First DIY - bi amped 2-way standmounts

valleyman

Member
2008-02-07 7:21 pm
Hi

I've been lurking here for a while, reading and absorbing the info on offer and I think it's time for my first post.
I'm a student at the moment and term ends in a few weeks then I'll have 6 weeks off some of which to devote to this project, so despite this being ambitious for a first project I think I'll be ok as I have plenty of time.

The idea is to go with an active crossover. I have picked the Behringer CX2310. I can pick it up here in the UK for £60 and by all accounts it's a very decent piece of kit.

For the amplification I have a Harman Kardon HK680 whose bass reproduction I love so much I won't part with it so that will be driving the midbass driver.
I have yet to decide between a T-amp and an LM3886/3875 for the tweeter.
I have seen some debate between these two, but would be glad to hear peoples thoughts. Given it will be driving the tweeter is either one known to be better at treble reproduction?

On to driver choices...

For the tweeter I was thinking about the Peerless 810921. Seems decent value for money and I'm hoping will give me what I need.

For the midbass I am looking at the Scanspeak 18W/4531G 7" Revelator 4 ohm. This driver is expensive but I have read very good things about it and I'm willing to invest the money.


The cabinet then is the next barrier. The speakers might well be placed close to walls so a front ported design is preferable.
I will probably try to use a design I can find. I'll do some more investigation, but I'd appreciate some help with the kind of size of cabinet I might need.

Many thanks in advance, this is a big project for me so all input is very much appreciated.
 
Here is a nice design that uses your prefered mid/bass driver:

http://www.humblehomemadehifi.com/Optimo.html

There is an option to use the Vifa XT25TG30 (much cheaper) with only a small change to the crossover if you decide to go passive at some stage.

http://cgi.ebay.co.uk/2-Vifa-Peerle...oryZ3276QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I know that this is a floorstander, but it does not take up any more space than a standmount, and it is arguably less "messy" looking. The transmission line will get the best low end out of the Scanspeak driver and the "port" faces upwards,
making placement flexible.
 
Unfortunately you won't find too much in the way of active XO designs. Those of us who prefer an active crossover are a distinct minority. ;)

Your chosen XO is pretty basic - although its sound quality is decent, It is better suited to main-sub crossover duty. Without the ability to add EQ, delays or baffle step compensation you're limited to the basic textbook matched slopes.

Not that it cannot work if your drivers have plenty of overlap, but chances areit will be less than optimum. If you can afford the DCX2496 you'll be able to get better results with the flexibility it offers. There is also a group buy brewing for active crossover boards, but t probably won't be completed in time for your break.

My preference would be an LM3886 for the tweeters. I haven't heard the T amp, but I'd like the extra headroom that the LM3886 would offer. It's not that much more expensive.
 
AFAIK ( which is not very) the only problem with using an active xover like the Behringer CX2310 (which I use for my surround speakers) is that they don’t’ invite response tweaking. Dedicated Xovers usually incorporate corrections to match the drivers and tweak the overall response. For my mains I use the dbx xover with RTA that accomplishes that for you. (Behringer also makes an excellent one) IMIO* muti-amping and active xovers are definitely the way to go.

IMIO = In my ignorant opinion.
 

valleyman

Member
2008-02-07 7:21 pm
Many thanks for the input. Unfortunately I really can't accomodate floorstanders, but I could probably live with tallish standmounts. The problem is, being a student, I move about a bit, changing rooms etc and floorstanders are simply too impractical for this.

With regards to the crossover... The DCX2496 is only £140. Admittedly that's quite a bit more, but not excessive in the grand scheme so I will definitely give it proper consideration.

From what I can tell, this is also a 3-way XO. The question then is should I go 3-way instead. This would certainly help with the integration, and with a 3 way system I could set the lower XO point in the middle of the baffle step and simply give the woofer a little extra power. This seems to me quite an elegant way of dealing with the necessary correction.

If I were to choose a 3 way design I would need to choose some cheaper drivers. I have never bought a driver before, but I feel fairly sure that, for instance, a SEAS driver coming in below $100 isnt really going to be that much worse than the Scanspeak costing more than twice that.

