Zaph's suggested Peerless 830656 & Seas DXT MMTMM design

[Loboone]

Good evening all,

I am hoping to start an investigation that will culminate into something myself and others will find of interest.

In one of Zaph's recent posts he describes the MMTMM senario using Peerless 830656 woofers and Seas DXT tweeter in a 2.5 way configuration. A sort of a poor mans "LGT" I guess.

Anyway not having any great software packages and the experience to completely design such a speaker (Yes Zaph cross overs and BSC etc etc scare the hell out of me).

Thats why my first speaker was Tony Gee's "Solo 206". But eventually I plucked up the courage to build Zaph's "ZBM4" bargain mini. It's a great little speaker but since I started using it for my PC sound the kids won't let me take them away and I am left wanting for speakers for my lonely Leach amp. (206's dont cut it sorry Tony)

Anyway in WinISD beta I have come up with two woofers in a 36 litre vented box and a tuning frequency of 45Hz. Box internal measurements of width 150mm height 600mm and depth 400mm.

There will be two of these boxes on top of each other and wedged in between will be the tweeter and hopefully space for the Xover. I believe these dimenssions come out somewhere close to Zaph's 50 inch mark.

Questions?

Am I better to stick with a straight baffle or design with angled woofers toward a listening position as in LGT.

My room has 8 foot ceilings so the bottom woofers will be closer to floor (carpeted). Should this be taken into account when designing cabinet or can we fix with Xover? Ceiling hard surface so maybe reflections will be even anyway? Distance and carpet doing the job anyway?

Anyway hopefully the guru's will be willing participants and some time down the track I and others will have something special in the lounge much to our partners delight!!! He He!!

Ian

[sreten]

According to Zaph : Qts = 0.51, Vas = 9.6L, Fs = 53Hz

http://www.zaphaudio.com/blog.html Nov 29 Vertical Polar Response

Hi,

Putting drivers in boxes where the box volume exceeds the drivers
Vas is not a good idea, basically for that volume there is usually a
better driver choice. 18L for a 9L Vas driver is not good practise.

18L vented is more typical for a 6.5" driver.

Qts = 0.51 usually means sealed, but is on the cusp of being ventable,
but this means a big box or a unusual more compact vented alignment.

WinISDbeta is OK for quick sims but you need something more
accurate like Unibox for simulating anything your going to build.

I'm not saying you cannot build these boxes, but they will be big.
72L a side in a tall (50") and slim (7") form = loads of wood / mdf.

/sreten.

[PeteMcK]

Sreten,
How would you characterise the differences between Winisd & Unibox? I have both but usually use Winisd because I'm too impatient to wait for Excel to start up on my clunky computer. (and it's a bit easier to compare multiple sims)
IIRC, in the past I got similar results trying the same thing on both.
Cheers,
Pete McK

[Loboone]

Hi Sreten and Pete McK,

Sreten I have taken on board what you have said and tried the set up with Uinbox. It works great and a lot more detail also.

I came up again though with 4 x drivers in 70 to 75 litres. Box size doen't worry me honestly. (The wife well we will see)

Hopefully I will be able to attach these files and pictures so you all can see and guide me through the issues.

Firstly the vented box of 75 liters looks good but I also like the passive radiator as well.

I am not sure if the PR is for just one driver or not and if it would work by placing it on the back of the cabinet radiating toward the walls.

In both cases I seem to be strugling with cone excursion. It appears that I can limit it with damping. Any idea's?

I am trying to sort out this drawing thing on the PC so I can post an image etc Probably going to go through a big learning curve though so may take some time.

[Loboone]

Cone excursion.

[Loboone]

Port Air speed

[Loboone]

Try again.

[Loboone]

Speaker impeadance.

[Loboone]

Step response.

[breez]

Port speed looks too high, it will almost certainly compress at those spl. How does it look like at 3-6 dB lower levels?