# Tuning mid in door on the cheap



## sqshoestring (Jun 19, 2007)

I have done this for years, but note it may not work well with high power and large motor drivers or you may have to find a different enclosur for them/etc. Large motors can fill the baffle and high xmax can deform the baffle. But for normal to cheaper mids in say a typical comp set it works fine. This is based on running a mid down to about 80Hz and will use that crossovr point for this example.

First off in case you are not familiar, when you put a small enclosur on a bass driver (even though this is more like midbass) you raise the Q. To simplify that means you boost the bottom its capable in turn for losing lower than its capable. For a typical 6.5 mid lets say it can play 80Hz and you don't care about lower than that where it will be weak, so you want to maximize 80-100Hz before it hands off to the sub.

We will buy a set of the foam baffles sold by many places (like XTC brand at Parts Express). These will raise the Q very high for most mids, such that they don't even want to make 80Hz at all. So we tune it like an AP enclosur (aperiodic). Take the baffle and cut a few small squares or slots in the bottom but only cut three sides. What works the best is if you can mount the driver then reach into another hole in the door to open/close the holes. Play music or tones and carefully listen for that 80-100Hz range, you want the mid to play them louder and not play below that. You close the holes it will play higher, open or cut more and it will play lower until it plays like it has no enclosure. This can take some time depending on how well you can hear the tones. You can reach in and tape the holes back shut if needed to get the tuning right. Once you get them right button the door back together you are done. 

Note that cutting back the low end response by closing up the baffle will increase power handling, so far as xmax getting too high, but of course you raise the response peak higher in frequency the more you do. The idea is have it come on at 80Hz and play strong from there on up, or whatever frequency you are trying for. Some cheap mids I have tuned to play 100 and up because they could handle more power that way. I've also tuned 3.5" drivers in the dash with them, 5.25, 6.5, and even 6x9 but the baffle volume tends to be too small for those to work as well.


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## s4turn (Jun 17, 2009)

wow nice write up!

I just installed some XTC baffles, however cut most of the back of it. I would of liked to have tried this.

wouldn't you need to strengthen the foam baffle? if using it for an AP enclosure? i.e the sides


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## bkjay (Jul 7, 2009)

Thanks must try on my next install.


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## rufast (Aug 7, 2010)

gonna have to try this on my front mids.


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## sqshoestring (Jun 19, 2007)

s4turn said:


> wow nice write up!
> 
> I just installed some XTC baffles, however cut most of the back of it. I would of liked to have tried this.
> 
> wouldn't you need to strengthen the foam baffle? if using it for an AP enclosure? i.e the sides


If you use enough power/xmax it will deform the baffle, but normal levels it does not seem to do much. Many cars you can look in there and see it, sure if it starts to move around thats not going to work. The ones I liked best were the crutchfield, not sure they are the same now but they used to be white and foam with a plastic shell on them that made them stiffer. No I looked they have the gray ones too.

You could use a plastic bowl or something too of course, its just if the foam baffles work its way easy to implement unlike a 'real' enclosure.

I wish I had a better way to explain how to tune them, it can be hard to find a rolloff at ~80Hz by ear if you are not used to that stuff. I used to play music full range at a moderate volume with various bass tracks in it, then boost the 80Hz on the EQ way up to find it, then as you change the holes you can hear the lower bass go away...open it back up until it plays the 80 again.


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## AdamTaylor (Sep 7, 2008)

basically

more holes = more perceived airspace = the lower the driver will play

less holes = less perceived airspace = the higher the driver will play

is that what you were trying to say?


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## rj671j (Jul 7, 2007)

Going to give this a try. Thanks


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## sqshoestring (Jun 19, 2007)

AdamTaylor said:


> basically
> 
> more holes = more perceived airspace = the lower the driver will play
> 
> ...


Yes, but you want to make a peak in response at 90Hz or whatever is just above your high pass. Its hard to hear it by ear. I play it full range and vary the holes until the midbass is strongest, you can change the crossover settings to figure out what sounds in your test music/tones are at the Hz you are tuning for. Then I make the hole configuration permanent and its done. LOL, but I use early Madonna to do this usually, the bass tracks move up/down and cover most of the bass spectrum its easy to hear where it falls off.

You might be able to play (ex: 85-90Hz for a 80Hz HP) tone and try to make it loudest, I have not done it that way. Also you could tune the other way; use a 60Hz tone and gradually close the box up until you hear it get quieter, then you know the peak is higher than 60 it should be 80 or whatever then verify. IMO its best to play with that stuff until you can hear what is happening, if you can't.

When you use a smaller enclosure it actually pushes up a peak = more output. The smaller the box, the higher the peak in frequency and output/dB. Of course a huge peak at 150Hz in your mid with nothing under that is not going to help you, you have to find when the peak begins and stop at just over your high pass.


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## Rock&Roll (Apr 21, 2009)

I've been thinking about experimenting with this idea. This is what I'm planing to do, get some foam baffles, reinforce them with fiberglass, cut a hole in them where I would install an aperiodic membrane from Dynaudio. The way I figure is at at different volume and frequencies the speaker would be able to breath at it's likeness, demands or desire. I figure the enclosure will behave as a small enclosure at low volume reenforcing the bottom end notes helping in better volume output and at higher volume it would act as a larger enclosure so the driver could breathe better. 
Your input will be greatly appreciated.
Richard


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## jp_over (Dec 21, 2011)

Subscribed!


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