A while ago I acquired a full set of Scanspeak revelators

6.5" midbass/midrange (18W8531G00)
4" midrange (12M4631G00)
1" tweeter (R2904/700000)

this will be run full actively from my v12 amps (545 and 345).

I will be bulding a full fibreglass and mdf enclosure in my door for the midbass, this is mainly because the speaker is designed for home use and won't do well in a door envirnoment (moisture etc).

First question is about positioning the midbass is definitley going in the doors. Should i put both the tweeter and midrange (playing form ~500Hz up) in the a pillars.

Or should i put the midrange in the kicks and the tweeters in the a pillars?

Also if i decide to port my midbass do i have to tune it to the same frequency that my subs are tuned to?

if i tune the midbass higher will there be phasing and blending issues with the sub?

Cheers

Lindsay

I would think that there would be separation issues with a midrange and tweet separated.

No idea about any of the other stuff.

Good luck with the instal

The midbass, if you keep it non-directional, can go almost anywhere up front. The doors are good, the floor/kicks are better (for vibration control). Preparation of surfaces and installation will give you the best response.

The midrange can go whereever you see fit to install them, and gives you the best response. Placement of this is the most important. Lower tends to result in deeper soundstages, sometimes wider, but sacrifices stage height. Higher tends to result in better stage height, at the cost of width. Depth can be controlled by placing the tweeter carefully here. Note these are general, as good placement can give you everything, and cost you nothing (with time and effort).

Tweeters go where they sound best. They DO NOT need to be next to the midrange, just like the midrange DOES NOT need to be next to the midbass (seperation will occur there too, if you're not careful). They go where they sound best. It really is THAT simple. We only make it complex

In the end, it varies from car to car. Try some places, and work around them. See what gives you the most enjoyable experience.

Question though. Why choose to port the midbass?? This may be more effort then its worth Im afraid, it just depends on what you want to get from it. Also, Id be dropping the Xover frequency between the midrange and the midbass a little too. 500Hz is dome territory. You're cones should easily be able to handle a full octave lower.

I presume you have time alignment available, and therefore can correct delta anomalies.



The doors are a good place for mid bass (enclosure size) Porting is a great idea, especially for extended lower bandwidth. If your sub is ported also this should help integrate the two networks. Failing that, consider a 24 dB slope on the sub woofer.

The mid woofer should not be operated above 250 Hz unless perpendicular to the listening position. Our auditory system becomes highly directional by 500 Hz (Able to detect 1 degree from directly in front), although if they are perpendicular (cone of confusion) we cannot locate them below 500 Hz.



The mid range determines ALL your depth cues for stereo. The most important aspect is the angle from the driver position (Ideally 60 degrees, but we live in the real world.) I would recommend the kicks, with a suitable baffle and attention to wave guide techniques (directional control) for best results.Try to use the wave guide to reduce floor to roof reflections and the "dreaded" centre console. I am unsure of your ideal frequency bandwidth for this. A 4 " midrange should not have significant off axis response degradation until 4000 Hz (Beaming) so the aiming of this is not crucial, unless you wish to use the tweeter as an "ambient". (5000 Hz and above.)



Tweeter is going to best in the kicks for width, consider inverting the phase mandatory.

do u have the linky for that HUGE post u did on the NZ forums about speaker placement? i cant seem to find it and there would undoubtedly be heaps of feedback from everyone here.

Ive got a copy.....

Abmo edited and removed all his comments from that thread last year. Lucky I saved them....

Feel free to share

does he mind if u share em?



that was the most informative thread. i wish i'd saved em

Ill only post it if Dean doesn't mind. Though I reckon he removed his original comments for a reason....

I would prefer you did not post them up.



We could run a thread on it at some stage. It is good to see interest in the most important aspects in car audio. CAA (Yes it is now MEA) got stuck on the what power amplifier etc "merry go around" for some time. When you consider a source unit, power amplifier etc can measure under 1% THD, and speakers are normally 10 % as a starting point, it isn't rocket science to evaluate where to spend your time and effort. There is little argument of audible speaker differences. Speaker placement is always a compromise, however if you use the early reflections (baffle diffraction AKA wave guide) considerable gains can be had.

Understood. Incredible thread at the time though.

To have something like that occur over here, well, it would be worth its weight in gold.

whats the chance of all putting in a few quid and actually renting abolech's brain for a week or so, and transcribing all the most amazing info in there into a massive thread...

I'd pay good moneys for that sort of thing. especially at a time when I'm considering exactly how to construct my kickpanel enclosures...

I'm in for a fiver at least

you'll be converted to mono.. can you deal with that?

fair enough. im sure you have ur own reasons.

