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Yamaha NS-6490 improvement project

ROOSKIE

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I never said that Alex-Z was incorrect - far be it for me to make that claim. I believe I've been quite clear in my replies. And my beef with him is one of attitude, not expertise.

I never said these speakers were a "diamond in the rough". In fact, I accept the technically detailed and substantiated evaluation presented in the other thread. Did you read that?

I never said I had decided on rockwool to line the cabinets. In fact, the general consensus within the speaker-building community is to line ported cabinets. This is an acoustic suspension-style speaker. I have since decided to stuff them with Acoustica-Fil.

I've also decided to replace the mid with a slightly better, yet reasonably-priced one that matches the selected crossover, since the woofer is doing most of the midrange work in Yamaha's cheap capacitor-only solution.

Why am I wasting my time on this project? Because I have more time than money, being retired after 30+ years in electronics/electromechanical repair, training, and support, as well as 10 years with the US Department of Defense. In my "beginner" opinion, it's worth $100 or so to try and improve these speakers, rather than just throw up my hands and say "there's nothing I can do" or buy another pair, and relegate these to storage space I don't have. AGAIN, if they're the worst speakers ever as y'all claim (they're not), then they can only get better, even if it's just a little.

So I will consider your comments, but I'll make my own decisions based on criteria other than purely technical. But why are you wasting YOUR valuable time and expertise commenting?
I never said that I felt that I was wasting my time by commenting and indeed I do not feel that way.

I love DIY and I'd love to hear you had fun messing around.
Like I said you start where you start and thus everyone starts at their own beginning.

I just felt it was disingenuous and unwarranted to try reprimand @alex-z , his comments were well informed and not over any sort etiquette line that I can see. Maybe he was saying what you did not want to hear but this is an open forum on a highly technical website so it stand to reason that some posters will be pointing out what a big job fixing these speakers to a high technical standard would be. Now "f"ing around with it all and having fun is not dependent on the final product being technically good.

Have a blast and line those cabinets with the 3-layer stuff I linked. You might actually be shocked at how much that stuff deadens live cabs. The pollyfill wont do anything for cab resonances. That not what it is for.

Anyway have a ton of fun and take care in your retirement.
 
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richardbruce

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I never said that I felt that I was wasting my time by commenting and indeed I do not feel that way.

I love DIY and I'd love to hear you had fun messing around.
Like I said you start where you start and thus everyone starts at their own beginning.

I just felt it was disingenuous and unwarranted to try reprimand @alex-z , his comments were well informed and not over any sort etiquette line that I can see. Maybe he was saying what you did not want to hear but this is an open forum on a highly technical website so it stand to reason that some posters will be pointing out what a big job fixing these speakers to a high technical standard would be. Now "f"ing around with it all and having fun is not dependent on the final product being technically good.

Have a blast and line those cabinets with the 3-layer stuff I linked. You might actually be shocked at how much that stuff deadens live cabs. The pollyfill wont do anything for cab resonances. That not what it is for.

Anyway have a ton of fun and take care in your retirement.
I've quoted Alex's remarks that I consider unwelcoming and rude - especially towards a new member. I don't care how RIGHT he might be technically. I expect more from a "senior" member of ANY group that wants to make new members feel welcome, no matter their speaker-building or modifying experience/expertise.

On the other hand, No. 5 was quite friendly and helpful. He never judged nor tried to discourage me. Nothing but helpful. I welcome his continued assistance. He's #1 in my book.
 

No. 5

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You need a mic that is at least mostly accurate, and an impedance sweeper. No way around spending that $80 unfortunately.

Is a UMIK-1 suitable for crossover design? Since it’s a single channel interface there’s no electrical way to get a timing reference. REW can provide an acoustic timing reference, and there's ways to add delay to the IR, but I don't know how comparable those methods are to a dual channel measurement when it comes to this. I would be curious to see a direct comparison, though.
Then to do the measurements you need a reflection free area, and a measurement stand. Two key requirements, the speaker is far away from hard surfaces, and neither is the mic body, it should be on the end of a boom arm.


With good quality measurements, you can export the data into VituixCAD, design a crossover, and be ready to buy parts and solder.
@richardbruce this is something to give some thought to if you are planning on making some acoustic measurements (and I highly recommend that you do). That link has some excellent step by step directions, however, for what you want to do here, I really don't see a need for you to get into getting nearfield bass part of it, and just to keep things simple, I figure we can skip doing a polar response.

