3-way Tower

[SoundmanDave]

I am in the planning stages of a pair of 3-way towers. I have all the drivers I need but need some help with the build parameters.

I am going to be using a 1" tweeter, 2-6" mids and 1 or 2 - 8" woofers and I intend to port the cabinets. Here are the questions I have:

1) Should I use one or two 8" per tower?
2) What layout is best? 1-6-6-8(-8); 6-1-6-8(-8)
3) Should the port(s) be on the front or back or does it matter? Should I have separate ports for the 6" and 8" drivers?
3) I understand I should separate the chambers between the 6" and 8" drivers but should I separate the chamber between like drivers, like the two 6" or the two 8"?
4) If I connect the two 6" in parallel should I design the xover as a 4-ohm load or should I design two separate xover circuits, one for each driver?

That should be enough for starters.

Thanks in advance...

[jleaman]

Originally Posted by SoundmanDave

I am in the planning stages of a pair of 3-way towers. I have all the drivers I need but need some help with the build parameters.

I am going to be using a 1" tweeter, 2-6" mids and 1 or 2 - 8" woofers and I intend to port the cabinets. Here are the questions I have:

1) Should I use one or two 8" per tower?
2) What layout is best? 1-6-6-8(-8); 6-1-6-8(-8)
3) Should the port(s) be on the front or back or does it matter? Should I have separate ports for the 6" and 8" drivers?
3) I understand I should separate the chambers between the 6" and 8" drivers but should I separate the chamber between like drivers, like the two 6" or the two 8"?
4) If I connect the two 6" in parallel should I design the xover as a 4-ohm load or should I design two separate xover circuits, one for each driver?

That should be enough for starters.

Thanks in advance...

1 tweeter and two 6.5" would be nice, i sure miss my old tower Mine were ported and had very deep bass.

[picowallspeaker]

Does it have to be a tower ? Why not the two woofers at the sides and MTM in between ?If you're going to put a port,you have to calculate (even in sealed cabinet you do this) also the length and diameter of the tube (if needed ),the position and the volume of air coupled to it.Two speakers wired in parallel behave as one speaker (easing also crossover design ! ).By doing this,it halves the impedance ,doubles sensitivity and output . So it will be good to keep the overall impedance (the one seen by the amplifier ) the same ,so 4 Ohm in total for bass , 4 Ohm for mid ,and a negligible 8 Ohm for the tweeter.

[jleaman]

Originally Posted by picowallspeaker

Does it have to be a tower ? Why not the two woofers at the sides and MTM in between ?If you're going to put a port,you have to calculate (even in sealed cabinet you do this) also the length and diameter of the tube (if needed ),the position and the volume of air coupled to it.Two speakers wired in parallel behave as one speaker (easing also crossover design ! ).By doing this,it halves the impedance ,doubles sensitivity and output . So it will be good to keep the overall impedance (the one seen by the amplifier ) the same ,so 4 Ohm in total for bass , 4 Ohm for mid ,and a negligible 8 Ohm for the tweeter.

It also depends on his amplifier too, if he only has a 2 channel amplifier then this will be hard.

Here is a link to my old towers

Brian's Gallery :: Tower's

[SoundmanDave]

Thanks, picowallspeaker. That is some of the information I was hoping for. I have to dig up my box of drivers to make sure I have enough to make a double 6" and double 8", thus providing the load balance you mentioned.

The Tower is simply for size constraints and stability. I don't have a big shelf to put speakers on and I have limited floor space but I have young kids so I don't want bookshelves on stands.

I am not against using waveguides instead of ports but I am comfortable doing all the required calcs to work out the port sizes. Does the port location matter? And should I put in two ports, one for the 6" chamber and one for the 8" chamber, or just the 8" chamber as they will be handling the low-end. Also, if I combine the like drivers in one chamber, will they cause interferences with each other? By that I mean, if one is slightly more efficient than another (real world) then would it cause power loss in the second (weaker) driver?

I thought my xover frequencies would be around 400-500Hz and 4k-5kHz. I could maybe lower the low-end to 250-300Hz. I know the 6" drivers can handle it but I just don't know if it is needed. A friend suggested starting with a xover that has one or two variable parts so I can 'tweak' it a bit either way. Any thoughts on that?

Thanks again.

