Wondering if a Classic 2.5 clone can be made with a series crossover on the woofers

[Kootskid]

Hi,
I have some DC160 -4 woofers and DC28F-8 tweeters. I am inquiring if it would be possible to use the 2 woofers in series for an 8 ohm system in the Paul Carmody Classic 2.5 TMM enclosure. I know I can make an MTM, but would rather have a TMM. Thanks for your time.

Myles

[Geoff Millar]

Hi,
I have some DC160 -4 woofers and DC28F-8 tweeters. I am inquiring if it would be possible to use the 2 woofers in series for an 8 ohm system in the Paul Carmody Classic 2.5 TMM enclosure. I know I can make an MTM, but would rather have a TMM. Thanks for your time.

Myles

It won't be a 'clone' as you're using different drivers, in particular, the tweeter's different. What I think you're after is a TMM/2.5 way crossover for those drivers, with the bottom woofer providing the Baffle Step Compensation as per the Classix 2.5 design. This will mean a new XO.

Enclosure-wise, without modelling I think the Classix 2.5 cabinet could be OK as the 160-4s and 160-8s have similar parameters.

There are a few designs around for a DC160-8 and DC28F MTM, but none that I've found for the 160-4 and no TMM 2.5 projects; happy to be proved wrong of course. The 2.5 feature adds additional fun/issues to deal with in working out a crossover.

Sorry I can't be more help but other PETT members may have some suggestions for you.

Geoff

[Chris Roemer]

Don't know, but don't THINK you can get to a 2.5-way using a pair of 4ohmers in series. I think a ".5" necessitates that the woofers be (wired/filtered) in parallel. (Wolf prob. knows the answer to this - perhaps he'll pop in?)

[Kootskid]

Thanks for the help so far. I have looked in with Curt Campbell in regards to building a larger version of his TriTrix. If Curts MTM model is what I build, I will have to decide on whether I want to build the TL's or the smaller version. Let's see if Wolf chimes in.

[Geoff Millar]

Don't know, but don't THINK you can get to a 2.5-way using a pair of 4ohmers in series. I think a ".5" necessitates that the woofers be (wired/filtered) in parallel. (Wolf prob. knows the answer to this - perhaps he'll pop in?)

That's certainly the case with the Classix 2.5 and one other project I've seen somewhere.

An MTM with the DC160-4 and DC28F could be modelled - I could try it in Xsim if you wish - by adapting an existing design for a DC160-8/DC28 two way.

This might be tricky: the DC160-4 - using the factory supplied data in Xsim, shown below - has a rougher FR than the 8 ohm version, so the XO will need an expert touch. Not mine!

The red is the DC160-4; connecting two in series will obviously affect the FRD and ZMA graphs.

Geoff

[Kootskid]

Thanks for the preliminary sim, Geoff. Not sure what my next move should or could be with these 4 ohm woofers. I may get a hold of Curt and see what recommendations he can give me on a larger model of the TriTrix, as it has woofers wired in series

[Whitneyville1]

CAN it be done? Well, yes. Is it worth the extra parts to make it sound good??? Very tough question. On U-toob I get asked questions about "can I get 1000 HP from a Chebby skinny block?" I say yeah, but it'll only last about 15 minutes at best and cost you $20,000. They've read magazines and seen u-toob videos. I've got scars on my hands and spent money and picked up pieces. I love my Classix II's, but messing around with Paul C's design wouldn't be my first choice. Paul C. combined the "wibbles and wobbles" of the DC-160-8 with the Vifa BC25TG15's response with a filter he designed for one of the most listenable speakers (for imperfect sources) I've ever heard. You can mess-up what he did very easy. I've built 7 or 8 pairs and strayed some from his exact design and still gotten excellent sound (building them into old console stereos for example) and I was shocked how good they sounded, but messing with the drivers and XO-ers could be like teasing barracudas...you pull back a bloody hand, worse than sharks.

