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Old 4th May 2007, 01:20 AM   #1
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Default DIY dilemma, TMM, MTM or TMW

My problem / requirements.

I am concerned my system is lacking bass / low midrange (ie. 80Hz - 320Hz) and also want to replace my main speakers with something better.

My room is - 5m x 7m (or 16.5' x 23') with cathedral ceilings.

I know a TM based on a single 6.5" woofer will hit excursion and not drive bass to satisfying levels in my room. Even with more BSC, the TM will not be able to fill the room without stressing the speakers = distortion / risk of damage.

I've added a sub - but I find I need to playing higher than 100Hz to fill in the gap mentioned above, meaning localisation / messing with the imaging / midrange.

I want to avoid active crossovers - only because I perceive my electronics knowledge is sub-par and the cost of extra passive crossover components would be cheaper than investing in a proper active setup, manuals, training etc.... I have enough amplication so "wasted power" going through a passive (high level) crossover isn't a concern. Active might be a step away in my DIY learning.

Solutions:?

1. Go MTM (2 way) or TMM 2.5 way, crossed at 100Hz to the sub. Would this address the above issue? At least I'd get more efficiency, problem is the midbasses would still be mixing bass and midrange.

2. go TMW running full range - with a side firing woofer crossed at 100Hz and to a sub crossed at say 40Hz (or matching the woofer rolloff). Thinking of a 10" woofer in the TMW. 100Hz is to avoid localisation issues (however with one per side - could I crossover higher? Tried searching the forums and generally people recommend 100Hz and below for side firing). Side-firing is to keep a slim asthetic baffle. Thinking of using a 6.5" mid/bass as I'll need it to handle down to 100Hz. The reason for a 10" driver is I can't see an 8" having enough swept area for satisfying bass at higher levels (or the 8" being driven harder to match a 10" = distortion)

Any other options?

I haven't put cost constraints into this. If I had to put a parts $ cap on this I'm thinking USD$700 (drivers and crossover components) - as I will have a USD$250+ shipping bill on top of that.

Thanks,
David.

PS: should have added:
I will be able to measure - so utilising an existing design is fine but not afraid to do a new design
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Old 4th May 2007, 04:16 AM   #2
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I'd still definitely try to go for an active setup, at least for the woofers. Passive inductors and caps would have to be huge for the frequencies you're looking at filtering active would probably be cheaper all round, apart from needing extra amplifier channels.
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Old 4th May 2007, 04:32 AM   #3
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And the three way would get my vote every time, except getting the integration between the bass and mid unit could be a problem, by this I am talking about level in dB matching, not necessarily the slopes in the xover. Actively driven however and this problem is erased.

Active crossovers are a doddle to make, no really they are. All you need is an extra power amplifier. You can veroboard the circuits to good effect, which massively simplifies construction.
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Old 4th May 2007, 05:11 AM   #4
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A 10" + 6.5" + 1" would still give you the same issues that 2-way designs tend to have: a crossover frequency around 2~3kHz and a midbass dip somewhere in the vicinity of 300Hz due to the baffle step of a slimline enclosure.

What I'd consider is an old-school WMT design with a 10" woofer running quite high, say 300Hz. A smaller 4" midrange going up to 4~5kHz, and a tweeter doing the rest. However, a side-firing 10" woofer might not sound so good at 300Hz. Others have come up with tapered designs so the top is slim despite having a front-firing woofer, or maybe a use a split box design?
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Old 4th May 2007, 05:25 AM   #5
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I think you would get the best sound from a TMW with a forward facing woofer in a separate cabinet for vibration isolation.

There are two schools of thought:

1) equal power with crossovers around 300Hz and 3K Hz, typically 1" dome, 5" midrange and either two 10" or one 12"-15" woofer. B&W Nautilus is one example.

2) human voice all on midrange with crossovers around 100Hz and 1.3Khz, typically low Fs 1" dome, 7-8" midrange, and 12-15" woofer.
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Old 4th May 2007, 08:50 AM   #6
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Thanks for all the good the advice.

Ok - it seems I should really be a man and have a look at active crossovers. After all, I'm about to make a Wallin Jig so they can't be that hard I'll google and see what I can find.

I think the side firing woofer will be more trouble than it's worth. The tapered (pyramid) type shape could be quite asthetic. Although I have a very tolerant and supportive partner, I respect she wants to live in a nice place with nice furnishings.

Would you go active all the way (TMW) or just on the woofer? (shows how much I don't know about active).

I want to buy drivers soon while our USD exchange rate is good (and save some money).

Thanks,
David.
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Old 4th May 2007, 11:44 AM   #7
Zarathu is offline Zarathu  United States
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Go here:

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You can learn everything you need to know. I did

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Old 4th May 2007, 02:07 PM   #8
tinitus is offline tinitus  Europe
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I would go even further and suggest a 15-18" with a good full/widerange with a supertweeter of some kind
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Old 4th May 2007, 07:45 PM   #9
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Quote:
Originally posted by LineSource
I think you would get the best sound from a TMW with a forward facing woofer in a separate cabinet for vibration isolation.

There are two schools of thought:

1) equal power with crossovers around 300Hz and 3K Hz, typically 1" dome, 5" midrange and either two 10" or one 12"-15" woofer. B&W Nautilus is one example.

2) human voice all on midrange with crossovers around 100Hz and 1.3Khz, typically low Fs 1" dome, 7-8" midrange, and 12-15" woofer.
If actively driven across the bass to mid crossover then the number of bass units matters not, usually they are chosen in quantity to match sensitivity.

