# Midbass cancellation, options? Angle upwards?



## bnae38 (Oct 3, 2015)

Been tuning hard for the better part of a year now. Getting to the point where I'm fairly content with the sound of my system, but there is one major obstacle left....










I have all drivers eq'd to a house curve, but with both the left and right midbass playing together (and nothing else), they cancel. I've checked the phase on individual sweeps of each and they are, in fact, about 180 degrees apart at those points.

I'm guessing it's because of the center console and reflections; the odd thing is I can eq (mostly down) and flatten each out individually, but combine the left and right midbass and there are a couple nasty dips.. 

Flipping phase of one or the other "fixes" this, but breaks a lot more than it fixes. See below.










Gear in sig, midbass are in doors. I'm considering angling them upward, they currently fire right at the console about a foot off the ground. Worth a shot right?!

Open to suggestions. 

Fwiw, i have tried every conceivable (some nowhere near ideal) TA setup.. things change, but not in a way that really helps. I don't think that's the answer. I've tried it, a lot. Believe me .

Thanks


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## gijoe (Mar 25, 2008)

Did you take several measurements of each side and average them? Angling won't make a difference, below beaming the speakers are omni directional.


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## bnae38 (Oct 3, 2015)

gijoe said:


> Did you take several measurements of each side and average them? Angling won't make a difference, below beaming the speakers are omni directional.


Yes, they are averages using hanatsu method.

10-4 on angling, kind of assumed that was the case.

Might just say Eff it.. they are sort of garbage frequencies afterall, but it seems like something is missing.


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## Lanson (Jan 9, 2007)

would be a great spot for a phase changing all-pass filter.


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## bnae38 (Oct 3, 2015)

Thought about GB40's in the dash .

Seems like a lot of money (and work to start over).


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## bnae38 (Oct 3, 2015)

fourthmeal said:


> would be a great spot for a phase changing all-pass filter.



Agreed, i could get a 2x4hd, but.... $$ vs reward. A hell of a lot more to learn too.

Actually, i read the other day we could do that with a regular 2x4... hmmmmm


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## bnae38 (Oct 3, 2015)

fourthmeal said:


> would be a great spot for a phase changing all-pass filter.


Wait a minute, this can be done in the analog domain.. opamps caps and resistors. Have you tried this?


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## Justin Zazzi (May 28, 2012)

To help you diagnose this, it would be really useful to see following measurements:
_(if you can overlay the following three traces on the same graph, even better)_
left midbass only
right midbass only
your midbass house curve, I'm assuming generated by my spreadsheet tool?
_(if you can overlay the following two traces on the same graph, even better)_
left and right midbass together, phase normal
left and right midbass together, phase reversed

If you want to make more measurements, the following might be useful:
left and right midbass and subwoofer only, phase normal
overlay the above with your overall house curve so we can see where the cancellation occurs

For all measurements please use the same smoothing (variable smoothing is good).

Time alignment can be set with a tape measure to within an inch or so of perfection.
As mentioned above, angling them is not useful since they are not beaming in the frequencies you're using them for.


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## gregerst22 (Dec 18, 2012)

if the center console is causing the null why wouldn't angling the speakers away from it help?


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## SkizeR (Apr 19, 2011)

gregerst22 said:


> if the center console is causing the null why wouldn't angling the speakers away from it help?


As said previously, sound is omnidirectional from a speaker up until it's beaming point. Meaning, it travels equally in all directions until a certain point in frequency depending on the diameter of the radiator

Sent from my SM-G920V using Tapatalk


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## gregerst22 (Dec 18, 2012)

I get that but if the drivers are angled upwards more of the sound waves will be traveling over the console instead of hitting it. Though it may not fix the issue couldn't it improve?


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## Justin Zazzi (May 28, 2012)

Low frequency sound radiating from a "large" enough speaker is omnidirectional, meaning it leaves the speaker in every direction equally. It's not exactly the same, but the concept is similar to trying to "aim" a bare lighbulb. No matter which way you turn it, it still lights up the whole room.

The concept of aiming a speaker only works when the wavelength of the sound is small relative to the size of the speaker. This is why you can hear a speaker great if you're standing in front of it. But if you stand off to the side then the treble goes away but you can still hear the bass perfectly.


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## Vx220 (Nov 30, 2015)

What about treatments for the centre console, I know the "1/4 wavelength" rule of thumb means it would need to be thick, but would it be worth trying something thinner to help?


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## Justin Zazzi (May 28, 2012)

It's hard to tell exactly where your cancellation problems are. I'm guessing it's in the 160-200hz range from that first graph. A quarter wavelength of 180hz is about one and a half feet. So to make a significant difference in reflections off that center console you would have to sit on one of your legs to make room for the layer of foam you would have to install. Thinner materials will still have some effect, but not much.

If you were to use something more practical like just 2" of foam, that would be a quarter-wavelength of about 1.7khz (which is well above what your midbass crossover looks like) and would make no difference in the lower midbass range where you have problems.

Your problem is something lots of people struggle with and you should be able to make some progress with that BitOne that you have. Are you interested in posting the measurements I mentioned earlier? That would really give us a better idea of what is happening, and we can better advise you.


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## bnae38 (Oct 3, 2015)

I'll take some more measurements tonight, i have a ps8.

thx


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## SkizeR (Apr 19, 2011)

Vx220 said:


> What about treatments for the centre console, I know the "1/4 wavelength" rule of thumb means it would need to be thick, but would it be worth trying something thinner to help?


