# Matching Polar Response at the Crossover Frequency



## SSSnake (Mar 8, 2007)

I am about to put a new system in my car and I am debating horns vs direct radiators. I have had both in previous vehicles so I am aware of most of the advantages and disadvantages associated with horns. After years trying to get the sound I want in a car, I am firmly a believer that you need to be able to match the power response/polars at the crossover frequency to get the best response at multiple listening positions (Geddes, Wehmeyer, and others have preached this for a while now). This makes sense to me and does line up with my experiences listening to the better vehicles. 

With the typical horn installs I see the, mid/midbass is in the kickpanel and the horn is perpendicular to the kickpanel and parallel with the firewall. Given the typical 1khz crossover frequency, 8" mid/midbass and the horn driver on tweet, this would seem to create a fairly large directivity/polar response mismatch at the crossover frequency. Am I missing something or is this a fairly accurate assessment? Is there a horn manufacturer that builds a horn body that is suited to mounting at about 30 degrees off of the kickpanel so that you can get the horn and the mid/midbass in the same plane to match directivity?

TIA


----------



## Elgrosso (Jun 15, 2013)

I believe that the match for a typical 2 way in kick is pretty good.

At these low frequencies (800/1K), where the woofer is below beaming, its angle has no impact.
Since we want the voice-coil to be placed as far laterally as possible for width cues, it has to be placed perpendicular to us most of the time.
The footwell shape/material probably has more impact on its response than anything else here.

For the horn, if you check an ES it's clearly visible that in fact they are what you're describing, I mean 30 or more 60 degrees angled horns, almost like a klipsch K1000.
But since the horn has to be integrated in the dash, an extension has been added on one side for the mouth to reach the edge of the dash that is facing us, for a smooth transition.
I doubt this added asymmetric part plays a big role in the directivity, maybe just for smoothing diffraction etc (Eric has said few times that it can be cut a bit if needed).
So the "main" part of the horn is actually placed at xx degrees. (maybe 30 for the full body and 60 for the mini, don't remember), allowing to place it as laterally as possible again for width cues, and also very close to the woofer.


----------



## Eric Stevens (Dec 29, 2007)

At 800 Hz the polar response of an 8" will very wide, For the Stevens Audio HLCD t will be vaery wie also. So I think from the matching polar response in the car they do very good. The HLCD directivity is not what common sense will lead you to believe. They operate somewhat like an array and will have a very broad vertical response pattern and a controlled horizontal response pattern.

The importance of matching polar response in the car is going to be diminished compared to a home audio or other system in a large or larger space. I think more important is the direct versus reflected energy in time arrival and amplitude.


----------



## SSSnake (Mar 8, 2007)

> At these low frequencies (800/1K), where the woofer is below beaming, its angle has no impact.


For me it is easier to talk about directivity using ka maps. This lets you visualize the variation in db very easily. ka is calculated as (speed of sound / (diameter*pi) or in this case (1087*12/8pi) which equals 520 hz. This is the highest frequency that primarily omnidirectional (slight attenuation at 90 degrees but nothing worth mentioning). So for a ka = 2 the frequency doubles to 1040 hz. The attached image contains the ka maps.

So with the 8" mounted flush in the kicks you are likely looking at about a 4db difference from the drivers seat to the passenger seat (driver seat at 90 degrees and the passenger seat at around 35 to 40 degrees - ignoring reflections off of the center console and etc.) While not a huge amount of directivity in the 8" it certainly does not appear to be omnidirectional at this freq.

From a Youtube video, that I can't find, I thought that Matt Borgardt mentioned the ID full body horns had around a 60 degree coverage angle (assume the outside of the car is a plane at 0 degrees). Which makes sense for directing the sound toward the opposite seat and away from the console.

I say all of this to get to this point. If you can't put the midbasses anywhere but the kicks (e.g. not in the firewall/floor which would keep them in roughly the same plane as the horn) would you be better running a three way with a smaller mid to bridge the gap between the midbass and the horn?


----------



## SSSnake (Mar 8, 2007)

> The importance of matching polar response in the car is going to be diminished compared to a home audio or other system in a large or larger space. I think more important is the direct versus reflected energy in time arrival and amplitude.


I agree about the "ideal" (ideal in this case being what you would measure in an anechoic chamber) polar response in the car not being AS important because we have so much interference in the near field. However, it always seems to complicate things when the "ideal" polars are poor to begin with. We hear so much reflected sound in a car and the reflections are so complex that you get very unpredictable response curves that tend vary widely with the location of the listener (which I know you are aware of). It seems to me that this is only made worse/more complicated when the "ideal" polars are poor. 

