audio-talk

Ray P wrote: ↑Fri Jan 24, 2020 12:17 pm I though these might be a good match for the Lii 10inchers
http://greatplainsaudio.com/wp-content/ ... -Sheet.pdf

Although those are probably a bit much (SPL) , they are well-regarded though - Lynn Olson / Gary Dahl used them. Good at low signal levels.
They are a bit low Q for standard OB loading, but might be fine with the slot-loaded thing.
Remember the Lii are not really 100dB/w or whatever they claim. They are about 95db/w in the midrange, just higher in places in the treble ( which is not necessarily helpful ! )

The Altec (GPA) bass drivers are good if loaded. I had a pair in an onken cabinet. You could obviously add a resistor in series to change the characteristics for OB What about the Lii Audio bass driver at 500 dollars a pair there quite cheap too? It has foam surrounds which I believe an advantage and a closer matching efficiency level. I heard some 15” JBL’s with foam surrounds - amazing amount of low level detail compared to a more conventional 15 PA style cloth surround one. I am keeping my eye out for a pair of Beyma 15BR100’s at the right price.

vinylnvalves wrote: ↑Sat Jan 25, 2020 2:01 pm 1. The Altec (GPA) bass drivers are good if loaded. I had a pair in an onken cabinet. You could obviously add a resistor in series to change the characteristics for OB
2.What about the Lii Audio bass driver at 500 dollars a pair there quite cheap too? It has foam surrounds which I believe an advantage and a closer matching efficiency level.
3. I heard some 15” JBL’s with foam surrounds - amazing amount of low level detail compared to a more conventional 15 PA style cloth surround one. 4. I am keeping my eye out for a pair of Beyma 15BR100’s at the right price.

1. Now I hadn't considered that, given the problems with running the Supravoxes with series resistance - but the primary resonance of the Altec's is so low that you could probably run them with 2 or 3 ohms of series resistance and they'd be fine - and ~95dB/w. Low Rms ( 1.49 ) too. Good point.
2. We discussed that about 3 or 4 posts back !
3. Are you sure it's the foam surrounds, or is the spider less stiff & lossy ? Could be either, but I've read more than once that the spider contributes more to Rms than the surround. Anyway, thanks for the info.
4. What's the appeal of those ? They don't appeal to me with Rms = 5.2. More of a PA high-SPL unit - may suit your taste though.

Dont look at the specs for the new Beyma’s it a different driver - same name. See https://www.diyaudio.com/forums/multi-w ... 5b100.html
Regarding your comment on the spiders - I have been thinking of butchering a PA driver in the name of science. There are a number of “top end drivers” which have effectively removed the spider. For home use where the cone excursion is minimal just removing it could be an option. The solution I like are the silk threads connected to centralise the cone, or the EPDM rubber spoked arrangements which do the same thing.
Looking at the lii bass drivers when you add to basket.... the cost almost doubles when you include postage

IslandPink wrote: ↑Sat Jan 25, 2020 4:02 pm3. Are you sure it's the foam surrounds, or is the spider less stiff & lossy ? Could be either, but I've read more than once that the spider contributes more to Rms than the surround.

It depends on the driver design as to what part of the suspension is doing more work. Take MA for instance. The Alpair 12P is in effect a single-suspension driver, where the spider handles almost all the work, and the surround's primary role is that of an air-seal. By contrast, the 11MS is also a single suspension unit, but in its case, it is spiderless and the surround provides all the mechanical damping; there is no rear suspension at all. Various related reasons from coil stability / centring under load & power-handling to excursion &c.

Toppsy wrote: ↑Mon Dec 30, 2019 7:26 pm

Oh, and there were no additional costs for VAT or import duty.

Hope this proves true for you Ray. However, in my own experience when I bought some ESL speaker kits from Australia I also thought I have paid all the duties and relevant taxes etc. at source and was not charged any addition Import Duties and VAT charges when the courier delivered the speakers to my door. So I thought, like you, I had got away with having to pay any additional UK taxes etc, That was until about 10 days after delivery I got an invoice in the post from the courier company for import tax, VAT and the courier charges for clearing by goods through customs. The import duty was based on the total cost of the goods plus the shipping charges and then the VAT was added on to this new total cost at the then current going rate. To say I was gutted was an understatement.