Only treatment here is to grab an angle grinder and have at er. There's really not much you can do about it unfortunately 

Sent from my SM-G920V using Tapatalk


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## bnae38 (Oct 3, 2015)

Another thought i had was to try using my crossovers at the same frequency in this region on one driver to fudge the phase. I would then need to use my deck and/or amps to set crossovers for the midbass... 

Something I'll play around with tonight when taking measurements.. There is no "all pass" filters on the ps8 obviously..


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## SkizeR (Apr 19, 2011)

the real question is.. is it audible. can you pick it out on music? can you pick it out with filtered pink noise?


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## bnae38 (Oct 3, 2015)

It is quite audible. When playing a tone in that area it is quiet until i flip the phase of one driver or the other.


As far as on music.... i dunno, it seems like something is missing. Overall FR is good at this point, but I'm betting phase response is relatively fuct in multiple areas .

Would be nice to implement a fix, even if temporary, and see if I like the difference it makes.


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## Patrick Bateman (Sep 11, 2006)

Angling the driver won't do anything.

Neither will modifying the dash.

180hz is 1.9 meters long. That means that if you have two drivers playing 180hz, and one driver is 0.95 metres away, they're going to be out of phase. That creates a null.

Does that make sense? The easiest way to solve this is to get the paths equidistant.

BTW I think this is the reason that midbass arrays sound AMAZING and everyone should use them.

Fourthmeal mentioned FIR filters, that would work too. I'm too cheap, I'd rather buy an extra pair of midbasses 

Everyone I know who's tried rephase has nothing but good things to say.

Also, If you like bass and you try one of the proposed solutions, i think you'll find the difference to be remarkable. It's night and day.


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## gijoe (Mar 25, 2008)

gregerst22 said:


> I get that but if the drivers are angled upwards more of the sound waves will be traveling over the console instead of hitting it. Though it may not fix the issue couldn't it improve?


I'm not sure if you've gotten a satisfactory response yet or not.

Understand what omnidirectional means; the sound coming from the speaker is the same regardless of where the speaker is pointing. The sound waves from the front, back, 15 degrees off axis, 90 degrees off axis, etc. are all the same. There is no difference in sound. Additionally, understand that each point of the wave acts as a source, so it continues to be omnidirectional at each point in the wave. 

Because of this, the direction a speaker is pointing doesn't make a difference as long as we're talking about frequencies below the beaming point. At (and above) beaming angles matter, but not below. So, to put it into perspective with our center console example, the console will interfere the same regardless of how the speaker is aimed. At the listening position, the effect of the center console will be the same because of the omnidirectional behavior of the speaker.


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## durwood (Mar 7, 2007)

Classic case of room modes. Angling will not fix. Just like in home audio (or home theater) where distributed subwoofers is the best solution to even out nulls in the bass, (or move your sub so that the null does not occur at teh seating position) our room is smaller which pushes this issue into the 60-300Hz region.

Try it for yourself and see. This was known a long time ago back in the "I am not sharing my secrets" days, so not many people think about it.
http://www.bobgolds.com/Mode/RoomModes.htm

Choices:
1) Move your seating position
2) Move your midbass to an alternate location
3) use distributed/multiple midbasses in different locations (look at the multiple sub option ideas for home theater but also remember that ITD cues fall in the 60-300Hz region).

All comes with tradeoffs and compromises.

Those null points are due to the dimensions of your vehicle, I think actually it is the length of car (firewall to trunk) that causes it in combination with sitting close to the boundary. It is measured in almost every car. When you are the passenger the nulls are on reverse sides.

It's most likely not that equal path lengths fix it, it's just that you or your speakers are in a different location so the nulls might move to a different location, perhaps lucky enough not where you sit.


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## oabeieo (Feb 22, 2015)

I would add a Woofer in the passenger foot well . Run it in a sealed box crossed over 125 or so firing straightforward basically run it as a sub woofer crossed high should help 


There ain't jack you're going to be able to do with the current set up. As previously posted


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## benny z (Mar 17, 2008)

if you feel something is missing, i'd be looking more at the top end personally...based on your first graph.


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## SkizeR (Apr 19, 2011)

benny z said:


> if you feel something is missing, i'd be looking more at the top end personally...based on your first graph.


if hes using spectrum mode (and not rta), its fine. that would look relatively flat on rta. if on rta mode, i agree


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## benny z (Mar 17, 2008)

SkizeR said:


> if hes using spectrum mode (and not rta), its fine. that would look relatively flat on rta. if on rta mode, i agree


all that newfangled fancy shiz...


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## Lanson (Jan 9, 2007)

bnae38 said:


> Wait a minute, this can be done in the analog domain.. opamps caps and resistors. Have you tried this?


No, I haven't. But I've recently learned (thanks to an AWESOME video about this stuff presented on a thread on this forum) how phase changes really work within a filter, and that brought the idea about.


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## Lanson (Jan 9, 2007)

Can a PS8 take a biquad filter manually?


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## bnae38 (Oct 3, 2015)

SkizeR said:


> if hes using spectrum mode (and not rta), its fine. that would look relatively flat on rta. if on rta mode, i agree


Avg's using sweeps. I'm happy with it tonally, i actually cut the tweets a couple db more from where my house curve was initially.


