# Need your thoughts to correct newbeness



## johnnyfamous (Jan 21, 2009)

First i have to say i love this site, it has been very helpfull! The only wish i had is that i found it before i built these. I would have done a few things different. But i guess the fun in DIY is learning along the way. my intent is to change a few things to get the most out of what i have already. 

from what i have read i broke one of the cardinal rules of speaker building, not flush mounting the tweeters. I plan on making this change. Does this apply to the woofer as well? from what i have read, flush mounting the woofer is more looks than anything, is this correct? oddly enough i like the look of surface mounting, but i want the best sound i can get so i will definatley flush out the tweeters.

overall the sound quality at this point is very good. but i am sure could be better, and i want to try and make it better.

thanks for any expertise.


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## dyohn (Apr 17, 2008)

There's really nothing "wrong" with surface mounting tweeters. I do it in many designs. Flush mounting them can help with time alignment and in some cases can reduce diffraction effects. But seriously, the impact is subtle and in many cases inaudible. If you feel like trying it there's nothing wrong with trying it of course, and isn't that part of the fun of DIY?


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## Anthony (Oct 5, 2006)

Flush mount tweeters: yes
Flush mount woofers: depends. Yes if visible, not necessary if hidden (opinion there). The wavelengths are long enough that you don't need to worry about the diffraction effects around the "step" down from speaker to baffle surface.

Now, that all being said, flush mounting after you have drilled out the middle is VERY difficult. Usually with a circle jig, you drill a center pivot hole and then make the following cuts:
1) Flush mount recess (largest diameter)
2) Inside hole (smallest diameter) -- usually in several passes so as not to strain the bit.

Once the inside pivot hole is "gone" it's hard to make the recess. You can try a rabetting bit with a guide bushing, but be very careful.

Those speakers look so nice too, I would hate to mar up the finish while recessing the tweeter. You have to ask if it's worth it. If you like the sound now, I'd leave well enough alone. Use this as an excuse to build another set 

Good luck.


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## johnnyfamous (Jan 21, 2009)

i read this on parts express website, they are modeling my tweeter as well. judging by what they say it might be a worth while attempt??

http://www.parts-express.com/resources/build-a-speaker.cfm

Also, the drivers, particularly the tweeter, should be flush mounted to minimize diffraction effects. It's amazing how much smoother the tweeter's frequency response is by simply flush mounting it!

The two frequency response curves to the right are of the popular Vifa D25AG-35 aluminum dome tweeter (#264-512) and compare flush mounting versus conventional mounting. Without flush mounting, the tweeter's response from 1,500-20,000 Hz is +/- 4.5 dB (referenced to 91 dB). Note the 3.25 dB peak at 4,500 Hz followed by a 4.5 dB dip at 7,000 Hz; not a good result. When flush mounted, the same tweeter is now +/- 2.0 dB from 1,500-20,000 Hz and +/- 1 dB from 6,000 to 20,000 Hz! A superb performance for any tweeter.


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## johnnyfamous (Jan 21, 2009)

Anthony said:


> Now, that all being said, flush mounting after you have drilled out the middle is VERY difficult. Usually with a circle jig, you drill a center pivot hole and then make the following cuts:
> 1) Flush mount recess (largest diameter)
> 2) Inside hole (smallest diameter) -- usually in several passes so as not to strain the bit.
> 
> ...


 I agree, I think the only way is to use a guide and a rabetting bit. not really looking forward to it though:unbelievable:


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## evilskillit (Oct 7, 2008)

Flush mounting tweeters is always recommended if possible, tho I suppose if it were not possible then surface mounting tweeters would be better than not having tweeters at all .


Flush mounting a woofer is more cosmetic. Granted a surface mounted woofer close to a tweeter will cause some diffraction off of the edge of the woofer basket. But even if you do flush mount it you'll get diffraction as the wave from the tweeter rolls into the woofer basket, so not much difference there either way.

As for how to do it after the hole has been cut, yes you'll need a rabbet bit. I've never done it that way but as long as you get the right size it should work great.

