recommended shielded 2-way speaker designs?

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I know these types of questions get asked quite often, but I'm having trouble sorting through the million or so 2-way speaker designs so please bear with me. I am going to build a pair of speakers and an appropriate GC to drive them over my winter break. I originally planned to build a 3-way set, but I think I'll take Bob Ellis' advice and stick to something simpler for my first major project. I'd like to keep the total cost (including 2-channel GC) around $600. The main design considerations are:

shielded- the speakers will be sitting pretty close to my roommate's TV, and I'd like to avoid any possibility of damaging it.

decent low-end- I will eventually build a subwoofer to go along with the pair, but I'd like to build something that sounds good by itself. I listen to a lot of electronic and classical music, and I realize i can't get floor shaking bass out of a 2-way, but a nice low-end 'presence' would be quite enjoyable. Accuracy is key. If it's not possible to get decent low-end out of 2-way then I will look at 3-way designs although I'm assuming that it should be possible with a 6'' or greater woofer.

I'm going to use the speakers mostly to listen to music. My roomie owns a pretty nice 5.1 system (Polk) we are using for HT. I'm building these more for the experience and to have something i can start building my own audio system around.

Incidentally I've also looked at line-arrays, and ruled those out based on material costs and size. Open baffle designs sound very attractive, but I have very little control over speaker placement (which i hear is fairly important if they are to sound good) and I've read they are more complicated to amp since they sound better if you can vary the cross-over frequencies depending on room acoustics and the such. I'm not sure that I understood that correctly, but it seems like most people who like the sound of OB speakers are using them with more complicated audio setups than a simple CD-player hooked to a 2-channel amp and passive XOs. If I am completely wrong about OBs let me know, I'd consider building one if it weren't for the above reasons.

If you are still reading at this point I may as well go on... I'd like to the speakers to be able to handle a decent amount of power. I already have a pair of small studio monitors (NHT M-00s) and I'd like to build something that can fill a larger room than those. Perhaps that is not related to power handling, but I've read that less efficient speakers tend to sound a little better than the ones with very high db/w ratios (is this correct, or am I wrong?)

I am trying to create something that sounds good. I know that's very relative, but I'd like to keep the quality at least on par with the NHTs (although I happen to think the NHTs are a tad too bright). If that means I absolutely must spend a little more money, then so be it- let me know if I've set my budget too low. Also, does substituting a shielded driver (with similar specs) change the response of the speaker considerable, or is that a pretty flexible design issue?

I guess I should mention some of the designs I've looked at. Any comments regarding them would be helpful:

Audax Mini's (not shielded and perhaps a little smaller than I had in mind)

Wesnor's Cameo

there are others, but it seems i forgot to bookmark them :( I've probably left out some stuff, but I think I've tortured everyone with enough reading for now :angel:
 
I noticed the 18S-8535 (partsexpress link here) has a sensitivity of 86.5 dB. Will I have trouble driving such a beast with a GC? I've read the power handling capabilty of the 2.5 clone is 70W rms with 100W peak, but I'm not sure how conservative of an estimate that is since the Proac site rates it at 200W peak. How powerful of an amp would you recommend I build?

-tony
 
On a different track - are you looking for "bookshelf" speakers only, or is a floorstanding option acceptable?

Though I think it has other inherent problems (drivers aren't shielded) but something like Wayne J's Eros would make you a very happy camper. And I *think* it falls in your budget. :) Some price changes since the price/parts list was posted. I'm not sure I would worry about shielded driver use and just focus on sound. Unless these will be RIGHT next to the TV you'll most likley have no issues at all. Just a couple feet between TV and speakers is usually more than enough. And it'll sound a LOT better that way.

Other options abound.

FWIW, "similar" driver that's shielded doesn't work - only "same" driver, and even then sometimes response changes such that they're not a direct swap. YMMV.

C
 
I built some Dennis Murphy MB20's. They sound great with a gainclone and have amazing bass for a speaker that size, IMO obviously. These are definitely on the warm side but still have good detail.

Parts cost me about $200. I used the shielded version of the M-130 woofer and the Morel MDT22, the shielded version of the MDT20.

Dennis' site has many variations of speakers built on the GR Research M130 woofer as well as other woofers.

As far as efficiency, I have some Ellis 1801s which are rated about 84dB and the gainclones with a 25-0-25 transformer ran them with no problem but I guess it depends on how loud you want them.
 
bookshelf speakers would be preferrable, but it seems that it's easier to get low-end response out of floorstanding designs (bigger cabinet). I'm pretty flexible...they just can't be *too big.

There is a shielded version of the P17WJ 6 1/2 drivers found in the Eros design. The frequency response graphs don't match up exactly, but they are very very close. Parts Express has them here.
 
Too bad it's the P18's used in the Eros... ;) It's also not just frequency response you need to watch - impedance can make a big difference. Even slight efficiency differences. Though if it's the same driver, both are likely to be close enough for all intents and purposes.

if you find it a problem, you could add bucking magnets yourself...