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## bnae38 (Oct 3, 2015)

fourthmeal said:


> Can a PS8 take a biquad filter manually?



I wish...nope.

Like i said, I'm gonna play with combining XO's just for giggles when i get home. Not very high hopes, but will be interesting to play...


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## Lanson (Jan 9, 2007)

bnae38 said:


> I wish...nope.
> 
> Like i said, I'm gonna play with combining XO's just for giggles when i get home. Not very high hopes, but will be interesting to play...


What about experimenting with different slopes?

You figure that a filter (crossover in this case) is affecting the phase, is it possible to change the crossover slope on left vs. right?


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## bnae38 (Oct 3, 2015)

I can try, in the end it's going to have to make sense to use it though. Ie fix more than it breaks..

Worth playing with though..


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## Lanson (Jan 9, 2007)

bnae38 said:


> I can try, in the end it's going to have to make sense to use it though. Ie fix more than it breaks..
> 
> Worth playing with though..


LOL, game of compromises, every time. 

The video I was mentioning, helped illustrate for me how steep slopes come at a price. I think I learned more in that video than in years of doing this stuff just off-the-cuff, and certainly more than years in school.

Ah, here it is (favorited in my Youtube)
https://www.youtube.com/watch?v=FnpkBE4kJ6Q


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## bnae38 (Oct 3, 2015)

I watched it the other night, thanks.

Was very interesting, had no idea they used phase to actually do the eq..


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## Justin Zazzi (May 28, 2012)

Using different slopes, time alignment, midbass arrays, allpass filters, and all of the suggestions you have so far are good tools for certain problems. The trouble is, we can't say what your problem is unless you offer more measurements. The ones I suggested can help rule out some certain problems. Then we can make better suggestions for you.

I'm not saying everyone is wrong or that I'm right. I'm just hoping you will help us diagnose your problem better before you start changing things.


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## sqnut (Dec 24, 2009)

benny z said:


> all that newfangled fancy shiz...


So much easier to tune for how it sounds rather than how it measures.


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## Lanson (Jan 9, 2007)

sqnut said:


> So much easier to tune for how it sounds rather than how it measures.


I'll drink to that.

edit: I have a similar, particularly nasty cancellation effect in my cabin. But one lucky thing is the effect is NOT where my ears are. If I move my head to the centerline of the car above the center arm rest, and move my head back to about where the 2nd row footwell begins, the bass response is incredibly weak. The null runs a huge range of bass frequencies, to the point where it feels like my subs are off and my ID 6x9's are 4" drivers. My drivers up front and the Sundown 10's in the rear seem to be completely out of phase right there, and you can even hear that weird feeling of pressure but no real output, which to me is cancellation at its peak. Luckily, that is not where my head usually is. But I found it a very interesting null in my cabin. I've been scared of moving that null to a listening position and have in fact not touched my EQ or crossovers or anything (MS-8 based setup) because that null could move if I made a change.


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## sqnut (Dec 24, 2009)

fourthmeal said:


> I'll drink to that.


Cheers!!:beerchug:


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## bnae38 (Oct 3, 2015)

Ok, all measurements are avgs of 8 sweeps except the sub plus mb (was 4... got impatient). Normal points for each, hanatsu method.

Lmb (purple) and rmb (red) individually with house curve. Note i used overall 31band eq some to finish up overall response so it wont quite match.









Both midbass in phase and with LMB phase inverted.









Subs plus mb on and in phase.










Ps: Jazzi, thanks for your tool! Works great.


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## bnae38 (Oct 3, 2015)

With them both on, i took 4 measurements on each ear and averaged the 8. 2" square probably..

For the last pic I did two spots on each ear and averaged the four.


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## gregerst22 (Dec 18, 2012)

gijoe said:


> I'm not sure if you've gotten a satisfactory response yet or not.
> 
> Understand what omnidirectional means; the sound coming from the speaker is the same regardless of where the speaker is pointing. The sound waves from the front, back, 15 degrees off axis, 90 degrees off axis, etc. are all the same. There is no difference in sound. Additionally, understand that each point of the wave acts as a source, so it continues to be omnidirectional at each point in the wave.
> 
> Because of this, the direction a speaker is pointing doesn't make a difference as long as we're talking about frequencies below the beaming point. At (and above) beaming angles matter, but not below. So, to put it into perspective with our center console example, the console will interfere the same regardless of how the speaker is aimed. At the listening position, the effect of the center console will be the same because of the omnidirectional behavior of the speaker.


So for arguments sake. It won't matter where the midbasses are placed in the car? For example one driver mounted on the ceiling facing down and one in the kick panel?


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## SkizeR (Apr 19, 2011)

gregerst22 said:


> So for arguments sake. It won't matter where the midbasses are placed in the car? For example one driver mounted on the ceiling facing down and one in the kick panel?


For mono, and in theory. Yeah have at it. But what happens when you have midbass frequencies on only left or only right 

Sent from my SM-G920V using Tapatalk


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## Elgrosso (Jun 15, 2013)

So if aiming doesn't change anything, could a slightly different placement help a bit?
Even if the wavelength is super long, but here it seems around 180hz so not that long, maybe the width of the car.
Just asking, because I noticed very different graphs when I recently changed my woofers (8" that had to move 2/3" into the cabin to fit).

