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View Full Version : Should I run 4 or 8 ohm mids?



_Vince
08-08-2012, 11:36 PM
What's up CA members? I'm working on fiberglassing my doors and I want to run Sundowns: (1) 8", (2) 6.5", & (1) tweeter per door on a Sundown 100.4

I'm stuck between running these parallel:
all 8 ohm speakers at 2.66ohms
all 4 ohm speakers at 1.33ohms
8ohm 8" & 4ohm 6.5" 1.60ohms

I'm running active, so tweeter wouldn't matter. So if someone can tell me the benefits and downfalls of running the above options, that'll be great.

duanebro
08-08-2012, 11:52 PM
Less power from the amp at 8 ohms, other than that, not much.

I am lost at why you want to use the size and number of speakers you listed.

_Vince
08-08-2012, 11:57 PM
Less power from the amp at 8 ohms, other than that, not much.

I am lost at why you want to use the size and number of speakers you listed.

Yeah, but how loud will it be with all speakers at 8ohms?
I'm making speaker pods for my doors and the maximum room I have without tremendously cutting the doors is 9". I also wanted to add some more midrange/bass to even out my 6 SA12s

Rich B
08-09-2012, 12:02 AM
Is the 8" going to be wired to the same amp as the 2x 6.5", and what kind of amp is it?

_Vince
08-09-2012, 12:04 AM
Is the 8" going to be wired to the same amp as the 2x 6.5", and what kind of amp is it?

Yes, I was going to run all the speakers parallel to a Sundown 100.4

TreyE
08-09-2012, 12:05 AM
5ohms

duanebro
08-09-2012, 12:07 AM
Yeah, but how loud will it be with all speakers at 8ohms?
I'm making speaker pods for my doors and the maximum room I have without tremendously cutting the doors is 9". I also wanted to add some more midrange/bass to even out my 6 SA12s

You will have half as much power at 8 ohms, so 3 db less. Could you fit two 8"s and one 6.5? Or depending on the speakers and what frequencies you want to use them at going with a smaller mid... 6.5" speakers can start to "beam" around 1500-2000 Hz iirc. There is more to look at than ohms....

Below20hzonly
08-09-2012, 12:09 AM
wouldnt you want to run the 8" at 4 ohms and the other speakers at 8?

fasfocus00
08-09-2012, 12:09 AM
i'd do the 8" in a kick panel, the 2 6.5" in the door and the tweeter in the door or the pillar. 8Ω and 4Ω have no real difference, it'll depend on what you want your final Ω load to be at. example I have 2 6.5" mids in each door, they are 4Ω each so I can get a 2Ω load on each channel. just personally preference I'd get another 2 channel amp and run just the 8" off of that and use that 4 channel to run your 6.5" and tweeter.

VWBobby
08-09-2012, 12:10 AM
If you wanted to, you could run a "semi" active setup.... run the 8" speakers from 120hz on down bridged on the rear channels. Run the other speakers on the front channels in stereo from 120hz on up, HPF.

Rich B
08-09-2012, 12:11 AM
8" at 8ohms, the two 6.5" at 4ohms.

Series the two 4ohm 6.5" to an 8ohm load, then parallel the 8ohm 8" with the two 6.5" already in series at 8ohm and you'll end up with a 4ohm load at the amp.

duanebro
08-09-2012, 12:11 AM
Yes, I was going to run all the speakers parallel to a Sundown 100.4

Just so I understand - each size of speaker will have its own channel? And the tweeters will be on another amp?

_Vince
08-09-2012, 12:20 AM
Time to catch up with the posts


You will have half as much power at 8 ohms, so 3 db less. Could you fit two 8"s and one 6.5? Or depending on the speakers and what frequencies you want to use them at going with a smaller mid... 6.5" speakers can start to "beam" around 1500-2000 Hz iirc. There is more to look at than ohms....

I can fit 2 8" and 1 6.5", will just have them flat against the panel instead of centering.


i'd do the 8" in a kick panel, the 2 6.5" in the door and the tweeter in the door or the pillar. 8Ω and 4Ω have no real difference, it'll depend on what you want your final Ω load to be at. example I have 2 6.5" mids in each door, they are 4Ω each so I can get a 2Ω load on each channel. just personally preference I'd get another 2 channel amp and run just the 8" off of that and use that 4 channel to run your 6.5" and tweeter.

