Jump to content

A K-402-Based Full-Range Multiple-Entry Horn


Chris A

Recommended Posts

I think the normalized plots are misleading....it would be better to overlay the actual total impedance, and you'll find the exponential horns have more loading....even at lower frequencies (below Fc). The issue is that the value of "1.0" for the exponential is much higher than the value of "1.0" for the conical.

Link to comment
Share on other sites

I might agree with you on this point, but look closely at the vertical axes units: the acoustic resistance at the throat of the horn is not normalized to anything but throat area and rho-c

Link to comment
Share on other sites

Generally, this includes horns without bends in their central axes that have area expansion formulas that are a quadratic function of the distance from the horn's throat, i.e.,

 

y = ax2 + bx + c

 

In the special case of the conical horn, the formula is y = ax2.  This is not the equation of the straight-sided portion of the K-402 horn--it's not conical...but it is straight-sided.

 

Chris

Link to comment
Share on other sites

  • 2 months later...
On 1/12/2016 at 6:39 PM, Quiet_Hollow said:

Just be mindful with running a full-range horn (like the OP's perforated K402, Synergy, Unity, etc..) 1/4 wave interference from the floor will be a major factor below Fc.

 

The 2 & 3 way designs (K-horn, Jub, La Scala, Belle) fare much better in that regard.

 

IOW, for the uninitiated, don't fuss too much (or get overly excited) about how much low freq performance is gained going full range, unless the plan is to set them on the floor. At ear level, they'll need to be high passed according to their nearest boundary distance regardless of capability.

I am about ready to start cutting I to my 402...I will be running mine vertical, and was hoping to to just tilt them upward. How is this going to affect the sound? I have a very live room that has not been treated yet with stone floors, clay walls, and a curved clay ceiling 30' high.

Link to comment
Share on other sites

Ron, I'd recommend raising them up to ear level while seated, aimed-right at the listener but off-axis a little (5-10 degrees) toward the center of the room.  If you can provide a solid riser below the MEHs, that would help.  The rest of the bass response can be re-equalized below ~150-250 Hz to regain flat response--which is the reason why the design uses two 15" woofers--to be able to compensate for not having them in full room corners on the floor

 

Chris

  • Like 2
Link to comment
Share on other sites

2 minutes ago, Chris A said:

Ron, I'd recommend raising them up to ear level while seated, aimed-right at the listener but off-axis a little (5-10 degrees) toward the center of the room.  If you can provide a solid riser below the MEHs, that would help.  The rest of the bass response can be re-equalized below ~150-250 Hz to regain flat response--which is the reason why the design uses two 15" woofers--to be able to compensate for not having them in full room corners on the floor

 

Chris

Thanks Chris, 

When you are saying to angle them do you normally angle them to your ears or to a point behind the head?

 

I am also debating on putting them in the corners as I am thinking of doing a Auro3d setup, and they want a 30 degree per side angle...which puts them smack dab in the corners. How will this affect it?

Link to comment
Share on other sites

I would recommend toeing them in--in front of your listening position (not behind), but this requires that you clear the area of the front wall of acoustic reflections, i.e., keep the equipment off to one side of the room further back, or if the amplifiers/racks, etc. are between the loudspeakers, keep the equipment low--well below the horn mouths in order to suppress any early reflections.  [Most people that toe their loudspeaker in behind their listening positions often have too many acoustic reflections between the loudspeakers, thus forcing them to toe them in to behind the main listening position.]

 

Putting the K-402-MEHs in corners is just where they will perform their best (in terms of extended and flat bass performance), but a little absorption--about 2' on either side radially and the height of the horn mouths--on the front and side walls will keep the early midrange/upper midbass reflections minimized.  You'll get 10-20 Hz deeper response--and flatter response if they're placed in the corners, even if they are elevated above the floor in the corners.

 

Chris

  • Like 1
Link to comment
Share on other sites

9 minutes ago, Chris A said:

I would recommend toeing them in--in front of your listening position (not behind), but this requires that you clear the area of the front wall of acoustic reflections, i.e., keep the equipment off to one side of the room further back, or if the amplifiers/racks, etc. are between the loudspeakers, keep the equipment low--well below the horn mouths in order to suppress any early reflections.  [Most people that toe their loudspeaker in behind their listening positions often have too many acoustic reflections between the loudspeakers, thus forcing them to toe them in to behind the main listening position.]

 

Putting the K-402-MEHs in corners is just where they will perform their best (in terms of extended and flat bass performance), but a little absorption--about 2' on either side radially and the height of the horn mouths--on the front and side walls will keep the early midrange/upper midbass reflections minimized.  You'll get 10-20 Hz deeper response--and flatter response if they're placed in the corners, even if they are elevated above the floor in the corners.

 

Chris

Thanks Chris. I have attached a pic of the cabinet in the proposed position for the right channel. I am not sure if I should mount it that way since I would need to raise it to ear height...might be easier if it was mounted like yours if I can not angle

it.

