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In the Forum: Horn-Loaded Speakers
In the Thread: JBL 2226 2445 2405 3-way and a path forward
Post Subject: The drivers’ zone of comfort.Posted by Romy the Cat on: 1/24/2014
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Pierre, yes, I understand it. It kind or irrelevant what they destined for and yes, in domestic applications in context of low power we can use it lower. What I am saying is that as we do use it at extreme low range we deal with slightly overdamped diaphragms.
Just think about it. The excessive pressure of that is generated by the driver diaphragm excursion needs to be dissipate somewhere. The diaphragm is 1-2MM from the phase plug and as diaphragm does let say 100Hz then there is very minor acoustic feedback from the phase plug. As the diaphragm does 200Hz then there is much stronger acoustic feedback over that 1MM from phase plug and the super light diaphragm does experience some reactance from it that in my view manifest itself in dynamic compression. I do not know if it happens in your case and I am talking about not about your case but rather about generic concept.
I personally feel that it is a good idea to use drivers in the zone of comfort where they are not stressed. The best bet for me is to consider if the driver can handle lower crossover then it meant to handle. For instance you use 3rd order can the same driver use 2nd order. If not then it might be that the driver is overstressed at the bottom. It might be not the case but it uselessly is.
It is a bit tricky to assess if the driver is stressed as the bottom. You might take a good played quartet but preferable not contemporary recording but something from 50s. Pay attraction how viola and cello grow affected by the octaves. Disconnect other channels and listen only your 2482 channel. As the tone goes down sound shall not loos structure and shape, shall not become fizzy or hollow, shall not change speed unless it untended, shall not obtain or loos testerone, shall decay evenly. I can give you other dozen examples of what it shall and shall not do, but it is not the point. The point is that somewhere down does Sound WILL lose ground. You need to add you’re complementary uppperbass channel, whatever you have and then to repeat your observations. The most important point in here is to have absolutely no event of any kind during sound transition between 2482 channel and uppperbass. You shall not have it even during “sit-down test”.
Using different drivers that I was trying to stress at lower knee I always concluded that my uppperbass was more vivid them the lower knee of my MF. As I rising up the crossover point for 50-100Hz up on my lower MF (that I call Fundamentals channel) and rising up the crossover point at my uppperbass I felt that I have more smooth transition with less “events”.
The 2482 might be different, I do not know. Generally I find that dropping compression in the driver was helpful a bit. I was very slightly open the back chamber of the driver that gave to me some ease at lower knee.
It is also important to differentiate when a driver is choking with wham the horn is choking by driver. In case or Macondo I was rather restricted by horn size then driver but I have chosen to keep this way as I have an expendable uppperbass that does fine upper knee.
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