I don't know. (sorry, I'm not an expert.) but I read reviews on 4Pi speakers (with JBL 2226H), that bass is nonexistent in the lowerst volumes. I managed to listen to it, my experience is the same as the reviews. I think that the Summas behave similarly.
I met a repairer last year who said that bigger (heavier) cones need power.
I met a repairer last year who said that bigger (heavier) cones need power.
All is well - thanks.
To me the "parameters" of a driver or its system below 100 Hz are pretty much irrelevant. Once in a room the end result is dominated by the room and driver locations. Since this can only be "corrected" with multiple subs and EQ, I assume such. When you have multiple subs and EQ available the parameters of the individual systems is completely irrelevant. You need good power handling, the rest is placement and EQ.
For a "sealed wide band driver" above 100 Hz - something that I have never done, nor would I suggest, it seems to me that a "Q" of .7 - 1.0 would be best, leaning to wards the higher limit. But this all depends on what you are doing below 100 Hz!
Summas were designed with the use of multiple subs in mind. Their bass cannot be judged otherwise as that was not the intent.
Sure if they have a heavy cone and a small magnet, i.e. LOW efficiency, but you specifically said "High Efficiency".
perempe20,
It seems to me you are mixing up terms here and concepts of hearing. Earl is correct that a high efficiency speaker will demand less power for a given spl level, that has nothing to do with just the physical diameter of a driver but the magnetic system comes into play here and the mass of the moving assembly.
But what I think you are referring to is that when we listen to music at lower sound levels the apparent bass will not be as much, that is just the way our hearing works. As you raise the sound level our hearing shifts and we become sensitive to different frequencies. Look up Fletcher-Munson hearing curves and you will see what I am talking about. This is why many older tube and solid state preamps had a loudness control, to bring up the bass at low levels to bring the sound into balance for our hearing at low levels.
It seems to me you are mixing up terms here and concepts of hearing. Earl is correct that a high efficiency speaker will demand less power for a given spl level, that has nothing to do with just the physical diameter of a driver but the magnetic system comes into play here and the mass of the moving assembly.
But what I think you are referring to is that when we listen to music at lower sound levels the apparent bass will not be as much, that is just the way our hearing works. As you raise the sound level our hearing shifts and we become sensitive to different frequencies. Look up Fletcher-Munson hearing curves and you will see what I am talking about. This is why many older tube and solid state preamps had a loudness control, to bring up the bass at low levels to bring the sound into balance for our hearing at low levels.
All of what you've said is correct, and I might add, very well presented.
Thanks,
TerryO
What needs to be "fixed"?
Horn loading is not a panacea, it has its own set of problems as well. In fact, to me, horns for increasing efficiency are a waste of space and money. They are only useful for directivity control - there, nothing else works.
The important thing IMHO is to be able to combine whatever natural high-pass you get with an eletrical EQ/filter to obtain a given acoustical target (that will complement the acoustical low-pass...).
As for electrical EQ/filter, a Linkwitz Transform will let you convert any sealed alignment into any other, so for example it might be easy to convert it into a Q=0.707 at the intended crossover frequency, and then add a second electrical Q=0.707 at the same frequency to obtain a acoustical Linkwitz-Riley 4th order filter.
The only thing that remains for the choice of a given acoustical sealed alignment is how much Watt you will need in the intended range after the EQ is applied (ie efficiency). This can be simulated with WinISD Pro (VA tab).
In most cases, as Earl noted, higher Q values will give a bump in the lower part of the range, and as a consequence will consume less power once EQed (ie be more efficient where it counts).
Less power is a good thing for the amp, but is even better for the voice coil of the driver (thermal modulation reduction).
Thanks Earl, that all makes sense.
Also thanks Pos, I am working on a design which only drives the full range driver above the box / driver resonance, and also only drives the subs below their box resonance.
Thanks again guys and all the best
Derek.
Problem with all of the above is that it ignores what the room is doing. A high Q driver may be at a low point in the room response thus negating any "gain" from the Q. The LP woofer and the HP mid are both modified by the room if this happens < 200 Hz or so. It is simply incorrect to make any analysis of LF systems that do not include the room and what it does to the response, and this, in general is case by case dependent. We all would like to make generalizations of what to do, but the bottom line is that you can't.
For example, in general I do not LP my subs, but certainly not at the same frequency in any case. It is all matched together to yield the best net result.
This is certainly true for the subwoofer crossover, but for a midbass crossovers and up, I think it is best to seek for a good complementarity of the acoustical filters (and phase coherency throughout the crossover). If the room affect the response and EQ must be used, then it will better be used on the input section, ie on both drivers in the same time, thus keeping the good complementarity.
The chances that the room consistently affects one driver differently than the other are quite small, and if it did then it would only be at specific positions anyway.
Of course boundary reenforcement, like having a woofer very close to the floor, and the other much higher, is something else altogether, as is having a baffle of different size for the two drivers (and a baffle step frequency around the crossover point...), or having the two drivers far apart, but those are simply bad design symptoms, and cannot be addressed using EQ anyways.
Agreed, that may be misleading. I feed the subs with the LFE channel and that in itself is LP'd. Some subs, like bandpass don't need any more LP, but others like a closed box do. Hence they are all LP'd at some point, but certainly not a common point such that there is anything that someone could point to as a Subwoofer Crossover Point. Generally there is no HP on the mains either, but sometimes a small 6 dB/oct is used for the smaller units. It ALL depends on the specific situation!
Earl,
I would be interested to hear your take on what JBL did with LSR6332? how do you think their approach compares to yours, since they also feature a 12incher at the bottom but mid and top are obviously a no-horn approach.
p.s. btw as for Lynn's design in this thread I consider it similar to yours only one size bigger (and for that matter too big for what I could practice in my home
).
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