[SteveRB]

Hi,
i've been having some fun with open baffle designs with great results. However, I feel like i have been flying a bit blind, and i would like to start gaining bit more knowledge on the subject. To that end I hope to be posting a few different Beginner Questions. Any help out there would be appreciated.

Question 1.
When connecting three speakers in a three-way design should the drivers be connected all in parallel to the binding posts?  ... in series?  or can the speakers be combined parallel and series to achieve different total impedance and individual wattages?

are there any major disadvantages?

I have been experimenting with an impedance calculator available here:
http://www.duncanamps.com/software.html

based on the numbers input, i see that putting the tweeter and mid driver in series and the bass woofer in parallel i can change the wattage ratio between the three drivers. Can this be used to give the bass driver more power (proportionally)?

[panomaniac]

If you are using a crossover of any order  - then the speaker drivers are connected to the outputs of the crossover - NOT the binding posts on the back of the speaker.  Tho usually the ground (neg) is common.

Is that what you mean?

[SteveRB]

Thank you for the reply.  I am still confused. In my projects i don't see the crossover as point from which the speakers driver are connected as a whole. each woofer is wired from it's own point in the crossover where the binding posts act as the source (+ and -).

Can you please relate your example to series or parallel connected to the source?

thanks again, i really want to have an understanding of this.  perhaps in the morning i will post a diagram to illustrate my thinking.

[David Weil]

That impedance calculator does not seem to be of much use, because it does not include the cross-overs influence. And it treats speakers like Ohmian resistors, which they are not. Speaker impedance varies a lot across the frequency.

The total impedance is influenced by the cross-over. Each way of the cross-over has a low impedance in its working range and a high impedance outside of it. E. g. a low-pass filter for a woofer has low impedance below its cross-over frequency, and a high impedance above it. Thus the effective impedance is more or less the speakers own impedance in its working region, and something much higher outside of its working area. The cross-over channels are paralleled in most cases. Due to their different impedances in each frequency range the overall impedance is in an amplifier-friendly range throughout the entire frequency range.

You cannot change the speaker connection to series or parallel any way you like, because the cross-over is designed for the impedance of the connected driver. The impedance calculator shows you that connecting several speakers together results in a different impedance. The cross-over will not work as intended anymore.

Serial cross-overs also exist. Connecting your existing mid- and high-range in series will however result in something unpredictable. The mid-range filters high and low frequencies out, the high-range filters low and mid frequencies out. What remains for the speakers?

[SteveRB]

thanks for the straight reply.

Is there a simple way to test what is the overall average impedance of a speaker build?

Currently i am working on a open/ infinite baffle project using the 'endorphin' as my model

http://www.lampizator.eu/SPEAKERS/PROJECTS/P17/Endorphine%20from%20Kingston%20Kitchen.html

the saba drivers are, 5 ohm (tweeter) and 5 ohm (woofer) - with an 8 ohm Altec bass driver. What is the overall impedance? What speaker terminals should i use 8 or 4 ohms...?

[David Weil]

Is there a simple way to test what is the overall average impedance of a speaker build?

Speaker Workshop can do such measurements. An evaluation version is available for download. I have never used it myself, so I cannot promise that it is simple, although I think it is.

[panomaniac]

Probably the 8 ohm tap.  The Altec woofer is going to be the major influence on impedance.  With the simple crossovers in front of the Saba drivers, impedance should be a bit higher than the nominal 5 ohms for those sections.
If you really just "have to" know - buy a WT3 at parts express and run a sweep.  The WT3 will show you exactly the impedance of your rig, from 20Hz to 20Khz.  They were on sale last week.

But it certainly won't hurt to use the 4 ohm tap - might even sound better!  (as explained in the post above)

Have fun with the project, let us know how you like it.  I've built a similar rig and really enjoyed it.

[SteveRB]

I just got my Mapletree Stealth 60 back from repair/ rewire. I am able to swap 4 ohm/ 8 ohm now from the speaker terminals. And i have to say that the 4 ohm tap sounds better. But i think (havn't measured yet) the el34's are burning hotter...


the Saba/ Altec set-up is awesome. Very lively. They do not behave like modern hifi speakers, but do bring out amazing qualities in different records. Motown records sound really come alive. Electronic music and hip-hop records lack punch. I have the Altecs mounted in the wall between my livingroom and my bedroom (better than a bookshelf). I'll post some pics this week.

[panomaniac]

Cool, can't wait to see them!

That punch you're lacking is usually in the 90~100Hz region.  That's where PA rigs get all their slam.  The Altecs should do it, if you put them in the wrong box.

[SteveRB]

HA!

[ecir38]

Is there a simple way to test what is the overall average impedance of a speaker build?

Have never tried it but read a couple of years back I think in the HTguide forum that what I put together in this pic as a reminder for me should work.



Just fiqure the pic of the speaker as the banana post before the cossover and drivers.

BR

[jeffac]

"Electronic music and hip-hop records lack punch."

If using CD, it might not so much be the speakers fault as the overblown expansion on the CD used to make everything sound 'LOUD'  Disregard if playing LPs.

Haven't tried it, but Cutestudio has software to help correct clipping which apparently can make some unlistenable CDs passable. No affiliation, but looks like it could be quite useful for some 'loud' CDs.

http://www.cutestudio.net/

cheers.. jeffac

[David Weil]

Is there a simple way to test what is the overall average impedance of a speaker build?

Have never tried it but read a couple of years back I think in the HTguide forum that what I put together in this pic as a reminder for me should work.



Just fiqure the pic of the speaker as the banana post before the cossover and drivers.

BR

That is more or less how all resistance measurements work. And yes it would work for you, if the source is a frequency generator or any source for sine waves, and you have the time and nerve to take notes on the impedance for each frequency.