Killer 2.5 way Design

[amperex]

I built a pair of ProAc 2.5 Response speakers about 7 years when they were all the rage at the Madisound forum.

As my tube audio system was upgraded a few times over the years, I noticed the ProAcs were not so dynamic sounding & did not sound like a live performance after listening to some other audiophile systems. The ProAc 2.5 are referred to as a forgiving speaker. In my case, too forgiving.

The new cabinets are 3/4" wall measuring 30" high x 16" wide x 14" deep ported enclosures using a Pioneer A30IR50-51F 12" woofer, a Peerless 830883 Exclusive 7" midrange & a Seas T25CF001 Excel tweeter. Rear facing pair of bass ports are 3-1/2" diameter x 10" long. The cabinets front panel are tilted back approximately 10 degrees for best time alignment.

I have read good reports of using a simple first order series crossovers. Simple crossovers do not have significant phase shifting issues like more complicated designs.

However, to limit the midrange lower response using a simple 2.5 way first order crossover, the midrange requires its own sealed enclosure to limit the low frequency response. I used 10" diameter sonic tube. Sonic tube is a cardboard tube used for concrete piers. It is available at Home Depot. I carefully cut the tube to the proper speaker cabinet depth and used epoxy glue for a super strong bond to the speaker cabinet interior. The tube interior is lined with high density 1" foam to limit reflections & reduce the interior volume. The volume was reduced to only .35 cubic feet. The tweeter is crossed over at approximately 2kHz. Although the design calls for a 10uF series cap, I used 8.2uF to better balance to response.

The end result is a speaker system that way outperforms the older ProAc 2.5 Response. Bass is more accurate & deeper in response. The midrange is much more detailed such as hearing reverberations in a piano cabinet & the Seas tweeter way outperforms the old Scan Speak D2010/8513 tweeter.

Notes: I should add the Seas is an aggressive tweeter and has an almost horn type tweeter sound I like, however it is without any edge or grain of some horn tweeters. A somewhat smoother tweeter is Morel MTD33 that may be more to ones preference.

The low crossover point plus being first order design is demanding on a tweeter. Only use tweeters in the 550 to 750 fs range.

[infinia]

Hi
Nice work. Anymore more pictures please?
Have you tried a zobel on the woofer?

[Andy G]

Just be aware that you may have to do a bit of tweaking to find the best place to cross the series x-o. There is a point where things just seem to lock in, but finding it can take time.
Mind you, with those drivers, if you are somewhere near it will still sound darn good. You may have to pad the tweeter a bit more than is indicated in you diagram, but you will find that out as you go.

Try to leave the x-o outboard until you are satisfied.

Another option would be to go with a 3-way linked series. I have found that they work rather well, giving a very nice blending of the drivers.
http://users.tpg.com.au/users/gradds...ss-overs8b.thm

Have fun, and may your ears be with you !!

[amperex]

I tweaked the crossover with different values. Interesting going from .82mh to 1mh removes the airy & open sound in the midrange. 1uF vs .82uF is a bit too aggressive in the tweeter lower frequencies per my ears. The crossover is about perfect as shown.

I did not try a zobel on the woofer yet. My reasoning is using a 2.5 way instead of 3-way is twofold. First, some rising impedance on the woofer lower frequencies may be a good thing as driving the midrange & woofer lowers impedance below 8 ohms without a midrange series capacitor. On the other hand, a series cap added on the midrange as in a parallel three-way design adds phase shift I do not want either.

Is there a calculator available for that 3-way series crossover? I would like to try crossing at 150Hz & 2kHz.

These new speakers makes the ProAc 2.5 Response speakers sound like cheap $250 per pair Warfedale floorstanders. No kidding. And, that new Peerless HDS Exclusive is far superior in the midrange compared to the old Span Speak mid/bass.

Also, I took a gamble on the Pioneer 12". It is far more accurate a bass speaker over Peerless XLS12, vintage Altec D120 & Stevens Trusonic (forgot model number) I had laying around. All three are gone now.

[Andy G]

Originally posted by amperex
Is there a calculator available for that 3-way series crossover?

yes, there is a link on the page to an excel download.

I think what you are hearing with the bass is the difference between a sub-woofer and a woofer.
I also think that lower excursion woofers sound better in a 3-way design.
Subs are for HT... just my opinion of course.. making no comment about specific drivers.

[tinitus]

Well, the obvious is often overlooked

TUBEamp with a SUBdriver - I dont think so

[Andy G]

What they are hearing is the immediacy of a higher sensitivity low excursion woofer, rather than the large travel bass from a sub-woofer.
There is a definite difference.
Of course you can't throw huge gobs of power at the low-excursion woof, but generally you don't need to at normal listening levels, and while operating within its limits, this type of woofer with do very MUSICAL bass.
Furthermore, if they were attempting to drive the XLS12 sub-woofer with an inadequate amp, then would definitely have sounded muddy and imprecise.

[Andy G]

Originally posted by SY


The mods are MORE than annoyed.

gees , and I was enjoying watching that !!!

[barfind]

Originally posted by Andy Graddon
What they are hearing is the immediacy of a higher sensitivity low excursion woofer, rather than the large travel bass from a sub-woofer.
There is a definite difference.
Of course you can't throw huge gobs of power at the low-excursion woof, but generally you don't need to at normal listening levels, and while operating within its limits, this type of woofer with do very MUSICAL bass.
Furthermore, if they were attempting to drive the XLS12 sub-woofer with an inadequate amp, then would definitely have sounded muddy and imprecise.

I agree completely with Andy. I chose a low excursion woofer over a long throw sub for bass in my system, and these have to keep up with a high quality fullrange. They provide a very musical foundation for my system. But drivers like these need to be implemented carefully, but will give very good results.

Nigel

[Andy G]

Another issue is that if you try to integrate a sub-woofer with a speaker that is already full range, this can also create that "wooly" bass problem.

Each part may be doing its job very well, but if the whole system is badly implemented, then YUK !