Yeah, I know it's about the final impedance but the individual impedance and how I wire it will determine the final impedance (right?). and I wanted to get a separate amp for the 8"s but that'll have to come later on.


8" at 8ohms, the two 6.5" at 4ohms.
Series the two 4ohm 6.5" to an 8ohm load, then parallel the 8ohm 8" with the two 6.5" already in series at 8ohm and you'll end up with a 4ohm load at the amp.

This is actually what I wanted to do, wasn't sure if it was going to work or not.


Just so I understand - each size of speaker will have its own channel? And the tweeters will be on another amp?

no, tweeters will have it's own channel. and if it's okay to run the speakers like the reply above this one, than I want to run it like that.

_Vince
08-09-2012, 12:20 AM
Nothing here, double posted

keep_hope_alive
08-09-2012, 01:31 AM
it's not active if the 6.5's and 8's are on the same channel. and it is not advisable to give all 3 the same signal. having three speakers playing the same signal - yet each a different distance from your head will sound weird and poor. the effect is called comb filtering - a form of phase interference. you want to bandpass the 8" to handle midbass only. then let the 6.5's handle midrange - of which you only want 1 mid per side.

if your question is if you should run two channels of the sundown at 1.33 ohms or 2.66 ohms, i vote the latter to make the load easier on the amp. later, when you have enough amp channels to do what you ultimately want, having all 4 ohm drivers is fine. but the real issue is that what you are planning to do is flawed. you're welcome to try and find out for yourself. maybe you'll like it. hell, people like Bose.

running tweets active isn't gaining much. you don't need to T/A tweeters. you just want level control and crossover flexibility. you run tweets active when you have spare amps channels to play with.

i would re-work your plan. run the tweeters off a passive crossover on the same channels as one 4 ohm 6.5" dedicated for midrange. then run a 8" midbass off the other channels, bandpass. this is a tried method that works well. when you have 6 amp channels, then run the various speakers individually.

lastly, you don't want mids and midbass sharing the same airspace. the midbass will pressurize the mid (out of phase) and distort it.

more speakers mounted on a door panel looks neat, but sounds quite poor. you want one driver producing midrange per side. you can double up on midbass drivers since the wavelengths are long enough that phase interference isn't as much of an issue when they are side-by-side.

my buck-o-five

mlstrass
08-09-2012, 04:21 AM
amp won't like 1.33 at all and will probably protect at 2.66 if you play it loud for long periods of time. I have a sundown 100.2 that i've run at 2ohm per channel at times and it gets hot and shuts off on hot days.

As for your choice of mids/set up that is up to you. I run 4 6.5's and 2 12's per door. It sounds just fine and gets VERY loud.

I assume playing very loud and sounding good is your objective, not ultimate SQ. I've installed a lot of PA set ups and have never had anyone complain about comb filtering, stage issues, ect...

So Hope how is he NOT active if he's not running passive xovers? Makes no diff if he's using diff sized mids, you lost me there...

keep_hope_alive
08-09-2012, 04:50 AM
"active" when powering 6.5's and 8's on the same channel? nah. defeats the purpose. just eliminating passive crossovers is only part of it.

"active" is using electronic crossovers to properly filter each speaker, especially speakers of different sizes.

it's not about "ultimate SQ". it's about spending money and time wisely.

people don't complain about "comb filtering" but i can measure it in any of your installs. our performance spec would require you to EQ the system, which is near impossible with comb filtering - since each seat will have different nulls and peaks. what sounds good is subjective. in general, people are used to phase interference and distortion. they are used to reproduction systems that are poorly implemented. the majority of performance spaces are poorly done. the majority of concert halls have acoustics issues. in general, few people have any clue what they are doing. and most PA installs have left and right arrays when the source is mono. DOH! Hell, just plug your installs into EASE and you'll see it there, you don't even need a mic.

i battle constantly with people saying "that's how i've always done it". just think if we took that same approach to medicine... where would we be?

/acoustics rant :)


regardless; if this was a thread asking about running 10's and 12's off the same amp channels, the responses would be different. but when it comes to playing frequencies where it actually matters...

_Vince
08-09-2012, 09:13 AM
I was thinking about it over night and you guys made some pretty **** good points. I'll be scrapping my original plan and either going with 2 8" per door or 3-4 6.5" per door.

