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Multi-Way Conventional loudspeakers with crossovers

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Old 27th October 2006, 08:21 PM   #11
Jonasz is offline Jonasz  Sweden
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MuaDibb: http://www.zaphaudio.com/BAMTM-2.00-MTM-Sub.pdf
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Old 27th October 2006, 08:31 PM   #12
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Zaph,

Did you have the PE pre-fab cab in mind when you designed the integrated sub section? It almost looks like a perfect fit, save for the slightly shorter depth. Then it could be a modular, removable system a la the NHT Evolution. Also, I know you recommend prosound amps and not plate amps for this project, but I noticed that one of the BASH amps, thanks to their long and narrow proportions, would fit nicely on the back panel. Granted, it would be expensive to use two of those in stereo.

Do you have any thoughts on these ideas? Thanks a lot for posting the design. Keep up the good work!
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Old 27th October 2006, 09:06 PM   #13
Zaph is offline Zaph  United States
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Quote:
Originally posted by sdclc126
I do have one other question - it's only indirectly related to this design, but have you ever considered open baffle/dipole? I am intrigued by the concept and have wondered how to do a "budget" version of something like the Linkwitz Orion. The reason this is somewhat relevant to the BAMTM is that it occurred to me that its driver compliment might make a workable OB top end (with appropriate crossover and equalization), and coupled to a dipole bass unit.
At this point, I've done at least 1 or 2 of just about every type of loudspeaker. There are some types however you aren't likely to find on my web site (yet) because I consider others to do them better than I do. Dipoles are one type of speaker like that. But, I guarentee there will be a dipole on my web site some day. It will be fully passive (and therefore budget oriented) because I don't want to own multi-amped speakers with an active crossover.


Quote:
Originally posted by widman
I too am interested in building a BAMTM, specifically the vented floorstander. Your drawing shows damping material in the upper 36" of the enclosure. Is this supposed to be whispermat/sonic barrier as you've used in some of your other designs? Also, where you show extra damping at the bottom, do you mean insulation only on the base or stuffing the last 8"?
Yes, whispermat or sonic barrier is the optimal damping material on top. In the bottom of the vented enclosure where I specify 8" thickness of damping, packed dacron fiber will work fine. This will absorb the lengthwise pressure node. Good observation, I should add that to the page.


Quote:
Originally posted by coolkhoa
Did you have the PE pre-fab cab in mind when you designed the integrated sub section? It almost looks like a perfect fit, save for the slightly shorter depth. Then it could be a modular, removable system a la the NHT Evolution. Also, I know you recommend prosound amps and not plate amps for this project, but I noticed that one of the BASH amps, thanks to their long and narrow proportions, would fit nicely on the back panel. Granted, it would be expensive to use two of those in stereo.
Actually, a PE box on the bottom would work fine for a modular sub. If you were going to use the 10" RS sub, you'd certainly want to glue the front baffle on solid or the sub will rattle the 4 "b-rex" bolts right apart from the high pressure. Also, when cutting the side opening, you'd have to figure out a way to remove the crossbrace inside to clear the woofer.

Likewise, a person could just use the PE box on top and build subs into stands below.

One quick edit: the power supplies in some plate amps tend to hum when close to massive woofer magnets. In a smallish enclosure where space is at a premium, it's hard to put some space between these. And naturally, if space is hard to come by, an external amp works better.
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Old 28th October 2006, 08:44 AM   #14
JonPike is offline JonPike  United States
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Thanks for another well worked out and well documented design..

Probably several things I would want to ask eventually, but the first one is related to the comments of power handling...

I'm curious at about what power/SPL level do the "problems" set in.. i.e. the compression in the woofer you mention in the writeup when you reach the limits in driving this particular design.

I'm trying to get a feel for overall power handling and dynamic range... and at what point would the diistortion and compression start to become an issue...
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Old 29th October 2006, 12:22 AM   #15
keyser is online now keyser  Netherlands
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John,

after the nice high-end ZD5 speaker, it's good to see you back to where your roots lie .
In this design you chose to cross the tweeter at an unconventionally low frequency. The nasty breakups of the Daytons of course gave reason to try it out.
In other models with this same (very robust) tweeter you used a higher crossover point. The partnering drivers were all better behaved in the higher mids than the Daytons.
Knowing that the low crossover point works so well in this combination, do you now think that a lower crossover point might also have been good option in other designs you've previously done? What do you consider to be the pros and cons of such low crossovers?
Thank you very much, and keep up the wonderful job you are doing for the DIY community!

Regards,
Martijn
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Old 30th October 2006, 04:05 AM   #16
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Default Project Update....

I'm in the progress of building this design with a twist. Being very new to DIY speaker building, I am always looking to learn and understand as much as possible with this hobby. With this design, I am building a 2 cu ft tower speaker, with removable baffle and movable shelf braces. My intentions are to try out a few of the different enclosure recommendations. I will be able to do the 1 cu ft sealed, 1.5 cu ft sealed, and the 2 cu ft selaed and ported. I am hoping to understand what sounds best to me in my listening room.