About spreading the midbasses, it definitley worked in my car, 4x6" fixed almost everything. But timing was never perfect. Just prefer the single 8".


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## gregerst22 (Dec 18, 2012)

I guess what I'm getting at is that the placement, angle and orientation of the midbass drivers can effect nulls. There's cancellation due to frequency length, size of the vehicles cabin and reflections within it. But it seems feasible with experimentation of midbass placement that the null can at least be reduced, maybe not eliminated, but at least improved at the listening position.


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## durwood (Mar 7, 2007)

A semi solution to using multiple midbass locations is to utilize the sub and have it play into your trouble freqs, or have shallow slopes so they overlap. Then play with EQ to lower the overlap. The problem you can run into there is if you have not dealt with rattles, the sub can pull the stage back. This is easier to do in a hatchback or SUV where your trunk is part of the cabin. You can see in your last graph how it smooths it out already when it is included in your measurements.

The other solution if you wanted to play with different locations is put a midbass in a box and temporary place it where your head is. Then using an RTA, move the mic around to possible mounting locations to see where you have the least amount of nulls.

http://www.sengpielaudio.com/calculator-roommodes.htm
Keep the bottom paragraphs in mind when thinking about digital room correction.


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## Patrick Bateman (Sep 11, 2006)

Midbass arrays fix all of this.

Be sure to vary the location quite a bit, don't put them right next to each other.

Mine are about a foot apart. At 180hz, that's one sixth of a wavelength.

You want them close enough that they're within one half wavelength, but not so close that they act as one unit.

Basically between one half and one quarter wavelength.

Note that all of this is frequency dependent too. IE, mine are a foot apart, and that's one sixth of a wavelength at 180hz. But it's one third of a wavelength at 360hz. That means that my midbass array can't play much higher than 500hz due to destructive interference.


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## gijoe (Mar 25, 2008)

gregerst22 said:


> So for arguments sake. It won't matter where the midbasses are placed in the car? For example one driver mounted on the ceiling facing down and one in the kick panel?



Angling and positioning aren't the same thing. If you mount a driver in a particular location, that location and it's proximity to reflections will impact the sound. However, as long as the driver isn't beaming, the angle of the driver at that location won't make a difference. The location a driver is installed can be very important.


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## bnae38 (Oct 3, 2015)

Patrick Bateman said:


> Midbass arrays fix all of this.
> 
> Be sure to vary the location quite a bit, don't put them right next to each other.
> 
> ...


I have some cdt midbass and boxes i could use one in. Could put in the passenger footwell....

Could spare a channel from dsp, instead of using 2 for subs; but i'd have to add another amp. Bleh.


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## Patrick Bateman (Sep 11, 2006)

Why do you need an amp channel? Just run them in parallel.


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## bnae38 (Oct 3, 2015)

Patrick Bateman said:


> Why do you need an amp channel? Just run them in parallel.


I could rewire one of the tm65's to 8ohms then add a 4ohm cdt to it in parallel.

That sounds.... like a mess. 


Edit: Plus i couldn't tune it separately??


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## gregerst22 (Dec 18, 2012)

gijoe said:


> Angling and positioning aren't the same thing. If you mount a driver in a particular location, that location and it's proximity to reflections will impact the sound. However, as long as the driver isn't beaming, the angle of the driver at that location won't make a difference. The location a driver is installed can be very important.


If door mounted midbass are facing parallel with the floor and I angle them up 45 degrees and toward the rear of the car haven't I reduced much of reflections off the floor, opposing speaker, console and provided greater unobstructed path length. All without physically moving them from their positions.


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## bnae38 (Oct 3, 2015)

I do have the rear doors with 6.5's in them... hmmmmmm

I took one of the prefab 6.5 boxes i have and tried to stuff it in the passenger foot well, would have to cut it down substantially.


Edit: Is it remotely feasable to put the cdt mids in the rear doors, and run them mono from 90-about 200hz?


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## Patrick Bateman (Sep 11, 2006)

Just try it with two midbasses per side, and tell us how it sounds

No need to get fancy, just wire them in series or in parallel

If you don't want to take the time to mount them in the door, put them in a $5 flower pot from home depot, just to see how it sounds

Use mortite to seal the enclosure. ($6, it's sold in the aisle with weather stripping)

If you like how it sounds, you can mount it properly. This just gives you a chance to evaluate it


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## bnae38 (Oct 3, 2015)

I have a spare 2channel amp i can use. No sense trying something I'd never do in practice.. would need to change the tm65s to 8ohm and add the 4ohm cdt's in parallel, or leave them and add the cdt's in series. Either way, bleh.

I can run the same signal to them from the ps8, or i can run them monomix with their own signal.

More curious about this, what are your thoughts on running them in the rear doors?


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## seafish (Aug 1, 2012)

gregerst22 said:


> If door mounted midbass are facing parallel with the floor and I angle them up 45 degrees and toward the rear of the car haven't I reduced much of reflections off the floor, opposing speaker, console and provided greater unobstructed path length. All without physically moving them from their positions.


NOT at all...the length of a 200hz tone is over 5' long and omnidirectional (think concentric ripples in water from a pebble being thrown into it), so it is going to be bouncing around the car no matter WHERE you aim the speaker. The trick is to mount them in places that still allow you to equalize the response between the speakers as much as possible as well as avoid nulls from the sound waves canceling each other (the OP's apparent problem). Like PB is suggesting, and like HT users have found out, multiple low frequency sources in a single room can help to eliminate null areas.


