opinions on wiring tweeters differently

The way I have my car set up right now, I'm running an Eclipse 3122 amp powering a set of 7" door speakers and 3/4" dome tweeters, also on the door panel. They're all run through a set of custom crossovers I built for them. Originally the tweeters were severely out of balance with the woofers, (too loud) so I put in a variable attenuator so I could control the tweeter volume to my liking.

The head unit's rear channels provide the power for the small 3.5" speakers in each headrest, and the front channels are unused because I'm using the amp in place of them. But I was thinking, if the tweeters are clearly a little overpowered since I have the attenuator hooked into them that's essentially bleeding off power, why not just wire them into the head unit's front channels? They'd be getting the same signal as the woofers, just from a different amplifier source, and the lower amount of power would just mean I wouldn't have to attenuate them as much. So I'd be increasing the power available to the whole system by utilizing the HU's front channels, and I'd be using it more efficiently because I wouldn't need to attenuate the tweeters as much. Anything wrong with that idea?

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'96 Mazda Miata

The tweeters sound too loud because they are likely more efficient than the woofers, and because they are probably closer to your ears.  It's not because they are getting too much power.  Your pad solution is the more correct one and the normal one.

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Yes, but couldn't I get better performance out of everything by splitting up the work on the front channel between the amp and the HU? Needing the L-pad in there just tells me that the HU probably has plenty of power to run just the tweeters to my liking.

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'96 Mazda Miata

Sad, little man wrote:

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Yes, but couldn't I get better performance out of everything by splitting up the work on the front channel between the amp and the HU? Needing the L-pad in there just tells me that the HU probably has plenty of power to run just the tweeters to my liking.

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Not usually, no.

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Ok, so against that advice I got curious and re-wired the tweets over to the head unit. Sounds good, but for some reason the treble seems harsh at higher volumes. I think it could be attributed to one of two things.

I think that either my tweeters are clipping at levels where the mids are still clean due to the tweets being hooked to the less powerful head unit amplifier. Or, something else I just came up with, is perhaps that due to the gain settings on the amplifier, the tweeter volume actually goes up at a steeper slope than the mids. ie let's say each click of the volume on the head unit increases the mids by 'X'db due to its gain setting and each click increases the tweets by 'X'+1db due to the head unit's own volume scale, so what sounds good at a moderate volume gets washed out by treble at higher volumes, and if I turn the tweets down with the L-pad, then I end up with too little treble at lower volumes.

The gain on the amplifier is already set to the maximum, so there's no way to try to match the volume slope of the tweets if that's the problem. And before you jump down my throat about gains, I did that due to the fact that the headrest speakers are normally too loud since they're so close to my head, so setting the front speaker gain up high allows me to not use as much fade forward on the head unit to balance the sound. The gain may be high, but it's not like I'm also cranking the head unit and pushing the amp into clipping.

Another benefit is it allows the amp to get as much signal as possible at as low a volume as possible, so the head unit's front channels driving the tweets have as low a volume as possible in relation to the mids so I can dial in as little attenuation as possible to quiet them down and use what power the head unit has most efficiently. I guess to put it simply I'm trying to keep the head unit's channels as quiet as possible as opposed to the amp as loud as possible.

So is there a good way to determine if my tweets are clipping at a given volume? I've found it's harder to hear than clipping from mids and bass. I really wish I had an oscilloscope to set all this with. Perhaps I should just re-wire everything to the amp, but I really believe that if there's untapped power in the head unit, it's beneficial to try to bi-amp the tweeters with it and have the most possible available power in the system.

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'96 Mazda Miata

Most likely it is the HU amp giving out. There is only 12v available for that - no switching power supply.

12X12=144(/4)=36(/2)=18w peak to feed the tweeters. Not enough in my opinion...

That is not to say that is the ONLY issue. Your second mentioned issue could be very much coming into play. The linearity between the HU internal amp and RCA outputs is also probably not matching up.

It is entirely possible that the running everything off the amp, using fixed (carbon, not wire) resistors for attenuation, might be your best bet.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

What's the advantage of fixed resistors? I mean, it's possible that I could get the correct resistance values by adjusting the pad and then wiring in the appropriate resistors in its place.

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'96 Mazda Miata

Your theory about gain setting is dead wrong.  You are probably clipping your amp without detecting it.  Have you scoped it?  If you need to attenuate your headrest speakers (which I would remove if I was designing your system as they will only do harm to your overall performance) then use your L-pads on THEM.

You need to pad your tweeters so they match the sensitivity of your woofers.  Using a L-pad is a cheap and dirty way to do it, sure, but it will always (always) add noise and shift the Xover point since L-pads are generally inductive loads.  You should calculate the amount of pad needed and use a fixed voltage divider built from non-inductive resisters.  Are you still using those overly complex 4th order crossovers you posted a while back?  They could be part of the problem as well as they simply contain way too many elements to be reliable unless you used VERY high quality (read: expensive) parts to build them.

