Our new Home Theater build...Negatron 2

[wuzzzer]

Ironically I was using Google Maps street view today to look at areas of San Miguel that I remembered from visiting my sister there back in 2018.

[Khornukopia]

On 2/26/2020 at 8:02 PM, Ron E said:

Progress pics...we now have the holes cut in 4 K402s.. .hopefully sometime this week or next I will be assembling them.

The horns will protrude out the front a couple of inches from the motherboard. The motherboard will be 1 1/2" thick and made of 2 layers of MDF. The cabinet (if we decide to use a cabinet) will also be made of 1 1/2" MDF. The MDF will be covered with Mahogany veneer. We will be using Speakon jacks for the hookups. The cabinet will be 4' high x 25" wide...depth is not decided yet.

 

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It looks like your ports are longer than the ports in pictures of the original K-402 based MEH. Why the change?

[NBPK402]

Chris suggested I use a 1 3/4" holesaw instead and make them longer for my setup...they are still a 10:1 compression, just a little smaller diameter.

 

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[Khornukopia]

I will be watching your progress posts and pictures!

[NBPK402]

My friend anticipates starting the veneer done this weekend. I hope to have them home sometime next week. Once I do I need to run down and get some wood for the space frame, and then once that is done...get the wood for a cabinet.

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[NBPK402]

A little behind anticipated arrival. Today I delivered 5 4x8 sheets of 3/4" MDF. We discussed the cabinet part, and he is going to draw it up for me (I did a basic drawing showing my idea on how to put the cabinet together and still have nice veneer). If everything goes right I am hoping this weekend or early next week to have all 3 speakers in my home ready for assembly and tuning.

 

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[NBPK402]

A little behind anticipated arrival. Today I delivered 5 4x8 sheets of 3/4" MDF. We discussed the cabinet part, and he is going to draw it up for me (I did a basic drawing showing my idea on how to put the cabinet together and still have nice veneer). If everything goes right I am hoping this weekend or early next week to have all 3 speakers in my home ready for assembly and tuning.

 

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[NBPK402]

Today I picked up all the pieces for the front 3 horns, plus a spare....minus veneer and cabinets. Starting tomorrow I will start on the backbone frame, and then decide on the cabinet shape, and design. Once we test one without a cabinet, and another with a cabinet... I will then get them veneered with my Mahogany veneer. Hopefully they will be to the listening/tuning stage sometime next week.

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[NBPK402]

Today I picked up all the pieces for the front 3 horns, plus a spare....minus veneer and cabinets. Starting tomorrow I will start on the backbone frame, and then decide on the cabinet shape, and design. Once we test one without a cabinet, and another with a cabinet... I will then get them veneered with my Mahogany veneer. Hopefully they will be to the listening/tuning stage sometime next week.

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[Lbk]

On 3/3/2020 at 10:33 PM, Negatron said:

Chris suggested I use a 1 3/4" holesaw instead and make them longer for my setup...they are still a 10:1 compression, just a little smaller diameter.

 

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Did Chris change the holes because your speakers will be standing up right? Looks good so far, looking  forward to seeing finished cabinets.

Edited April 4, 2020 by Lbk

[NBPK402]

Not sure...Chris suggested this was the way he would do it if he was me.

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[PrestonTom]

Good luck with this project. It looks like you are making good progress. I toyed with the idea myself, but I get nervous about cutting up a K402. 

My guess is that they will be a bit over 2 ft wide and close to 4 ft tall. Any guess on what they might weigh (I imagine there is substantial bracing inside to carry the various loads)?

-Tom

[NBPK402]

I have no bracing currently I am making a support setup today. I am also planning on a 2 piece cabinet plus access that will tie into the support setup. I am still debating on how I want the cabinet to be shaped and still allow it to be removed if desired. If I were to guess, I would say currently the setup weighs 150lbs+, and by the time it has a complete cabinet it will be over 200lbs. Double wall MDF is very heavy.

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[PrestonTom]

I assume this a sealed cabinet and not ported.

