kenwood center channel tweeter question

[hillbillydeluxe]

hello and greetings to all.this is my first post here and my first question. i replaced the center channel tweeter in my kenwood speaker and noticed that it had a simple 6th order 1 uf cap for a
7.2(8ohm nominal) tweet. my question is why would they place so high a xover on the tweeter?
and the mids had no xover at all just natural rolloff.the mids are 4 in cloth surrounds i don't think they can possibly go high enough to be full range.anyway i replaced the tweeter with a paper cone
panasonic 8 ohm i had lying around with a 2.2 uf cap and now the center sounds so much louder and brighter, just what i needed to keep up with the rest of the home theater system.

[johnastockman]

hello and greetings to all.this is my first post here and my first question. i replaced the center channel tweeter in my kenwood speaker and noticed that it had a simple 6th order 1 uf cap for a
7.2(8ohm nominal) tweet. my question is why would they place so high a xover on the tweeter?
and the mids had no xover at all just natural rolloff.the mids are 4 in cloth surrounds i don't think they can possibly go high enough to be full range.anyway i replaced the tweeter with a paper cone
panasonic 8 ohm i had lying around with a 2.2 uf cap and now the center sounds so much louder and brighter, just what i needed to keep up with the rest of the home theater system.

This is how OEM speaker companies do things. Since they have to be very aware of per-unit costs, they will scrimp on anything to keep their cost-of manufacture low. Simply because they make thousands and thousands, a few cents or a dollar here and there means they will be able to make a profit. It's about compromise with retail speakers, even at the high-end of the spectrum. I know, as I worked for an audio emporium in Olympia, Wa. for years. Offering everything from inexpensive house-brand speakers, up to 5-6 figure a pair units. OEM's will save and scrimp on the things that the average consumer doesn't understand and/or will never see. Like the XO you found in the Kenwood...or lack of a XO. It's a 6dB "slope", or a 1st order, usually with just one component. A cap on the tweeter, maybe a coil on the woofer. Definitely not adequate for a better SQ, but again, to maintain a realistic cost-of-manufacture so they can make $$. To be able to use a 1st order effectively, the woofer or mid must have a smooth roll-off to be able to run with just a coil...or nothing at all. Tweeters must be fairly robust and/or crossed high (like your speaker) to be able to handle a 6dB/1st oder XO. Those cone-type tweeters can handle a lower cross-point. Designs like the Large Advent used them, and the EPI 2-way speakers were famous for using just a 10uF cap on the tweeter. You could have issues with power handling, so if you hear any sort of distortion coming from the center, you'll have to lower it's level or turn the volume down a bit. These are all general rules-o-thumb, as there can be exceptions. If the increased volume from your tweeter is what you were after, then you are one of the few to get some success with an aftermarket drop-in replacement. A 4" mid driver can "possibly" play higher, that's why they used such a high cross-point on those, with the tweeter being used and protected by crossing at a higher frequency. Glad to hear you had a good result from the other tweeter.


John A.

[Fusion916]

Cheap speakers.

[hillbillydeluxe]