The main reason I am considering a horn for the highs in my car speaks to your second point - the reduction in reflected energy (amplitude). With horns, which use directivity to their advantage, the reflected energy tends to be greatly reduced (at least in the very near field). I typically prefer this sound versus what i get with direct radiators. However, the path lengths for a dash mounted mid and the horns in my car are fairly similar so there is no real advantage to PLDs with the horn in my car.

So what it all boils down to for me is: Will the reduction in reflected energy at higher frequencies be worth the problems I have had in the past matching the horn to a B&C 8NDL51 mounted in the kicks? For whatever reason I just never could get the sound in the crossover region to sound the way I wanted. For me issues very close to the middle of the human vocal range are particularly annoying.


----------



## ErinH (Feb 14, 2007)

Knowing that a driver beams at about 1/2 it's (effective) diameter you can figure an 8" will begin it's descent in to more directional sound around 850hz and a 10" at 675hz. out of those two, then, the 8" seems the better "match" in terms of mating a driver to another with desired crossover point at 1khz. I don't know if I'd worry too much about 150hz and change but with a 10" I think the 300hz gap might be more concerning. 

My main concern is mating a large circular radiating driver to a smaller, intentionally directive driver/horn combo. With the typical car audio horn bodies you have a wider directional coverage vertically than you do horizontally and those polar differences can be quite significant. I did a "study" on the old Speakerworks USD CD/horn(waveguide) a while back, which can be found here:
http://medleysmusings.com/blast-from-the-past-speakerworksusd-audio-a-6-0-testing/


Specifically, when you compare the polar response of the horizontal (1st picture) vs the vertical polar (2nd picture), you can more easily visualize the stark contrast. 





















As you can see, where you are from top to bottom of that horn isn't as drastic from one spot to another. However, when you look at the horizontal response, the difference from side to side (-180 degrees to +180 degrees) is very, very different. Not only that the response within half-sides isn't too great, either. I know this is part of the design but seeing it really helps to paint the picture. I also realize this design is oooooooollllllddddd... but the overall picture it paints is telling of the behavior of similarly-designed horns with this type of rectangular geometry.

I often wonder if this difference in vertical and horizontal patterns and/or if this interaction with a cone driver which is (mostly) omnidirectional is the reason it's so hard to get a "standard" car audio horn to not be so localizable. ** as an aside, I'll add I've heard many, many car systems with these kind of horns and only one didn't exhibit this ... tradeoff. don't shoot the messenger **



Not sure if that really tells you anything you didn't already know but hopefully, if nothing else, the data from that test helps you draw some meaningful assumptions about similar designs and helps in implementing them in to your system. 

Edit: Also realize when looking at the data the horns were measured free-air. The consensus is these things are designed for a dash to help extend the "waveguide effect". Regardless of that, you can still glean a lot of useful information from seeing the "out of car" response; the same as you would any other speaker (many cases can be made for horn-loading other drivers without a waveguide already attached to them).


----------



## SSSnake (Mar 8, 2007)

I forgot you did that on your site. I went back and reviewed. I wish you had done this analysis on the ID full bodies 

The horizontal to vertical mismatch in directivity is necessary to keep the horns from imaging at your knees. How this effects the radiation pattern when you have both a vertical and horizontal offset (like in the passenger seat) has caused me some concern as well but I don't see any other way to do this in a car...

I love the dynamics of horns and the elimination of some of the early reflections. I just wish I could gt those with a smoother transition to the direct radiator.

Thanks all for the input.


----------



## ErinH (Feb 14, 2007)

SSSnake said:


> The horizontal to vertical mismatch in directivity is necessary to keep the horns from imaging at your knees.



Understood. But I have to wonder if that was the purpose of the design or a coincident benefit of them simply being designed to not be obtrusive to the driver/passenger legroom.


----------



## Elgrosso (Jun 15, 2013)

SSSnake said:


> For me it is easier to talk about directivity using ka maps. This lets you visualize the variation in db very easily. ka is calculated as (speed of sound / (diameter*pi) or in this case (1087*12/8pi) which equals 520 hz. This is the highest frequency that primarily omnidirectional (slight attenuation at 90 degrees but nothing worth mentioning). So for a ka = 2 the frequency doubles to 1040 hz. The attached image contains the ka maps.
> 
> So with the 8" mounted flush in the kicks you are likely looking at about a 4db difference from the drivers seat to the passenger seat (driver seat at 90 degrees and the passenger seat at around 35 to 40 degrees - ignoring reflections off of the center console and etc.) While not a huge amount of directivity in the 8" it certainly does not appear to be omnidirectional at this freq.
> 
> ...


