john banks

You may have seen my earlier posts about my first major install in the Scoob, but now I'm getting "used" to it (a bit like the turbo!) I am looking at further improvements.

In the front doors, my speakers went into the plastic spacers with just a little trimming of the splash guards. Does anyone have experience of a before and after changing to MDF spacers. I am wondering if this might improve mid-bass response - or am I getting obsessional? I am even wondering (blasphemous I know) about now adding some rear speakers to help a bit at really high volumes - although I don't know whether it is my ears or the speakers that make it a little uncomfortable - certainly there is no sub-bass problem - it is the mids and highs I think that sound a little strained - or maybe it is the physical structure of the car just complaining despite sound deadening city!?

My system - Kenwood HQ167DB front spkrs (93dB/W, pk pwr 220W, rated 50WRMS, 16cm coax) with good wire to 50WRMSx2 of Kenwood amp with other 150WRMSx1 bridged to a Pioneer bandpass box. 5080R Headunit. Factory rears. 100Hz HPF fronts, 80Hz LPF sub both 12dB/oct.

It was the bandpass box that I thought would be the most dodgy part of the system, but it is amazing - it's manual suggests a LFP rating of <=80Hz as it's response drops off from 120Hz quite steeply.

I could prolly put the HQ167DB in the back shelf off the HU, and could consider some components for the fronts.

Ideas for components - good sensitivity, able to take shed loads of power (ie 100WRMS contin). My amp manual suggests using speakers with a continuous rating of 100W even though it "only" puts out 50WRMS contin 100W "peak" (however you define peak).

Thoughts?

Richard Gledhill

To be honest it's probably the amp complaining. Japanese amp manufacturers grossly over-quote their power output - ofen they could only manage their "max" output for a split second and with horrendous distortion. If you look at amp details, they often quote power outputs at up to 10% THD (Total Harmonic Distortion). The ear can hear distortion from around 0.04%! 10% is unlistenable to. A decent amp will be able to provide its power rating at <1%THD and continuous.

I have a Rockford Fosgate amp which is quoted at 4x100W RMS into 2Ohm. This was verified on a test bed where they ran it continuously - giving out 512W RMS total (i.e. it exceeded its quoted value). In comparison, a typical 300W Japanese amp is likely to be nearer 100-150W max continuous at listenable-to distortion levels, if you're lucky.

So I'm afraid that at 2x50W and 150W bridged (I assume they're off the same amp), it's probably that that's complaining.

As for the speakers... when speakers are run too hard, the bass in the sound can cause the cones to run out of travel (at suprisingly low volumes in fact) and then you will get distortion. However, the distortion is apparent in the mid-high range, where it sounds like the song is being "strangled". If this is what you are hearing, you might be best setting the HPF higher for the fronts to protect them, as at high volumes there may be sufficient <100Hz coming through. I have Xtant fronts, which take 150W RMS and can withstand the bass, even at the volumes I occasionally listen to the system at To complete my set-up, I have a Rockford Fosgate Power DVC sub.

Back to your original point! Putting in MDF spacers won't make a lot of difference. The main thing is to hold the speaker as rigidly as possible, and seal it against the reflected sound wave that comes off the inside of the door panel. As long as yours is sealed (using the splash guard normally), it should be fine.

I'm surprised you haven't blown the factory rears - they're only rated at about 25W (IIRC). They will be complaining big time - I'd just file them away until you need to sell the car Leaving the gaps where they went open will allow the sub to vent into the cabin, which improves the bass.

If you're after more sizeable components... well, price is the biggest issue here. MB Quarts come out nicely, Rockford Fosgate FNXs are very strong and clear. I like Xtants, but then again the RRP is £450 a pair (not what I paid though!)

Well, you wanted some thoughts! Hope this helps, but probably just gives you a hundred times more questions and options than before

Richard

john banks

Thanks for the reply Richard. Thankfully the factory rears are only powered off the headunit otherwise they would have been toast long ago!

I hadn't thought the amp might be the weak spot as it was the most expensive bit of the system (£250 RRP £160 paid) and quotes 50Wx4 at 0.08%THD contin all channels driven (doesn't quote freq range) which sounds quite respectable. Speakers were £72 pair (£120 RRP) although the most powerful in that size that Kenwood did (even compared with components - which had lower sensitivity).

HU seems to put out 1VAC on my voltmeter at max volume from the RCA. Front channel setting at 0.3-0.5V setting as otherwise it sounds like a mouse. Starts to sound "strangled" at settings of >25/35 on HU although with the sub (which is only supposed to take 100W contin) on the bridged channels (claimed 150W contin 0.8%THD) at MAXIMUM sensitivity it just loves it and sounds incredible (apart from the spoiler vibrating from outide the car - strictly high speed use only - would be v embarrassing and anti-social in town and I would let down the good image of Scooby drivers ) The amp and sub never shut down (both are overload protected) under these conditions, which is what is making me wonder if it is the fronts that are lacking.

