like 4-5 dB and my waveguides are typically in the area of 7-9 dB. But all can be CD ( Omni, dipole, cardiod are all very difficult to maintain over a wide bandwidth.)
Now it appears that you comment implies that the amount of HF droop should depend on the DI, not just on if the system is CD. I am not saying that this is right or wrong, I just don't know if it is true or not. I know of no data to say either way. On what logic would you make such a claim (if in fact that is what you are saying).
Have you found the drivers allready or have you not decided yet. I'm looking for a similar project and have my eyes on the Celestion TF1530 bass driver that was mentioned in the Ariel thread and a cheap polish 2 inch CD for the horn (IWATA or LMLC) Perhaps we could team up.
The OP has stated he is using a 1" Compression driver on a SEOS-15 waveguide and a B&C 15TBX100 woofer.
I'm talking about the later. Don't ask me for a "why?" Explanation though. I have no idea why. It seems to conflict with my intuition.
I think that the later case is very clear. In a CD speaker there is a lot of energy going out from the tweeter at high frequencies and this energy gets back to the listener via the reverberant field. Our sense of tonal balance depends on both the direct field and the reverberant field. In the direct radiator case the HF are in a narrow beam and as such there is not HF in the reverberant field only the direct field. So it takes more direct field - axial response - to yield the same perception of the HF energy.
Basically even though the direct field of the CD speaker is lower than that of the direct radiator, the total energy at HFs is greater.
The question that was raised earlier had to do with the amount of indirect energy and its influence on the amount of direct field energy needed for proper perception. It seems that as the DI gets higher less of a falloff should be required, but that does not seem to be the case. I am not sure what the answer to this second issue is.
Basically even though the direct field of the CD speaker is lower than that of the direct radiator, the total energy at HFs is greater.
The question that was raised earlier had to do with the amount of indirect energy and its influence on the amount of direct field energy needed for proper perception. It seems that as the DI gets higher less of a falloff should be required, but that does not seem to be the case. I am not sure what the answer to this second issue is.
Ok thx I missed the woofer, it does however seem to have a problematic peak at 1000Hz.
And there's quite a difference between having bought the drivers or contemplating them, I was trying to clarify whether Magnus did one or the other.
I got a sweet deal on a pair so they should arrive in a week or so.
Great have fun!
But that typically doesn't kick in until>5kHz...give or take. Maybe that's enough to do it? I would think that the 2-5k would be more important as far as specral balance perception is concerned. I actually haven't seen many broad dispersion designs maintain their dispersion much above 5kHz. Narrower designs in general seem to stay closer to constant. Toole's book seems to be keen on the direct response giving you the tonal balance above 300Hz. He does mention something in there about reflections filling in spectral gaps.
Anyway, just my observations down with complete disregard for science though I respect it.
Yep.
The comment is based on my own pratical work (documented on my web page) and observations with "foreign" speakers.
I have build a speaker that is true omni horizontally. That required a lot of roll-off. Then I changed the speaker to incorporate a tweeter that starts beaming at around 2.5KHz. It required at lot less roll off but comparable to my dipole.
I have heard speakers that use bigger FR units (e.g. 5"). They even required a rising FR in order to sound about right. However, the highs became hot/heavy because the DI was rising fast above 1.5...2KHz, yet the tonal balance was not wrong. It was only much less airy and more compact (maybe that is what Ronion was referring to with "trebly").
In all setups the reverberant sound field was higher than the direct sound by about 3...6dB.
So the answer lies in the combined sound field at the listening place mainly influenced by the DI/sound power response of the speaker and the subsequently generated indirect sound field in a regular small room.
This is fascinating stuff, I'm learning a lot from just reading your discourse.
I can't claim to grasp it fully but it sort of sounds like the energy transmittet by the HF driver can be seen as constant but depending on the dispersion pattern the percieved HF response will change for the listener. I suppose this will be a direct effect from energy transfer and very measurable?
A somewhat trivial analogy could be a common garden hose with a adjustable nozzle.
The amount of water is constant but you can sparay it over a large area or use a focused water beam. The water beam will deliver a much more tangible "hit" on the target.
Would that be sort of the same thing?
I can't claim to grasp it fully but it sort of sounds like the energy transmittet by the HF driver can be seen as constant but depending on the dispersion pattern the percieved HF response will change for the listener. I suppose this will be a direct effect from energy transfer and very measurable?
A somewhat trivial analogy could be a common garden hose with a adjustable nozzle.
The amount of water is constant but you can sparay it over a large area or use a focused water beam. The water beam will deliver a much more tangible "hit" on the target.
Would that be sort of the same thing?
Yes and the changes are not subtle. But don't limit this to the tweeter. It applies to the entire speaker above the Schroeder Frequency (typically the low hundrets of Hz).
Yes, funny analogy
Now only put a guy, who will become wet, inside four walls and set two nozzles (one in each hand) to wide. Then spray so that the outer sprinkles first hit the side walls and from there they spray at the guy from roughly 60° on each side. Some water will run down the wall so he becomes a little less wet from the sides than from the front but when asked, he finds it pleasing.
That is pretty much what Toole says in his book and I recommend reading it. In there you will also find the exact mentioned semantics.
My other recommendation is to start thinking in radiation patterns (3D). The on-axis FR only says very little when looked at in isolation.
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