Xover design... - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 15 Old 10-25-06, 11:17 PM Thread Starter
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Xover design...

Brian:

Do you do xover design for other people, or just for your speakers?

How do you go about xover design? Do you have a test chamber for measurments etc? What software tools do you use?

I am asking not because I want to do my own, but because I'm interested in having someone designing and perhaps building xovers for speakers I'm thinking about building.

I was looking at a multiple midbass with a single tweeter perhaps MMMMT. The drivers I am thinking of using would be PE 264-816 & 275-085. It looks like a crossover in 4khz range looks good on paper to tame the nasties above 5khz in the 264-816.

My choice of these drivers is simple, I have wanted build a speaker with a planar/ribbon tweeter, this one is fairly inexpensive and handles a fair amount of power. The reason for the midbass units, is I wanted something that would allow a reasonably high xover, was fairly small and had some bass. The reason for four of them is based on my understanding that 4 would increase the spl to match the tweeter and have the added benefits of more bass and in series/parallel would be 8 ohms, making the xover design simpler.

I worked with a fellow locally in South Florida that was talented, but we chose not to work together, he thought I was taking advantage of him, and I wanted prices to remain consistent between jobs.

At the moment I do not have the time to get good at xover design would be interested someone that would do a good job for a fair price.

Paul
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post #2 of 15 Old 10-27-06, 08:46 PM
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Re: Xover design...

Paul,

Sorry that I haven't responded sooner. I've been pretty busy at work and getting ready for my wedding next weekend. I think you'd be better served looking at some different drivers (especially the tweeter) but I don't have time to go into it right now. Give me until tomorrow to get all of my thoughts together and I'll give you a more in-depth response then.
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post #3 of 15 Old 10-27-06, 11:08 PM Thread Starter
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Re: Xover design...

Congratulations on your impending nuptials...

I will wait patiently...

I was hoping someone might have had some experience with the inexpensive ribbon/planars... Perhaps they are inexpensive for a reason...

Paul
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post #4 of 15 Old 10-28-06, 06:49 PM
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Re: Xover design...

Paul,

I've seen the ribbons used in a few line arrays, and heard them in one line array, but that's the extent of my experience with them. From everything I've read the BG Neo 3 planar tweeter is a much better option. It costs a little more and is not as efficient but I think it's much better option. Also, I think you'd be better off going with something like the Dayton RS 5" drivers than the Tang Band 4". The Dayton is actually a lot closer to a 4" driver than a 5". Also, it's only a few dollars more than the TB but is a much nicer driver in my opinion.

I don't have any kind of chamber, as I do everything out of my home. I still have a lot of help with my crossover design but do have LspCAD and JustMLS and am learning to use both. As I learn to use JustMLS better I'll be taking measurements outside to eliminate the effects of the room and then import the data into LspCAD.

I wouldn't mind designing something along the lines of what you're talking about anyway so if you want to work together on something that would be great. But first I'd like to find out exactly what your needs and expectations are and we can go from there.
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post #5 of 15 Old 10-28-06, 08:22 PM Thread Starter
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Re: Xover design...

Brian:

I was unable to find a Dayton 5" RS driver. What is the PE part #?

My design criteria is fairly fluid but basically I am interested in a thin speaker cabinet, perhaps floor standing, I want to play with a ribbon type driver, I would like something that would xover to a sub at 80hz. I think keeping the mid/tweeter xover above 2.5khz is a good idea.

I'm interested in drivers that don't need a lot of manipulation to be fairly flat. My concept for these drivers were TMMMM for the front & rear, and MMTMM for the center.

You mention that you heard a speaker with these tweeters in it, but didn't mention your impression... I assume it wasn't good, what was the problem with it?

Paul
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post #6 of 15 Old 10-28-06, 09:47 PM
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Re: Xover design...

Paul,

The driver is the Dayton RS125S-8 (PE part# 295-360). I think 4 of them would work pretty well with a 28L (1ft^3) enclosure. Assuming 3/4" material, I think a cabinet 38"H x 7"W x 12"D would work quite well. If you wanted to limit depth a bit the cabinets could always be made taller, but it really depends on what you want tweeter height to be.

