SLOB project

[Ali Tait]

I find a single 18 better than twin 15’s.

[ed]

That's an interesting observation Ali.

There is a historic argument among bass players that 2 x 10 is better than 15 and 2 x 12 is better than 18. I've never seen twin 15 against an 18 discussed though, but I'm not sure the preference works in HiFi situations.

[Ali Tait]

Well I like the bass better with the Bastanis with single 18” Goldwood driver than with my previous OB’s with twin 15 Eminence Alpha. Maybe it’s just a better driver.

[steve s]

I started off with the belief that 2 smaller would be better than a big one..
My own thoughts are now that all high efficiency drivers have a peak dependant on size. Putting two together does nothing but increase that, although the resonant frequency is smoothed, that does not help the low frequency.
When I bought my 4 x 18s a few years I nearly bought a pair of 24" I often regret not doing that now.

My goal has been not to loose efficiency as best I can.. so I'm not prepared to use low eff bass drivers for a a couple of good reasons.

[Dave the bass]

That's an interesting observation Ali.

There is a historic argument among bass players that 2 x 10 is better than 15 and 2 x 12 is better than 18.

Typing as a bassist (using two hands and without dribbling too I might add etc etc etc etc) I personally prefer 2 x 10's over 1 x 15. I've used 1 x 15, and 2 x 12 and also at one time 1 x 15 + 1 x 10 + 2 x 6" and HF horn in the same cabs x 2. Huge, heavy, spensiff.

The 2 x 10 on its own is for me 'the best batch yet' IMO/E mainly because of the speed and attack they have when you're playing on a stage, efficient at LF's they're not but modern day amplification/gain is cheaper (and lighter!) now plus seeing as I don't play in a live dub band I don't need that mahoosive low-end force and power on stage, let the FOH PA cope with that, thats what its designed for innits.

Horses for courses.

But, in HiFi OB's, all the types I prefer seem to be loaded with a big whopping single 15 or 18 driver.

[IslandPink]

'the best batch yet'

You couldn't resist, could you ?

Ray, the Freq response of the 10" drivers is a bit too good to believe - have you seen anyone eg. on DIY Audio who has done an independent measurement yet ?

[Toppsy]

Ray, the Freq response of the 10" drivers is a bit too good to believe - have you seen anyone eg. on DIY Audio who has done an independent measurement yet ?

Seems you and I Mark are on the same wave length. I have asked just this question to Scott, he is quite clued up on this sort of manufacturer published data and what (if any) tweaks they adapt to the figures or plots.

Ray, I'm watching this with interest. However it would be interesting if you could publish the costs you incur in this build as both the drivers you are using are quite expensive units, then there is the added cost of the XO filter module (Nelson Pass unit?) together with the bi-amping requirements. Those Eminence sub-bass drivers are around £380 each from the only UK seller I could find. Though lii Audio in China have reduced the cost of the Fast-10 if they declare the true selling price of the drivers for customs purposes there will be a hefty import duty + VAT payment to be added to the original buying price. This could make the O/A cost at least double that of the of my own OB experiments.

Having said that though I do like the looks of the finished speakers and agree for OB's they are more domestically acceptable than most. Might ask Scott how this design would work with the Monacor 10" coax I used on my own OB's coupled with a single 15" bass unit that I used. But doing it all passively as 3-way using a single amp. If this goes ahead I will start a parallel thread.

[IslandPink]

This could make the O/A cost at least double that of the of my own OB experiments.

Yes, but the Lii units are a third of the price of some Cube 'Magus', and about 1/6th of some AER's, so I'm still interested, as they are a very good replacement for what I'm using on OB currently without the penalty on sensitivity with the twin FX120's.
They have more or less all the parameters that I like, I would just like to see a real measurement of the 500 to 5000Hz region to compare against what I have, or other FR units.

[Ray P]

Lots of opinions and its good to see that the project has generated some interesting and lively discussion - it often seems quite quiet here so that's great.

But, as I've said earlier, I'm going to play it safe and go with the Nelson Pass script for the bass configuration; he's probably one of the most experienced of SLOB experimenters and the bass of these units has been positively commented on in several instances. My assumption is that slot loading places different demands on a bass unit to simple baffle mounting so it makes sense to utilise the body of knowledge that Nelson Pass has accrued. The Eminence Definimax units are available from Blue Aran for about £235 each (delivered).

I've lots of experience of buying from Chinese sellers and know what to look out for and have asked questions. The price I have paid for the Fast-10S units includes VAT and delivery within the EU so the price is competitive. Although I'm obviously interested in the freq. response graph it is obviously smoothed and doesn't tell the full story, but, I didn't decide to purchase the units based on it, rather I've decided to take the risk based on the positive comments about the sound quality of the units posted by several DIY'ers who have used them in real speakers, both boxes and OBs (and they feature in several DecWare OBs as I linked to somewhere above).

Over the festive period, when I can't work on the amp builds, I'll get some AutoCAD drawings put together for the base unit cradle with a view to getting the parts CNC machined from birch ply. Not the cheapest option but accurate! I'm certain I can get two sets of cradle parts from a single 8 x 4 sheet with ply to spare - possibly, with some careful nesting, maybe even enough for two baffle boards too - I've not had sheet material machined for a few years so will have to check out the previous place that did it for me but I also know there's a Maker facility at Cardiff that has a large bed CNC facility.

I did wonder about the Monacor units so it'll be interesting to see how a version using them would work out.

[Toppsy]

Mark wrote:

Yes, but the Lii units are a third of the price of some Cube 'Magus', and about 1/6th of some AER's, so I'm still interested, as they are a very good replacement for what I'm using on OB currently without the penalty on sensitivity with the twin FX120's.

Fully understand your interest Mark. Never have been a fan of Fostex drivers though the FX120 units are probably the best driver they produced. However for me there is something about Full Range drivers that I find limits ones listening music. There non ability to handle certain types of music such as the likes of rock music so one tends to tailor the type of music these drivers excel at i.e. simple girl and guitar genre. Hence my view to use the Monacor 10" coax unit that I know can handle all genres of music with aplomb.

Ray, Fully understand from where you are coming and it would seem you have done extensive research before embarking down this round. I expect this project to pan out well. But for myself based on my past experience building and using several full range driver speakers and knowing their limits I still wouldn't use a FR for the lower mids and HF for the reasons I have said. But that is just me.

[vinylnvalves]

The Beyma 12BR70 is a very good bass driver with a foam surround, also nice and cheap. There are a number of OB designs around using 4 to 6 drivers per side. The Orelino by Bert is an example which uses a “modified” Beyma driver in a similar arrangement to SLOB.

[Nick]

However for me there is something about Full Range drivers that I find limits ones listening music.

Of course just because a driver is marked as full range doesn't meant you have to use it in that way.

[Ray P]

Yes, but the Lii units are a third of the price of some Cube 'Magus', and about 1/6th of some AER's, so I'm still interested...

Mark, remember that these specific units (Fast-10S) are on 'end-of-line' sale and after that you would need to purchase the more expensive Crystal-10 units. The Lii website states the stock level of the Fast-10S as 2 (pairs).

[IslandPink]

My calcs were based on the Crystal 10, actually !

[Ray P]

My calcs were based on the Crystal 10, actually !

OK.

I would offer to measure the response of the 10S units when they arrive but I haven't got the means. I'll need to beg, steal or borrow a MiniDSP that means I could measure but only in room so not ideal as it would have to be 'processed'.