 

Luckily the equipment will be on the loft, with B&O Icepower amps (bridge to mono, and running for cables) installed next to or in the cabinets. I have not decided what I am going to use for crossovers since you recommended against the minidsp ones.

20180716_120608.jpg

Link to comment
Share on other sites

On 1/18/2016 at 11:01 AM, Chris A said:

The current outside dimensions, including the box, are

 

27.25" H (69.92 cm) x 42.25" W(107.32 cm) x 23.63" D (60 cm) 

 

The horn itself is somewhat smaller, but you'll need a box of at least those dimensions anyway.  Of course, If you have relatively high ceilings, carpet on the floor and a narrow room, the speakers can be turned 90 degrees to cover 60 degrees horizontally, so their form factor is fairly close to that of a La Scala II--with (IMO) better than Jubilee imaging performance.

 

The La Scala dimensions (original La Scala, not the La Scala II) are:

 

35.5" H (90.17cm) x 23.75" W (60.33cm) x 24.5" D (62.23cm)

 

The conical horn doesn't have as high of an acoustic resistance (the key parameter for "horn loading efficiency") at low frequencies just above Fc that an exponential or hyperbolic profile will have, however, the flip side is that the conical actually has some resistance/reactance below Fc that the other profiles do not, and that is key to the current horn design performance.  Refer to Beranek for more information of conical vs. exponential vs. hyperbolic.  Its actually a fairly key part of why this design works the way that it does.

 

I'm retired only in the sense that I'm not on someone's payroll nowadays (by choice) and have a lot of latitude in spending my time.  The current New Center project is the fruit of some of that, as is the unmastering stuff and other audio adventures, in addition to work doing pro bono related to my prior chosen profession.   The audio portion has been very easy for me to focus on of late.

 

Chris

I hope my dimensions are ok... If not I will repurpose the cabinet to the garage. Remember O am using the EV DH1As.

 

26 5/8" deep

26" x 40 1/4"

Link to comment
Share on other sites

You might talk to @MetropolisLakeOutfitters about the miniDSP 2x4 HD crossovers.  He's apparently got experience with them and the Xilicas, etc., so he can give you a better idea of their usefulness in a Jubilee-like application.  I've heard that the noise levels are higher, so the question is--"how much higher?".  Understand that one Xilica XP-8080 can go a long way toward having just one crossover in the setup--perhaps miniDSPs can be used on the surround channels if you're bi-amping those.  I use only the one XP-8080 for the whole 5-channel array (bi-amping the front three, mono-amping two surrounding Cornwalls).  When you look at the price of the XP-8080 vs. at least four miniDSP 2x4 HDs, you might find that the Xilica is actually less money.

  • Like 2
Link to comment
Share on other sites

I'll have to do a layout to answer your box size question.  I had no problem with the 15" cast frame woofers from Crites using a KPT-305 box: there's plenty of clearance for the woofers.  The problem is the depth of the EV DH1A compression drivers vs. the K-69-A that I'm currently using. The box needs to be slightly deeper than the KPT-305 box -- about 2" deeper.

  • Like 1
Link to comment
Share on other sites

  • 2 weeks later...

I do know that the balanced MiniDSP 2x4 is noisier than the unbalanced, as we had hiss with my JBLS before we went to the unbalanced. I had a xilica 3060 before, and it was great. I guess I will have to look for another 3060.

You might talk to [mention=59101]MetropolisLakeOutfitters[/mention] about the miniDSP 2x4 HD crossovers.  He's apparently got experience with them and the Xilicas, etc., so he can give you a better idea of their usefulness in a Jubilee-like application.  I've heard that the noise levels are higher, so the question is--"how much higher?".  Understand that one Xilica XP-8080 can go a long way toward having just one crossover in the setup--perhaps miniDSPs can be used on the surround channels if you're bi-amping those.  I use only the one XP-8080 for the whole 5-channel array (bi-amping the front three, mono-amping two surrounding Cornwalls).  When you look at the price of the XP-8080 vs. at least four miniDSP 2x4 HDs, you might find that the Xilica is actually less money.


Sent from my SM-T550 using Tapatalk

Link to comment
Share on other sites

I've kept the '79 Cornwalls with Crites CT125 tweeters for several years now.  I have these on two channels of the Xilica and have EQed them flat (which is important when using the CT125, which a little less sensitive than the K-77 tweeters).  I haven't moved the tweeters to the back of the cabinets yet to time align them, but when I get a round tuit, I'll do that, too.  I need to make little mounting baffles for this (more on this subject below).  Getting the tweeters physically time aligned pretty much makes the Cornwall time aligned overall since the midrange horn-woofer is only about a wavelength from being aligned. 

 

I need to move a table saw and other power tools into my garage that I've inherited, but first, "stuff" has to leave...

JET-708677PK__1.jpg

Chris

  • Like 2
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...