For acoustical measurements, you'll need four, one of the speaker as is (to have a reference to compare), and one for each of the drivers in the cabinet. The speaker and microphone will need to be "locked down" for these measurements because you need to know what the raw response of each driver is at a single point in space along the listening axis in order to design the new crossover. You will also need to use a loopback from one channel of your USB interface's headphone output into its number 2 input channel to get the relative delay between each driver. It would be good to document the axis used for the measurements and the distance between microphone and front of the speaker (around 40" should be good) since you'll probably want to measure the results after you install the new crossover.

And as mentioned, you'll need impedance measurements for each of the three drivers. Otherwise it'll be completely impossible to get anywhere with this project.

As far as the cabinet, I would see what you can get with a new crossover first before considering what to do about the any cabinet resonances. Similarly with replacing any drivers, I'd measure and see what you have before expending any money on new parts. But that's just me.

For what it's worth, I quite like engineering challenges like this. They get a person thinking creatively, and can be remarkable learning experiences.
 

alex-z

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Is a UMIK-1 suitable for crossover design? Since it’s a single channel interface there’s no electrical way to get a timing reference. REW can provide an acoustic timing reference, and there's ways to add delay to the IR, but I don't know how comparable those methods are to a dual channel measurement when it comes to this. I would be curious to see a direct comparison, though.

It works fine for crossover design. It just requires more setup time, because you need to manually adjust the impulse response gating, rather then relying on the loopback interface you would get with 2 channel setup. In general, get a 2 channel XLR setup if budget allows.

The default UMIK-1 config has a random incidence response, which means won't track accurately with a free-field calibrated setup, like the Klippel NFS. This is true of most microphones. However, Cross Spectrum sells a free-field calibrated version for slightly more. They also sell a calibrated Dayton UMM6, or you can ship them a mic of your choosing and they will calibrate it.

And for those people on a tight budget, you can edit the default correction file, delete all the values above 7000Hz, and it will improve the accuracy a fair amount. I wouldn't call it accurate enough for commercial designs, but enough for intermediate DIY work.



Another part of doing the free-field response correctly is making sure your measurement stand and microphone stand both have no immediate reflections. Picture D in the following link is an example, the microphone is mounted on a long boom arm. You will notice a cleaner impulse response when the microphone is truly free-field.

 

No. 5

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It works fine for crossover design. It just requires more setup time, because you need to manually adjust the impulse response gating, rather then relying on the loopback interface you would get with 2 channel setup. In general, get a 2 channel XLR setup if budget allows.
Interesting that it can be done, thanks for clarifying. I don't have a USB mic, so it's something that I've never looked into, but that's something that I should play around with.
 
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richardbruce

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I finally completed my NS-6490 improvement project. Installed the crossovers, replaced the mids, and added Acousta-Stuff polyfill. And since I don't have the knowledge and sophisticated equipment suggested here, I decided to do just the most basic testing available. I created a test CD with tones varying from 20hz to 20khz, then played that thru the speakers, using my JVC RX-805VTN receiver and JVC XLM-409TN CD player/changer. I recorded the results in stereo using Audacity and 2 identical Shure SM-58 microphones. The microphones were placed equidistant to the speakers, and either centered on the loudspeakers for sweeps or focused on the mid speakers, which I was most interested in. The right channel shows the original speaker and "crossover", while the left shows the changes as I replaced first the crossover, then the mid speaker. Here are the results. To my eye (and ear), the new crossover and midrange speaker provided a much smoother mid and somewhat better highs. I can't hear about 10kHz anyway.
 

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No. 5

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Congratulations on your project! It sounds like you got the result that you were looking for.

Can you upload the recordings of the sweeps? It might be possible to load them into analysis software and get some kind of a look at the results that way.
 
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richardbruce

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It looks like I can export the audio file from Audacity. What file format would be best/uploadable here?
 

No. 5

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It looks like I can export the audio file from Audacity. What file format would be best/uploadable here?
A .wav file is fine for the data, it should only be a few seconds long. I don't know if there's any restrictions on file types here.
 
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richardbruce

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A .wav file is fine for the data, it should only be a few seconds long. I don't know if there's any restrictions on file types here.
Here's the smaller 16-bit file. It's about 30 seconds long. Only compatible file format is .zip
 

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No. 5

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Thanks for uploading that. Unfortunately, I was unable to get any useful data after loading it into my analysis software. Maybe if I had the original file of the sweep too, but at this point, it's probably best to just enjoy what you have accomplished rather than spending more time trying to get measurements back and forth.

Glad you are enjoying your creation!
 
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