[Geoff Millar]

CAN it be done? Well, yes. Is it worth the extra parts to make it sound good??? Very tough question. On U-toob I get asked questions about "can I get 1000 HP from a Chebby skinny block?" I say yeah, but it'll only last about 15 minutes at best and cost you $20,000. They've read magazines and seen u-toob videos. I've got scars on my hands and spent money and picked up pieces. I love my Classix II's, but messing around with Paul C's design wouldn't be my first choice. Paul C. combined the "wibbles and wobbles" of the DC-160-8 with the Vifa BC25TG15's response with a filter he designed for one of the most listenable speakers (for imperfect sources) I've ever heard. You can mess-up what he did very easy. I've built 7 or 8 pairs and strayed some from his exact design and still gotten excellent sound (building them into old console stereos for example) and I was shocked how good they sounded, but messing with the drivers and XO-ers could be like teasing barracudas...you pull back a bloody hand, worse than sharks.

Anything else aside, the DC28 is a very different sounding and behaving tweeter to the VIFA which Paul used, so even if you used DC160-8s in parallel, as per the design for the Classix 2.5, the speaker would be highly unlikely to work well with the Dayton.

Moreover, the VIFA is a nominal 4 ohm tweeter and the DC28F is 8 ohms, so there's an additional set of issues.

In theory, a MTM design such as the Dayton DIII: http://projectgallery.parts-express....cts/the-d-iii/ which uses the DC160-8 and DC28F might be adapted to use the DC160-4s in series, but then there's the differences in the woofers' response (see Xsim graphs above) to deal with in the crossover.

Probably not what you wish to hear, sorry.

Geoff

[Wolf]

It is not possible to make a 2.5-way with the 4 ohm woofers in series without using about 3x the parts in the xover. Unless a special 'reinjection' topology (3x parts) is used, you'll have a 2 ohm net impedance.
A series xover is a whole other ballgame, and I'm sure the OP did not mean this wording nor this direction.

Later,
Wolf

[Geoff Millar]

It is not possible to make a 2.5-way with the 4 ohm woofers in series without using about 3x the parts in the xover. Unless a special 'reinjection' topology (3x parts) is used, you'll have a 2 ohm net impedance.
A series xover is a whole other ballgame, and I'm sure the OP did not mean this wording nor this direction.

Later,
Wolf

Yes, I think the idea was to make a bigger Tritrix-type design where two 4 ohm woofers are connected in series in an MTM configuration. At least in Oz, using 3x as many crossover parts would mean that the crossover costs more than the drivers.

Going back to the OP, does anyone have a suggestion(s) about how those drivers might be used?

Geoff

[Kootskid]

Everyone,
Thanks for the valuable knowledge concerning the above drivers. Since the 2.5 is out of the question, and I am not fond of MTM's:

Could a MT be built or TMWW be built with the WW wired in series

Myles

[Geoff Millar]

This thread might give you some ideas, it's the only discussion I've found about using the DC160-4s in a TM. It also uses the DC28F:

https://www.diyaudio.com/forums/multi-way/284815-real-build.html

Of course, I haven't heard these and have no idea how they might have turned out.

Geoff

[Kootskid]

Thanks Geoff,
Any ideas on the TMWW or would I have the same problem as the 2.5 way if the woofers are in series. Maybe not as this would be a 3 way?

Myles

[LOUT]

It is not possible to make a 2.5-way with the 4 ohm woofers in series without using about 3x the parts in the xover. Unless a special 'reinjection' topology (3x parts) is used, you'll have a 2 ohm net impedance.
A series xover is a whole other ballgame, and I'm sure the OP did not mean this wording nor this direction.

It looks (to my inexperienced eyes) like it's possible to mostly treat it like a regular low-pass at the beginning and then add a large Cap (and maybe a small resistor) in parallel with one of the woofers to create the extra 0.5 step.

I'm not saying it resembles the original design or anything like that, but I think it looks like a viable way to make a 2.5way from a pair of 4ohm speakers aiming for a ~6.6ohm minimum. Which means I'm probably missing something important and detrimental about this.

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[Wolf]

The cap-bypass on a woofer method is not supposed to work properly. There are threads here at PETT about just this idea in particular, and the greater minds than me said it does not work.

Later,
Wolf