 

I am curious about the weight of the tweeter driver. In my case it would be a JBL 4 inch voice coil version and it is about 35 lb. In your case that EV driver also probably weighs quite a bit. I am leery about mounting it to the K402 without adequate support since I would hate to have the horn's flange self-destruct. Are you going to run some sort of internal shelf across the width of the cabinet?  Everything I have sketched out seems rather makeshift and may not hold up if the cabinets were ever moved or tipped. 

 

Interesting project,

-Tom

[NBPK402]

I assume this a sealed cabinet and not ported.

 

I am curious about the weight of the tweeter driver. In my case it would be a JBL 4 inch voice coil version and it is about 35 lb. In your case that EV driver also probably weighs quite a bit. I am leery about mounting it to the K402 without adequate support since I would hate to have the horn's flange self-destruct. Are you going to run some sort of internal shelf across the width of the cabinet?  Everything I have sketched out seems rather makeshift and may not hold up if the cabinets were ever moved or tipped. 

 

Interesting project,

-Tom

[/quoteCurrently what I am doing is supporting the EV DH1A driver only, but I I am thinking of also supporting the woofer mounting pads. Currently it is resting on a t channel setup, but later I hope to have it supported with MDF or solid wood. My EV DH1A weighs about 30lbs, and each woofer is about 15lbs. The first version (which is what I posted up ) is going to be tested as a open baffle setup with the intention that a sealed cabinet can be attached to the speaker setup frame. I will be assembling the 3rd setup this weekend, and also the framework for free standing or a cabinet. The k402 horn protrudes out of the 1 1/2" thick front baffle and is sandwiched between angle cut MDF. In addition we used construction adheasive to attach 2 triangular shaped pieces of MDF...this is then used as a mount for the woofer mounting pads by screwing them to the the glued triangles. Currently we are using silicone to seal the woofer ports, but when we disassemble it all to veneer the cabinets... I will use clay (just in case I ever need to remove the horn from the cabinet).

 

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[Chris A]

8 hours ago, Lbk said:

Did Chris change the holes because your speakers will be standing up right? Looks good so far, looking  forward to seeing finished cabinets.

No...This is a tradeoff between length of woofer ports and their width.  The woofer ports (the "off-axis" ports) affect the combined off-axis polars of the entire MEH loudspeaker.  Longer/narrower ports are a bit better at spreading out and minimizing the reduction in extreme off--axis SPL response around frequency band that corresponds to the 1/4 wavelength distance from the throat. 

 

One of the no-no's of MEH work is to put too large a port across one wall of a pyramid-type horn (like the K-402).  You'll get a drop out in off-axis polars that corresponds to that frequency band. Making the off-axis ports too small affects the efficiency of the woofers, too large affects the off-axis polars. 

 

These are tradeoffs that many amateur MEH builders apparently are not paying much attention to.  I try to pay attention to them. 

 

BTW: the tradeoffs that are made for MEHs are far less of a compromise than using separate horns like on "conventional" loudspeakers...in terms of the resulting sound quality and issues with lobing at the crossover frequency bands--among other issues such as time misalignments.

 

Chris

[Lbk]

On 4/4/2020 at 3:56 PM, Chris A said:

No...This is a tradeoff between length of woofer ports and their width.  The woofer ports (the "off-axis" ports) affect the combined off-axis polars of the entire MEH loudspeaker.  Longer/narrower ports are a bit better at spreading out and minimizing the reduction in extreme off--axis SPL response around frequency band that corresponds to the 1/4 wavelength distance from the throat. 

 

One of the no-no's of MEH work is to put too large a port across one wall of a pyramid-type horn (like the K-402).  You'll get a drop out in off-axis polars that corresponds to that frequency band. Making the off-axis ports too small affects the efficiency of the woofers, too large affects the off-axis polars. 

 

These are tradeoffs that many amateur MEH builders apparently are not paying much attention to.  I try to pay attention to them. 

 

BTW: the tradeoffs that are made for MEHs are far less of a compromise than using separate horns like on "conventional" loudspeakers...in terms of the resulting sound quality and issues with lobing at the crossover frequency bands--among other issues such as time misalignments.

 

Chris

Does the location of the port affect the sound? Looks  likes yours and negatons are  center a 1/3 of the way up up the side of the horn.         