I see, maybe I'm just used to 30/60 degrees and rarely use 90 (mine are at 45) but still I doubt it’s a big deal here, I would imagine the footwell shape to have greater influence on the response + of course the cabin once the soundwave is out.
And if deep in the footwell then the beaming issue is probably just masked or cancelled by all reflections. 
I mean we definitely get crazy woofer measurements in multiple points starting above the Schroeder frequency while still below the beaming anyway.

But about the rest just to say that I'm on the same journey, balancing horns VS regular drivers and of course it's a lot question of dispersion pattern. Right now I'm going to use domes, with waveguides if possible for a better balance direct/reflected sound.

I'm surprised you didn't get great results with your setup.
I always preferred higher near 1.6Khz when I had my 2 way. Don’t you think the problem could have come from the horn? like not loading properly that low or maybe even the CD used.

About your question on the 3 way, my last setup was a sort of WTM, far from perfect for Xo interactions.
Horn at the edge of the dash, midbass deep in footwell and mid flat in door kind of apart, playing into beaming quite a bit (around 3Khz or more).
And while I had strange artefact on the stage I'm guessing due to interaction between midrange and horns, it was still the most enjoyable I ever had.


----------



## Eric Stevens (Dec 29, 2007)

I dont have the time to formulate a complete response but would like to point out a topic for discussion and consideration.

Polar plots as you are referring are based upon radiation in a 1/2 space environment, the automobile interior is, anything and everything but 1/2 space, and this will change the polar response and energy distribution.


----------



## ErinH (Feb 14, 2007)

Eric Stevens said:


> I dont have the time to formulate a complete response but would like to point out a topic for discussion and consideration.
> 
> Polar plots as you are referring are based upon radiation in a 1/2 space environment, the automobile interior is, anything and everything but 1/2 space, and this will change the polar response and energy distribution.


The same as it would for any speaker. (As you know) Polar plots are good to see the behavior of the speaker off-axis, especially in a highly reflective environment where there are two main impacts: 1) mating one driver to another driver and 2) the high frequency driver. 

In regards to the latter, I prefer wide (omnidirectional) dispersion over narrow dispersion for the exact reasons you mentioned; when the polar doesn't have a smooth, reliable contour the energy reflected back will hurt the direct sound significantly more than it would otherwise. Then there's the aspect of narrowing dispersion resulting in a lessened sense of "space" in the listening environment which leads to increased focus but tiny images and no real sense of being in a large room (when the recording permits). Of course, this particular aspect is really preference and one that can have merits either way depending on your point of view/preference. Then there's the former aspect regarding mating the directivity index of the two drivers so the wavefront is as close to "one" as it can be. When the DI increases at the crossover point you often wind up getting a "yea, the speaker is right there" effect as well as simply having a "hole" in the response.

Certainly there's more to the discussion but I don't want to beat a dead horse here, either. In a nutshell, though, the reasons above are why I put a lot of stock in to viewing polar plots; especially in cases where the driver will be used outside the beaming point. I don't _know_ if you were implying polars matter less because of the car environment but that's how I read it and why I wanted to provide a counter. If that wasn't what you were implying then I apologize in advance.


----------



## Elgrosso (Jun 15, 2013)

I guess it mostly depends of the drivers placement.
Polars are probably more useful when all drivers are close and on the same plan as we can expect a somewhat similar cabin effect on these drivers.
But less useful/predictable if all drivers are spreaded out and with different angles.
So a poor polar response does not always correlate to a poor power response.


----------



## thehatedguy (May 4, 2007)

Timely as I start installing my 10s and minihorns.


----------



## ErinH (Feb 14, 2007)

Elgrosso said:


> So a poor polar response does not always correlate to a poor power response.


There is no situation where a poor polar response makes a good power response. Axial measurements directly influence the in-position response (what I assume you're referring to as the polar response). The car isn't going to somehow "fill in the gaps" for a speaker with poor polar response, certainly not as a 'one size fits all' case since every car and install is different on our end of car audio.

To take that even further... think about what you're proposing ... someone would have to have anechoic measurements of a speaker and know what the car is doing, then design a speaker to perform in the exact opposite manner the car worsens the response. No one is doing that. If anyone were to, certainly it would be OEMs designing their factory systems in this manner. I've never seen anyone provide evidence that OEMs do anything more than DSP correction.