So what you have said about the amp Richard makes me now wonder how I can tell where the weakness is... one to have a think about.

It is interesting that a £120 Prologic receiver 60WRMSx2 (+ a few rear speakers) in the lounge with some £199 Eltax Symphony floor standers sounds **much** better. Oh well, I suppose it is the poor acoustic environment of the venerable (in other respects) Scooby.

It would be great at some point to hear some of your installs - no one at trackdays so far seems to have any other than standard audio or new HU as far as I have discovered (they get their tunes from Scoobysport et al and I can see why ).

I am near Edinburgh - I heard there might be a Fife/Dundee meet next w/e, but unfortunately I am working. Anyone else nearby, esp with any interesting ICE I would love to meet up with.

[This message has been edited by john banks (edited 29 October 2000).]

john banks

I changed the HPF setting on the fronts from 100 to 120Hz and the LPF up to about 85Hz and it sounds **MUCH** better at high volumes. So I guess it might be the cone travel problem. For now I don't think I'll need to upgrade - thanks for the advice.

BTW, a few calculations - are these correct?:

12dB/oct filters, therefore 3dB for 1/4 octave. Since 3dB is a halving in power, then I needed a point where the two x-over curves would meet at -3db therefore 1/2 octave between x-over points. 2^0.5 = 1.414 (since an octave is doubling in freq). Hence theoretically I reckon the correct setting of HPF = 1.414 *LPF hence 85 & 120Hz approx. It sounds good too - if I put more distance between the settings it sounds like there is a "flat" spot. Or am I imagining it and going mad again?

I have probably just spouted a complete load of rubbish - please correct me

[This message has been edited by john banks (edited 31 October 2000).]

Richard Gledhill

Glad to be of service! Sounds like Kenwood are learning, and are quoting decent figures, so that's probably not a problem.

Impressed by your maths - you are indeed spot on with these, which is why it sounds so good. It's also why many amps have LPFs set at 80Hz and HPFs set at 120Hz - near enough your (more accurate) values.

And I agree with the spoiler vibration problem! We recently had a Cambridge meet, with a drive around Cambridge (and I mean round the outside on the country roads!), stopping at a pub. I'd just finished fitting my grand's worth of kit and a few people wanted a listen. Sure enough, with Madonna's "Music" on loud, the back spoiler does vibrate rather... didn't half sound fantastic inside the car though - hair on the back of my neck standing on end with the SPL and no trace of distortion anywhere in the system Beautiful.

I'd love to compare systems, but living in Cambridge would make it a bit of a trek! If you're ever down at Donington Park or one of the other track days, let me know and we'll arrange to meet up there.

Keep playing and enjoying

Richard

[This message has been edited by Richard Gledhill (edited 31 October 2000).]

rockin'Ru

What's the dampening factor of the amp?That factor greatly influances bass response.Around 200 is average.Also,if you're lokking for a more powerful mid-bass or transient response from the fronts,put in a pair of foam baffles.They're about $8 a pair through Crutchfield and are a cinch to install and will improve the speakers overall response tremendously.I myself just don't like the sound of the "infinate baffle" concept.It just doesn't sound good,IMO.
Just a thought.

john banks

Not quoted. Baffles sound interesting - not heard of these before. Do these baffles go behind the magnet and form some kind of seal?

I was also wondering about some rear midbass drivers (since bass is not that directional) to reinforce the rather peaky bandpass response. I would put a bandpass filter on the midbass drivers so as not to bring the soundstage backwards, and could run the amp at 2ohm (with the front & rear off the same output in parallel) for 50% more power. Or I could run them off the HU. 6x9 might do the job here? Could this be the true role of these beasties in a car with a sub?

[This message has been edited by john banks (edited 01 November 2000).]

rockin'Ru

John,I'm not too good with this computer stuff yet[32 years old and no excuse]but this should show you what these baffles look like.Here goes.
ProdPic.asp?i=237XT42&q=&o=atwww.crutchfield.com
If it doesn't work,do a search on crutchfield.It's a mail order company in Virginia,USA.The company that makes them is called XTC I think.
All you need to do is take the speaker out,unhook the wires,poke a hole in the baffle for the wire,re-connect the speaker and put the speaker back with the baffle behind it.They're made of foam[like a cup with a lip]and will conform to what ever's behind the speaker.Couldn't be easier.They'll allow the fronts to handle down to 50 hz,adding "depth".A word of advice as far as the front stage goes,if you can afford it,go with genuine components.If you can't,you can add a pair of inexpensive separate tweeters to improve imaging.I can't stress enough how much of a differance separate tweeters make.It totally changes the sq of the entire system.
You can keep the factory rears.I have a P7000R Pioneer hu that has a bandpass[adjustable] filter built in,it's called FIE[front imaging enhancer]that cuts off the rears at 100-160-250hz.I personaly would like a little higher,but sounds excellent.That would allow you to retain the factory rears on hu power.They're only meant as an echo,like off the back wall of a concert stadium.Concentrate on your fronts.If you can drop the fqz response in the front down to 50-80hz in conjunction with your sub,the system will come together seemlessly and probably get you stemmy for a minute or two.
If everything's right,you can sit in your car and close your eyes and just disapear,you're there.There's no real point of sound[i.e.,it's hard to pin-point exactly where the speakers are.]A seemless blend.
With just door speakers,no matter what brand or type,can never compare.You'll always have that empty space up in front of you[where the windshield is],a simple pair of tweeters can remedy that.Otherwise all the sound will be coming from your ankles.
Sorry for the book John.I love music.
Hope I helped a little.