Are you intending on placing these closer than a couple feet from the TV? I ran my old Lafayette 2002's (single 12", small horn mid, pair of cone tweeters) only a couple feet away from a TV for years, and never an issue with the TV.

If you *are* placing these really close, you may not realize the sound quality of some of the better designs since reflections and such can alter the sound, sometimes (seemingly) drastically.

Depending on your timeline, other top notch options may become available. Parts Express just released their new Dayton RS series drivers which offer excellent performance at an almost too good to believe price, and they're fully shielded. I'll be building an MTM shortly (with a Seas tweeter) for CC duty as a gift. ~$150 with shipping, enclosure, finishing, and all that, at an absolute top.

Adire Audio also may be making some interesting offerings in the near future that could alter the landscape.

I might also add - if you've never built speakers before, there may be some sense in putting together a relative budget system. Once again, some of the Dayton speakers (this time in their Classic series) may prove a great option - something like a Triune in a TL enclosure (also can be ported or sealed) which runs a bit over $100 for a pair (plus enclosure). Particularly with roomates. ;)

Regardless, I'm just tossing ideas and thoughts out there. It's ultimately up to you.

C
 
Too bad it's the P18's used in the Eros...
Right, I must have missed that some how. Unfortunately, no shielded version of the P18 as far as I can tell...

Unless these will be RIGHT next to the TV you'll most likley have no issues at all. Just a couple feet between TV and speakers is usually more than enough. And it'll sound a LOT better that way.
Our floor space in the living room is really limited, so for the next year it would be sitting quite close to the TV and the speakers would be a little over a medium sized TV stand's width apart. I realize these are sub-optimal conditions, but they are temporary. I'm building these more for the experience and to do something creative and useful with my winter break. I intend to use them as my main audio setup after I move out so I'd like for them to be nice.

Will magnetically shielded drivers sound worse? To be precise, the speakers will be positioned such that the drivers will be barely over 12'' from the edge of the TV screen. Is this out of range of the emag interference?

Also, there is no reason why the TV needs to be on while I am listening to the speakers. My roomie already has a 5.1 system for HT and I'm building these purely for music (after I move out I will be using them for HT as well, but presumably I will have more floor space and will be able to put them wherever I want). If I can prevent permanent TV damage by making sure the TV is always off when I'm running my speakers then I'll look at non-shielded options as well.
 
Scone

If the shielded version of the same driver (18s8535) sounds different to the unshielded version, it would be the first time that I would hear about it. I find in my living room with minimal space that it is easier to place slim floorstanding speakers than bookshelfs on stands. You cannot prevent damage to your TV monitor by turning them off. The damage could take place irrespective of whether your TV is switched on or off. The Proac 2.5 clone is an easy speaker to drive because of the easy impedancec load presented to the amp. I am positive that a GC would drive them to very loud levels. You would be hard pressed to find a speaker with better bass than the clones. If positioning is a problem, I would build them with a sealed box and port them only once I have the space to position them further away from walls. The driver can be used successfully in either sealed or ported boxes. I know that the drivers are expensive and over your budget, but it would be worth it for the sound. They are ideal for the novice builder because there is so much info on the available net.

D
 
I own a pair of ProAc clones ad surprised that no-one has mentioned room size.

I have towed these 55lbs (ea) speakers to my partner's apartment but they didn't suit the room at all. In a smaller place the speakers just seem to dominate the room, both visually and sonically.

You don't throw a band into any ol' venue do you?

And all good speakers deserve proper placement to suit the room and the listener's seated position(s). And if you build speakers rear ported, IMHO they sound best away from the wall. In my 20'x30' room they sound best at least 2' away from the rear wall, 7' apart.

If you have a smaller room and not much space a pair of bookshelves would be a good start, easier to build, allow flexible positioning.

And you won't slip a vertebral disc if you need to move house.

Since you have an active 2 way with 4.5" miniwoofer, I think one of the handful of 2 way standmounts 5-7" mid/woofers would be a nice start. John Krutke's
XG18/27TDFC MTM is a large standmount. If you can wait awhile his smaller L18/27TBCG should be also great value.

Troels Gravesen has a great treasure trove of designs of all sizes.

IME unless you need to put the speakers directly on top (eg. centre speaker) or within inches of the tv, non-shielded speakers are fine.

Any of these are sure to blow the socks off that NHT M-00
 
thanks for all the suggestions everyone. :)

Since you have an active 2 way with 4.5" miniwoofer, I think one of the handful of 2 way standmounts 5-7" mid/woofers would be a nice start. John Krutke's XG18/27TDFC MTM is a large standmount.

Sounds like a very inviting option. I'd have to place them on shelves about 5 ft. high and 6.5-7 ft. apart. I could angle them slightly down and inward. This is so they clear my roomie's floorstanding speakers and also to stay away from the TV. They would be very close to the wall but such is life (and they're not rear-ported so it's not as bad of a problem). Unfortunately there's not as much info on Krutke's MTM as there is on the Proac clones (actually, I can't find a single account of someone having built them, other than John himself)

I noticed that the woofer in the Proac 2.5 clone is shielded but the tweeter is not. Can unshielded tweeters damage CRTs as well? I'd have to assume yes, but perhaps the magnetic field created by them is small enough that it isn't a problem?
 