Edit: Btw those sure are pretty. I think I might want to steal that design and color scheme for my floor standing 2.5 way.


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## Warmon (Aug 25, 2007)

You might also want to check out this investigation on surface mounting.


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## Brewski (Jan 8, 2010)

"Once the inside pivot hole is "gone" it's hard to make the recess. You can try a rabetting bit with a guide bushing, but be very careful."

Out of curiosity could a piece of wood be added across the speakers cutout to get the central pivot point back for routing with a jig? I was thinking about this more for a woofer but I'd think it could be applied to a tweeter as well.

Great looking speaker Johny good luck with the project.


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## lsiberian (Mar 24, 2009)

I think it's better if you take a measurement of your speaker's response before you make modifications. 

I've found the best way to flush mount a tweeter is use the jasper jig to cut the flush as well as the hole. Of course for my tweeters I don't know what I'll do since they are rectangular.


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## Anthony (Oct 5, 2006)

Actually, the more I think about it, a rabbet bit should work fine for the tweeter. The hole is small enough that the base of the router is supported on all sides and the bearing can do the guiding.

The only problem is that the adjustable rabbet bits are in fixed sizes and the the "lip" you need for the recess may not be one of the standard sizes, which would leave an unsightly gap. The hole jigs (Jasper, et al) are much more adjustable, but as mentioned, need a central pivot hole.

I guess you could cut a "plug" to fill in the tweeter hole and use that as a guide, if you were to go that route.

I do second the advice to measure the speaker response before cutting. Who knows, it might be pretty good now and not worth the effort.


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## CasePro (Dec 23, 2009)

Beautiful speakers. Agreed that the tweeter should be flush mounted. I also think that it is best to flush the woofer. One thing that hasn't been brought up is the fact that sound waves from the tweeter travel along the sourface of the enclosure towards the woofer. The lip of the woofer will create diffraction of the tweeter. If flushed it is more predictable.

As far as whether you should do it, I would say to weight the risk of damaging your beautiful enclosures vs the potential increase in sound quality. At a minimum I would practice on a spare piece of wood first to make sure you can do it.


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## evilskillit (Oct 7, 2008)

Plugging the hole would work, tho if you do it from the back the pivot might be a bit long and could wiggle.

Just some advice, whatever you do, cover the front with blue painters tape or something to help prevent the router base from scuffing that nice finish. Good Luck


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## fbov (Aug 28, 2008)

johnnyfamous said:


> ... from what i have read i broke one of the cardinal rules of speaker building, not flush mounting the tweeters. ...





johnnyfamous said:


> i read this on parts express website, ...


Johnny,
Without seeming flippant, do you listen with your eyes? How do they sound??

You've made a lovely pair of speakers, real eye candy, but retrofitting major mechanical features like flush mounting could destroy that. A rabbeting bit may seem ideal, but all I see are veneer tears all the way around your tweeter. Granted, that won't be visible behind a grill....

Speaking of grills, have you seen what a grill does to the anechoic frequency response? If you can't "hear" the difference the grill makes, you are not likely to hear the benefits of flush tweeter mounting. A lot of this is learning curve; you can always fix this later if you find it aurally objectionable. (I'm still waiting to hear the "lobing problem" with my CC.)

Then again, if you think the veneer's ugly or you really love wood finishing, far be it from me to tell you how to enjoy yourself. Just don't let what you read detract from your listening enjoyment, especially if the grills aren't audible. 

Have fun,
Frank


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## evilskillit (Oct 7, 2008)

FBOV probably has a good point, dont fret over stuff you can't even hear. I mean whats next? Are you going to worry that you didn't round over the corners?

I'm where your at on my first build, but it isn't nearly as pretty as yours, but the flush cuts are a bit rough and the front corners arent round. I decided to instead just build my next project. Then when its done if I want to go back and fiddle with my first ones, I can.


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## Drew Eckhardt (Oct 24, 2009)

Anthony said:


> Actually, the more I think about it, a rabbet bit should work fine for the tweeter. The hole is small enough that the base of the router is supported on all sides and the bearing can do the guiding.