rockin'Ru

One other thing I forgot,you mentioned "peak" power up above;well generally an amplifier has an rms rating and a dynamic rating,and then a max rating.RMS ratings are usually the advertised[on the box] power ratings at a given voltage.Good quality amps put out advertised wattage at about 12.5 volts[battery voltage],and the same amp being fed 14.4 volts[normal car voltage from the alternator]will put out considerably more wattage and blow an alledgedly compatible speaker.Cheaper equipment just doesn't have a dynamic power output because they've already listed the amps maximum rms wattage at maximum voltage input,and any attempt to squeeze more power from it results in some really nasty sounds[distortion].
Example:I have an MTX 4300x amp that was advertised as putting out 37.5 watts x 4 at 12.5 volts.When I got it,the"birth certificate" said it actually puts out 68 watts x 4 at 12.5 volts,and 90 watts x 4 at 14.4 volts[dynamic power].
That's why they recomend you have at least 100 watts rms speakers,just in case you run a very good charging system[a constant 14.4 volts].

john banks

Amp quotes 100W x 4 Maximum, 50W x 4 RMS 0.08%THD all at 14.4V. I'll look at these baffles at home - web block at work prevents many sites

It seems that if I had a sealed or ported box rather than dual bandpass sub box, the 100-200Hz range might be stronger. As it is the sub when in it's freqency range is so phenomenal I think it would show up the response of many cheaper midbass drivers.

Do the baffles need an airtight seal?

rockin'Ru

John,as far as the baffles go,they have a dual purpose,1,they protect the back side of the speaker from any water that may get inside the door,as well as dust & dirt,and 2,they supply the driver with some back-preassure.No,there's no sealing involved.They're made of foam so they won't give you that nasty "tinny" sound that you get with a very small,hard enclosure.It's a simple modification that just can't be beat for a mear $8.
Also,if you have a circular saw and a jig saw you could experiment with a different box.I prefer the acoustical flexability of a sealed box myself,they'll cover a wider range of fqz's better IMO.If you were willing to buy 1 sub,say a Pioneer 10" or a 12",you could build a box for it[1.5 cubes for the 12"]and run it sealed.If you want a tighter sound from it,take the driver out and put in some styrafoam to take up a little space,making the internal volume smaller.Keep playing with it until you find your own ideal sound.
Try the baffles first and see how the sub interfaces with the new acoustics in the cabin.You can also put some baffles on the rears to.It would really clean things up.If you find them[at crutchfield]and see them,you'll understand how they work immediatly.
Keep us posted!

john banks

The baffles look great. I tried to order them from Crutchfield (online and on the phone) but they do not deliver overseas!

I have enquired with a local ICE supplier to see what he can get.

rockin'Ru

BUMMER!! Sorry John,I didn't think of that over seas stuff.Take a look around and see what you can find there.How much would it be to ship to you?

john banks

Don't know what shipping would be, but if I had no joy here I was considering asking you to send some over if I sent over cost+shipping+beer(or whatever) money, but then I thought how the hell do you send money overseas ?are there any international postal orders etc?

rockin'Ru

Did you say beer?Heheh.I'll have to stop at the post office and see what's up with it.They're only foam so they shouldn't cost much in shipping,but overseas,not sure.
I'll let you know.

rockin'Ru

One other thing,where are you?Need to know.E-Mail if you prefer.

john banks

Scotland, UK.

rockin'Ru

John,I stopped at the post office and it's not too hard to send the stuff.The baffles are $8 and 4.95 shipping from Crutchfield,and the post office can ship 1 pound by boat for about $8.A 4 pound package by air for around $22.
Let me know.

john banks

Thanks very much. I'm still interested. I'm working all this weekend - crazy junior doctor exploitation 56hour thing but I'll e-mail you from home on Monday.

Probably the boat delivery would be best. I think the baffles I need are the smaller ones for 6-1/2 inch speakers - the mounting depth is 59.5mm. The actual depth I *think* is 83mm, but I think by the looks of them the depth we need is from the screw holes to the back of the magnet - ie the mounting depth. I'll look in more detail at the site when I'm home and can access it rather than battle with the web nanny thing at work -thankfully it allows scoobynet!