This is how OEM speaker companies do things. Since they have to be very aware of per-unit costs, they will scrimp on anything to keep their cost-of manufacture low. Simply because they make thousands and thousands, a few cents or a dollar here and there means they will be able to make a profit. It's about compromise with retail speakers, even at the high-end of the spectrum. I know, as I worked for an audio emporium in Olympia, Wa. for years. Offering everything from inexpensive house-brand speakers, up to 5-6 figure a pair units. OEM's will save and scrimp on the things that the average consumer doesn't understand and/or will never see. Like the XO you found in the Kenwood...or lack of a XO. It's a 6dB "slope", or a 1st order, usually with just one component. A cap on the tweeter, maybe a coil on the woofer. Definitely not adequate for a better SQ, but again, to maintain a realistic cost-of-manufacture so they can make $$. To be able to use a 1st order effectively, the woofer or mid must have a smooth roll-off to be able to run with just a coil...or nothing at all. Tweeters must be fairly robust and/or crossed high (like your speaker) to be able to handle a 6dB/1st oder XO. Those cone-type tweeters can handle a lower cross-point. Designs like the Large Advent used them, and the EPI 2-way speakers were famous for using just a 10uF cap on the tweeter. You could have issues with power handling, so if you hear any sort of distortion coming from the center, you'll have to lower it's level or turn the volume down a bit. These are all general rules-o-thumb, as there can be exceptions. If the increased volume from your tweeter is what you were after, then you are one of the few to get some success with an aftermarket drop-in replacement. A 4" mid driver can "possibly" play higher, that's why they used such a high cross-point on those, with the tweeter being used and protected by crossing at a higher frequency. Glad to hear you had a good result from the other tweeter.


John A.

the paper tweet came with the 2.2 cap so i figured just go with it.i understand going on the cheap but a 1st order slope at 15000 hz(+/- a few)is just to high. i don't think i would go that high for any tweeter.

[hillbillydeluxe]

thanks for the reply

[johnastockman]

the paper tweet came with the 2.2 cap so i figured just go with it.i understand going on the cheap but a 1st order slope at 15000 hz(+/- a few)is just to high. i don't think i would go that high for any tweeter.

Yeah, not that high. You could get a few of the inexpensive NPE caps and play around with it. I do not recommend any on-line calculator for XO-parts-calculations, but considering the low build quality on those (not intending to offend) you could try something around 4000Hz, maybe 5000Hz. Those 4" woofers should be able to do 4-5000Hz easy if they're a paper-cone type. Putting more money into the center might be wasting money, as the end-result SQ you can achieve will be low anyway. When you decide that you want something better, still on a budget, there are some terrific DIY designs available that will make that center sound like a transistor radio. I took a friend's cheap-brand Fidek (?) center channel speaker with 4" woofers and did this.

Original:




TB woofers, Audax tweeter, real XO:




End result:




I'd never heard of Fidek before, or since. But it was a huge improvement in clarity and SQ. Not saying you should do that with yours, though. It's usually better to start with a well-constructed cabinet to begin with. Curt C. has some very nice budget-oriented designs that can be used in a center-channel config. like the TriTrix for one, if/when you might want to upgrade.


John A.

[mdocod]

Hello hillbillydeluxe!

my question is why would they place so high a xover on the tweeter?
and the mids had no xover at all just natural rolloff.

You've more or less answered your own question here, however, there's a bit more to it...

the mids are 4 in cloth surrounds i don't think they can possibly go high enough to be full range

Lots of 4 inch drivers reach to 10K or beyond (albeit, with drawbacks, especially when used in multiples). A cloth surround is actually a common material for extending the response of a driver. I wouldn't be surprised at all if they reached up to 10K or beyond here. Allowing them to do so on the other hand, is, IMO, an undesirable trade-off, especially in a dual-woofer, horizontal center channel. (Too much opportunity for significant destructive coupling at different listening positions in the room)

noticed that it had a simple 1st order 1 uf cap for a
7.2(8ohm nominal) tweet

Quoted the above with correction applied.

The 1uF cap is doubling as both a way to bring down the level of the tweeter (saves the cost of having to use a resistor, and a higher value capacitor, or some other more costly configuration of components), while simultaneously giving it an electrical roll-off to protect it from low frequency. It's possible that the tweeters natural response tapers downward in the high frequency, and the 1uF cap may actually help flatten out it's response, providing a functional, albeit, far from perfect way to blend it with the woofers with the lowest component count and cost.