The woofer in the original and clone ProAc are unshielded. ScanSpeak offers a shielded version of the same driver, and people who have substituted this driver have had good results. I recall someone has built a centre speaker by doing this...

The clones must be THE most popular diy speaker of all time. IMHO, this is because

a) very good website- informative and helpful, thanks to Al M.

b) ease of build and moderate cost- it's a straightforward 2 way box speaker.

c) thoroughly fine tuned by several key people, and backed up with measurements.

The fact that the commercial (using similar but customised drivers) retailed for some 2,700 GBP/USD4,500/AUD10,000 in circa 1996-2003, makes it very tempting to the prospective DIYer...

Oh, and did I mention it does sound rather good?

Some designers prefer to do their own thing, and I can understand that you are hesitant because there's not as much feedback.

But I wouldn't be surprised if they sound as good or better, or have other qualities lacking in the 2.5.

I have other projects pending for summer 04/05 (yes we're south of the Equator so it's building time!)
Tony Gee Humble Homemade Hi-Fi
John K's NaO
 
tktran said:
John Krutke's
XG18/27TDFC MTM is a large standmount. If you can wait awhile his smaller L18/27TBCG should be also great value.


Got to hear these yesterday.

Top notch stuff. They were one of the only speakers that stood up to one track we played with some very heavy and somewhat distorted bass, yet they handled just about everything else with the same finesse. Really a superb speaker.

I'm not sure they'd like being placed that close to a wall though. IIRC they have full baffle step built in, so they would tend to sound boomy near room boundaries.

C
 
I'm not sure they'd like being placed that close to a wall though. IIRC they have full baffle step built in, so they would tend to sound boomy near room boundaries.
Forgive my ignorance, but I don't know what it means to have a full baffle step built in.

There's nothing i can really do about the boominess. Even floorstanding speakers would have to be placed pretty close to the rear wall, and those would have to be sandwiched in between a TV and my roomate's speakers. At least the MTM would have breathing room on both sides because I can mount it on shelves. We live in a pretty small apartment, but college living conditions are temporary and my speakers should outlast them . :cool:
 
cjd,

do you mean the XG18/TDFC MTM or L18/27TBFCG?

Really I should stop looking I have too many project ideas...

I feel that 2 ways should be confined to bookshelves IMHO and smaller rooms.

If I'm going to the trouble of building large floorstanders all the time/effort and MDF/veneers deserve more drivers for cleaner bass/higher sensitivity (eg MMT or MTM), or dedicated mids and larger woofers for better midrange and lower bass eg. 3 way.

scone,
The "baffle step" is the rising acoustic response (SPL of increases with increasing frequencies) of a driver once it has been placed on baffle (the front panel of the speaker). Without baffle step compensation, (compensating for this rising response by designing the crossover to tilt the reponse back to flat) speakers initially sounding "detailed in the midrange" soon reveal themselves as too prominent in midrange/low treble and fatiguing. Very harsh on your ears. You can partly counteract it by placing the speakers closer/against front wall. This elevates the low end (room gain) thus effectively tilting up the low end.

Speakers with full BSC have a flatter frequency response. But now if you place them against a wall the boosted bass will make it sound very unnatural/boomy.

Some speakers provide partial BSC compensation facilitating closer to wall placement and midrange that doesn't rip your head off when you place it clear of walls.

I hope my simple explanation of BSC made sense. Hopefully others can point out my mistakes...
 
Ummm...

Yes? I heard both. I got to hear the L18/27TBFCG combo from two different spots - I seem to recall it had a little trouble on the really heavy bass track (and I mean, REALLY heavy... we're not talking bass shy speakers on ANY of these, but this track was just a killer) at our standard level. Speakers were set to ~88dB from the front center (~2m back) which was actually too loud for me - I was one seat over and ended up giving it up and moving around the room 'cause my ears started hurting.

The XG18/27TDFC combo was a little more to my liking - I'm not really sure why at this point. One of my thoughts is that I'm not a fan of metal dome tweeters. :) But I really liked the ribbon we heard, so who knows. Anyhow, I suspect just about any of John's projects would be a no-brainer.

C
 
Thanks for everyone that suported my suggestion for the 2.5 clones. As I said in my original post, building them as a closed box design to start off with will allow for easier placement in a small room, yet give you very tight and dynamic bass. Has anyone else tried this?

D
 
stuffing the port kills the bass (obvious) and makes the mid-range sound shut-in (not sure why)

One of the aims of the clones is to provide good full range sound from a compact floorstander.

The tradeoff is low sensitivity. The tweeter has plenty of sparkle, and some say the midrange could be better.

So if you do it sealed, or going to use them with subwoofers, you may as well go with another design.

my 0.02dB
 
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