----------



## Holmz (Jul 12, 2017)

The driver and passenger are usually in well known locations in a car, so there are. 1 or two places where we would want to be inside of a beam rather than outside of it.

If the majority of energy coming out of the horns is not "being wasted" towards other parts and reflecting off of the interior, then the more directive horns should be better than a conventional driver(??) minimising reflections, and hence to some degree in EQ(??)


----------



## SPLEclipse (Aug 17, 2012)

Holmz said:


> The driver and passenger are usually in well known locations in a car, so there are. 1 or two places where we would want to be inside of a beam rather than outside of it.
> 
> If the majority of energy coming out of the horns is not "being wasted" towards other parts and reflecting off of the interior, then the more directive horns should be better than a conventional driver(??) minimising reflections, and hence to some degree in EQ(??)


What Erin is getting at is that having certain areas of the FR where there's a lot of reflection (wide dispersion) and certain areas where there's little reflection (narrow dispersion) leads to changes not only in the FR at your ear but also causes localization issues. Since dispersion tends to narrow around the crossover point between two speakers, this makes things more difficult. I guess ideally you would want both the passenger and driver to be within a very narrow directivity window with no reflection anywhere in the spectrum, but that's not possible, so having reflection at every point in the spectrum is better than a "lumpy" polar response.


----------



## Elgrosso (Jun 15, 2013)

ErinH said:


> There is no situation where a poor polar response makes a good power response. Axial measurements directly influence the in-position response (what I assume you're referring to as the polar response). The car isn't going to somehow "fill in the gaps" for a speaker with poor polar response, certainly not as a 'one size fits all' case since every car and install is different on our end of car audio.



Sur not one size would not fit all that’s why the «*not always*», and this correlation is probably proven most of the time.
But I was thinking of a case where, since cabin reflections are so chaotic, a certain frequency could be reinforced at a certain distance off-axis while not reinforced at the same distance on-axis. So the total sound power could appear smoother than in an anechoic chamber.
But maybe it's not correct to say sound power here since it's in a car cabin, is it only in anechoic room according to Harman definition?
I might mix the SPFR from Raimonds that is measured in situ at all distances from the «*speaker*».




ErinH said:


> To take that even further... think about what you're proposing ... someone would have to have anechoic measurements of a speaker and know what the car is doing, then design a speaker to perform in the exact opposite manner the car worsens the response. No one is doing that. If anyone were to, certainly it would be OEMs designing their factory systems in this manner. I've never seen anyone provide evidence that OEMs do anything more than DSP correction.


Does not sound so crazy, I remember an old discussion with Niick, where he wanted to measure the entire cabin effect on all drivers. For easier driver selection or just future tunes and tests.


----------



## SSSnake (Mar 8, 2007)

I am glad to see this topic heated up over the weekend. Thanks to all that have contributed.



> I see, maybe I'm just used to 30/60 degrees and rarely use 90 (mine are at 45) but still I doubt it’s a big deal here, I would imagine the footwell shape to have greater influence on the response + of course the cabin once the soundwave is out.


A LOT of the older horn cars had the mid/midbasses flushed into the kicks leaving them at 90 degrees off axis for the near seat. I have a man pedal in my car so before I removed the parking brake pedal I flushed mine into the kicks. I will be moving them more on axis in my latest installation (likely 45 to 60 degrees off axis). The other reason I brought up having the horn and the mid/midbass in the same plane was installs similar to Eric's Sable with mid/midbasses in the floor facing the driver/passenger. It would seem the polars would match up better in this configuration.



> So a poor polar response does not always correlate to a poor power response.


While I do acknowledge this is theoretically possible I have never seen this in any installation. IMO the environment is so highly reflective and the reflections so close to the sound origin that I am unsure actual measurements will yield much usable information (at least not with most peoples measurement tools). A highly detailed physics based simulation might yield more usable results but that is beyond the capabilities of most on this forum (I say this having 25 years experience in M&S). Without the ability to accurately characterize the direct vs reflected energy I am not sure how you would design a system that made up for poor polar response of the drivers themselves.



> If the majority of energy coming out of the horns is not "being wasted" towards other parts and reflecting off of the interior, then the more directive horns should be better than a conventional driver(??) minimising reflections, and hence to some degree in EQ(??)


