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Joined: Sep 2020
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meghdad Offline OP
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So I am inclined to add a pair of tweeters to go with the internal speakers of the Korg C1, in an attempt to improve the high-freq sound, and diminish the relative dullness.
I'll learn a thing or two and it'd hopefully be fun as well.

What should I take into account regarding the tweeter specs? What shape, what power, what sensitivity etc? Also where to attach them? The DP has a ~90 degree opening key cover which when is opened, faces towards my head and it has gaps underneath which allows wires to be crossed in, as well as a space or depth, as deep as ~3cm which could allow tweeters to be attached to beneath the key cover (thus facing me while open) without getting in the way of it while closed.

Here is an image of the DP with the key cover open.

I'd like to conceal them in a way that doesn't mess up with the aesthetics too much, like the internal speakers, which are concealed using a wooden-fabric cover. But that could an afterthought so long as it doesn't affect the choice of tweeter depth.

As for the crossover circuit, I've found this guide as a starting point.

P.S The max power is limited to 50w.
P.S 2: Its big brother , the G1 air, has tweeters on top, which does not face the player.

Last edited by meghdad; 09/12/21 04:39 AM. Reason: Added P.S
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meghdad Offline OP
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Well I just found out there are ready-made crossover circuits. I've found this one.

Specification

3Way audio crossover
6dB/oct Atenation slope
cutoff frequency @4ohm
Woofer : Full
Mid : 600Hz-5KHz
Tweeter : 2Khz
Dimention : 53*45*20

Does it support my use case?
It supports 100w, which is appropriate for my case (50w). What about resistance? My amp's resistance is 6ohms and the internal speakers are 8ohms. I'd need tweeters which are greater than 8ohm right?

Oh and it has a 2nd order filter.

Last edited by meghdad; 09/12/21 05:33 AM. Reason: Added last line
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I wouldn't hack a custom modification. The hack will likely not sound good.

Instead I'd buy speakers or monitors. These will sound much better.

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meghdad Offline OP
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As you may know, I'm on a tight budget so I can't afford spending money on monitors.

As for speakers, again as you may know, I have a couple of bookshelf speakers that sound great. However Id like to try this approach and see what can be achieved, at least for the heck of it. Besides, the DP's internal speakers are located in such a way that the sound isn't sent directly to my ears which would cause ear damage in the long run usage. That and, they look good aesthetically. :-)

Is it really not possible to achieve sound as good as factory-made ones akin to the DP's big brother, G1 Air? What parameters could be different other than calculations (which can be figured out)? The components like capacitors etc?

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Originally Posted by meghdad
As you may know, I'm on a tight budget so I can't afford spending money on monitors.

As for speakers, again as you may know, I have a couple of bookshelf speakers that sound great. However Id like to try this approach and see what can be achieved, at least for the heck of it. Besides, the DP's internal speakers are located in such a way that the sound isn't sent directly to my ears which would cause ear damage in the long run usage. That and, they look good aesthetically. :-)

Is it really not possible to achieve sound as good as factory-made ones akin to the DP's big brother, G1 Air? What parameters could be different other than calculations (which can be figured out)? The components like capacitors etc?


Keep in mind the way x-overs work:

each driver - woofer/tweeter etc. connects to its own x-over singly.

get a 8 ohm tweeter to use with a 8 ohm woofer/ 2 way x-over x-over frequency ~2.5 kHz

If your tweeter is too loud compared to the woofer, an in-line resister between the amp and tweeter x-over would be be added to attenuate the tweeters level

Also, the tweeter directed at the ear with the woofer pointing somewhere else will probably be imbalanced and annoying.

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@emenelton: I think you're spot on. There's much to know and do.
If someone lacks the knowledge and ability to construct homemade speakers, I think the result is likely to be poor.

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I will give a simple suggestion that I think would be very practical and efficient.

If you just add a tweeter to your piano by plugging a cable into the drivers' posts of your instrument with a capacitor of 2.2 welded on the positive cable that will plug into the tweeter it would be simply solving your problem.

The tweeter you would put where you want, and only have a cable that would be plugged into the positive and negative posts of your driver coming out of the piano.

So i wouldn't change anything, i wouldn't worry about crossover or impedance.

As a suggestion to tweeter something similar to teac TE-T20 would be enough.

Hugs to all.

Rajane.


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I think the translator got a little complicated, I'll repeat.
Just plug a cable into the negative and positive speaker pole of your piano and connect this cable to your tweeter with a capacitor of 2.2 on the positive pole of this cable.
Hugs to all.
Rajane.


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Originally Posted by meghdad
Well I just found out there are ready-made crossover circuits. I've found this one.