Well, a month has passed since I took delivery of the Lii drivers and no sign of any additional charges.

I've taken a bit of time out from audio projects - been going through one of those fallow spells that come along every now and then and I've now lost my way a bit so please give me a hand with getting some thinking organised.

I keep returning to wanting to build an open baffle project and would like to pick up the Pass SLOB that I started this thread about.

For the 'full range' driver I would like to use a pair of 15ohm Lowther PM6s as they could easily be driven by one of my flea-power OTL amps. Nelson Pass used PM6s, presumably 8ohm, in his original build.

Crossover will I think be around 180-200Hz

The recommended bass drivers are nominally 8ohm. I have a pair of 100W chip amps available for these.

I'm thinking passive filtering of the Lowther, or maybe roll-off the LF output of the amp as Mark suggested back along

For the bass unit I'm thinking something like the Pass Analogue crossover network, or maybe even a DSP unit, would allow management of the roll-off but also give options for a little bass lift if needed.

Am I being muddle-headed?

re the muddle headed, I don't think so Ray...
I still haven't got mine off the drawing board...so much to do, so little time....
I have 4 x tpa3116 boards which I was going to drive with 2 x LR actives...they are still in the box waiting to be nailed to pieces of wood.
Unfortunately my drivers are not quite as well-heeled as yours....as usual it's a budget undertaking.

Re the pm6a, I got the following info on the quote from them

Available in either 8 or 15 Ω. Please Note: If you require 15 Ω we would strongly recommend that you go for Silver Voice Coil as this is a far more reliable option.

Also, the curves look a lot better. Not heard them yet though.

Nick wrote: ↑Mon Nov 30, 2020 8:35 pm Re the pm6a, I got the following info on the quote from them

Available in either 8 or 15 Ω. Please Note: If you require 15 Ω we would strongly recommend that you go for Silver Voice Coil as this is a far more reliable option.

Also, the curves look a lot better. Not heard them yet though.

my turn to play pedant...
the quoted statement STRONGLY implies that if you don't opt for the silver voice coil then the product could be less than reliable..

just sayin!

I'd say go for it Ray, I currently have something similar and it's the best sound I've had at home.

I use the GM70 SET with the Fostex wideband drivers using only the mechanical roll off of the small baffle. Measurements suggest it falls off slowly below 250Hz. I roll the bass off in the amp at 100Hz to keep the bass frequencies out of the OPTs.

The Supravox 285 bass drivers I now use in sealed boxes as measurement showed they were rolling off quite high with little low bass in the baffles. I use cheap ebay class D 3116 subwoofer amps which have a low pass filter of 180Hz built in. They work surprisingly well in the application.

And I use another cheap 3116 amp with a first order filter set to around 7kHz with the supertweeters.

I guess it's all just choosing one's compromises. The additional complexity of multiamping is more than compensated, for me, by the clarity I gained removing the speaker crossover and coupling the amps directly to the drivers. Feels like the benefits of single drivers, but with the added benefit of deep controlled bass .

Thanks for the encouragement chaps.

Regarding the Lowthers, yes I would default to the silver version.

A question for Nick on his Lowthers for his Quasar build; did you consider PM5A units?

Regarding the crossover, I need to get a better understanding of tweaking the 'full-range' amplifier to roll off appropriately - any pointers?

Ray P wrote: ↑Tue Dec 01, 2020 7:34 pm
Regarding the crossover, I need to get a better understanding of tweaking the 'full-range' amplifier to roll off appropriately - any pointers?

Well, it's just about making sure the really low stuff doesn't make the full-range driver flap around I suppose. Depends on the rest of your system, though. Instead of just filtering the VLF, you could make the amp's input filter part of the overall crossover.

These days, I prefer to go with passive crossovers and a full-range amplifier - keeps overall operation nice and simple.

Chris

Ray P wrote: ↑Tue Dec 01, 2020 7:34 pm A question for Nick on his Lowthers for his Quasar build; did you consider PM5A units?

No either of the extra cost and the peaky response curve of the PM5A would have put me off.

Cheers Nick.