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## gregerst22 (Dec 18, 2012)

seafish said:


> The trick is to mount them in places that still allow you to equalize the response between the speakers as much as possible as well as avoid nulls from the sound waves canceling each other (the OP's apparent problem).


Isn't that what I just suggested. By aiming the speakers up and toward the rear of the vehicle, like at the 3rd brake light much of the sound waves that were going straight at the center console or opposing speakers are now being directed to the the rear of the vehicle which is going to be at least 5ft if not further. Of course your going to still have sound waves radiating in all directions but much less reflection from close objects than before. Has anybody ever experimented with this and measured the response.

On the other hand I think Niebur in his build log mounted a small down firing sub up under the dash that filled in the the null he was getting with his midbass. Which may be an easier approach than building arrays and trying to mount midbass in awkward places.


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## durwood (Mar 7, 2007)

Aiming is not going to do anything, waves act as particles and waves (particle-wave duality) and these waves will pass right through none dense objects, so aiming is wasted exercise for midbass.

Coustic XM7 manual had a nice blurb about room modes.









If you use their dimensions into the room mode calculator the key take aways are:

Schroeder Fc: 287hz
Frequency Regions:
- No modal boost: 1hz to 80hz
- Room Modes dominate: 80hz to 287hz
- Diffraction and Diffusion dominate: 287hz to 1148hz
- Specular reflections and ray acoustics prevail: 1148hz to 20000hz

The length of your car must be longer, your nulls start lower. If you change the length you will see those shift around.

Another favorite site of mine you can demo speaker placement in a ripple tank simulation.

Ripple Tank Simulation

For me personally, I tried something that did not require the extra drivers. Borrowing a concept from the "optimal source distribution" model, I pushed my midbass further back in the doors. I am curious as to VW with their Golf models if they decided on this method on purpose or purely just a weird coincident.


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## durwood (Mar 7, 2007)

Ripple tanks simulations:

Single source in free space








Typical door location in the room








Kick panel location








3 sources (doors + trunk)








4 sources (4 doors roughly)








Optimal Source distribution location 90 deg (note not true 90 azimuth unless at ear level)








Obviously if you actually run the sims it is easier to see than a snapshot.


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## bnae38 (Oct 3, 2015)

So... adding midbass in rear doors? Good/bad? Would be run mono.


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## gijoe (Mar 25, 2008)

gregerst22 said:


> If door mounted midbass are facing parallel with the floor and I angle them up 45 degrees and toward the rear of the car haven't I reduced much of reflections off the floor, opposing speaker, console and provided greater unobstructed path length. All without physically moving them from their positions.


Nope, you haven't done anything. As I said, the sound below beaming is omni directional, perhaps I'm not doing a good job describing what this means, I'll see if I can find an illustration. 

Regardless of the angle, sound waves are the same in every direction, the same amount of waves are hitting the floor regardless of the angle, because the waves are omnidirectional. Imagine the speaker is a sphere, and the waves from that spherical source are going equally in every direction. Now if you tilt that sphere, you haven't changed anything, correct? The speaker isn't literally shaped like a sphere, but the sound waves are behaving as if it is.


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## gijoe (Mar 25, 2008)

I see that durwood added some visuals, hopefully that helps.

Think of your example of aiming the speaker at the 3rd brake light. The speaker is facing (on axis with) the brake light, but sound is still omnidirectional, so waves are still hitting every surface near it equally. Take that speaker and aim it at the floor and you still have the same waves going directly at the 3rd brake light (omnidirectional). Aiming does not matter, but location does. 

Think of durwood's particle-wave duality. Think about a sound wave coming from a speaker, now pick any point in space along that wave. Any point on that wave from the source to your ear, acts as a source of a wave, so at any given point, the wave is again omnidirectional.


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## I800C0LLECT (Jan 26, 2009)

Based on Patrick's thoughts I may add another pair of mids to my 3 way. One set under the seat and another in the doors. I've always preferred multiple mids and this is my first time using a single pair. I definitely feel like I'm missing something.

Op...as everybody stated. The speaker is NOT similar to a flashlight below beaming. You can't aim the sound unless the wave length of the frequency is shorter than length of the speaker cone. If it's larger than the width of the cone then it'll radiate evenly in all directions.

Placement can increase or decrease spl. It will also effect how the sound interacts with the environment.


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## bnae38 (Oct 3, 2015)

I'm really not asking about aiming any more.. sigh. Thread kind of got jacked.


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## I800C0LLECT (Jan 26, 2009)

If it helps...there's others who believe that beaming should be used to reduce interaction with the environment.

In a 2-way...aiming your 6.5" mid (or larger?) would allow you to crossover higher, 3KHz perhaps? And open up the possibilities for tweeters since they don't have to play as low. Using shallow slopes could work well in that scenario with a tweeter in the pillar.

That help any?

Sent from my XT1254 using Tapatalk


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## bnae38 (Oct 3, 2015)

I'm considering adding another set of 6.5 midbass to the rear doors or the largest center ch speaker i can fit below the radio in the cubby (likely 4" at most).

Ns3 looks somewhat promising on paper. I could brick wall hp it around 150 up to wherever i want.