A typical 1 3/8" diameter rabbet bit can't cut a rabbet over 1/2" wide (using a 3/8" bearing) and would duplicate the cut-outs for the tweeter terminals.

For a clear finish the simplest thing to do is to make a pattern with the correct diameter hole in it for the rebate, attach it to the speaker, and use a top bearing pattern bit preferably with a large router sub-base (I use my router table insert for things like this) that spans the entire opening (an offset base would work too).

For paint or veneer which has not yet been applied you can screw a cross-piece in to hold the circle jig pivot.

You could also use hot glue or double sided carpet tape to attach a cross-member behind the driver cutout to hold the circle jig pivot


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## lsiberian (Mar 24, 2009)

If you built these well then you will have better sound quality than a comparable commercial speaker. I'd leave the enclosures be.


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## johnnyfamous (Jan 21, 2009)

Thanks for all the input, appreciated!

if the affects are going to be inaudiable to me, i would rather not make the change, Parts express and Zaph make very STRONG recomendations against it though, so i thought the difference would be noticable to my uneducated ear, perhaps not!?

I dont really understand Graphs yet, but am slowly learning, I would love to do a measurment on them and see how they sound, but at present I dont own any equipment to take a reading, nor do i have funds to make any purchases of testing equipment right now. I did just download fuzzmeasure though.

I dont really understand what causes poorer response when its surface mounted, is it just delay? Could i just then tilt my speakers back slightly to produce the same effect?

They sound great to me. the detail in the highs is amazing, there is stuff there that i have never heard before! The base response is lacking though, without my subwoofer on there is a bit of warmth missing. 

the cabinet was built well, i did make a mistake there though, my measurment was off slightly on the box size, the plan called for a 0.900cuft box. and after it was all said and done i remeasured the internal volume and i am at around 1445 cu inches. my port length is 2 x 5 inches. is my base response due to the cabinet size? could i correct this by changing the port length?


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## CasePro (Dec 23, 2009)

Here is a good article about flush mounting with some graphs that show the difference.

http://www.rjbaudio.com/Audiofiles/flush%20mounting.html


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## dyohn (Apr 17, 2008)

If they sound good to you then don't mess with them. Seriously. The differences shown in most tests concerning diffraction may or may not be audible no matter what the graphs show. People get too hung up on graphs, IMO, and forget about what happens to them in the real world of someone's living room heard from 9 feet away and slightly off axis. None of the theoretical or anechoic graphs matter that much then.  

I am being 100% serious: only alter your existing speakers if you really just want a project. If you like the way they sound now leave them alone, and if you want to experiment with flush mounting I suggest buying a few drivers and some MDF and whip up a new speaker to play with.


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## johnnyfamous (Jan 21, 2009)

dyohn said:


> If they sound good to you then don't mess with them. Seriously. The differences shown in most tests concerning diffraction may or may not be audible no matter what the graphs show. People get too hung up on graphs, IMO, and forget about what happens to them in the real world of someone's living room heard from 9 feet away and slightly off axis. None of the theoretical or anechoic graphs matter that much then.
> 
> I am being 100% serious: only alter your existing speakers if you really just want a project. If you like the way they sound now leave them alone, and if you want to experiment with flush mounting I suggest buying a few drivers and some MDF and whip up a new speaker to play with.


I built these with the intention of using them for many years. So i dont have any issue spending a little time on them tweeking, or playing around to get the most out of what i have. I want to do as much Tweeking as possible. I Dont think i will have any issue with the veneer being damaged. I be carefull:sn:

I am more concerned with the development of remeasuring my cabinet volume and properly subtracting, port volume, woofer volume and bracing to only find out my box is to small, Not understanding the effects of what this will cause totally?

but most importantly what could i do to "fix" the not so good base response? Or is the missing low base just the speaker? I built a center channel using the same drivers but there are two 6.5 wired in parallel in a box volume of 1.25cuft, the mid response is much better and fuller, I assume because of two drivers instead of one? I have no complaints with the center,in hind site i should of built the same towers utilizing two drivers.

my cabinet internal volume is 0.83622 with a 2" x 5" inch port but should have been 0.900 cuft. what would this error in measurement cause? but more importantly what can i do?

