adjustments to 2way

[rsmith]

I have made my first attempt at building speakers and am not all that thrilled with the results. I used the Dayton classic 8 woofer with the Audax (276-102) 3/4 textile shielded dome tweeter. I have a Zobel on the woofer and a L-pad on the tweeter. I used a PE crossover (260-142) 2500hz 2 way. The cabinets are 1.2cuft with a port. I am not sure how to put this but the speakers have a "in your face" sound to them. The sound lacks smoothness I guess is another way to put it. I am thinking of replacing the tweeters, or should I switch out the woofers with units that have a hight FR. Any help will be greatly appreciated.

[Chris Roemer]

> I have made my first attempt at building
> speakers and am not all that thrilled with
> the results. I used the Dayton classic 8
> woofer with the Audax (276-102) 3/4 textile
> shielded dome tweeter. I have a Zobel on the
> woofer and a L-pad on the tweeter. I used a
> PE crossover (260-142) 2500hz 2 way. The
> cabinets are 1.2cuft with a port. I am not
> sure how to put this but the speakers have a
> "in your face" sound to them. The
> sound lacks smoothness I guess is another
> way to put it. I am thinking of replacing
> the tweeters, or should I switch out the
> woofers with units that have a hight FR. Any
> help will be greatly appreciated.

Howdy.

I LOVE that 8" driver. It's best (ported) in around 1.7 cf (or more). I would guess that sealed it would like about half that volume. I can tell you more if you tell me your tuning freq., or BEST, the inside dims of your cab as well as the inside dia. and length of your port.

It DOES have quite a hump around your cross point, but I've run it almost wide open without it really sounding "bad". Sometimes a 2nd order xo can accentuate that hump if you don't use a Zobel, but you have, so I'm thinkin' if it really stinks, it might be your box tuning. Can you tell me exactly what the component values are on that PE xo? I've never bought one so I don't know. I think it's a textbook 8 ohm, LR at 2.5 kHz though. Also, what's your Zobel made from?

Typically, a smaller tweeter (3/4" as opposed to 1-1/8", like Dayton's -070) is used where the midbass can reach higher than 2.5 k. They have higher Fs values that typically indicate an Fc of 3 to 3.5 kHz or higher. Yours has an Fs of 1.6k, so typically the lowest you'd go would be one octave up (or 3.2k) with a 2nd order. Also, ferrofluid helps to control a tweeter near resonance, I'm not sure your tweeeter uses ff. If not, and if your Fc is too low, you could be hearing that little tweeter complaining at its Fs. Also, I've used that 8" with Dayton's "silky", which is 3 dB quieter than your tweeter. Another thing is that that tweeter is nominal 6 ohms, while I think that xo is made for 8. THAT can cause peaking at the x pt. as well. If you can tell me the exact values in the HP on that Dayton xo, as well as what's in your L-pad, I can try modelling it to help you more.

Another thing is that you should try reversing the polarity of your tweeter. There is really no cut and dried rule as to how ANY tweeter should be wired. It's always best to listen to it both ways before everything get buttoned up. Also, did you line your cab with egg-carton (convoluted) foam? Mid freqs can reflect off the back of the cab and pass through the woofer cone or out the port if it's front mounted.

Your problem COULD be a combination of all these things, but I think we can iron them out, although you might have to try a more suitable tweeter.

Chris

[daver]

The Audax 3/4" tweeter may need to be crossed over a little higher. Also, its DC resistance (Re) is close to 4 ohms. If "in your face" refers to excessive highs, that could be part of it.

The pre-built crossover is designed for a nominal 8 ohm tweeter with Re about 6.8.

You might try the Audax TM025F1 (276-152), which is a 1". Its resonance is lower, and it should have no trouble crossing over at 2500 Hz. You might still need to pad it down a little more. Try increasing the series resistor in the Lpad.

Another option is to look at the "Noah's 8" 2-way in the project showcase on the PE website. It uses the same woofer, but requires a different size enclosure, different tweeter, and a crossover which requires building from the ground up.

-Hope this helps.

Dave R

> I have made my first attempt at building
> speakers and am not all that thrilled with
> the results. I used the Dayton classic 8
> woofer with the Audax (276-102) 3/4 textile
> shielded dome tweeter. I have a Zobel on the
> woofer and a L-pad on the tweeter. I used a
> PE crossover (260-142) 2500hz 2 way. The
> cabinets are 1.2cuft with a port. I am not
> sure how to put this but the speakers have a
> "in your face" sound to them. The
> sound lacks smoothness I guess is another
> way to put it. I am thinking of replacing
> the tweeters, or should I switch out the
> woofers with units that have a hight FR. Any
> help will be greatly appreciated.

[georgem]

> I have made my first attempt at building
> speakers and am not all that thrilled with
> the results. I used the Dayton classic 8
> woofer with the Audax (276-102) 3/4 textile
> shielded dome tweeter. I have a Zobel on the
> woofer and a L-pad on the tweeter. I used a
> PE crossover (260-142) 2500hz 2 way. The
> cabinets are 1.2cuft with a port. I am not
> sure how to put this but the speakers have a
> "in your face" sound to them. The
> sound lacks smoothness I guess is another
> way to put it. I am thinking of replacing
> the tweeters, or should I switch out the
> woofers with units that have a hight FR. Any
> help will be greatly appreciated.

I'm not an expert at all so take my comments with a grain of salt. Perhaps one of the pro's can steer you in the right direction. These guys have money invested in measurement tools and software for a reason. It's really hard to do a good speaker by mixing together random off the shelf parts. A woofer that size has break-up modes at higher frequencies but in this case might be OK - though the frequency plots suggest there might be a problem above 2k so your 2.5k cross is maybe a little high. The tweeter is also a little small to cross that low. You probably should think about a 1 inch tweeter with a much lower Fs. Also, the tweeter is the wrong impedance for that x-over so the true x-over point is really something other than 2.5k. Plus the tweeter is more efficient that the woofer so it is playing too loud and needs to be brought down in level.

Couple of ideas.
1) Check the PE speaker building showcase and build the Noah 8's. This is yor best bet for a good outcome. Unless you have the tools and knowledge, builing from a known design is your best bet. You already have the woofers. You need the tweeters and x-over parts. While your cabinet would yield a different low-end response, at least copying those parts would get you something better than you have now. Best of all would be to rebuild the boxes to match the Noah 8's.

2) Try sticking a 4 ohm sandcast resistor in series with the tweeter connection but before the Zobel. This would at least get the impedance somewhere in the range of what the x-over was designed for. My guess is that things will sound at least a bit better. (Please take this recommendation with a huge grain of salt. It's what I would do based on my rudimentary knowledge.) Now you still should probably add an l-pad since the tweeter is I'm sure still a bit bright. If you do a google search you can find lots of references on l-pads and how to implement them.

3) Your x-over has no baffle step designed into it hence it probably sounds a little thin on the bottom end. This is tough to fix. You can try to put them right up against the wall - that may help a little.

Hopefully one of the pro's who hang out here can give you better answers. Maybe one of them can even point you in the right direction as far as a better x-over for your current configuration.