Again, I do not agree with all notion of Rubber sound that Haralanov seeded. I can not speak what was in the situation that “be” described and 400Hz crossover. I do have the 8” version of 25W driver (I think it is 21W) and my feeling that it sound along the line with 25W driver. I would say that from what I heard in the sound of 21W it has more rubbery sound then 25W. The problem is that I do not attribute or associate the character that 25W or 21W drivers have to Rubber at all. It might “feel” that it is sort of like rubber and looking at the driver it is very easy to conclude that the rubber is the guilty party. I do not feel this way.
The 25W footers are made with Styrene-Butadiene rubber wish is synthetic polymer and frequently used for many different things. SkanSpeak calls the suspension ofthe 25W woofer as "non-inertia" suspension. Sure this is just marketing things BUT when I first touched the 25W woofers I did get a feeling the it is not a regular rubber as SkanSpeak probably used much thinner rubber on those drivers, Put in this way: many other drivers the I touched did not impress me with this feeling of suspension non-not intensive softness. For a first time I touched them it was when John Dunlavy upgraded his SC-IV model in end of 90s to the SC-IVA replacing whatever woofer the model SC-IV had with the 25W. It was very good move for those speakers and I did noted that SC-IVA had much more interesting bass then SC-V or even the SC-VI. This thin rubber suspension on the 25W driver does not feel like rubber to me when I touch it and it more feel like ailed foam or even leather. In my view it does has different feel to touch when I move the driver by hand.
Now about the allegations of the rubber sound. Well, we all understand that word “allegations” is not literal here but still let talk about it a bit more. In my assessment what you guys call rubber sound of the 25W driver (and I do know what you are talking about) is not rubber sound but the sound of the driver compression. This driver is 88dB sensitive and it behaves like any other 88dB driver. If you take let say a good 15-18” woofer then they would be 97-101dB sensitive, the 12-13dB difference in sensitivity got to be heard. OK, let see how the 25W woofer compresses sound.
In my past I had a number of powerful SS amps (BAT, Spectral, PassLab, etc) that I was experimenting to drive my woofer towers. The best SS amp that I had was Lamm M1.1. Lamm M1.1 was very interesting amp and I have seen a number of commercial ported speakers that never were famous for their bass performance and Lamm M1.1 transformed them into very different bass. So, I was trying in my past to drive my woofer towers with different SS amps. It was OK but ultimately I did not like it and I do concur that it had very sever dynamic restriction and did sound almost like rubber.
It was in 2000-2001, and I use a pair of Lamm ML2.0 to drive my speakers. One day I took one of my Lamm ML2.0 from left channel and put it to drive bass towers of my right channel, listening it in mono version. It was truly fantastic as all, absolutely all problems that I hear in the woofer towers with 4x25W driver were gone. It was so wonderful that I immediately played to Lamm for another pair of ML2.0 SETs and frankly I never looked back.
If you look further down the line of my past, the period that is well covered already in my site then at the time when I made my first 3 Channels Melquiades DSET ( at that time I called it Super Melquiades) I was not satisfied with the sound of the bass transformer I had after I added extra two woofers. The impedance of the woofers dropped from 8R to 4R and the new transformer that I has was 6.1R or something like this. I order another transformer that I think was 5.3R. I might be mistaken with the numbers but what I am not mistaken hat there was HUGE difference in the sound of my woofers between 5.3R and 6.1R transformers. You understand that we are taking about very minor change in loading that in most of the cases shall not be auditable. At that time I use 100Hz second order and the difference in sound moderated by loading was VERY substantial.
So, what I am trying to say, BTW, I do remember that I did said it before. There is something in the 25W driver that is very nice. I think that combination of that cone (I use the pimpled cones only), that soft suspension, the masses and anything else makes it very sensitive to loading. My woofers boxes are overtrumped, that makes them even more sensitive to loading. The soft “saturation” of the SET amps looks like makes the dynamic limitations of 25W drivers to sound very human and very none annoying. In the end with properly SET loaded and many drivers in line-array I truly report that I had no negative qualities you guys associated with this driver and I did liked it a lot. I do concur that it was not the perfect in absolute send but I do not associated it with rubber suspicion but with other factors: low reverberation time in the room, restricted power of my bass amp, inability to put another 16 2W driver in use and so on.
I do sincerely feel that in that in that time in that small room I had the best bass I heard in audio anywhere. It is very much not ego thing but just my testimony. From certain perspective it was in a way even bass-better then what I have now in my current listening room (not all together but from only certain restrictive perspective). Do I recognize the 25W problems? Of cause I do but I would not name the rubber suspension but rather the dynamic restrictions. If the 25W was let say 10dB sensitive then it would be much more interesting.
So, in the end of the day I feel that you guys call the dynamic restrictions of the driver as “rubber sound”. In reality with a good SET bass amp those dynamic restrictions are very pleasant and very transparent.
For sure using the larger driver with very different topology is other way to go and there is nothing wrong with it. However, the different sound of the larger woofers is not necessarily is an indication that there is something wrong with 25W woofers, particularly if the efforts were not spent to make the 25W to sound properly. If I have an option to go for 8x24” woofers or 32x25W woofers (or whatever will be an equivalent in volume displacement) and if I had no other considerations (room, location, positions, boxes… etc…) then I truly do not know what I would select. I know that if 25W woofers had extra 10dB sensitively and had extra 10-15dB of compression point then I would not doubt about my choice as I feel that there is something very nice, very organic, very pleasant and very sort of speaking human in the sound of the 25W driver. Not it is NOT the tone-wealthy driver (like some others) but it still has that “something” that makes it to be loved my me.Rgs,
Romy the Cat
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche