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#22860 - 22/11/2000 06:34 Another sub question
BryanR
member

Registered: 29/08/2000
Posts: 153
Loc: Berkshire, UK
Hi,

Well, I've had my Empeg for a few months now, and I must say that I absolutely love it! Mind you, instead of spending five minutes in front of my CD collection trying to decide what to listen to, I now spend five minutes flicking through menus on the Empeg... (and this is progress?)

Anyway, I've come to the conclusion that such a good stereo deserves better speaker quality than it's currently getting, so I've decided to add a sub.

At the moment I have a 4-channel amp driving two MB Quart 6.5" co-axials in the front, and the stock speakers in the rear (being the best I could afford at the time, after buying the Empeg).

So, what's the best way of approaching a sub? I don't want to spend a fortune (200 max, say).

My options seem to be:
1) Get an active sub (with built in amp) such as one of the Pioneer jobs - strikes me as being the easiest to fit.
2) Since I've got an amp in the boot already, I could stop using the rear speakers and use the existing amp to power a sub.
3) I could buy a new amp to run the sub.

I'd also want to be able to remove the sub fairly easily for those occasions when I need the luggage space (won't be that often, 'cause it's quite a big boot).

So, what should I buy (amps and subs)? Any suggestions gratefully received!

Cheers,
Bryan.

Mark 2 #080000515
12GB Blue

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Bryan.

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#22861 - 22/11/2000 06:56 Re: Another sub question [Re: BryanR]
rob
carpal tunnel

Registered: 21/05/1999
Posts: 5328
Loc: Cambridge UK
Toby got a small active sub from the Sony Xplode range - and contrary to my expectations it sounds really good! I'm sure he could be provoked to provide details (or give Cambridge Car Audio a call, which is where he got it).

Rob



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#22862 - 22/11/2000 12:05 Re: Another sub question [Re: BryanR]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31314
Loc: Seattle, WA
1) Get an active sub (with built in amp) such as one of the Pioneer jobs - strikes me as being the easiest to fit.

Yes, I have done this before and it is pretty easy to do it this way. However, the self-powered subs are usually characterized by the following:

- A barely-adequate amplifier.
- Cheaper driver(s).
- Ported enclosure to improve volume from the above two items.

After my self-powered sub got stolen, I decided to put together one of my own for its replacement. For the same price as I paid for the self-powered sub ($300.00), I was able to put together a prebuilt sealed enclosure, a better driver, and a more powerful amplifier. The assembly of these items was not much more difficult than putting the self-powered unit in place. In fact, the hardest part of the whole procedure (getting the RCA cables to the sub) is the same whether you build your own or not.

This new sealed unit sounds so much better than the self-powered sub because its frequency response is so much flatter. A ported sub, on the other hand, has a frequency "peak" right around the frequency of the port, making it sound boomy instead of smooth.

So if you're serious about the sound, I'd suggest going that route. Crutchfield can hook you up with all the stuff you need: Woofer, enclosure, amp, and all the necessary parts. And they'll make sure all the parts match each other.

___________
Tony Fabris
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Tony Fabris

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#22863 - 22/11/2000 20:24 Re: Another sub question [Re: BryanR]
borislav
addict

Registered: 30/04/2000
Posts: 420
Loc: Sunnyvale, CA, USA
2) Since I've got an amp in the boot already, I could stop using the rear speakers and use the existing amp to power a sub.

If you have enough spare power in the amp, you can put a front and a rear speaker in parallel on one channel of the amp. I did that with a 4-channel amp (bridging the remaining two channels to driver the sub) and I'm pretty happy with the result. One drawback is that you lose the fader control but for me the sound image is still in front, so I don't need it.

Borislav


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#22864 - 23/11/2000 02:51 Re: Another sub question [Re: tfabris]
BryanR
member

Registered: 29/08/2000
Posts: 153
Loc: Berkshire, UK
Thanks, everyone, for the replies.

I did think that with a self-powered sub I would probably loose in quality what I gained in ease of fitting. Not that I'd gain that much, because since the amp is in the boot already, I'd only need to route cable from it to a sub anyway. Even I can manage that! It was the journey from the battery and the head unit to the amp that I didn't want to do myself!

I think I'll pop into one of our local stores and see what they suggest.

Cheers,
Bryan.

Mark 2 #080000515
12GB Blue (and now Green)

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Bryan.

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#22865 - 24/11/2000 04:46 Re: Another sub question [Re: borislav]
teemcbee
addict

Registered: 04/02/2000
Posts: 687
YEP! This is the same thing I did and I'm very happy with that. Even though I'm a bit audiophile the sound seems perfect to me.

By the way another thing: The rear speakers are just for backfill. Just to make it sound rounder. So the frontspeakers should be quite high quality, the rear's are not that important.

TeeMcBee
Got my Mk2! # 080000143
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TeeMcBee
[orange]Mk2, # 080000143, 40+30 GB, Tuner, Peugeot stalk hookup</font color=orange>

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#22866 - 24/11/2000 05:54 Re: Another sub question [Re: BryanR]
teemcbee
addict

Registered: 04/02/2000
Posts: 687
Did you already thing about building a sub for yourself? That would be the cheapest way.

The shape or type of a sub can be very different.
There are following main types:

1 - the closed box
This is - how the name already says - a totally closed box with a single hole filled with a speaker. This type gives the best quality in sound but has not as much power as others have ( less dB than the same speaker in a bassreflex )

2 - the bandbass
This is the most complicated sub-construction. It's a box splitted into 2 chambers. One of these chambers is totally closed and in the splitting wall there's the speaker sitting and pointing to the open chamber. The open chamber has (usually in an angle of 90 degrees) bassreflextube. That's it. This construction is quite powerful but only gives a very small band of frequencies. So you get e.g. only the very deep frequencies and you'll miss some sound between the very low and mid-range frequencies.

3 - the bassreflex
This is similar to the closed box. The only difference is that (holding the same speaker) it's a bit bigger and has one (or more) holes with bassreflex tubes. This construction gives all frequencies quite good and is pretty powerful but in comparision to the closed box it's more noisy and so so clean

4 - the freeair
This is a simple speaker mounted somewhere without any build box around. The box around the free air sub is eg. the trunk itself. It doesn't sound that good and has not too much power.

Of course there are many differences in size and shape of the boxes. They can hold 1 or more speakers, the speakers can have different sizes etc. Generally you can say the bigger the size the better the low frequencies. eg. a 12" sub would play the low frequencies better than a 10" or 8" sub. But this also depends on the quality of the speaker, speaker-chassis, membrane etc.

I dared to build a box by myself. At first I had a bassreflex tube with a 12" speaker. But it was not very powerful so I calculated a new box - this time it was a bandbass box. I used the same 12" speaker in this box. It was a bit more powerful but you could only hear the very low frequencies (as described above) and it didn't sound too dynamic.
So I ended up building a closed box. This is what I have in my car now. It's pretty small and has a very clear and also powerful sound and I'm very happy with it.

Even though the building of a box is a very complicated thing and you have to know a lot about the speakerparameters and calculating the correct volume for your purposes (there are some programs for calculating subwoofers in the internet) it's not THAT important in my opinion. Maybe you wouldn't get the BEST result possible by building a box without calculating it's correct/optimal volume, but it's cheap.
Or you could also get a ready prepared box and you would just have to fit a speaker into it. That's another cheap way to get a good sub.

Good luck - and take enough time - maybe you could try some subs at a car dealer. Then you'll hear the difference and you can decide what would fit best.



TeeMcBee
Got my Mk2! # 080000143
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TeeMcBee
[orange]Mk2, # 080000143, 40+30 GB, Tuner, Peugeot stalk hookup</font color=orange>

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#22867 - 24/11/2000 06:44 Re: Another sub question [Re: teemcbee]
BryanR
member

Registered: 29/08/2000
Posts: 153
Loc: Berkshire, UK
I have thought about it, but 1) I haven't really got time, 2) I haven't got workshop facilities of any description (and I'd only get shouted at if I started this sort of thing in the kitchen!), 3) I'm lazy.

I intend to pop into my local car audio dealer in the next couple of days, to see what they can do for me. I'll fit it myself (which should save 50-odd quid).

One other question, and maybe a rather stupid one, but I'm new to all this: how do you fasten a sub in place? Do you have to bolt them onto the bulkhead or boot floor, or something? (He asks, his mind filled with visions of drilling through the petrol tank, causing an explosion that could be seen and heard from Lands End to John O'Groats..!)

Cheers,
Bryan.

Mark 2 #080000515
12GB Blue (and now Green)

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Bryan.

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#22868 - 24/11/2000 08:01 Re: Another sub question [Re: BryanR]
teemcbee
addict

Registered: 04/02/2000
Posts: 687
There are some kind of tape strips - ( sorry don't know the word for that but I'll try to explain):
On the one side they are glued and on the other side they burs. Like on some jackets or briefcases or things like that. Do you know what I mean?

So you stick them on the groundfloor of the sub and then put the sub in you trunk on the carpet and that's it. Easy to remove but it holds in every curve and on accelerating and braking.

Clear?

TeeMcBee
Got my Mk2! # 080000143
_________________________
TeeMcBee
[orange]Mk2, # 080000143, 40+30 GB, Tuner, Peugeot stalk hookup</font color=orange>

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#22869 - 24/11/2000 08:31 Re: Another sub question [Re: teemcbee]
BryanR
member

Registered: 29/08/2000
Posts: 153
Loc: Berkshire, UK
Like Velcro? Lots of little hooks that hold onto the carpet? That's a cunning plan... I assumed it would need to be rigidly attached. Far simpler if I can just velcro it.

Thanks for your help - I'll try and get something sorted out this weekend.

Bryan.


Mark 2 #080000515
12GB Blue (and now Green)

_________________________
Bryan.

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#22870 - 24/11/2000 08:35 Re: Another sub question [Re: BryanR]
teemcbee
addict

Registered: 04/02/2000
Posts: 687
YEP! That's what I meant. Geeee! My english vocabulary is so bad!!

Good luck!

TeeMcBee
Got my Mk2! # 080000143
_________________________
TeeMcBee
[orange]Mk2, # 080000143, 40+30 GB, Tuner, Peugeot stalk hookup</font color=orange>

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#22871 - 24/11/2000 09:30 Re: Another sub question [Re: BryanR]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31314
Loc: Seattle, WA
Like Velcro? Lots of little hooks that hold onto the carpet?

Yeah, that's how my sub is held to the floor of the trunk right now and it works like a charm.

Note that it only works because I have a hatchback-shaped box (sort of a pyramid shape) with a flat bottom. There are some subwoofers shaped like a cylinder, and those require mounting straps (which come with the subwoofer).

Regarding the idea of building your own: Remember that you can purchase prebuilt boxes like the Q-logic ones and simply drop your own speaker into them. You can get sealed, bandpass, whatever. That's what I did and it was quite easy.

___________
Tony Fabris
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Tony Fabris

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#22872 - 29/11/2000 12:38 Re: Another sub question [Re: teemcbee]
john
stranger

Registered: 22/07/1999
Posts: 37
Loc: London, UK
I've had a bit of experience with building subs recently, as well as a grounding in the theory behind their operation. My findings are quite different to what you find on most web pages.

Building a sub involves trade-offs between:

- Reducing driver excursion.
- Increasing efficiency.
- Lowering cutoff frequency.
- Reducing the size of the enclosure.

