DUAL-208 with Fostex FE208e∑ + T90A

While listening to the test cabinets of the Alnico CA-80's, I was simultaneously building the DUAL-208's.
Once they were finished I was very disappointed with the lower frequencies.
But in general very nice speakers for my 2nd set.
 

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Some pictures

Some pictures during fabrication.
 

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End results

Some pictures of the end results.
 

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Several driver tried.

As you can see I have tried different drivers in these cabinets.
The 206, 208 and the 225.
The 208 sounds the best, but also not happy with the lows.
All three drivers are very beautiful drivers.

The 225 looks the best with these cabinets (personally), but unfortunately they sound the worst.
 

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Sorry to hear that. The horn appears to be derived from the old Fostex BK series, which to be honest weren't all that great. Main issue is the usual excessive compromising of the expansion path for the QW tuning, so you usually end up with a peak in the upper bass and curtailed gain below that, with a rather uneven response up to the horn's upper corner frequency. With the higher Q 225wk that's likely to be exacerbated -the 225 can be used in a back horn, but isn't likely to be ideal for that design. Beautiful build & work though.
 
Look up "Schmacks horn" here you have something that works like a horn, those you built really are transmission line quarter wave resonators with a positive flare. They will work as horn perhaps above 100 Hz or so. Smaller than a Schmacks horn and it is more of a pipe than a horn. They still can make sound compromises and end up sounding well, but it si not easy.
 
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frugal-phile™
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Once they were finished I was very disappointed with the lower frequencies.

Not the best horn for these. The small front firing mouth will limit horn loading below a fairly high frequency and below that the horn will be a poor TL — with all except the FF225 — not suited to a TL.

Nice looking build thou.

dave
 
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Baffle step ?

I use a lot of bass boost.

I'd cover the tweeter semi horn walls with felt also.
Fill the cab with acouta fill ?

Maybe too much 150-600hz coming out of the horn mouth....... (delayed by 10ms) ?

I normally playing "pure direct" without boosting bass.
But at the moment I boosting bass, but still not satisfied.
The cabinets I fabricated are from Humble Hifi (Solo 206).
It's an existing design.
In his report he also confirmed the sub bass is missing.
Maybe damping the line will help a little to reduce the higher frequencies as you advised.
Thx!
 
Totally different, Ron was using some of the most advanced 3d modelling available at the time to create his Dallas and Austin designs. Ultimately there is only so much you can do with a relatively compact box, but Dallas II is still probably the best example of this sub-type for the Fostex units.

Yes, they are much more complex than a simple sealed or vented box, so there are a large number of factors that have a significant impact upon design.