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Multi-Way Conventional loudspeakers with crossovers

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Old 1st April 2003, 01:01 AM   #11
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had another thought on it...
I think I will wait until I finish my Aleph amps, and build a pair of gainclones or something that will drive the woofers well. Then I can biamp and play with the crossover points electronically. What do you think? It seems like an easier way to do the crossover. I'm a little concerned with my ability to build a fourth order that works with no acoustic measurement equipment.
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Old 1st April 2003, 11:16 AM   #12
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I also plan a MTM with 2 P17WJs actively crossed with a small heil tweeter.
Amplification: Aleph (not sure if my just-finished 30 or a dual Aleph-X).

My goal is to make a TL (see the TL6 from www.theloudspeakerkit.com ), but unfortunately they don't sell plans.... and buying a australian kit is gonna kill me for forwarding expenses....

Anyway I was told it is reasonably similar to the Seas Thor, so that project will be my starting point.

Cheers

Andrea
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Old 1st April 2003, 12:29 PM   #13
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Andrea,
I was also considering going the TL route... I'm just not sure that it's a good idea with my midbass problem. I have heard that TL's can have a somewhat recessed midbass. Another option I was considering is a double chamber reflex, but the two woofers wouldn't work too well with the volumes I would have to use (the upper chamber is so small, it would be difficult getting them to fit well).
For now, the plan is to finish up a couple sets of amps and a preamp, and start experimenting with bi-amping and different filters. After that, I will be trying out some different cabinet types. Maybe I'll start with the enclosures first- MDF is cheap!
Good luck on your design.
Steve
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Old 1st April 2003, 12:38 PM   #14
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You're right, a 3/4" radius is ineffective in reducing diffraction from the cabinet edge. It looks good, though.

One more suggestion: if you have or live near someone who has frequency response measurement capability, that may be extremely diagnostic.
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Old 1st April 2003, 03:08 PM   #15
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Quote:
Originally posted by SY
You're right, a 3/4" radius is ineffective in reducing diffraction from the cabinet edge. It looks good, though.

One more suggestion: if you have or live near someone who has frequency response measurement capability, that may be extremely diagnostic.
Unfortunately, I don't know ANYONE around here that is into diyaudio! I would like to find someone even to come and listen to my system (someone else with good ears.)
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Old 3rd April 2003, 05:53 PM   #16
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I got into this thread rather late... so I have a few things to add.

I agree with going for the 4th order L-R crossover - but again, to reitterate - an ACOUSTIC 4th order. For a general rule of thumb, in an MTM design, the best way to go is to use a 2nd order lowpass on the woofers and a 3rd order highpass on the tweeters. This allows the phasing of the drivers to match better, and will get rid of a rather nasty notch at the crossover frequency. This will undoubtedly improve midrange performance.

Also, you complain about midbass. I don't mean to sound like a jerk, but the P17 is not much of a driver in my opinion. Its a great driver for an early project, but I'd advise checking out some different ones. I'd recommend the Peerless 7" CSX driver - this blows the pants off the P17 for midbass detail and yet still maintains some very clean and smooth midrange. Not too smooth where it lacks detail (as in your standard Poly cone - i.e. the P17), but not harsh either. Good mix.

The Vifa PL14 is an unbeleivable driver. It's midbass is unreal for a 5" - better than the Peerless above. I feel it has a bit more detail than say the Focal 4211, which is also a GREAT driver. All I'm saying is consider using a different driver if you want to improve the midbass.

Baffle step compensation is really easy to do electrically - I would definetly try this before redoing your cabinet. May also want to consider how difficult it may be to alter your port tuning. If you need to lenthen the port, you can stuff the port with a bunch of straws... and pull the straws out to the desired length of the port. Pretty neet trick for tweaking the port.

Good luck -
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Old 3rd April 2003, 06:08 PM   #17
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Quote:
Originally posted by Tieftoener
I got into this thread rather late... so I have a few things to add.

I agree with going for the 4th order L-R crossover - but again, to reitterate - an ACOUSTIC 4th order. For a general rule of thumb, in an MTM design, the best way to go is to use a 2nd order lowpass on the woofers and a 3rd order highpass on the tweeters. This allows the phasing of the drivers to match better, and will get rid of a rather nasty notch at the crossover frequency. This will undoubtedly improve midrange performance.

