4 Way Build

[David Ketley]

I'm using Jbl 2245s 2123s 2446s (shortly to be replaced by 2450s, lighter) 2405s in a 4 way active set up.

I'm using a Marchand xm 44 3 way crossover with just a Capacitor to the Jbl 2405s.

The crossover frequencies are 160Hz 1600Hz and 8000Hz.

I was worrying about the fall off of the Jbl 2123 at the lower end 160Hz and sure just running the unit on its own it drops off but putting the JBL 2245 into circuit cleans up the lower response no end in fact I'm quite happy with the result.

I'm using 24db Linkwitz-Riley cards and its fascinating just how much information still gets through each side of the crossover point. The JBL 2123 cross at 1600Hz but they are still audible at double the frequency! This blend works very well at lower frequencies but I'm not happy even though I'm crossing the JBL 2446 high at 1600Hz that the amount of lower frequency information getting through is not insignificant. I'm thinking of sending off for the 90 Db cards for the crossover to the Jbl 2446 Marchand can supply.

I would value any comments or suggestions.

[yggdrasil]

Do you consider 90dB slopes to protect your 2446's?

If so - I'm quite sure they will handle more than the listener.

Sound-wise - I believe more complexity will give you less details / nuances.

[David Ketley]

Its not the protection but the fact that horns and compression drivers need to be kept within tight boundaries to perform well.

I thoroughly agree with your observation on complexity but the Marchand active crossover is easily adaptable and a 90db crossover is available.

Another issue I,m having is with the 2245s they are sounding woolly so some mental gymnastics sorting them out!

[richluvsound]

Are you using 4313b's crossover FQ's as a starting point ? Try running the 2245 higher up to 290 hrtz ?

Richard

[David Ketley]

Are you using 4313b's crossover FQ's as a starting point ? Try running the 2245 higher up to 290 hrtz ?

Richard
Rich its really good to hear from you.Tried that already I have cards for 260hz but I did not like what I heard. So far I have no stuffing in my boxes which are a bit of an unconventional design, my guess is I'm getting some reflections off the rear of the cabinet and my listening room is adding its character to the sound. Firstly I,m trying to solve the internal back wall reflection of the 2245s boxes, I thought of using AFP100 Pro-Acoustic Pyramid Foam Pyramid Tiles but a not sure they will attenuate at the lower freq 160hz down. Any suggestions would be welcome.
Im very happy with the blend from the 2245s to the 2123 with them both in circuit there is not much loss if any at crossover up.
When funds allow I intend purchasing the Iwata 300 horns but even then I will keep away from trying to get them low. They will be a far better match rather than the 18 Sound XT1464 1.4" throat horn taken out to 2". In spite of some negative comments its the best sounding horn I've heard on my system 1600hz-8000hz

Dave

[richluvsound]

Rich its really good to hear from you.Tried that already I have cards for 260hz but I did not like what I heard. So far I have no stuffing in my boxes which are a bit of an unconventional design, my guess is I'm getting some reflections off the rear of the cabinet and my listening room is adding its character to the sound. Firstly I,m trying to solve the internal back wall reflection of the 2245s boxes, I thought of using AFP100 Pro-Acoustic Pyramid Foam Pyramid Tiles but a not sure they will attenuate at the lower freq 160hz down. Any suggestions would be welcome.
Im very happy with the blend from the 2245s to the 2123 with them both in circuit there is not much loss if any at crossover up.
When funds allow I intend purchasing the Iwata 300 horns but even then I will keep away from trying to get them low. They will be a far better match rather than the 18 Sound XT1464 1.4" throat horn taken out to 2". In spite of some negative comments its the best sounding horn I've heard on my system 1600hz-8000hz

Dave


Size of box , bracing layout and material of construction ? port size ?

Rich

[David Ketley]

Size of box , bracing layout and material of construction ? port size ?

Rich
285 liters with two 6" ports only 250cm long. This brings it in at just over 32Hz, owing to room size could not see any point in going much lower.

Listening room total size 28 feet x 20 feet x 16 feet high into the apex. but with a wall at 18" with an opening of 120 square feet total.

The room has stone walls but it is a suspended floor! The roof has around 40 tons of stone flags on so is inert.


The box is lying down so is only 22" high but is on two 4"x 4" solid oak stands.

I will try moving things around the room a bit but I'm just trying putting a triangle of absorbent board behind the 2245s to see if that improves reflections.
This is the problem with bass reflex its a tuned system very dependent on many parameters. Must try a different power amp as well to see if that makes a difference.

I must see if I can post some pictures that would make things much clearer.

Dave

[yggdrasil]

I have run 2245's in bass reflex earlier. Had to move them ~1m out from the wall, and at least 10cm up from the floor.

Getting them right demanded a lot of measurements and moving around. The curves changed from saw-tooth to a straight line and was well worth the effort.

[David Ketley]

I have run 2245's in bass reflex earlier. Had to move them ~1m out from the wall, and at least 10cm up from the floor.

Getting them right demanded a lot of measurements and moving around. The curves changed from saw-tooth to a straight line and was well worth the effort.

Yes was getting mine mobile today, I also moved a table adjacent to the left hand speaker and the woolly response disappeared.
I must admit I don't have any measuring kit other than a DB meter, a tone generator and my ears.

[yggdrasil]

I have a Behringer ECM8000, but today I would probably get a USB microphone like e.g. http://www.amazon.co.uk/miniDSP-UMIK-1-Measurement-Calibrated-Microphone/dp/B00N4Q25R8/ref=sr_1_1?ie=UTF8&qid=1430374978&sr=8-1&keywords=measurement+microphone+usb

[David Ketley]

Well after moving furniture away from the speakers location and moving them away from the back wall a bit I stuffed the boxes with wool and wow what a difference, tight articulate bass. No wonder these 2245s are so highly rated. I will play with the port length for final tuning but all other issues are solved.