New build based on an old design

[Garyf52]

My 40 year old speakers have been retired. One tweeter died and the mid ranges, which I re foamed 3 years ago, were just not sounding very good compared to the various speakers I’ve built over the last few years. However the woofers are still in excellent shape and are just too good to lay around unused. So they became the basis for my current project.

The woofers are 10” Seas 25-ewx. This is the same woofer that is used in the old Dynaco A40XL speakers from the 70’s, a 2-way. That speaker uses a very simple crossover on the tweeter and the woofer runs full range. This project is a takeoff on that design. The cabinet dimensions are the same, as the A40XL, but I’m using a Morel Cat 298 tweeter. This will be the first time I’ll be making a crossover myself.

For starters, I’ve tried several variations of simple 1st and 2nd order circuits using the small selection of components that I have on hand. I’m quite happy with the sound using a simple 8.2 uf cap and a 2 ohm resistor in series, on the tweeter.

It’s been very educational swapping components of different values and hearing the results. I have no equipment, nor technical skills for taking measurements, analyzing audio data, or designing sound systems. But hearing the effects of circuit changes makes the graphs and technical data that are widely referenced on this forum, a little less abstract for me. Also increases my respect for those who share their skills here.

The other thing I’ve been experimenting with is the cabinet damping. This is a sealed speaker with 2 chamber aperiodic damping. I’m still trying different configurations and am finding the differences to be quite subtle so far.

I'm in no hurry to finish these as I'm enjoying the experimentation process.

Some photos to show how they are looking at this point.

My testing setup. They are a bit larger than the Modula MT's that I’m using as a reference.



Very simply crossover sound quite good to me.


Experimenting with damping configurations. The batting is just taped in for testing purposes.


As always, comments and suggestions are appreciated.

[chrisn]

Looks good! Glad you aren't letting those woofers sit unused Will these have grilles?

[Garyf52]

Looks good! Glad you aren't letting those woofers sit unused Will these have grilles?

I'm planning on making grills for these. Haven't decided on the finish yet but I've ordered grill cloth in gray.

[Garyf52]

Finally finished these.

Well patience and persistence finally paid off. My speakers are up and running and I'm pleased with how they sound. The rather simple crossover was achieved purely by trial and error. I do not recommend this approach.
Here is what I came up with:




The inductor was recycled from my old 3 ways. I'm guessing that it's about 0.55mh based on the size, but I have no way of measuring it. I tried multiple combinations of components that I had on hand and it's just good luck that this one fits the bill very well.

Don't know how they compare to the original Dynaco A40xl, but I've been listening to them extensively and they compare well to my other speakers.

One thing that they do especially well is play LOUD. They seem to be very sensitive and they sound great at much higher volume than my other speakers can go. Also my amps run a few degrees cooler with these speakers. The bass does not go as low as my other speakers, but it has a satisfying full sound to it that my smaller woofers don't quite produce.

I scrapped the idea of making grills. The recessed baffle sounded terrible so I made it flush and rounded the edges. This made a huge difference.

The rather unremarkable looks was intentional. These woofers are 40 years old, so I decided against anything fancy. The finish is just a couple of coats of primer applied with a roller, then painted with oil base enamel in a plain tan color, applied with a HVLP sprayer.

[Juhazi]

I think that you should cut big holes in the divider plate!
Tweeter has closed back, it doesn't need any kind of chamber and doesn't care of back waves.
The woofer looks like a 10" unit with paper cone, and they usually like LARGE cabinets...
Because the woofer is sealed and doesn' have any kind of baffle step compensation, place the speakers tightly against wall or preferably in the bookshelf!

[Garyf52]

I appreciate your suggestions. I decided to go with the original cabinet specs and try my hand at developing a simple crossover. Didn't want to vary too many different aspects at once. No doubt many improvements could be made to this speaker, but until I can approach this in a much more scientific manner, they will remain as is. Luckily they are decent enough to use when I'm in the mood to really crank up the volume. Also, I already have a house full of well designed, great sounding speakers, so these are surplus.

Perhaps in the future I can partner with somebody who is skilled in speaker design. These drivers are probably worth the effort but my skill set is more along the lines of woodworking and cabinet building.

[Dave Bullet]

This is a DIY success.

You repurposed something, for little money and complexity and have a speaker that plays well with good sensitivity.

I think they look great too. Well done!

[TEK]

Cool!
Sounds like a fun project.

Just curious - do you have the ts-parameters fot the drivers?

[Garyf52]

Dave, Thanks for the encouraging thoughts.

Tek, There are links to the factory data sheets in the text of the first post of this thread. Morel doesn't include all the data.

Here is a puzzle that I'd welcome some input on. The original Dynaco's used a crossover point of 1500Hz.
I would think that my version is crossed much higher. I did extensive A/B testing with these against my other speakers; Modula MT, Tributes, Seas CA18RLY. I expected to detect a noticable gap in the response, but this was not evident to my ears. Any theories? (of course it could be my ears..)

Here is some info on the original Dynaco's:
Dynaco-A-40-XL-Service-Manual.pdf

[TEK]

It seems to me that the 10» is able to go up to 2000hz, so I guess that it should be possible to cross it above 1500. Probably not the bedt crossover design for these drivers?

[Juhazi]

Data sheet of SEAS 25F woofer http://www.seas.no/images/stories/vi...08_25f-ewx.pdf
and Morel tweeter https://www.morelhifi.com/wp-content.../11/CAT298.pdf

So this is clone of Dynaco A40 XL which is sealed instead of the aperiodic A25.. My first hifi-speakers in early 70's were a kit Philips AD2525, sealed 3-way in 25 liter cabs, 8" bass. Second was bigger 85 liter kit 3-way with SEAS 10" paper cone. Bot had naturally much more "developed" crossovers than those Dynacos.

[wkhanna]

This is a DIY success.

You repurposed something, for little money and complexity and have a speaker that plays well with good sensitivity.

I think they look great too. Well done!

this!!!!!:T