I left this information out but I already have 4 6.5" 4ohms and 1 8" 8ohms. I'll just have to decide which setup I want


lastly, you don't want mids and midbass sharing the same airspace. the midbass will pressurize the mid (out of phase) and distort it.


How big of a problem is this? Now that I've read everyone's post, I'm thinking of 2 8" or 4 6.5" per door + a tweeter. BUT can I run 2 8" & 1 6.5" + tweet per door? how will the quality be like that with your knowledge?

_Vince
08-09-2012, 10:00 AM
I was thinking about it over night and you guys made some pretty **** good points. I'll be scrapping my original plan and either going with 2 8" per door or 3-4 6.5" per door.

I left this information out but I already have 4 6.5" 4ohms and 1 8" 8ohms. I'll just have to decide which setup I want


lastly, you don't want mids and midbass sharing the same airspace. the midbass will pressurize the mid (out of phase) and distort it.


How big of a problem is this? Now that I've read everyone's post, I'm thinking of 2 8" or 4 6.5" per door + a tweeter. BUT can I run 2 8" & 1 6.5" + tweet per door? how will the quality be like that with your knowledge?

duanebro
08-09-2012, 11:06 AM
Ok, you should use a separate channel for each different speaker, and your amp can be set to a band pass type xo I think. This would allow you to correctly xo the mid and mid bass. Get another amp to run the tweeter...

I don't know what speakers you are planning on using, or their FR and specs. But in general, it is much harder to play lower notes. This is why a 1" tweeter can keep up with a much larger sub. This is why I would also use a single mid with 2 midbass speakers.

VWBobby
08-09-2012, 05:07 PM
Listen to what Keep_Hope_Alive said. He is dead right and I am much too tired and exhausted to repeat everything he said. Everything that he said is exactly how I would do it. Personally, I am running 8" speakers from 80hz down. 6.5" coax speakers from 120hz up, 6db/oct HPF's. It sounds good, but not as nice as a full 3-way active setup with T/A.

mlstrass
08-11-2012, 05:05 AM
"active" when powering 6.5's and 8's on the same channel? nah. defeats the purpose. just eliminating passive crossovers is only part of it.

"active" is using electronic crossovers to properly filter each speaker, especially speakers of different sizes.

it's not about "ultimate SQ". it's about spending money and time wisely.

people don't complain about "comb filtering" but i can measure it in any of your installs. our performance spec would require you to EQ the system, which is near impossible with comb filtering - since each seat will have different nulls and peaks. what sounds good is subjective. in general, people are used to phase interference and distortion. they are used to reproduction systems that are poorly implemented. the majority of performance spaces are poorly done. the majority of concert halls have acoustics issues. in general, few people have any clue what they are doing. and most PA installs have left and right arrays when the source is mono. DOH! Hell, just plug your installs into EASE and you'll see it there, you don't even need a mic.

i battle constantly with people saying "that's how i've always done it". just think if we took that same approach to medicine... where would we be?

/acoustics rant :)


regardless; if this was a thread asking about running 10's and 12's off the same amp channels, the responses would be different. but when it comes to playing frequencies where it actually matters...

how does it defeat the purpose? It allows him to run any mids he wants and set up a bandpass for them. It may not be ideal to YOU, but that doens't mean he won't be happy with it.

It doesn't matter what you can measure, if the listener can't hear it for whatever reason then it's not a problem.

You're talking about concert hall/stage set ups, why??? Has nothing to do with a car audio environment. Roll down the highway at 55mph with the windows down, SQ isn't a concern, just being able to hear it is the main concern. Having very loud bass is much the same way, you're main goal is to make sure the mids/highs can be heard. Not comb filtering, staging, imaging, ect...

I've done a lot of PA set ups in cars that meter from 150-160 and the owners have all been very happy with how they sound. That's the end goal, plain and simple.

Unfortunately all your doing is throwing your preference at him, not helping him figure out how to make what he has work. If you don't agree with what he's doing, then move along and don't respond.

I run 6.5's, 8's, 10's, 12's, and 15's in my demo set up, all running active off the same HU. Gets VERY loud and sounds very good to the average listener, so I know it can be done...

keep_hope_alive
08-11-2012, 10:56 AM
I was thinking about it over night and you guys made some pretty **** good points. I'll be scrapping my original plan and either going with 2 8" per door or 3-4 6.5" per door.

