I posted and also linked measurements from jbl pro:
Dr. Geddes, thanks for the reply. yup, the summa line is on the top of my wishlist right now. I have to ask though cause I come from the Philippines, how much would they cost shipped the nathan's for example. And whether I can save on the kit or fully built. We have very good woodworkers here. I am just worried about the crossover if i'll get them right. Additionally, what does built and tested mean? Do you measure all fully built speakers before you send them?
I also have other questions, hope that its not too much.
Quote:
I don't really think that all those speakers that you mentioned really do have comparable measured performance. Within what they show they might, but its what they don;t show that is the key. One needs good high resolution off axis data that always seems to be sadly lacking.
I do not know if these measurements suffice. They have on axis, listening window, 1st relection, directivity index sound power, directivity index 1st reflection, impulse response, etc. Are the measurements lacking to be able to know whether they sound good or not? Or are the shown measurements themselves bad?
Quoting from jbl "We all know that many loudspeakers have similar measurements but sound different. By going beyond simple on-axis frequency response measurements, JBL defines the ultimate performance specification for new systems – what it will sound like in your room. At the mix position, you hear a combination of direct sound and sound reflected from the rooms surfaces. For sound arriving at the mix position to be smooth and neutral, it is not enough for a speaker to measure “flat” on-axis - it is essential the speaker have excellent off-axisperformance. While other manufacturers use a single on-axis frequency response measurement taken at one point in space, JBL measures monitor systems over a sphere that encompasses all power radiated into the listening room – in every direction. This data reflects 1296 times the information of a single on-axis response curve. Seventy-two measurements of the direct sound field, the reflected sound field, and the reverberant field, the entire sound field heard by the listener, is correlated to optimize response at the listening position. In place of spectral smoothing used by some manufacturers, which actually conceals data, the JBL approach actually exposes flaws in systems, such as resonances, poor dispersion and other causes of off-axis coloration. The data shown below is a set of spatially measured graphs that are the heart of JBL’s philosophy."
I think of all the other speakers i have mentioned the harman brands have the most capability of making good speakers due to their resources. My worry is that even if they have the talent and the resources, the research isn't applied to the fullest in their end product especially the ones I can afford. Nowhere have I seen the amount of technical data than from the harman brands excepting of course your summa's and linkwitz orions. And what I most like about the summa line is that people interested get to have answers directly from you. This gives people peace of mind that what they are buying fully espouse the research. Finally, your designs compared to most state of the art loudspeakers cost much much less and is certainly attainable compared to Revel Ultima's or JBL Synthesis for example.
I do have a question regarding interpreting polar maps. I do not understand how to interpret them. I have been looking at the polar maps of the summa, abbey, and nathan and I just assume that the summa is better. Is it simple to interpret? Sorry, i lack technical expertise. Dr. Geddes do you have a picture of a perfect "ideal" polar response that could be compared?
Finally, regarding room design, will you be posting the additional chapters in your home theater book at your website? I only know that low frequencies need to be treated while mid to highs need minimal but I dont know how to realize them.(construction)
Once again, thank you Dr. Geddes and i hope that I havent taken too much of your time.
Dr. Geddes answers:
Theshade
I would agree that Harman is the best of the companies out there in terms of R&D and product line. They supply the best data, but it is still lacking IMO. Theye are trying to get a valid but "simple" set of measurements. I think that they oversimplify. What they do is better than most, but I'd still p[refer to see the "real" data.
I assume that you understand polar response graphs shown on axis and at angle off axis. The data in a polar map is identical, just shown in a different way. What becomes obviuos in a polar map is the field of flat response. For example my polar maps are arranged so that they show color changes every 4 dB with the first color being +-2dB from the nominal level (0 dB). So from this you can immediatly see what frequencies and what polar angles have +- 2 dB capability. In my designs this is usually (excluding the LF limit for now) up to 30 degrees and 10 kHz. There is sometimes a small "hole" on axis which means that theya re flat from +-7.5 degrees from 70-10 kHz.
The second thing that become obviuos is the coverage angle becuaes the secodn line is the -6 dB line which is the coverage. This should be fairly constant.
Also obviuos are resonances as they show as bumps in all levels at a fixed frequency. Diffraction will show as a bump (a peak and or a dip) which changes frequency with angle in a constant arc. These take some experience to see.
Shipping the speakers to the Phillipines would cost about 33% of the total cost (based on experince, but this goes up all the time). The croosver is easy to make and would be hard to screw up, but there is always the issue of a bad componenet that is unknown when assembling it. This is easy to test for me, but difficult for the end user. Yes, I do test each speaker that I assemble. Good paint is the hardest thing to do in building the kits.
As to more chapters for my book - well that takes time that I don't seem to have these days.