[SoundmanDave]

Originally Posted by jleaman

It also depends on his amplifier too, if he only has a 2 channel amplifier then this will be hard.

Here is a link to my old towers

Brian's Gallery :: Tower's

Those are some nice towers. I am planning something a bit simpler. I estimate the cabinets to be 9" x 12" x 36". This of course will depend on the volume calculations once I get to that.

I am using a stereo amplifier. Nothing fancy but good quality. It is an amp that I helped develop with a company that I used to work for. The company is no longer but I still have one of the units and it works great. It is about 40Wpc into 8ohms and is 4-ohm stable.

BTW: I like your chip-amp setup. My former co-worker was making his own of the same system. I actually designed two amps that were loosely based on that chip-amp design. One made it to market the other did not.... That chip-amp design is rock-solid though and usually sound great with little tweaking.

Thanks.

[picowallspeaker]

Waveguide properly used with the tweeter helps in some way to smoothen the transition to midrange. It is an option to look at . You meant not simply truncaded pipe for the port,maybe !

[SoundmanDave]

I am really open to any suggestions as long as it is not too difficult to materialize. I have a limited shop so there are some physical limits to what I can create.

What are your thoughts on a dual ports that meet the same calculated volume but split the depth and diameter. I've seen it done on a few different speakers but I can't say I've ever listened to them close enough to know if they are a good idea or not.

[event horizon]

Originally Posted by SoundmanDave

1) Should I use one or two 8" per tower?
2) What layout is best? 1-6-6-8(-8); 6-1-6-8(-8)
3) Should the port(s) be on the front or back or does it matter? Should I have separate ports for the 6" and 8" drivers?
3) I understand I should separate the chambers between the 6" and 8" drivers but should I separate the chamber between like drivers, like the two 6" or the two 8"?
4) If I connect the two 6" in parallel should I design the xover as a 4-ohm load or should I design two separate xover circuits, one for each driver?

Originally Posted by SoundmanDave

I thought my xover frequencies would be around 400-500Hz and 4k-5kHz. I could maybe lower the low-end to 250-300Hz. I know the 6" drivers can handle it but I just don't know if it is needed.

1. It depends on the 8" driver parameters & the kind of response you can coax from the completed enclosure. If the available cubic volume looks close to the drivers VAS you'll probably be better off with 2 drivers, though this depends on the driver Qts as well.

2. I'd go for the MTM or D'Appolito arrangement. Simply put at crossover if the 2 x 6" drivers are to one side of the tweeter the directivity of the sound can be directed at quite an angle upwards (usually) if the mids are below the tweeter. If there is a driver either side being fed the same signal the directivity will remain forward as both up & down radiation will cancel.

3. As long as you seperate the "different" drivers you'll be ok, the two 6" can be in the same enclosure as they'll be being fed the same signal. Likewise if you use two 8" drivers, they can share the same box.

4. You'll need to design the crossover for each different impedance. So assuming your tweeter is 8 ohm then design that section feeding the tweeter for an 8 ohm driver. If the two 6" in parallel make 4 ohm that section will need to be designed for 4 ohm.

By the way, if you are planning to use the 6" drivers for midrange there is zero point in porting that part of the enclosure as they'll see no bass (normally - unless you are doing something very odd indeed). Also the volume of box they take up can be quite small, possibly only 4 or 5L (depending on driver specs).

Whether you have the port on the front or the back depends on how much room you envisage between the back of the speakers & the rear wall. If it'll be less than 2ft i'd suggest you have a port on the front. However, if you have a gradually falling bass response i'd possibly have it at the back to get some reinforcement. Again this depends on the driver parameters, enclosure size & possibly room size.

Any chance of posting the driver specs & some kind of idea on enclosure internal volume? Can help a lot more then

Good luck

[SoundmanDave]

Well, I took an inventory of what I have, sadly, there were no spec sheets in the boxes. I am trying to dig up my old contacts for the specs to get all those juicy details... stay tuned...

I do have enough drivers to go with my original idea of 6-1-6-8-8 but I have two different pairs of 6" drivers. Essentially they are the same but one pair has a nice dust cover on it (that matches the 8" drivers) and the other pair does not.

So if I go just for looks, I'm better off with a 1-6-8-8 configuration. Any pros or cons for this setup?

thanks,