The attached pictures show a completed previous project, rs150 MTM by CJD with the rs28a tweeter for comparison that I use for my HT.

I only have 4 screws in the baffle (will add more) but the test run so far has been very pleasing. I am by no means an audiophile, so I will not try and wax poetic, but I am very excited about this budget design. I must say, the seas tweeter sounds awesome, very similar to the rs28a and even $15 cheaper.

Click the image to open in full size.

Click the image to open in full size.
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Old 30th October 2006, 01:49 PM   #17
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Hey outfitter -

Great looking builds there. I just got wind of the CJD design and am interested in building a 2-way version of it. I haven't searched for it yet - can you provide a link, or send me the XO plans? I'd greatly appreciate it. Feel free to email me.

Thanks!
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Old 30th October 2006, 07:46 PM   #18
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CJD has a site for his MTM here-

http://www.eldamar.net/audio/rs150mtm/

There is also a write up for BSC and non-bsc designs for a MT. I am going to be adding the non-bsc for on-wall surrounds sometime in the future. That one is here- post #62

http://www.htguide.com/forum/showthr...6&page=2&pp=35

If you look at the write up on his site just swap at the values in the schematic, and it will make sense.
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Old 31st October 2006, 03:14 AM   #19
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Quote:
Originally posted by outfitter
CJD has a site for his MTM here-

http://www.eldamar.net/audio/rs150mtm/

There is also a write up for BSC and non-bsc designs for a MT. I am going to be adding the non-bsc for on-wall surrounds sometime in the future. That one is here- post #62

http://www.htguide.com/forum/showthr...6&page=2&pp=35

If you look at the write up on his site just swap at the values in the schematic, and it will make sense.
Thanks outfitter - this is it! Hopefully not too far in the future I'll have my first real build to post.
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Old 31st October 2006, 02:50 PM   #20
Zaph is offline Zaph  United States
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Quote:
Originally posted by JonPike
I'm curious at about what power/SPL level do the "problems" set in.. i.e. the compression in the woofer you mention in the writeup when you reach the limits in driving this particular design.
Well, I wouldn't call it problems with the DA175, just limitations of a lower tech motor design. The two types of distortion we're talking about here are thermal and BL. At lower levels, the DA175 performs on par with the Seas L18. As millimeters of Xmax get used up, the DA175's generic flat and straight pole piece causes BL distortion to accumulate faster than some better motor designs that have better BL curves.

Thermal is simply the driver's ability to maintain it's measurements at higher levels as the voice coil and suspension heat up. This can be easily seen in response and impedance curves that are increased in incremental levels. For example, starting at 90 dB/1m, then running response and impedance plots in increments at levels 5 or 10 dB higher to observe the changes.

This kind of testing is still somewhat important, but I usually don't do it due to time constraints. Soundeasy can do Volterra Series Expansion, which is more of an estimate of a BL curve rather than an actual Klippel-style measurement, but still useful. Some day I'll post a set of measurements so you guys can see what this looks like. I'll use the L18 and DA175 too, as these drivers really point out the difference that motor design can make. People want to just add up the Xmax, calculate out the volume displacement and use that to determine how loud a speaker will get, but it's not that simple. A single L18, through most of it's bandwidth, will play louder with lower distortion than two DA175's. Make no mistake that the DA175 is a great woofer, but the higher price of the L18 does get some performance improvements in this case. This sort of leads into the next question.


Quote:
Originally posted by keyser
In this design you chose to cross the tweeter at an unconventionally low frequency. The nasty breakups of the Daytons of course gave reason to try it out.
In other models with this same (very robust) tweeter you used a higher crossover point. The partnering drivers were all better behaved in the higher mids than the Daytons.
Knowing that the low crossover point works so well in this combination, do you now think that a lower crossover point might also have been good option in other designs you've previously done? What do you consider to be the pros and cons of such low crossovers?
The breakup of the DA175 is not really that bad. I chose the lower crossover frequency of the 27TBFCG for other reasons, compared to the 2000Hz in the L18 design. First off, MTM lobing is far worse than MT lobing and the lower crossover point helps minimize this or at least limit it to only woofer c/c issues. If you've ever seen the power response of a large MTM with a high crossover point, you'd know what I'm referring to.

Secondly, the L18 is a system that will play relatively loud. In a system like that, it's wise to cross over the tweeter with consideration to the system's overall abilities. In that system, the tweeter will not be the limiting factor, but if I'd crossed over at 1450Hz, it might be.

Finally, there is an economy to crossover topology. I could have crossed the L18 system over at 1450, but I would not have gotten away with the simple crossover design. The single notch and inductor on the woofer serve multiple response shaping purposes that only worked for the 2000Hz crossover. Crossing over at 1450 would require a much more complex crossover. Likewise, with the DA175, crossing over higher would have required a notch for the breakup and a couple more components to shape the response.

A single DA175 could probably cross over around 2kHz LR4 without distortion issues. On the other hand due to the limited output of the DA175, I don't think I'd want to use only a single one in a system unless it's specifically for low levels only.

I consider all of the above when I pick a crossover point.
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