Speakers

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CN211276
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Re: Speakers

Unread post by CN211276 »

I have downloaded RTA analyser and think it gives a fair reflection of what I hear.
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Re: Speakers

Unread post by Noodledoodle »

68c3a412-6d71-40e2-8c44-0b52dabbc774.jpg
68c3a412-6d71-40e2-8c44-0b52dabbc774.jpg (82.45 KiB) Viewed 1843 times
Karatestu and Geoff,

Thanks again.

A lot to address here. First I will download those apps and try to get some actual data on the crossover frequencies - then I know what I am dealing with. I think I will address this first and then move onto your message (Karatestu).

But I can attach a pic of the crossover (it's an old photo so I can't get the resistor values immediately, and besides I need to to the above test first). It's from 1970 and the caps are original. I just got a tester in the post.

The baffle is around an inch wider than the bass driver.

The video I used was a rising tone starting at 20hz going up to 20,000. I stuck my head in the bass driver to check when I could hear it, and I covered the other drivers in heavy fabric. I went up and down a few times to be certain (ie I used a rising then a falling tone).

In a few days I will post an excel table

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Re: Speakers

Unread post by Geoff.R.G »

CN211276 wrote: Thu Apr 28, 2022 8:26 am I have downloaded RTA analyser and think it gives a fair reflection of what I hear.
I have the paid version and it is really useful for setting equalisation.

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Re: Speakers

Unread post by Noodledoodle »

Results:

I got both the signal and the measuring app. Removed all three drivers and tested each separately through via the crossover pictured above. All drivers were tested in the cabinet. The mic was on a stand and all done in a quiet room.

There's no need for an excel sheet.

The bass driver responds from 20 to around 5,000hz
The midrange driver kicks in suddenly are around 120hz and then stays audible until the high teens.

Given the restrictions of the free app and my big fingers I stopped here because there is clearly a problem. The crossover doesn't seem to work at all. I'm going to remove each capacitor and test it and I will post the outcome. I'll try to dig out the original wiring diagram for the crossover and post that too.

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Re: Speakers

Unread post by Noodledoodle »

Removed the caps tested, and they are all very close to what they are supposed to be.And ESR<0.5, Vloss 1% for all. Bit puzzled.

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Re: Speakers

Unread post by Geoff.R.G »

Noodledoodle wrote: Fri Apr 29, 2022 6:59 pm Results:

I got both the signal and the measuring app. Removed all three drivers and tested each separately through via the crossover pictured above. All drivers were tested in the cabinet. The mic was on a stand and all done in a quiet room.

There's no need for an excel sheet.

The bass driver responds from 20 to around 5,000hz
The midrange driver kicks in suddenly are around 120hz and then stays audible until the high teens.

Given the restrictions of the free app and my big fingers I stopped here because there is clearly a problem. The crossover doesn't seem to work at all. I'm going to remove each capacitor and test it and I will post the outcome. I'll try to dig out the original wiring diagram for the crossover and post that too.
Just because a driver responds from 20Hz to 5KHz doesn’t mean it produces a clean output, the bass driver cone may well be breaking up (flexing) well before 5KHz. Likewise the midrange driver above 5KHz, obviously you can’t see what the cones are doing but there will be good reasons why each drive unit is crossed over at specific frequencies.

Crossovers don’t actually cut off completely, a crossover at, say, 500Hz might mean there is still a signal to the bass driver at 2KHz, much attenuated but still there. At the same crossover the mid range driver may well get a signal at 120Hz but produce little or no usable output.

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Re: Speakers

Unread post by Noodledoodle »

The issue was that the rta app was reporting a high output across this broad range for both mid and bass drivers rather than the curve that one would expect.

But like I said the whole thing was a bit fraught given the 5 seconds of recording available. I couldn't rename the files either so that got messy. I'm looking for software that I can run on my pc so I can get decent plots. I found some freeware called TrueRTA which samples real time, but I can't figure how to record the output over time yet. If and when I'll put some plots up

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Re: Speakers

Unread post by Vinyl-ant »

Rew is a good option
For that program you need a usb mic, a umik 1 is recommended, or a measurement mic and an interface.
I have a behringer ecm8000 mic and a behringer um2 interface. Dont forget that you are measuring the in room response so you are not just seeing what the driver itself is doing
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Re: Speakers

Unread post by Noodledoodle »

I made a dumb error by not actually recording the different pitch increases, and then analysing them. I was trying to do it all together in 5 seconds. So I'm first going to take three recordings (one for each driver), and then analyse them. VA - good point, ill put the mic inside the other cabinet with some wadding in to reduce the other sounds. I'm going to try to get this working this week and actually post some plots!

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karatestu
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Re: Speakers

Unread post by karatestu »

karatestu wrote: Thu Jul 25, 2019 6:54 am
I am now definitely a big speaker guy. No going back to 6.5 " mid bass drivers now. There is a whole section of music missing.
That went well didn't it :lol:
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