FE207e and Vofo

[Drewaudio]

Hello,

I'm new to this forum and would value you advice.

I've been thinking about building a full range speaker to match my diy triode KT88SE amp. I read a heap of posts in this forum about various speaker designs and have chosen to focus on Martin's virtual project 5 using the FE207e or, FT-1600 using FE167e or, Vofo.

My question relates to the Vofo design which uses the FE206e. What design changes are required to accommodate a FE207e? Is it simply the BSC or are dimensional changes required for the cabinet?

Kind Regards
Andrew Parsons

[Scottmoose]

You'd need to change Vb and port CSA, which Ed has tuned carefully to match the 206. Response of the 207 will slump in the bass somewhat as-is.

[vitalstates]

Hi Andrew

As mentioned previously the cab volume has been reduced for the latest version. This figure was actually by 0.8 ltrs. The first version is probably more suited to the 207 but I would guess that given the paras below you will be hard pressed to tell the difference. To make a pair of mark 1s just add 12mm depth to the cabinet. This can be easily achieved by building the bottom wave guide on 6mm ply instead of the prescribed 18mm.

Is there any reason for using the 207 in preference to the 206??

fwiw I believe Nelson Pass mentioned his preference for the 206 in his paper on matching FR units with transconductance amps, and that was good enough for me.

Regards

Ed

[Scottmoose]

207 is shielded. It'll need less correction in a mass-loaded line as it's got a higher Q. In a TQWT like the Vofo, the 206 would be the better bet IMO. Goes higher than the 207 too.

[vitalstates]

Sorry Scott, I glibly took spectrum's figures as gospel...does this mean that theres a typo on their page????

[Scottmoose]

Nah, just Fostex PR speak. They claim 20KHz for both, but even using their massively smoothed graphs, compare the efficiencies / SPLs of each at 20KHz. On-axis FE206E = 95db. FE207E = 86db. This 8 - 10 db difference at 20KHz continues off axis as well. The FR207E is only really usable to about 12 - 14KHz; despite the whizzer, it doesn't get up much higher than the FE208ESigma, which is more of a WR than an FR driver. It can probably be EQ'd ~flat though like the Sigma, but it needs some help, either with that or a supertweeter of some description.

[Drewaudio]

Interesting comments guys!

The main reason for using the 207e is that this project will be my first experience with full range speakers and I thought that the 207e would allow me to try a range of different designs using the same divers.

It seems that it will be too much work to modify the vofo for the 207e. Perhaps I should buy the 206e as that might be a driver that is capable of being used in a range of enclosures. I've read a number of comments about the 206e (rising HF etc) that caused be to consider other options.

Vitalstates: I'm not clear about the vofo mark 2 dimensions. Would you mind giving the dimensions (internal or external) again.

Kind Regards
Andrew Parsons

[OzMikeH]

Originally posted by Drewaudio
Interesting comments guys!

The main reason for using the 207e is that this project will be my first experience with full range speakers and I thought that the 207e would allow me to try a range of different designs using the same divers.

I have a pair of 207 and I am about to build my second cabinets, Generally any cabinet that will allow the 207 to really perform well will consume at at least one full 1200 x 2400 sheet of material per speaker. Really big cabinets aren't that great in MDF so you're looking at a cabinet cost about equal to the driver cost.

One thing you must do: put phase plugs in. Don't even bother breaking them in, just make sure they work then void your warranty and cut them up. They do need a good thrashing before they sound any good.

My biggest mistake: making cabinets suited to corner loading without having appropriate corners in the room.

[vitalstates]

Originally posted by Drewaudio
Interesting comments guys!


Vitalstates: I'm not clear about the vofo mark 2 dimensions. Would you mind giving the dimensions (internal or external) again.

Kind Regards
Andrew Parsons

Andrew

Are you saying that you don't understand the dimensions on the plan?

[GM]

Originally posted by Drewaudio

The main reason for using the 207e is that this project will be my first experience with full range speakers and I thought that the 207e would allow me to try a range of different designs using the same divers.

Greets!

FYI, the lower the driver's Fs, Qts and the greater its Vas, HF gain, the greater its in-room tuning flexibility with various forms of acoustic and/or electrical EQ, so between the 206/207 the 206 is the 'no-brainer' choice and if you need the shielding, scraps of cold rolled steel (CRS) sheet metal from the local tin-knocker on either side of the TV/monitor solves the problem if you can't find the proper size tin can to fit around the magnets or don't want to pay for bucking magnets if you don't have any old drivers around to scrounge magnets off of.

GM