Worried about another set of midbass in the rear doors pulling stage back, but i don't think it would be overwhelmingly bad..


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## I800C0LLECT (Jan 26, 2009)

Ah...you should search "cone of confusion". I think you'll be fine adding them as mid bass drivers. If you want them as midrange as well that's another story. Probably a bad idea at that point.


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## Elgrosso (Jun 15, 2013)

Adding a big cc seems a good idea! 
Especially since both woofers will then play much less information in the same time, so less cancellation. 
And your dip being around 180Hz, not sure the rear mid could help enough there.

I was seduced too by the cone of confusion idea, tried it, kind of worked about the dips, but it never sounded really right (same for dual midbass in front, tried many configs).

Edit: only dual front that was quite good, was with some sort of seatbox, second pair firing up at the dashboard, but with a super small bandpass.
This really filled every dips and didn't impact the sound cohesion, but was just too ghetto for everyday.


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## bnae38 (Oct 3, 2015)

Big is relative, but 100mm outer diameter should be (barely) doable. If i find a driver that's a little bigger that i absolutely have to try i can probably make it work..

Any suggestions? Ns3 looked good on paper, but I've tried the ns2. There were things I loved and things i really didnt care for with it...

Alternatively I could fit a couple drivers 3" or less in the area.


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## bnae38 (Oct 3, 2015)

I really liked the looks of this one on paper.... but 125mm is probably too big.

Tang Band W4-1720 4" Underhung Midbass Driver


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## Patrick Bateman (Sep 11, 2006)

I wish you were on the west coast durwood, I'd love to hear your projects.

I wondered the same thing about vw.


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## Patrick Bateman (Sep 11, 2006)

Keep in mind that if you want something really directional, dipoles are always an option.


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## Orion525iT (Mar 6, 2011)

durwood said:


> Ripple tanks simulations:
> 
> Optimal Source distribution location 90 deg (note not true 90 azimuth unless at ear level)
> View attachment 150529
> ...


I didn't do any ripple tank simulations, but i my head, the above sim was what I had expected. Which is why I am going through so much effort to place my midbass at the top of the door, just below ear level, as close to 90 degree azimuth as possible. Started a thread about it a bit back, and I have been slowly working on it for a few months. 

http://www.diymobileaudio.com/forum...-ported-midbass-creating-phantom-sources.html

That position has the added benefit of maximizing ITD in critical frequencies. 

Something else to think about. I drive a coupe, and my subs are in the rear quarter, also placed as close to 90 degree azimuth as possible. I did a set up like that previously (now redesigning to improve upon the concept), and it allowed me to cross the subs at ~150hz, without pulling the stage back. 150hz was exactly where I had a suckout with the door mounted midbass. Essentially, the subs plus the midbass created an array at the crossover point which effectively mitigated the null.


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## gregerst22 (Dec 18, 2012)

durwood said:


> Another favorite site of mine you can demo speaker placement in a ripple tank simulation.
> 
> Ripple Tank Simulation


Cool link.


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## Elgrosso (Jun 15, 2013)

bnae38 said:


> I really liked the looks of this one on paper.... but 125mm is probably too big.
> 
> Tang Band W4-1720 4" Underhung Midbass Driver


(Edited my previous post)
The w6s were awesome as sub, don't know about the 4". Sensitivity/power handling are pretty low...
But if you can fit this guy you can probably find something better no?
Why not a gs40? Or even Gb40 if you find a spare, or split the expense with someone here.
Because you'll still have to cover up to 20khz!

But before the cc there must be something else to help.
Seatboxes/dual door boxes/front third box in passenger/rears with dsp etc
Are you ready to butcher your door panels? 




Patrick Bateman said:


> Keep in mind that if you want something really directional, dipoles are always an option.


Do you have a thread about that that I missed?!


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## beak81champ (Oct 2, 2015)

This thread has a lot of interesting info! bnae38, I have a set of AF GS40's I would be willing to part with. They are BNIB. PM me if you are interested.


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## pocket5s (Jan 6, 2012)

PB was the first that I saw that actually had the most correct info. The wavelength is bigger than the car at those frequencies. Being omni-directional in of itself doesn't mean angling won't work on a speaker. It most certainly does have an effect due to early reflections. However in this case it doesn't because of the frequencies involved.

after scanning through the responses i didn't see one person ask the obvious question, can you HEAR that null? A lot of cars exhibit this behavior, but in many cases even though you can see it on the rta you can't hear it. 

Before adding more speakers or other potentially complicating experiments, try listening to it. The easiest is to take 1/3rd octave pink noise tracks and go through the bands. Start well above that problem area, listen to each band for a few seconds and go down through that area. If you can't hear a big drop in volume, leave it alone.


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## gijoe (Mar 25, 2008)

Early reflections won't change by angling a speaker that is not beaming. Changing locations and changing baffles will effect early reflections, but tilting a speaker a little this way or that way won't do anything. Unless we're talking about speaker types with narrow dispersion, most speakers have broad (omnidirectional) dispersion, so the response on axis and off axis is the same, so reflections are the same.


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## pocket5s (Jan 6, 2012)

science and first hand experience says otherwise, but carry on.


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## gijoe (Mar 25, 2008)

pocket5s said:


> science and first hand experience says otherwise, but carry on.


You can half ass this, or we can talk about it. I'm looking for a discussion here.