Give me the makes/models of the two speakers you are trying to use as your home-made component set and describe their relative mounting positions, and I'll design a crossover network for you to try.

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Yeah, the crossover plans (well, values, I went ahead and used multiple caps in each section to match the values exactly) and speaker selection was by someone on another board who installed a similar system into his car. I did use audio quality 18ga air core inductors, non-inductive resistors, and electrolytic capacitors good to 200W in the crossovers, they should be reliable. The speakers I'm running in the doors are these as recommended.

However, the company now makes a 4ohm version of the same speaker with slight differences to make it more suited to car audio, and if I build a whole new set of crossovers, I'd build them for the 4ohm version as this would make things a lot more efficient.

The tweeters are a pair of these.

I found a good interior picture of a car identical to mine online, you can see the tweeters mounted up high on the door panel, and the woofers in the normal spot. My speakers are still in the factory locations.


If you'd like to design some crossovers for these, by all means... I'm probably going to switch my door woofers to that 4ohm speaker after a while, and that'll mean I'll need to have new crossovers anyway.

As far as the headrest speakers, I want to keep those, because they are a godsend in a convertible, especially at highway speeds. They're really the only way to hear anything with all the added noise.

Thanks again for all the help with everything. I have a lot of mechanical knowledge dealing with cars, but the electrical side, especially when getting into stuff as precise as audio, is still a little foggy.

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'96 Mazda Miata

OK, first off just looking at the two drivers you've chosen, they are a very bad match and that could be part of your frustration.  I can't put together a good crossover for those two that I would recommend to anyone.  What is your crossover frequency?  I would not recommend crossing that Dayton woofer any higher than about 1500Hz, and the little Dayton tweeter is not much good below 3000Hz.  So you have a big huge natural hole in the response, right in a critical frequency band for music for speech, and forcing the tweeter to play too low will eventually destroy it and make it sound very ragged while it dies.  A much better tweeter to use with those Daytom woofers is something like THIS.  You have to pay a bit more than $5 to get a tweeter that can reach into the upper midrange like that Dayton woofer requires.  Or get a better woofer that can be crossed up around 3KHz, maybe like THIS one (which I use in my home.)

Also you say you are using electrolytic caps in the crossover.  This is generally a no-no unless you are using very expensive bypass caps, and even then electrolytics can cause all sorts of sonic issues not the least of which is high frequency harshness and distortion and a very thin, shrill sound.  You need to use good crossover caps, metalized poly at the least, like THESE.  A good passive crossover generally will cost more to build than the drivers it is controlling.

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OW. BUT, you did come asking for advice. DYohn is right, again, and while the Dayton drivers you have choses are decent drivers, they are not really the best choice for a two-way system in a car. If you were to implement a three-way system, you could certainly improve your standing from here, CONSIDERABLY.

DYohn mentions the hole in the frequency response. Again, he's right. A three-way implementation would fix that. The sensitivity differences between youe woofer and tweeter is almost 6dB, a HUGE effciency issue to overcome.

The Adire 6.8 is a FANTASTIC woofer, if a bit deep. They are in my car, running 50-200Hz at 36dB on both ends, running into a 4 inch Vifa (proprietary, acquired from Harman) midrange up to 3500Hz (at 48dB on both ends), into the JL VR Evolution series silk dome tweeter at 3500 and up (at 48dB). This is all tri-amped, with signal processing, TD and crossover functions all being provided by an AltoMobile UCSPro. It takes MUCH effort to get it sounding right, as you can tell.

Ouch... I also didn't know you were using electrolytics on your system... Yeah, again, DYohn hit on it. Electrolytics are VERY bad in audio circuits. They are fine for low frequency portions of crossovers, but I'd never implement them ANYPLACE they would be seeing over about 500Hz... and never EVER in high pass portions, where the audio signal passes through them; they are FAR too lossy to be used in even moderately high frequency stuff.

Also, one last thing... (and this applies especially right now, until you get your driver complement decided) that positioning in that picture will ONLY serve to make your frequency response hole worse. The tweeter should never be more than one woofer diameter away from the woofer. (1/2 a woofer diameter is even better.) I would never place those two drivers that far apart in a car. In a home application, where you can be right on axis, it would pnly be SLIGHTLY better, but in the car...? Blech. Major suck-out potential.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

what is your reasoning for building your own crossovers and such? if you are lacking the experience and electrical skills, I would much rather pay for a properly engineered crossover.

You could study it and build your own eventually

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I think you're interchanging the terms building and designing crossovers, but they're two different things. Like I said, the actual values for the crossover I got from someone who had designed them for himself, I just took the values and built a set of crossovers to that spec. I mean, don't get me wrong, I'm good with soldering and everything involved with building the crossover, I just don't fully understand everything that goes into them, that's why I didn't try to design my own.

