DIY-project: JBL Kebnekaise S4365

[bubbleboy76]

Sorry,your response to the above quoted comment regarding spikes from Greg Timbers is to put your speakers on wheels. Ok good luck with that.

I did not mean it that way. The wheels are not for solving the GT issue.

I want them on wheels so I can try, for example, having the woofer 1m out from the corner (to avoid corner-SBIR around 200-300Hz), and the horn on the wall, with correct dsp delay making them play togheter. And other placement strategies.

[BMWCCA]

I have my 4345 on casters with no apparent ill effects.

[bubbleboy76]

I played around in the free speaker designer software Basta!
http://www.tolvan.com/index.php?page=/basta/basta.php

First the JBL 1501fe woofer data entered (hopefully in the correct manner).

[bubbleboy76]

Basta! suggested the following box (with Keele algorithm) for 1501fe:

Vb=53,27L
Fp=44,79Hz

I assume Fp is the bassreflexport tuning frequency.

I wonder if this correlates to the interpolation Ruediger suggested?

[bubbleboy76]

Calculated system response for vented box (using the above suggested box) vs closed box (using the same box-size) with linkwitz-transform.

Graph shows calculated response for 1m 2,83 volt.

(no room gain, or baffle step, included)

Qb used for closed box=5 (much damping)
Qb used for vented box= 20 (moderate damping)

Closed box looks really nice too me, what I am missing!? 93dB sensitivity down to 20Hz.
There are 6dB more bass about 50-150Hz for vented, but I get smoother and deeper curve with closed. And the room gain will add a lot to this. Assuming I can add something like linkwitz-transform with my dbx4820.

With the assumption of having subwoofers to crossover to downwards, would you recommend me to do closed or vented box for the woofer? (I know you are going to say vented...)

[bubbleboy76]

Closed box comparison with and without linkwitz-transform.

[bubbleboy76]

Adding this kind of linkwitz-transform-DSP, would it be any problem technically? Maybe pos can comment that?
There are quite some gain to add, is it too much to do with digital dsp, you think?

[Adhoc]

I will try soft feet decoupling the speaker low frequencies from the floor, in the end, when I know the exact weight-distribution of the speaker.

The only problem with that approach is maybe this:

Originally Posted by gtimbers
You will eat the bass kick immediately if any enclosure movement is allowed. The woofer kicks really hard and if any energy is consumed moving (rocking) the enclosure due to it not being properly coupled to the floor, you will lose bass kick and impact. The proper use and need for spikes (or equivalent) is not BS. It is based in sound theory and is easily demonstrable.

I will start with them on casters, I think.

Timbers is correct when he says you should prevent the speaker from rocking back and forth. Using (common) spikes is not a good way though as you don't want the speaker coupled to the floor. You should avoid any vibrations from the speaker transmitted to the floor or room structure, giving off resonances. That means a decoupled speaker (isolated with springs or compressed rubber feet => a wobbly speaker if free standing) while at the same time immovable and fixed in its position. Both together can be tricky to accomplish but can be solved. A post on positive things about decoupling speakers: https://www.gearslutz.com/board/11882181-post22.html (That whole thread is good reading.)

[pos]

A post on positive things about decoupling speakers: https://www.gearslutz.com/board/11882181-post22.html (That whole thread is good reading.)

The important part in the linked post is the "very heavy slab base, many times the weight of the speakers (ours is 960kg)". This prevents most of the rocking.

[hpham]

Question: where to buy all the JBL drivers?

[bubbleboy76]

Question: where to buy all the JBL drivers?

That is the million dollar question.

I bought mine second-hand from a member on this forum.

[JeffW]

That is the million dollar question.

I bought mine second-hand from a member on this forum.

.

That's good to hear, I just saw your WTB ad in the marketplace and was wondering if you had done all this preparation without having secured the drivers yet.

[bubbleboy76]

2 more woofers would spicen up the mix a bit

[hpham]

That is the million dollar question.

I bought mine second-hand from a member on this forum.

Because I can't find the shop or distributor to sale modern driver of your nice project. I asked because I want to built one and really don't know where to buy.

[bubbleboy76]

Because I can't find the shop or distributor to sale modern driver of your nice project. I asked because I want to built one and really don't know where to buy.

These luxury drivers are not for sale. You can not buy them from JBL.