Redesign my TMW to a TMMW with Shiva's

[sunil]

Please comment on the following setup. I plan to redesign my TMW to a TMMW for higher sensitivity. The W is a Shiva which will be in a cabinet as part of the entire speaker, front-firing. The TMM will be in its own cabinet on top. The whole setup is 4-way active. The crossover frrequencies are at 2500 & 200.

The drivers are:

Tweeter : Vifa D27
Mid : Vifa P13
Woofer : Shiva

My doubts are:

1) Whether I can get away without padding the TMM since the sensitivity will be much higher than the Shiva's. Since some gain is expected, will room gain make up for the 88db sensitivity of the Shiva's ? The Shiva cabinet will have a Qtc around 0.6 for accurate bass ( primarily music ).

2) In a TMM is driver offset an issue ?

cheers,
sunil

[pat_staunton]

Hi Sunil,
Your project sounds quite interesting,
Could you give me some more details on your Xover? You said it was a four way right?
And where did you pick up the Shiva driver? in Bangalore?
Any idea whre to pick up some good drivers in B'Lore?

[sunil]

Hi Pat ( hope that is is your real name ),

The x-over design is what is available from Rod Elliot / Dave Pomann. Nothing fancy. Although when the current 2-way materialises to the 4-way I will use the design as published by Luc Henderieckx's. The drivers are all from favours by friends.

In Bangalore the ONLY option I know for good drivers are from www.corrson.com. Nice people to deal with though. They have very good accessories including a "tar" based damping material.

Cheers,
sunil

[pat_staunton]

Thanx a Ton...... No, Two tons.......
Sunil my man you saved me a lot of trouble.....
Do let me know how things are going with your project...

Pat.

[BillFitzmaurice]

I'd go MTMW; you'll get much better horizontal dispersion and lessened early reflections. Driver offset isn't a particular problem, your time align differential is far too short to be audible. The differing sensitivity situation isn't a problem either; remember that the mids are rated at 88 dB in a standard baffle, but normally your're not going to get that in a narrow box due to the diffraction step, so the additional 6dB of voltage sensitivity merely balances out the baffle step anyway.

I'd also reconsider the 200 Hz crossover; your post isn't specific but if those mids are P13WH-00-08 midwoofers they should be used for the directional frequencies, right down to 100 Hz or so, for the best result.

[sunil]

Bill,

Thanx for the reply. Before I go ahead I should mention I made a mistake with the original post. I had intended to write, the setup is a 3-way active, not 4-way. I don't understand something.

Is'nt the P13 weak at below 200hz ? Why not x/o at 200hz ? I'm going by the spec sheets as I have not measured the drivers. The Shiva's are to be on the same plane as the P13's & the D27's, so are the directional frequencies still going to be a problem ?

Thanx,
sunil

[navin]

many years ago I heard a pair of P13s and asked the owner/designer what was wrong. he said that the P13's are not dyunamic as they have a high damping surround. they are very flat in their freq. resp. though. then we heard a scanspeak that had a low damping surround and while the paper freq. resp specs were not as flat as the P13s the sound was closer to live music. given this experience i think that your orignal XO of 200Hz is not bad. Yes the P13 s can go quite low but when you ahve dedicated woofers for the bottom octave or 2 why not use it. I suggest email Lynn Olson. He has a lot of experience with the P13s.

[BillFitzmaurice]

As fasr as the midwoofs/tweeter are concerned they are the focus point of the system directionally speaking, and you don't want that focus disturbed by another source, which the woofer could be if crossed over that high. With a single P13 you would have some issues going down to 100 Hz, but with two it shouldn't be problematic. But it's a rather moot point if you're going active, since adjusting the crossover frequency will be a matter of turning a knob anyway, and you can alter it to whatever sounds best in room.

When you say the Shiva will be on the same plane as the other drivers I assume that you mean vertically speaking.

[sunil]

Hi Navin,

I remember you mentioned the same thing in some other thread. I decided on the dual P13's after reading about the success people have had with the Ariel's.

Bill,

Does that mean, with a dual setup I can push them to 100hz without any equalization of any sort ???? I checked it with "Unibox" & two P13's just about manage at 100hz. What do you think ? Is there something I'm missing here ?

If not 100hz, is 120 a more appropriate x/o frequency ?

Thanx,
sunil

[BillFitzmaurice]

It depends on your alignment. 2 drivers maximally flat in a .2 cu ft sealed box gives an F3 at about 140 Hz; in a .4 cu ft VB the F3 comes in at 80 Hz. If it was me I'd be going the VB route, so that if you find in room that a 100 Hz crossover sounds better you can do so without stressing the drivers. For that matter you may even decide that 80 Hz is better still, but with the sealed box you'd never know since it wouldn't give you that option. I know that sealed is often preferred for midbasses, but the main reason for the bad rap that vented gets is insufficient damping of the box.

On the other hand if you really want a killer rig go TL instead, that way you could go to 80 Hz no problem at all and still have the sonic characteristics of a sealed box.