DIY Speakers, where do I start? (1 Viewer)

[RobertSchaez]

I'm new to all this and was wondering how to pick the right sounding kit for my budget, since I obviously can't listen to them first. Budget is about the cost of B&W 600 series. Actually, that is the sound I'm looking for, just better bass control and nicer cabinets.
Thanks

 

[chung_sotheby]

Check out Zalytron.com Speakercity.com Madisound.com and GRReasearch.com they all have kits that for about the price of a B&W 600 series (~600) will knock them out of the room, as well as have nicer cabinets. I, for one, have never been impressed with the 600 series, but the CDM and Nautilus line are a whole different beast.

 

[Brian Bunge]

Chung,
That's www.gr-research.com

 

[chung_sotheby]

Yup, you're right. My b

 

[Phil M]

Robert:
Here is a comparison that I did between the B&W Nautilus 805 & the ACI Sapphire III from ACI. (it's towards the bottom)
http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=56817&highlight=Sapphire
Phil

 

[jeff lam]

Actually Phil, I believe the Sapphire III enclosure is very difficult if you're not experienced. The baffle is designed with an ~14 degree upwards tilt to compensate for the woofer tweeter alignment.
Danny Richie explains woofer/tweeter alignment a little in this email he sent me coresponding to his original(old) AV1 and Dennis Murphy's MB1/(SPCA special) and why he recommended running them upside-down.

Jeff
I would run all the MB-1's with the tweeter under the woofer.
See this email I sent to Dennis regarding that (he had the same question).
I think my response to him will explain this pretty well for you.
The A/V-1 (at the time I sent this to Dennis) used a first order network
and I had the tweeter under the woofer.
It and Dennis's design both need the tweeter on bottom.
The new series network in the A/V-1 is the exact opposite. More electrical
delay is used to realign the drivers and the response is great on axis and
as the measuring axis is increased vertically. So if you use any of these
marked down enclosures with our series network just flip it over so that
the tweeter will be on top.
Good question Dennis,
Here are some of my thoughts on that.
The main thing in the end is how it sounds in the room.
One thing that is a given in any room is the listening height of the seated
listener. This can vary somewhat but from 8' to 10' away from the speakers
there is not a lot of variance.
Another given is that the speaker will be placed on a stand that is 24" to
29" tall typically. This means that it's in the lower 3rd of the room,
ceiling to floor.
The second possibility, especially in an audio store, is that the listener
may be standing. I person my even be inclined to walk up to the speaker as
it is playing.
So it's very likely that the listening position can change in the vertical
by going up (above seated ear level), but not at all likely to go down
(like laying on the floor).
So, should a more perfect image be cast up into the room or more down to
the ground?
Having said this lets look at the physical alignment of the drivers in the
A/V-1.
I first must ask myself who are these speakers for and who will be building
them?
To properly align the drivers physically the front baffle must be sloped
back about 12 to 14 degrees with the tweeter on top of the woofer. I forget
the specific degree, but it does not matter.
The average DIY speaker hobbyist looking to buy or build a speaker in this
low price range does not want to build a complicated enclosure. He wants a
easy to build rectangular shaped box.
Now ideally with a first order network the drivers need to be physically
aligned and the tweeter wired in reverse polarity to the woofer to allow
for the electrical shift in phase caused by the crossover.
Now if the tweeter is placed above the woofer the point at a listening
distance in which the drivers are more closely physically aligned is
somewhere close to the floor.
If the tweeter is located below the woofer the point at which the drivers
are physically aligned at a listening distance is in about the center of
the room.
If on the SPCA special you are getting the flat as a pancake curve at a
measuring point between the woofer and tweeter about 1/3 of the way down to
the woofer, and you get a couple of db dip in response if you simply move
the mic to the tweeter axis. The center to center of the woofer and tweeter
is only 4.75". One third of that is 1.583". Then at two times the measuring
distance (I assume 2 meters) the mic would need to be raised only 3.166" to
cause a couple of db dip?
Someone may be seated a little higher and experience a dip in response.
What if they stand up?
On tweeter axis is already about 12 to 14 degrees off center of the
physical driver alignment with the tweeter on top. Any upward movement
causes an even farther physical misalignment of the drivers.
On the A/V-1 with the tweeter above the woofer if I measure on tweeter axis
there is a slight amount of dip beginning to occur that gets worse as the
measuring height increases, and as physical driver alignment gets worse.
With the woofer on top of the tweeter and measuring on woofer axis the
response is great. No dips. If I increase the measuring height I get closer
and closer to an ideal Physical driver alignment. As measuring height
increases the curve remains very flat until such a height is reached that
the physical driver alignment starts to be mis-aligned in the other direction.
Thus, seated or standing at listening distance the response is essentially
the same. The response is more evenly distributed in the room as well.
So for these reasons I have chosen to place the tweeter on the bottom. I am
sure to many it may seem upside down, but actually it's just right.
I am sure you will experiment with moving your mic higher with the speaker
turned one way then the other.
On the A/V-1 I am sure will see the same effect on the curve that I see.
I am not sure what the changes in vertical response will be like on the
SPCA special, using a higher order network, but since you are already
showing a dip in response as measuring height increases I would guess that
you will notice similar effects with it as well.
Thanks for the question.
Danny Richie

I have a drawing that may help but can't seem to get it to load properly from my image host, I'll try to get it posted.
Lets try this:
http://imagehosting.bidbay.com/image.php3?imgID=1177748

 

[jeff lam]

To properly align the drivers physically the front baffle must be sloped

back about 12 to 14 degrees with the tweeter on top of the woofer. I forget

the specific degree, but it does not matter.

The average DIY speaker hobbyist looking to buy or build a speaker in this

low price range does not want to build a complicated enclosure. He wants a

easy to build rectangular shaped box.

This is how the saphire III's are built and I would think they are fairly difficult considering the angle you must achieve.

 

[Brian Bunge]

Jeff,

As long as you can get the angle right on the front of the top and bottom pieces of the enclosure you can cut the front oversized and trim off the extra. It's not as easy as I make it out to be (I've never done it myself), but it can be done.

I did help a friend build the Jags though! He used lots of sanding and bondo to fill any gaps before he added any type of finish.

Brian

 

[Patrick Sun]

May as well start making speaker enclosures out of adobe clay. Anyone remember "The Adobe" car commercial spoof on Saturday Night Live a long time ago (when the Yugo was first introduced)? Whenever someone ran into something with The Adobe, the driver would get out of the car, and just mold it back into shape.

 

[chung_sotheby]

Yeah, that was hilarious. I had the Saturday Night Live commmercial special on a VHS, but I lost the tape. One of the greatest compilations ever. Colon clean, Schmitts Gay, the Adobe clay car, the Obsession perfume knockoff ("from Calvin Clean"), the sixth finger-off potion, Hibernol, etc. I think that one way that manufacturers also compensate for driver center alignment is to mount a seperate tweeter enclosure on top of the woofer enclosure, kind of like what B&W, Diva and Norh do. Sometimes, if done well, this could make a very attractive cabinet.

 

[Jed M]

The Adobe Car was great!!! Everytime they got out of the car they had clay all over them. Good memories. I have that tape somewhere around here, looks like I may have to go digging for it.