DIY dilemma, TMM, MTM or TMW

[tinitus]

Well, we will have to look fore that design then

But MAYBE this is not far from your desires

http://www.troelsgravesen.dk/PMS-EXCEL.htm


This is not to take your guts, anyhow, this is how I look at it

 

[CeramicMan]

At the moment I don't have much space for new speakers, but I was thinking about doing a TMW design myself within the next year or so. Something along the lines of:

10" woofers in their own floor-standing boxes – the shape probably doesn't matter so much, as long as it's aesthetically pleasing.

4.5" ~ 5.5" midranges housed at the mouth of Nautilus-like backloaded horns, constructed from stacked layers of plywood (or something similar). The idea is that the back-wave gets funnelled into a lossy cavity after about 2m or so. I still need to think about it, but I suspect that such a design could be extremely effective at absorbing the back-wave.

Generic 25mm hard-domed tweeter from Accuton, Seas, Visaton, Alcone – one of those guys.

All active/digital filters, crossed at around: 200Hz and 4kHz. Class-T amps for the bass and mids; class A for the tweeters.

 

[rj45]

re: no TMW designs available?

Gotta search a liitle more!

Here's a couple of TMW with 8 inch woofs that should satisfy:

http://www.rjbaudio.com/AlpheusMkII/alpheusmkii.html
or
http://www.rjbaudio.com/Daedalus/daedalus.html

and one of the true DIY greats, Troels. Many great systems.

http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm

Dennis Murphy's MBOW1 has been built by many people.

http://murphyblaster.com/content.php?f=MBOW1_3-WAY.html


Happy building.

-Don

 

[Dave Bullet]

tinitus,

I agree with you. Newbies (like me) are either arrogant enough or just plain naive, that they think they can reach on their first design the best sounding speaker ever made

In my case, if I end up designing my own, it will be more for the fun of it. I also figure with the cost of driver shipping from the USA I can send 6 budget drivers for USD$280 or 6 better quality drivers for USD$280. Yup - the same price. So may as well go for $150 or so in better drivers and get some value for money in the shipping.

My main concern at the moment is picking drivers well matched to the task. I am less concerned about the crossover, as I believe with adequate measurement and enclosure design and analysis, I should be able to get close. I would never embark on a self design unless I could actually measure (so I'm not completely green). I personally think well matched driver choice, timbre, natural rolloff, sensitivity and what 2nd and 3rd harmonic distortion products exist in driver passbands are vital to understand.

rj45,

Thanks for the links. I had overlooked Dennis' site. The MBOW1 3 way looks tempting.

Troel also has good writeups and good designs.

Ceramic man,

I am thinking of exactly the same combo in terms of driver sizes. Most 3 DIY ways on the net seem to go for 8" bass drivers. The reason I am steering toward 10" drivers is I have heard 8" drivers from different systems in my lounge and their bass is not satisfying. I realise this could be due to a number of reasons - other than the driver simply can't sweep enough air to reproduce low frequency.

What I may want in bass may not be true reproduction. but it is what I like and gives me satisfaction and emotion listening to music.

I will complete my measurement setup soon - so will be able to tell if what I've been listening too is at least flat, or whether I am a basshead

Cheers,
David.

PS: I do like good live classical music too! But I also like organ rattling D'n'B

 

[tinitus]

OK, thats good then .... in that case I think you will need at least a good 12" or double 10" to get what you dream of .... I would

 

[critofur]

Why not build speakers which are accurate and neutral, then supplement them with a subwoofer that will give you however much bass you want? Then maybe 8" would be fine on the main speakers ~ take them down to about 45 - 50 Hz?

Then you can have very excellent accurate reproduction of some musics, but also reproduce an earthquake type of bass when listening to some club music (something like Chemical Bros., or Crystal Method type music?)?

If you use a subwoofer you can add a 2nd one, or switch to a bigger one, whatever, without changing the main speakers.

If you really want to go crazy with the base, then you might want a couple of high excursion 15 inch subwoofers?

Something like a pair of these: http://news.softpedia.com/news/Under-Heavy-Bass-Bombardment-49259.shtml might be good?

 

[tinitus]

First I will say I think this one from Troels looks real impressive, and although I am sure it will sound very good, it wont produce monster bass

http://www.troelsgravesen.dk/TJL3W.htm


To follow up on your urge/choise to build a classical 3way .......

I would build it with double 10", and a good widerange, and maybe a ribbon or the Hiquphon OW1 or the XT19

2 x Seas CA 26RE4X
Veravox 5X(S ?)
NEO-3/FP or similar

xo frequencies could be 500hz and 5000-10khz

 

[Dave Bullet]

Thanks for the replies.

I have definitely settled on a 3 way. Main reason is to offload the midrange drivers (in a TMM / MTM) from having to play bass frequencies (even though excursion is halved, it must be better if the driver plays no bass at all, forcing it to introduce harmonics at the lower end of its passband).

I already have a 12" sub which I will use for the bottom octave or so (ie. upto 60Hz). I'll use single 10" drivers in a TMW but in a sealed enclosure so there is a 2nd order rolloff (or thereabouts) and no driver unloading with heavy music.

Mi mid is not efficient enough to keep up with dual 10" (then there is also SAF which is TMW limited at this stage - well I don't want to push that constraint)!

I've got some raw simulations on the L26 / L15 / 27TBFCG with pretty close 2nd order acoustic LR slopes between mid and tweeter. Problem here is the XO is around 2.25KHz. I'm trying to avoid crossing the L15 above 2KHz due to higher order harmonics due to the cone breakup mode at around 8KHz. Another problem is 2nd order acoustic slopes don't give many components to play with getting phase right, which means either going asymetric (may help protect the tweeter), slanted baffle or ladder delay network.

I also plan to biwire the speakers to the top terminal will feed the TM and bottom the W, so biamping (or simply cutting off the 10" for light string classical) will mean the system can be used for night listening etc...

Thanks,
David.

 

[Dave Bullet]

Tinitus,

Wouldn't it be harder to get phase tracking right the higher you go in frequency? Maybe there is no difference whether the xo frequency is 500Hz or 5KHz. Just seems to me the higher the frequency, the more critical phase alignment becomes.

Cheers,
David.

 

[audiobomber]

Thanks for the replies.

I have definitely settled on a 3 way. Main reason is to offload the midrange drivers (in a TMM / MTM) from having to play bass frequencies (even though excursion is halved, it must be better if the driver plays no bass at all, forcing it to introduce harmonics at the lower end of its passband).

Yes, but you have to run the mids through a giant cap, and the woofer through a giant coil. It's a trade-off, there's no free lunch.

 

[Dave Bullet]

Yes, but you have to run the mids through a giant cap, and the woofer through a giant coil. It's a trade-off, there's no free lunch

True.... assuming the ear is less sensitive to any distortion introduced by crossover components on bass frequencies (after all Class D amps are used for subs)..... is there any evidence quantifying the distortion introduced by a large cap on the midrange?

With a passive 3 way - I'll end up having to buy a $20 something 60uF metalised polyprop cap so a lot of extra cost too. I am also hoping with some judicious shaping of sealed midrange Q I might be able to use the enclosure to shape the midrange lowpass without having to add a large parallel inductor as well (cost rather than quality issue here).

David.