If the response of a speaker is the same on axis as it is 90 degrees off axis, how do the reflections change simply by changing the angle? The sound is the same from every part of the speaker, and remains the same after you angle it. Reflections would change if, in addition to changing the angle, you moved part of the radiating surface closer or further from reflective surfaces. Assuming you aren't moving the speaker closer to, or further from, a reflective surface, then simply changing the angle won't make a difference.

I'm more than willing to change my thinking, if I'm wrong, but that isn't going to happen with "science and first hand experience says otherwise, but carry on."


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## Elgrosso (Jun 15, 2013)

I think we all assumed that if bnae38 posted this it's because he can hear the issue (it's quite large). But sure, more tuning should probably help before everything else.

About the general question on angling, to your point gijoe, since it's impossible to change the angle of the speaker without changing its relations to the planes it's attached on (door or whatever), then different angles must have a real effect on early reflections, baffle diffraction etc... And maybe they're not so minor?

But also, even crossed pretty low, some highs are still coming out from the speaker, so directionnal, maybe they caused late reflections/interactions that can have an hearable effect? (Even if not this kind of dip).
Am I wrong?


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## gijoe (Mar 25, 2008)

Elgrosso said:


> I think we all assumed that if bnae38 posted this it's because he can hear the issue (it's quite large). But sure, more tuning should probably help before everything else.
> 
> About the general question on angling, to your point gijoe, since it's impossible to change the angle of the speaker without changing its relations to the planes it's attached on (door or whatever), then different angles must have a real effect on early reflections, baffle diffraction etc... And maybe they're not so minor?
> 
> ...



Well, let's see. Let's take a door mounted midbass as an example. If the midbass is mounted flat, like most are from the factory, does changing the angle make a difference? The change in angle has brought the top of the woofer a tad closer to the door panel, and pushed the bottom of the woofer away, but is that enough to make a difference? With midbass I would certainly say no. The wavelengths are too long, and the minor change in reflections would be negligible and inaudible. 

Does this change with high frequencies? Let's put a tweeter in the corner of the dash aimed at the dome light, then aim on axis to the driver. Clearly, at and above the beaming point, there will be a difference, but what about below that point? With a tweeter, the wavelengths might be short enough that 1/4" difference on one side might matter. What if we put that tweeter in a spherical pod? Without baffle diffraction can we now twist and turn that tweeter in any direction and have the same response?


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## pocket5s (Jan 6, 2012)

gijoe said:


> You can half ass this, or we can talk about it. I'm looking for a discussion here.
> 
> If the response of a speaker is the same on axis as it is 90 degrees off axis, how do the reflections change simply by changing the angle? The sound is the same from every part of the speaker, and remains the same after you angle it. Reflections would change if, in addition to changing the angle, you moved part of the radiating surface closer or further from reflective surfaces. Assuming you aren't moving the speaker closer to, or further from, a reflective surface, then simply changing the angle won't make a difference.
> 
> I'm more than willing to change my thinking, if I'm wrong, but that isn't going to happen with "science and first hand experience says otherwise, but carry on."


See below...



Elgrosso said:


> I think we all assumed that if bnae38 posted this it's because he can hear the issue (it's quite large). But sure, more tuning should probably help before everything else.


that's an assumption that needs to clarified 



Elgrosso said:


> About the general question on angling, to your point gijoe, since it's impossible to change the angle of the speaker without changing its relations to the planes it's attached on (door or whatever), then different angles must have a real effect on early reflections, baffle diffraction etc... And maybe they're not so minor?
> 
> But also, even crossed pretty low, some highs are still coming out from the speaker, so directionnal, maybe they caused late reflections/interactions that can have an hearable effect? (Even if not this kind of dip).
> Am I wrong?


close. The link below has some detailed measurements on various locations and angles on a midrange driver in the dash. You will see that even below beaming, the angle in relation to the driver's surroundings will change the frequency response. 

Beyond just the frequency response, the angle can have significant effects on staging and imaging. For example, in my car with sail panel mids, my first effort was having the driver parallel to the side glass, firing along the glass essentially. Now, this gave me a very wide stage because of that glass reflection (mid-mirror to edge of mirror). However, it collapsed the left center onto the left. The only way to fix that flaw with tuning resulted in an amplitude imbalance left to right. 

Using the same location but angling the speaker so it points to the opposite side seat fixed the left center imaging problem but narrowed the stage slightly. The effect of this imaging shift was predominant in the 400-700hz range, well within the beaming area of the driver (a 2.5" mid).

in a previous setup on this car, I had the mids in the OEM locations in the dash corner, firing up. The left side had a slight ghosting/split image effect due to the angle relationship between the mid and windshield. Changing the angle on the mid helped solve that problem, but would have required a dash pod that at the time I didn't want to have, or pulling the windshield and building into the dash which I also did not want to do.

In another car of a good friend (and competitor from a couple years ago), the angle of his mids changed the focus of the image in his car. It took him a few tries to get the angle just right to overcome the issues in his car. 

This paper has some good info. In particular look at page 11, section 8. 
http://www.jjracoustics.com/129_AES-2010.pdf


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## bnae38 (Oct 3, 2015)

bnae38 said:


> It is quite audible. When playing a tone in that area it is quiet until i flip the phase of one driver or the other.
> 
> 
> As far as on music.... i dunno, it seems like something is missing. Overall FR is good at this point, but I'm betting phase response is relatively fuct in multiple areas .
> ...


