[Danny Richie]

Attention Alpha LS owners...

I have recently been doing some tweaking on the Alpha LS and have achieved two things.

One, a revised network.

Secondly, a bass management system.

First, a little on the revised network.

The tweeters have now been allowed to extend just a little bit lower crossing over to the woofers at 1,200Hz instead of 1,375Hz.

Secondly, the woofers received a steeper roll off that has them nearly gone by 2kHz and about 14db down by 1,500Hz.

This also smoothed out the response as it was slightly elevated (1db or more) in the crossover region.

The impedance of the overall speaker is now more even across the board too. It has less rise in the area before the network and there is less shift in phase now too.

What did it do to the over all sound?

Smoother by a little for sure. Vocals seamed to be a little deeper in the sound stage than they were before. Placement of images are a little more pin point and have a little more air around them. Detail level in the upper vocal range is better too.

Next was the bass manage issue.

When these were shot in our anechoic chamber they were dead flat across the bottom end with no rise in the lower octaves.

When these were shot with a single speaker standing in the center of my den (a room that is 23' by 17' with 9' ceilings) it also had little gain in the bottom end (room gain). This was with ungated Pink noise.

But when placed 5' out from the rear wall and positioned where it is placed when playing a pair (more towards the corners of the room) I do get room gain in an area below 200Hz, and with a little gain at 250Hz.

I also have noticed that at Dodd Audio, Gary gets considerable room gain in his much smaller room using the Alphas. Plus, so far most of the Alpha LS owners are using these in rooms no larger than mine. So they are likely dealing with some room gain in the bottom end too.

So it is likely that most are getting excessive room gain in the bottom end as the Alpha LS can easily load the room with low frequency reinforcement. They are -3db down at 25Hz in my room too.

Since the output of the Alpha LS is limited to the output level of the tweeters it is not possible to raise the output level in any other areas.

The solution would have to be to limit the low frequency output in the bottom end and to do so without effecting the rest of the response.

So I came up with something that works and is adjustable.

It uses a large inductor in parallel across the positive and negative terminals after the main network with an in line resistor.

In this application the resistor values need to have a pretty high rating. 30 to 40 watt rating is just enough for most applications.

So bundles of the Mills resistors are used with 100 ohm and or 82 ohm values.

This allows one to adjust the low frequency output to either no adjustment, 33 ohms, 25 ohms, 20.5 ohms, or 16.4 ohms of resistance.

This does not adversely effect the impedance of the system either.

Even with the use of the 16.4 ohm values in place the low frequency load does not drop down below 8 ohms.

The result is tunable bottom end.

This seamed to clean up the lower midrange too.

The sound of the system in my room just got better by a notch or two.

I have some more measuring to do and I will post all the new measurements and the cost of the bass management system soon.    

[azryan]

"-The tweeters have now been allowed to extend just a little bit lower crossing over to the woofers at 1,200Hz instead of 1,375Hz.-"

But I thought the previous x-over point was 1,275 Hz?

"-I also have noticed that at Dodd Audio, Gary gets considerable room gain in his much smaller room using the Alphas. Plus, so far most of the Alpha LS owners are using these in rooms no larger than mine. So they are likely dealing with some room gain in the bottom end too.

So it is likely that most are getting excessive room gain in the bottom end as the Alpha LS can easily load the room with low frequency reinforcement. They are -3db down at 25Hz in my room too. -"

My room's ~the same size as yours and I don't hear any excessive bass. If anything it's a hair thin on the bottom end, but I believe that's due to my line level signal.
I've tried other line level signals are can drastically change the balance.

If my room is simialr to yours and your F3's ~25Hz. So is mine 'eh?

Is there are 'bump' between there and the 200-ish Hz you mentioned?

I doubt I'd want to gut my fairly brand new Alphas x-over just for a slight tweek in the x-over region.

I could see it being even better -since nothing's perfect, but I don't hear any probs. now.

Is there anything I can listen to that you know directly relates to that x-over region where you can hear a distinct diff.?
Music or certain DVD or something?

[Danny Richie]

Hi Ryan,

Your room, like mine has something else going for it. You have some good sized tube traps across the rear wall behind the speakers. This will reduce the low frequency reinforcement.

The bass management system does nothing but control the room gain in the bottom end.

Keep in mind that I have my speakers spread further out to the corners of the room too.

Some electronics can be on the weak side down there too. It is all a matter of synergy and system matching.

If you are happy with the current sound then don't mess with it.

The crossover change to the new version is a minor tweak not a major change. It pulls the output level down in the crossover region slightly giving it a more laid back, less forward sound stage.

Maybe you can make a trip to Texas for the 2003 DIY event and give my Alpha's a listen? It's a two day long event and well worth the trip if you have the time for it.

I know I have one guy coming from Boston and one from Seattle for this years event, so you won't be the guy that comes the furthest.

[azryan]

Sounds good about the new x-over.

I think I'm totally fine on the bottom end so I'll just keep them the way they are.

About TX DIY... I've thought about it. Part of me'd really like to go. Don't really have the time and spare money.

Or if we did have the money it'd be hard to spend it on a trip rather than say that dAck! you seem to really love.

I'll keep thinking about it...
 
My wife wouldn't mind going at all either. Cool 'ey?
Remember... she picked the Alphas as the best looking speakers when I showed her the few that I was considering.

I'd love to hear your system just 'cuz I know your room's similarish and we both have Alphas (though yours I'm sure are decked-out w/ speacial wire and the best connectors. And just a guess but maybe all matching woofers and neos?? no?) but I'm sure our line level signals are very different.

I guess if I weren't so totally happy w/ the Alphas from top to bottom then I'd be more inclined to hear 'other stuff'.

Just had my buddy over and he's heard the Alphas many times now and while my system's alwasy been better than his he's never actually said he 'wanted' anything I've got, but he wants to build the Alphas. He can't afford new anything right now though and is in a small apartment where I think he'd havea very hard time setting up the Alphas even close to optimally.

He doesn't hand out complinemts too often, but in the middle of listening some music recently he just busts out -"Damn... Those speakers REALLY sound good."

That was pretty cool, and the compliment should be passed on to 'the man'.

Just re-watched The Matrix last night and listened to it at what 'must' be called 'too loud'. hehe
Certainly louder than even a typical theater and those Alphas just have zero problems w/ it (and I use a phantom center so they're doing the work of three speakers).

I asked my wife if it was 'too loud' (after it was over -hehe) and she said 'yes' but what would normally hurt our ears sounded totally smooth and put a huge smile on our faces when everything goes nuts at the end.

~$2,500 for these speakers? That's just a steal. Thanks Danny.