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Multi-Way Conventional loudspeakers with crossovers

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Old 30th June 2010, 04:30 AM   #101
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I liked the blog, Tony. I have seen builders adding bucketloads of passive components into an xover just to save a wide 1dB lift. I like my xovers simple if it can be done. When you have finished yours, compare them with the simple 5.6 or 6.8uF and see what they sound like. Just for fun!

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Old 30th June 2010, 05:48 AM   #102
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Tony, just a suggestion, when you cross to your tens, do it at 300Hz but no higher. That leaves the mid woofer to handle all the human voice and at the same time minimises cone excursion. As far as the tens are concerned you will come very close to providing baffle step compensation (If you think it is important) by simply turning up the bass amp.

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Old 1st July 2010, 01:36 PM   #103
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Thanks Terry, I've at various times thought about crossing at 300Hz but when I looked at my original design calcs I had done it was actually planned for 200Hz. The BSC I was contemplating putting into the active crossover has a pot meaning it can be adjusted from 0db right through 6db, excellent for experimenting. I did originally intend to not do any BSC on the MTM's but after seeing the measurements thought maybe a little might be in order.

I will have to try the suggestion of reducing the parts count. Certainly I've done that already (removing the 1k notch, which took out three parts) The resulting graph doesn't look as smooth, but they sound better

I actually decided to start a blank speaker workshop project and re-imported my measurements (individual drivers and the combined response with the current crossover) at least for this crossover the simulation is VERY good. I'll have to try again with the higher order and see if the funnyness persists (but now it is time for bed).

Hows this for a correlation between sim and actual measured response? Black is the sim, and Blue is the actual measured response. all measurements were done with the mic and speaker in the exact same position, crossover was already made, just swapped the wires for the three measurements, and then simmed the actual built crossover with the individual tweeter and woofer responses to get a comparison. Pretty damn close!! If I can get that good a correlation for the 4th order network I'll be very happy

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Old 1st July 2010, 04:07 PM   #104
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Nice Tony.

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Old 1st July 2010, 09:17 PM   #105
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Thanks Dan,

I have to make a correction to the above post though. This bit
Quote:
all measurements were done with the mic and speaker in the exact same position, crossover was already made, just swapped the wires for the three measurements, and then simmed the actual built crossover with the individual tweeter and woofer responses to get a comparison.
Is not correct. It is what I did initially, but I changed the crossover since, and the above is with the latest version of the crossover. I was tired last night. The actual measured response was in fact done a few months after the initial driver responses, and was an on axis one meter measurement, whereas the measurements of the drivers individually were taken at 1.5M. Also for clarification when I say individual drivers, the MW144's were running together and the measurement was taken on axis with the tweeter (ie in the centre of the two drivers). so by individual I mean separate measurements of the tweeter and the MW144 pair When I took 1M and 1.5M measurements on anly particular day there were only very minor differences.

I ended up using the 1.5M measurements because they were the ones I did with time zero locked in holm impulse (and I didn't go back and do 1M ones). This made a big difference for getting accurate sim results, as before I did this, there was only a minor correlation between the sim and the actual results.

Tony.
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Last edited by wintermute; 1st July 2010 at 09:21 PM.
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Old 11th August 2010, 03:38 AM   #106
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Default woops!

I've spent an awful lot of time simulating a new crossover, but I hadn't ticked the box to simulate the impedance... what a mistake!! luckily I've been procrastinating and hadn't bought the components for the 4th order network.

The impedance curve of what I'd pretty much settled on is terrible. around 1.3 ohms at 800Hz.... Back to the drawing board!!

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Old 12th August 2010, 07:18 AM   #107
speedie is offline speedie  Australia
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Smile looks good

hi tony
been off the site for some time now
noticed that you have pushed along with your project
hope that it is all that you crave for as it has taken up a lot of your passion
i still havent got my cabinets but am persueing another cnc shop
cheers speedie
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Old 22nd June 2011, 12:38 PM   #108
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My goodness it's been nearly a year since I posted here!! scarily I haven't done anything much at all. The speakers are fine (more than fine) for TV and watching movies which is their main duty, however I've not been satisfied with them for certain music. Ironically I think one of the earlier incarnations of the crossover was better.

My interest has been re-kindled by the can you have sparkling treble but without silibance thread and more specifically by a post that Lynn Olsen made #17

I think that my crossover point is too low, and I'm getting modulation of the higher frequencies from the lower frequencies that the tweeter is trying to produce.

I did some measurements on the weekend and have attached some below.

The first pic shows the measurements of the MW144's and the DMS37. I used swept sine at 1.2M distance, and starting frequency of 100Hz.

The second pic shows measurements with (blue) and without (red) the padding on the tweeter.These are actual measurements of the speaker with the current crossover.

The orange trace is the result of measuring each of the tweeter and mids with their respective crossover components individually and then summing the response (with tweeter inverted) in holmimpulse. I didn't think to do ta crossover measurement with tweeter inverted on the day.

What this tells me is that the crossover frequency is actually lower than I thought, (it was supposed to be 3Khz originally) at around 2.2Khz, it also indicates that the tweeter is contributing to the overall sonics down to a shockingly low 600Hz

The speakers sound great on some music, but terrible on others, it was Lynns comment on dense material that made the penny drop.

Picture three shows the THD plots for the current implementation...

The fourth picture is the impedance plot of the MW144's measured in the exact same position that the acoustic measurements were taken. The thing I find most strange about this is that it shows no signs of anomalies in the 1-4khz region.

The 5th picture is a nearfiled measurement of one of the two MW144's taken a while ago, and yes that is the raw response, no gating no smoothing.

Anyway I have some more work to do and now at least I have an idea what to focus on, for the particular problem my ears were telling me I had

Tony.
Attached Images
File Type: png mw144_dms37_1.2M.png (54.0 KB, 214 views)
File Type: png crossover_with_and_without_tweeter_padding.png (53.9 KB, 212 views)
File Type: png crossovers_thd.png (50.2 KB, 207 views)
File Type: png mw144s_impedance.png (18.6 KB, 31 views)
File Type: png mw144_nearfiled.png (43.2 KB, 31 views)
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Old 22nd June 2011, 01:27 PM   #109
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Excellent work on these over what looks like the course of more than 5 years!

Don't stress yourself into an early grave over-engineering, though. Don't forget to relax with a nice glass of red and enjoy all your hard work!
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Old 22nd June 2011, 10:09 PM   #110
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Thanks DrDyna yes it has been over about 5 years (8 years if you count the three years thinking about it before buying the drivers ) though there was a big gap there where I did nothing at all...

Some of my cd's sound very good on them, but some are pretty much unlistenable I reaaly find myself wanting to turn it down or completely off after only a few seconds. This is what I want to fix

and you are right (as is Terry) I do tend to over engineer... always striving for perfection I was focusing on getting a flat frequency response before, which is I now suspect and as Terry already pointed out, not an area I need to worry about

Tony.
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