PMSL

x2

I agree though on this topic.
I have my mids practically screwed to the firewall at the top of the kicks, and angled carefully to give the best 'centre image', using the under-side of the dash as a waveguide .

funny though, it took me 18 months to figure this out - and another 6 months to appreciate how good it is (I'm still playing with crossovers and phase, and still making improvements without moving the speakers).

I have heard midbass in doors, floor, and kicks - I prefer doors for the larger enclosure, but floor is my second preference.

tweeters - wherever sounds best, once you get everything else right.

Kinda on a sidenote here but anyway, with hifi speakers such as Scanspeak and Vifa, as they are not designed for a car environment (as pointed out already) is it compulsary to put the mid bass in its own enclosure within a door cavity?


I guess this is to replicate a typical hifi enclosed box? And to protect the gear from the 'elements' (aparently hifi speakers aren't built with exactly same materials...but don't hold me to that! haha)

Cheers,

jas.

Pulse-R> Can you pls explain what a waveguide actually is/does and how ur underside-of-dash acts as one.

ok this is goona take a whle to sink in, excellent info.

providing it is ok with Dean would i be able to have a copy of his post matt?

agree simon could you elaborate on the waveguide and perhaps a picture of where its mounted?

the only tuning tool i have atm is my 9853R (two way + sub TA, 5 band parametric and crossover)

may get a 701 in the future though.

Cheers

Lindsay

I'm pretty interested in learning about this too..

The waveguide effect is when the sound follows a contour to give more even dispersion of the sound - a bit like a horn - and can be good if used properly.

a picture
Click to view attachment

so the under-side of the dash helps to focus the sound at your head (the red circle).

The mids are at the firewall - maximising stage depth, and using the curved shape of the under-side of the dash to help focus the sound.

Stick with SQ Simon...

Your MSPaint skills are lacking LOL

Lindsay, you (will) have almost the same setup as me.

I have 3 way front active (6.5", 4" and 1" ) running actively off my 9835 and 2x MRV-F545's...

how do u plan on setting it up? its all possible, but you must compromise on the TA channels of the HU and 'group' one set together...

ive experimented a little and ended up putting the 4" and tweeter on the same TA channel, and mounting them together...

as for crossovers, set the HU to 3 way mode and go:
Low = Sub = LP (for example, LOW = LP 80hz, 12db)
Mid = 6.5" = BP (for example, MID-LOW = HP 80hz, 12db, MID-HI = LP 400hz, 12db)
Hi = 4" + 1" = HP (for example, HIGH = HP 400hz, 12db)

as an example setup:
* run the low preout to the sub amp (545 rear ch?), amp crossovers off, use HU crossovers (examples above)
* run the mid preout to the mid amp (545 front ch?), amp crossovers off, use HU crossovers (examples above)
* run the hi preout to the 4" + 1" amp (345?), into ch 1 and 2. then flick the 'input selector' switch to 1 and 2 (i think?) which will 'copy' the signal to the rear channels. tweeters off 1 and 2, 4" off 3 and 4. run a HP filter at the amp (eg 3.4khz), at ur desired freq for the tweeters, and a LP (eg. 3.4khz) for the 4", at the amp.

this will give you independant TA control over the sub, 6.5", and the 4" + tweeters together...

with the 4" + tweeters together, they can be TAed together fine (best compromise with the given equipment)...

basically, get the install perfect the first time, and set it up this way for best results (from what ive found)...

ive stuffed up my install the first time with the door pods, and mounting the tweets and 4" seperately (which wasnt a problem at the time, as i didnt have TA) but with TA, and the 4" further back, it drags stage down and back. then combine that with the TA, and the tweeter mounted forward of it, and about 25cm away, TA becomes ur enemy as its hard to get it right, IF at all...

from what ive asked about my install (and the best way to set it up) i was advised to go down that route, and put the 4" and tweet together, as the 4" and tweet would 'generally' be TAed together (or very close together) anyways...

put the 4" and tweeters as far forward as you can get them. in the kicks would be ideal, but now this means that the tweets wil have to go there aswell. unless u have the room to put the 4" and tweeters in the pillars haha...

Does that mean that line-of-sight is not necessarily needed from your head to the mids? Because the waveguides are 'guiding' the sound out from underneath the dash and (in some cases) drawing/lifting it up to the listener?

I actually thought he did pretty well.