 

Are these going to be a 2 way design, haven't seen any mention of a separate tweeter. Thanks'

Edited April 6, 2020 by Lbk

[Chris A]

26 minutes ago, Lbk said:

Does the location of the port affect the sound?

Yes, it does.

 

26 minutes ago, Lbk said:

Are these going to be a 2 way design, haven't seen any mention of a separate tweeter.

If one adds a "separate tweeter", I recommend these to make them three-way loudspeakers:

 

http://www.bmsspeakers.com/index.php?id=bms_4592nd

 

Once dialed in well, they sound just like the TAD TD-4002s on either side of the center K-402-MEH...in my setup.

 

Chris

[Delicious2]

On 4/4/2020 at 8:26 AM, Negatron said:

On 4/4/2020 at 7:24 AM, PrestonTom said:

[/quoteCurrently what I am doing is supporting the EV DH1A driver only, but I I am thinking of also supporting the woofer mounting pads. Currently it is resting on a t channel setup, but later I hope to have it supported with MDF or solid wood. My EV DH1A weighs about 30lbs, and each woofer is about 15lbs. The first version (which is what I posted up ) is going to be tested as a open baffle setup with the intention that a sealed cabinet can be attached to the speaker setup frame. I will be assembling the 3rd setup this weekend, and also the framework for free standing or a cabinet. The k402 horn protrudes out of the 1 1/2" thick front baffle and is sandwiched between angle cut MDF. In addition we used construction adheasive to attach 2 triangular shaped pieces of MDF...this is then used as a mount for the woofer mounting pads by screwing them to the the glued triangles. Currently we are using silicone to seal the woofer ports, but when we disassemble it all to veneer the cabinets... I will use clay (just in case I ever need to remove the horn from the cabinet).

Yes, fascinating project!  Got any more pictures of the initial setup/evolution?  Still plan on testing as "open baffle" (not sure how that would work when only the woofers fire to the rear) and if so wouldn't the baffle have to be much larger than what your pictures show so far?

If already going to a sealed cabinet without OB testing, why have the horn protrude from out front?  Won't that be difficult to seal off?  Why not have the horn lip seal to the cabinet front much as it does with the KPT-305 which cabinet Chris used for his MEH?

Speaking of the KPT-305,  Klipsch went to the trouble of enclosing the back of the 8 inch driver in that  mid bass module in a metal can - really sealing it off inside the  305 box.  Maybe our evolving MEH designs should go in that direction?

[NBPK402]

Please excuse the mess. I was working on the framework for the speakers most of today, and I have 3 MEHs ready to wire now. I do not know when I will be able to buy more MDF as HD, and the lumber yards are now closed in our area. At least I will be able to enjoy them as OB until I can try a cabinet. A cabinet will be made to where it can fit the existing structure. Once I find out which way we like it I will be getting them veneered in Mahagony that way.

 

As far as the OB the woofer do fire forward through the horn...so this will be to me another way to try the MEH. It might be a total failure as a OB, but I can always add a cabinet to it.

 

As far as dealing the horn to the baffle...we have 2 layers of MDF, and also overlapping as the easiest way to do it was to angle cut a sheet of MDF into 3 pieces, and then angle cut the other way to remove the center area for the horn. It is pretty solid right now, and when we do the final build on it we will also seal it off with caulk.

 

The speakers are already pushing 200lbs each, and will def be a good amount over 200 with a cabinet. We have constructed this to where we can still take it apart for shipping if we want to, as the horn can be removed from the front baffle. Whe the horn is removed only theb1 side triangle would remain as they are glued with construction adheasive, and the woofer plates attach to them with screws.

 

Another reason for not having a simple box if footprint...in order to minimize the footprint we also needed to raise it off the floor to get the horn center closer to the correct height. If we mounted them the way everyone else does it would have been much wider, and we would have to raise them off the floor even more,

 

The last pic is why I have the horn protruding the front baffle. I liked the design and wanted to do a MEH like this non MEH speaker. I also wanted to try out open baffle to see how I like it. As far as the front baffle being wide enough...time will tell, and if it is not and a box sounds better, it will have a box.

 

 

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