Vifa P17WJ-00-08

Vb 0.900cuft
Fb 36.7 hertz
F3 40.9 hertz
Ql 7.0
fill Normal
Ports one round
Dv 2.00in
Lv 5.00

the box was lined with 2" of fiberglass, would a simple port length change make any difference?

i know the easy answer,, build new ones,,, but i like them and would rather tinker:rofl2:

I tried to download Winsid but it does not work on a mac:rolleyesno:


again your thoughts and guidance are appreciated!!

:innocent:they say stupid questions are the ones you dont ask:rofl:


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## dyohn (Apr 17, 2008)

The Vifa P17 was an outstanding woofer. If your enclosure is 0.8 cuft (about 22 liters) that's about right for the woofer, although your port at 2" X 5" tunes the enclosure to about 39Hz which is lower than optimal for the woofer (optimal would be about 48Hz in 22 liters.) Try shortening your 2" port to just under 3" long to raise the tuning frequency to 48Hz and you should have better bass definition. That woofer will never produce deep bass; you'll always need to use a sub with it if you want full-range response. But in-room you should get usable output into the 40's and excellent mid-bass performance.

What is the Xover topology to the tweeter?


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## johnnyfamous (Jan 21, 2009)

Here is what i have,???


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## dyohn (Apr 17, 2008)

Looks like a good design to me. Try adjusting your port and see if you like it better.


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## JCD (Apr 20, 2006)

I had an idea.. what about surrounding the tweeter with a decently thick felt ring? Would that help with the diffraction caused by the slightly raised lip of the tweeter? I know it's supposed to help with the edge diffraction caused by the hard/sharp corners of the baffle. Seems like it should help here too. It's a cheap fix that can be removed if it doesn't work. I'd love to see a before and after graph.


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## johnnyfamous (Jan 21, 2009)

I dont really want to start cutting down my port without totally understanding the effects. is anyone interested in moddeling the difference in port length from what i have now with what the difference would be by shortening the length or increasing it? or perhaps sending me in the right direction to calculate the difference myself?

if i read you right dyohn, if i increase my tuning frequency ( shorten port length)my mid response will improve?

thanks again.


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## evilskillit (Oct 7, 2008)

Here ya go. Nice big pic, shows the difference between the current 5" long port vs a 4" long port.


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## dyohn (Apr 17, 2008)

If diffraction is an issue with this design then yes, trying felt or foam surrounding the tweeter will reduce it and might improve directivity of the tweeter, if that's desired in this application.

As far as what raising the port tuning frequency will do, among other things it will "tighten" the response allowing better bass and mid-bass reproduction.

-edit- thanks for posting the model image!


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## fbov (Aug 28, 2008)

johnnyfamous said:


> ... but most importantly what could i do to "fix" the not so good base response? ...


My first thought is "how were they designed." I see nothing pertaining to this in your Madisound report, so ask if they are standalone or on-wall/in-wall designs. 

A standalone speaker, like yours, will need much greater bass output because it spreads that energy out over an entire sphere. The in-wall only feeds to a hemisphere, because any energy that wraps around the speaker is reflected forward by the wall. The correction for this is called baffle step compensation (BSC). Note that this is not a localilzed effect, as port tuning, but rather one that starts low and extends well into the midrange. A standalone design placed on wall is boomy; an in-wall design placed away from walls (as in your photo) is thin, with no body.

Is this effect audible? Extremely so! We're talking as much as -6dB at 100Hz vs. 1000Hz. The fix is either to put the speakers flush against the wall, or redesign the XO for free-standing use, or both. 

If you're pleased with the mid-bass through the midrange, then it might be box tuning. The port has no effect above ~100Hz and so is completely independent of BSC. Tuning is also not as sensitive as you may think; a 10% change in port length will be hard to hear without a trained ear. It can also be modified by adding/removing interior wall covering and polyfill, if you used it. 

My message is that there are lots of things you can do to alter bass extension, but they won't help a bit if the real issue is insufficient BSC. 

Have fun,
Frank


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