So for a 3-way I could go with:
Peerless 810921
MCA12RC (H1304) 4.5" Coated Paper Midrange
For the woofer I would then be looking at the CA18RNX or the P18RNX/P. I think this is just the coated paper/poly versions of the same driver.
The paper version has a more similar Fs to the original scanspeak while the poly cone is higher.

I would then need a couple of T-amps or LM3886s or maybe one of each, and stick to using my HK as a pre and power for the woofer.

That optimo cabinet design looks good, despite the fact I cannot accomodate it. I'll quickly sketch a version I could accomodate in a moment and post it for criticism.

Once again, thanks very much, I really want to do this project and I won't be able to without help. I'm not expectine anyone to design this for me, but these kinds of comments are just what I need.
 
The great thing about active crossovers is that you can easily change your set up without wasting money on expensive crossover components.

If you buy a good mid/woofer like the Scanspeak and build a bookshelf/standmount then you can add a bass driver at a later date and build a three-way floorstander. I think three-way standmount will be hard to achieve and may limit future potential.

Do not be put off good compact speakers. They can go deep and sound every bit as good as larger units.

You should also consider the 15W4531 driver too, along with its sisters, 15W/8530 etc. It may be more suitable in the long run.

http://www.troelsgravesen.dk/Ellam.htm
http://www.troelsgravesen.dk/W1501_95.htm
http://www.zaphaudio.com/ZD5.html
http://www.lautsprechershop.de/english/index_hifi.htm See "Studio 12" under "Scan Speak kits"

The 18W4531 is also used in AOS Studio 22M in the german section here http://www.aos-lautsprecher.de/index.html

The Delta 3 project here http://www.gattiweb.com/index.html demonstrates how you can "grow" from two-way to three-way, by adding the bass driver section at a later date when you have more space and funds available.

I would aslo recommend going for the DCX2496. It is much more capable and will be able to serve your needs for many projects in future years.
 

valleyman

Member
2008-02-07 7:21 pm
So Here's the picture I've come up with and a scribble to the side showing the possible eventual arrangement.
Sorry about the crummy photo - finished the sketch, put it in my scanner and a nice little message popped up declaring the scanner is dead...


Also dublin I think I may well go for those tweeters you recommend too, thanks.
 

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valleyman

Member
2008-02-07 7:21 pm
OK. You're definitely right, the DCX2496 is a better idea. I'm fairly sure it has a sub out too, so I can add a sub later if I like in addition to the 3 drivers.

Is there any obvious reason the design I posted above would not work? Is it a problem to have the tweeter so low and might I be better going for WTM?
Also any thoughts on maybe a 3 driver copy of the ZD5?
 

valleyman

Member
2008-02-07 7:21 pm
This was supposed to be an adaptation of the Optimo's TL design, but a little reading and it goes in the bin I think. In a standmount design like this, the TL isn't long enough to give me the bass extension a TL is supposed to offer and is therefore not really suitable.

I won't scrap the TL idea altogether, but I think I need to sit down, do some reading and think on it.
I'll have some time tomorrow evening to rethink and redesign
 
I would bin the TL idea if you are going for a stand mount, unless you are using a much smaller mid/bass driver.

I would also bin the 3 way idea, as this is hard to achieve in a compact enclosure. It would mean that the drivers would not be suitable for incorporation into a larger pair of cabinets at a later date (if this is your intention).

I still think, given your physical restraints, that a small two way would suit you better. If you go with good quality drivers like the ones you have mentioned, then at a future date you could add something like a Scanspeak 26w8861, adjust the active XO accordingly, and you would have a hard to beat three-way system. See Delta 3 project mentioned previously. You can build all sorts of enclosures, and do not have to be stuck with any particular design.

Do not think that a small two-way system cannot give amazing results. Look at the Scan Speak kit, Studio 12 reviews on the http://www.lautsprechershop.de/english/index_hifi.htm website. Also google serch for reviews on the Acoustic Energy AE1.

If you really fancy something more "special looking" then consider a MTM d'appolito speaker. This is still a two-way (the two identical mid/bass drivers act as one) and will give great results, whilst being able to be made into a three way at a later date. See the Maxima at the bottom of the page : http://www.audiocomponents.nl/speakers/scanspeak/reference/scanspeak-reference_eng.htm

There are lots of designs out there for small/medium sized d'appolito speakers.