This line of thinking is what drives me toward horns but also tortures me when I have them. We know there is controlled horizontal dispersion. We also know there is very little directivity in the vertical axis so that: 1.)more than just our kneecaps can enjoy the music and 2.)we can fit the horns into the under-dash area. So what happens to the response at the opposite listening position (e.g. driver side horn passenger side listening position). From memory (I did measurements several years back) it was a mix of controlled dispersion and uncontrolled dispersion. When this is the case the FR at each listening position for the same pair of drivers will be different and I don't see how you can EQ this difference away for both seats. How big a deal is this? I was hoping it would be much less of an issue if I could get the initial polars to match a little more closely.

All of the above is based upon what I heard in my car and what I believe I had heard in others with horns. While I did hear the GN in my youth I have no idea how I would assess the sound now. Back then it was head and shoulders above everything I had heard. Horn cars tend to be few and far between around here and I have to admit I am not going out to IASCA/MECA events these days so my sample size is admittedly small. What I was hoping and continue to hope is there is something that I am missing and once I understand the implementation of horns in a car then I can do better than my last horn install (because God I do love the dynamics). If I can't figure out what I am doing wrong, I will be going with direct radiators (which is where I am now leaning).


----------



## thehatedguy (May 4, 2007)

Here is my passenger's side that I did this weekend. JBL 2012h in the floor maybe like you were talking about.


----------



## SSSnake (Mar 8, 2007)

Yep. That is it. Have you had the same driver in the kicks (I doubt it as those are pretty large but I needed to ask)? I know you likely don't have much listening time on it but I was wondering if you could compare/contrast the sound from two different mounting locations.


----------



## thehatedguy (May 4, 2007)

I haven't had a working stereo in about 4.5 years in this car, and just got that side fabricated yesterday...so no listening impressions yet. I was going to do some JBL 2119s that I have, and after opening up a hole I found that 10s could fit as easy as the 8s. These 2012hs have a motor that is about 8" around and limited some aiming options. 

But with a Sd of roughly 8" narrowing shouldn't be much of an issue around 1200 hertz. And if it is, I have some ideas on how to fix it and make grills at the same time- take a look at the JBL EON615 and 612 for where I might be heading.

And something else a lot of people don't talk about much is roughly matching the area of the horn/waveguide mouth/exit to the Sd of the speaker mating to it. That seems to smooth the transition too. Geddes talked about that in the past.


----------



## SSSnake (Mar 8, 2007)

Yeah I feel you on the no working stereo for a while. I have been working performance mods and left the stereo alone as i was integrating a tablet PC. Long story short, issues with USB device handling left me without the PC or the stereo (was going to use the PC as the HU) for about three or four years. So I grabbed an HU that would do most everything I needed from a USB standpoint and had an HDMI in. Doing a PC update the tablet went black and now won't power on. Too much time wasted so I am now moving on.


I have seen Geddes quoted as matching the area AND/OR having the horn area exceed the cone area slightly (e.g. 12" waveguide mated to a 10" driver). That and the 3D printer here at work had me thinking about some custom horns/waveguides as well.


----------



## Elgrosso (Jun 15, 2013)

thehatedguy said:


> I haven't had a working stereo in about 4.5 years in this car, and just got that side fabricated yesterday...so no listening impressions yet. I was going to do some JBL 2119s that I have, and after opening up a hole I found that 10s could fit as easy as the 8s. These 2012hs have a motor that is about 8" around and limited some aiming options.
> 
> But with a Sd of roughly 8" narrowing shouldn't be much of an issue around 1200 hertz. And if it is, I have some ideas on how to fix it and make grills at the same time- take a look at the JBL EON615 and 612 for where I might be heading.
> 
> And something else a lot of people don't talk about much is roughly matching the area of the horn/waveguide mouth/exit to the Sd of the speaker mating to it. That seems to smooth the transition too. Geddes talked about that in the past.


Oh yeah the Eon waveguide! I’ve been trying to find a pair used or even through my friends at HK... no luck for now. I was curious to test them on my midbass like you, would just need to modify a bit the 12 to work on a 10.
I was thinking about helping crossing much higher, so widening the dispersion.
But I guess it could be used in the opposite way like for SSSnake, to match the horn dispersion at 800Hz (tall and angled).

But who knows the exact dispersion pattern of a full body, in a car? Well of course Eric probably...
I mean I have ideas but still can't visualize it properly, horizontal/vertical pattern flip with which transitions, moving center, delays etc
One day I'll take time for measurements or maybe I'll even ask a friend to create a 3d for some sort of simulations

https://i.imgur.com/c7UjQWd.mp4


----------



## SSSnake (Mar 8, 2007)

> https://i.imgur.com/c7UjQWd.mp4


Neat idea (and one i hadn't thought of) and it does show the horn directing sound more toward the opposite listener but I would guess the water is adhering to the body of the horn too much for it to be very representative. But I could be wrong... I also wonder how different it would look on the full body horns. The CD enters the top not the side on the full body so I would expect things to look substantially different with water.