And like anything derived from good physics, you can't have all of them at the same time :) Well, you can, but you end up with VERY large enclosures. A friend of mine suggested that the ratios between size, efficiency and bass cutoff is very approximately:

- Half bass cutoff = 8 times the required volume(size)
- Half bass cutoff = 1/4 the efficiency (-6dB)
- Twice the volume = twice the efficiency (3dB)

And a very approximate "reference" sub: 100dB SPL : 100 litres : 100Hz

Given that, I start with an approximate maximum size of sub - in my case a 90 litre enclosure. Then sort through a list of drivers applied to an enclosure of that size until you find one which gives the required Hz and SPL. You cannot get a driver which has the same Hz but higher SPL. If you find one, the manufacturer has some bad figures. It is not possible to have "higher efficiency" drivers at bass frequencies.

Enclosures are all about dealing with the rear wave. I've got a ton of stuff about enclosure choices to write, but I'll save that till tomorrow (beer beckons). Basically, 6th order bandpass boxes are amazing things:

- Transient response is as good as a sealed enclosure. Don't believe me? Create a good enclosure and see that group delay follows closely the delay of a sealed enclosure, up to where a sealed enclosure would have stopped producing bass. From there on, the group delay becomes bad, but hey the sealed box wouldn't be producing that bass would it? And it's usually less than 20ms, so you probably won't even notice it.

- Bass response is excellent. You can shift the parameters that a driver determines by quite a lot (cutoff, sensitivity, bandwidth), leaving a lot of design freedom.

- Excursion control is excellent. It's a shame people quote frequency response as the determining factor. It's not. The true maximum SPL a sub can generate is the minimum of max excursion and max wattage at a frequency. This makes sealed boxes have much much lower maximum SPL at low frequencies. And because excursion is lower, so is distortion - another thing people usually attribute the other way around!

- Lots of freedom in enclosure design. You have two ports, two partitions and a driver to play around with. You can generate pretty much any frequency/excursion graphs you want provided you can find the drivers.

Food for thought :)



- John (from empeg)

(The above may not represent the views of empeg :)

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#22873 - 29/11/2000 13:55 Re: Another sub question [Re: john]
mardibloke
addict

Registered: 14/08/2000
Posts: 468
Loc: Penarth, UK
. . . but I'll save that till tomorrow (beer beckons). . .

. . Food for thought . .

Ha ! All the qualifications to be on the empeg team eh ?


- --
Rod, UK Mk2 64gig Red S/No.341
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Rod, UK

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#22874 - 30/11/2000 04:30 Re: Another sub question [Re: BryanR]
Paul
stranger

Registered: 01/04/2000
Posts: 30
I have heard good things about the small active subs from sony but i maybe being stupid here but surely with an active sub you have to feed it with both power and sound signal so it would be a bigger pain to remove than a ordinary sub with just the speaker cable going into it.

As to being easier it fit if you have run all the cables to the boot the hard stuff has been mostly done providing the power cable is heavy enough


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#22875 - 30/11/2000 07:59 Re: Another sub question [Re: john]
BryanR
member

Registered: 29/08/2000
Posts: 153
Loc: Berkshire, UK
Thanks to everyone for their advice! I decided that building anything was beyond me (lack of tools, space, time and ability), so I decided to see what I could find in the area.

Well, I went into my local car audio dealers yesterday (the ones who fitted my Empeg, amp and front speakers), and after a bit of a chat and a listen to some of their subs, I got what I think is quite a nice sub in a pre-build sealed enclosure. I've sacrificed my rear (stock) speakers, and wired the sub into the spare channel on the amp.

It's certainly a huge improvement in sound quality, and since it's running off my existing amp it was a two-minute job to fit (and even quicker to remove when necessary).

Actually, speaking of the car audio dealer (Berkshire Car Sounds in Reading, FWIW), I noticed that they have an Empeg sticker in their door window...

Bryan.

Mark 2 #080000515
12GB Green (was Blue)
...but I've only got 2GB left to fill!
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Bryan.

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#22876 - 01/12/2000 03:44 Re: Another sub question [Re: BryanR]
Paul
stranger

Registered: 01/04/2000
Posts: 30
Very good choice you can have an great sounding system with just front speakers and single sub in the boot.

But i'm a moron so i wll be going for front and rear speakers and two subs in the boot a big one and a little one


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