Have fun.
 

valleyman

Member
2008-02-07 7:21 pm
Thanks dublin. I agree, your advice is sound. DIY auido is something I think I could get into, but not at present. A few years down the line when I'm not working on a student budget I'll probably come back to it, but for now I want to build something decent but also fun and unique to me.

A 3-way standmount TL would certainly be that BUT big driver = large cross section of TL and it needs to be pretty long so you are right, fitting that in a standmount is a losing battle. On the other hand they can be fairly big, they just can't go on the floor.
I'm very busy this afternoon but have time this eve. Will absorb your words of wisdom, think on it and come back with alternatives.
Thanks
 
Hi,

I'd build a high quality passive 2-way.
On a budget active does not make much sense for a 2-way.

but for now I want to build something decent but also fun and unique to me.

Unique usually translates as ignoring the sensible options ......

http://www.zaphaudio.com/SR71.html

The drivers are available in the UK. The boxes can be made larger,
around 18L / 0.75 cuft and tuned a little lower for better quality bass.

More expensive drivers ?

http://www.geocities.com/woove99/Spkrbldg/Usher_2way/Usher_2way.htm

All metal drivers ?

http://www.zaphaudio.com/audio-speaker17.html

Again drivers available in the UK.

I'd would use one of the above and then concentrate on the quality
of the cabinets. 9mm MDF / 12mm chipboard joined with a contrained
layer for damping and some bracing might an idea, but there are
other options / approaches that could also work well.

Also any thoughts on maybe a 3 driver copy of the ZD5?

There is adding a powered subwoofer or two to it. There is not
such a thing as an effective 3 driver version without redesign.

:)/sreten.
 

valleyman

Member
2008-02-07 7:21 pm
I'm probably going to end up buying drivers from madisound. It's 2$ to the £ at the moment near enough so even with duties and shipping etc it probably still works out cheaper and then I don't have to worry about which drivers I can get here.

I've come up with a design new design I feel would work fairly well.
It is based around a 15cm instead of the 18cm woofer and I've ditched the mid driver as dublin suggested and I'd probably be looking at one of the ScanSpeak 15W woofers.
I'm most attracted to the 15W/4531G. This driver has a 40hz Fs compared to others which are around 30hz which (correct me if I'm wrong) allows for a shorter TL.

In this case I have roughly a 150cm tapered line with an initial cross section of 144.5cm^2 and a port size of 93.5cm^2 - almost identical to the driver area.
I'd be looking at using a fair amount of stuffing especially in the first 2 parts of the line and I could adjust tuning with stuffing in the last section.

I've learned an awful lot in the last few days and hopefully it's made the required difference. This design seems very workable to me and I quite like the fact that I have a bit of "in-built" tilt in the front panel too.
When I said I'm on a budget, what I meant was I don't have the money available to start doing this as a hobby at the moment. For this single project, however, I have a fair bit of money saved and I'd be willing to invest around £500 with more available if I think it's worth it - but yes, you're right, 2-way makes more sense for this price.
Thanks all who have replied!
 

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This is starting to look pretty good.

I am no expert on TL design, so I cannot comment on the tuning. I have read a White Paper on TL design. If you ask on this forum someone will point you in the right direction. Or you may find it here: http://www.t-linespeakers.org/index.html

Madisound are good. I have had drivers delivered to the UK very simply. It is not just the exchange rate (which is good for UK residents at the moment), the prices of goods are so much cheaper in the States as a rule - even when the items are European in origin. I am sure that you are aware oif "Rip off Britain".

I have used 15W/4531G. Very nice indeed. I am about to buy two more.

When I said I'm on a budget, what I meant was I don't have the money available to start doing this as a hobby at the moment

This is how ninety percent of us started (not with the intention of starting a hobby). Beware it is addictive. If you enjoy building and creating things that are interesting and special then DIY audio can have great appeal (assuming you enjoy music). You don't have to have lots of cash either. There are plenty of budget designs out there too - not that yours is a budget project.
 
Yeah, I'm not sure that tool is any good. I think much more effective designs can be produced using the alignment tables produced by Martin J King.
To that end I have come up with a revised design which ought to work better at least in theory. I'll do a quick sketch later, along with some explanation as to how I arrived at the figures it uses.
Thanks