Specification

3Way audio crossover
6dB/oct Atenation slope
cutoff frequency @4ohm
Woofer : Full
Mid : 600Hz-5KHz
Tweeter : 2Khz
Dimention : 53*45*20

Does it support my use case?
It supports 100w, which is appropriate for my case (50w). What about resistance? My amp's resistance is 6ohms and the internal speakers are 8ohms. I'd need tweeters which are greater than 8ohm right?

Oh and it has a 2nd order filter.

That's overkill if you're adding a rather random tweeter. Building decent speakers is serious engineering. You may find that the crossover in cheapo stereos often comprises a single capacitor for the tweeter. But these are often not a good match for a DP, because a DP is a challenging sound source akin to a function generator, good for exposing speaker weaknesses ;(
Add-on tweeter are often available for car speakers. But no idea if you can find one with matching impedance and sensitivity.

> I'll learn a thing or two

If you want to learn a thing or two with such project, you need proper gear to measure the frequency response.

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Originally Posted by RAJANE
I think the translator got a little complicated, I'll repeat.
Just plug a cable into the negative and positive speaker pole of your piano and connect this cable to your tweeter with a capacitor of 2.2 on the positive pole of this cable.
Hugs to all.
Rajane.

+1.

I assume that you meant "2.2 uFd" (microFarads), which sounds reasonable for a high cutoff frequency. (A larger value capacitor would give a lower cutoff frequency.)

When my father was getting old, and losing his high-frequency hearing, he added a small horn tweeter to his AM/FM table radio. Took the power feed from its loudspeaker, and put a capacitor in series with the tweeter as a primitive crossover.

.. . He loved the sound.

The rest of the family, when we visited, found it really screechy. The horn tweeter was quite efficient, and upset the bass/treble balance.

It would probably be OK with a lower-efficiency tweeter -- a dome tweeter, for example.


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That's exactly what it was.

As for the tweeter being of the dome of the seed or is not at the discretion of the taste of each.

I particularly find the most velvety seed dome tweeter with a sharper refinement.

I fully agree with your suggestion by this tweeter template as being a more right choice.

I cited this Teac only as a low cost reference to test this possible possibility.

Hugs to all.

Rajane.

Last edited by RAJANE; 09/12/21 04:50 PM.

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meghdad Offline OP
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Originally Posted by emenelton
Originally Posted by meghdad
As you may know, I'm on a tight budget so I can't afford spending money on monitors.

As for speakers, again as you may know, I have a couple of bookshelf speakers that sound great. However Id like to try this approach and see what can be achieved, at least for the heck of it. Besides, the DP's internal speakers are located in such a way that the sound isn't sent directly to my ears which would cause ear damage in the long run usage. That and, they look good aesthetically. :-)

Is it really not possible to achieve sound as good as factory-made ones akin to the DP's big brother, G1 Air? What parameters could be different other than calculations (which can be figured out)? The components like capacitors etc?


Keep in mind the way x-overs work:

each driver - woofer/tweeter etc. connects to its own x-over singly.

get a 8 ohm tweeter to use with a 8 ohm woofer/ 2 way x-over x-over frequency ~2.5 kHz

If your tweeter is too loud compared to the woofer, an in-line resister between the amp and tweeter x-over would be be added to attenuate the tweeters level

Also, the tweeter directed at the ear with the woofer pointing somewhere else will probably be imbalanced and annoying.

Thanks for the tips. I'll keep them in mind even though I'm inclined to go with the aftermarket car tweeter options, as a jump-start.
As for your last point, the G1 Air is setup exactly like that, with the woofers and tweeters not pointing at ears. That's important as you noted, and I should take this one rather seriously and if I can't find a good placement for the tweeters, I would give up.
Now I should ponder if there's at all any suitable placement on the DP for tweeters. Look at the G1's tweeter setup:
[Linked Image]
It's directed upwards, which then the sound reaches ears indirectly. The C1 does not have such a space onboard, the control unit is located where the G1's tweeters are.
The closest setup to that of G1's would be to place the tweeters on top middle section, which then wouldn't provide good stereo soundscape, being parallel to my ears. Another downside would be that I the sheet placement location would be wasted. So such a setup doesn't seem to be possible with the C1.

At the end of the day, I may come arrive at a conclusion similar to what macmacmac suggested. We'll see.

Originally Posted by macmacmac
If someone lacks the knowledge and ability to construct homemade speakers, I think the result is likely to be poor.
First of all thanks for the easy-to-remember nickname. haha

Other than the point made above, I think I'm gonna seek the opinion of car tweeter aftermarket sellers and buy one unit from them so as to reduce the chance of messup, as far as tweeter and crossover specs are concerned.


@RAJANE: Are you sure it would work well without a crossover? Do you have experience with such stuff? Here's a reference to my current setup, in case that might change your opinion:
http://forum.pianoworld.com/ubbthre...xternal-amplifier-to-the-dp-speaker.html

@_sem_: What kind of gear may I ask?
Also good call on the aftermarket car tweeters, as they can be found in abundance over here. I'm gonna seek their opinion and see what options do I have for ready-made boxes.