Carry on.


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## Elgrosso (Jun 15, 2013)

I was really focusing on midbass only, I mean pretty sure everybody agrees that angles can have a huge impact on the result with midranges & tweeters, especially in corners on the dash.

In your example gijoe you took a reasonable angle, but what if we use something like 30/45/90 degrees?


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## pocket5s (Jan 6, 2012)

Elgrosso said:


> I was really focusing on midbass only, I mean pretty sure everybody agrees that angles can have a huge impact on the result with midranges & tweeters, especially in corners on the dash.
> 
> In your example gijoe you took a reasonable angle, but what if we use something like 30/45/90 degrees?


I agree with gijoe's previous statement about the wavelength of the midbass being too big to have any effect from angle changes. You are more likely to have issues with other things in the car, like a big center console or something like that.


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## durwood (Mar 7, 2007)

See posts 18 and 19...not making assumptions "hear". 

If it were me who likes to go the easy route first.

1) start with using the sub to overlap. Does it make the null less for you? If it does are you happy with it enough?
2) next stage, try some temporary setup with rears included (bookshelves, speakers in temp enclosures, stereo or mono), does it get better or worse?
3) Stage 3, Play with other locations using the method mentioned by searching for a new location via measurement.

You can choose how far you want to go with experimenting and investing.


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## bnae38 (Oct 3, 2015)

durwood said:


> 1) start with using the sub to overlap. Does it make the null less for you? If it does are you happy with it enough?


So you've found success with this? Wondering if you played the sub overall into the trouble range, or eq'd it only to the area that needed boost?

Either way, kind of skeptical... but I might give it a shot.


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## Lanson (Jan 9, 2007)

Since phase is affected by crossover (well beyond the crossover point), have you tried changing crossover slopes?


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## bnae38 (Oct 3, 2015)

Seems like I have, i need to check that again.. 

thanks


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## bnae38 (Oct 3, 2015)

Nah, still dead if the lmb and rmb slopes match.

If i change one to another slope I get better volume in the null range, but I'm betting i'm fubar elsewhere.


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## Mic10is (Aug 20, 2007)

Is it audible on actual music? Unless u regularly listen to tones and demo your system with tones then nulls are typically very hard to hear. 
Nulls between 250 and 500hz are quite common in most systems


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## iyamwutiam (Nov 20, 2006)

Mic10is said:


> Is it audible on actual music? Unless u regularly listen to tones and demo your system with tones then nulls are typically very hard to hear.
> Nulls between 250 and 500hz are quite common in most systems


This is why we need a like button


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## Jscoyne2 (Oct 29, 2014)

So how close is exceptable for matching crossovers? Sometimes your chosen point misbehaves and makes matching points rather difficult. In lower frequencies. Less than 1k, matching xos is pretty much pick a spot without a null and go but in the higher regions 4k+. I can get decent slopes around 2-400hz of eachother. Im sure this isnt ideal but what exactly is too far away?

Sent from my SGH-T999 using Tapatalk


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## Jscoyne2 (Oct 29, 2014)

Specifically this

Sent from my SGH-T999 using Tapatalk


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## bnae38 (Oct 3, 2015)

Mic10is said:


> Is it audible on actual music? Unless u regularly listen to tones and demo your system with tones then nulls are typically very hard to hear.
> Nulls between 250 and 500hz are quite common in most systems





bnae38 said:


> Might just say Eff it.. they are sort of garbage frequencies afterall, but it seems like something is missing.



I'm not entirely sure, would like to know what it sounds like with the null filled


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## OldNewb (Sep 30, 2016)

Sit in the car listening to headphones then listen to the car. You will get a rough idea if it's worth bothering with. Or a nice HT if you have access. I use to go sit at a place down the road in their demo room for hours just to listen to songs that I wasn't getting right in the car


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## bnae38 (Oct 3, 2015)

Kind of running with the center channel midbass idea, gs40's will ship to me on Monday. Going to try one in the cubby below the deck, see pic (not mine).










Did some experimenting. Changed one of my sub outputs on the ps8 to a center channel (sum L/R) and hooked it up to my lrx2.150 2ch (bridged). Tried a couple different types of speakers to see if i liked what i heard. I did. To my ear the gap fills nicely with tones (155-210 range), and didn't kill off above or below it that I could hear. I didn't do any measurements, but it was enough to reassure me purchasing the frogs wasn't a waste.. Listening to music, and turning the center channel off and on with the ps8 tells me its definitely a step in the right direction.

What I didn't care for: going above the midbass hp xo (350) on the center, it drug the stage down and right. I couldn't really get timing right with TA to center up the high's, but it was the location bringing the stage down that will probably have me running the speaker just on the lower end.... Oddly, running just lower frequencies the center channel midbass seems to drag the stage slightly left. Likely driver interaction/tuning opportunities.

I tried a logitech computer speaker in pod (slightly smaller than gs40), pic below. I also tried a cdt 6.5mid in the large boxes i have.
http://ecx.images-amazon.com/images/I/41RXTCQJBDL.jpg

I'll miss my cubby spot, and not overly thrilled with adding another amp, but looking up!


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## bnae38 (Oct 3, 2015)

Btw, gross volume is roughly .08cuFt. Ideally i would run it 90-350 like Tm65's, but will probably have to do closer to 130-350.


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