Elliptical drivers in back loaded horns

[hughthewineguy]

I bought a couple of single ended valve amps a while ago, which came with some high efficiency speakers, mounted in some terribly boomy 60s/70s cabinets.
Having spent a little time looking at options, I'm quite keen on building some Frugel Horn Mk3s to rehouse them, and I'm wondering if there are any considerations if using drivers with elliptical cones.

The pair I have are vintage Rolas, which are marked 'LX' on the back of the magnet, and '27H5' on the chassis. Kinda hard finding information on these online, and apart from a scanned copy of an old Rola catalogue, I've found basically nothing, not even any pics/images of what I have. The closest thing in the catalogue is what is referred to as a '6-9H' although what I have is different, having a 5x7" cone (presuming that's what's meant by the numbers in their catalogue)
They have whizzers, sorry no pic of the fronts of the drivers, I took some a while ago, but I can't find where I stored the images, and I can't be bothered taking them out again simply to add that to the post.
I'm guessing what would make most sense is to mount them vertically in the cabinets, but I'm open to suggestions...



Thanks in advance for any input!

 

[chris661]

You'll need the Thiele-Small parameters to figure out what sort of cabinet they'll go into. Frugel-Horn XL would be worth consideration - I don't think they'll fit into a normal FH3.

Chris

 

[hughthewineguy]

You'll need the Thiele-Small parameters to figure out what sort of cabinet they'll go into.

Chris

Thanks, have just done a little reading on this, it may be something a friend can do for me, he builds and tests all sorts of gear.

Am I going to end up needing to go the custom cabinet route? Or are there generally cabinets that suit a certain range of values?

 

[chris661]

I think you're gonna have to see how the T/S come back. I'm expecting a Qts >1, which is really only suitable for open baffle or leaky enclosures.

Chris

 

[waxx]

Too measure speakers, there is a good tool that is relative cheap: The Dayton DATS V2. I have it and it's certainly worth it's mony to measure out old parts (speakers, but also inductors, caps and resistors). I would buy this or find someone who own it in your region, and measure them. Also because t/s parameters may change over the years due to aging/degeneration of the drivers. I own some old Philips and Seas speakers, and their T/S parameters are a bit of the official specs from way back, altough they still sound very good and are perfectly usable once you got the right specs.

 

[Mattes]

Hi,


the DATS was easily one of my best investments in audio measurement tools and I consider it a MUST for everyone working with (old) speakers, resistors, inductors and capacitors. It removes a lot of guesswork and trust in manufacturers data...


All the best


Mattes

 

[xrk971]

I have DATS too and agree it’s essential. There is a cheap DIY way to do it with REW and a computer. Just need wires and a resistor plus some alligator leads.

 

[planet10]

Without the T/S we would just be guessing, but based on the driver size, Fs, and expected Q, it might be best in Joan — email me — or maybe FHXL.

The FH family has been very versatile in terms of commpatiblity of a range of drivers using line damping and room placement to tune the box to your taste.

I would not be surprised if these have a very good midrange and most likely a large FH would require reduction of the amount of bass/midbass produced (ie add more damping).

dave