Zaph's L18 - lower XO point

[Mor den Siur]

Hello

Maybe there is someone who tried doing this ( Zaph? )
There is some projects that cutting 27tbfc/g below 1,5kHz. I've just built Zaph's design:
http://diyaudio.pl/viewtopic.php?t=12314 and I'm very happy with it, but I want to try it.

I'm going also to conwert it into 3-way design with L26rfx/p like in:
Calling Johan - Seas L26 + L18/L15 + 27TBFCG

I don't think that smaller power handling coused by lower XO piotn will be a problem to me because I don't like to listen music very loud. Some
I've read somwhere that 27tbfc/g will handle even 200 watt on 1,5 kHz

I will be gratelfull for any help

[sdclc126]

I believe the XO point on Zaph's BAMTM is 1450 Hz, which the 27TBFC/G handles very well.

[Dave Bullet]

Hi Mon den Siur,

Maybe there is someone who tried doing this ( Zaph? )

Zaph did a modification to the L18 design which I have a copy of for a customer that wanted to use the L18 TM design on its side as a centre channel. I won't post it here since it is Zaph's design and he specifically didin't want it shared around. He might chime in if you are lucky.

The original L18 design had the primary vertical lobe favouring listening at or above tweeter axis. When you lay a TM on its side, those to the woofer side would experience a dip around the crossover frequency. So Zaph changed the crossover to reduce BSC, lower the xo point (to about 1800Hz from memory - not as much as you are mentioning) and lower the listening axis.

Essentially - that design might be able to be used as a basis if you added a L26 (since it has less BSC) and were happy to have the tweeter above your listening axis.

For the link you've posted, I've updated it and posted on htguide.com. I still haven't constructed a test box for real measurements, but I have a couple of crossover variations based on the simulated data I have been working with.

I don't think that smaller power handling coused by lower XO piotn will be a problem to me because I don't like to listen music very loud. Some

The 1500 XO point with LR4 acoustic slopes means the 27TBFC/G will reach 0.48mm excursion (its xmax is 0.5mm) with around 40 watts of power input, producing 100.5dB at 1500Hz. Of course with an LR4 slope, the system is outputting 106.5dB. No dome tweeter will handle 200 watts directly at 1500Hz. It was Jay Kim who did the analysis around system power input of around 200 watts (refer blog).

norcad has also posted a paper based seas 3 way design over at htguide.com you could take a look at.

Cheers,
David.

[Mor den Siur]

OK, it will be a good decision to not changing Zaph's design, especially when it will run as 3-way.

So what about adding L26 filter to L18 design? The sensivity is similar, and want also cross it quite low.
Have you any ideas for filter for L18?

[sreten]

Originally posted by Mor den Siur


..... because I don't like to listen music very loud ....

I will be gratelfull for any help

Hi,

So what is the point of adding the L26 ?

/sreten.

http://www.rjbaudio.com/AlpheusMkII/alpheusmkii.html
(mid volume is too large IMO, I'd triangulate its compartment)

[Mor den Siur]

I also thought about L22rn4x/p. I came into a point that L26 have more to say in low frequencies that L22, but the cabinet volume is so big that I'm still thinking about it.

Here is L22rn4x/p crossed very low http://www.audioweb.cz/vase-shelbynator1.htm

I've got crossover parts for Dadalus - they are similar like in Alpheus. That could make the final cost lower...

[sreten]

Hi, not much wrong with the Daedulus design, /sreten.

[peter_m]

Have you considered just adding a sub-woofer instead of modding the x-over into a 3-way?

[Mor den Siur]

I am not a fan of 2.1 systems. I was considering 2 actice subs, but the cost will be to high.
The thing is coming to 2,5 way with L22rn4x/p.

[Dave Bullet]

The L26 is quite happy in a 47L sealed box which isn't too big. It's sensitivity is a better match with the L18 than the L224RNX/P. The L22 Qes hints at a vented alignment being more suitable. This will increase the volume you need (which I haven't modeled so could be wrong), putting it on a par (or above) the sealed L26. The other downside is the cost of the prestige drivers. The L26 was $165 at Madisound last time I looked.

A true TMM 2.5 way usually matches drivers in the MM. A popular 2.5 way topology seems to be the Bagby (?) cascaded design, which really requires the same drivers for the MM so the 0.5 woofer circuit just requires a follower inductor.

Adding any driver to the L18 TM system will require a woofer/mid crossover design. Since you will need less BSC on the L18, you will probably need to shape / raise the mid/tweeter crossover point as you may gain 2+dB in overall sensitivity over the TM version.

So essentially - you must be prepared for a crossover redesign in adding any one of these drivers.

Anything less than 240Hz if you are going 3 way passive will require large and costly inductors.

If you are just after more bass, another option is to add just another L18 and go with a TMM 2.5 way as you hinted. Zaph did a design a while back (I think it was a TMM 2.5 way - not an MTM) but never built, voiced etc... so comes with cavaets.

Cheers,
David.