Also, you complain about midbass. I don't mean to sound like a jerk, but the P17 is not much of a driver in my opinion. Its a great driver for an early project, but I'd advise checking out some different ones. I'd recommend the Peerless 7" CSX driver - this blows the pants off the P17 for midbass detail and yet still maintains some very clean and smooth midrange. Not too smooth where it lacks detail (as in your standard Poly cone - i.e. the P17), but not harsh either. Good mix.

The Vifa PL14 is an unbeleivable driver. It's midbass is unreal for a 5" - better than the Peerless above. I feel it has a bit more detail than say the Focal 4211, which is also a GREAT driver. All I'm saying is consider using a different driver if you want to improve the midbass.

Baffle step compensation is really easy to do electrically - I would definetly try this before redoing your cabinet. May also want to consider how difficult it may be to alter your port tuning. If you need to lenthen the port, you can stuff the port with a bunch of straws... and pull the straws out to the desired length of the port. Pretty neet trick for tweaking the port.

Good luck -

Hey, thanks for the ideas!
A couple questions for you:
I understand what you mean by an acoustic 4th order response, but dosen't the driver's response dictate to some extent what filters and slopes you will use to get the 4th order response? If so, can you really say for sure that a 2nd low and a 3rd high will work, or are you giving a typical example?
As for your opinion of the P17, I would have to agree, and you're definitely not a jerk for stating your opinion. It's not the most fantastic driver available. The choice would most likely be different now. Thanks for the driver recommendations- I always like to hear what other people have found. One thing I have found is that many of the highly regarded systems use drivers with more exotic cone materials. When I look up the spec sheets on these, I see that they often have a much rougher frequency response than the poly cones like the P17. I am assuming that the trade off is complexity for more resolution. Is this the case?
I will definitely try adding some passive bafflestep compensation before I do anything else. The bass response has good extension, and is fairly controlled- much more so than I would have expected from a ported system. I just have never been happy with the balance of the system. I didn't know anything about bafflestep when I built them, but I think it may take care of most of my complaints with little work. They are definitely sensitive enough to throw some away- about 92.5 db/1W.
Thanks for the help... Any other comments / suggestions are appreciated.
Steve
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Old 3rd April 2003, 07:36 PM   #18
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Today speakes are way better than what they use to be, speaking of regular ones, as mentioned on this thread so what I'm about to say may not even applay.

Years back, when the original project from D'appolito came out I built the complete Swan system as proposed by him, including the electronic crossover for biamping (at a later day).

Not satisfied with the results I started to changed passive xover components, tested 3/4th order to different aligments, series and parallel midbass configuration and what not. In the end I trashed the project and moved to other simpler systems.

My conclusion was that the high number of pasive components on the xover really killed transients and inner details besides the regular problems of lobbing / combing that you never are able to get rid off.

Adding a baffle-step will surely change the balance and help your midbass but the bass itself may become to much for a balanced sound.

I'm not discouriging the test of the Bafflestep, this is a very easy test and you have the resistor to play around for deeper or shallower effect. Having a very narrow baffle and small enclosure I would use a 4 to 4.5 mH inductor for the test (assuming 8 Ohms speaker impedance).

Let us know your findings.
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Old 3rd April 2003, 07:55 PM   #19
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appasgear,
I have heard that said by a few different poeple on this board (about the complexity of the crossover causing more problems than it solves). I tend to lean toward the simpler approach whenever possible too. There are a few drivers out there that are using some different cone materials AND achieving flat response. Vifa's MD series come to mind. It's strange though, that the scan speak version of the glass fiber cone speakers have rough response, and that the Vifa MD series, using the same type cone and at half the price are smooth.... I don't know what to think about that.
When using a receiver that has a semi-parametric bass control, I have found through listening that 6db of boost from about 350 Hz on down really improved the balance of the system. I think the zobel is needed. I guess we will see. Thanks for the suggested starting point.
Steve
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Old 3rd April 2003, 08:39 PM   #20
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nobody special:

Sorry - I wasn't very clear earlier. I like the 4th order L-R acoustic approach.

Another approach that many use and have good results with is using a 2nd order LP on the woofer and a 3rd order HP on the tweeter (for MTMs) - with regards to electrical crossover. Iin a lot of cases, this second approach can actually be used to produce a 4th order L-R acoustic response... just a matter of implementation. But as you mention - driver response does have an effect on this.
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