----------



## Eric Stevens (Dec 29, 2007)

SSSnake said:


> Neat idea (and one i hadn't thought of) and it does show the horn directing sound more toward the opposite listener but I would guess the water is adhering to the body of the horn too much for it to be very representative. But I could be wrong... I also wonder how different it would look on the full body horns. The CD enters the top not the side on the full body so I would expect things to look substantially different with water.


No the sound in the horn as it exits the compression driver is going to act more like a liquid and has no directional characteristics until exiting the mouth or as it exits the mouth. Both have a 45 degree reflector which reconstructs the wavefront at 90 degrees so they will work in a similar fashion.

The full size will be different because the angles are different and the mouth size larger so it has directivity to a lower frequency.

I think your issues in the crossover range were caused by factors other than polar response. I have always found it easy to blend the horns with the midnass.


----------



## Elgrosso (Jun 15, 2013)

SSSnake said:


> Neat idea (and one i hadn't thought of) and it does show the horn directing sound more toward the opposite listener but I would guess the water is adhering to the body of the horn too much for it to be very representative. But I could be wrong... I also wonder how different it would look on the full body horns. The CD enters the top not the side on the full body so I would expect things to look substantially different with water.


Yes I was sanding them so had everything around to try. It’s sure not very representative as it really depends of the pressure/angle of the hose but it illustrates the idea and was fun, I was surprised it worked that much in fact.


----------



## SSSnake (Mar 8, 2007)

> I think your issues in the crossover range were caused by factors other than polar response. I have always found it easy to blend the horns with the midnass.


It very well could be. Any thoughts about what might be causing the issues or things to look for?

BTW - please don't take this as an attack on your products (past or present). It is CERTAINLY not intended that way. I have had the pleasure of speaking with you a couple of times on the phone (years back) and have always found you extremely helpful.


----------



## Eric Stevens (Dec 29, 2007)

SSSnake said:


> It very well could be. Any thoughts about what might be causing the issues or things to look for?
> 
> BTW - please don't take this as an attack on your products (past or present). It is CERTAINLY not intended that way. I have had the pleasure of speaking with you a couple of times on the phone (years back) and have always found you extremely helpful.


I dont take it as an attack or questioning of the product in any way.

To help isolate what the issue is I need a good description. With that I can analyze and give suggestions or say it's "xxxxxxx"


----------



## SSSnake (Mar 8, 2007)

When playing tones around the xover freq the image always seemed to lose focus and move. The FR averaged around a half dozen measurements locations was fairly smooth (not great but not horrible and it did seem to change with measurement location more than I would like). The measurement locations were two rows of three measurements. Measurements in each row were spaced 6" around the center of the listener's head. The second row was 6" below the first with similar horizontal spacing. Measurement tool was either REW or TrueRTA (usually a combination of both). Mics were Behringer ECM8000s (they are uncalibrated but I have two so that if I get screwy with one results I can compare against the other mic). Nothing clipping and reasonable listening levels. I never really got the system good enough to check linearity... 

Horns were mounted snugly against an damped plywood panel that replaced the stock underdash cover. They were as far back and as wide as I could get them and they were symmetrically mounted (wrt left and right sides). The flat portion of the horn that points to the opposite listening position was extended to butt against the center console. I tried adding towels to the center console and even rebuilt the center console at one point so that it was lower than the seats in hopes of helping the horn blend with the midbass (B&C 8NDL51). I tried reticulated foam (Geddes mentioned it at one time and then I think he just changed to open cell foam) to help as well with no significant impact on the sound.

Beyond this the highs suffered from the typical rainbowing. I never ran supertweeters to help with this or top end extension (which I thought was good enough after EQ).

All of this was run off of whatever Alpine HU I had at the time, the Alpine H701, and whatever class A/B amps I was running at the time (MTX for quite a while but Zapcos were used originally and later I think I had a JL amp or two on them). The xovers were almost always 24db/octave. Polarity was inverted a couple of times to see if that may be the issue but it was not. I did try other xover slopes but always seemed to come back to 24db/octave. I wanted to run the xover freq down to 750hz but it seemed to get a little honky (for lack of a better term) so i typically settled on 1khz.


----------



## thehatedguy (May 4, 2007)

Mini or big bodies?


