DB651 tweeter mod

caraudio10

I installed db651 on my car, front and rear, but I find it that the tweeter is a bit loud for my hearing. So I reduce the car headunit treble control to zero but still its not enough for my taste.

How can I mod the tweeter so its not loud enough. Is this possible? Is there any other way to control the tweeter other than what I think?

If I am going to remove the tweeter, will it significantly change the impedance? or resistance vs its 4 ohms combined impedance?

[Deleted User]

Hello,
Welcome to Polk's forum. Most of the time reducing the treble adjustment on a car stereo is enough to set how high frequencies blend with the mid-range and bass. The only way to adjust the tweeter's output would be to place a series resistor before the tweeter's high pass filter (usually a blocking capacitor). This might be difficult on the DB651 and would probably void the warranty.
You might want to check with a local car audio shop to see if the addition of an EQ would be possible?
Just curious, did your car come with a factory "premier" sound system? It's possible what you're hearing is a function of a built-in frequency response set with the factory speakers. When the speakers are changed for new ones with a different frequency response the old EQ is too bright for the wider range speakers.
The impedance will not be significantly changed.
Regards, Ken

caraudio10

I have toyota highlander xle, toyota claims premium audio (non-jbl) version but EQ tweeter control almost does nothing ...guess not a "premium" sound after all. I think you are right about stock EQ tuning, its fine tuned to the crappy paper cone stock speakers. When I installed a good set of speakers, EQ have to be adjusted to the new speaker.

I am amazed on the bass response of db651. I can definitely feel the bass. Not like the bass of an amp'd speaker but its there.

I may have to experiment more. I will try what you have suggested to add a resistor in series with the tweeter.

What do you think is the resistor value for -3db or -6db on the tweeter?

My actual problem is hearing more "s" on vocal. Am I right in pointing tweeter volume control issue? or this is more of crossover issue?

caraudio10

I am thinking on replacing these speakers with component set with adjustable treble control.

[Deleted User]

I would begin using a 4 Ohm 5 Watt resistor, that should give a -3dB drop in tweeter level.

caraudio10

thank you. this is very helpful. I will wait for more weeks for the speaker to breakin.

caraudio10

As I am reading about speaker crossover, it came to my mind that the original 3.5" dash speaker on my car had 5.6uf or 6.5 uf capacitor. From crossover calculator on the net, at first order, with 4ohms impedance would cross at 7khz.

Now these make sense I think, toyota wired its dash and front speaker like a component speaker setup. 3.5" dash speaker act like a tweeter crossed at about 7k. While front door act as woofer.

Now that I use good and efficient speaker..I would think the tweeter is crossed maybe around 3 or 4khz it makes tuning harder from the head unit and my hearing perceived it as loud tweeter.

Do you think its worth a try to alter the crossover point on my polk db651 speaker to say 5 or 6Khz plus the resistor attenuation? And leave the high frequency handled by my db351 on dash.

It may defeat the purpose of the good speaker but at least I've got clear low, mid but not "too much" high. Actually the high is clear but its mixing with the vocal range.

Btw, I installed this speaker on my other car (honda) and I don't have problem with taming the high frequency since the head unit offer good control.

caraudio10

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westmassguy

You could also try an L-Pad, just to decrease the signal going to the tweeters. The Polks are most likely more efficient vs stock.

caraudio10

I just installed an lpad on my dash 3.5" speaker, I use series 1 ohm,then 10 ohms parallel. Sounds great and brings up the stage, like I am seating in front of a real concert stage. Music is clean and alive.

For my door 6.5 speaker I just need to lower down the tweeter and it should be the perfect audio. Soft clear,clean vocal with thump on lows.

caraudio10

With lpad on tweeter, what should be the values I can use?

Someone suggested a series 4 ohms resistor. From the internet, lpad is preferable over series resistor. So I might go on lpad mod.

I can calculate the resistor values if I know the tweeter nominal impedance. Anyone know this value?Tweeter only impedance of a coaxial db651.

westmassguy

Check the DCR. If it's at or under four ohms, it should be 4 ohm nominal impedance.
I would use a 15 watt stereo L-Pad : http://www.parts-express.com/speaker-l-pad-attenuator-15w-stereo-1-shaft-8-ohm--260-251
Solder the upper and lower tabs together. This will create an ad-hock 4 ohm, 30 watt L-Pad. Insert it temporarily in the harness feeding the tweeter. Adjust it till you find the correct tweeter level, remove it, measure the two resistances (series and shunt), then install fixed resistors of the same value.

caraudio10

Anyone from polk audio staff who can help me add an lpad to the tweeter in db651? I prefer data from polk audio staff since they have the schematic and technical spec of db651.
I am hesitant to add random component..as it may lead to failure in my headunit if impedance does not match.

Please polk audio staff help me. I wish you would provide -3db or -6db gain on the tweeter.

caraudio10

To polk audio staff....what is the impedance of db651 tweeter?

[Deleted User]

If you prefer to contact Polk directly you would need to telephone them on Tuesday at 1-800-377-7655 or send them an email to polkcs@polkaudio.com