[dawaro]

I am looking at some options to add bass bins to my A/V-3Neo's and wanted to see what others might think would be best.
My room is roughly 20'x20' with 9' ceilings. The A/V-3's will be in sealed enclosures and actively crossed on the lowend at 180hz. The speakers will be completely rebuilt as towers so I have limited the choices to the M130 line to keep the baffle with from changing. For asthetics I have also ruled out a side firing sub because I do not like the look of the flared out lower portion of the enclosure it would require.
The two options that I am most interested in is (A) 2 - M130X's in a ported enclosure or (B) 4 - M130/16's in a sealed enclosure like the lower end of the OB-7.
If it where you what would you choose and why?

[Danny Richie]

4 M-130's in a sealed box would be a good choice and will actually give you something over what you already have (a pair of M-130/16's).

However I'd cross them in the 80Hz range and no higher than 100Hz for sure. That will give the best transition and sound quality.

[dawaro]

4 M-130's in a sealed box would be a good choice and will actually give you something over what you already have (a pair of M-130/16's).

However I'd cross them in the 80Hz range and no higher than 100Hz for sure. That will give the best transition and sound quality.

Should I use the same enclosure design that is used in the bottom of the OB-7 design or would you recommend something different?

[Danny Richie]

Its tried tested and proven.

So long as you maintain that air space and its braced well you're fine.

[dawaro]

Danny why would this configuration require such a lower crossover point between the mids and woofers than the OB-7?

[Danny Richie]

It doesn't require a lower crossover point but the lower crossover point is more optimal.

The MTM section in a sealed box will play to a -3db down of at least 80Hz without room gain.

[dawaro]

Here is a rough drawing of the bracing layout for my A/V3 Neo with the OB7 bass section. Can some of you look it over and give me your opinions. My concern is based on the bottom section of the cabinet. The speakers are going to be powered by a five channel plate amp that will be housed in the bottom of the enclose along with the crossover boards. The bottom 18" of the woofer enclosure back wall is moved in 4-3/8" to accommodate the amp and crossover. I have placed it at the bottom for the simple reason of keeping the RCA and power connections at the bottom.
So long story short is there going to be any negative effect from the decreased depth at the bottom of the enclosure?
If it is I can move the amp and crossover to the top and use one of the blank Dayton binding post plates at the bottom with an EIC jack and RCA connector and run the cables through the enclosure but I would prefer to keep it at the bottom.

So what do you think?

[klh]

Looks nice, but I'm just a layman. Did you forget a woofer? I take it the width of the enclosure is 8".

[Hank]

Regarding the bass section, keep the internal volume the same as the OB7.  You can certainly take part of that volume by mounting your plate amp and xover where you plan to.  Just add to the cabinet depth a tad to gain back that lost volume.  I wouldn't advise you to put the amp and xover up top - keep them as planned so the weight is at the bottom for stability.

[Danny Richie]

A couple of other things I would do is to take that back wall behind the mids and make it a wall that is not parallel to the mids. Start about where your 5.5" measurement is in the drawing and slant the rear wall from there to one of the far back corners.

I'd also consider getting the crossover further away from the plate amp because the transformer on the plate amp (unless it is a switching power supply) will couple with the inductors and it could pick up a hum.

[dawaro]

Looks nice, but I'm just a layman. Did you forget a woofer? I take it the width of the enclosure is 8".

You are right there is a missing woofer. When I colored the last brace SketchUp made a face in that section and covered the woofer up! Also, yes the baffles are 8" wide per the A/V-3 neo and OB-7 design.

[dawaro]

Regarding the bass section, keep the internal volume the same as the OB7.  You can certainly take part of that volume by mounting your plate amp and xover where you plan to.  Just add to the cabinet depth a tad to gain back that lost volume.  I wouldn't advise you to put the amp and xover up top - keep them as planned so the weight is at the bottom for stability.

The bass section is going to have the same volume as the OB-7 does in the end. I havent calculated everything after the latest revisions so there may be adjustments that need to be made in the final version.
The section behind the MTM and the amplifier section are identical so that the volume for the amp is offset.

[dawaro]

A couple of other things I would do is to take that back wall behind the mids and make it a wall that is not parallel to the mids. Start about where your 5.5" measurement is in the drawing and slant the rear wall from there to one of the far back corners.

I'd also consider getting the crossover further away from the plate amp because the transformer on the plate amp (unless it is a switching power supply) will couple with the inductors and it could pick up a hum.

Danny is this what you are suggesting?


If so am I correct in assuming this is to reduce the standing waves in the enclosure?
The amplifier is a Bash design with a switching power supply but I had not thought of the inductors coupling. Do you think it will be ok since it is a switching power supply or should I plan to move it just to be safe? What kind of distance is needed?

[ebag4]

Hi Dwaro,
Sorry to be a bit OT here, can you give the make of the 5 channel plate amp you mentioned above. A website with info on it would be appreciated as well.

Now back to the regularly scheduled thread...

Ed

[Danny Richie]

Danny is this what you are suggesting?

No, what I am talking about goes from the side wall to the rear corner. Think of it from the perspective of a top view. Look at your brace that is in the bright baby blue. Now imagine a diagonal divider that starts just before the peak of the arch on the first circle and to the far right side of the brace. Then draw a diagonal line to the opposite far corner on the back wall.

What you are left with is a wedge shaped design that will minimize reflected energy back through the cone.

It is like a tapered transmission line that is sealed.

Make sense?

[dawaro]

OK Danny I see what you are saying now. Thanks

[dawaro]

Hi Dwaro,
Sorry to be a bit OT here, can you give the make of the 5 channel plate amp you mentioned above. A website with info on it would be appreciated as well.

Now back to the regularly scheduled thread...

Ed

Ed the amplifiers are from the original Klipsch ProMedia 4.1 speakers. I bought a few of them that were new surplus. Each plate has 5 separate amplifier channels that can be configured to drive any of the three input signals (front, rear, sub). A friend of mine worked the numbers to change the stock xover points to 100hz hp/lp with a 25hz sub sonic filter. originally they had a 60hz hp/lp with a 40hz sub sonic filter which would probably explain why people complain about the small ported boxes in the set being so boomy. At one time Apexjr.com had the amplifiers but they have long since sold out.

[ebag4]

Dawaro,
Thanks for the info, great find and application!

Ed

[dawaro]

Dawaro,
Thanks for the info, great find and application!

Ed

If it is something you might me interested in let me know because I havent yet decided if I am in fact going to use them