----------



## Eric Stevens (Dec 29, 2007)

SSSnake said:


> When playing tones around the xover freq the image always seemed to lose focus and move. The FR averaged around a half dozen measurements locations was fairly smooth (not great but not horrible and it did seem to change with measurement location more than I would like). The measurement locations were two rows of three measurements. Measurements in each row were spaced 6" around the center of the listener's head. The second row was 6" below the first with similar horizontal spacing. Measurement tool was either REW or TrueRTA (usually a combination of both). Mics were Behringer ECM8000s (they are uncalibrated but I have two so that if I get screwy with one results I can compare against the other mic). Nothing clipping and reasonable listening levels. I never really got the system good enough to check linearity...
> 
> Horns were mounted snugly against an damped plywood panel that replaced the stock underdash cover. They were as far back and as wide as I could get them and they were symmetrically mounted (wrt left and right sides). The flat portion of the horn that points to the opposite listening position was extended to butt against the center console. I tried adding towels to the center console and even rebuilt the center console at one point so that it was lower than the seats in hopes of helping the horn blend with the midbass (B&C 8NDL51). I tried reticulated foam (Geddes mentioned it at one time and then I think he just changed to open cell foam) to help as well with no significant impact on the sound.
> 
> ...


Sounds like you had a lot of things done right. 

I have question about how the equalization was set in the 400 to 1200Hz range. I recommend no more than 2 or possibly 3 dB of boost at any frequency between 400 and 800 Hz. This is an area whee there are destructive cancelations and you can EQ so it appears flat an RTA but it really isnt. You are better off leaving the dips that appear on an RTA between 400 to 800 hz alone and resist the urge to boost them, it will sound better in every way. This frequency range will measure different in different locations around the listening area, and the cause is the environment.

Rainbow is localization to the speakers and happens when its not imaging as well as it should. Some related things: when the mid is not in phase with the hlcd through the crossover it will cause localization, to correct this I use signal delays as a phase adjustment, I work on one side at a time with the other muted and increase the delay time on the midbass until I get a spoken voice as high as possible.


----------



## SSSnake (Mar 8, 2007)

> Mini or big bodies?


Big. As a matter of fact they were the old fiberglass big bodies. 

BTW - did the old big bodies have the reflector that Eric mentioned earlier? For some reason I don't remember seeing it.



> I have question about how the equalization was set in the 400 to 1200Hz range. I recommend no more than 2 or possibly 3 dB of boost at any frequency between 400 and 800 Hz. This is an area whee there are destructive cancelations and you can EQ so it appears flat an RTA but it really isnt. You are better off leaving the dips that appear on an RTA between 400 to 800 hz alone and resist the urge to boost them, it will sound better in every way. This frequency range will measure different in different locations around the listening area, and the cause is the environment.


Cardinal sin of equalization - boosting a null. So I don't (I have tried only to find that you never really get it to a flat FR and you get a ton of unwanted boost in the adjacent frequencies AND that null is usually location dependent - move your head about six inches and watch the null move in freq). I also try not to put a boost very close to a cut - sometimes it works OK but usually not. If you turn down the smoothing you usually see there is something going on there that you won't be able to eq away. IMO this range (400-800hz) and the transition between sub and midbass is the hardest to get right in a car. So... I may not have gotten it right but I did spend a LOT of time in both areas.

The rainbowing was really only apparent at higher freqs (around 4khz and above). It seemed to get worse as frequency increased. The vocals were actually imaging pretty high (just slightly below the rearview mirror for stereo content). Most folks thought I had dash mounted speakers. When the frequency went up and/or the content shifted to a single side the image would tend to pull down to the dash or even a little below. However, I did wonder if the phasing was off at the xover freqs. In my installation the midbasses were the furthest from the listening positions. So the horns got more TA than the midbasses to account for the differences in physical location. I tried adding some TA to the midbasses and taking some out of the horns ( I know - same net effect) but maybe I didn't get aggressive enough.

Thanks for all of the advice. I think my path forward will allow me to try the horns for a while and see what I can get. Armed with this new information, if I get the issues worked out I will keep them. If not, I will go back to direct radiators. It shouldn't be that time consuming given my build plans.


----------



## Elgrosso (Jun 15, 2013)

SSSnake said:


> ...
> The rainbowing was really only apparent at higher freqs (around 4khz and above). It seemed to get worse as frequency increased...


This is high above the XO point, you think it could still have this effect?
Just curious, I wonder if it could be the loss of vertical directivity that must start around this area (I thought more 6Khz).