Any special reason you prefer to keep the crossover above 2.5KHz? I know that the tweeter used might make that a necessity. My towers use dual RS 10's, dual RS 7's and the RS28a tweeter. My mid/tweet crossover is at 1.6KHz, but is extremely steep (around 8th order). For a center channel I'd recommend 2.5-way design so that you could eliminate comb filtering for anyone sitting off axis.

The line array I heard with the Dayton planar tweeter actually wasn't too bad. The main thing I didn't like about it was that the tweeter line wasn't long enough. It's been a good 3-4 years ago since I heard it though so it's hard to truly remember the sound other than them being very dynamic. I do know this tweeter was compared to the BG Neo 3, along with several higher dollar true ribbons. The BG was ruled the winner and the Dayton planar was considered last place.
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post #7 of 15 Old 10-29-06, 08:29 AM Thread Starter
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Re: Xover design...

I like the Dayton RS 5", the specs look good, the size is only 5/16" larger, and the price is about $4 more per driver. That coupled with the low le, and the nasties don't crank in until about 12 khz it seems like it would work well.

Winisd shows a .64 cu ft, 17 litre box yeilds an f3 at 62 hz which should be acceptable with a sub.

What I don't like about the neo is the output is weaker, the power handling is 1/4, the impedance is 4 ohms, and when you add the mounting ring the cost is almost $20 more per driver. That coupled with my opinion that it is butt ugly makes it undesireable.

I suspect the neo would be good with two of the RS 5" drivers for a more refined system, but for home theater I want something I don't have to worry about the kids (My wife will say that I'm the biggest kid) cranking and frying...

I think a 12db crossover at 2.5 khz for this combination looks good on paper, might need something additional to attenuate the nasty hump at 12-15khz. Of course until the cabinets are built and the drivers are measured in the cabinets we really won't know.

I'm not familiar with a 2.5 way design, and only have a vague idea about the comb filter problem you are refering to. Could you point me to someplace that will educate me?

Paul
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post #8 of 15 Old 10-29-06, 04:33 PM
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Re: Xover design...

I use Unibox for my box designs most of the time and I find it much more accurate than WinISD. I think 17L is a bit on the small side but if you tune around 50-55Hz it doesn't look too bad. Oh, and what are you planning to use for a subwoofer?

A 2.5 way design is one where you have multiple woofers in a design. The upper woofer(s) cross over to the tweeter and play all the way down to the low frequency limits of the driver. Then your .5 woofer(s) will cross over at some frequency below the mid/tweet crossover and only reproduce the lower midbass/bass frequencies. Many times this is done to keep efficiency up by allowing the lower .5 woofers to handle the baffle step compensation.

I'll have to see if I can find something in particular about comb filtering. It's really an issue with short, wide center channels where the woofers flank the tweeter. The center to center spacing between the woofers ends up being so great that anyone that sits much off center of the tweeter will have a lot of trouble with vocal intelligibility. This is due to the listener being different distances from the two (or more) woofers and results in a very chesty sound, especially on male vocals. This is why I would suggest using a 2.5 way crossover so that only the two inner woofers are crossing over to the tweeter and reproducing the vocal range. Without doing this things would get very nasty for anyone sitting off center.

Here's an interesting center which is actually a 2.5.5-way using six 3" woofers.

http://www.partsexpress.com/projects...ure/index.html

Oh, and here's the article where the Dayton planar tweeter (same as the Silver Flute tweeter that Madisound sells) was compared to various other ribbon/planars. Read this before you decide you definitely want to proceed with this tweeter.

http://www.zaphaudio.com/nondomes/
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post #9 of 15 Old 10-31-06, 04:38 PM Thread Starter
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Re: Xover design...

zaphaudio certainly has strong opinions about the silver flute planar tweeter. You'd think the designer made a pass at his wife & kicked his dog...

Paul
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post #10 of 15 Old 11-15-06, 12:05 PM
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Re: Xover design...

Yeah, he didn't care for that tweeter at all. Like I said, I only heard it once and that was in a line array several years ago. In that capacity it wasn't too bad. I'm just not sure how good it would sound with only a single unit running.
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