Adrian,

It might be a fascinating but more evolved journey then you think or willing to endure.  The first thing first I think that your fear that your “midrange might have ideal frequency response” is not a motivation to change anything. Are you concern about frequency response or about the well-identified subjective complained that you have developed?

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=432

If you look all thread related to TRA then you might see that I am very skeptical about “even frequency response”. It is a big subject and do not expect that you get from a new for your RTA any objective measurement. The objective measurement is the one that 100% correlation with auditable experiences – it take some time to educate yourself how to measure, what to measure and how to interpret the measured results.  What a time being, instead of thinking about “what might be changed” I would encourage you to nail down what specific problem of your playback dissatisfies you and to think then by mean of what changes you will be addressing the given well-identified and understood problems.

Romy the Cat wrote:

The first thing first I think that your fear that your “midrange might have ideal frequency response” is not a motivation to change anything. Are you concern about frequency response or about the well-identified subjective complained that you have developed?

Adrian,

If you are still in MF frustrations then I have something that you might find interesting. Recently I pick up in UK a pair of Vitavox S3 drivers. They out to be with original metal cones. I do not need them but the price was too good to let it pass. I was considering to put it to my storage, adding them to the of my large grave yard collection (a big storage with all imaginable loudspeaker crap) but then I figure that if you wish I might let you to play with before they die in my “audio repository”. 

The speakers now in the box in my trunk (I did not open the box up as I got it from UPS) and if you wish I just dump them to post office. Be advised that it might be more pain on ass for you then you expects. The speakers are 50 year old and most likely need work. They are 1.5” and you would need to make up some kind of temporally mounting arrangement. The have cone at the different spot then you current drivers, so you will straggle with time-alignment. They are with ceramic magnets- so you might not like your current amp with those speakers, a SS SE amp in class A would be more desirable for them.  Anyhow, you might have a lot of work to do just to try it, I am not sure that it is what you would like.

Anyhow, if you are bored and would like to have some audio “excitement” then I can send them to you for a couple month…

Romy the Cat wrote:

If you are still in MF frustrations then I have something that you might find interesting. Recently I pick up in UK a pair of Vitavox S3 drivers. I figure that if you wish I might let you to play with before they die in my “audio repository.

Romy the Cat wrote:

The have cone at the different spot then you current drivers, so you will straggle with time-alignment.

Romy the Cat wrote:

They are with ceramic magnets- so you might not like your current amp with those speakers, a SS SE amp in class A would be more desirable for them.

Romy the Cat wrote:

Anyhow, if you are bored and would like to have some audio “excitement” then I can send them to you for a couple month…

drdna wrote:

Very interesting, it is certainly worth a try. Do you have the information on frequency response, impedence, etc?

drdna wrote:

In any case I think it will be educational to see the effect on the sound.

It will not be just “effect on the sound” but “affords on the driver”. I cut the lid of the shipping box in my trunk and it looked at the drivers. Without opening them I up I might assess that they are in original condition and no one vandalized them (I have seen many of them and can make very accurate assumption). The drivers have flare foe 4-bolt mounting, which is good. Each driver has one terminal broken off (constant pain on Vitavox drivers if former shippers did not screw in the binding terminals all the way down before shipping). The way how the Vitavox made the broken off binding terminals shall not destroy diaphragm, so I presume that the diaphragms are fine. Considering that it is the original S3driver that were not modified (they have a tone of spider net in the throats) I might presume that they have original S3 cones – the aluminum with plastic suspension. If it so then it will not be the contemporary “white” suspension but “clear” suspension – that was designed for high power applications…

Anyhow, if you go for it then you will need to find two metric bolds and use them as binding terminals. You would need also clear up the gaps and align the cones - I am sure they will have dead cockroaches in the gaps. I would estimate that it will take one trip to you local shop that sells bolts and one wasted evening to clean the driver and to make it operational. Frankly, this is one of the reasons why I propose you to deal with it as in the end I will have a perfectly operational driver. BTW, if someone would offer the same to me then I would refuse as what would I do if I like the driver but it is the time to send it back?

Romy the Cat wrote:

However, you need to find out how much power and how much gain you need for you subs and your room. Borrow for someone any 6C33C and measure how far the 6C33C will be from class A2 at a level of max tolerable bass in your room.

Romy the Cat wrote:

If you are taking about loading demand then it is more complicated subject. The keys in the decision to go for separate DSET for upperbass in not LF but HF. You need to know if the inductance of your upperbass returns anything into MF channel; THAT was why I separated my upperbass and MF – I have written about it as it was the issue with my Fane 8M driver.

Romy the Cat wrote:

If you have the same problem than a simple solution would be to add just one more 2A3 with own OPT and driver from the same driver and driver from it the upperbass. In your case it would be even simpler. You have two stages on two halves with 6SN7 with too much gain. You might convert your amp into two stages 6SN7-2A3 and make each halve of 6SN7 to drive own 2A3: one upper bass and another MF. All that you need to worry if your PS would care another 60mA. In this setting you might load MF 2A3 with respect of best harmonics and the upperbass 2A3 with respect of most power (if it were necessary)