Would explain, but I never suffered from this, while I did suffer of lows too low sometime on some tracks. But maybe I didn't pay enough attention.
I remember sometime being surprised by the amount of steered highs «*virtually*» coming from the bottom pillar/corner dash.


----------



## Patrick Bateman (Sep 11, 2006)

Why don't you just use a Unity Horn? It solves all of these issues. I'm covering six octaves from a waveguide that's no bigger than anyone else's HLCDs.

If you want me to print a set, LMK. 



























My latest design is specifically optimized for the Celestion CDX1-1425, the same driver used in EAW's "ANYA" speaker









The midranges that I'm using are the same that were used in the SPL-TD1 prosound speaker. (Misco JC5TRF-B)

It gets loud


----------



## SSSnake (Mar 8, 2007)

> This is high above the XO point, you think it could still have this effect?
> Just curious, I wonder if it could be the loss of vertical directivity that must start around this area (I thought more 6Khz).


It is funny that you put 6khz as the first time I typed the thread I put 6khz. It has been a while since I had these in my vehicle so it could definitely have started at that point vice the 4khz I mentioned.

It would surprise me if it was a xover phasing issue but I have been surprised before. Given the time that has passed since my last horn car I feel like I need to try it again particularly given the information concerning the way Eric time aligns the midbass to the horn. I could live with the rainbow but the weirdness at the xover freq drove me nuts (once I got over being impressed by the dynamics).



> Why don't you just use a Unity Horn? It solves all of these issues. I'm covering six octaves from a waveguide that's no bigger than anyone else's HLCDs


I would love to play with one. Instead of you printing it and shipping to me why don't you just send me the stl and source file. I have access to a 3D printer. I have never printed anything but I have a few guys that would be willing to assist. 

I noticed you are printing your horns in multiple pieces. Is that because you are experiencing warping of larger parts as they cool or because your printer can't print the full size of the horns? If it is the latter I may be able to print you a one piece part. We have a pretty decent size printer that was open frame. We experienced warping of larger parts originally then built a plexiglass box with a port for a heat gun. We preheat the air in the box prior to printing and this has helped us dramatically with elimination of warping.


----------



## oabeieo (Feb 22, 2015)

Wow great thread sssnake! 
Fun read, 

I liked what Erin H was eluding to quite a bit actually, 

But to throw my .02c in, 

I would suggest there isn’t one perfect answer. 

I think it starts with how uniform you want the response to be on both sides at what magnitude? How loud you want this thing to be? 

If we’re talking 100-105db both sides at a1khz crossing (LR) with an 8” and a big ES horn I don’t see any issues. I just finished a BMW (I’ll post pics in install pics of horns after this post) with ES CompNeo on minis and ES MB-8s in kicks on a F30 (E93) . 

It was actually kinda hard to not screw it up. At crossover dispersion was wide on both the horn and the MB , with no DSP just crossovers it sounded listenable and the relative polarity track worked great on both sides......

What I’m getting at is transfer function. As long as both sides of the car have very similar PLDs it’s really a breeze. A lot of cars give the passenger a LOT less room than the driver , and when sitting in the passenger seat I’ve seen the passenger have more exacerbated PLDs than the driver, lower dash height seat position relative to placement. Cars are very far from symmetry. So in those cases moving the horn on the driver side a forward or push passsanger side back can mitigate it some, but one only has maybe 2” or 3” before causing uniformities in the transfer function. 

Than the volume , the louder you go the more compound some reflections will be (and at crossover I’ve always moved the horn up to 1.6khz to 2khz to get a more uniform response on both sides) even the the 8 will begin narrowing, the narrowing isn’t always bad when it’s in crossover and you have even PLDs and even transfer function. 

Really some very minor convolution can easily fix these small problems with kick panel mounted drivers quite nicely. 

I totally understand the question tho, having a stage that starts to pull one direction or the other or simply start to breakup cohesion between seats can be very annoying, again raising the crossover always seems to stop any awkward pattern flip because of imperfections in transfer functions.


----------



## Reece514 (Mar 11, 2013)

thehatedguy said:


> Here is my passenger's side that I did this weekend. JBL 2012h in the floor maybe like you were talking about.


Have you listened to this yet? How are you protecting the drivers from the back? Did you cut the floor or did you have it done?

This set-up is badass!!! I wanna try it, but would like to hear your opinions.


----------



## Jscoyne2 (Oct 29, 2014)

Elgrosso said:


> https://i.imgur.com/c7UjQWd.mp4


Lolll


----------