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'96 Mazda Miata

Which is why I tried to encourage you (sadly, you posted after you had already built the crossovers) to simplify, simplify, simplify, in your initial thread on this subject.  Some research would have pointed you to a better direction to crossover design instead of just copying one poster's design.

There are things that are wrong with your component selection as well.  DYohn (et.al.) spelled that out above.  With changes comes more changes.  Oy vey!

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Ok, ok. So whenever I decide I want to fork over more money to do things over, how about I go with this tweeter (bigggest thing I could likely fit i nthe stock location, and goes to 2,000hz) with the afformentioned 4ohm dayton woofer. Both drivers are 4ohms, and they're within 2db of each other in efficiency. Then maybe just stick to a second or third order x-over at 2100hz so according to the published specs each driver stays 100hz within in its range. And then wire up a 2db (or would I want more since it's higher up on the door) L-pad for the tweets so each has about 91db efficiency. About the tweeter placement... Maybe it would be better closer to the woofer, but I really don't want to start hacking up the interior. I also just can't justify or bother with designing a complex three way system, it's just overkill for what I'm after. Do you guys think this site would be good for getting the specs for the x-overs and L-pad?

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'96 Mazda Miata

That tweeter is a much better match for the Dayton woofer. Fs of 900Hz means you could go as low as 1800 if you needed to, with 2700Hz being "ideal" (3X fs.)   I suggest a 3rd order passive at about 2KHz (2100Hz is a good target.)  Mounted high in the doors like that I'd cut the tweeter output at least -3db below the woofer, so you'd need to pad for -5db (there is also a tweeter pad calculator on the site you linked.)  The crossover calculator site gives good average values.  No calculator is ever perfect, but it's a decent place to start.  If you want to model a bit more effectively, download the Passive Crossover Designer from the FRD Consortium (You will need Microsoft Excel to use the files.)  Be sure to use at least 10-watt non-inductive resisters for your pads, and good quality polypropylene caps and air-core inductors at least 16-gauge for your crossover.  THROW AWAY your fist full of electrolytic caps (or save them for a future amplifier build!)

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So... what did you end up doing?

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Nothing yet. I went out of town just after I made the last post. Due to budget and time constraints I think I'm going to keep the current system until my school semester is out in early May. The current system may not be great, but it's still miles ahead of my old setup of running factory (albeit premium) speakers off of the head unit. But at least now I have a better plan for doing things, and a lot of the wiring is already in place.

Melodramatic I know, but changing out the speakers is huge amounts of work. To get those woofers in place without cutting up the interior I had to put them into one of the door access holes and fish them along though the inside of the door to mount to the back of the hole where speakers would normally go. The tweets will also be pushing the limits of what will fit between the door and the panel.

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'96 Mazda Miata

...So taking a good hard look at what components I'll actually be buying when it comes time to change things again, would it be a bad idea to just go with a second order filter at 2100hz with those drivers? I only say this because A) It'd be cheaper to build B) It'd be much easier to fit everything into a plastic electronics box C) I'm not sure how to overcome the 270deg phase shift of a third order filter and D) In a second order the low pass only goes through one inductor, making the power lost in the crossovers less, and I'm really looking for ways to improve the efficiency of the system.

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'96 Mazda Miata

Not sure which drivers you ended up using... and also not sure why you think you'll need to replace the woofers in your doors.  In any case, choose a tweeter with an Fs at 1000Hz or less and you can cross at 2100 with a 2nd order filter and be relatively safe.   Be sure to reverse the polarity of the tweeter in relation to the woofer with 2nd order.  As to your other comments, the phase shift in 3rd order topologies is not generally audible.  I use 3rd order electrical all the time in hi-fi and home theater applications, and it is required for a proper D'Apollito alignment.  Also, if you use inductors with sufficient gauge, there is no significant "power loss" in the woofer filter circuit.  Fractional decibels which will not effect your overall system efficiency.

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I'm going to go with those TB tweets I posted in a link. The 1" with what looks like a small rear chamber. Fs is 900hz. And if I go to the trouble of making new x-overs with better caps, I might as well drop the $60 and change my woofers to the 4ohm version of the ones I have and effectively double my power, and according to the sensitivity ratings, increase the volume by 3.4db. My system was designed before they made the 4ohm version of that same driver. It'll also match up the efficiency between the woofers and tweeters so I won't need to pad the tweeters as much.

Mainly my urge to go with a second order filter is to keep the size down. Those audio grade caps are a lot bigger than the electrolytics. Thinking in terms of packaging both the high and low pass filters in one box, if I start throwing together 3-4 of those caps and 3-4 15ga air core inductors along with a zobel and an L-pad, I'll need a pretty large box to fit everything, one on each side of the car, and space under the dash is limited.

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'96 Mazda Miata

No need to mount your crossovers in a box.  I use pieces of peg board and leave 'em open.

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