Well, the game with a “better” 10" bass driver is over. After years of mind looking for the 10” light-coned, papered 20Hz drivers with higher sensitivity and after a month of quite active searching for such a driver I concluded that such a driver juts do not exists. I went over (specs) at least a dozen drivers that remotely fit the requirements and spoke with a number of driver manufacturers exploring the possibility to make a run of the custom drivers. The compromise between sensitively and some other crucial for me characteristic really did not allow to move upper at the sensitively scale even if I make my favorite 25W/8565-00 a lower impedance version it would demands the stiffer suspension in order to retain mechanical stability at high levels with the heavier voice coils and consequently the increase of the resonance frequency. I was looking at all of this and decided that without spending a really huge amount of blood and dough to resolve this issues and without going into the realm of 15” line arrays I would advance the sensitivity by adding a pair of drivers per channel. The 25W/8565-00 is 88dB and with 6 drivers I have +3dB per driver >100dB total (?). It sounds to me like OK numbers + I will still stay under thesecure umbrella of SD-1 motor, SET friendly, low excursion assembly with “smartly” overhang VC of non-excessive power handling.. In addition I know how the 25W/8565-00 sound….

I feel that I kind or lost the battle for the higher sensitivity 10" bass driver but …sometimes it is peaceful to be a looser.

Rgs
Romy The caT

cv wrote:

I make 6 drivers = 95.8 db/W. You get 3db / doubling of the number of drivers ie 88 + 10log10(6 drivers).That's why I'm going with a bunch of Lambda TD15S (which are sort of a cross between the Altecs cone - paper, curved, foam surround, and a motor not too dissimilar to the SD1 I think). But then I'm gonna try them out in dipole mode first so what the hell do I know :-)

Chirag wrote:

Outside of the already constructed bass towers, is there a reason you are looking exclusively for 10" drivers?  I have heard a pair of stacked 15" Lambda's on each side supplementing/providing bass to lower midbass under some Oris horns and it worked quite well.  15" drivers will have their own benefits and drawbacks; I am not yet in a position to identify this, but on paper, they will be able to go as high as needed, can be picked up with larger magnets and tend to have a bit more sensitivity.  Is there something you find interesting about the just 10" for bass?

Certainly there are no other reasons then to use the existing bass towers. If I had space then I would probobly go the line arrays with 15” and if they were good drivers (as hard to find good 15” as to find good 10”) then the 15” would produce superior result. It is important do not use the 12” drivers – they never ever were made good quality but the 15” are fine, the 18” even better, thanks God there was some very good 18” produced. Still there are a few “issues” for the line arrays of big drivers. With even 2 X18” of the quality that I mean you would need 20-30 cu feet… that is kind of large…. Also, all of them need a lot of power to drive them, so they certainly are no SET friendly, not to mention that practically all of them do very bad at upper bass. The 15” are very good compromise, they might be fairly SET-friendly and can handle the upperbass’ first order. The entire idea of my LF section was to make the small line arrays with minimum footprint that would perform at the level of 15” array, or prefabs better. The idea pretty much grows around the 25W/8565-00 capacities.  You might have some difficulties to find a 15” driver that would be able to perform at the 25W/8565-00 level. I know some 15” drivers that do better at upper bass but they all have air resonance at 40-50Hz. I do not know any 15” with resonance at 20Hz that sound good all around, although I did not dig very deep into the 15-inchers

BTW, thins to anyone who suggested different drivers, I have decided to do increasing the number of the 25W/8565-00 section….

Rgs,
Romy

cv wrote:

Not to start a pissing contest, but how are they wired (series/parallel?), and with what voltage across them? Something just can't be right; the makers spec is 88db / 2.83V, which is over 1W. Unless it's uniquely smooth room gain with the array configuration... c'est possible, I suppose.

Romy - Not sure if you mean increase the load above 550ohms, which would give you less power, better damping and possibly less distortion (trade off between how much you need to push the tube and the flatter loadline, also I suspect there is distortion cancellation going on in the Melquiades which is more unpredictable).

However, this would slightly increase the gain and more "overdamping" of the 6c33, certainly lower Zout...

Is this what you mean?

Something else to consider, if you are running your 4 drivers in series parallel, then connecting 3 parallel pairs in series will give you 1.5x the original load. Well, strictly speaking, it will if your OPT has plenty of primary inductance - as I recalll, 7H, which is getting marginal, but anyway, at least at 40Hz and up, the 6C33 will then see a load of 800ohms... so if you are defintely going to go to 6 drivers, this will avoid having to get the OPT rewound.

OTOH, if you are of the "series connection of woofers is bad" school, get those OPTs rewound for a 1ohm load (6 woofs in parallel).

Btw, assuming identical woofers, there is no change in damping between series and parallel connection I reckon, contrary to the BS usually spouted.

cheers