Technically speaking, all waveguides are horns, with different dispersion patterns which differentiate them from the generalised definition of a horn.If a baffle therefore increases efficiency dramatically, it is considered a horn. If the baffle marginally increases efficiency and directs the wave it is termed a wave guide. A waveguide is a an acoustic device that transforms the radiation characteristics of a speaker driver.One significantly different characteristic of a direct radiator driver is it radiates directly to the air, unlike an acoustic loaded baffle, it has mono modal propagation, this means that it can only propagate sound in the longitudinal mode and this happens at a constant velocity.



The idea therefore is to create the ideal (or more ideal) impedance medium to transfer energy from a high impedance (driver radiator) to a low impedance (air).



The narrow end is called the throat and the wide end is called the mouth, and depth related to both the throat and mouth is the rate of expansion. A waveguide has a very rapid expansion from throat to mouth, in the extreme, a flat baffle is a waveguide with the most rapid expansion. Here the radiation pattern is hemispherical for wavelengths where the baffle is large compared to the wavelength of sound. In any case, for a waveguide to be effective, the dimensions of the mouth must be large compared to the wavelength of the lowest frequency of operation. For frequencies lower than this, the waveguide becomes invisible and the driver operates as if the waveguide wasn't even there. Since the size of the mouth and the depth are "predetermined" by the car, the only other design constraint the reflection back into the throat,the transition region needs to be smoothly terminated in order to avoid sound waves reflecting back down the waveguide and causing interference effects.



By using these areas as a wave guide we gain:



Better acoustic impedance match (reader higher SPL output, money for jam )

Less interference from obstacles (read legs)

More directivity control (less combing)

Better near field listening

Reflections are used as a gain instead of a minus



But most importantly



The chance to say I have a "wave guide" and wow the newbies





Hope I haven't stepped on your toes pulse-r

Just had to correct one thing

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Click to view attachment

PMSL!!!!!!

REFLECTIONSAAAAAAA!!!

abmolech: I wear steel-toe boots
and you are right - to use unavoidable reflections as an advantage really works.

Does that mean that line-of-sight is not necessarily needed from your head to the mids? Because the waveguides are 'guiding' the sound out from underneath the dash and (in some cases) drawing/lifting it up to the listener?

Extreme apologies Iceman_jkh, thats twice you have had to ask the same question.



Yes.



A horn often has no line of sight, yet is capable of redirecting the wave.



Huge bonus. A normal radiating driver can "steer" waves by having a radiating surface width or height, that is close to the length of the frequency being produced. (known as beaming or off axis response) The difficulty for us, is not that we must keep the driver on axis to reduce response (although it can be a problem) but we cannot often use this to "steer" the wave from harmful interference (read centre console, floor to roof, etc).



This is where array's, wave guides (or combination there of) and horns can help. We can direct the wave away from some of these surfaces.



In my opinion (especially in a car) a wave should be kept in a baffle (wave guide) for as long as practical.

You still need line-of-sight for higher frequencies, but certainly helps to keep the lower mids up high with the tweeters.

Sexy gear - would love to hear it in action



Any reason for the mid-bass being crossed so high? My 4" Vanadium mids have no trouble playing down to 250hz, and I can't imagine the Scans would either. If the mid-bass and midrange/tweet are going to be seperated (which seems to be the case) then I'd be crossing the mid-bass over as low as it can comfortably play so minimise directionalism (new word!).

Aside from that, our ears are still pretty sensitive in the midrange and lower treble regions, the often the mid-high transition is the most noticable and most critical. Whatever you do, I'd avoid seperating the two if you can at all. One of the big advantages of a seperate mid in a three-way system is it's easier to get into those 'hard to reach places' then a large midbass.

That said, i know the Scanspeak tweeters are large units (my brother has some in his car) so I understand how fitting the two units together in one place could be a challenge - especially with the mids needing an enclosure.

If you cross the mid-bass lower (~250hz), and if you have enough room for an enclosure, then I'd suggest trying to get the mid and tweeter both in the pillars and see how you go.

If your mid-bass crossover point has to be higher (~500hz) then I'd strongly considering getting both mids and tweeters in the kicks and using well thought out ambients for height (if necessary). Otherwise, the seperation between mid-bass and midrange may cause too much drifting of the image.



My brother toyed around with this in his car. He built up slot ported enclosures for his Peerless mid-bass drivers but it didn't have quite the effect he expected. He did properly model the enclosure before building it so it was built to spec, but still it seemed to act more like an air leak then a port hurting his midrange and mid-bass output. He has now sealed it off and claims it sound much better.

In his case he is running a two-way front end, so the drivers are playing up from 100hz or so up to around 1.5k - this could have had part to do with why the ports did more bad then good not sure.

Edit:
Just read the rest of the posts, some interesting info there