I have tried both thinking 1) and 2) there are pros and cons to each.

The good thing about number two is the low crossover on the mid is low enough so that the bass drive unit is effectively acting as 'sub' more or less. This means getting a good match between bass and midrange is far less critical, as the fundamental and the majority of the harmonics are being played by the same driver (midrange), giving consistent tonal balance. The negative side is that the xover from mid to tweeter is fairly low. If you want to maintain good off-axis response this will usually place the xover in the 1-3khz critical range.

Version 1 has the benefit of allowing you to use smaller midrange drive units with far better extension and dispersion on the top end, allowing a crossover between 4-5khz or so, moving the upper xover away from that sensitive band. The downside to this, is that the midrange cannot be crossed over as low and therefore you are calling upon the bass driver to reproduce a lot of the fundamentals. If crossed at say 400hz you're getting 90% of a tenors fundamental range covered by the bass driver and the harmonics on the midrange. Just under half a sopranos fundamental on the bass and the rest of her on the midrange + harmonics. Obviously this requires good matching. You will see Shin, trying to match an ATC mid dome with a SEAS excel W22 with mediocre success, something didnt sound right - Metal cone matching with a soft dome, it didn't work particularly well. Note that this is slight nit picking over a grain of sand, the combination of the W22 and ATC would, I have no doubt, sounded great, but using a bass unit with a damped cone, instead of the metal SEAS, got the balance just right.

Crossing over higher up (ie 4-5khz) to my ears, does sound better, but will require a better match (and possibly a more capable bass driver) between bass and mid. With a 100hz cross the 'quality' of the bass units midrange is far less critical.

The problem, as mentioned before, is getting a MIDRANGE driver thats comfortable playing low as well as high, pure mids are not so happy with this. They can have nice upper extension, but the lower end suffers somewhat. The easy answer is, use a mid/bass. A quality 4-5" mid/bass will be plenty happy playing down to 100hz and, if chosen correctly should be happy going up to 3khz. A pure mid would probably sound better, if the surrounding components are up to the task, but this could get more expensive. A good compromise would be a mid/bass for the mids. This would mean you can cross low, and remove a bit of a headache with bass to mid matching, but also allows a reasonably high cross on the mid to tweeter crossover.

With the pure mid you can cross high and use any good but inexpensive tweeter on the market, however require a better bass unit perhaps. With the larger pure mid, you can cross lower to the bass, requiring a less capable bass drive unit, but now you need a tweeter that can handle the low xover point = generally more cash.

Using the mid/bass for the midrange, you can cross low to the bass and high to the tweeter, best of both worlds, but probably with a slight compromise in quality. The main problem is getting a small driver to play low, a large driver, by its nature cannot really play high and maintain good off axis performance.

Quote:
Originally posted by Dave Bullet
Thanks for all the good the advice.

Ok - it seems I should really be a man and have a look at active crossovers. After all, I'm about to make a Wallin Jig so they can't be that hard I'll google and see what I can find.

I think the side firing woofer will be more trouble than it's worth. The tapered (pyramid) type shape could be quite asthetic.

Would you go active all the way (TMW) or just on the woofer? (shows how much I don't know about active).

I want to buy drivers soon while our USD exchange rate is good (and save some money).

Thanks,
David.
Active all the way if possible yes, but the biggest advantage will come from the bass to mid xover being active.

Quote:
Originally posted by tinitus
I would go even further and suggest a 15-18" with a good full/widerange with a supertweeter of some kind
Quote:
Although I have a very tolerant and supportive partner, I respect she wants to live in a nice place with nice furnishings.
I think 15 and 18" drivers are not an option Perhaps one in a corner (out of the way) as a sub maybe.

A three way with a 10" bass, 4-5" mid/bass and 19/25mm tweeter would work very well.

A peerless - 830668 on the bass
A peerless - 831882 on the mid
A vifa - XT19 on the highs.

Xover ~100hz ~3.5khz Should work great imo. Of course there are many other drivers to choose from also.
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Old 5th May 2007, 07:39 AM   #10
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Thanks for the detailed reply 5th element.

The 10" / 5.25" / 1" combination sounded good to me too. Looking at Zaph's site - not many of his 5.25" drivers he recommends over a 2KHz crossover (mainly due to higher order harmonic distortion lower down the range).

I'll do some enclosure modeling for 5.25" that are happy down to 100Hz to ensure xmax won't be a problem (shouldn't be).

I've been thinking of going all seas - L26 for the 10", either the L18 or L15 for the midrange (I know the L18 is a 7" midbass), with a 27TBFCG 1" tweeter. Even if I decide to xo mid/tweeter at about 2KHz - then the 27TBFCG should be able to handle it with 4th order acoustic slopes based on others' designs.

If the L15 won't model down to 100HZ, then I'll play the L26 upto 200Hz. At least being the same range and cone materials, harmonics and timber should be better matched than if using different cone materials.

I'm going to go sealed for both woofer and midrange. Easier to get right. No need for a mid/woofer to be run vented. I'll just supply it with a larger \(Qtc0.5) enclosure well stuffed / damped to absorb as much backwave as possible.

I've started reading the pages suggested by Zarathu. At least now I'll order the drivers which are the bulk of the cost before worrying about either going the passive or active way to protect against fluctuating currency.

Cheers,
David.
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