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Multi-Way Conventional loudspeakers with crossovers

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Old 12th November 2019, 01:50 AM   #81
8ntractor is offline 8ntractor  Canada
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I really like Holms, I think the ability to see the distances is really great. I am not confident in any of the measurements. I have to continue to work on the measurement system I think I have to focus on the device and signal section. thank you again Allen
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Old 13th November 2019, 09:19 PM   #82
8ntractor is offline 8ntractor  Canada
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The felt really did work the 7k dip is better. Brilliant. I think if I do make new boxes I will have felt or sound deadener around the tweeter.

Not really understanding the treble rolloff. the speakers actually sound pretty good at the listening position not sure if the spl meter is accurate at the higher frequencies. maybe a 6 db rolloff on the treble is not terrible with the mtm design. I would like to know if it is real or not. is there any problem with putting a small resistor in parallel to C1? it looks like it would lower the most of the woofer to try to start working on matching the tweeter.
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File Type: jpg felt listening position.jpg (74.1 KB, 50 views)

Last edited by 8ntractor; 13th November 2019 at 09:40 PM.
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Old 13th November 2019, 09:55 PM   #83
AllenB is offline AllenB  Australia
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I don't mind a treble rolloff, however yes as you suggest, mics do have issues up here. Did yours come with a calibration file? Sometimes generic ones are available that are better than nothing.
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Old 13th November 2019, 10:00 PM   #84
AllenB is offline AllenB  Australia
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C1 is part of a notch at 4,500Hz. Shunting it with a resistor would probably affect the upper bass/lower midrange specifically. Typically the woofer level isn't worked on, if you want to raise the treble, change R2. However, if you need more treble we can try to bring down the woofer.
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Old 14th November 2019, 08:39 AM   #85
8ntractor is offline 8ntractor  Canada
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Thank you Allen

I will take out R2 is there any downside to removing those components R3 and C4 are already removed. I don't think it will change the impedance much.

I am using a Radio Shack analog SPL meter for a mic. I know they roll off on the treble but REW is suppose to correct for that when the c weighting is used. but there is probably a ton of variation from one unit to the next.

The Nextel woofers have a sensitivity of 87.5 and the Magnesium drivers were 86. I spent quite a bit of time looking for established designs and most designers pair the Nextel woofers with the crescendo tweeters 92.5 as they are more sensitive than the millennium tweeter 89db. with the pair of woofers I think pairing them adds sensitivity so the millennium tweeter may not be able to play loud enough. Like you say the rolloff may not be a bad thing the speakers are sounding better. Not sure if I am getting used to them or if the woofers are breaking in. I will take out R2 once I hear back from you and then I can use the iTunes eq and try boosting the treble. wont help with cds or albums but maybe I can get a sense of whether or not it is worth working on reducing the woofers. thank you again for all of your help.
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Old 14th November 2019, 10:28 AM   #86
AllenB is offline AllenB  Australia
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Without R2, I think you'll find that R3 and C4 have close to no effect, seen or unseen. Leave them in if you want.

I used to use an RS SPL meter. I looked for my old cal files, couldn't find them. I once had one that was an amalgam of dozens of mics. I also settled on one that I found I like the sound of the results from. Calibration returned results from the high end as well as the bass.

There are a number of tricks and considerations you can use when trying to get more level from the tweeter. This should be no problem.

You mentioned gain from the woofer pair. Yes, they will add 6dB, however at higher frequencies this becomes directional which complicates things.
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Old 14th November 2019, 04:03 PM   #87
8ntractor is offline 8ntractor  Canada
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Hello Allen I found a cal file for the SPL meter on line and added it I also added soundflower to help with the soundcard on the mac. the results are very different than earlier results. Based on these results I should put R2 and C4 back in. Is there any definitive way to know which results are correct. I do n't think I can necessarily here a few db on the treble without a reference. thank you again for all of your help.
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File Type: jpg right new cal listening position.jpg (94.9 KB, 39 views)
File Type: jpg right new calc one meter.jpg (85.0 KB, 38 views)
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Old 14th November 2019, 10:42 PM   #88
AllenB is offline AllenB  Australia
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I see your dilemma. In that situation I'd go back to without the cal file because the error has a simpler nature than two random errors intertwined, but I did eventually achieve satisfaction.

To find out for sure you either have your mic calibrated professionally, or you buy one that is. Or, you can invite a friend over with their calibrated mic and run a careful comparison to create your own cal file.
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Old 15th November 2019, 01:23 PM   #89
8ntractor is offline 8ntractor  Canada
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Hi Allen thank you I will have to find a way to calibrate my spl meter or get a new mic. I spent time today on speaker position and measuring / listening at the listening position. I was able to get the ocean waves of the room modes within +/-6 and the rest within +/-3 the charts are choppy and I am not sure if that is something that could be fixed in the crossover or just the way the drivers are made or maybe like you showed me in adding the felt they are caused by cabinet errors. Tow in and out of the speaker makes a big difference on rolloff of the tweeter.

You mentioned earlier
Quote:
R3/C4 cut in around 6k to make sure that R2 can continue attenuating through the higher frequencies despite the rising impedance.
Would making R2 larger reduce the 3k to 10k region to try to keep the slight downward slope going. I am also reading the design your own speaker from scratch thread and will now be more careful before heating up the soldering iron.


the speakers sound pretty good male and female, rock and jazz all sound pretty good. Classical still needs some work . Between the speakers imaging and soundstage are pretty good but not much happening to the outside of the speakers

thank you again for all of your help
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File Type: jpg best position in room.jpg (78.0 KB, 31 views)

Last edited by 8ntractor; 15th November 2019 at 01:37 PM.
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Old 15th November 2019, 11:12 PM   #90
AllenB is offline AllenB  Australia
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Some good work finding a room location with low frequencies distributed that way.

To get the tweeter downward trend you could also decrease R3, and if needed increase C4.

Now, reading this chart is different. Ignore the smaller wiggles up high, just follow the trends. I see a room controlled region down low, a hole above it, a twitch just above 400Hz, a slight downward slope, a twitch at 2kHz etc. etc. The twitches will probably show on the group delay plot.
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