A 1uF cap does not automatically mean that the crossover is abnormally high either... In this particular case, yes, the natural overlap of these drivers with this component in place is probably pretty high, however, you should never assume that the crossover point in a design, correlates to the inverse of the crossover point that a textbook crossover calculation spits out. Imagine for a moment, a tweeter that has a naturally falling response from say, 5-20K hz, at a rate of say, ~4dB/octave on average. A low value capacitor might be used here to "correct" for this falling response, converting the falling response, to a 2dB/octave rising response instead, which might be a favourable correction for a speaker whose intended listening position is actually off axis a bit. In that case, the low value capacitor is just one piece of a working system, and does not define the crossover point in and of itself.

.anyway i replaced the tweeter with a paper cone
panasonic 8 ohm i had lying around with a 2.2 uf cap and now the center sounds so much louder and brighter, just what i needed to keep up with the rest of the home theater system.

It probably does sound louder, but I'd be willing to bet that the result of this change is a speaker that is further from a flat performance than it was originally. The 1uF capacitor, while cheap, was also probably selected as a best possible tradeoff to achieve a reasonable response with the speaker considered AS A WHOLE at a particular cost-to-build point. The modification you have made, with an undoubtedly louder tweeter, crossed lower, sounds better to you because it is louder through part of the passband, not because it is playing anything more accurately. This is a common problem with comparing speakers. Louder tends to sound pretty decent even at the expense of flatness, and furthermore, any-time you personally put work or thought into a build or a modification, your are inclined to prefer the results simply on the basis of being human, having an ego, and stroking it, whether intended or not (We're all guilty).

A 2" cone tweeter has a particular sound to it, that many people find desirable (particular distortion characteristics), and having one installed in a manner that would be very bright (undoubtedly it is in this case), creates a characteristic that, while on paper is flawed, in the real world, with real ears, may sound pleasing. A speaker with glaring inaccuracies will often "stand out," and that act of "standing out" is often misconstrued by consumers as a desirable behaviour. In this case, you've given your speakers "sparkle!"

-------------

Now, go back and ask yourself, if the kenwood center channel, had just had say, a single 5" "full-range" speaker right in the middle of it, no tweeter, just a single driver configuration. Would you, as a customer, be more or less likely to take the speaker seriously?

The truth is, a speaker built with the single 5" full range driver, would be less costly to make, and acoustically more accurate for more listening positions through the most critical frequency ranges, than the MTM Kenwood that is the topic of this thread. I'm not a proponent of full range speakers, in fact, they are well known a huge tradeoff, however, I am pointing out, that Kenwood knows, that because of misconceptions in the consumer industry, they are more apt to sell a worse sounding speaker, on the basis of it "looking" like it should sound good (symmetry, visible multi-way, etc), than on the basis of it actually sounding good and/or being accurate. In this particular case, they have made a multi-way, that is worse off acoustically than a single way could have been, and will sell more of them this way because of consumer ignorance.

Customers EXPECT to see a sideways MTM for a center channel because it's common. Ask anyone here who knows what they are doing, and you'll find out that from a sound engineering perspective, a horizontal MTM is a very poor configuration unless some of it's major problems are overcome through careful design choices. The industry started pumping these out for aesthetic reasons over acoustic reasons years ago, and now we are stuck with this as the standard.

Customers EXPECT to see a tweeter. You want to see that tweeter there, otherwise your brain will tell you that the speaker sounds muffled, or muddled, or thin, or weak up top, or not "airy" or "crisp" enough, lacking sparkle, whatever. In reality, the kenwood MTM up for considerations here, could probably forgo the tweeter for most ears, and in a double blind, wouldn't make a lick of difference, as few adults hear for crap above ~8-10K, and few musical programs include any significant content up there anyway.

Ok, I've rambled enough.

Regards,
Eric

[Whitneyville1]

Eric, your last graph may be why Hillbilly prefers the sound now in his room. A kick in the not-so-good programming high-end in a room that "eats" them a little. He's also taken some of the load off the 4"er's for the top-end which may reduce some break-up. (I don't know, I'm guessing based on the Dayton B652's for example.) Who knows, the center might test better than it did from the factory, especially in his living room or den or whatever.