And I still have the option of using my bookshelf speakers if this approach goes nowhere.

Thank you all.

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> What kind of gear may I ask?

A good microphone, a signal generator, hardware and/or software to draw frequency and phase response...

> Look at the G1's tweeter setup:

I don't think the speaker placement in the G1 is great.
I assume you know how monitor speakers are mostly placed.
You can try attaching tweeters to the underside of the keyboard cover, if there is enough space for them and their cables. Of course this may not be optimal because they'd be closer than the main speakers, but that wouldn't be the only suboptimal thing with the setup.
You could also put them on brackets further away, at a distance comparable to the main speakers, but it might look a little bit ugly smile
You could also consider mounting the speaker box above the piano (if it doesn't sound dull inherently, not just due to the placement).

> And I still have the option of using my bookshelf speakers if this approach goes nowhere.

I guess this is a better line of thought, if they're any good.

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@RAJANE: Are you sure it would work well without a crossover? Do you have experience with such stuff?

Believe me, it works, and it won't be harmful to your piano.

I have Yamaha NS-777 towers that I added an external tweeter this way more than a decade ago, my Parasound amplifier has always worked with this artificio in the towers, in fact if it is adding another way to your system after the original crossover.

The capacitor is just cutting the frequencies harmful to the tweeter, in fact it is acting as just another crossover passive just to protect your twitter.

This artof using a capacitor acting as a crossover for high frequency pathways is very common in low-cost speakers, this is a low-cost solution that has been used by industry for decades, not a solution of mine.

Hugs to all.

Rajane.


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Based on the information sem has given it's clear that 2.2 uF is not the right cap. It's too small for most cases.

Regardless ... you'll first need to know the cutoff frequency and tweeter impedance. Then get your answer from the links sem has offered.

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Can you find some used powered computer speakers for free or super cheap (at a recycling place, for example)? Alternatively, I bet there are some great consumer electronic techs in your town who may have some refurbished computer speakers that are better than new.

You would want to test the speakers work and don't buzz (see counterfeit capacitor problem that destroyed a lot of consumer electronics built between roughly 2000-2010).

If the speakers have a problem, replacement capacitors can be really easy and cheap. But there is a possibility leakage destroyed other components so is not really fixable. . .

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@RAJANE: Are you sure it would work well without a crossover? Do you have experience with such stuff?

Believe me, it works, and it won't be harmful to your piano.

I have Yamaha NS-777 towers that I added an external tweeter this way more than a decade ago, my Parasound amplifier has always worked with this artificio in the towers, in fact if it is adding another way to your system after the original crossover.

The capacitor is just cutting the frequencies harmful to the tweeter, in fact it is acting as just another crossover passive just to protect your twitter.

This is not correct. If you combine an 8 ohm woofer or full range driver with an 8 ohm tweeter in parallel with no crossovers, you will have a 4 ohm circuit. (Connecting them in series will introduce phasing issues).

If your amp is 4 ohm stable, that will work ok as long as the tweeter is not damaged by low frequency content.

The poster wanting to do this posted that the amp in the piano is rated for 6 ohms. I'm not sure how he got that spec, but if the amp is not rated for 4 ohms, presenting a 4 ohm load may increase the current draw in the amp, overspec'ing some components in the amp, causing them to overheat and fail. It theoretically could even be a fire hazard.

When you have a low pass filter on the woofer and high pass filter on the tweeter, the two are only producing frequencies in common near the crossover frequency, and at a low level there. There will not be a frequency where both are fully active. At a given frequency, the resistance will then remain close to 8 ohms so that the overall impedance curve over the frequency range will stay close to 8 ohms.

Part of the engineering is designing the combined circuit (full range driver, tweeter, crossover circuit elements) to have an impedance in the range supported by the amp.

If the poster does not have the budget for some powered monitors, I hope he has the budget to repair or replace the piano, because that may be where this is headed.

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In other words ... if you don't know what you're doing, don't do it. Right?

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I've always known that the "resistance", or nominal impedance, of a speaker is varyable.

And this "resistance" varies according to the frequency of the electric current circulating, and that is precisely why it is called impedance (and not simply resistance).

And I learned that in the case of a single tweeter and its capacitor attached to a system the resistance offered due to the frequency to this circuit is so small that it offers no change to impedance's marriage security.

As in life science can suddenly be altered by new theories and discoveries we are always in a continuous learning.

I suggest to the colleague before attaching a new tweeter to your piano consult a technician of your confidence.

In several cases where I added this way a tweeter in some system never huove anything wrong, let alone some fire or malfunction of the device.

But caution is never too much, before trying in this way suggested by me consult a specialized assistance to evaluate to assess the safety of this procedure.

Hugs to all.

Rajane.


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