I left this information out but I already have 4 6.5" 4ohms and 1 8" 8ohms. I'll just have to decide which setup I want



How big of a problem is this? Now that I've read everyone's post, I'm thinking of 2 8" or 4 6.5" per door + a tweeter. BUT can I run 2 8" & 1 6.5" + tweet per door? how will the quality be like that with your knowledge?

a pair of 8" midbass and one 6.5" midrange can sound great. you can run multiple midbass drivers with no issues. i would have the two 8's low, and the 6.5 above them, aimed near the dome light.

keeping airspace separate is still important, but easy to do. those 8's will have the ability to pressurize the door cavity - which would move the 6.5" cone in opposition to the 8's, causing both cancellation and eventually ruining the speaker. with the midbass drivers playing up to 300Hz or so, the 6.5 doesn't need to play as low, so it doesn't need as much airspace. A sealed pod for the midrange would be all you need. Since you're building the doors - your can make that happen pretty easily. The 8's can vent into the door cavity.

See my build log for how I recently added PVC encased fiberglass batt to my doors - that small effort made huge gains in midbass by lower the f3 point of the doors (similar to adding fiberglass/fill to a sub enclosure). I would recommend that to anyone looking to lower midbass extension in their doors.

always remember what we are trying to achieve when installing speakers - we want to isolate the rear wave from the front (or control/delay it with vented enclosures). The rear wave will combine with the front and cause cancellation. The rear wave has two main paths - 1. through leaks in the enclosure, and 2. reflecting off the rear wall of the enclosure and leaving through the speaker cone (speaker cones have almost no transmission loss, especially at lower frequencies).

A good home audio speaker design will use internal baffles and internal fill to separate airspace for mid and midbass, and to reduce the rear wave reflection.

keep_hope_alive
08-11-2012, 11:24 AM
what you said (not quoted to save space)

if someone asks for opinions, they are open to suggestion and wants to know what to learn from the efforts of others. if that is the case, I prefer to give them the best chance for success. a single midrange speaker per side is optimal. best place to start. our ears are most sensitive in that range anyway. we are less sensitive to midbass frequencies, so we want a bump below 200Hz. many agree with me, you are alone in your approach.

I have 10 well defined speaker locations for the front stage of my car that can be configured in a number of ways. i use 6 at a time in a 3-way active configuration. i've added drivers and ran more than one per frequency range to experiment. was it louder? yes. was it unfocused and unnatural? you bet. would I want to listen to that every day? nope. i don't know anyone that would want that when listening to music is their goal. now, when people want loud noise - the more the merrier and they can follow your approach.

experimentation is great, and i'm all for people trying things out to see what they like and don't. when you have the money and time to waste - go for it. i've spent hundreds of hours experimenting, i'm sure you do as well. i'll try things that people ask about, just to have an informed opinion. if you want to just do it once, take a focused approach making music sound good.

over the years, i've mixed driver sizes, overlapped frequency ranges, added more drivers to be louder - etc. when i was 19 i thought it was fine. then i met some competitors, learned more about acoustics, and started paying more attention to tonality. it's not about concert hall acoustics in a car - granted, you can look at those concepts and adapt them to a car. i attempt to explain the phenomenons that people experience in a car though the eyes of an acoustics engineer. i have come to realize WHY i hear certain things in a car. so i do speak in acoustics terms.

i agree that you can make a PA-style setup be very loud in a car by filling it with speakers.

the OP wants to enjoy music at a higher volume. but they want to enjoy music - not hear noise.

FYI - windows down at 55 - i still have a sound stage, i still have good tonality. if anything, soundstage focus is improved by eliminating the dreadful reflecting plane by my ear. :)

lastly, above 130dBA you don't hear music. you hear noise and you damage hearing. i prefer not to give people tinnitus.

mlstrass
08-12-2012, 09:24 AM
Are the 6 12's in a wall? I'd do 2 8's per door and a single super tweeter. If that's not enough "assuming" you have a wall then you could add 6.5's in the side trim panels. If it's an SUV then the rear doors would work.

My daily does a 47 on music and a single 6.5 per door keeps up no problem.

whitedragon551
08-12-2012, 09:47 AM
Efficient 8 ohm > 4 ohm. Half the power from the amp, same level of output, less stress and wear and tear on the amp.

The "Real Deal" with 8 ohm drivers - DIYMA Car Audio Forum (http://www.diymobileaudio.com/forum/how-articles-provided-our-members/31-real-deal-8-ohm-drivers.html)