[hillbillydeluxe]

thanks for clearing up the cap question.i know placebo effect has something to do with how the new tweet sounds,but i tend to like a less than flat sound coming from my speakers. i just can't get into speakers built that way.
i may eventually try a proven design for all my home theater speakers(except the sub)but all i have is 100 wattsx5 to play with. i have a older plate amp from P.E. that gets 150 watts@4 ohm.i want in your face volume (100-105 db)levels
. i don't see most flat audiophile type speakers reaching those levels with just 100 watts per speaker.

[mdocod]

...
. i don't see most flat audiophile type speakers reaching those levels with just 100 watts per speaker.

JUST 100W per speaker? hehe..

Most "audiophile" MTMs, TMMs and the like using ~6" or larger midbass units, should hit ~110dB@1M as a pair within a 100WPC limit.

Regards,
Eric

[fbov]

+1

100W is 20dB. To reach 105dB@2.83V, 1m, use a speaker with at least 85dB@2.83V, 1m sensitivity (105 - 20). One reason for the popularity of MTMs is the increased sensitivity of dual mid-woofs, fully 6dB of voltage sensitivity. Just remember that this region is called headroom; average levels in-room are more like 75dB, with 30dB of headroom for the peaks.

HAve fun,
Frank

[hillbillydeluxe]

i will aim for 90 db sensitivity @ 2.83v 1m. thanks again guys there is so much to learn and my head is swimming.
i got some studying to do if i want to even comprehend 1/10th of what is needed to make something more than just a "speaker".

[fbov]

That's why this is both a profession and a hobby - lots to learn but you don't need to be an expert to get satisfactory results.

HAve fun,
Frank

[johnastockman]

The sticky threads have a ton of info. Sometimes overwhelming for a person just starting out. One step at a time and don't be afraid to ask ?'s if you're stuck. Remember that the XO is the heart of the speaker. There is no easy way regarding the XO. I tried all the wrong ways before I came here many years ago. Wrong because the simple methods I tried never gave me something that was pleasant to listen to. No matter what drivers I used, from buy-outs, budget, or more expensive. Don't be tempted to use on-line calculators or ANY XO design method that only wants the driver's impedance and an arbitrary cross-frequency. The relevant parameters/specs needed for a proper XO design are variable, never a fixed number. Using a fixed number for one that constantly varies is an exercise in frustration and will get you no where. A great book for beginners is Ray Alden's "Speaker Building 201". This next recommendation and link is the best place to start and get a grasp on the wonderful & addicting world of DIY speaker-building. Paul has generously offered his designs and his knowledge about the common misconceptions about building your own speakers. Read everything under "Resources" at the right:

https://sites.google.com/site/undefinition/diy

I'm not a designer of XO's yet, but my background in a brick/mortar audio store for many years lends a certain perspective on DIY vs store-bought speakers. You can definitely get better overall SQ and a more enjoyable listening experience with a well-designed XO, better-than-store-bought-cabinet-construction DIY speakers than from the usual suspects of retail brands. Including both popular OEM's and the more esoteric/expensive ones. Help is always available throughout your own personal learning curve.



John A.

[hillbillydeluxe]

my biggest problem is the steep learning curve for PCD.very confusing very fast.i think my brain could only take so much before i get a migraine.i am going to read,read,read.

[fbov]

That's where a book on loudspeaker design would be helpful. Here's a search at PE for "speaker design books."
http://www.parts-express.com/wizards...Cat&srchCat=72

I've got just enough electronics background to be dangerous with PCD without these, but I've built mostly provens, and spent my lime learning about hearing, rooms, and acoustics so far (Toole, Everest). I'll probably buy LDC eventually, mainly because it's the thickest. Others may chime in, but I'm sure there are several books that will give you far more than just insight to PCD.

Have fun,
Frank